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Zinc doped Cerium oxide nanoparticles are prepared by a facile single step co-precipitation method. The synthesis method involves co-precipitation of the precursor salts using a non-toxic, green reagent oxalic acid, followed by annealing process at reliable low temperature. The effect of Zn doping on cerium nanoparticles are clearly investigated by the different characterization techniques such as X-Ray Diffraction, Scanning electron microscopy for morphological study, Fourier Transform Infra-Red studies to study the functional groups present and UV–Vis spectroscopy for optical study. The micro-structural and optical studies exhibit remarkable variation in the structural, optical, and morphological properties.

Due to the progressive shortage of primary resources and growing environmental concerns over industrial and household residues, proper management of electronic wastes is of great importance in addressing sustainability issues. Spent batteries are considered as important secondary sources of their constituting components. In this study, the co-recycling of used zinc-carbon and lithium-ion batteries was performed aiming at the recovery of their manganese and lithium contents as compounds which can be used as precursors for the synthesis of spinel LiMn2O4. Manganese was recovered in the form of amorphous, submicron, spherical nodules of MnO2 after acid leaching of zinc-carbon battery pastes. Lithium was obtained from nickel-manganese-cobalt (NMC) batteries as its monohydrate oxalate (C2HLiO4.H2O) through selective leaching in oxalic acid followed by crystallization. Lithium carbonate was also prepared by subsequent calcination of the oxalate. The synthesis of LiMn2O4 spinel cathode was carried out using the recycled Li- and Mn-containing compounds via solid-state synthesis method. The effect of such parameters as type of reactants (C2HLiO4.H2O, Li2CO3, Mn2O3, and MnO2), temperature (750, 800, and 850 °C), and time (8 and 10 h) on the synthesis of LiMn2O4 was investigated. The products were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The crystallographic parameters used to predict the electrochemical behavior of synthesized cathode materials were derived from XRD patterns. Based on these, the spinel powder synthesized at 850 °C for 10 h was determined as the sample with the best potential electrochemical properties among the synthesized samples. The galvanostatic charge/discharge characterization within the voltage range of 2.5–4.3 V showed the specific capacity of the 850°C-10 h sample to be 127.87 mAhg−1.

Solution equilibrium calculations were performed in this study to understand the impact of contaminant metal ions on the precipitation efficiency of selected rare earth elements (Ce3+, Nd3+, and Y3+) using oxalic acid as a precipitant. Trivalent metal ions, Al3+ and Fe3+, were found to considerably affect the precipitation efficiency of REEs. When Al3+ and Fe3+ concentrations were increased by 1 × 10−4 mol/L, in order to achieve an acceptable cerium recovery of 93% from solutions containing 1 × 10−4 mol/L Ce3+, oxalate dosage needed to increase by 1.2 × 10−4 and 1.68 × 10−4 mol/L, respectively. Such great impacts on the required oxalate dosage were also observed for Nd3+ and Y3+, which indicates that oxalic acid consumption and cost will be largely increased when the trivalent metal ions exist in REE-concentrated solutions. Effects of the divalent metal ions on the oxalate dosage is minimal. Furthermore, solution equilibrium calculation results showed that the precipitation of Fe3+ and Ca2+ (e.g., hematite and Ca(C2O4)∙H2O(s)) likely occurs during the oxalate precipitation of REEs at relatively high pH (e.g., pH 2.5), which will reduce rare earth oxalate product purity. In addition to the metal ions, anionic species, especially SO42−, were also found to negatively affect the precipitation recovery of REEs. For example, when 0.1 mol/L SO42− occurs in a solution containing 1 × 10−4 mol/L Ce3+ and 4 × 10−4 mol/L oxalate, the pH needed to be elevated from 2.0 to 3.3 to achieve the acceptable recovery. Overall, findings from this study provide guidance for the obtainment of high-purity rare earth products from solutions containing a considerable amount of contaminant metal ions by means of oxalic acid precipitation. Accepted version

The increase of harmful carbon monoxide (CO) caused by incomplete combustion can affect human health even lead to suffocation. Therefore reducing the CO discharged by vehicles or factories is urgent to improve the air quality. The spinel cobalt (II, III) oxide (Co3O4) is an active catalyst for CO abatement. In this study, we tried to fabricate dispersing Co3O4 via the dispersion-precipitation method with acetic acid, formic acid, and oxalic acid as the chelating dispersants. Then, the asprepared samples were calcined at 300 ºC for 4 h to obtain active catalysts, and assigned as Co(A), Co(F) and Co(O) respectively, the amount of the dispersants used are labeled as I (0.12 mole), II (0.03 mole) and III (0.01 mole). For comparison, another CoAP sample was prepared via alkaliinduced precipitation and calcined at 300 ºC. All samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), scanning electron microscope (SEM), and nitrogen adsorption/desorption system, and the catalytic activity focused on the CO oxidation. The influence of chelating dispersant on the performance of abatement of CO was pursued in this study. Apparently, the results showed that the chelating dispersant can influence the catalytic activity of CO abatement. An optimized ratio of dispersant can improve the performance, while excess dispersant lessens the surface area and catalytic performance. The series of Co(O) samples can easily donate the active oxygen since the labile Co–O bonding and indicated the preferential performance than both Co(A) and Co(F) samples. The nanorod Co(O)-II showed preferential for CO oxidation, T50 and T90 approached 96 and 127 ºC, respectively. Also, the favorable durability of Co(O)-II sample maintains 95% conversion still for 50 h at 130 ºC and does not emerge deactivation.

New coordination compounds trans-bis(oxalato)diaquarhodiate sodium dihydrate Na[Rh(H2O)2Ox2]·2H2O (crystallizes in two polymorphic forms NaRh-1 and NaRh-2), trans-bis(oxalato)hydroxoaquarhodiate sodium tetrahydrate Na2[Rh(H2O)(OH)Ox2]·4H2O (Na2Rh) and trans-bis(oxalato)diaquarhodic acid tetrahydrate (H3O)[Rh(H2O)2Ox2]·4H2O (HRh) are synthesized. The compounds are characterized by IR spectroscopy, elemental analysis and single crystal X-ray diffraction. NaRh-1, NaRh-2 and Na2Rh crystallize in space group P 1. Trans-bis(oxalato)diaquarhodic acid exists not only in solution, but can also crystallize as a tetrahydrate (space group C2/c). The formation of various species in solution of rhodium hydroxide in oxalic acid and their redistribution were studied using 103Rh NMR spectroscopy.

