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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]

Citrate-modified biochar nanoparticles (CBCNPs) represent a promising amendment with plant-available silicon (PASi) releasing capacity. However, the co-transport behavior with released PASi remain poorly understood. This study investigated their co-transport in saturated porous media under various solution chemistry and low molecular weight organic acids (LMWOAs). Experimental and two-site kinetic model results revealed that higher ionic strength caused favorable aggregation and size-selective, hindering CBCNPs transport. Divalent Ca2+ ions retained CBCNPs more effectively than K+ due to stronger charge screening and cation bridging. The pH buffering capacity of CBCNPs resulted in consistent transport behavior across a broad pH range (4–8). XDLVO calculation clarified the impact mechanisms of IS, ion types and pH on CBCNPs transport. Furthermore, LMWOAs exhibited a time-dependent blocking effect on CBCNPs transport. Oxalic acid (OA) and citric acid (CA) facilitated CBCNPs transport though mechanisms beyond XDLVO, including steric hindrance, competitive adsorption, and surface hydrophilicity. The presence of LMWOAs significantly hindered PASi co-transport, with the inhibitory effect ranked as acetic acid (AA) ≈ CA > OA > absence of organic acids. The inhibition is attributed to the blocking effect and formation of Si-organic acid complexes, as evidenced by breakthrough curves and density functional theory calculations. This study provides novel insights into the co-transport of CBCNPs with released PASi through mutual mechanisms, indicating both potential environmental benefits and risks. [Display omitted] • CBCNPs retention enhanced with increasing ionic strength and ion value. • PH-buffering capacity of CBCNPs ensures consistent transport across pH 4–8 range. • CA, OA enhance CBCNPs transport with the impact of non-XDLVO interactions. • Organic acids inhibit PASi co-transport with the order of AA ≈ CA > OA. • Organic acids hinder PASi transport through blocking effect and complexation. [ABSTRACT FROM AUTHOR]

The shift towards a circular economy, where waste generation is minimized through waste re-use and the development of valorization strategies, is crucial for the establishment of a low carbon, sustainable, and resource-efficient economy. However, there is a lack of strategies for re-using and valorizing specific types of waste, particularly those containing naturally occurring radioactive materials (NORM), despite the prevalence of industrial activities that produce such waste due to their chemical and radiological hazards. Living organisms, including fungi, are valuable sources of bioactive compounds with various industrial applications. In this study, we assessed the growth and metabolic profile changes of three white rot fungi species in response to low concentrations of a uranium mine effluent containing NORM and metals to explore their potential for producing biotechnologically relevant bioactive compounds. The growth rate was assessed in three different culture media, with and without the uranium mine effluent (1% V/V)), and the metabolic profile was analyzed using FTIR-ATR spectroscopy. Results suggested an improvement in growth rates in media containing the uranium mine effluent, although not statistically significant. T. versicolor showed promise in terms of bioactive compound production. The production of droplets during growth experiments and significant metabolic changes, associated with the production of bioactive compounds like laccase, melanin, and oxalic acid, were observed in T. versicolor grown in mYEPDA with the uranium mine effluent. These findings present new research opportunities for utilizing waste to enhance the biotechnological production of industrially relevant bioactive compounds and promote the development of circular economy strategies for re-using and valorizing NORM-containing waste. [Display omitted] • FTIR-ATR spectroscopy revealed enhanced bioactive compound production. • Notable differences between the fungal species and the growth media tested. • Potential increase in laccase, oxalic acid and melanin production by T. versicolor. • Small volumes of U mine effluent needed to apparently increase production. • Fungal bioactive compounds production as solution for mine waste valorization. [ABSTRACT FROM AUTHOR]

Solid-liquid extraction was investigated to obtain selected major plant nutrients (P, K, Ca, Mg) from biofuel ash using weak organic acids like salicylic acid, citric acid, and oxalic acid as sacrificial leaching agents. In this study, three organic acids were compared to determine the most effective leaching agent for maximizing the P, K, Ca, and Mg extraction from biofuel ash. The findings indicated that 0.1 M citric acid was the most efficient for plant nutrient recovery, with 81.9% of P recovered after 30 min, 82.4% of Ca, 76.8% of Mg, and 47.3% of K. after 120 min. The highest amount of K, with 59.3% was recovered after 180 min of extraction with 0.1 M oxalic acid. However, recovery of P–80.7% was lower, and much lower recovery of Ca–2.3%, and Mg–68.6% after 180 min of extraction with 0.1 M oxalic acid. The leachates were not contaminated with heavy metals, just 0.47 mg/L of Zn, 7.67 mg/L of Al, and 1.99 mg/L of Fe were detected after 180 min of extraction with 0.1 M oxalic acid. The formation of calcium oxalates after extraction with 0.1 M oxalic acid was seen by SEM-EDS. The findings indicated that to achieve the highest recovery of all beneficial nutrients (P, K, Ca, Mg) different extraction times and different extraction agents are required. [Display omitted] • 0.1 M citric acid showed the best recovery of beneficial nutrients from ash. • 0.1 M citric acid can recover more than 80% of P and Ca from biofuel ash. • Amounts of leached heavy metals to filtrate were lower that limits of detection. [ABSTRACT FROM AUTHOR]

V–Ti magnetite tailings (VTMTs) contain various heavy metals, such as Fe, Mn, V, Co, and Ni. The groundwater pollution caused by the tailing metal release has become a local environmental concern. Although studies have demonstrated the influence of alternate flooding and drying cycles (FDCs) on metal form and mobility in minerals, little was known about whether FDCs affect the metal release of VTMTs and the transformation of released metals. This study investigated the metal release kinetics of VTMTs and the metal transformation under FDCs in the absence and presence of acid rain (sulfuric and nitric acids) and bio-secreted organic acids (acetic, oxalic, and citric acids). The results showed that FDCs promoted metal release whether or not acids were present. The maximum released concentrations of V, Mn, Fe, Co, and Ni were as high as 78.63 mg L−1,1.47 mg L−1, 67.96 μg L−1, 1.34 mg L−1, and 0.80 mg L−1, respectively, under FDCs and citric acids. FDCs enhanced the tailing metal release by increasing the metal labile fraction proportion. However, the concentrations of released Fe, Mn, V, Co, and Ni all gradually decreased due to their (co-)precipitation. These precipitates conversely inhibited the subsequent mineral dissolution by covering the tailing surface. FDCs also enhanced the tailings' porosities by 2.94%–9.94%. The mineral dissolution, expansion and shrinkage, and changes in tension destroyed the tailing microstructure during FDCs. This study demonstrated the low metal pollution risk of VTMTs under FDCs, either in acid rain or bio-secreted organic acids. However, the increase in tailing porosity should be seriously considered as it would affect the tailing pond safety. [Display omitted] • The metal release depended on proton/ligand-promoted and reductive dissolution. • The promotion on metal release followed: citric acid > acetic acid > oxalic acid. • Citric acid provided a reducing environment for the reductive dissolution of Fe/Mn. • Flooding and drying cycles enhanced the tailing porosity and anoxic-aerobic cycles. • V–Ti magnetite tailings produced ·OH during flooding and drying cycles. [ABSTRACT FROM AUTHOR]

