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Cotton textiles play a universal role in everyday life, but they are prone to stain and serve as a primary channel for transmitting viruses and bacteria. The photocatalytic/antibacterial coatings are highly effective in addressing bacterial contamination on fabrics, although their efficacy diminishes with continuous use and washing. Here, insights are provided into the attachment of LiNbO 3 on cotton surfaces using eco-friendly chemical activators to promote resistance to washing cycles, self-cleaning, and bactericide textiles. LiNbO 3 nanoparticles were synthesized by low-temperature hydrothermal synthesis and directly applied to cotton fabric using immersion. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) N 2 adsorption, diffuse reflectance for band gap determination, and Raman spectroscopy. A simple and effective impregnation method was used, promoting an ester-bond attachment between the cotton surface and the activators. Microscopy analysis (SEM) confirmed the successful deposition of the nanoparticles on cotton fabric. The LiNbO 3 coating consisted of transparent layers and did not change the properties of cotton. Methylene blue stains are generally eliminated under UV light after 2 h using nanoparticles and activators. Antibacterial properties were evaluated under visible light through direct contact with bacterial suspensions and culturing. The coated cotton fabric that was activated with oxalic acid exhibited significant photocatalytic antibacterial activity against both Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) bacteria, with bacterial reduction rate above 97 %, even after 10 washing cycles. This performance can be attributed to the effective coupling of LiNbO 3 with oxalic acid in the cotton's surface and its resistance to washing out. This study's novel synthesis and coating method offers an environmentally friendly, cost-effective, and straightforward approach for producing LiNbO 3 self-cleaning and antibacterial surface-activated cotton. [ABSTRACT FROM AUTHOR]

In the present research, it is reported that ball milling technique can be applied to enhance the photocatalytic properties of MnO and ZrO 2 metal oxide powders (MZOx) furthermore the fabricated photocatalyst can be used for the degradation of tetracycline (TTC). XRD analyses revealed that increasing the milling time resulted in the formation of a pure metallic Mn crystal phase, which boosted the antibiotic degradation rate. It was confirmed by SEM technique that the morphological structures of the particles were generally small and uniform. The band gap energy was calculated as 3.70 eV for the hybrid metal oxide. Additionally, the adsorptive and photoluminescence features were illuminated via DRS and PL analyses. The effect of milling time had a major impact on the photodegradation rate of TTC, and the 8 h milling sample (MZOx-8h) exhibited the highest catalytic degradation activity (79.4 %). Low photocatalytic activity was obtained at acidic pHs and increased at alkaline pHs. The presence of H 2 O 2 sharply decreased photocatalytic process time (60 min) and 94.3 % of the TTC was degraded at 7.5 mM H 2 O 2. The photocatalytic degradation process proceeded through superoxide radicals and was supported by holes. The stability of MZOx-8h almost remained constant (70.02 %) even after seven cycles. It was determined that the presence of oxalic acid positively affected the progress of TTC degradation reactions. Further, practical application areas were investigated and MZOx-8h doped on support materials was found to be suitable for such applications in proportion to the doping ratio. Finally, it was demonstrated that MZOx-8h exhibited remarkable performance in photocatalytic reactions of different types of organic pollutants. The synergistic nature of MnO and ZrO 2 with the contribution of ball milling time effect resulted in high photocatalytic activity. • High purity metallic Mn phase was successfully synthesized by ball-milling. • MZOx was used for the first time in TTC photodegradation. • TTC degradation was stable in the seventh cycle. • The different organic pollutants were removed with high efficiency. [ABSTRACT FROM AUTHOR]

Soybean molasses (SM), a sugar-rich by-product obtained from manufacturing soy protein concentrate, is an interesting source of fermentable sugars for biotechnological processes. For the first time, SM was used as a new and low-cost substrate in Aspergillus niger cultures to produce gluconic acid (GA), a carboxylic acid obtained by the oxidation of glucose and with a wide range of applications. The effect of SM composition and sugar content on GA batch production was studied in a stirred-tank bioreactor using two SM samples with different total sugar concentrations of 46 % and 52 % (w/w) and different sugar profiles. GA productivity improved as the total sugar concentration increased, whereas yield was unaffected. Agitation rate increase positively affected yield and productivity in SM medium with the highest sugar concentration. Under these conditions, the highest GA titer (79 g·L−1) was obtained. Oxalic acid and fructose syrup were other added-value compounds found from the submerged fermentation of SM. This work proved the potential of A. niger in the bioconversion of SM with different compositions into GA, providing a novel strategy for low-cost and eco-friendly GA production from SM. [Display omitted] • Soybean molasses is a new substrate for gluconic acid production by A. niger. • The sugar profile of soybean molasses affects organic acids production • Rise of agitation rate had positive effect on gluconic acid yield and productivity. • The highest titer (79 g·L−1) was obtained at 600 rpm and high sugar concentration. • Oxalic acid and high-fructose syrup were also produced from soybean molasses. [ABSTRACT FROM AUTHOR]

Fusarium verticillioides is both an endophyte and pathogen of maize. During growth on maize, the fungus often synthesizes the mycotoxins fumonisins, which have been linked to a variety of diseases, including cancer in some animals. How F. verticillioides responds to other fungi, such as Fusarium proliferatum , Aspergillus flavus , Aspergillus niger , and Penicillium oxalicum , that coinfect maize, has potential to impact mycotoxin synthesis and disease. We hypothesize that low molecular weight acids produced by these fungi play a role in communication between the fungi in planta/nature. To address this hypothesis, we exposed 48-h maize kernel cultures of F. verticillioides to oxalic acid, citric acid, fusaric acid, or kojic acid and then compared transcriptomes after 30 min and 6 h. Transcription of some genes were affected by multiple chemicals and others were affected by only one chemical. The most significant positive response was observed after exposure to fusaric acid which resulted in >2-fold upregulation of 225 genes, including genes involved in fusaric acid synthesis. Exposure of cultures to the other three chemicals increased expression of only 3–15 genes. The predicted function and frequent co-localization of three sets of genes support a role in protecting the fungus from the chemical or a role in catabolism. These unique transcriptional responses support our hypothesis that these chemicals can act as signaling molecules. Studies with gene deletion mutants will further indicate if the initial transcriptional response to the chemicals benefit F. verticillioides. • Low-molecular-weight fungal acids impact the Fusarium verticillioides transcriptome. • Fusaric acid impacted more genes than other acids. • Kojic acid impacted two gene clusters that occur widely in Fusarium. [ABSTRACT FROM AUTHOR]

The present work demonstrates a low-cost, single-step route for synthesizing ZnO, CuO, and ZnO–CuO nanomaterials using oxalic acid as a precipitating agent, avoiding using other surfactants. The current research also demonstrates the chemical reduction method for incorporating Ag nanoparticles onto the surface of the synthesized metal oxide nanostructures using sodium borohydride as the reductant. X-ray diffraction studies reveal the phase purity and crystallinity of the nanoparticles, while X-ray Photoelectron Spectroscopy characterizes the chemical states of surface elements. UV–vis spectra of the samples disclose the modifications shaped by Ag nanoparticles in the absorption characteristics and energy band gap of ZnO, CuO, and ZnO–CuO nanomaterials. The catalytic potentials of the synthesized materials are tested by monitoring degradation reactions of hazardous organic pollutants, including methylene blue and methyl orange, within a few minutes. The significant finding of the present study emphasizes the incorporation of Ag nanoparticles to ZnO–CuO nanocomposite and the use of sodium borohydride in photocatalysis effectively to enhance the rates of degradation of pollutant dyes without the use of intense radiation or unique lamps by initiating a three-stage electron transfer mechanism. [ABSTRACT FROM AUTHOR]

The graphene oxide (GO) membrane treated by ozone, GOL, exhibits a relatively high conductivity, but its mechanical strength cannot be maintained due to severe swelling. To further improve the conductivity while suppressing the swelling, the free-standing GO membrane was subjected to ozone treatment and subsequently modified by crosslinking agents with oxygen functional groups, i.e., glyoxal (GLX) and oxalic acid (OXA). The modified membranes, GLX/GOL and OXA/GOL, successfully reduced the swelling and increased the conductivity to provide an excellent power output of a fuel cell at 30 °C due to the increased oxygen functional groups and the carbon defects. Furthermore, OXA/GOL exhibited a significant stability at elevated temperatures. At 50 °C, the through-plane conductivity and power output increased to 23.5 mS cm−1 and 317 mW cm−2, respectively. This is considered to be due to the relatively high thermal stability of the carboxy group added by the OXA modification. [Display omitted] • The agents with oxygen functional groups were used to crosslink GO layers. • The modified GO membranes showed improved conductivity and reduced swelling. • OXA/GOL exhibited the highest conductivities among the modified GO membranes. • OXA/GOL demonstrated a stable performance at higher temperatures. • A power density of 317 mW cm−2 at 50 °C was achieved by OXA/GOL. [ABSTRACT FROM AUTHOR]

[Display omitted] • Short-chain organic acids are readily biodegradable to CO 2 and H 2 O. • Selective leaching of Mo/V and Ni from HDS catalysts with organic acids is achieved. • The leaching of metals is jointly influenced by acidolysis and complexolysis. • Roasting pre-treatment is applied to maximize extraction efficiency. • Different leaching processes of Mo and V in HDS catalysts were identified. This article employs six organic acids to selectively dissolve Mo, Ni and V from spent catalysts, and the most effective acid is identified. Then, the effects of key leaching parameters, including acid concentration, temperature, and S/L ratio, on metal leaching are systematically explored to determine the leaching mechanism. The results demonstrate that the leaching ability of organic acids followed the order: oxalic acid > citric acid > tartaric acid > malonic acid > acetic acid > formic acid. The leaching process of metals was jointly influenced by acidolysis and complexolysis. Among them, more than 93.07 % of Mo, 86.64 % of V, and 74.21 % of Ni were selectively leached with oxalic acid at the optimum condition: S/l: 1/20, oxalic acid: 1.0 mol/L, temp: 60 °C. From the correlation coefficients, the resulting activation energies, and n values, it was demonstrated that Mo and V followed the Avrami dissolution reaction model, V leaching was controlled by the diffusion mode, and Mo leaching was controlled by a mixed mode of chemical reaction and diffusion. The dissolution behavior of both metals consistently adhered to the linear trend of the Avrami kinetic model under varying S/L ratios and oxalic acid concentrations. [ABSTRACT FROM AUTHOR]