Converting the γ phase into the α phase completely is necessary in the presintering stage of industrial alumina (Al2O3), which requires high temperature and energy consumption. To reduce the presintering temperature, γ-Al2O3 was activated by oxalic acid. XRD, 27Al-MAS-NMR and TG-DSC were used to characterize the γ - alumina before and after activation, and the phase transformation was studied. The formation temperature of α-Al2O3 decreased to 1029 °C for oxalic acid activated γ-Al2O3, and the α-fraction was 100% for activated γ-Al2O3 at 1300 °C. After oxalic acid activation, the diffraction peak intensity of γ-Al2O3 decreased significantly; the results of 27Al-MAS-NMR suggested that octahedral [AlO6] in γ-Al2O3 was easier than tetrahedral [AlO4] to be attacked by oxalic acid, and the formation of pentavalent [AlO5] with higher reaction activity, which was in favour of the lowering formation temperature of α-Al2O3. The dissolution concentration of Al increased after oxalic acid activation, and the dissolution process was controlled by surface reactions. Oxalic acid mainly attacked the octahedral aluminium in γ-Al2O3 and extracted Al as three complexes of [Al(C2O4)]+, [Al(C2O4)2]- and [Al(C2O4)3]3-. Oxalic acid activated γ - Al2O3 with a lower phase transformation temperature has broad application prospects in the alumina industry.

Background Oxalic acid (OA) existing widely in animal, plants, and factory processes may affect human health and result in environmental pollution. It is highly desired to develop a rapid fluorescent sensing for accurate determination of OA content in food and wastewater. Methods We are the first to design an easy-to-prepare rhodamine-6G based zinc complex as a fluorescent probe for the selective detection of OA and explore the sensing mechanism between zinc complex and OA. The zinc complex presents the coordination with two Zn2+ and both of rapid color and linear fluorescent response toward OA in the range of 0-10 μM. Findings The detection limit of the probe for OA can reach to 1.20 μM, which is superior to those reported in the literature. Compared with other dicarboxylic acids, the binuclear zinc complex probe displays rapid detection and high selectivity for OA over a wide pH range due to the steric hindrance and ring strains. The recycling of the probe can be achieved by the treatment with sodium sulfide to form zinc sulfide and regenerate the intermediate.

The extraction of tungsten from scheelite was carried out using a sulfuric acid solution with oxalic acid as the chelating agent. Tungsten was obtained in the form of highly soluble hydrogen aqua oxalato tungstate (H2[WO3(C2O4)·H2O]) during the leaching process, while calcium remained in the residue as calcium sulfate dihydrate (CaSO4·2H2O). About 99.2% of the tungsten was leached at 70 °C, 1.5 mol/L sulfuric acid, 1 mol/L oxalic acid, a liquid/solid ratio of 25:1 (mL/g), an oxalic acid to sulfuric acid molar ratio of 1:1, a stirring speed of 300 r/min and a leaching time of 2 h. H2[WO3(C2O4)·H2O] was thermally decomposed into tungstic acid (H2WO4), and tungsten trioxide (WO3) was directly produced by calcining H2WO4 at 700 °C for 2 h. The surface chemical reaction was determined to be the controlling step during tungsten leaching, and the apparent activation energy was calculated to be 51.43 kJ/mol.

To co-extract vanadium, titanium, and chromium from vanadium slag, a cleaner process featuring oxalic acid hydrothermal leaching with synergy of Fe powder was proposed in this paper. With the leaching temperature of 125 °C, oxalic acid concentration of 25 wt pct, liquid-to-solid mass ratio of 8:1, leaching time of 90 minutes, and iron powder addition of 3.2 wt pct, the leaching extents of vanadium, titanium, and chromium can reach up to 97.9, 98.4, and 93.3 pct, respectively. The non-toxic residue is mainly composed of FeC2O4·2H2O, MnC2O4·2H2O, and amorphous SiO2. Compared with the traditional sodium roasting-water leaching and calcification roasting-acid leaching processes, this novel process is possessed of two prominent advantages. Firstly, without the roasting step, the process is simplified significantly and the energy consumption is reduced greatly. Secondly, the valuable components titanium and chromium which cannot be extracted by the traditional processes are leached synchronously and efficiently.

A technique is developed and new composite materials containing manganese oxides MnxOy (x = 1, 2, 3; y = 2, 3, 4) are synthesized based on high-silica nanoporous glasses (NPGs). The synthesis is carried out by successive impregnation of porous glass plates in aqueous solutions of manganese chloride (MnCl2) and oxalic acid (H2C2O4), followed by heat treatment of the samples in an argon atmosphere to decompose the reaction product (MnC2O4). The chemical composition and phase composition of the obtained composites are investigated.

In this study, alkali/acid treatment and ion exchange post-synthesis modification methods to modify the pore diameter and structure of molecular sieve 13X (MS13X) were applied to obtain products, which could then be implemented to improve the enrichment recovery of hopanoids in petroleum. The modification products were analyzed by SEM with EDS, XRD and nitrogen physisorption. The results indicated that the product which had been prepared in the oxalic acid ethanol solution formed some mesopores, and also retained the initial framework of crystal. It was revealed that this product was able to remarkably increase the recovery rate of hopanoids in petroleum without leading to a significant isotope fractionation phenomenon. It is thus shown that this modification method of non-aqueous oxalic acid solution for MS13X can be used as an effective pretreatment tool in the application of compound-specific isotope analysis of hopanes with low concentration.

