Evaluation of Cr (VI) Ion Removal from Aqueous Solution by Bio-Inspired Chitosan-Clay Composite: Kinetics and Isotherms

This paper reports the evaluation result of adsorbing Cr (VI) ions on sorbent prepared from chitosan (CHT), a versatile derivative of chitin, and dodecyl amine modified locally available kaolinite clay (Bijoypur clay) (MC) that has excellent mechanical properties and great resistance to chemical and biological attack. The effect of the initial metal ion concentration, solution pH, contact time, and adsorbent dosages on the adsorption capacity of the composites was investigated. pH of 4 was selected for better adsorption by the adsorbents. The adsorption abilities were studied over Cr (VI) ions using different adsorption isotherms such as Langmuir, Freundlich, and Dubinin-Radushkevich, respectively. Langmuir isotherm is found better fitted with maximum adsorption capacity of 73 mg/g by composite SB-1. R2 obtained from Langmuir isotherm is 0.999, which indicates a monolayer adsorption on the adsorbent surface. The adsorption kinetics was also well described by the pseudo-second-order equation with a rate constant of 0.000302 gmg^−1min^−1 at 25 ppm Cr (VI) concentration. The adsorption of Cr (VI) ions by the adsorbent was confirmed by FT-IR and X-RD analysis of the composites before and after Cr (VI) ion adsorption. The desorption percentage of the metal ion and the second cycle metal adsorption by the regenerated (regenerated after the first adsorption by fresh adsorbent) adsorbent processed with 0.01N sulphuric acid show values of 78.23 % and 68.12 %, respectively.