磁性生物炭对铅和镉离子的竞争吸附动力学

Competitive Adsorption Kinetics of Lead and Cadmium Ions on Magnetic Biochar

以玉米秸秆为原材料,通过水热合成法制备磁性生物炭,结合SEM、EDS、XRD、FTIR、BET技术对其进行表征,并研究温度、竞争作用对磁性生物炭吸附Pb^2+、Cd^2+的影响。利用准一级、准二级动力学模型和双室模型对所得数据进行拟合。结果表明,磁性生物炭含有丰富的含氧官能团及芳香结构,表面覆盖Fe 3O 4颗粒。磁性生物炭对Pb^2+、Cd^2+的吸附过程符合准二级动力学方程,表明化学吸附占主导地位。无论是单独吸附还是竞争吸附,Pb^2+在磁性生物炭上的吸附量高于Cd^2+,且升温有助于吸附反应的进行。双室模型也能较好地描述Pb^2+、Cd^2+在磁性生物炭上的吸附过程。Pb^2+、Cd^2+的吸附均以快室吸附为主,升温有助于提高快、慢室吸附速率。Pb^2+在快室吸附中的竞争能力高于Cd^2+,其竞争能力随温度升高而增大。Pb^2+于慢室吸附中的竞争能力在25℃时占优势,但随着温度升高,Cd^2+在慢室吸附中的竞争能力逐渐增强。

The magnetic biochar was prepared with corn stalk as raw material by one step hydrothermal synthesis method and characterized by SEM,EDS,FTIR,XRD and BET surface technologies.Then the effects of temperature and competitive adsorption of Pb^2+ and Cd^2+ on magnetic biochar were investigated.The adsorption experiment data were fitted by pseudo-first-order model and pseudo-second-order model as well as two-compartment model.The results showed that magnetic biochar contained a large amount of oxygen functional groups and aromatic structure.Meanwhile,Fe3O4 was successfully loaded on the surface of magnetic biochar.The results of kinetics experiments data proved that the adsorption process could be well described by the pseudo-second-order model and two-compartment model.The former suggests that the whole process was dominated by the chemical adsorption.The adsorption capacities follow the order Pb^2+>Cd^2+ in both single-component systems and competitive adsorption,and the adsorption capacities of Pb^2+ and Cd^2+ increased with the temperature increasing.The adsorption of Pb^2+ and Cd^2+ was dominated by fast-chamber adsorption,and as the temperature increases,the rate of adsorption in fast-chamber and slow-chamber increased.The competitive ability of Pb^2+ in fast-chamber adsorption was higher than that of Cd^2+,and its competitive ability increased with increasing temperature.The competitive ability of Pb^2+ in slow-chamber adsorption was dominant at 25℃,while with the temperature increasing,the competitive ability of Cd^2+ in slow-chamber adsorption gradually increased.