• Nanosilicon was synthesized and characterized for size, shape, stability and functional group analysis. • Metabolomics elucidated differential metabolites of PEG-induced water stress and nanosilicon-treated leaves. • Volcano plot demonstrated differential metabolites recognized significantly in tolerant vs. susceptible group. • Enrichment analysis explains drought-responsive metabolites and novel pathways inclined by nanosilicon. Chickpea (Cicer arietinum L.) is a crucial agricultural crop, facing challenges in yield due to environmental stresses, particularly drought. The potential of nanosilicon (NS) in improving drought tolerance in crops remains unclear. This study efforts on synthesizing and characterizing silicon nanoparticles using sodium silicate, examining properties such as size, shape, stability, and functional groups before assessing their potential biological effects. Two chickpea varieties, drought-tolerant (GJG-6) and drought-susceptible (GJG-3), were selected based on previous research exploring biochemical and physiological changes under polyethylene glycol (PEG)-induced osmotic stress. Gas chromatography and mass spectrometry were employed to elucidate the metabolomic profile of chickpea leaves under PEG-induced osmotic stress, with and without NS treatment, at 23 days after sowing. Heatmap analysis depicted the intensity gradient of identified metabolites induced by NS treatment under osmotic stress. Fold change and volcano plot analyses revealed significantly differential metabolites between tolerant (T) and susceptible (S) groups. Metabolites such as l -tryptophan, d -fucitol, beta- d -(+) talopyranose, alloxanic acid, and azelaic acid were significantly upregulated in the tolerant group (T/S). Remarkably, metabolites like oxalic acid, 5-methyluridine, l -histidine, lactic acid, l -asparagine, and mannonic acid exhibited higher fold changes in the NS-treated tolerant variety compared to the susceptible one under drought influence (T_PEGNS/S_PEGNS). NS-treated tolerant variety revealed vital drought-responsive metabolites like l -asparagine, behenic acid, alanine, stearic acid, and d -mannose. This study unveils novel metabolites responsive to drought stress and induced by NS treatments, emphasizing their roles in antioxidants and signal transduction pathways that mitigate the effects of drought in chickpea. [Display omitted] [ABSTRACT FROM AUTHOR]

The photolysis can separate the lithium and iron leached by oxalic acid and H 2 O 2 from spent lithium iron phosphate cathode. The process free the addition of precipitant and no hazardous waste is generated. [Display omitted] • Photolysis instead of additional precipitants for metal separation and recovery. • Rapid and selective leaching of active material elements from spent LFP cathode. • No wastewater or hazardous emissions generated from the process. Recovering valuable resources from spent cathodes while minimizing secondary waste generation is emerging as an important objective for the future recycling of spent lithium-ion batteries, including lithium iron phosphate (LFP) batteries. This study proposes the use of oxalic acid leaching followed by ferrioxalate photolysis to separate and recover cathode active material elements from spent LFP batteries. The cathode active material can be rapidly dissolved at room temperature using appropriate quantities of oxalic acid and hydrogen peroxide, as determined through thermodynamic calculations. The dissolved ferrioxalate complex ion (Fe(C 2 O 4) 3 3−) is selectively precipitated through subsequent photolysis at room temperature. Depending on the initial concentration, the decomposition ratio can exceed 95 % within 1–4 h. Molecular mechanism analysis reveals that the decomposition of the Fe(C 2 O 4) 3 3− complex ion into water-insoluble FeC 2 O 4 ·2H 2 O results in the precipitation of iron and the separation of metal elements. Lithium can be recovered as dihydrogen phosphates through filtration and water evaporation. No additional precipitant is needed and no other side products are generated during the process. Oxalic acid leaching followed by photolysis offers an environmentally friendly and efficient method for metal recovery from spent LFP cathodes. The photochemical process is a promising approach for reducing secondary waste generation in battery recycling. [ABSTRACT FROM AUTHOR]

Lithium hydride (LiH) is a promising material for the production of hydrogen via hydrolysis. However, the formation of lithium hydroxide (LiOH) during the hydrolysis process hinders contact between the remaining LiH and water, retarding the hydrolysis reaction and increasing the actual amount of water required. Through this study, it is demonstrated that an increase in the hydrogen ion concentration can improve the hydrolysis of LiH. When the hydrogen ion concentration reaches 1 mol L−1, the maximum hydrolysis rate is 232.6 mL min−1, and the H 2 generation yield reaches 2102.8 mL. Additionally, we investigated the effects of doping solid acids and strong acid–weak base salts on LiH hydrolysis. Experimental results indicate that the addition of solid acids led to a hydrogen generation behavior similar to that with acid solutions. In particular, after the addition of oxalic acid, the maximum hydrolysis rate attained was 362.0 mL min−1, and the H 2 generation yield reached 2108.3 mL. After the addition of dl -malic acid, citric acid and dl -tartaric acid, the maximum hydrolysis rate attained were 173.1, 170.0 and 255.8 mL min−1, respectively. Under alkaline conditions, the hydrolysis of strong acid–weak base salts was enhanced, and the released hydrogen ions consumed LiOH, thereby increasing the rate of LiH hydrolysis. After the addition of CuSO 4 , the maximum hydrolysis rate attained was 403.8 mL min−1, and the H 2 generation yield attaining 2036.0 mL. After the addition of AlCl 3 and FeCl 3 , the maximum hydrolysis rate attained were 212.5 and 221.3 mL min−1. Thus, an increase in the concentration of hydrogen ions and the addition of solid acids and strong acid–weak base salts are effective techniques for reducing the adverse effects of LiOH formation on LiH hydrolysis for hydrogen production. [Display omitted] • Methods to mitigate the impact of LiOH on LiH hydrolysis are researched. • The addition of solid acids and strong acid-weak base salts enhance the hydrolysis rate of LiH. • The addition of CuSO 4 resulted in the maximum hydrolysis rate reaching 403.8 mL min−1. [ABSTRACT FROM AUTHOR]

• High iron recovery efficiency. • Low recovery cost. • The performance of regenerated LFP battery is better. The recovery of valuable metals from used lithium batteries is essential from an environmental and resource management standpoint. However, the most widely used acid leaching method causes significant ecological harm. Here, we proposed a method of recovering Li and Fe selectively from used lithium iron phosphate batteries by using low-concentration organic acid and completing the closed-loop regeneration. Low-concentration oxalic acid is used to carry out PO 4 3− , which is significantly less soluble in aqueous solution than Li, two-stage selective leaching Li, where the leaching rate of Li reaches 99 %, and the leaching rate of Fe is only 2.4 %. The leach solution is then decontaminated. The solubility of Li 3 PO 4 in aqueous solution is much smaller than that of Li 2 C 2 O 4 , which was required to recover Li to change the pH and Li can be recovered as Li 3 PO 4 ; Fe can be retrieved as FeC 2 O 4 ·2H 2 O, and re-prepared into lithium iron phosphate. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mixed culture was designed by mimicking natural habitats and bacterial stress. • The bacterial-fungal mixed culture produced 7460 mg/l oxalic acid successfully. • Bioleaching of spent printed circuit boards by mixed culture was better than pure. • The process concluded with a valuable residue that can be utilized in the future. This study explores the extraction of metals from spent mobile phone printed circuit boards (SMPhPCBs) to address environmental and resource depletion concerns. The challenges in metal recovery from SMPhPCBs arise due to their complex composition and high metal content. While previous research has primarily focused on using bio-cyanide, bio-sulfate, and bio-ferric compounds from acidophilic bacteria, the potential of bio-oxalic acid for SMPhPCBs treatment and the alteration of their complex structure has not yet been explored. Additionally, this study suggests evaluating the untapped potential of Aspergillus niger in oxalic acid production through mixed cultures with bacteria, marking a pioneering approach. A unique culture of Bacillus megaterium and A. niger was created, inducing bio-stress by bacterial metabolites, including gluconic acid (2683 mg/l) and live/dead bacterial cells in a medium with glucose deficiency. Results demonstrated reducing sugar consumption and oxalic acid over-production in mixed cultures compared to pure cultures, ranging from 1350 to 4951 mg/l at an initial glucose concentration (IGC) of 10 g/l and 4276 to 7460 mg/l at IGC 20 g/l. This over-production is attributed to proposed fungal signaling mechanisms to bacteria. Metal extraction using organic acids and siderophores at 10 g/l pulp density, 24 h, and 60 °C yielded Mn (100 %), Pt (100 %), Pd (70.7 %), Fe (50.8 %), Co (48.3 %), Al (21.8 %), among others. The final valuable residue containing copper, gold, and silver holds potential for future recycling. The study concludes with XRD and FTIR analyses to assess the bioleaching effect on the bio-leached powder. [ABSTRACT FROM AUTHOR]

this study evaluated dentin microtensile bond strength (µTBS) and failure modes (at 24 h and one year), bonding interface regarding hybridization, surface morphology regarding demineralization, in situ metalloproteinase (MMP) activity, and antibacterial effect of three dentin etchants compared to 35% phosphoric acid (PA). The Adper Single Bond 2 adhesive (3 M Oral Care) was applied on moist dentin etched with PA (control) or on air-dried dentin etched with 3% aluminum nitrate + 2% oxalic acid (AN), 6.8% ferric oxalate + 10% citric acid (FO), or 10% citric acid (CA). The µTBS test used 40 human teeth (n = 10). Failure modes and surface morphology were analyzed by scanning electron microscopy (n = 3), while bonding interface morphology and MMP activity were evaluated by laser scanning confocal microscopy (n = 3). Antibacterial activity was evaluated against S. Mutans biofilm by means of viable cells count (CFU/mL). PA presented the highest bond strengths regardless of aging time. PA, AN, and CA showed stable bond strengths after one year of storage. Adhesive and mixed failures were predominant in all groups. Thin hybrid layers with short resin tags were observed for the experimental etchants. The AN-based etchant was able to inhibit MMP activity. All tested etchants presented antibacterial activity against S. Mutans biofilm. This study suggests different dentin etchants capable of inhibiting MMP activity while also acting as cavity disinfectants. • Phosphoric acid bond strength was higher than the tested etchants. • Ferric oxalate + citric acid showed significant bond strength reduction at 1 year. • Gelatinolytic activity was inhibited by aluminum nitrate + oxalic acid. • Bacteria cell viability was reduced according to the pH of the acids. [ABSTRACT FROM AUTHOR]

