Synthesis of a functional biomass lignin-based hydrogel with high swelling and adsorption of Acid Red 73

In this study, sodium lignosulfonate (LS) was used as raw material, acrylamide (AM) and acryloyloxye thyltrimethyl ammonium chloride (DAC) as monomers, and N,N'-methylenebisacrylamide (MBA) as cross-linking agent, the potassium persulfate (KPS)/tetramethylethyl enediamine (TEMED) as oxidation/ reduction initiation system. Synthesis of a functional biomass terpolymer lignin-based hydrogel adsorbent (LAD) with excellent adsorption properties by free radical graft copolymerization. The structure and properties of the prepared LAD were characterized by FT-IR and SEM, and the relationship between structure and properties was studied. The effects of solution pH, adsorption time, hydrogel dosage, initial concentration of dye and temperature on the adsorption of AR 73 by LAD were investigated. LAD adsorbed AR 73 solution with initial concentration of 100mg/L for 2h to reach equilibrium, with equilibrium adsorption capacity and adsorption rate of 47.59mg/g and 95.18%, respectively. The prepared LAD hydrogel has good swelling and deswelling properties, the swelling ratio of water absorption for 2h was 25g/g, and the water loss rate of 120 min in ethanol solvent was 93.51%. The adsorption of AR 73 by LAD was consistent with the Langmuir isothermal adsorption model. It was single-molecule adsorption with a maximum adsorption capacity of 409.84mg/g. The adsorption was a process of spontaneous heat release and entropy reduction.The adsorption kinetics was in accordance with Pseudo-second-order kinetic equation, and the adsorption activation energy was 2.501 kJ/moL. In addition, the mechanism of adsorption is mainly electrostatic, and there are also comprehensive effects of physical, chemical adsorption and hydrogen bond.The LAD hydrogel adsorbent has a significant adsorption effect on AR 73, and can be used as an efficient and recyclable biomass adsorbent for the treatment of anionic dye wastewater.