Актуальность исследования обоснована целесообразностью создания благоприятных условий при проведении термохимической обработки топливных фрагментов с целью обеспечения одновременной трансформации керамического топлива в порошкообразный материал и полного высвобождения продукта реакции из оболочки, а также удаления из топливной композиции перед гидрометаллургическими операциями летучих продуктов деления (тритий, иод-129, углерод-14, радиоактивные благородные газы). Цель: определить основные технологические параметры процесса получения окислительной смеси NxOy-O2-СО2-Н2О(пар), пригодной для использования на операции термохимической обработки фрагментов оболочечного топлива на основе диоксида урана керамического качества. Объекты: раствор смеси азотной и щавелевой кислот, окислительная смесь NxOy-O2-СО2-Н2О(пар), образец необлученного твэл на основе диоксида урана. Методы: экспериментальные исследования, кондуктометрическое и потенциометрическое титрование, гравиметрический и рентгенофазовый анализ, морфологические исследования, газовая хроматография. Результаты. Исследованы основные физико-химические закономерности процесса получения окислительной смеси NxOyO2-СО2-Н2О(пар) для термохимической обработки топлива на основе диоксида урана. Установлено, что при пропускании раствора смеси кислот (азотная кислота - 380 г/л, щавелевая кислота - 80 г/л) со скоростью 5 колон. об/час через слой катализатора Pt/Cr2O3/ZrO2 при температуре 368-373 К происходит образование газового потока, содержащего 26 об. % диоксида азота, 20 об. % монооксида азота, 44 об. % диоксида углерода, 10 об % паров воды. Доокисление монооксида азота и каталитическую активацию полученного газового потока предпочтительно проводить на насадке Pt/Cr2O3/ZrO2 при температуре 413 К и соотношении высоты насадочного слоя к диаметру колонны 5:1, в результате чего полученная окислительная смесь соответствует следующему составу: 41 об. % диоксида азота, 6 об. % монооксида азота, 42 об. % диоксида углерода, 6 об. % паров воды, 5 об % кислорода. Показана принципиальная возможность трансформации керамического топлива на основе необлученного диоксида урана, заключенного в циркониевую оболочку, в порошкообразный октаоксид триурана с использованием в качестве окислителя каталитически активированной смеси NxOy-O2-СО2-Н2О(пар). Получен порошкообразный материал, полностью отделенный от циркониевой оболочки, который по результатам рентгенофазового и гравиметрического анализа (соотношение O/U=2,67) соответствовал брутто-формуле U3O8. The relevance of the research is based on the rationale for creating suitable environment for fuel thermochemical treatment to ensure simultaneous ceramic fuel conversion into powder-like material, complete recladding of reaction product, and volatile fission products entrapment (tritium, iodine-129, carbon-14, radioactive noble gases) from fuel composition prior to hydrometallurgical processes. The main aim is to find main process parameters of NxOy-O2-CO2-H2O(steam) oxidizing mixture which can be used for thermochemical treatment of cladded fuel containing ceramic uranium dioxide. Subjects: solution of nitric acid and oxalic acid composition, NxOy-O2-CO2-H2O(steam) oxidizing mixture, sample of new fuel element containing uranium dioxide. Methods: investigational studies, conductometric and potentiometric titration, gravimetric and and X-ray phase analysis, morphological studies, gas chromatography. The results. The main physical and chemical rules of fabricating NxOy-O2-CO2-H2O(steam) oxidizing mixture were studied for thermochemical treatment of fuel containing uranium dioxide. It was found that generation of gas bearing nitrogen dioxide (26 vol. %), nitrogen monoxide (20 vol. %), carbon dioxide (44 vol. %) and water vapor (10 vol. %) was the result of passing acids mixture (nitric acid - 380 g/l, oxalic acid - 80 g/l) at the rate of 5 column volumes per hour through Pt/Cr2O3/ZrO2 catalyst layer at 368-373 K. It is preferable to implement nitrogen monoxide full oxidation and gas catalytic activation by means of Pt/Cr2O3/ZrO2 packing at 413 K and height of packed bed to column diameter ratio as 5:1. Upon doing that, oxidizing mixture has the following composition: nitrogen dioxide (41 vol. %), nitrogen monoxide (6 vol. %), carbon dioxide (42 vol. %), water vapor (6 vol. %) and oxygen (5 vol. %). Ability in principle to convert ceramic fuel containing nonirradiated uranium dioxide in zirconium cladding into powder-like triuranium octoxide was proven by using NxOy-O2-CO2-H2O(steam) mixture as an oxidizing agent following catalytic activation. We made powder-like material separated from zirconium cladding in full which corresponds to molecular formula U3O8 from X-ray phase and gravimetric analyses, O/U=2,67.

To quickly and drastically reduce CO2 emissions and meet our ambitions of a circular future, we need to develop carbon capture and storage (CCS) and carbon capture and utilization (CCU) to deal with the CO2 that we produce. While we have many alternatives to replace fossil feedstocks for energy generation, for materials such as plastics we need carbon. The ultimate circular carbon feedstock would be CO2 . A promising route is the electrochemical reduction of CO2 to formic acid derivatives that can subsequently be converted into oxalic acid. Oxalic acid is a potential new platform chemical for material production as useful monomers such as glycolic acid can be derived from it. This work is part of the European Horizon 2020 project "Ocean" in which all these steps are developed. This Review aims to highlight new developments in oxalic acid production processes with a focus on CO2 -based routes. All available processes are critically assessed and compared on criteria including overall process efficiency and triple bottom line sustainability.

An efficient and simple process was developed to extract valuable metals from monazite ore. Monazite was subjected to acidic digestion. Then isopropyl alcohol as a miscible solvent was added in different ratios. The produced REEs were purified with Dowex 50 cation-exchange resin. 4 M HCl was used for the complete REEs elution. Thorium was separated by precipitation with 20% oxalic acid. Uranium was separated using Dowex 1 anion-exchange resin, eluted with acidified sodium chloride (1 M NaCl + 0.15 M H2SO4), and precipitated at pH 7.5.