Extracellular polymeric substance (EPS) with highly hydrophilic groups and sludge with high compressibility are determined sludge dewaterability. Herein, Fe2+ catalyzed calcium peroxide (CaO 2) assisted by oxalic acid (OA) Fenton-like process combined with coal slime was applied to improve sludge dewaterability. Results demonstrated that the sludge treated by 0.45/1/1.1-OA/Fe2+/CaO 2 mM/g DS, the water content (W C), specific resistance to filtration and capillary suction time dropped to 53.01%, 24.3 s and 1.2 × 1012 m/kg, respectively. Under coal slime ratio as 0.6, W C and compressibility were further reduced to 42.72% and 0.66, respectively. The hydroxyl radicals generated by OA/Fe2+/CaO 2 under near-neutral pH layer by layer collapsed EPS, resulting in the degradation and migration of inner releasing components and the exposure of inner sludge flocs skeleton. The hydrophilic tryptophan-like protein of TB-EPS were degraded into aromatic protein of S-EPS and exposed inner hydrophobic sites. The protein secondary structures were transformed by destroying hydrophilic functional groups, which were attributed to the reducing α-helix ratio and reconstructing β-sheet. Moreover, coal slime as the skeleton builder lowered compressibility and formed more macropores to increase the filterability of pre-oxidized sludge for the higher intensity of rigid substances. This study deepened the understanding of OA enhanced Fenton-like system effects on sludge dewaterability and proposed a cost-effective and synergistic waste treatment strategy in sludge dewatering. [Display omitted] • OA/Fe2+/CaO 2 composite coal slime is effective for sludge deep dewatering. • Layer by layer degradation for EPS was verified in OA/Fe2+/CaO 2 system. • Proteins and polysaccharides concentrated in TB-EPS migrated to outer layer. • OA/Fe2+/CaO 2 more seriously degraded inner hydrophilic EPS than Fe2+/CaO 2. • The role of coal slime in enhancing Fenton-like pretreated sludge filtration was cleared. [ABSTRACT FROM AUTHOR]

Complex rhizoremediation is the main mechanism of phytoremediation in organic-contaminated soil. Low molecular weight organic acids (LMWOAs) in root exudates have been shown to increase the bioavailability of contaminants and are essential for promoting the dissipation of contaminants. The effects of root exudates on the dissipation of organophosphate esters (OPEs) in soil are unclear. Consequently, we studied the combined effects of root exudates, soil enzymes and microorganisms on OPEs (tri (1-chloro-2-propyl) phosphate (TCPP) and triphenyl phosphate (TPP)) dissipation through pot experiments. Oxalic acid (OA) was confirmed to be the main component of LMWOAs in root exudates of ryegrass. The existence of OA increased the dissipation rate of OPEs by 6.04%–25.50%. Catalase and dehydrogenase activities were firstly activated and then inhibited in soil. While, urease activity was activated and alkaline phosphatase activity was inhibited during the exposure period. More bacteria enrichment (e.g., Sphingomonas , Pseudomonas , Flavisolibacter , Pontibacter , Methylophilus and Massilia) improved the biodegradation of OPEs. In addition, the transformation paths of OPEs hydrolysis and methylation under the action of root exudates were observed. This study provided theoretical insights into reducing the pollution risk of OPEs in the soil. [Display omitted] • Oxalic acid was the main component of ryegrass root exudates. • OPEs stress enhanced the secretion of oxalic acid. • The root exudates of ryegrass promoted the degradation of OPEs in soil. • Microbial communities were significantly affected by root exudates. [ABSTRACT FROM AUTHOR]

Sea-salt aerosols (SSA) are one of the key natural aerosols in our atmosphere, consisting predominantly of sodium chloride (NaCl). Throughout their atmospheric transport, these aerosols undergo complex internal mixing, giving rise to a rich variety of inorganic and organic species, including dicarboxylic acids. This study investigates firstly the composition and deliquescence properties of coarse particles containing pure malonic acid (MA 2 , CH 2 (COOH) 2) and internally mixed NaCl and MA 2 , by means of an acoustic levitation system coupled with a Raman microspectrometer. Secondly, we report here the first experimental observation and characterization of the products arising from photochemical reactions under UV–Visible irradiation (338 ≤ λ ≤ 414 nm) in the absence of an oxidant under acoustic levitation conditions in MA 2 and NaCl/MA 2 aerosols. Furthermore, the impact of photodegradation on the hygroscopic properties of these particles is examined. We confirmed the irreversible formation of monosodium malonate (NaMA, HOOCCH 2 COONa), which coexists with NaCl or MA 2 on non-irradiated particles. We also demonstrated the formation of oxalic acid (OA 2 , HOOC–COOH) within irradiated MA 2 droplets and the appearance of glyoxylic acid (GlyA, HCOCOOH) in NaCl containing droplets. The photolysis process exerts a marked effect on the hygroscopic properties of the particles, resulting in a shift in deliquescence transitions toward higher relative humidity (RH) values. This study contributes to the understanding of the intricate physicochemical processes involved in SSA during their atmospheric transport. Likewise, this work sheds light on the impacts of these types of aerosols on cloud formation and climate change. [Display omitted] • Individual-levitated malonic acid droplets photolyzed in the absence of oxidants. • NaCl modified the photochemical reactivity of microdroplets of aqueous malonic acid. • Photolysis of malonic acid droplets produced oxalic acid or glyoxylic acid. • Photoreactivity altered deliquescence behavior and reduced hygroscopic growth. [ABSTRACT FROM AUTHOR]

