Adsorptive removal of anionic dyes using magnetic hydrogel based on almond gum-grafted-poly (acrylamide) crosslinked N, N'-methylene bis acrylamide: Kinetics, isotherm, and thermodynamic insights.

Dye effluents form a significant amount of textile industry wastewater. Zero liquid discharge norms for the textile industry make it compulsory to treat these effluents and reuse them for the next batch. The present work aimed at the effective removal of congo red (CR) and aniline blue (AB) dyes by treating them with an almond gum-based novel magnetic hydrogel (Amg-g-PAM-cl-MBA/Fe₃O₄). The magnetic hydrogel showed a saturated magnetization value of 6.32 emu/g, suggesting ferromagnetic behaviour. Various factors, including concentrations of dye solution, dosages, pH, temperature, and contact time, were analyzed to assess its performance. Later, the 94.92 and 92.54% removal was achieved for CR and AB dye, respectively. The maximum adsorption capacity (qmax) of CR and AB was 301.20 and 177.62 mg/g, respectively, using the Langmuir model. The best fit of adsorption kinetics was for pseudo-second-order (R2 = 0.998 and 0.991), suggesting chemisorption. While the thermodynamics data suggest the adsorption process is endothermic and spontaneous, the incorporation of Fe₃O₄ into the hydrogel improves the reuse and recyclability aspects. The developed magnetic hydrogel can be applied directly to textile waste effluents for dye remediation.