Here, we aimed to synthesize an oxalic acid (Oxa)-induced cobalt (Co) and nickel (Ni) bimetallic assembled polyaniline (PANi) nanocomposite as a bifunctional material through a microwave-assisted method, where the Oxa was used as a complexing agent to determine the final particle size distribution of the metal dispersion. The as-prepared materials were characterized well using FTIR, PXRD, SEM, XPS, BET and zeta potential analysis. Among the prepared Co–Oxa, Ni–Oxa, Co–Oxa–Ni and Co–Oxa–Ni@PANi electrode materials, Co–Oxa–Ni@PANi nanocomposite exhibited a higher specific capacitance (1420 F g−1) at the current density of 1 A g−1, and better recyclability in a three-electrode system with 1 M KOH electrolyte, where the electrolyte could diffuse between the carbon layers of PANi provides sufficient space to buffer the volume change. Besides, the chromium [Cr(VI)] adsorption density on Co–Oxa–Ni@PANi nanocomposite was much higher at solution pH conditions (5.3) compared to other materials developed for this study. The maximum uptake of Cr(VI) on Co–Oxa–Ni@PANi nanocomposite was found to be 52.52 mg g−1 with a contact time of 240 min at pH 5.3. The synthesized material was regenerated up to five times with 0.1 M NaOH solution as an eluent. A very high degree of selectivity and no dissolution was observed for the prepared nanocomposite in the selectivity and stability studies, respectively. The findings of this study are of great importance in the development of multitalented materials by the one-pot two-step (1p2s) method. These materials can be used in both fields of energy and environment with minimal energy consumption.

A procedure is developed for the separate determination of the Sn(II) and Sn(IV) in the range of 0.05–0.25 M in acidic aqueous and ethylene glycol solutions in the presence of Ni(II), Cu(II), F–, a surfactant (OS-20), and citric or oxalic acids. The direct iodatometric titration of Sn(II) is used before and after the reduction of Sn(IV) with aluminum. The procedure is applicable to the analysis of electrolytes for the deposition of tin and Ni–Sn and Cu–Sn alloys and can be used to monitor changes in the concentrations of Sn(II and IV) as a result of redox processes in electrolytes and the hydrolysis of tin compounds. The interfering effect of copper consists in the interaction of Cu(II) with Sn(II) and Al with the formation of Cu(I) ions, reacting with iodate ions, and is eliminated by the introduction of oxalic acid. The relative error in determining the concentration of tin in the absence of copper(II) ions and in the presence of other components does not exceed 2.2%, and in the presence of Cu(II) the error is 4.3%.

Manganese nodules from ocean bed are potential resources of Cu, Ni, and Co for which land-based deposits are scarce in India. The present work describes a novel approach of using glycerol, a nontoxic biomass-derived reductant, for the reductive acid leaching of manganese nodules. Parameters such as acid concentration, time, temperature, and pulp density were optimized for leaching. The optimal leaching conditions were found to be 10% (w/v) pulp density and 10% (v/v) H2SO4 at 80 °C with 1% (v/v) glycerol yielding >95% of Ni and >98% Cu, Co, and Mn extraction within an hour. Kinetic analysis of the data based on the initial rate method showed that the leaching process was chemical reaction-controlled with an apparent activation energy of 55.47 kJ/mol. Various oxidation intermediates of glycerol formed during leaching were identified using mass spectrometry and Raman spectroscopy, and a probable oxidation pathway of glycerol during the leaching process has been elucidated based on the analysis. Glycerol was oxidized to glyceraldehyde, glyceric acid, tartronic acid, dihydroxyacetone, hydroxy pyruvic acid, glyoxalic acid, oxalic acid, and finally converted to CO2 during leaching. The fast reaction kinetics, near-complete dissolution of manganese, and other associated metals in the nodule can be attributed to the participation of all intermediate products of glycerol oxidation in redox reactions with MnO2, enhancing the overall reduction leaching efficiency.

In last several decades, electromagnetic wave (EMW) absorbing materials have attracted much attention because of their ability to attenuate EMW and reduce the electromagnetic pollution caused by the rapid development of information technology. Among many electromagnetic wave absorbers, nickel cobaltite (NiCo2O4) stands out for its excellent electromagnetic wave absorbing performance. However, as the most commonly used synthesis method of NiCo2O4-based materials, hydrothermal method is time-consuming and complicated, which hinders the actual production and application of nickel cobaltite. In this work, agglomerate NiCo2O4 of lamellar accumulation was prepared by chemical coprecipitation and calcination with oxalic acid as precipitant. The effect of pH control on the properties of product was studied by adding ammonia to change the microenvironment of coprecipitation system. When the pH value of the coprecipitation system is 7, the absorbent has been prepared successfully which has broad absorption bandwidth of 6.26 GHz (11.74–18 GHz) and ultrathin matching thickness of 1.58 mm. The synthesis method is simple, convenient, time-saving and energy-saving, and the product has excellent electromagnetic wave absorption capacity, which has a good industrial application prospect.

Oxygen-doped g-C₃N₄ (CN) with carbon vacancies (O–CNC) was synthesized by microwave heating the mixture of melamine–cyanuric acid (MCA) supramolecular aggregates and oxalic acid for only 7 min. The as-synthesized O–CNC shows a mesoporous structure and exhibits a tunable band structure, optimized charge separation, and significantly enhanced two-electron reduction for H₂O₂ production. The photocatalytic H₂O₂ production rate reaches 2008.4 μmol h–¹ g–¹ under simulated sunlight irradiation, which is more than 4 times higher than that of pristine bulk CN. The enhanced photocatalytic performance is attributed to the synergistic effects of the mesoporous structure with a large specific surface area, doped oxygen atoms, and carbon vacancies. These results have provided a facile and efficient way for realizing the practical application of CN in photocatalytic H₂O₂ production.

Zamak are zinc-aluminum alloys that, when processed by squeeze casting (injection), presents porosity defects on its surface, compromising its corrosion resistance. Thus, with the purpose to minimize these defects and increase corrosion resistance of Zamak, this work proposes formation of layers by anodizing, containing oxalates and oxides based on Zn and Al. Anodizing parameters used were 100 V, 10 mA.cm−2, room temperature, oxalic acid 0.3 mol.L−1 as electrolyte and 5 or 60 min. Samples were analyzed by infrared spectroscopy (ATR-FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electrochemical impedance spectroscopy (EIS). The model suggested in this work shows that Zamak anodization occurs in three stages. In the first stage, zinc oxalate is formed as crystallites. In the second stage, zinc oxalate is solubilized and the formation of Al2O3 and ZnO (with smooth aspect) takes place. In the third stage, increasing thickness of the oxide layers promotes cracks on the anodized surface. Anodization of Zamak promotes better performance against corrosion, when compared to non-anodized samples, and this effect is attributed to the barrier effect of the oxides and the formation of corrosion products that fill the cracks generated during anodizing.