Chemically mediated recovery of phosphorous (P) as vivianite from the sludges generated by chemical phosphorus removal (CPR) is a potential means of enhancing sustainability of wastewater treatment. This study marks an initial attempt to explore direct P release and recovery from lab synthetic Fe–P sludge via reductive dissolution using ascorbic acid (AA) under acidic conditions. The effects of AA/Fe molar ratio, age of Fe–P sludge and pH were examined to find the optimum conditions for Fe–P reductive solubilization and vivianite precipitation. The performance of the reductive, chelating, and acidic effects of AA toward Fe–P sludge were evaluated by comparison with hydroxylamine (reducing agent), oxalic acid (chelating agent), and inorganic acids (pH effect) including HNO 3 , HCl, and H 2 SO 4. Full solubilization of Fe–P sludge and reduction of Fe 3 + were observed at pH values 3 and 4 for two Fe/AA molar ratios of 1:2 and 1:4. Sludge age (up to 11 days) did not affect the reductive solubilization of Fe–P with AA addition. The reductive dissolution of Fe–P sludge with hydroxylamine was negligible, while both P (95 ± 2%) and Fe 3 + (90 ± 1%) were solubilized through non-reductive dissolution by oxalic acid treatment at an Fe/oxalic acid molar ratio 1:2 and a pH 3. With sludge treatment with inorganic acids at pH 3, P and Fe release was very low (<10%) compared to AA and oxalic acid treatment. After full solubilization of Fe–P sludge by AA treatment at pH 3 it was possible to recover the phosphorus and iron as vivianite by simple pH adjustment to pH 7; P and Fe recoveries of 88 ± 2% and 90 ± 1% respectively were achieved in this manner. XRD analysis, Fe/P molar ratio measurements, and magnetic attraction confirmed vivianite formation. PHREEQC modeling showed a reasonable agreement with the measured release of P and Fe from Fe–P sludge and vivianite formation. [Display omitted] • The reductive dissolution of ascorbic acid (AA) on Fe–P sludge was effective. • Oxalic acid effectively solubilized Fe–P sludge and chelated Fe at oxic conditions. • The chelating effect of oxalic acid to Fe was stronger than ascorbic acid. • The reductive dissolution of Fe–P sludge with hydroxylamine was negligible. • It was possible to recover P and Fe as vivianite by AA treatment when pH raised to 7. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resins (UPR) are composed of prepolymers and styrene diluents, while the former are produced by co-polycondensation between diol, unsaturated diacid and saturated diacid. In this work, bio-based UPR prepolymers were synthesized from bio-based oxalic acid, itaconic acid, and ethylene glycol, which were then diluted with bio-based isosorbide methacrylate (MI). Meanwhile, the phenylphosphonate were introduced into the molecular chains of prepolymers to achieve intrinsic flame retardancy of bio-based UPR. The potential of the reactive MI diluents as substitutes of volatile styrene, was also assessed through the volatility test, curing kinetics and gel contents analysis. For UPR materials with styrene diluents, the UPR materials can achieve UL-94 V0 level and the 28% of limiting oxygen index (LOI) with 2.63 wt% of phosphorus contents. By contrast, the UPR materials with MI diluents can reach UL-94 V0 level with only 2.14 wt% of phosphorus contents. As the phosphorus contents were further increased to 2.63 wt%, UPR materials can achieve highest 29%, while the peak of heat release rate (PHRR) and total heat release (THR) were decreased by 68.01% and 48.62%, respectively. The Flame Retardancy Index (FRI) was also used to comprehensively evaluate the flame retardant performance of UPR composites. Compared with neat UPR, the composites with MI diluents and phosphorus containing structures increased from 1.00 to 6.46. The mechanism for improved flame retardancy was analyzed from gaseous and condensed phase. Additionally, the tensile strengths of bio-based UPR materials with styrene and MI diluents were studied. This work provides an effective method to prepared high-performance and fully bio-based UPR materials with improved flame retardant properties and safety application of reactive diluents. [Display omitted] • Fully bio-based and intrinsically flame retardant UPR was synthesized. • Bio-based MI diluents can effectively replace toxic and volatile styrene VOC. • Fully bio-based UPR achieved UL-94 V0 with only 2.14 wt% of phosphorus. • Fully bio-based UPR exhibits promising comprehensive application prospects. [ABSTRACT FROM AUTHOR]

This study aims to explore the reusability of wastewater treatment by-product for photo-Fenton process to treat an organic pollutant model. The optimal condition, reactive oxygen species (ROS), and kinetic approach in photo-Fenton process was discussed. The Metal oxide crystal pellets from are a by-product of the Fluidized-Bed Crystallization (FBC) process and can be used as a catalyst in the Photo-Fenton process. Electroplating wastewater containing iron and copper was treated via the FBC process using granulated Al(OH) 3 as carrier seeds. The binary oxide of FeOOH and Cu 2 O on the Al(OH) 3 surface (Fe 0.66 Cu 0.33 @Al(OH) 3) was identified as the FBC by-product after characterization using FTIR and XPS analysis. In the photo-Fenton process, visible light from a fluorescence lamp with a wavelength of 400–610 nm was chosen as an irradiation source. Oxalic acid was added as chelating agent to form photosensitive iron oxalate species and hydrogen peroxide was applied as oxidant to generate active radical to decolorize and mineralize RB5 synthesized solution (100 mg/L). The operating conditions including the oxalic acid to pollutant ratio ([OA] 0 /[RB5] 0) of 4.5–13.0, reaction pH (pHr) of 3–7 and initial to theoretical hydrogen peroxide molar ratio [H 2 O 2 ] 0 /[ H 2 O 2 ] theoretical of 35%–120% were optimized. Under the optimal conditions, pH r = 5.0; [H 2 O 2 ] 0 /[RB5] 0 at 75% stoichiometric and [OA] 0 /[RB5] 0 = 9, the RB5 is almost completely decolorized after 210 min of operation and the mineralization efficiency is 58%. The contribution of •OH, O 2 •-, and O 2 1 to the Photo-Fenton system was determined using ESR analysis with the addition of DMPO and TEMP as spin trap agents. The kinetic analysis reveals the observed rate constants k RB5 , k OA and k R from fitting are 0.0120, 0.0054 and 0.0001 M−1s−1, respectively. [Display omitted] • The binary oxide of by-product from FBC process is useful for organics treatment. • Treatability of azo dye RB5 by visible light-assisted photo-Fenton was investigated. • RB5 was completely degraded and mineralized of 55% using a 75% stoichiometric dosage of H 2 O 2 with the addition of oxalic acid at pH 5. • Up to 55% of TOC was mineralized mainly by O 2 •- and O 2 1. • Rate modeling of RB5 and TOC removal were explained using consecutive kinetics. [ABSTRACT FROM AUTHOR]

Tricresyl phosphates (TCPs), a typical sort of organophosphate flame retardants, has received extensive concerns due to its potential adverse effects. However, limited information is available on the efficient and safe removal methods of TCPs. In this regard, TCPs were tentatively biodegraded with Brevibacillus brevis. A probable degradation pathway was further proposed with the cellular reactions discussed in detail. Experiments showed that B. brevis at 2 g L−1 could degrade 1 mg L−1 tri-m-cresyl phosphate, tri-p-cresyl phosphate, and tri-o-cresyl phosphate by 82.91%, 93.91%, and 53.92%, respectively, within five days. In the process of biodegradation, B. brevis metabolism caused the release of Na+ and Cl− as well as the absorption of some nutrient ions including K+, PO 4 3−, Mg2+, and SO 4 2−; the presence of oxalic acid, citric acid, acetic acid, and malonic acid was also detected. Similar metabolic pathways were found among different TCPs isomers, but tri-o-cresyl phosphate induced more reactive oxygen species than the other two did. This work develops novel insights into the potential mechanisms of TCPs biodegradation by microorganisms. Image 1 • B. brevis could degrade TpCP and TmCP more effectively than ToCP. • Biodegradation pathways were speculated based on the metabolites of TCP isomers. • Organic acids produced by B. brevis were detected during the degradation process. • TCP isomers induced oxidative stress on B. brevis. [ABSTRACT FROM AUTHOR]