Iron oxide-based ferrite ceramics, widely applied in high-frequency applications, are conventionally produced through high-temperature sintering processes, often resulting in grain growth and phase transformation. In this study, we used a cold sintering process (CSP) with oxalic acid (OA) as a solvent to consolidate iron oxide (Fe 3 O 4) ceramics at a low temperature of 160 °C. The OA-assisted CSP technique has demonstrated a remarkable capacity to facilitate the dissolution and redeposition of iron oxide ions, leading to the interconnection of Fe 3 O 4 particles, forming densely packed ceramics even at low-temperature sintering. Importantly, CSP maintained particle sizes and hindered phase transitions of Fe 3 O 4. The OA concentrations in CSP had a minimal impact on crystal structure and magnetic properties, but it significantly enhanced microstructural features, density, hardness, and electrical resistance. Compared to reference samples prepared without an aqueous solution or with water alone, the CSP-prepared Fe 3 O 4 ceramics with OA exhibited substantially improved density (a relative density of ∼80 %), mechanical properties (Vickers hardness of 3.5–4.0 GPa), magnetic properties (saturation magnetization >70 emu/g), and electrical resistance (electrical conductivity ∼10−3 S/cm at 102–106 Hz). These findings demonstrate a novel approach to fabricating Fe 3 O 4 ceramics at significantly lower temperatures while still achieving properties comparable to those sintered at high temperatures. [ABSTRACT FROM AUTHOR]

• Herb-medicine residue (HMR) is applied as a thermal reducing agent. • 99.6% of the Li is extracted by oxalic acid (OA) leaching after thermal reduction. • HMR thermal reduction and OA leaching are used for synergistic recovery of Li. • The combined process contribute to improve extraction kinetic of Li. • The whole process realizes the one-step treatment of the two wastes. With the increasing demand for lithium resources, the efficient recovery of lithium from spent lithium-ion batteries (LIBs) has become the focus of social attention. Herein, a combined process of reduction roasting of herb-medicine residue (HMR) and oxalic acid (OA) leaching is proposed to improve the recovery efficiency of lithium. Due to the large amount of reducing gas produced by the pyrolysis of herb-medicine residue, the layered structure of LiNi x Co y Mn z O 2 cathode powder can be destroyed at 650℃ for 10 min, and the cathode powder is converted into Li 2 CO 3 , Ni, Co, MnO. Moreover, about 99.6 % of Li in the roasting residue can be selectively extracted by 0.5 mol L−1 oxalic acid for 20 min. Under the combined action of HMR and OA, the extraction efficiency and kinetics of lithium are improved simultaneously. This work achieves synergistic treatment of two types of waste from the perspective of waste management for waste. Meanwhile, it provides an alternative and innovative approach for the difficult problem of low efficiency of lithium recovery from spent LIBs. [ABSTRACT FROM AUTHOR]

The present study standardized a green protocol for extracting apigenin from Biophytum poterioides. Natural deep eutectic solvents (NADES) and green extraction techniques like microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) were adopted and optimized by response surface methodology. Based on the statistically evaluated results, the optimal solvent was the choline chloride: oxalic acid (NADE 5) at a molar ratio 1:1 with 30% (v/v) of water. MAE using a solid-to-solvent ratio 1:10 for 6 min duration was identified as the optimum condition for the effective extraction of apigenin. A sixfold increase of apigenin was obtained using NADE 5 (1395.767 ± 5.083 mg/L) compared to ethanol (255.718 ± 2.930 mg/L) at the optimal condition. The FT-IR studies aided in confirming the interaction of apigenin with NADES 5. Furthermore, antioxidant studies demonstrated that the NADES 5 extract had a substantial ability to scavenge DPPH radical (IC50 =219.572 μg/ml). Appraisal of the greenness of the developed methods was evaluated using the novel Analytical GREEnness (AGREEprep) metric. The results confirmed that the combination of NADES and MAE offers a rapid and cheap alternative to conventional solvents for sustainable and green extraction and allows easy transfer of the proposed methodology to large-scale extraction of apigenin. [Display omitted] • An eco-friendly method for apigenin extraction has been developed. • Green solvent-mediated microwave and ultrasound-assisted extractions. • Higher yield and reproducibility of apigenin achieved using NADES than ethanol. • Response surface methodology was used for the protocol optimization. • Evaluation of greenness with Analytical GREEnness (AGREEprep) metric. [ABSTRACT FROM AUTHOR]

• Eddy leaching technique was developed to treat heavy metal-contaminated soil. • Concentration of heavy metals in soil reduced as particle size increased. • Highest separation efficiency of hydrocyclone was 84.7%. • Enhanced desorption of heavy metals by eddy leaching compared to OAPE. An eddy deep leaching technology was developed in this paper to address the challenge of treating heavy metal contaminants in industrial mining areas. The desorption effect of As, Cd, Sb and Pb was investigated utilizing chemical leaching and physical eddy techniques. It was found that the heavy metals concentration increased with decreasing particle size. The highest proportion of Cd in the form distribution of soil was in the bound to iron and manganese oxides, while the maximum proportion of As, Sb and Pb were in the residual. The optimal solid-liquid ratio of the hydrocyclone was 1:20, and the corresponding separation efficiency and flow rate were 84.7% and 1.76 m3/hr, respectively. The grade efficiency of soil particle separation increases with particle size and exceeds 99% for particles above 1,000 µm. Leaching experiments have revealed that oxalic acid (OA) and a combination of oxalic acid and EDTA (OAPE) were more efficient than citric acid (CA) and a combination of citric acid and EDTA (CAPE) for the desorption of heavy metals, respectively. The comparison of OAPE and eddy leaching found that the latter improved the desorption efficiency by 9.4%, 7.5%, 7.2% and 7.8% for As, Cd, Sb and Pb compared to the former, respectively. The results demonstrated that the eddy leaching technique could further enhance the desorption efficiency of heavy metals. It is expected to provide technical support for soil remediation with reduced usage of leaching agents. [Display omitted] [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) coordination polymer [Co(ox)(bpy)] 1 (ox = oxalate, bpy = 4,4'-bipyridine) was prepared by hydrothermal synthesis using CoCl2⋅5H2O, oxalic acid, bpy as raw material. Compound 1 is a 2D structure extended by ox and bpy, and it has excellent visible photocatalytic performance. The photocatalytic efficiency of compound 1 could reach up to 98.13% with pH = 10 when two drops of H2O2 were added to methylene blue. The photocatalytic degradation results could be described by the first-order kinetic. Besides, after five cycles, the degradation efficiency decreased only 4.11% (without H2O2) and 5.22% (with H2O2). Meanwhile, the solid fluorescence and UV-Visible diffuse reflection of compound 1 were also studied. What's more, the visible light photo- catalytic mechanism of compound 1 was analyzed more clearly by free radical trapping experiment and Mott-Schottky curve. [ABSTRACT FROM AUTHOR]

In this paper, we report a carbon cloth/amorphous nanoscale Pd (CC/AN Pd) composite electrode and realizes the modifier-free composite of low-cost intractable carbon support and low-loading Pd metal by designing a mild and facile oxidation-ion exchange-reduction (OIR) route. This CC/AN Pd composite electrode presents high activity, robust, cost-effective, modifier-free, micro-nano porous and low Pd loading characteristics compared with the traditional Pd/C electrode. This composite electrode shows superior oxalic acid (OA) oxidization reaction (OOR) catalysis performance, outperforming all the as-reported OOR catalysts especially at high current density. Moreover, on the basis of catalysis performance and the cost of Pd loading amount, this CC/AN Pd composite electrode shows superior hydrogen evolution reaction (HER) catalysis performance with high cost-effective characteristic, surpassing all the as-reported HER catalytic electrodes. Importantly, this composite electrode was used as HER and OOR electrodes to assemble an oxalic acid electrolytic cell (OAEC), which drives 10 mA/cm2 and 100 mA/cm2 current density at only 1.09 V and 1.52 V voltage, respectively, and obtains up to 95.2% average faraday efficiency for 50 mA/cm2 oxalic acid electrolysis. Notable, this CC/AN Pd composite electrode-based OAEC has better energy-saving and stability advantage compared with the commercial CC/Pd–C-based OAEC especially for high current density OA electrolysis. This work opens new avenues to the design of novel composite electrode materials and enables new opportunities in green energy or environmental catalysis areas. [Display omitted] • Amorphous nano Pd/carbon cloth electrode was built by oxidation-ion exchange-reduction route. • This electrode has robust, cost-effective, modifier-free and micro-nano porous property. • This composite electrode can constitute oxalic acid electrolytic cell (OAEC). • This OAEC needs 1.09 V@10 mA/cm2 and 1.52 V@100 mA/cm2 to generate H 2 and OA degradation. • This OAEC has energy-saving and stability advantage compared with commercial OAEC. [ABSTRACT FROM AUTHOR]