Since lithium salts were demonstrated to be very effective for the potential control of Varroa destructor, a highly detrimental parasite of honey bee (Apis mellifera), no studies have been reported on their comparison with any commonly used varroicides in commercial bee colonies. In this study we compared the effectiveness of lithium chloride to that of oxalic acid, a widely used miticide. The results of the present study confirm that lithium has superior efficacy to oxalic acid sublimation both as a main or a supplementary pre-wintering treatment at moderate infestation levels, restricted to certain pre-wintering conditions. Considering its easy implementation in apicultural practice and its twofold mode of action, trickling would be the preferred way of administration after the use of lithium salts as varroicides is authorised.

Fe(II)-driven transformation of schwertmannite can strongly impact the transport and redistribution of coprecipitated As in reducing acid sulfate soil (ASS)/acid mine drainage (AMD)-contaminated en...

This work reports a study of the extraction of iron (III) deeply from the chromium sulphate solution in which most of the iron was precipitated with oxalic acid. Di(2-ethylhexyl)phosphoric acid (P2...

The synthesis of alkali metal and copper(ii) 1-polyfluoroalkyl-4,4-dimethoxypentane-1,3-dionates is reported. The subsequent treatment of these compounds with oxalic acid or ethylenediaminetetraacetic acid disodium salt affords functionalized 1,3-diketones. The nature of the polyfluoroalkyl substituent was found to affect the conditions of the Claisen condensation and the stability of the acetal group in acidic medium.

Microparticles of CuO were obtained by thermal decomposition of copper(II) oxalate synthesized by pulse electrolysis of an oxalic acid solution with a sacrificial copper anode. Scanning electron microscopy showed that the particles are rectangular hexagon-shaped with a size of 0.2–5 µm and form complex irregular aggregates with a porous structure. The use of the water–dimethylformamide solvents with a volume ratio 1 : 1 is optimal to achieve the desired morphology of the product.

In recent years, transition-metal oxides (TMOs) have been long employed for aerobic oxidative desulfurization. However, the inherent bottlenecks, such as the low explosion of active sites, limit the application of bulk TMOs catalyst. In this study, V2O5 nanoparticles with oxygen vacancies were prepared in large-scale via facile ball milling strategy with adding oxalic acid as a reducing agent. The as-prepared catalysts exhibit remarkable sulfur removal for oils with different initial S-concentrations and different substrates. Sulfur removal could reach up to 99.7% (< 2 ppm) under the optimized reaction conditions. This work provides a feasible desulfurization strategy for fuel oils.

Iron coordination polymer, Fe(ox)(H2O)2 (H2ox = oxalic acid) nanorods were grown on a nickel foam (NF) collector via a one-step electrodeposition method, which can be directly used as a freestandin...

In the preparation process of magnesium-cobalt nano-ferrite powder (Mg0.1Co0.9Fe2O4) by sol–gel self-propagation method, the effect of complexing agent on the nanostructure and magnetic properties of ferrite is studied by changing the type of complexing agent (the complexing agent includes citric acid, oxalic acid, tartaric acid, glucose, and egg white). The XRD pattern of each sample has eight distinct characteristic peaks, and the number of the strongest peak in each map is one [i.e., (311) peak]. All these evidences can preliminarily indicate that the sample has a spinel structure. In addition, in the FTIR of the sample, it can be seen that there are several distinct characteristic peaks at 580 cm−1 (i.e., Fe–O peak, etc.) which can also prove the structural characteristics of the sample. In the SEM map, the sample can be seen to have an elliptical shape with a crystalline grain size between 28 and 50 nm. From this, we can guess that the complexing agent participates in the reaction and has a certain influence on the particle size of the sample. Elemental analysis showed that all the six samples prepared contained magnesium, cobalt, iron, and oxygen, and then we quantitatively analyzed the sample to find that the prepared sample was the target product. The BET test shows that a sample is prepared with glucose as the complexing agent, the specific surface area of it can be increased. The VSM data show that magnesium–cobalt ferrite powder with high saturation magnetization, residual magnetization, and coercivity can be prepared by selecting glucose as the complexing agent.

This study was formulated to synthesize the ZnO nanoparticles through acetate-based zinc salts with NaOH (ZnO-I) and Oxalic acid (ZnO-II) as reactants; sodium dodecyl sulfate (SDS) used as a stabil...

The present study evaluates the reductive leaching of indium from indium-bearing zinc ferrite using oxalic acid as a reducer in sulfuric acid solution. The effect of main factors affecting the process rate, including the oxalic-acid-to-sulfuric-acid ratio, stirring rate, grain size, temperature, and the initial concentration of synergic acid, was precisely evaluated. The results confirmed the acceptable efficiency of dissolving indium in the presence of oxalic acid. The shrinking-core model with a chemical-reaction-controlled step can correctly describe the kinetics of indium dissolution. On the basis of an apparent activation energy of 44.55 kJ/mol and a reaction order with respect to the acid concentration of 1.14, the presence of oxalic acid was found to reduce the sensitivity to temperature changes and to increase the effect of changes in acid concentration. Finally, the equation of the kinetic model based on the factors under study is presented.

Phosphorus (P) rich ash from biomass incineration is a potential promising alternative for non-renewable phosphate rock. This study considered the P recovery potential of poultry manure ash, sewage sludge ash and meat and bone meal ash through wet chemical extraction. X-ray diffraction analysis showed that these three ash types had a distinct P mineralogy. If inorganic acids were used for the extraction, the P extraction efficiency was not or only slightly affected by the P mineralogy. Contrarily, for the organic acids, alkaline extraction liquid and chelating agents considered, the P extraction efficiency was highly affected by the P mineralogy, and was also affected by the elemental composition of the ash and/or the chemical characteristics of the extraction liquids. Alkaline extraction liquids showed in general low heavy metal co-extraction, in contrast to the inorganic acids. From an economic point of view, of all extraction liquids considered, sulfuric acid was the most interesting to extract P from all three ash types. Oxalic acid could be a more sustainable option for P extraction from sewage sludge ash. In addition, extraction of poultry manure ash with ethylenediaminetetraacetic acid showed a relatively high P extraction efficiency combined with relatively low heavy metal co-extraction.

