Fabrication of in situ metal-organic framework grown on sodium lignosulphonate hydrogel for removal of Pb2+, methylene blue and crystal violet from aqueous solution

In this study, the metal-organic framework (MOF) was successfully compounded with lignosulfonate/diethylenetriaminepentaacetic acid (SLS/DTPA) hydrogels adsorbent using an assembly strategy that combined free radical polymerization and in-situ growth. The SLS/DTPA@ZIF-8 adsorbent exhibited excellent performance in removing heavy metal ions (Pb2+) and cationic dyes (methylene blue, MB and crystal violet, CV) from wastewater. To determine the maximum adsorption capacity, various influencing factors such as contact time, initial concentration of contaminant solution, adsorbent dosage and pH of solution were systematically discussed. The maximum adsorption capacities of Pb2+, MB and CV were calculated from Langmuir isotherm model to be 1021.85, 890.90 and 827.54 mg g−1, respectively (C0 (Pb2+) = 100 mg L−1, C0 (MB) = C0 (CV) = 25 mg L−1, pH = 6 ± 0.2, dosage = 0.2 g L−1 and T = 298K). The results of adsorption kinetic and isotherm experiments indicate that the pseudo-second-order and Langmuir isotherm models are most appropriate for describing physical and chemical adsorption processes occurring simultaneously. The XPS results confirmed that functional groups containing O and C were involved in the interaction of hydrogen bonding and electrostatic attraction between pollutants and hydrogel adsorbents. Additionally, the adsorbent's regeneration capabilities were studied. Five regeneration cycles later, the adsorbent still had good adsorption performance for the target pollutant. Overall, the present study shows a low-cost, green and efficient hydrogel adsorbent that exhibits remarkable efficacy in removing Pb2+ and dye from aqueous solutions.