In this paper, K 0.5 Na 0.5 NbO 3 (KNN) samples were successfully synthesized via modified Pechini technique with many different chelating agents. Physicochemical studies as differential scanning calorimetry (DSC) measurements, dielectric measurements, impedance spectroscopy and structural analyses confirmed the influence of chelating agent on phase transformation from the ferroelectric orthorhombic to tetragonal and ferroelectric tetragonal to paraelectric cubic phase. The study of the charge transfer mechanism of KNN is carried out based on small polaron hopping theory. In addition, the high dielectric constant associated with a low dielectric loss observed for KNN material obtained using combination of glycine and oxalic acid makes it a possible use in electronic devices. [ABSTRACT FROM AUTHOR]

Memristor has a high-density information storage capability and can manipulate a large amount of data computing in parallel, so it can be applied in neuromorphic computing. The advanced intelligent applications are one of the major breakthroughs made in the past decade based on the memristor's research. In this work, amorphous Nb 2 O 5 film as functional layers on flexible niobium (Nb) foil were fabricated by anodic oxidation in oxalic acid aqueous solution. A broad spectrum of well-defined color was acquired by varying the anodic voltage during oxidation of the Nb foil. The results of spectroscopic ellipsometry (SE) tests show that the Nb 2 O 5 layers with various colors have different thickness. The willow yellow Nb 2 O 5 film with a thickness of ∼85 nm based memristor show an excellent memristive memory behavior. Finally, it was proposed that the potential well of the ionization center tilts under the external electric field, which causes the probability of charge to escape along and against the direction of the external electric field to explain the memristive effect of the device. This work opens up a new method for fabricating the flexible memristor, which provides the potential applications for next generation self-color electronics. [ABSTRACT FROM AUTHOR]

α-Al 2 O 3 with outstanding physical and chemical properties makes it an excellent feedstock to prepare advanced ceramics, but its preparation at low temperature still remains a challenging task. Herein, hydroxyl aluminum oxalate (HAO) with an average particle size of 196 nm was successfully prepared by solvothermal reactions using 40 vol% ethanol aqueous solution (EAS) at 200 °C for 2.5 h. Meanwhile, HAO acting as seed was introduced into Al(OH) 3 modified with oxalic acid (AHOD) for the first time. The results demonstrated that α-Al 2 O 3 can be obtained by seeding 5% HAO at 900 °C and the initial nucleation temperature was as low as 780 °C. The morphologic evolution mechanism of obtained α-Al 2 O 3 was proposed. Kinetic analysis displayed that the activation energy of γ-Al 2 O 3 to α-Al 2 O 3 after seeding 5% HAO was 197.01 kJ/mol. [ABSTRACT FROM AUTHOR]

To achieve efficient electromagnetic wave absorption (EWA) performance with requirements of low density and thin thickness, three-dimensional (3D) hierarchical CNTs/VO 2 composite microsphere was successfully synthesized though an ultrasonic atomization process in this work. The phase composition, morphology, EWA performance and corresponding mechanism were investigated. The VO 2 microspheres (MS) was obtained via the complete reduction of V 2 O 5 by oxalic acid, and the introduced CNTs were uniformly distributed around VO 2 MS. The addition of CNTs both improved the impedance matching and provided multiple attenuation modes. The highly conductive CNTs enhanced conductivity further increasing conductance loss. Moreover, heterogeneous interfaces formed between CNTs and VO 2 phase generated strong polarization loss. Furthermore, the construction of 3D structure not only benefited the stability of structure but also extended the paths of EW reflection and scattering thus consuming more EW energy. With the synergistic effect of favorable impedance matching and attenuation ability, the excellent EWA performance was achieved that the minimum reflection loss was −58.2 dB with the effective absorption bandwidth of 3.94 GHz in X band. This research plays a significant guiding role in structural construction and optimization of EW absorber. [Display omitted] • Constructing 3D hierarchical composite microspheres. • The superior electromagnetic absorption performance was achieved. • The impedance matching and attenuation ability were enhanced simultaneously. • The electromagnetic absorption mechanism was in-depth investigated. [ABSTRACT FROM AUTHOR]

Recycling waste into efficient adsorbents to remove pollutants again provides a compatible solution for the sustainable development of water resources. Here, Mg2+, Al3+, and Fe3+ metal ions from oxalic acid leaching mixed-dimensional palygorskite clay wastewater were successfully converted into mixed metal oxides (MMOs) through a simple precipitation-calcination process. MMOs prepared under different precipitation pH conditions or different washing schemes were used to remove the anionic dye Congo red (CR) and cationic dye Methyl violet (MV). The relatively pure Mg-Al-Fe MMO obtained at pH 13 with thorough washing had ultrahigh adsorption capacity for CR, up to 1369 mg/g. In the presence of sodium oxalate byproducts without washing, the prepared MMOs containing Fe 3 O 4 , sodium carbonate, and carbon byproducts had higher removal capacities for cationic dye MV, with a maximum of 1098 mg/g. Moreover, the series of MMOs exhibited strong removal capability for CR + MV mixed dyes and satisfactory cycle stability. This work provided a new perspective on the sustainable utilization of mineral resources and water resources. [Display omitted] • Sustainably utilized acid-leaching clay wastewater to fabricate MMOs adsorbent. • Precipitation pH and water washing programs affected the properties of MMOs. • Changing the properties of MMOs regulated their affinity for CR and MV. • This work provided a new way for sustainable utilization of mineral wastewater. [ABSTRACT FROM AUTHOR]

Bauxite residues known as "Red Mud" (RM) are the principal waste of caustic digestion of bauxite from the Bayer Process, whose costs of disposal are expensive and cover 5 % of the total costs of extraction and processing for aluminum production. Nevertheless, this material can be considered an important source of high-value elements, such as rare earths (REEs) and metals, Fe, Ti, Al and others. In this work, the focus has been on the recovery of iron in the form of the compound Fe(II) oxalate. Four types of acids have been used (HCl, H 2 SO 4 , H 3 PO 4 , H 2 C 2 O 4) for iron extraction from RM coming from Montenegro. Hydrochloric acid shows a higher iron extraction capacity, reaching an iron extraction yield in solution of 22.6 %. Sulfuric and phosphoric acid, instead, interacted with RM leading to the formation of sulfonate and phosphate species, inhibiting the leaching ability of individual species. Oxalic acid showed the least amount of iron ions extracted but formed a stable ionic complex in solution, Fe 2 (C 2 O 4) 3 ∙2 H 2 O. Starting from this complex it was possible to recover the corresponding salt by a reduction and precipitation process. Through a pre-treatment with HCl and a subsequent treatment with oxalic acid, it was possible to obtain a better yield of iron oxalate. Starting from the laboratory scale, a CHEMCAD plant was conceptualized with a yield higher than 16 % per pass (repeatable 3 times with a global iron yield>50 %) and obtaining iron(II) oxalate dihydrate with purity up to 96%wt. In a holistic view of the problem, the proposed process can operate in parallel with other procedures proposed in the literature for the recovery of other valuable substances from red mud. Not applicable. • Valorization and reuse of red mud through chemical treatments of acid leaching and reduction. • Selective coordination of Fe3+ ions with oxalic acid and subsequent salt precipitation. • Development of a preliminary procedure for the synthesis of high-purity iron oxalate from RM. • Development of a plant scheme for the production of Fe 2 C 2 O 4 with material and energy balances. [ABSTRACT FROM AUTHOR]

[Display omitted] • CsPbBr 3 /graphite or CsPbBr 3 /platinum photo-electrodes for solar fuels production. • Photo-electrocatalytic CO 2 reductions to oxalic acid by CsPbBr 3 hybrid films. • Hybrid CsPbBr 3 films stable in water environment. • Electrochemical interfaces properties of CsPbBr 3 graphite or platinum thin films. CsPbBr 3 halide perovskites have been recently received a lot of interest in the field of photo and electro catalysis, solar cells, and photodetectors due to their tunable band gap, large absorption coefficient and high carriers' mobility. However, CsPbBr 3 poor water stability limits its real application and the development of related devices. In this work, hybrid CsPbBr 3 /platinum (Pt) and CsPbBr 3 /graphite (C) photo-electrodes are employed, for the first time, in aqueous environment for the photo-electrochemical CO 2 conversion to liquid products. Hybrid photo-electrodes were prepared depositing CsPbBr 3 by spin coating and sputtering Pt or C on top of it to obtain a homogeneous protective layer with the same thickness. Thanks to the Pt and C layers, the instability of the perovskite in water environment is overcome and the new hybrid electrodes obtained still showed the ability to absorb light in the visible region producing photocurrent. The as-obtained photo-electrodes demonstrated energy band values suitable to reduce carbon dioxide by photo-electrocatalytic reaction in water environment. As main results, these hybrid electrodes produced complex organic molecules such as oxalic acid with Faradic efficiencies close to 44% (at −0.8 V vs Ag/AgCl) using graphite in combination with CsPbBr 3. [ABSTRACT FROM AUTHOR]

