Biosorption of rhodamine B and sunset yellow dyes on cross-linked chitosan-alginate biocomposite beads: Experimental and theoretical studies

This research explores the biosorption of Rhodamine B (Rd-B) and Sunset Yellow (SY) dyes using cross-linked chitosan-alginate (Ch-A) biocomposite beads, combining experimental investigations with theoretical studies to elucidate the biosorption mechanisms. The biocomposite beads were synthesized through an eco-friendly cross-linking method, and their structural properties were characterized using various characterization techniques. Complementary theoretical studies using Monte Carlo (MC) simulations and molecular dynamics (MD) calculations provided insights into the molecular interactions between the dyes and the biocomposite beads. ChA maximal biosorption capacity for Rd-B and SY was determined using the Langmuir model to be 43.6 mg g- 1 and 25.1 mg g- 1, respectively. Kinetic analysis elucidated that the biosorption process for Rd-B followed the pseudo first order (PFO) model and SY followed the pseudo second order (PSO) model. According to the thermodynamic characteristics, Rd-B and SY adsorb spontaneously and endothermically on Ch-A. In conjunction, MC and MD calculations were applied to probe the interactions between Rd-B and SY molecules and the Ch-A biocomposite beads, providing compelling evidence of robust binding interactions such as hydrogen bonds, electrostatic attractions, and it-it interactions. These theoretical insights were subsequently aligned with empirical observations, affirming a significant relation between the theoretical and experimental data. This study highlights the significance of combining experimental data with theoretical models to advance the development of environmentally friendly materials for water purification.