The main aim of this study is to investigate the biodegradation of highly concentrated aspirin as an emerging pollutant from aqueous solution using an alternating current microbial electrochemical system. A single-chamber Plexiglas cylindrical reactor equipped with stainless steel mesh electrodes (18 cm height × 16 cm diameter) was applied as the bioreactor in batch mode with an effective volume of 5 L, height of 20 cm, and the diameter about 20 cm by AMPL = 2 V pp , OFST = 0.1 V, waveform = sinusoidal, frequency = 10 Hz, and pH = 7. The process parameters including initial concentration (100–400 mg L-1), chemical oxygen demand (COD), activity of enzymes, biokinetic and pathway studies at very low voltage and very low frequency alternating current were investigated. The specific biodegradation rate of aspirin was calculated based on Michaelis–Menten model. The complete aspirin removal efficiency and the maximum enzymatic activity were achieved at 250 mg L-1 aspirin, voltage of 2 V pp and applied current = 3 mA during 6 h. The bioassay of aspirin concentrations in biofilm of the system using flow cytometry analysis resulted in the live and necrotic cells shares of 96.2%, and 0.44%, respectively. Moreover, the LC and GC-MS analysis showed low molecular weight acids such as oxalic and acetic acid at 6 h time under the optimal conditions using very low applied voltage and frequency. Obtaining low reaction time for degradation, high potential in biodegradation, oxidation and mineralization ability were the novelty of treatment system with high concentration aspirin in the study. Image 109877 • A new approach for emerging pollutant treatment. • Microbial electrochemical system supplied by alternating current was utilized. • Metabolic activity and pathway of aspirin biodegradation have presented. • The specific biodegradation rate of aspirin was determined. • The bioassay of aspirin presented by flow cytometry analysis. [ABSTRACT FROM AUTHOR]

Self-doped TiO 2 nanotube arrays (DNTA) were prepared for the electrooxidation of resistant organics. The anatase TiO 2 NTAs had an improved carrier density and conductivity from Ti3+ doping, and the oxygen-evolution potential remained at a high value of 2.48 V versus the standard hydrogen electrode, and thus, achieved a highly enhanced removal efficiency of phenol. The second anodization could stabilize Ti3+ and improve the performance by removing surface TiO 2 particles. Improper preparation parameters (i.e., a short anodization time, a high calcination temperature and cathodization current density) harmed the electrooxidation activity. Although boron-doped diamond (BDD) anodes performed best in removing phenol, DNTA exhibited a higher mineralization of phenol than Pt/Ti and BDD at 120 min because intermediates were oxidized once they are produced with DNTA. Mechanism investigations using reagents such as tert-butanol, oxalic acid, terephthalic acid, and coumarin showed that the DNTA mineralization resulted mainly from surface-bound OH, and the DNTA produced more than twice the amount of OH compared with BDD. The free OH on the BDD electrode was more conducive to initial substrate oxidation, whereas the adsorbed OH on the DNTA electrode mineralized the organics in situ. The preferential removal of p -substituted phenols on DNTA was attributed mainly to their electromigration and the aromatic intermediates that are hydrophobic were beneficial to mineralization. Image 1 • The DNTA showed excellent oxidation efficiency by dopping appropriate Ti3+. • DNTA exhibited lower removal but higher mineralization efficiency for phenol than BDD. • Surface-bound.•OH was a dominant mechanism for the mineralization. • The electrooxidation efficiencies of different p-substituted phenols were investigated. [ABSTRACT FROM AUTHOR]

Abstract In order to understand the spatial distribution characteristics, loss risk and leaching behaviors of phosphorous from exposed rocks in typical small-area of Chaohu watershed, phosphorus-rich rock was selected for conducting a series of column leaching experiments to investigate the phosphorus leaching. By simulating the intermittent cycle of acid rainfall, effects of oxalic acid on the weathering of phosphate rocks were studied. Total phosphorus contents, pH and phosphate leaching capacity from phosphorus rocks were tested in the presence of oxalic acid at different dry-wet intervals. The results indicated that the cumulative release of phosphorus increased first and then decreased with the duration of dry-wet intervals increasing. Four typical kinetic equations can describe phosphorus release from phosphate rocks with the action of oxalic acid. The best fitting models were the weight function and parabolic equation, with a mean correlation coefficient R2 of 0.9727 and 0.9941, respectively, which reached significance level. Total phosphorus (TP) leaching distribution in each column showed a tendency of gradually decreasing from top to bottom except for time interval of 5 d and 7 d. Occluded-bound P (Oc-P) is the dominant form in rocks. The change point value of rocks phosphorus is 4.11 mg kg−1 after intermittent leaching, and the phosphorus loss risk is relatively large in some rocks formations. Highlights • A series of column leaching experiments were conducted for simulating acid rainfall at different time intervals. • Characterization of the leachate variations in phosphate rocks with action of oxalic acid was studied. • The cumulative release of phosphorus at different time intervals was investigated. • Phosphorus leaching critical value was evaluated. [ABSTRACT FROM AUTHOR]

Abstract Oxalic acid potentially enhances pump-and-treat for groundwater As remediation by accelerating mobilization. This study examines how oxalic acid mobilizes As from Fe(III)-oxide coated sand under hydrodynamic conditions. Four columns were packed with metal-substituted ferrihydrite or goethite to 1% Fe, presorbed to 50% As surface coverage, and reacted with pH = 2.2 artificial groundwater amended with 10 mM oxalic acid at 1 m day−1. Arsenic elution was affected by both As and Fe speciation. Although the As(V) columns experienced faster substrate dissolution, As(V) elution was delayed by re-adsorption, whereas As(III) elution was rapid due to pH decrease that prevented re-adsorption. Cr-ferrihydrite and Ni-goethite dissolved both effectively initially but then diverged. The Cr-ferrihydrite columns experienced continuous stoichiometric Fe and Cr release, and As release could be sustained. The Ni-goethite columns initially experienced nonstoichiometric Fe and Ni release, and As release was extensive. Such release, however, was not sustained. We hypothesized that Ni-goethite contained sites with distinct reactivity, and oxalic acid targeted readily-dissolved, sorption-dense sites. Our data indicate that oxalic acid-enhanced pump-and-treat methods would be easier to apply to aquifers dominated by As(III), requiring less amendment to be injected; such oxalic acid-enhanced methods remove reactive sediment Fe and As, potentially preventing future groundwater contamination. Graphical abstract Image 1 Highlights • We study oxalic acid promoted metal release from As presorbed Fe oxide coated sand. • Cr and Ni substituted ferrihydrite and goethite were used. • The effect of substrate dissolution was isolated from other As release mechanisms. • As(V) elution was retarded, whereas As(III) elution was rapid due to pH decrease. • Unlike Cr-ferrihydrite, metal release from Ni-goethite could not be sustained. [ABSTRACT FROM AUTHOR]