Schefflera bojeri possesses several therapeutic virtues: the leaves are used to alleviate hypertension and the bark for the treatment of diabetes. This work aims to verify its potential medicinal virtues. Quantitative analyses of phytochemicals from the leaves and bark were performed using spectrophotometric methods. The antioxidant capacity was determined with DPPH and FRAP assays. The analgesic and anti-inflammatory activities of the two methanol extracts were respectively assessed on the in vivo experimental pain and oedema models. Their antidiabetic property was determined using the oral glucose tolerance test in mice. The acute toxicity of the methanolextracts was evaluated in mice. The total bioactive compound content (TBCC) in the leaves was two-fold more than in the bark as well as the total phenolic compounds (TPC). Oxalic acid (22.39%) was the main compound quantified in the bark, while ferulic acid (18.42%) was of the main molecule in the leaves. The leaves exerted a stronger antioxidant activity than the bark against DPPH but exerted a similar activity on ferric ions. Both the methanol extracts showed a similar dose-dependent analgesic activity (p < 0.05). Yet, the anti-inflammatory activity of the methanol extracts at each phase of observation (1h, 2h, 3h and 4h, p < 0.05, respectively) was in a dose-dependent manner however the leaves exerted more potent activity than the bark at the dose of 200 mg/kg at each time of observation. Both of the extracts demonstrated a dose-dependent hypoglycaemic activity at 60- and 120 min post glucose administration (p < 0.01). Both of the methanol extracts did not show any sign of preliminary toxicity. The secondary metabolites in the extracts could be at the origin of preliminary pharmacological properties justifying the therapeutic virtues of this species. Further phytochemical, pharmacological and toxicological studies should be undertaken to better clarify these biological activities. [Display omitted] • Schefflera bojeri leaves are used to alleviate hypertension and its bark is used to treat diabetes. • Oxalic acid (22.39%) was the major compound quantified in the bark and ferulic acid (18.42%) was those of the leaves. • The methanol extracts exerted antalgic and anti-inflammatory activities in a dose-dependent manner. • The methanol extracts decreased the glycaemia dose-dependently. • The methanol extracts did not reveal any toxicity signs using an acute toxicity assay. [ABSTRACT FROM AUTHOR]

• The effects of three pre-activators (colloidal Ti, oxalic acid, phosphoric acid) on the performance of a PCC was compared. • The pre-activators promote nucleation by peeling off the original oxide film and increasing the specific surface area. • Different pre-activators did not alter the formation mechanism, but significantly changed the growth rate and morphology. • Phosphoric acid was the overall best choice for pre-activating the Mg alloy considering on the PCC performance and cost. In this study, Mg–6.0Zn–3.0Sn–0.5Mn (ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid, and a phosphate conversion coating (PCC) was prepared on the alloy surface. The morphology and corrosion resistance of the prepared PCCs were investigated. Surface morphology studies showed that the phosphate crystals that formed the coating were the smallest for the sample pre-activated by phosphoric acid. The coating on the colloidal Ti and the phosphoric acid samples had the largest and the smallest thickness and surface roughness, respectively. The reason for the discrepancy was analyzed by comparing the surface morphologies of alloy samples immediately after the pre-activation treatment and various phosphating treatments. X-ray diffraction analysis revealed that all three PCCs contained the same compounds. The corrosion resistance time from the copper sulfate drop test and the electrochemical data from the potentiodynamic polarization curves showed that the coating pre-activated by phosphoric acid had the best corrosion resistance. Finally, the 1500 h neutral salt spray corrosion test confirmed that the phosphating treated magnesium alloy, which was pre-activated by phosphoric acid, exhibited excellent corrosion resistance and behavior. [ABSTRACT FROM AUTHOR]

This study investigates the production of cellulose nanofibers (CNF) from Barley straw using ultrasound-assisted deep eutectic solvent (US-DES) treatment for biomass fractionation and subsequent high-intensity ultrasonication (HIUS) for nano-fibrillation. Two deep eutectic solvents (DES), synthesized from choline chloride (ChCl) and oxalic acid dihydrate (OAD) at 1:1 and 2:1 M ratio, achieved solubilisation of over 80 % of lignin and hemicellulose under optimal conditions. The purification of these DES-treated materials resulted in cellulose with a purity >88 %. CNFs, characterized by a size of <100 nm, a polydispersity index under 0.5, and a zeta potential lower than −30 mV, were successfully isolated through a combination of wet grinding and HIUS treatment. SEM and XRD results showed the formation of a network of interconnected fibres with a Type I cellulose structure. This research highlights Barley straw's potential as a sustainable source of high-value CNF from agricultural waste. [Display omitted] • >80 % of the lignin was solubilised using US-DES treatment at optimal conditions. • US-DES treatment resulted in >85 % hemicellulose solubilisation at optimal conditions. • The purification of US-DES treated samples led to >88 % cellulose purity. • >80 % nano-fibrillation efficiency was achieved during CNF production. • XRD analysis revealed that the produced CNF exhibited Type I cellulose structure. [ABSTRACT FROM AUTHOR]

[Display omitted] In this study, bauxite tailings were innovatively employed as the coagulant resource in the treatment of nanofiltration concentrated landfill leachate (NCLL) via bipolar membrane electrodialysis (BMED). The employment of H 2 C 2 O 4 as the leaching acid, in lieu of HNO 3 , not only promoted the leaching of metal ions but also minimized the competitive migration of free H+, attributable to its chelating effect. The COD removal increased from about 40.4 % to about 49.9 %, while the energy consumption (EC) decreased to about 0.05 kWh/g COD when the acid is replaced by H 2 C 2 O 4. An optimal dosage of bauxite tailing is crucial for effective COD removal. An increase in the initial concentration of H 2 C 2 O 4 benefits metal leaching, while, an excessive concentration thereof augments the competition of H+ ions, thereby impeding the coagulation process. Furthermore, the current density exerted a notable impact on both COD removal and EC, with an optimal density identified at 5 mA/cm2. Connecting more treatment units still maintains COD removal efficiency at approximately 50 %, with a significant reduction in EC of about 24 %, necessitating only 0.038 kWh/g COD. Humic-like and fulvic-like acids are efficiently coagulated, which represent the principal biorefractory substances in NCLL. Consequently, this research delineates a novel approach for the utilization of bauxite tailings and the treatment of NCLL. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel [TBP]-ionic liquids with different anions were used for ABS formation in combination with ammonium-sulfate. • Partition studies showed that [TBP][DTPA]/(NH 4) 2 SO 4 ABS demonstrates the highest extraction efficiencies for Co, Ni, and Mn. • The optimized ABS was applied for the recovery of valuable metals from the cathode of the LCO battery from sulfate leachate. • Co and Li extraction and separation from the leaching solution of spent LIB was achieved. • A sustainable and efficient integrated extraction platform for separation and concentration of Co and Li from spent battery was proposed. The consistent expansion of the lithium-ion battery (LIB) market, coupled with their relatively brief lifespan, necessitates the development of efficient and sustainable LIB recycling strategies. Recycling is crucial not only for the recovery of critical metals like Co(II) and Li(I) from the cathode material as a secondary resource but also from an environmental perspective. This study explores the use of a series of aqueous biphasic systems (ABS) with synthesized tetrabutylphosphonium ionic liquids (ILs) and ammonium sulfate as extraction platforms for metals from LIB cathode. Firstly, liquid–liquid equilibrium phase diagrams for each ABS were established, and partitioning experiments were conducted to assess the Co(II), Ni(II), Mn(II), and Li(I) recovery efficiencies. We observed distinct partitioning behaviors for the metals, with tetrabutylphosphonium diethylenetriaminepentaacetate, [TBP][DTPA], showing recovery efficiencies exceeding 98% for Co(II), Ni(II), and Mn(II). At the same time, Li(I) was predominantly retained in the aqueous salt-rich phase. By fine-tuning ABS operational parameters such as pH, temperature, system composition, and phase ratio, we identified optimal conditions for extracting metals from the cathode material of lithium-cobalt-oxide (LCO) batteries using sulfate lixiviate. Introducing [TBP][DTPA] after the leaching process induced ABS, achieving remarkable recovery efficiency over 95% for Co(II) in the IL-rich phase, with all Li(I) remaining in the lower phase. Cobalt was subsequently extracted using oxalic acid to precipitate as Co-oxalate from concentrate, while Li(I) was isolated from the aqueous phase using ammonium carbonate. After the "cleaning" of the IL-rich phase, the [TBP][DTPA] was recovered and reused in four consecutive cycles, with small detected losses on the recovery efficiency of Co(II) and Li(I). Therefore, our innovative strategy combines sulfate-based lixiviants with IL-ABS technology, thereby enhancing selectivity and sustainability within one of the most efficient lixiviant systems widely employed in the industry. This technological advancement presents a promising pathway for the recycling of spent batteries, offering substantial environmental advantages within the well-established and extensively utilized realm of metal recovery technology in the industry. [ABSTRACT FROM AUTHOR]

Magnesium oxalate cement is an alternative binder made by reacting dead-burned magnesia and oxalic acid salts. Dead-burned magnesia, which has a high carbon footprint, was replaced at different levels (25–100 %) with copper slag, as a source of iron and thus a reactive component, or silica fume, as an inert or low-reactivity component. The powder mixtures contained ∼25–35 % oxalate, by mass. Physical and mechanical properties were investigated as well as changes in the mineralogy and morphology of paste and mortar specimens. Replacement of up to 50 % of dead-burned magnesia yielded strong (> 30 MPa) and water-resistant mortars with extended setting times, for mixtures with lower oxalate content. Mixtures with higher oxalate content and those without any dead-burned magnesia suffered significant strength loss in water. When copper slag was used, humboldtine, an iron oxalate, formed instead of or in addition to glushinskite, the main reaction product of magnesium and oxalate ions. Silica fume did not yield any crystalline reaction products. • Magnesium oxalate cement is an acid-base binder with a low carbon footprint. • Dependence on dead-burned magnesia hinders the attainment of carbon negativity. • Copper slag and silica fume can partially replace dead-burned magnesia. • Replacement with industrial wastes can extend setting times and increase strength. • Copper slag contributes humboldtine to the main reaction product glushinskite. [ABSTRACT FROM AUTHOR]

