Adsorption behavior and mechanism of amine/quaternary ammonium lignin on tungsten

Amine/quaternary ammonium lignin for adsorption of tungsten was synthesized by amination and quaterniza-tion from lignin. The adsorbent was characterized by SEM-EDS and FTIR. The effects of pH, initial concentration of tungsten, adsorption time and dosage of adsorbent on the adsorption effect were investigated. The adsorption mechanism was revealed by SEM-EDS and FTIR and XPS. The results showed that amine/quaternary ammonium lignin was loose and rough and contained a large number of phenolic hydroxyl and amine and quaternary ammonium functional groups. Using the optimum conditions, which included the pH of 4.0 and initial tungsten concentration of 800 mg.L-1 and adsorption time of 960 min, the saturated adsorption capacity of 1 g.L- 1 amine/quaternary ammonium lignin for tungsten reached 421.68 mg.g- 1. The adsorption followed Langmuir model and quasi-second-order kinetic model, indicating that the adsorption was monolayer homogeneous chemisorption. When the total concentration of tungsten was 0.005 mol.L-1 and the value of pH was smaller than 4.7, H2W12O40 6-was the existing form of tungsten and was adsorbed by electrostatic attraction of hydrogen bond and coordination with amino and ion exchange with Cl-.

Automated summary

Amine/quaternary ammonium lignin was synthesized and used as an adsorbent for tungsten. The adsorption mechanism was studied, and the optimal conditions for adsorption were determined. The results showed that the adsorption followed Langmuir model and quasi-second-order kinetic model, and the adsorption mechanism involved electrostatic attraction and coordination with amino and ion exchange. The findings provide important insights into the adsorption of tungsten using amine/quaternary ammonium lignin.