N-doped lignin used for adsorption of tungsten was synthesized by polyamination and quaternization from lignin.The adsorbent was characterized by SEM-EDS and FTIR.The effects of pH,initial mass concentration of tungsten,adsorption time and amount of adsorbent on the adsorption capacity were investigated.The adsorption mechanism was revealed by SEM-EDS and FTIR and XPS.The results showed that N-doped lignin was loose and porous and contained a large amount of phenolic hydroxyl,amine and quaternary ammonium functional groups.When the total concentration of tungsten was 0.005 mol/L and the value of pH was smaller than 4.7,the existing form of tungsten was H2W12O406-.H2W12O406-was adsorbed by N-doped lignin through electrostatic attraction of hydrogen bond and coordination with amino and ion exchange with Cl-.The saturated adsorption capacity of 1 g/L N-doped lignin for tungsten reached 421.68 mg/g at pH of 4.0,with initial tungsten mass concentration of 800 mg/L and adsorption time of 960 min.The adsorption followed Langmuir model and quasi-second-order kinetic model,indicating that the adsorption was monolayer homogeneous chemisorption.
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