• SFC was used for the analysis of anthraquinones in Frangula alnus for the first time. • Seven derivatives could be resolved in less than six minutes on a DIOL phase. • The method permits the separation of glycosides and aglyca at the same time. • The assay was validated and is well applicable for real sample analysis. Anthraquinones are the major bioactive compounds in alder buckthorn , a plant with a long history of use for the treatment of obstipation in European and Asian traditional medicine. As these metabolites are also associated with toxic side effects, reliable analytical techniques for their determination are essential. Previously described methods mainly utilized Liquid Chromatography for this purpose, as the photometric assay described in the current edition of the European Pharmacopoeia lacks selectivity. In this study, the development and application of an alternative approach, Ultra-High Performance Supercritical Fluid Chromatography, is presented, facilitating the qualitative and quantitative determination of seven anthraquinone derivatives in under six minutes. This was possible by using a Torus™ DIOL column and a modifier comprising methanol with 10 % acetonitrile and 2.5 mM oxalic acid; applying a flow rate of 1.6 mL/min and an elevated temperature of 55 °C enabled optimal resolution. Regarding selectivity, linearity (R2 ≥ 0.9995), precision and accuracy (recovery rates between 96.6 and 103.3 %), all results were in line with the respective ICH requirements. Practical applicability of the assay was confirmed by analyzing different samples, including commercially available plant material, phytopharmaceuticals containing Frangula bark and wild collected samples. Except of the latter, glucofrangulin A always was the dominating compound; however, the overall anthraquinone content showed to be very variable ranging from 2.18 to 51.32 mg. [ABSTRACT FROM AUTHOR]

• Vivianite is completely dissolved in HCl and H 2 SO 4 at a H+/P molar ratio of 2.5. • Oxalate precipitates Fe(II), Ca, and Mg ions to minimize impurities in leachate. • Phosphoric acid leaching + oxalate precipitation yields pure ferrous oxalate. • Integrating Fe recovery and oxalic acid reuse with P recovery. This paper examines the acid leaching efficiencies of Fe and P from vivianite slurry (VS, Fe 3 (PO 4) 2 ·8H 2 O), which is magnetically separated from anaerobic digested sludge, and elaborates on Fe and P reuse routes. The characteristics and dissolution behavior of raw VS in hydrochloric, sulfuric, phosphoric, oxalic, and citric acids are investigated. Results reveal that the primary impurities in VS are organic matter, other phosphate compounds, and Mg present in the vivianite crystal structure. Hydrochloric and sulfuric acids could effectively extract P (90%) from VS at an optimal hydrogen-to-phosphorus (H⁺/P) ratio of 2.5, compared with sewage sludge ash (SSA) that normally needs an H⁺/P ratio greater than 3. Hence, VS can be employed as an alternative P resource following a similar recovery route used with SSA. However, in comparison to SSA, VS use can decrease acid consumption in P extraction and the requirement for the extensive purification of cationic impurities. Furthermore, oxalic acid effectively facilitates the separation of P and Fe in VS by precipitating Fe as insoluble ferrous oxalate in acidic conditions, leading to a high Fe recovery rate of 95%. The recovery and reuse of Fe through the oxalic acid route further improves the feasibility of VS as an alternate resource. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of agricultural wastes as raw materials to produce adsorbents for treating dye wastewater is a remarkable research topic. Given that maize (Zea mays L.) is one of the most productive crops, a large amount of discarded corn-cobs is not utilized every year. In this work, solid residues from corn-cobs hydrolyzed by oxalic acid were modified with polyethyleneimine (PEI) and catechol to form adsorbents. The adsorption performances for Congo red (CR) dye were measured, including the effects of initial solution concentration, temperature, and adsorption time. The maximum equilibrium adsorption capacity for CR was ∼650 mg/g at 30 °C, which exceeded that of many biomass-based adsorbents reported in recent literature and even reached the level of some carbon materials. The adsorption of CR molecules followed the pseudo-second-order kinetics. The thermodynamic interaction between CR molecules and the adsorbents was an endothermic process. The adsorption state of the CR molecules on the adsorbents was Langmuir monolayer adsorption, and the adsorption type was physical adsorption. The thermal stability of the adsorbents was similar to that of corn-cobs. [Display omitted] • Corn cobs is prepared as adsorbent through acid hydrolysis and PEI modification. • Experimental adsorption capacity for Congo red is 650 mg/g in neutral water at 30 °C. • The adsorption capacity for Congo red dye reaches the level of carbon materials. • Kinetic and thermodynamic parameters, as well as adsorption mechanism are given. [ABSTRACT FROM AUTHOR]

Tellurium is a technology-critical element (TCE), with relatively limited data on its behavior in the environment, especially the pedosphere. As with other TCEs, its more widespread use, especially in new energy sources, might lead to Te spillage during production or in the eventual waste. Investigation of tellurium's interaction with soil is a necessary step in the research into the physiochemical transformation and determining the mobility of different tellurium species. To broaden the hitherto scarce knowledge of tellurium behavior in the soil environment, selected soluble tellurium compounds were introduced into different types of well-characterized soil (content of fertilizers, organic matrix, clay minerals, Mn, Fe, pH). The study of Te(IV) and Te(VI) sorption indicated that after 7 days the sorption is quantitative and close to 100%. Addition of Fe 2 O 3 to a soil deficient in Mn and Fe increases its sorption potential by about 10 percentage points. Based on fractionation study (0.11 mol L−1 CH 3 COOH, 0.1 mol L−1 ascorbic acid in oxalate buffer (pH 3), 30% H 2 O 2 at 85 °C followed by 0.5 mol L−1 CH 3 COONH 4), it was shown that the presence of Mn/Fe (oxyhydr)oxides plays an essential role in the mobility of Te, especially Te(VI), regardless of the soil type. In the soil poor in reducible fraction and rich in organic matrix (peat), the organic fraction was responsible for the immobilization of Te, especially Te(IV). Extraction of the mobile fraction after incubation in the presence of DI water (Te extraction: 7–8%), oxalic acid (5–7%) or citric acid (6%) (mimicking rhizosphere activity) indicated that these did not play a significant role in Te retention. Nevertheless, soil modification with biocarbon limited the effect of citrates on Te mobilization. This knowledge is fundamental, i.e. in the context of soil remediation processes and counteracting the migration of Te in the environment from anthropogenic sources (e.g. solar farms). [Display omitted] • Soils differing in Mn/Fe (oxyhydr)oxides content differ in Te(IV/VI) sorption. • Te(IV) and Te(VI) sorption after 7 days is close to 100%. • Te(IV) binds stronger, mostly to Mn/Fe (oxyhydr)oxides and organic matter (long-term). • Up to 60% of Te(VI) is bound to reducible phases in soil. • Addition of Bio-C and LMWOA has no significant impact on Te retention. [ABSTRACT FROM AUTHOR]

[Display omitted] • The extraction of indium, zinc and iron from IBZF using DES is achieved. • The entire process is a green closed-loop system. • Water is both co-solvent and diluting precipitant. Indium, a strategic key metal, is mainly recovered from zinc leaching residue. However, a challenging problem in the treatment of zinc leaching residue is how to efficiently and cleanly treat the poorly soluble phase, the indium-bearing zinc ferrite (IBZF). Here, we propose a novel strategy for the selective extraction of indium, zinc and iron from IBZF. By introducing water to regulate the coordination environment of a choline chloride-anhydrous oxalic acid based deep eutectic solvent (ChCl-Oxa based DES), efficient leaching and deep separation of indium, zinc and iron were achieved. Water, acting as both co-solvent and diluent, played a critical role in the whole process. The addition of a little water reduces the viscosity of the DES, thereby improving the leaching of indium, zinc and iron. Under specific leaching conditions (leaching temperature of 90 °C, liquid/solid ratio of 20:1 ml/g, molar ratio of ChCl:Oxa = 1:1, molar ratio of DES:H 2 O = 1:3 and reaction time of 3.5 h), the leaching efficiencies of indium, zinc and iron were 96.27 %, 95.55 % and 96.33 %, respectively. The subsequent addition of large amounts of water dilutes and dissociates the structure of the DES, facilitating the stepwise precipitation and deep separation of metal ions. The precipitation efficiency of zinc and iron reached 93.06 % and 98.07 %, respectively. Residual indium ions in the solution were effectively adsorbed by activated carbon, with a recovery efficiency of 75.7 % after five cycles of adsorption. The solution separated from the metal ions was well regenerated by evaporation and addition of Oxa. Our work represents a novel approach for the recycling and clean utilization of zinc leaching residue. And the regulation of the coordination environment of metal ions in DES is proved to have great potential in metal recycling. [ABSTRACT FROM AUTHOR]

• 5-HMF production from chitosan catalysed by DES were explored. • High efficiency was obtained under the optimized conditions. • The interactions between the HBA and HBD of DES were confirmed. • The solid residuals were characterized to reveal the conversion mechanism. This study explores an efficient catalytic system for the conversion of chitosan into 5-hydroxymethylfurfural (5-HMF) under hydrothermal conditions. The catalysts used are deep eutectic solvents (DESs) comprising choline chloride (ChCl) as the hydrogen bond acceptor (HBA) and various organic acids as the hydrogen bond donor (HBD). Among the DESs tested, the ChCl: oxalic acid (OA) combination exhibits the highest catalytic activity, resulting in a yield of 27.5% 5-HMF employed the optimized conditions. To elucidate the interaction between ChCl and OA, various analytical techniques were employed, including quantum chemical calculations, nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR). These investigations confirmed the formation of strong hydrogen-bonds between ChCl and OA. Furthermore, the solid residues obtained during the conversion process were characterized using FTIR, X-ray diffraction (XRD), and scanning electron microscopy (SEM). These analyses provide insights into the chemical structures and morphologies of the residues, revealing the gradual conversion of chitosan, along with the formation of humin by-products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Predominantly VO₂ phase obtained by easy and fast chemical synthesis. • A good quality precursor solution to obtain a stable phase of vanadium. • Dispersing precursor-solution medium influences the final vanadium phase. • Same concentration in different dispersing mediums provides different morphologies. • The VO 2 active layer device showed a write-once-read-many memory behavior. This study explores the influence of precursor solution composition and solvent selection on the synthesis of vanadium oxide (VO 2) thin films tailored for resistive memory applications. The vanadium pentoxide and oxalic acid molar ratio and the dispersing medium (ethanol, water, and their mixture) were varied. Water content significantly influenced the VO 2 phase, morphology, and film thickness. Ethanol yielded mixed vanadium oxide phases VO 2 − Tetragonal, V 2 O 5 − Orthorhombic, and Monoclinic) and a film with minor imperfections. Conversely, the active layer prepared using an aqueous medium showed a predominant VO 2 − Monoclinic phase, albeit with a non-uniform film. An ethanol–water mixture produced the most uniform morphology and a mixture of vanadium oxide phases (VO 2 − Tetragonal, V 2 O 5 - Orthorhombic). All devices displayed resistive switching behavior. VO 2 -containing devices exhibited a more pronounced transition from an ohmic conduction state to a space-charge-limited conduction mechanism. ON-state currents remained consistent, while OFF-state currents varied notably. [ABSTRACT FROM AUTHOR]

