High efficient adsorption of W(VI) with a novel lignin-based biosorbent functionalized with Zn²⁺ and polyamine

Functionalized lignin-based biosorbent has become popular in wastewater treatment and extraction of valuable metals. Amination and metallization modification can effectively improve the adsorption performance of adsorbent. Zn²⁺/polyamine lignin for adsorption of W(VI) was synthesized by quaternization, amination and metallization from lignin with 3-chloro-2-hydroxypropyl trimethylammonium chloride, tetraethylenepentamine and ZnCl₂. The adsorbent was characterized by SEM-EDS, FTIR and XRD. The adsorption performance of Zn²⁺/polyamine lignin for W(VI) was investigated in batch system. The adsorption mechanism was revealed by zeta potential, SEM-EDS and FTIR and XPS. It was shown that Zn²⁺/polyamine lignin exhibited great adsorption capacity at pH of 2, 25 °C, oscillation rate of 400 r/min, initial tungsten concentration of 700 mg·L^-1 and adsorption time of 720 min. The maximum adsorption capacity of 0.5 g·L^-1 Zn²⁺/polyamine lignin for W(VI) reached 488.28 mg·g^-1. The adsorption followed Langmuir model and quasi-second-order kinetic model, indicating that the adsorption was monolayer homogeneous chemisorption. W(VI) was adsorbed through electrostatic attraction of hydrogen bond and Zn²⁺, ion exchange with Cl^- and coordination with -NH₂. The adsorption capacity reduced by only 6.47 % after seven cycles of adsorption-desorption, which indicated that Zn²⁺/polyamine lignin had a great application prospect.