This work aims to develop a green method for the recovery of vanadium from spent contact process catalyst (SVC) with 6–7% V2O5. The efficiency of leaching was evaluated using oxalic acid by varying...

Geoactive fungi play a significant role in bioweathering of rock and mineral substrates. Monazite is a phosphate mineral containing the rare earth elements (REE) cerium, lanthanum and neodymium. Little is known about geomicrobial transformations of REE-bearing minerals which are also relevant to REE biorecovery from terrestrial and extra-terrestrial reserves. The geoactive soil fungus Aspergillus niger colonized monazite in solid and liquid growth media without any apparent growth inhibition. In a glucose-minerals salts medium, monazite enhanced growth and mycelium extensively covered rock particle surfaces, probably due to the provision of phosphate and essential trace metals. Teeth-like and pagoda-like etching patterns indicated monazite dissolution, with extensive precipitation of secondary oxalate minerals. Biomechanical forces ensued causing aggressive bioweathering effects by tunnelling, penetration and splitting of the ore particles. High amounts of oxalic acid (~46 mM) and moderate amounts of citric acid (~5 mM) were produced in liquid media containing 2% (wt./vol.) monazite, and REE and phosphate were released. Correlation analysis suggested that citric acid was more effective than oxalic acid in REE mobilization, although the higher concentration of oxalic acid also implied complexant activity, as well as the prime role in REE-oxalate precipitation.

Vanadium-based oxide is widely investigated as a zinc ion battery (ZIB) cathode due to its ability to react reversibly with Zn2+. Despite its successful demonstration, modification with simple molecules has shown some promise in enhancing the performance of ZIBs. Thus, this presents an immense opportunity to explore simple molecules that can dramatically improve the electrochemical performance of electrodes. Thus, the effect of CO2 modification is studied in this work by decomposing oxalic acid within a hydrated V6O13 framework. Based on the collective results, the presence of CO2 drastically lowers the relative energy of Zn2+ diffusion through the pathways by forming weak electrostatic interactions between OCO2 and Zn2+. This leads to an enlarged diffusion contribution, which consequently results in enhanced stability and better rate performance. The as-synthesized CO2-V6O13 electrode delivers one of the highest specific capacities reported for vanadium-based oxides of ca. 471 mAh g-1. Furthermore, an excellent cyclic stability of 80% capacity retention after 4000 cycles at 2 A g-1 is recorded for CO2-V6O13, which suggests the importance of simple molecules in the material framework toward the enhancement of ZIB cathode performance.

A scandium-based coordination polymer (Sc-CP), Sc(ox)1.5(H2O)2·4H2O (1) (H2ox = oxalic acid), with a two-dimensional (2D) layered structure was prepared by both hydrothermal synthesis and ultrasound-assisted heating methods using glutaric acid as a modulator. Then, the single crystal of 1 as a precursor was transformed into another 2D Sc-CP, Sc(ox)1.5(H2O)2·H2O (2), by increasing the temperature. Due to the difference in hydrogen bond interactions between the host framework and guest water molecules, 2 showed good tolerance to various solvents, while 1 exhibited poor stability even exposed in air. After activation, 2 could be used as a heterogeneous Lewis acid catalyst for two classic C–C bond formation reactions, the cyanosilylation reaction and Strecker reaction at room temperature, showing excellent catalytic activity and selectivity.

In this study we used a chemical solution method from oxalic acid (OX. acid) and zinc acetate (ZnAc) to prepare Zinc Oxide nanoparticles (ZnONPs) and Zinc Oxide nanoparticles doped with Chlorine (Cl:ZnONPs). The characterizations (FTIR, X-ray, SEM, TEM) of ZnONPs and Cl:ZnONPs were determined. Amylase inhibitors of ZnONPs and Cl:ZnONPs also were determined. SEM indicated that the ZnONPs and Cl:ZnONPs have an average particle size of 46.65 - 74.64 nm. TEM images of the ZnONPs and Cl:ZnONPs showed the round shaped. Compounds b, d and e exhibited significant inhibitory activity against amylase enzyme (from 69.21 ± 1.44 to 76.32 ± 0.78), respectively, and were comparable with that of acarbose (86.32 ± 0.63) at 1000 μg, thereby, projecting ZnONPs and Cl:ZnONPs as α-amylase inhibitors.

This study investigated the dissolution behavior of metals from chalcopyrite concentrate in a pressure reactor system in the presence of hydrogen peroxide by oxalic acid leaching. The fact that the compounds formed by copper and iron with oxalic acid had different dissolution coefficients showed that metals could be selectively extracted based on the leaching temperature. The effects of various leaching parameters on metal extraction in the autoclave system were investigated at different H2O2 concentrations (1-5 M), H2C2O4 concentrations (25-125 g/L), leaching temperatures (318-443 K) and leaching times (15-180 min). While iron and copper extraction as a result of 180 min of leaching with 5 M H2O2, 318 K and 100 g/L H2C2O4 was respectively 90.6% and 1.73%, 88.5% of copper and 2.11% of iron could be extracted as a result of 180 min of leaching with 3 M H2O2, 443 K and 100 g/L H2C2O4. The reversal of the copper and iron extraction dissolution behavior started after the leaching temperature of 378 K. In the XRD analysis of leach residues obtained at low leaching temperatures, CuC2O4 peaks were dominant, while at high temperature conditions, Fe2O3 peaks were dominant. (c) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

A highly practical method for C–CN bond formation by C–N bond cleavage on enaminones leading to the efficient synthesis of β-cyano enones is developed. The reactions take place efficiently to provide (E)-β-cyano enones with only a molecular iodine catalyst. In addition, the additional employment of oxalic acid enables the selective synthesis of (Z)-β-cyano enones.

