Fabrication and characterization of fenugreek-g-poly(acrylic acid) hydrogel for effective adsorption of crystal violet dye

In this study, an FG-g-poly(AA) hydrogel was synthesized by polymerizing acrylic acid onto fenugreek gum (FG) using MBA as a crosslinker and APS as an initiator in a hot air oven. The RSM-CCD model was employed to optimize various parameters, including the amounts of monomer, crosslinker, and initiator. The prepared hydrogel was characterized using FTIR, XRD, FE-SEM, TGA, and BET to confirm its crosslinked network, morphology, thermal stability, and surface charge. The hydrogel’s surface area, pore volume, and pore diameter were determined to be 16.332 m²/g, 0.046 cc/g, and 3.712 nm, respectively. Adsorption studies were conducted under various conditions, with different initial dye concentrations, temperatures, and pH levels. Under optimal conditions, the hydrogel achieved a maximum dye removal capacity of 97.3% for crystal violet (CV) dye within 6 h. The Langmuir isotherm model fitted the data well, and the maximal capacity for CV adsorption was 925.9 mg/g. A negative ΔG value indicates the feasibility and spontaneity of the adsorption process, while a positive ΔH suggests that the adsorption was endothermic. Thus, the synthesized hydrogel is an excellent candidate for eliminating CV dye from wastewater solutions.