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

In this study, sodium lignosulfonate (LS) was used as raw material. Acrylamide (AM) and acryloxyethyltrimethylammonium chloride (DAC) were grafted onto LS through the free radical graft copolymerisation to synthesise a functional biomass terpolymer lignin-based hydrogel adsorbent (LAD). The effects of different factors on the LAD adsorption of Acid Red (AR 73) were investigated through the static adsorption method. LAD adsorbed AR 73 (C₀=100mg·L^-1) for 2 h to reach equilibrium, and the equilibrium adsorption capacity and removal rate were 47.59 mg·g^-1 and 95.18%, respectively. The prepared LAD hydrogel swelling ratio for 2 h was 25 g·g^-1, and the water loss rate in ethanol solvent in 120 min was 93.51%. The adsorption of AR 73 by LAD was consistent with the Langmuir isotherm adsorption model. This adsorption was a single-molecule adsorption with a maximum adsorption capacity of 409.84 mg·g^-1. The adsorption was a process of spontaneous heat release and entropy reduction. The adsorption kinetic was in accordance with the pseudo-second-order model, and the adsorption activation energy was 2.501 kJ·moL^-1. Moreover, the mechanism of adsorption was electrostatic attraction, and comprehensive effects of physical, and chemical adsorption and hydrogen bond. The LAD hydrogel adsorbent has a remarkable adsorption effect on AR 73, and can be used as an efficient and recyclable biomass adsorbent for the treatment of anionic dye wastewater.