Kinetic and isotherm studies of cr (VI) adsorption from aqueous media by using a synthetic chitosan-allophane nanocomposite

This study investigates Cr (VI) removal from an aqueous solution by a synthetic chitosan-allophane nanocomposite. The nanocomposite was synthesized using the solvothermal method. The adsorbent was characterized utilizing X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) images, and the Brunauer-Emmet-Teller (BET) method. This work investigated the influence of the solid/liquid ratio, pH, contact time, and initial concentration on the adsorption process, as well as the adsorption kinetics and isotherms. The maximum adsorption capacity of the synthetic nanocomposite for Cr (VI) is 112.17 (mg/g) under optimum conditions. The kinetics study shows that the pseudo-second-order kinetic equation better describes the adsorption behavior of the adsorbent. The isotherms study suggests that the adsorption process of the synthetic chitosan-allophane nanocomposite follows the Langmuir model. Freundlich isotherm shows a better fit to the process with R² = 0.97 and Freundlich constant of 42.9 L/g. The adsorption of Cr (VI) ions on adsorbent well fits to pseudo-second-order with qe: 125 mg/g. Moreover, the stability and reproducibility of the synthetic nanocomposite were investigated. This study presents a approach for synthesizing high surface area, engineered morphology, reusable, and stable nanocomposite for effectively adsorbing heavy metal ions from wastewaters.