Response surface methodology-based modeling and optimization of fenugreek gum-based hydrogel for efficient removal of malachite green dye

•The novel synthesis of SDS-g-poly (AA) hydrogel was done for the first time using RSM.•Hydrogel's qmax can reach up to 137.74 mg g−1 and 373.13 mg g−1 for MG and MB.•Hydrogen bonding and electrostatic interactions controlled the adsorption mechanism.•Adsorption data indicated the favorable, spontaneous, and exothermic nature of adsorption.•SDS-g-poly (AA) hydrogel showed excellent reusability and recyclability potential. This research work describes the synthesis of a fenugreek gum (FG)-based hydrogel (FG-g-poly(AAm)) via free radical polymerization for the removal of malachite green (MG) dye from an aqueous solution. The effects of various parameters such as backbone amount, initiator, monomer, cross-linker, and solvent on the percentage swelling were investigated using a 2-level-5-factor central composite half fraction design as an experimental design for response surface methodology. The model was found to be significant with a maximum percentage swelling of 1360%. The formation of a crosslinked network was validated by FTIR, TGA, XRD, BET, and FE-SEM characterization techniques. The surface area and average pore radius of the prepared FG-g-poly(AAm) were found to be 0.695 m2/g and 18.124 Å, respectively. The synthesized FG-g-poly(AAm) hydrogel was examined for the adsorption of MG dye from an aqueous solution as a function of time, pH, adsorbent dose, initial dye concentration, and temperature. The prepared hydrogel showed a maximum sorption capacity of 585 mg/g, as confirmed by pseudo-2nd-order kinetic and Langmuir adsorption models, revealing adsorption's chemisorption nature. The positive values of ΔHo and ΔSo showed that an endothermic process accompanied the adsorption process and had an affinity for dye molecules. The synthesized hydrogel can be used as a candidate for cationic dye removal.