The non-exchangeable potassium (NEK) is the major portion of the reserve of available K in soils and primary factor in determining soil K fertility. The kinetics of NEK release in 10 different soil types of Punjab having a wide range in available K was investigated by successive extraction with 0.01M oxalic acid over a period of 200 h. The cumulative amount of NEK release ranged between 86 and 253 cmol x 10−2 K kg−1 in different soils. The highest amount of NEK release (253 cmol x 10−2 K kg−1) was recorded in loamy sand soil from Mansa district and the lowest amount (86 cmol x 10−2 K kg−1) was recorded in soil from Gurdaspur district deficient in available K. Based on high coefficient of determination (R2) and low values of standard error of estimate, kinetics of NEK release from all the soils were adequately described by Elovich, First order, power and parabolic difusion models but Elovich was found the best ftted model because of highest R2 values, while zero order model was not suitable to describe NEK release.

The photoelectrochemical reduction of U(VI) is recognized as an economical and effective way to eliminate radioactive pollution. In this study, we construct a α-Fe2O3/TiO2 film electrode-based photoelectrochemical cell to remove U(VI) and recover uranium from aqueous solution. Citric acid and oxalic acid could act as hole scavengers, being favorable for the photocatalytic reduction of U(VI). In the presence of 0.5 mM citric acid and oxalic acid, the uranium removal capacity reached 70% and 58%, respectively, while 24% was achieved for the system in the absence of acid. The XRD, SEM, FT-IR and XPS results revealed that a proportion of U(IV) was also precipitated as surface associated metastudtite. These novel observations have significant implications for the behavior of uranium within engineered and natural environments.

In this study, CeOx with different exposed facets was prepared to investigate their potential effect on activating the peroxone reaction (H2O2/O3) and breaking through the restriction of solution pH on peroxone. By controlling the concentration of hydroxide, cube CeOx with a (100) facet, rod CeOx with a (110) facet and octahedron CeOx with a (111) facet were prepared by the hydrothermal precipitation method, and they all promoted heterogeneous peroxone for oxalic acid (OA) under acidic conditions. The catalytic activity of CeOx was highly related to their surface oxygen vacancies (OVs) and the interfacial electron transfer process. Both experiments and theoretical calculations showed that CeOx with different exposed facets activated peroxone in different ways and (111) CeOx possessed better activity than (100) or (110) CeOx. The low efficiencies of (100) and (110) CeOx were due to their inefficient use of H2O2 to reduce surface Ce4+ and their large energy gap to generate surface peroxide (OVs-OOH). (111) CeOx was stable with surface-adsorbed H2O2, and the rich electrons at OVs could be donated to H2O2 and generate OVs-OOH, which then triggered O3 decomposition into hydroxyl radical (˙OH) and superoxide radical (˙O2−). These electron migration processes depended on the electron-donating ability of the OVs rather than solution pH, therefore, still greater amounts of reactive species were generated under acidic conditions. The flexibility of the (111) CeOx/H2O2/O3 process was further investigated for removing 20 kinds of pharmaceuticals. The synergy effect of (111) CeOx/O3 and H2O2 varied with the structure of the pharmaceuticals.

It was found that Li[BOB]·nH2O salts were not readily suitable for the synthesis of high-purity orthoborate-based tetraalkylphosphonium ionic liquids, as exemplified here for trihexyl(tetradecyl)phosphonium bis(oxalato)borate, [P6,6,6,14][BOB]; along with [BOB]-, a metastable transition anionic complex (TAC) of dihydroxy(oxalato)borate with oxalic acid, [B(C2O4)(OH)2·(HOOC-COOH)]-, was also formed and passed into the ionic liquid in the course of the metathesis reaction with trihexyl(tetradecyl)phosphonium chloride. On the contrary, Na[BOB] was found to be a more suitable reagent for the synthesis of this IL, because [BOB]- anions safely passed into the final IL without hydrolysis, when metathesis reactions were performed using aqueous-free media. Since ultra-pure Na[BOB] is not commercially available, in this work, a preparation protocol for ultra-pure (>99%) Na[BOB] was developed: (i) molar ratios of boric and oxalic acids were optimised to minimise boron-containing impurities, (ii) the Na[BOB] product was thoroughly purified by sequential washing of a fine powder product in hot acetonitrile and ethanol and (iii) characterised using powder X-ray diffraction and solid-state 11B MAS NMR spectroscopy. The physico-chemical properties of the prepared boron-impurity-free IL, i.e., its density, viscosity, electric conductivity, glass-transition temperature and thermal stability, were found to be significantly different from those of the previously reported [P6,6,6,14][BOB], containing ca. 45 mol% of TAC, [B(C2O4)(OH)2·(HOOC-COOH)]-. It was found that a high-purity [P6,6,6,14][BOB] prepared in this work has a considerably lower viscosity, a higher viscosity index and a wider electro-chemical window (ECW) compared to those of the sample of [P6,6,6,14][BOB] with ca. 45 mol% of TAC. Interestingly, [B(C2O4)(OH)2·(HOOC-COOH)]- in the latter sample almost completely transformed into [BOB]- anions upon heating of the IL sample at 413 K for 1 hour, as confirmed using both 11B and 13C NMR. Therefore, in this work, apart from a well-optimised synthetic protocol for boron-impurity-free [P6,6,6,14][BOB], implications of boron-containing transition anionic complexes in tetraalkylphosphonium-orthoborate ILs used in different applications were highlighted.

Boron-modified high-ortho phenolic resins (BPRs) were prepared under normal pressure by using phenol and formaldehyde as raw materials, zinc acetate, and oxalic acid as catalysts, and boric acid as a modifier. Boron-modified phenolic fibers (BPFs) were prepared by melt spinning and curing in a mixture of formaldehyde and hydrochloric acid, followed by a heat treatment under high temperature. The structure, ortho–para ratio (O/P), molecular weight and distribution, spinnability, thermal stability, fiber strength, and morphology of the resins were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and fiber strength testing. The results showed that the addition of boric acid reduced the ortho reaction of the synthetic resin and the O/P value of phenolic resin. When the content of boric acid was 3 wt%, the thermal stability was the best, the O/P value was up to 3.26, and the weight average molecular weight (Mw) was 18745 g/mol. In Compared with the unmodified resin, the mass loss was increased by 33.7%, and finally the carbon yield was 51.2%. The tensile strength of the fibers reached 187.2 MPa and the elongation at break was 10.5%. By introducing boron into the molecular chain, the structure of the resin was improved, and the thermal stability and mechanical properties of the fibers were improved.