The design and development of adsorbents with high efficiency, selectivity, and economy for Pb(II) are essential to environmental governance and ecological safety. Herein, an oxalic acid (OA) activated natural sepiolite (nSEP) composite for highly efficient Pb(II) removal was prepared by a facile impregnation strategy. The OA activated nSEP nanocomposite (OA-nSEP) was characterized by various instrumental techniques and its adsorption performance towards Pb(II) was further evaluated through a series of static and dynamic experiments under various environmental conditions. Results revealed that OA reacted with the calcium impurities in nSEP to form calcium oxalate, causing mesoporous structure and larger specific surface area of OA-nSEP. The obtained OA-nSEP possessed super high Pb(II) adsorption capacities (858.4–1252 mg/g), which were much higher than that of most modified clays or conventional materials. The average adsorption site energy and the standard deviation of the site energy distribution were analyzed to investigate the strength of Pb(II) binding onto OA-nSEP and the adsorption site heterogeneity. Mechanism studies confirmed that oxalate groups exerted a primary role in the adsorption process. X-ray diffraction and X-ray photoelectron spectrometry (XPS) unveiled that the coordination of oxalate with Pb(II) and precipitation of lead oxalate was responsible for the high efficiency and selectivity. Distinguishing feature of high adsorption capacity, specific selective adsorption, abundant availability, and splendid reusability make the OA-nSEP a promising candidate for eliminating Pb(II) in practical scenarios. [Display omitted] • The OA activated nSEP composite was firstly prepared for aqueous Pb(II) removal. • Highly efficient Pb(II) removal was mainly attributed to the formation of PbC 2 O 4. • Site energy distribution of the adsorption system was analyzed. • Pb(II) adsorption mechanisms and the influencing factors were examined. • OA-nSEP had great potential for the treatment of lead-containing wastewater. [ABSTRACT FROM AUTHOR]

The degradation of asulam herbicide by photo electro-Fenton (PEF) and solar photo electro-Fenton (SPEF) processes was studied using an undivided electrochemical BDD/carbon-felt cell to generate H 2 O 2 continuously. A central composite design combined with response surface methodology was applied to determine the optimal operating conditions of current intensity = 0.30 A, [Fe2+] = 0.3 mM, and [Na 2 SO 4 ] = 0.11 M at pH 3 to achieve the complete degradation of asulam by electro-Fenton. Subsequently, the SPEF process was more efficient treatment compared to PEF, achieving a complete degradation of asulam and 98% of mineralization in 180 min. Moreover, 4-aminobenzenesulfonamide, 4-aminophenol, and 4-benzoquinone were detected as aromatic intermediates, whereas acetic acid, oxalic acid, and NO 3 − ions were identified as final degradation by-products. Thus, the SPEF process is an efficient alternative for the complete degradation and mineralization of herbicide asulam in an aqueous solution under natural sunlight. [Display omitted] • Asulam was completely degraded by using PEF and SPEF processes. • Natural sunlight irradiation contributes to enhancing.●OH production. • SPEF was the most efficient process for the mineralization of asulam. • Acetic acid, oxalic acid, and nitrate ions were detected as final asulam degradation by-products. • The SPEF process represents a promising option for large-scale water treatment. [ABSTRACT FROM AUTHOR]

The application of sludge biochar (SC) materials as efficient catalysts for organic pollutants mineralization via advanced oxidation process meets the good strategy of "make waste profitable". The catalytic oxidations of methyl orange (MO) and pyrene by oxalic acid modified sludge biochar (SC-OA) with and without H 2 O 2 were carried out. The analysis of Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), electronic paramagnetic resonance spectrometer (EPR) and free radical quenching experiment were performed and the definite relationships between persistent free radicals (PFRs) type and specific reactive oxygen species (ROS) were made clear. It is suggested for the first time that carbon-centered type PFRs in SC-OA without H 2 O 2 could form O 2 •- and •OH from COOH groups, while oxygen-centered type PFRs induced H 2 O 2 to produce •OH. The degradation intermediates of MO and pyrene were identified and the transformation pathways were proposed. SC-OA, possessing good sustainable utilization and clean catalytic property, is expected to be popularized and applied in the mineralization of organic pollutants, especially in the in-situ remediation of contaminated soil where is no continuous supply of H 2 O 2. It is known that the g-factors for oxygen-centered radicals are larger than 2.0040, while g-factors less than 2.0030 correspond to carbon-centered radicals. As shown in Fig. 4a, the g-factors for SC, SC-OA, and SC-OA deg were 2.1326, 1.9914, and 2.1330, indicating that carbon-centered PFRs played a key role in the catalytic degradation of MO. From the above results, we can speculate that SC has the intrinsic oxygen-centered type PFRs, and OA monoanion on the SC-OA can convert to carbon-centered PFRs (SC–OH/HOOC•) under the activation of the oxygen-centered PFRs followed by radical decarboxylation to give CO 2 and formate. Then, SC-OH/HOOC• stimulates the generation of ROS. [Display omitted] • The relationships of PFRs type and ROS generation was made clear. • Carbon-centered type PFRs in SC-OA prefer to form O 2.•- and •OH without H 2 O 2. • Oxygen-centered type PFRs in SC contribute to induce H 2 O 2 to produce.•OH. • SC-OA possess good sustainable utilization and clean catalytic property. [ABSTRACT FROM AUTHOR]

Chemical extraction of incinerated sewage sludge ash (ISSA) can effectively recycle P, but it may change the speciation and mobility of the remaining metals. This study investigated the changes of the leaching potential and distribution of metals in the chemically extracted ISSA. Batch extraction experiments with different extractants, including inorganic acids, organic acids, and chelating agents, were conducted on the ISSA collected from a local sewage sludge incinerator. The extraction of Zn, Cu, Pb, Ni, Cd, Ba, Cr and As from the ISSA and the corresponding changes of the mobility and speciation were examined. The results showed that the metals in ISSA were naturally stable because large portions of metals were associated with the residual fraction. The inorganic (HNO 3 and H 2 SO 4 ) and organic acids (citric acid and oxalic acid) significantly co-dissolved the metals through acid dissolution, but the reduction in the total concentrations did not tally the leaching potential of the residual metals. The increase in the exchangeable fraction due to destabilization by the extractants significantly enhanced the mobility and leachability of the metals in the residual ISSA. Chelating agents (EDTA and EDTMP) only extracted a small quantity of metals and had a marginal effect on the fate of the residual metals, but they significantly reduced the Fe/Mn oxide-bound fraction. In comparison, the bioaccessibility of residual metals were reduced to varying extent. Therefore, the disposal or reuse of chemically extracted ISSA should be carefully evaluated in view of possible increase in mobility of residual metals in the environment. [ABSTRACT FROM AUTHOR]

In this study, the photooxidation capacity of UVC/Oxalate (Ox) was evaluated using As(III) as a typical pollutant. The results show that the direct oxidation amount of As(III) induced by UVC in water was negligible, but the presence of Ox remarkably accelerated the oxidation rate of As(III). Under UVC irradiation, 50 μM As(III) can be completely oxidized to As(V) in the case of Ox concentration above 300 μM within 60 min. As(III) oxidation was found greatly related with the photodecomposition of Ox. Much more Ox can be mineralized in more acidic solution. At the same time, the photooxidation of As(III) was significantly favored at decreased initial pH from 8.0 to 3.0. In this reaction system, the role of oxygen was indispensable for Ox photodecomposition and As(III) photooxidation, which can be ascribed to its special roles as a precursor of reactive superoxide and an electron acceptor. In oxygen-present atmosphere, the in situ production of H 2 O 2 was detected during the photolysis of Ox and its photolysis product, i.e., OH primarily contributed to the oxidation of As(III). However, the photodecomposition of Ox and photooxidation of As(III) were significantly inhibited in the anaerobic environment. In general, the homogeneous photolysis of Ox in many commonly practiced UVC oxidation processes can be also proposed as a supplementary method of generating highly oxiditive species in aerobic condition. [ABSTRACT FROM AUTHOR]