• The early failure of an AISI316L C-type Bourdon tube from a pressure gauge was investigated. • The microstructure in the failure zone was suspected of sensitization and exhibited intergranular corrosion. • The most probable cause of the early failure was an improper welding that causes the sensitization of the microstructure in the HAZ. This paper presents the failure analysis of a C-type Bourdon tube made of AISI 316L stainless steel, which was part of a pressure gauge. For the study, chemical composition and microstructure of the Bourdon tube were determined. Additionally, electrochemical attack with oxalic acid was used to asses if the microstructure was suspected of sensitization in samples taken near to and away from the failure. Finally, fractographic analysis of the failed Bourdon tube was accomplished by scanning electron microscopy. The results showed that the failure was due to an intergranular corrosion phenomenon that embrittled the material in the area close to the welding between the Bourdon tube and the joint. [ABSTRACT FROM AUTHOR]

• Comprehensive comparison of treatments for the control of soft rot and extension of postharvest shelf life in kiwifruit and systematic conclusions obtained. • A large amount of valid data has been collected and the results are highly reliable. • The results of the analysis can provide a basis for researchers to design effective combination programs. This meta-analysis covers 30 different interventions, as well as 5 tests of bacteriostatic activity. The results showed that 10 mmol/L oxalic acid solution had the best inhibitory activity against Botryosphaeria dothidea. The best intervention to inhibit the increase in morbidity in kiwifruit was the sprayed by 0.1 % sodium-rich calcium + 25 % azoxystrobin SC 2000-times liquid. Applied pullulan-active-coating + 10 g/L potassium metabisulfite was the best method to inhibit the increase in lesion diameter and suppress the accumulation of soluble solids. 5 % chitosan + 1 % tea polyphenols + 1.5 % Ca(NO 3) 2 liquid maintains high levels of soluble solids in kiwifruit. 5 % chitosan + 1 % citric acid + 1.5 % Ca(NO 3) 2 liquid can effectively promote the accumulation of soluble sugar. Pre-harvest sprayed by 5 % chitosan + 1 % antibacterial peptide + 1.5 % Ca(NO 3) 2 liquid is the best measure to inhibit titratable acid accumulation in kiwifruit. Fumigation treatment with 0.6 µL/mL citral allowed kiwifruits to maintain high firmness. The use of pullulan-active-coating + 1 g/L potassium metabisulfite was the best treatment to inhibit fruit weight loss. These results are useful for future control of kiwifruit soft rot or postharvest storage, with a view to informing researchers in designing effective combination programs based on these results. [ABSTRACT FROM AUTHOR]

Red mud (RM) and spent oyster mushroom substrate (SOMS), by-products of industrial and agricultural production, can be recycled for polluted freshwater purification, bringing about a win-win situation. In this study, unacidified RM and RM acidified with oxalic acid (O-RM) and hydrochloric acid (H-RM), respectively, were mixed with SOMS to produce a porous ceramsite as a potential constructed wetlands (CWs) substrate. The results showed that the O-RM, H-RM, and RM ceramsites displayed fine compressive strengths of 7.75 ± 1.14, 8.40 ± 1.30, and 8.84 ± 0.69 MPa after calcining at 950 °C for 30 min, respectively. The phosphorus adsorption capacities of H-RM, O-RM, and RM ceramsite at a solid-liquid ratio of 25 g/L were 1.18 mg/g, 0.88 mg/g, and 1.06 mg/g, respectively. Toxicity release experiments showed that the ceramsites did not cause secondary environmental pollution, except for arsenic (ranging from 0.210 to 0.238 mg/L). The H-RM ceramsite was tested in a tidal flow-vertical flow CW (TF-VFCW) with Iris pseudacorus L. and Canna indica L plants. In the TF-VFCW, the average chemical oxygen demand (COD), ammonia nitrogen (NH 4 +-N), total nitrogen (TN), and total phosphorus (TP) removal rates were 81.01, 90.25, 66.90, and 77.32 %, respectively. Plant growth had less impact on COD and NH 4 -N removal but had greater limited TN and TP removal. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analysis confirmed that acid pretreatment and the incorporation of SOMS significantly increased the surface and interior porous structures of the ceramsite and enhanced phosphate adsorption by the polyhydroxyl aluminum-iron complex ions. Bacteroides and Campylobacter used the energy produced during polyhydroxyalkanoic acid (PHA) catabolism to absorb phosphorus. Therefore, the synergistic effect of the substrate, plants, and microorganisms achieved the removal of phosphorus from CWs and offered effective and environmentally friendly recycling of RM and SOMS. [Display omitted] • Phosphorus is an essential nutrient causing eutrophication in the freshwater ecosystems. • Spent oyster mushroom substrate (SOMS) is a good pore-forming material and can be used to prepare porous red mud ceramsite. • The ceramsite does not leach toxic pollutants and has good compressive strength. • In CWs, the ceramsite plays an effective role in removing pollutants. [ABSTRACT FROM AUTHOR]

The oxidation mechanism of methylglyoxal (CH 3 COCHO) in the aqueous phase plays a crucial role in the formation of secondary organic aerosols (SOA). To date, the investigations of reaction mechanisms of MG in the aqueous phase still needs to be refined, and the oxidation mechanisms of MG in the existence of various oxidants (e.g., H 2 O 2 , O 3, ∙NO 3 , etc.) are in controversy. In this paper, we investigated the hypothesis that small-molecule organic acids are the primary products in cloud water and fog droplets, while large-molecule organic acids and oligomers play crucial roles in wet aerosols. Specifically, the hydration reaction, oxidation mechanism and oligomerization reaction of MG in aqueous phase were investigated on a theoretical basis. It has been indicated that the hydration reaction is a significant initiating reaction of MG in the atmospheric aqueous phase, whose generated hydrated compounds played a critical part in the process of forming oligomers. The aqueous oxidation reaction of MG could form a variety of organic acids, including pyruvic acid, formic acid, acetic acid, and oxalic acid. In the presence of OH radicals, pyruvic acid was the main first-generation production, which undergoes further reactions to form acetic acid, oxalic acid, and mesoxalic acid. Acetic acid was mainly derived from the reaction of OH radicals with pyruvic acid, whereas oxalic and mesoxalic acids were mainly generated by the OH radical reaction for MG and pyruvic acid. Of these, the formation of acetic acid was thermodynamically most favorable. Additionally, the reactions of MG with other oxidants also provided the possible pathways for pyruvic acid production. At 298 K, we calculated the rate constants for the reaction of MGHY with NO 3 , OH, HO 2 radicals, and O 3 to be 4.48 × 108, 2.54 × 107, 1.26 × 10−2, and 4.38 × 10−4 M−1 s−1, with atmospheric aqueous phase lifetimes (τ) of 4.43, 3.12 × 103, 2.21 × 1011, and 3.17 × 108 h, respectively. The theoretical results from this work will facilitate the explanation for the MG reaction process in the aqueous phase so as to further correctly estimate the relationship between the aqueous phase chemistry of MG and the formation of SOA. [Display omitted] • The aqueous oxidation reaction of methylglyoxal was studied theoretically. • The main oxidation products are organic acids. • OH radicals are the main oxidant for removal of methylglyoxal. • The hydration of methylglyoxal is favored at higher RH. [ABSTRACT FROM AUTHOR]

