改性玉米秸秆对水中磷酸根的吸附动力学研究

Adsorption Kinetics of Phosphate from Aqueous Solutions onto Modified Corn Residue

将化学改性后的玉米秸秆制备阴离子交换剂,重点研究了改性玉米秸秆对磷酸根的吸附动力学特性.通过静态实验,考察了在不同pH、温度、磷酸根初始浓度条件下,改性玉米秸秆对磷酸根吸附效果的影响,并分别用伪一级动力学方程、伪二级动力学方程、修正伪一级动力学方程和颗粒内扩散方程进行拟合,计算出相应的速率常数.结果表明,Langmuir等温模式能更好地描述改性玉米秸秆对磷酸根的吸附效果,并且随着温度的升高,改性玉米秸秆对磷酸根的最大吸附量逐渐减小.改性玉米秸秆对磷酸根的吸附是一个快速吸附过程,30 min内即可达到吸附平衡,该吸附过程符合伪二级动力学方程和颗粒内扩散方程,吸附速率主要受颗粒内扩散控制.随着初始浓度的增大,伪二级吸附速率常数逐渐减小,颗粒内扩散速率常数逐渐增大.通过改性玉米秸秆对磷酸根的吸附动力学研究,可以为反应器的设计和污水处理装置的运行提供基础信息,对于去除水溶液中磷酸根的技术应用具有重要实际意义.

The adsorption kinetics of phosphate from aqueous solutions onto modified corn residue was studied in a batch reactor. The influence of initial pH, concentration and temperature to adsorption effect were investigated. In addition, the kinetic data were fitted by pseudo-first-order equation, pseudo-second-order equation, modified pseudo-first-order equation and intra-particle diffusion model, and the respective characteristic rate constants were presented. The results showed that the adsorption data fitted Freundlich isotherm model, and the maximum adsorption capacity of phosphate would decrease with the temperature increasing. Furthermore, the adsorption process could reached equilibrium in 30 minutes, and the pseudo-second-order equation and intra-particle diffusion model generated the best agreement with the experimental data for the adsorption systems. The intra-particle diffusion was the main rate-controlling step. With increasing initial concentration, the rate constant of pseudo-second-order equation decreases and that of intra-particle diffusion model increases. The adsorption kinetic analyses could be of a great practical value for the technological applications of phosphate removal from aqueous solutions.