铅和铜离子在纳米羟基磷灰石上的竞争吸附动力学研究

Competitive Adsorption Kinetics of Aqueous Pb^(2+) and Cu^(2+) on Nano-HAP Surfaces

通过吸附动力学试验研究了Pb2+和Cu2+在纳米羟基磷灰石(Nano-HAP)上的竞争吸附动力学过程,比较了吸附前后Nano-HAP的Zeta电位以及X射线衍射图谱等,对Pb2+和Cu2+在Nano-HAP上的竞争吸附机制进行了探讨.结果表明,单一铅、铜离子存在时,Pb2+较Cu2+在Nano-HAP上的吸附量要高;当铅、铜这2种离子共存时,Pb2+和Cu2+在Nano-HAP表面发生竞争吸附,铜的吸附量增加,而铅的吸附量下降.结合X射线衍射图谱和动力学反应中Ca2+的溶出量,推测出Cu2+在Nano-HAP上的吸附以静电吸附和表面络合为主,而Pb2+在Nano-HAP上的吸附以溶解-沉淀反应为主,Pb2+、Cu2+在Nano-HAP上的吸附量与Ca2+的溶出量线性关系显著(R2为0.861～0.954).分别用一级、二级动力学方程、抛物线方程、Elovich方程、双常数方程和LJ方程对Pb2+和Cu2+在Nano-HAP上的吸附动力学过程进行了拟合,其中二级动力学方程和双常数方程拟合结果较好,说明Pb2+和Cu2+在Nano-HAP表面的动力学吸附反应是一个化学反应和物理吸附均占一定比例的复杂的吸附过程.

Competitive adsorption kinetics of aqueous Pb2＋ and Cu2＋on Nano-HAP surfaces were investigated by performing the adsorption kinetic experiments and comparing the change of ζ potentials and XRD-map before and after metal adsorption.The results showed that the adsorption quantity of Pb2＋ on Nano-HAP was higher than that of Cu2＋ in the single system.However,the competitive adsorption of Pb2＋ and Cu2＋ occurred in the co-existence system of Pb2＋ and Cu2＋.The adsorption quantity of Cu2＋ on Nano-HAP increased,while that of Pb2＋ decreased.The X-ray diffraction（XRD） and adsorption quantities of Ca2＋ surface analysis indicated that dissolution-precipitation is the primary immobilization mechanism for Pb2＋,while surface complexation and electrostatic adsorption account for Cu2＋ sequestration.The adsorption quantities of Pb2＋ and Cu2＋on Nano-HAP had marked linear relationship with Ca2＋ release from Nano-HAP（R2 0.861-0.954）.The adsorption kinetics were fitted with the equations of first-order,second-order,parabola,Elovich,double constant equation and LJ function,respectively,in which the second-order and power function kinetics equation fitted the results best.According to above results,the adsorption kinetics of Pb2＋ and Cu2＋ on Nano-HAP is a complex adsorption processes with both chemical reaction and physical adsorption.