[Display omitted] • Function of oxalic acid assisted Fenton-like reaction in composting carbon conservation was verified. • The concentration of ·OH was increased via using Fenton-like reagent during composting. • Fenton-like reagent addition facilitated organic matter decomposition and humification. • The degree of aromatization was facilitated by Fenton-like reagent monitored by spectral determinations. • Fenton-like treatment also facilitated microbial activity for improving humification. To illustrate the role and mechanism of using oxalic acid (OA) and Fenton reagent to enhance carbon transformation and humification in the co-composting of swine manure and corn straw, four different treatments, SW1 (Control), SW2 (Fenton reagent), SW3 (10 % OA), and SW4 (Fenton reagent + 10 % OA) were set up for an 80-day pilot-scale composting. Compared with the Fenton pretreatment, the contents of Fe (II) and hydroxyl radicals (·OH) in the SW4 treatment increased by 20.25 %-54.55 % and 6.39 %-71.00 %, respectively. This confirmed the role of OA in protecting Fe (II) and maintaining the generation of ·OH during the composting. Compared with Control, Fenton-like reagent amendment facilitated decomposition of dissolved organic carbon and total organic matter by 20.53 % and 25.37 %, respectively, which led to a higher content of humic substances (141.81 mg/g) and a higher degree of polymerization (3.51) in SW4. Among all, the dissolved organic carbon in the compost substrate of SW4 treatment showed the highest level of aromatization and more refractory organic matter decomposition. The compact microbial co-occurrence network analysis exhibited the high-metabolic activity in Fenton-like treatment (SW4). Therefore, the probable mechanism of humification facilitation by Fenton-like reagent amendment in co-composting could be controlled by several processes: 1) generation of ·OH for facilitating the decomposition of organic matter, 2) disintegration of refractory lignocellulose substances by promoting the lignin pathway of humification, and 3) increasing the quantity and activity of microbes (i.e., Proteobacteria, Actinobacteriota, Chloroflexi, Ascomycota and Basidiomycota) involved in humification. This study provided a profound understanding of Fenton-like reagent amendments in co-composting of agricultural solid wastes and proposes a solution for enhancing the humification degree of compost products for agricultural use. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg-modified biochar exhibited a high P adsorption capacity (∼248 mg g−1). • Goethite was more effective than hematite in reducing P transport in columns. • Coexistence of biochar and goethite increased available retention sites of P. • Citric acid and oxalic acid achieved release of P retained in columns. The practical effects of biochar on soil phosphate (P) transport are significantly affected by P adsorption capacity of biochar itself and its interaction process with iron oxides. Here, the ability of pyrolysis to shape P adsorption capacity of biochar was investigated, while the interaction of biochar and iron oxides on P transport was explored with quartz sand columns and numerical modeling. Adsorption experiments showed that pyrolysis increased P adsorption capacity of Mg-modified biochar (∼248 mg g−1) through enriching surface morphology and pore structures, optimizing composition of functional groups, and forming MgO crystals. It also caused that P adsorption at MgBC-700°C was mainly controlled by surface precipitation, electrostatic attraction and pore interception. Simultaneously, the desorption of P was sensitive to pH changes and with low-stability. Transport experiments showed that iron oxides reduced P transport, shown to be goethite > hematite (P leaching: 69.59 % vs 98.29 %). Further, MgBC-700°C continued to decrease P transport from 75.56 % to 31.50 %, and the effect of goethite was more effective, with ligand reaction playing an important role. This process was influenced by cation types (Ca2+ and K+), ionic strength (1 mM and 50 mM), and pH (5, 7 and 9) through changing available retention sites of columns. Furthermore, since P adsorption mechanisms were different in the presence of MgBC-700°C and goethite than MgBC-700°C only, the changes of pH could no longer cause the release of P, but surprisingly, citric acid and oxalic acid could activate and slowly release the retained P via chelation, ligand exchange, and solubilization, which suggested that MgBC-700°C, as an environmentally-friendly P adsorption and release material, has great potential in reducing P loss and facilitating P utilization. [ABSTRACT FROM AUTHOR]

The successful upscaling of anaerobic fermentation (AF) still relies on ensuring the stable production of volatile fatty acids (VFAs) in high concentrations and yields. The unforeseen events taking place at industrial scale can compromise the AF stability, thereby decreasing the cost-effectiveness of the process. To assess process stability against disturbances and identify AF failure indicators, this investigation explored the effect of starvation and pH control failure in a continuous reactor. The starvation disturbance did not affect AF performance and methanogenesis was not restored, confirming the relevance of selecting proper conditions (25 °C and pH 6.5) to ensure methanogenesis suppression. By contrast, the uncontrolled pH provoked a pH drop to 4.5, limiting the acidogenesis metabolisms and modifying the metabolites profile due to microbiome reshape. Lactobacillus , and members of Lactobacillaceae, Lactobacillales, and Bifidobacteriaceae dominated the microbiome in the pH disturbance, revealing lactic, succinic and oxalic acids as warning indicators of the acidogenesis failure. Nevertheless, the AF was completely recovered after the disturbances evidencing the microbiome robustness against pH range between 4.5 and 5. • 25 °C and pH 6.5 suppressed methanogenic activity at long hydraulic retention time. • Starvation period shorter than hydraulic retention time did not alter process yield. • pH drop limited acidogenesis while hydrolysis remained highly efficient. • Lactic, succinic and oxalic acids indicated the level of process damage. • Metabolic plasticity enabled microbiota recovery after disturbances. [ABSTRACT FROM AUTHOR]

Iridium (Ir) has some unique excellent properties and many special applications in high-tech fields. Herein, Ir and Ir Ni films were electrodeposited on copper substrates from aqueous solutions containing Ir3+, [Ir(III)Br 6 ]3− or [Ir(IV)Br 6 ]2−. The electrochemical behaviors of the electrolytes were studied. The surface morphology, phase and chemical composition of the selected films were investigated by SEM, TEM, XRD, XPS and EDS, respectively. The composition of Ir Ni film was regulated by bath components. Ir and Ir-rich Ir Ni films were deposited electrochemically from hexabromoiridate solutions. Although the quality of Ir film from IrCl 3 solution was poor, Ni-rich Ir Ni films obtained from IrCl 3 solution exhibited good quality and good adhesion. The deposition rate, crystallinity and appearance quality of the films were improved in oxalic acid solutions. Under the same deposition conditions, Ir Ni deposits from [Ir(III)Br 6 ]3- electrolyte had similar composition to the films from [Ir(IV)Br 6 ]2- electrolyte, while the deposition rate and efficiency tended to be high in [Ir(III)Br 6 ]3- electrolyte. The top-surface of the film was composed of Ir oxide and metallic Ir, or Ni and Ni oxide. However, the depth composition in the film mainly consisted of metallic Ir and Ni. The selected Ir-0–90 at.% Ni films consisted of nanocrystalline and amorphous phases. The hardness and elastic modulus of the films decreased with the decrease in Ir-content. The mechanical properties of Ni-rich Ir Ni alloys from citrate solutions are higher than those of Ir-rich Ir Ni deposit from oxalic acid solutions. The films from acid electrolytes with a low pH value had poor interfaces, resulting in poor adhesion. However, the adhesion force of Ni-rich Ir Ni alloys from citrate solutions was up to 35 - 45 N. • Ir films were electrodeposited from aqueous solutions with three kinds of Ir salts. • Ir-rich and Ni-rich Ir-Ni alloy films were plated from different solution systems. • Microstructure, phase and composition of Ir and Ir-Ni films were characterized. • Hardness and modulus of the film decreased with the decrease in Ir-content. • Adhesion force of Ni-rich Ir-Ni deposit from citrate solution was 35–45 N. [ABSTRACT FROM AUTHOR]

• DFT methods were used to find the most stable structure of the DESs composed of ChCl/carboxylic acids. • All 1:1 and 1:2 ChCl/carboxylic DESs were found be stable due to the negative formation energies. • The Cl H(O) Lewis acid-base interaction between ChCl and CA is stronger than the hydrogen bonding. • The ChCl/oxalic acid DES was found to be the most beneficial as a co-solvent in pharmaceutical and chemical industries. Deep eutectic solvents (DES) have received substantial applications and development in the field of green chemistry during the last decade. Using computational density functional theory (DFT), DESs composed of Choline Chloride (ChCl), as the hydrogen bond acceptor (HBA), and six carboxylic acids (CA) including Glycolic acid (Gly), Glutaric acid (Glu), Oxalic acid (Oxa), Lactic acid (La), Itaconic acid (Ita), and Levulinic acid (Lev), as the hydrogen bond donner (HBD), were investigated. Geometry optimization and vibrational frequency assignment were performed by applying three DFT functionals, i.e., B3LYP-D3(BJ), M06-2X, and ωB97XD in combination with Pople's 6-311+g(d,p) basis set. Then, using of the QTAIM, NBO, and the NCI analyses, different sorts of interactions have been evaluated to indicate the most stable structure between ChCl and various CAs, and the hydrogen bonding in the studied DESs. The results confirm that the Cl ion in choline chloride created a strong hydrogen-bond with HBDs, and the mixed ionic-covalent interaction is the main interaction in construction of the DESs of ChCl with the studied carboxylic acids. [ABSTRACT FROM AUTHOR]

• ChCl-oxalic acid was the effective extraction medium for antioxidant bioactive compounds. • DES extracts showed a plasticizing effect in the film. • The use of DESs and DES extracts induced structural change in the films. • The addition of DES extracts improved the antioxidant activities of chitosan film, especially ChCl-lactic acid extract. Natural polymers are the most promising alternatives to petroleum-based plastics for developing biodegradable food packaging films. However, the brittleness and lack of active protection of films from most natural polymers pose a challenge to their practical application. The addition of plasticizers and natural extracts to these films is considered an effective solution to address these issues. In this study, the potential for the use of deep eutectic solvents (DESs) and DES extracts derived from Hibiscus sabdariffa in the production of chitosan films and their effects on their mechanical and antioxidant properties were examined. Initially, the extraction efficacy of DESs composed of choline chloride (ChCl) and various carboxylic acids (citric, lactic, tartaric, and oxalic acids) was evaluated in terms of phenolic and anthocyanin contents along with antioxidant activities. Optimal results were achieved with the utilization of ChCl-oxalic acid as the extraction medium. Subsequently, chitosan films were fabricated by introducing DESs and DES extracts as plasticizers and compared with glycerol-plasticized chitosan films. The incorporation of DESs and DES extracts into the film matrix led to a notable reduction (11.78–14.82%) in moisture content compared with glycerol (25.34%). Notably, using ChCl-tartaric acid improved the tensile strength, while ChCl-citric acid enhanced the film flexibility. Films containing ChCl-tartaric acid demonstrated exceptional light barrier properties. SEM analysis revealed an interaction between chitosan and DESs, which was further corroborated by FTIR and XRD. Additionally, DES extracts provided superior antioxidant activity to the films than their pure DESs. These findings suggest a significant potential for DES extracts from Hibiscus sabdariffa as bioactive agents and plasticizers in chitosan films. [ABSTRACT FROM AUTHOR]