Cross-linked chitosan/pencil clay hybrid beads for the adsorption of reactive black 5

Chitosan (CH) and pencil clay (CL) were utilized to prepare stable epichlorohydrin cross-linked chitosan-clay hybrid beads (CCHB) for the adsorptive removal of anionic reactive black 5 (RB5) dye. Among various percentage weight ratios of chitosan/clay hybrid beads, 40 % CH-60 % CL was selected as the best adsorbent owing to its stability and removal efficiency. The pore properties of CCHB in terms of surface area, total pore volume, and average pore width were 40.33 m²/g, 0.088 cm³/g, and 86.06 Å, respectively. The adsorption behavior of RB5 on CCHB followed Langmuir and pseudo-second-order models. Thermodynamic parameters confirm the endothermic and spontaneous nature of RB5 adsorption and the regeneration studies reveal a negligible decrease in removal efficiency of CCHB after 5 adsorption-desorption cycles. The CCHB exhibited adsorption capacities of 169.49, 200.00, and 227.27 mg/g for RB5, respectively, at 30, 40, and 50 °C. The prepared chitosan-clay hybrid bead adsorbent can be efficiently applied for anionic wastewater treatment.