粉煤灰合成NaA型沸石对重金属离子的吸附动力学

以粉煤灰为原料,采用两步法合成了单一沸石矿物种的NaA型沸石,对合成产物的结构和性能进行了表征.通过静态吸附实验,研究了NaA型沸石对水溶液中Cu(ΙΙ)、Cr(Ⅵ)和Zn(ΙΙ)离子的吸附特性,从动力学角度探讨了吸附机理.结果表明,在所研究的浓度和pH值条件下,NaA型沸石对3种重金属的吸附符合Langmuir等温吸附方程,静态饱和吸附量(Qm)分别为82.30,65.96,47.78mg/g;3种金属离子在水溶液中的存在方式和大小是影响它们吸附行为的主要因素,通过动边界模型推算表明:NaA型沸石对Cu(ΙΙ)和Zn(ΙΙ)离子的吸附过程的速度控制步骤为液膜扩散,对Cr(Ⅵ)离子的吸附过程的速度控制步骤为颗粒扩散,3种金属离子的吸附过程符合伪二级方程.

Adsorption kinetics of heavy metal ions on NaA zeolite synthesized from fly ash

Single-phase zeolite NaA was synthesized from fly ash using two-stage method. The structure and performance of the products were characterized. With the static method, the adsorption properties of NaA zeolite to Cu(ΙΙ), Cr(Ⅵ) and Zn(ΙΙ) in aqueous solution was studied and adsorption mechanism was discussed from kinetic point of view. Under the experinental concentration and pH value, the equilibrium adsorption data fitted to Langmuir isotherms and the greatest adsorption capacity of Cu(ΙΙ), Cr(Ⅵ) and Zn(ΙΙ) was 82.30, 65.96 and 47.78 mg/g, respectively. The existing way and size of three heavy metal ions in aqueous solution were important influential factors on adsorption behavior. Moving Boundary Model analysis showed that the adsorption rate of Cu(ΙΙ) and Zn(ΙΙ) was mainly governed by liquid film diffusion, and intra-particle diffusion was important controlling factor for the adsorption rate of Cr(Ⅵ). The adsorption processes of three heavy metal ions followed a pseudo-second-order kinetic model.