Vanadium (V) contamination in soils is an increasing worldwide concern facing human health and environmental conservation. The fractionation of a metal influences its mobility and biological toxicity. We analyzed the fractionations of V and several other metals using the BCR three-step sequential extraction procedure. Among methods for removing metal contamination, soil washing is an effective permanent treatment. We conducted experiments to select the proper reagents and to optimize extraction conditions. Citric acid, tartaric acid, oxalic acid, and Na 2 EDTA all exhibited high removal rates of the extractable state of V. With a liquid-to-solid ratio of 10, washing with 0.4 mol/L citric acid, 0.4 mol/L tartaric acid, 0.4 mol/L oxalic acid, and 0.12 mol/L Na 2 EDTA led to removal rates of 91%, 88%, 88%, and 61%, respectively. The effect of multiple washing on removal rate was also explored. According to the changes observed in metal fractionations, differences in removal rates among reagents is likely associated with their pK a value, pH in solution, and chemical structure. We concluded that treating with appropriate washing reagents under optimal conditions can greatly enhance the remediation of vanadium-contaminated soils. [ABSTRACT FROM AUTHOR]

Methyl parathion (MP) is a typical organophosphorus pesticide that is widely used worldwide, and hydrolysis, oxidation and reduction are the main abiotic degradation processes. Manganese dioxide (MnO 2) and organic acid can participate in various geochemical processes of pollutants, a reaction system was constructed to degrade MP using δ-MnO 2 and oxalic acid. The δ-MnO 2 /oxalic acid reaction system could efficiently degrade MP, and the removal rate of MP (20 μM) reached 67.83% within 30 h under the optimized conditions (pH 5, [δ-MnO 2 ] = 2 mM, [oxalic acid] = 100 mM). MP was hydrolyzed by substitution reactions of S N @P and S N @C, and reduced by conversion of the nitro groups (-NO 2) in MP and its hydrolysates to amino groups (-NH 2). The primary active substance produced in the reaction system was the complexes dominated by Mn(III)-oxalic acid. This study provides a scientific basis for the degradation of organophosphorus pesticides using MnO 2 and an organic acid. The results have important theoretical significance and application value for pollution control and remediation of organophosphorus pesticides. [Display omitted] • δ-MnO 2 /oxalic acid can effectively degrade methyl parathion. • The optimum reaction conditions were obtained by analyzing the factors influencing the reaction system. • The transformation pathway of methyl parathion was determined from the identified products. • Methyl parathion was degraded mainly by hydrolysis and reduction. • The primary active substance was determined to be Mn(III)-oxalic acid active complexes in the reaction system. [ABSTRACT FROM AUTHOR]

Carbonaceous materials have a potential to mediated oxalic acid (OA) for Cr(VI) reduction, but the rational modification is needed for boosting the mediation of electron transfer. Herein, we utilized polyvinyl alcohol to envelop schwertmannite synthesized by Acidithiobacillus ferrooxidans biomineralization, and pyrolyzed them to obtain the carbon encapsulated iron oxides (C-2.0- Sch -PVA). SEM and TEM results demonstrated that a moderate calcination temperature would yield a neural network-like carbon encapsulated structure. C-2.0- Sch -PVA efficiently mediated OA to reduce Cr(VI), 98.4% of Cr(VI) (40 mg L−1) was reduced with 0.75 g L−1 C-2.0- Sch -PVA and 4 mM OA in 60 min. It still performed excellent results in a wide pH range, multiple anions and different water matrixes. The carbon encapsulated structure as electron shuttle mediated the electron transfer, and the O-moieties on its surface were a premise for initiating the Cr(VI) reduction process. The electron transfer from the inner iron oxides to the conjugated structure of the outer carbon shells facilitated Cr(VI) reduction as well. Moreover, OA raised the persistent free radicals' level in C-2.0- Sch -PVA as another important pathway for Cr(VI) reduction. Overall, C-2.0- Sch -PVA provides an excellent demonstration in the carbonaceous materials modification for mediating OA to reduce Cr(VI) in aqueous. [Display omitted] • Carbon encapsulated iron oxides was synthesized by biomineralization and pyrolysis. • Carbon encapsulated structure as electron shuttle mediated OA to reduce Cr(VI). • The inner iron oxide as another electron source enhanced the electron transfer. • The O-moieties were a premise for initiating the Cr(VI) reduction process. • Oxalic acid raised the PFRs level in C-2.0- Sch -PVA and facilitated Cr(VI) reduction. [ABSTRACT FROM AUTHOR]

Oxalic acid is the most abundant low molecular weight organic acid (LMWOA) in many environments and offers enormous prospects for treating Cr(VI) contamination. In this study, laboratory batch experiments were conducted to estimate the roles of oxalic acid in Cr(VI) removal by Penicillium oxalicum SL2. Oxalic acid changed the initial pH and provided a suitable condition for the growth of strain SL2 when the penicillium was applied to bioremediation of Cr(VI) contamination in alkaline soil. Gompertz model analysis indicated that initial pH affected the lag time of the growth curve of strain SL2. Scanning electron microscopy and scanning transmission X-ray microscopy analysis showed strain SL2 sufficiently contacted with contaminated soil and reduced Cr(VI) to Cr(III) in the hyphae. The results suggested that oxalic acid could enhance the bioremediation efficiency of strain SL2 though improving chromium bioleaching from the contaminated soil and strengthening Cr(VI) removal in the leaching solution. This study provided oxalic acid as a green reagent for stimulating Cr(VI) removal by strain SL2 and would expand knowledge on the roles of LMWOA in Cr(VI) bioremediation. [Display omitted] • Gompertz model could simulate the growth curve of strain SL2 under initial pH5 to pH9. • Growth of strain SL2 had a strong correlation with Cr(VI) removal. • Oxalic acid improved chromium bioleaching by strain SL2 from contaminated soil. • Oxalic acid enhanced Cr(VI) removal by strain SL2 in the leaching solution. [ABSTRACT FROM AUTHOR]

As a typical advanced oxidation process, Fe2+-persulfate (PDS) oxidation technology has been widely and efficiently reported for enhancing sludge dewaterability. However, higher dosage of Fe2+ must be added, which will restrain the oxidation efficiency of Fe2+-PDS process. In this work, the oxalic acid (OA)/Fe2+-PDS process was studied to improve paper sludge dewatering. With the OA dosage of 6 μmol (g total solid (TS))−1, Fe2+ dosage of 0.3 mmol (g TS)−1, and PDS dosage of 0.6 mmol (g TS)−1, sludge dewaterability was improved more efficiently. The specific resistance to filtration and water content of sludge cake were decreased by 70.7% and 8.0%, respectively. In comparison with Fe2+-PDS process, the viscosities of sludge suspension and supernatant were further reduced by 3.73% and 51.77%, respectively, and the contents of extracellular polymeric substances fractions were increased. The improved sludge dewaterability in OA/Fe2+-PDS process was mainly contributed by the synergistic effect of oxidative disintegration by free radicals and flocs re-flocculation, the contributions of which were the orders: metal cations > sulfate radical > hydroxyl radical. OA enhanced the efficient disintegration of sludge flocs, released more bound water, generated more Fe3+-oxalate complexes, and finally increased the sludge particle size significantly, forming a larger aggregation and obvious cracks. Additionally, the stabilization of several heavy metals was improved due to the chelating capacity of OA. These works will provide a novel approach for sludge dewatering in the PDS oxidation process. [Display omitted] • Oxalic acid (OA) chelated Fe2+ activated persulfate process was more efficient for enhancing sludge dewaterability. • Free radicals oxidation and flocculation effect were the proposed pathways on the improvement of sludge dewaterability. • OA promoted the recovery of Fe2+ and the production of Fe3+-oxalate complexes. • The release of water bound on extracellular polymeric substances improved sludge dewaterability. [ABSTRACT FROM AUTHOR]

