Adsorption Effect of Oxalic Acid-Chitosan-Bentonite Composite on Cr6+ in Aqueous Solution

• Published in: Water, air, and soil pollution air, and soil pollution, 2023-08, Vol.234 (8), p.540, Article 540
• Main Authors: Huang, Chong, Ma, Qiang, Zhou, Man, Wang, Jinfeng, Feng, Zhigang
• Format: Article
• Language: English
• Subjects: Adsorption; Aqueous solutions; Atmospheric Protection/Air Quality Control/Air Pollution; Attraction; Bentonite; Chitosan; Climate Change/Climate Change Impacts; Earth and Environmental Science; Environment; Environmental monitoring; Experimental data; Gels; Hydrogeology; Ions; Isotherms; Kinetics; Oxalic acid; pH effects; Removal; Soil Science & Conservation; Thermodynamics; Water analysis; Water Quality/Water Pollution; Water sampling; X ray photoelectron spectroscopy
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-023-06543-x

In this paper, a gel adsorption material (CS@OB) was prepared by compounded oxalic acid modified bentonite with chitosan, which was used to remove Cr 6+ from aqueous solution. Batch adsorption was carried out under different experimental conditions, such as pH value, adsorption dose, Cr 6+ concentration, temperature, time and coexisting ions, to evaluate the adsorption effect of CS@OB. The experimental data were fitted and analyzed by adsorption kinetic model, adsorption isotherm model, and adsorption thermodynamic, and the structure and adsorption mechanism of CS@OB were characterized by SEM–EDS, FTIR and XPS. The results showed that pH had a great influence on the removal of Cr 6+ by CS@OB, and the removal efficiency could reach above 99% when pH was 2–3. According to the fitting results of adsorption isotherms (Langmuir and Freundlich), adsorption kinetics (pseudo-first-order and pseudo-second-order) and adsorption thermodynamics, Langmuir isotherm model and pseudo-second-order kinetic model were more suitable for experimental data. The adsorption mechanism was spontaneous and endothermic monolayer chemical adsorption, and the maximum adsorption capacity could reach 111.47 mg·g −1 . The adsorption of Cr 6+ by CS@OB mainly included electrostatic attraction and redox. Nitrogen-containing groups were protonated with positive charge, which effectively combined with Cr 6+ (HCrO 4 − /Cr 2 O 7 2− ) in solution through electrostatic attraction. Therefore, CS@OB can be used as an effective adsorbent to remove Cr 6+ ions from water samples.