Novel hydrogel based on natural hybrid backbones: optimized synthesis and effective adsorbent for the removal of malachite green dye from an aqueous solution

In this work, we synthesized a novel hydrogel based on poly(acrylamide) grafted Guar/locust bean gums, i.e. (GG/LBG-g-poly(AAm)) through free radical polymerization, aiming for the removal of malachite green (MG) dye from aqueous solutions. Response surface methodology and a full factorial rotatable central composite design were used to optimize various reaction parameters, enhancing the percentage swelling of the synthesized hydrogel. This optimization resulted in a notable increase in swelling capacity, reaching 1050%. The incorporation of acrylamide chains onto the guar/locust bean gum-based hybrid backbone, as well as crosslinking between different polymeric chains, was confirmed through various characterization techniques, including FTIR, TGA, XRD, FE-SEM, wettability studies, and zeta potential analysis. We evaluated the synthesized hydrogel adsorption performance for MG under specific conditions: pH (7.0), contact time (300 min), adsorbent dose (0.08 g), and dye concentration (50 mg/L). Under ambient conditions, GG/LBG-g-poly(AAm) demonstrated a maximum adsorption capacity of 52.96 mg g⁻¹, achieving a removal efficiency of 98%. The Freundlich model best described the adsorption data and followed pseudo-second-order kinetics, indicating a consistent agreement. Furthermore, the Dubinin-Radeshkovich isotherm and Elovich model perfectly depicted the chemisorption nature of the adsorption process. The synthesized GG/LBG-g-poly(AAm) demonstrates significant potential for effectively removing toxic dyes from wastewater.