A batch experiment was conducted to investigate the mobilization of soil-borne arsenic by three common low-molecular-weight organic acids with a focus on dosage and time effects. The results show that oxalic acid behaved differently from citric acid and malic acid in terms of mobilizing As that was bound to iron compounds. At an equivalent molar concentration, reactions between oxalic acid and soil-borne Fe were kinetically more favourable, as compared to those between either citric acid or malic acid and the soil-borne Fe. It was found that reductive dissolution of soil-borne Fe played a more important role in liberating As, as compared to non-reductive reactions. Prior to the 7th day of the experiment, As mobility increased with increasing dose of oxalic acid while there was no significant difference (P > 0.05) in mobilized As among the treatments with different doses of citric acid or malic acid. The dosage effect on soil-borne As mobilization in the citric acid and malic acid treatments became clear only after the 7th day of the experiment. Soluble Ca present in the soils could cause re-immobilization of As by competing with solution-borne Fe for available organic ligands to form practically insoluble organic compounds of calcium (i.e. calcium oxalate). This resulted in transformation of highly soluble organic complexes of iron (i.e. iron oxalate complexes) into slightly soluble organic compounds of iron (i.e. iron oxalate) or free ferric ion, which then reacted with the solution-borne arsenate ions to form practically insoluble iron arsenates in the latter part of the experiment. [ABSTRACT FROM AUTHOR]

The final sinkers of polyaromatic hydrocarbons are water sources, where they undergo bioaccumulation and biomagnification, leading to adverse mutagenic, carcinogenic, and teratogenic effects on exposure in flora, fauna, and humans. Two indigenous strains, Pseudomonas sp. WDE11 and Pseudomonas sp. WD23, isolated from refinery effluent, degraded over 97.5% of benzo(a)fluorene (10 mg/L) in 7 days. On growth at concentration dependent amounts (50 mg/L and 100 mg/L), the degradation reduced to approximately 90% and 80% respectively in 56 days. Degradation kinetics was concentration dependent, as degradation followed first-order and second-order kinetics for 50 mg/L and 100 mg/L respectively. The half-life for degradation of benzo(a)fluorene ranged between 11.64 - 12.26 days and 13.11–14.5 days for strains WDE11 and WD23 respectively. The values of Andrew-Haldane kinetic parameters i.e. μ m a x , K s , and K i were 0.306 day−1, 11.11 mg/L, and 120.41 mg/L for strain WDE11 respectively, while for strain WD23, the respective values were 0.312 day−1, 9.97 mg/L, and 152 mg/L. Degradation metabolites were identified by their MS patterns as 3,4-dihydroxy fluorene, 2-(1-oxo-2,3-dihydro-1H-inden-2-yl) acetic acid, 3,4-dihydrocoumarin, salicylic acid, catechol, and oxalic acid. Metabolic pathway of degradation constructed, revealed that benzo(a)fluorene was metabolized via the formation of fluorene, further metabolized by salicylate pathway forming catechol. The catechol formed was degraded into simpler metabolites by meta-cleavage pathway, which was validated by catechol 2,3 dioxygenase enzyme activity. [Display omitted] • Indigenous Pseudomonas strains utilize benzo(a)fluorene as sole carbon source. • Degrade over 80% of 100 mg/L in 56 days. • Degradation kinetics is concentration dependent – first-order at lower concentration, second-order at higher. • Metabolic pathway of benzo(a)fluorene elucidated – metabolites of fluorene degradation identified. • Salicylate pathway followed by meta cleavage of catechol – first report. [ABSTRACT FROM AUTHOR]

The presence of 1,4 dioxane in wastewater is associated with severe health and environmental issues. The removal of this toxic contaminant from the industrial effluents prior to final disposal is necessary. The study comprehensively evaluates the performance of sequential batch membrane bioreactor (MBR) for treating wastewater laden with 1,4 dioxane. Acetate was supplemented to the wastewater feed as an electron donor for enhancing and stimulating the microbial growing activities towards the degradation of 1,4 dioxane. The removal efficiency of 1,4 dioxane was maximized to 87.5 ± 6.8% using an acetate to dioxane (A/D) ratio of 4.0, which was substantially dropped to 31.06 ± 3.7% without acetate addition. Ethylene glycol, glyoxylic acid, glycolic acid, and oxalic acid were the main metabolites of 1,4 dioxane biodegradation using mixed culture bacteria. The 1,4 dioxane degrading bacteria, particularly the genus of Acinetobacter , were promoted to 92% at the A/D ratio of 4.0. This condition encouraged as well the increase of the main 1,4 dioxane degraders, i.e., Xanthomonadales (12.5%) and Pseudomonadales (9.1%). However, 50% of the Sphingobacteriales and 82.5% of Planctomycetes were reduced due to the inhibition effect of the 1,4 dioxane contaminate. Similarly, the relative abundance of Firmicutes, Verrucomicrobia, Chlamydiae, Actinobacteria, Chloroflexi, and Nitrospirae was reduced in the MBR at the A/D ratio of 4.0. The results derived from the microbial analysis and metabolites detection at different A/D ratios indicated that acetate supplementation (as an electron donor) maintained an essential role in encouraging the microorganisms to produce the monooxygenase enzymes responsible for the biodegradation process. Economic feasibility of such a MBR system showed that for a designed flow rate of 30 m3∙d−1, the payback period from reusing the treated wastewater would reach 6.6 yr. The results strongly recommend the utilization of mixed culture bacteria growing on acetate for removing 1,4 dioxane from the wastewater industry, achieving dual environmental and economic benefits. [Display omitted] • Sequential batch membrane bioreactor is efficient for 1,4 dioxane biodegradation. • The removal of 1,4 dioxane amounted to 87.5 ± 6.8% at acetate to 1,4 dioxane ratio of 4.0 • Proteobacteria phyla were increased from 30.1 to 69.5% and Rhodobacterales from 0.3 to 19%. • Xanthomonadales were boosted from 0.9 to 12.5% with 1,4 dioxane addition. • Acinetobacter genus degrading 1,4 dioxane accounted for 92% of the Pseudomonadales. [ABSTRACT FROM AUTHOR]

