N掺杂木质素对钨的吸附

Adsorption of tungsten by N-doped lignin

木质素经胺化和季铵化改性后制备了N掺杂木质素,并用于吸附钨,通过SEM-EDS和FTIR对吸附剂进行表征,考察pH值、钨初始质量浓度、吸附时间和吸附剂用量对吸附容量的影响,利用SEMEDS、FTIR和XPS分析揭示吸附过程的机制.结果表明,N掺杂木质素表面疏松多孔且含有大量的酚羟基、胺基和季铵官能团,在总钨浓度为0.005 mol/L、pH<4.7时,钨的存在形态为H_(2)W_(12)O_40)^(6-).H_(2)W_(12)O_(40)^(6-)通过与N掺杂木质素中氢键的静电吸引、胺基的配合和氯离子的离子交换作用而被吸附.在pH=4.0、钨初始质量浓度为800 mg/L、吸附时间为960 min的条件下,1 g/L N掺杂木质素对钨的饱和吸附容量为421.68 mg/g.吸附过程遵循Langmuir模型和准二级动力学模型,表明吸附过程为单分子层均质化学吸附.

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 H_(2)W_(12)O_40)^(6-).H_(2)W_(12)O_(40)^(6-)-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.