Chitosan-Modified Bentonite for the Adsorptive Removal of Three Organic Dyes: A Comprehensive Experimental and Theoretical Investigation

Chitosan has significant advantages due to its good biocompatibility and biodegradability. However, the original chitosan often has problems such as limited adsorption capacity and poor selectivity. Therefore, modifying chitosan to improve its adsorption performance has become an important research direction. This study adopted molecular dynamics simulations to explore the factors influencing the physical modification of chitosan and further conducted adsorption experiments with three different dyes. The results indicated that when combined with different clays, the interaction between chitosan and montmorillonite was more likely to occur, making it a suitable adsorbent for physical modification. As the molecular weight (MW) of chitosan increased, the <500 MW chitosan-modified bentonite exhibited the maximum adsorption capacity for different dyes, with the adsorption rates of 90.73% (methylene blue), 72.05% (methylene orange), and 32.28% (cresol red) at 20 mg/L, respectively. The adsorption kinetic and thermodynamic analysis indicated that the adsorption process is consistent with the pseudo-second-order kinetic model (R2 > 0.99004), while lower temperature was more conducive to the adsorption process. The results would help determine the optimum synthetic conditions for chitosan-based composite materials and make positive contributions to the green development of agriculture.