The influence of HCl and NaOH activation on kaolinite to synthesize acid and base activated kaolinite (AAK and BAK) as catalyst supports for nickel oxalate precursor synthesized via oxalic acid functionalization (OAF) was explored in the study. For comparison, another catalyst was synthesized via incorporation of nickel nitrate salt into the activated supports and the catalysts were calcined at 700 °C. The characterization results confirmed that while acid treatment reduced the crystallinity of Kaol, base treatment transformed Kaol into sodalite-zeolite according to the XRD and FESEM results. The Ni nanoparticle (NP) sizes on nickel supported on AAK (Ni/AAK-700) were nine times larger than Ni particle sizes on nickel supported on BAK (Ni/BAK-700) which itself is 1.42 times smaller than the Ni NP in oxalic acid-functionalized Ni supported on BAK (NiOL/BAK-700). The XPS Ni2p peak of Ni/BAK-700 was observed to shift towards higher binding energy signifying a higher degree of metal-support interaction with increased H2 reduction difficulty. A reversed phenomenon was observed for NiOL/BAK-700. The samples basicity followed the order Ni/BAK-700 > NiOL/BAK-700 > NiOL/BAK-800 > Ni/AAK-700, while the acidity followed the reverse. These results provide insights into modified Kaol supported Ni catalysis for various applications based on the required physicochemical properties.

The hydrometallurgical recycling of cerium from a secondary residue of exhausted auto-catalyst was investigated. Cerium dissolution was significantly improved up to 96% when HF was additionally introduced into a 2.0 mol/L H2SO4 solution. The activation energy (Ea, 31.8 kJ/mol) indicated the diffusion-controlled mechanism prevailed in cerium leaching. Subsequently, the leach liquor containing 4.2 g/L cerium was equilibrated with Cyanex 923 for solvating the post-extraction species $$ \left[ {{\text{Ce}}({\text{SO}}_{4} )_{2} .2\left( {\text{P {=} O}} \right).{\text{HSO}}_{4}^{ - } } \right]_{org} $$ into the organic phase. Thermodynamic properties revealed that the affinity of Cyanex 923 toward cerium was spontaneous (ΔG°298K, −6.58 kJ/mol) and exhibited outer-sphere coordination for the exothermic process (ΔH°, −21.42 kJ/mol). Furthermore, cerium was quantitatively stripped (> 98%) from the loaded organic using the strippant mixture of 1.0 mol/L H2SO4 + 0.5 mol/L H2O2. Eventually, high-purity Ce2(C2O4)3.10H2O was precipitated by adding oxalic acid at an optimized dosage of Ce3+:H2C2O4 = 1:5.

The next-generation positron zirconium-89 (89 Zr, T1/2 = 3.27 days) is a novel nuclide for immunological positron emission tomography because of its favorite longer half-life. The aim of this work is to develop optimized methods for routine production and purification of 89 Zr through Monte Carlo (MC) simulation and laboratory experiments. 89 Y(p,n)89 Zr reaction was used for 89 Zr production. Optimized thicknesses of Al degrader (0.11 cm) and 89 Y foil (0.064 cm) were simulated through MC method. 89 Zr (15.0-40.7 mCi) with an average production rate of 0.92 ± 0.12 mCi/μA·h was produced after 1- to 2-h bombardment at the proton beam energy of 20 MeV and current of 20 μA. High radio-purity 89 Zr (6.14-26.8 mCi) obtained eluted from hydroxamate resin using 1-mol/L oxalic acid solution, with the concentration of 2.7 × 104 mCi/L. The gamma spectrum showed that the characteristic peak of 89 Zr was 511 and 909 keV, and no impurities were found. [89 Zr]Zr-DFO-trastuzumab was successfully labeled and performed good radiochemical purity (>95%) and stability that showed potential application in tumor molecular imaging.

Recycling of industrial waste has become a process of highly positive impact on the environment, industry and human health. The management of the electric arc furnace dust (EAFD) is a necessary and interesting task due to the possible recovery of its elevated metallic content (Zn, Pb, Cu, etc.). This reduces the environmental pollution generated by the leachability of its heavy metals and produces new revenues for the steel industries. In this work, a hydrometallurgical route was studied to extract the zinc present in EAFD. The research carried out using two carboxylic acids: sodium citrate and oxalic acid at moderate concentrations (≤ 0.5 M). The effect of pH, molar concentration and stirring speed was analyzed. Under pressure and ambient temperature, after 3 h of leaching, the results showed that both agents can leach zinc from waste, reaching metal extractions of approximately 50%. The more stable franklinite (ZnFe2O4) and hematite (Fe2O3) phases were not decomposed under these mild conditions. Citrate was especially promising due to its selectivity for zinc.

In the present research Polyaniline (PANI) has been prepared by chemical polymerisation using oxalic acid (OA) as a dopant. Removal of Methyl Orange (MO), (Sodium 4-{[4-(dimethylamino) phenyl] diaz...

Thermochromic materials have attracted the attention of scientific and technological researchers due to their ability to change color depending on the temperature. Vanadium dioxide (VO2) is capable of considerable polymorphs and has aroused interest mainly because its metal–insulator transition (MIT) presents a thermochromic characteristic at a relatively low temperature. This work aimed to obtain vanadium oxide nanostructures using hydrothermal synthesis to tune the MIT temperature. Ammonium metavanadate or vanadium pentoxide was used as a precursor of vanadium, oxalic acid as a reducing agent, and sodium molybdate as an additive. The starting materials were homogenized and inserted in a hydrothermal reactor at 180 °C. After 24 h of synthesis, part of the resulting product was heat-treated at 400 °C for 3 h. The powders obtained were characterized by their structure, morphology, and thermal properties. The results showed a fiber/rod-shaped VO2 (M) morphology. Distinct strategies were used to obtain the crystalline phase of interest (VO2(M)), and the presence of a reversible change occurring at ~68 °C was evaluated according to the parameters from the VO2 phase transition. The addition of sodium molybdate favored a 22% reduction in the MIT temperature when the precursor used was vanadium pentoxide, indicating possible doping in the structure increased the effects of smaller crystallite size and the presence of crystalline phases. This work opens new perspectives for applications of the vanadium oxides obtained, such as in thermal sensors and/or intelligent materials.