Bimetallic oxide integrated chitosan matrix for adsorption coupled reduction of Cr(VI) from aqueous solution

Abstract

In an aqueous environment, chromium is often recognized as a toxic oxyanion that poses a significant threat to living organisms because of its carcinogenic nature. The removal of hexavalent chromium (Cr(VI)) from an aqueous medium is essential to protect the environment and human health. This investigation explores the elimination of Cr(VI) ions from water by employing an adsorption technique utilizing a biopolymeric hybrid composite consisting of copper-incorporated lanthanum oxide@Chitosan (Cu_xLa_2-xO₃@Chi). The as-prepared materials were comprehensively analyzed using SEM, EDX, FTIR, XRD, BET, TGA, and XPS analysis. A systematic approach was used to optimize the batch adsorption parameters in order to ensure the maximum adsorption capacity of prepared adsorbent materials. The prepared Cu_xLa_2-xO₃@Chi composite exhibited a prominent adsorption capacity of 123.45 mg/g at pH 4.0 within 120 min. Adsorption kinetics and isotherm studies reveal that the adsorption of Cr(VI) process follows pseudo-second-order kinetics and Langmuir isotherm models, respectively. This suggests that the adsorption process occurs in a monolayer formation and involves a chemisorption mechanism. Mechanistic investigations reveal that the synergistic effect of electrostatic attraction, surface complexation, and adsorption-coupled reduction mechanism enhanced the adsorption of Cr(VI) ions from aqueous media. The selectivity and stability of the Cu_xLa_2-xO₃@Chi composite were investigated through competing and reusability experiments. The findings demonstrated outstanding selectivity in the presence of various competing ions and maintained good stability over five consecutive cycles. Therefore, the prepared Cu_xLa_2-xO₃@Chi composite proved outstanding adsorption ability against Cr(VI) ions and can be used as a technological reference in real-world water treatment.