The translocation of lead (Pb) in the soil–mulberry–silkworm food chain and the process of Pb detoxification in the mulberry–silkworm chain were investigated. The amount of Pb in mulberry, silkworm, feces and silk increased in a dose-responsive manner to the Pb contents in the soils. Mulberry roots sequestered most of the Pb, ranging from 230.78 to 1209.25 mg kg −1 . Over 92% of the Pb in the mulberry leaves was deposited in the cell wall, and 95.29–95.57% of the Pb in the mulberry leaves was integrated with oxalic acid, pectates and protein, and it had low bioavailability. The Pb concentrations in the silkworm feces were 4.50–4.64 times higher than those in the leaves. The synthesis of metallothioneins in three tissues of the silkworms was induced to achieve Pb homeostasis under Pb stress. These results indicated the mechanism involved in Pb transfer along the food chain was controlled by the detoxification of Pb in different trophic levels. Planting mulberry and rearing silkworm could be a promising approach for the remediation of Pb-polluted soils due to the Pb tolerance of mulberry and silkworm. [ABSTRACT FROM AUTHOR]

Agricultural plastic films and triazole fungicides are widely used in agricultural production process. Exposure to natural environment, agricultural plastic films will degrade into micron plastic particles, which will adsorb pesticide molecules and may affect their toxicity, biological activity and persistence. The long-term coexistence of microplastics (MPs) and triazole fungicides will bring potential harms to the agricultural ecological environment. Therefore, two kinds of triazole fungicides flusilazole (FLU) and epoxiconazole (EPO) were selected as cases and the adsorption behaviors of them on polystyrene and polyethylene were investigated. A series of factors which could affect the adsorption behavior were evaluated. Specifically, the particle size of MPs could affect its adsorption capacity, and the smaller the particle size, the stronger the adsorption capacity. Moreover, with the increase of pH value from 6.0 to 9.0, the adsorption capacity of MPs to target compounds gradually increased. The effect of ionic strength was evaluated by NaCl, and 0.05% of NaCl was beneficial to the adsorption process, while the continuous increase of NaCl concentration inhibited the adsorption. Oxalic acid and humic acid decreased the adsorption capacity of flusilazole on PE by 15.99-32.00% and PS by 35.02-48.67%, respectively. In addition, compared with the single pesticide system, the adsorption capacity of MPs for flusilazole and epoxiconazole in the binary pesticides system decreased by 36.13-37.93% and 44.36-51.35%, respectively, indicating that competitive adsorption occurred between the two pesticides. Meanwhile, the adsorption process was evaluated by adsorption kinetics and adsorption isotherms and were consistent with pseudo-second-order kinetic model and Freundlich isotherm model, respectively. Finally, several characterization analyses were conducted to investigated the adsorption mechanism, and hydrogen, halogen bonding and hydrophobic interaction proved to play an important role. The study on the adsorption behavior and mechanism of pesticide on MPs was the basis of assessing the risk of joint exposure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Developing low-cost and efficient materials for dye pollutant removal under mild condition remains a great challenge. Here K+ and Tb3+ co-doped porous MnO 2 (K–Tb–MnO 2) nanoparticles with tailored properties including crystal structure, surface area and catalytic activity have been synthesized. Experimental results reveal that K–Tb–MnO 2 nanoparticle has higher specific surface area, Mn3+ content and surface oxygen vacancies than pristine MnO 2 nanoparticle and single-doped MnO 2 materials, showing the uniqueness of dual-doped metal ions. Using methyl blue (MB) as a model pollutant, its removal efficiency by K–Tb–MnO 2 nanoparticles within 5 min is 93.6%, which is 18, 8.3, and 2.9 times higher than that of MnO 2 , K–MnO 2 , and Tb–MnO 2 nanomaterials, respectively. Oxalic acid triggered MnO 2 material dissolving assay and FT-IR spectrum suggested that remarkable performance of K–Tb–MnO 2 nanoparticle toward MB removal can be attributed to a combined effect of adsorption (16% MB removal) and catalytic degradation (84% MB removal). Moreover, K–Tb–MnO 2 nanoparticle mediated MB degradation is demonstrated to be a combination of non-radical oxidation by Mn3+ and radical-participated degradation, with 1O 2 as the main species. And the intermediates and pathways of MB degradation were studied by liquid chromatography-mass spectrometry. Importantly, cell viability experiment suggests that the toxicity of MB dye could be efficiently alleviated after the treatment with K–Tb–MnO 2 nanoparticle. These results demonstrate the great potential of the novel K–Tb–MnO 2 particles to be used as a highly effective nanomaterials to reduce the risk of dye wastes toward the environment and human health. [Display omitted] • K+ and Tb3+ co-doped porous MnO 2 (K–Tb–MnO 2) with improved properties has been synthesized. • K–Tb–MnO 2 exhibited higher methyl blue (MB) removal capacity than pristine MnO 2 and single metal dopant MnO 2. • The MB removal performance of K–Tb–MnO 2 can be ascribed to a combined effect of adsorption and catalytic degradation. • The toxicity of MB dye could be efficiently alleviated by the treatment with K–Tb–MnO 2 nanoparticle. [ABSTRACT FROM AUTHOR]

Arsenic contamination in abandoned soils is a global concern which warrants an effective method of remediation. In this study, two organic acids and one biodegradable chelating agent were used to treat arsenic (As) contaminated abandoned mine soils. The concentration of As was 19,100 and 75,350 (mg/kg) for Webbs Consols (WC) and Mole River (MR) samples, respectively. X-ray diffraction and scanning electron microscopy confirmed that tooeleite, arsenopyrite, scorodite and quartz were the major minerals in these soils. A major portion of the As was composed of amorphous and crystalline oxides of Fe and Al determined by sequential extraction. Among the three washing reagents (oxalic acid, citric acid and EDDS) oxalic acid showed the best performance for extracting As. Based on the batch experiment, 0.5 M oxalic acid and 3 h of washing was the most efficient treatment to extract As and other trace elements. Extraction of As, Fe, and Pb was 70, 55, and 48% respectively for WC, while 68, 45 and 63% respectively for MR soil. Oxalic acid extracted 75 and 83% of As and Fe, respectively from tooeleite. Leachability and bioaccessibility of As and Fe in the treated soil was reduced due to washing. However, bioaccessibility and leachability of Pb in soil and Fe and As in tooeleite increased in washed samples. Though the leachability and bioaccessibility of As and Fe in soil was reduced in the treated soil, As still exceeded the USEPA criteria (5 mg/L) which is needed to successfully remediate soil by washing. Soil washing and subsequent solidification/stabilization could be an alternative option to remediate extremely contaminated abandoned mine soil. [Display omitted] • Oxalic acid was efficient in extracting As and other trace elements in abandoned mine soils. • Extraction of As and other trace elements increased with increasing Fe extraction. • Bioaccessibility and leachability of As was reduced after soil washing. [ABSTRACT FROM AUTHOR]

Highlights: [•] Malic and citric acids could inhibit immobilization of Pb(II) by PR and HAp1. [•] Oxalic acid enhanced the immobilization of Pb(II) by PR via precipitation with lead. [•] Oxalic acid enhanced the dissolution of HAp1 by complexation with calcium. [•] HAp2 had best immobilization efficiency of Pb regardlessof the addition ofLMWOAs. [Copyright &y& Elsevier]