城郊小河流沉积物吸附Pb2+的动力学过程

采用分批试验法，对城郊小河流沉积物吸附Pb2+过程进行了研究，探讨了Pb2+吸附的动力学过程和机制.结果表明，随着溶液中沉积物质量增大，达到吸附平衡所需时间变短，单位沉积物吸附量和达到吸附平衡后溶液中Pb²⁺浓度变低；沉积物含量>0.6 g·L^-1时对溶液中Pb²⁺的去除率超过95%；Pb²⁺在沉积物上吸附的动力学过程符合假二级动力学模型，该模型拟合的平衡吸附量也更接近真实值；Pb²⁺初始吸附速率与初始溶液中沉积物质量无明显的相关性；随溶液中沉积物浓度的增加，吸附速率常数逐渐增大，化学吸附所起的作用也越显著；较高浓度沉积物吸附Pb²⁺的动力学机制能较好符合Elovich方程，但较低浓度沉积物时则相对较差；从吸附速率来看，溶液中沉积物质量较高时，内扩散是整个吸附过程速率的控制步骤，沉积物含量较低时，吸附速率存在多级线性过程，初始阶段非均相扩散是主要控制步骤，但随着时间的延长，其吸附过程转变为沉积物内部的扩散过程.

Kinetics of Adsorption of Pb2+ onto Small River Sediment

The batch experiments of adsorption of Pb2+ onto small river sediments were conducted. The kinetics of the sorption process was analyzed. The results showed that the equilibrium time of adsorption increased with the increasing of sediment mass in solution, while both adsorbed Pb²⁺ on per unit of sediment and Pb²⁺ concentration in the solution after equilibrium decreased. More than 95% of Pb²⁺ in solution was removed when sediment contents larger than 0.6 g·L^-1. Both pseudo first order and pseudo second order kinetics were tested and it was found that the latter gave a better explanation of the adsorption process. The equilibrium adsorption capacities calculated from the pseudo second order model could represent the true value. There was no significant correlation between initial adsorption rate of Pb²⁺ and the amount of sediment in solution. However, the pseudo second order rate constant increased in the solution with more adsorbent, namely chemical adsorption controlled the process. Elovich equation could explain the mechanism of sorption in the solution with higher contents of sediment; nevertheless, the process of low concentration of adsorbent adsorbing Pb²⁺ disagreed well with Elovich equation. In terms of adsorption rate in the sorption, intra particle diffusion dominated in the more sediment solution. On the other hand, multi linearity was presented for the adsorption rate in less adsorbent solution. The first, sharper portion represented adsorption on the external surface. The second portion indicated Pb²⁺ diffused gradually into the interior of particles and intra particle diffusion controlled.