Showing papers on "Oxalic acid published in 2022"

Dye removal from aqueous solution using nanocomposite synthesized from oxalic acid-modified agricultural solid waste and ZnFe2O4 nanoparticles

Abstract: Batch adsorption experiments were carried out to eliminating Congo red (CR) and methylene blue (MB) from aqueous solution using oxalic acid-modified jujube shells of Ziziphus lotus (OA-JS)/ZnFe2O4(OA-JS@ZnFe2O4) nanocomposite as a high efficient adsorbent. The Fourier transform infrared (FTIR), Brunauer Emmett Teller, thermogravimetric analysis–differential scanning calorimetry, scanning electron microscope, transition electron microscope, and X-ray diffraction techniques were used to characterize the OA-JS@ZnFe2O4. The equilibrium data fitted to Langmuir isotherm and the maximum adsorption capacities were determined as 980.39 mg g−1 and 476.18 mg g−1 for CR and MB, respectively. The pseudo-second-order model could be best described the sorption kinetics. The calculated thermodynamic suggests that the CR and MB adsorption on OA-JS@ZnFe2O4 is spontaneous and endothermic. The OA-JS@ZnFe2O4 recycled, and the removal CR and MB were 82.08% and 76.59% after seven cycles, respectively. The synthesis of OA-JS@ZnFe2O4 nanocomposite showed excellent potential adsorbent for dye removal from wastewaters.

Facet-Dependent Activation of Oxalic Acid over Magnetic Recyclable Fe3S4 for Efficient Pollutant Removal under Visible Light Irradiation: Enhanced Catalytic Activity, DFT Calculations, and Mechanism Insight.

Abstract: Photo-Fenton-like reaction based on oxalic acid (OA) activation is a promising method for the fast degradation of pollutants due to the low cost and safety. Hence, the magnetic recyclable greigite (Fe3S4) with the exposed {011} facet (FS-011) was prepared using a facile one-pot hydrothermal method and activated OA under visible light irradiation for pollutant removal, in which the removal efficiency values of FS-011 for metronidazole (MNZ) and hexavalent chromium were 2.02 and 1.88 times higher than that of Fe3S4 with the exposed {112} facet, respectively. Density functional theory calculations revealed that OA was more easily adsorbed by the {011} facet of Fe3S4 than by the {112} facet, and the in situ-generated H2O2 preferred to diffuse away from the active sites of the {011} facet of Fe3S4 than from that of the {112} facet, which was conducive to the continuous adsorption and efficient activation of OA. Moreover, the analyses of Fukui index and dual descriptor confirmed the degradation mechanism that the imidazole ring of MNZ was easy to be attacked by electrophilic species, while the amino group of MNZ was easy to be attacked by nucleophilic species. These findings deeply analyzed the mechanism of enhanced OA activation by facet engineering and consolidated the theoretical basis for practical application of Fenton-like reactions.

Organosolv pretreatment of oat husk using oxalic acid as an alternative organic acid and its potential applications in biorefinery

Abstract: Abstract In this study, ethanol organosolv treatment of oat husk and the potential effects of phosphoric acid and oxalic acid as alternatives to sulfuric acid were investigated. These acids were determined as effective as sulfuric acid to obtain high quality lignin and glucan and they can be used instead of sulfuric acid in solvent acidification. To determine the purity and recovery of both lignin and glucan, the effects of initial substrate amount, solid-to-liquid ratio, and amount of washing solutions were also examined using a one-factor-at-a-time strategy. Reducing the amount of washing solutions (water, solvent, or both) negatively affected lignin recovery, but it did not affect glucan recovery. The optimum conditions for pretreatment of the oat husk at higher glucan recovery were obtained with 50% aqueous ethanol acidified with oxalic acid at 210 °C for 90 min and solid-to-liquid ratio of 1:2. In the mixture of evaporated glucan-rich and hemicellulose-rich fractions obtained through the optimized condition, 4.62 g/L biomass containing 10.27% protein was produced by the cultivation of Aspergillus oryzae . The fractions obtained from organosolv treatment can be used to obtain value-added products such as biomass production, and thus contributing to a sustainable economy by integrating lignocellulosic substrate residues into the biorefinery.

Magnetically separable NiFe2O4/Sepiolite catalyst for enhanced ozonation treatment of quinoline and bio-treated coking wastewater in a catalytic ozonation system

Abstract: In a quest to eliminate the bio-refractory organic pollutants in industrial wastewater , the NiFe 2 O 4 /SEP composites were synthesized via a sol-gel method and investigated by XRD, SEM, XPS , FTIR, VSM. The TOC removal increased from 16.82% to 69.35% in NiFe 2 O 4 /SEP+O 3 system using quinoline as a target contaminant after 30 min, which is about 4.12 times as that in O 3 system. The evolution of acetic acid, oxalic acid and formic acid in quinoline degradation was analyzed, saturated carboxylic acids were inertia to ozone molecules. However, 93.54% of oxalic acid was removed after 10 min, and 77.66% of acetic acid was degraded after 30 min in catalytic ozonation . The generation of small molecular organic acids could promote the Fe 3+ /Fe 2+ redox cycle by complexing with Fe 3+ on NiFe 2 O 4 /SEP, and then accelerated the formation of reactive oxygen species . In the presence of NiFe 2 O 4 /SEP, the high oxidation potential of •OH and •O 2 - contributed to an excellent TOC removal rate. Meanwhile, NiFe 2 O 4 /SEP was proved to be active for bio-treated coking wastewater in catalytic ozonation. The naturally fluorescent constituents in bio-treated coking wastewater were almost entirely removed by NiFe 2 O 4 /SEP+O 3 system in 60 min. These findings indicated the good potential of NiFe 2 O 4 /SEP for practical applications in industrial wastewater treatment .

Increasing Heavy Metal Tolerance by the Exogenous Application of Organic Acids

Abstract: Several metals belong to a group of non-biodegradable inorganic constituents that, at low concentrations, play fundamental roles as essential micronutrients for the growth and development of plants. However, in high concentrations they can have toxic and/or mutagenic effects, which can be counteracted by natural chemical compounds called chelators. Chelators have a diversity of chemical structures; many are organic acids, including carboxylic acids and cyclic phenolic acids. The exogenous application of such compounds is a non-genetic approach, which is proving to be a successful strategy to reduce damage caused by heavy metal toxicity. In this review, we will present the latest literature on the exogenous addition of both carboxylic acids, including the Kreb’s Cycle intermediates citric and malic acid, as well as oxalic acid, lipoic acid, and phenolic acids (gallic and caffeic acid). The use of two non-traditional organic acids, the phytohormones jasmonic and salicylic acids, is also discussed. We place particular emphasis on physiological and molecular responses, and their impact in increasing heavy metal tolerance, especially in crop species.