In situ preparation of MIL-100(Fe) loaded sodium humate/guar gum hydrogel adsorbents: Green and efficient adsorption of heavy metals and dyes in water.

Sodium humate (SH)/guar gum (GG)@MIL-100 (Fe) composite hydrogel absorbent was successfully prepared by combining free radical polymerization and in-situ growth technology, which was subsequently applied to remove Cu, methylene blue (MB) and malachite green (MG) from wastewater. In this study, the effects of adsorption time, solution pH, adsorbent quality and initial concentration of pollutants on the adsorption performance of SH/GG@MIL-100 hydrogel were investigated. The adsorption process and rate-limiting steps involved in the removal of pollutants by SH/GG@MIL-100 were scrutinized using a multifaceted approach that encompassed the Langmuir isotherm model, Freundlich isotherm model, pseudo-first-order and pseudo-second-order kinetic models, along with the intraparticle diffusion kinetic model. The maximum adsorption capacity of Cu, MB and MG by SH/GG@MIL-100 can reach 311.48 mg g, 834.16 mg g and 794.45 mg g, respectively. The adsorption process involves many mechanisms such as hydrogen bonding, electrostatic attraction, surface complexation and π-π conjugation.