Adsorption of methyl orange using different viscosity chitosan/graphene oxide/gelatin hydrogel beads in wastewater.

Chitosan (CS) demonstrates significant potential in addressing water contamination challenges. In this study, high viscosity (H-CS, >583 kDa), medium viscosity (M-CS, 265-583 kDa), and low viscosity (L-CS, <265 kDa) of chitosan (CS) were used. Prepared graphene oxide (GO) and gelatin via a neutralization-precipitation method. CSGO hydrogel beads was developed through crosslinking CS and GO composite using glutaraldehyde as a linking agent. Furthermore, the adsorption performance of the hydrogel beads for methyl orange (MO) was investigated. Component ratio analysis showed that at a GO to CS mass ratio of 1:10, the adsorption capacity of CSGO hydrogel beads increased by 18 % compared to CS hydrogel beads. CSGO hydrogel beads with different viscosities exhibited variations in pore size and porosity. Under the optimal conditions(pH 3, 60 °C, 10 mg/L MO concentration, 20 mg adsorbent), H-CSGO, M-CSGO, and L-CSGO achieved the maximum adsorption capacity of 257.20 mg/g, 238.87 mg/g and 242.68 mg/g, respectively. Adsorption kinetic followed the pseudo-second-order model and the Freundlich isotherm model, with adsorption governed by both intra- and external diffusion control steps. The primary mechanisms involved electrostatic attraction, hydrogen bonds, n-π interactions, and π-π stacking.