Kinetics, thermodynamics, and structural investigations on the removal of Pb2+, Cd2+, and Zn2+ from multicomponent solutions onto natural and Fe(III)-modified zeolites
Kinetics, thermodynamics, and structural investigations on the removal of Pb2+, Cd2+, and Zn2+ from multicomponent solutions onto natural and Fe(III)-modified zeolites
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DOI：
10.1007/s10098-014-0794-8
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发表时间：
2015-02
影响因子：
4.3
通讯作者：
Marija Mihajlović;S. Lazarević;I. Janković-Častvan;J. Kovač;B. Jokić;Djordje Janackovic;R. Petrović-R.-Petrov
中科院分区：
文献类型：
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作者：
Marija Mihajlović;S. Lazarević;I. Janković-Častvan;J. Kovač;B. Jokić;Djordje Janackovic;R. Petrović-R.-Petrov
通过间歇实验研究了天然沸石和Fe(III)改性沸石对等摩尔多组分溶液中Pb2+、Cd2+和Zn2+的吸附，以确定不同初始浓度和不同温度下竞争效应对去除效率的影响。动力学和平衡研究表明，两种沸石对Pb2+的亲和力最高，对Zn2+和Cd2+的亲和力较低。在低浓度时，竞争效应可以忽略不计，而随着浓度的增加，对锌离子，尤其是对镉离子的吸附受到抑制。天然沸石对离子的亲和力低于改性沸石，从单组分溶液中的吸附情况来看，天然沸石的亲和力低于改性沸石。对于较低浓度和较高亲和力的离子，外膜扩散是速率控制步骤，而对于较高浓度和较低亲和力的离子，则以粒内扩散为主。吸附过程的自发性随温度的升高而增大，吸附热值为正值，表明吸附过程具有吸热性。用X射线光电子能谱(XPS)对负载Pb2+、Cd2+和Zn2+离子的吸附剂进行了结构研究，证实了Fe(III)改性沸石的表面和亚表面离子含量高于天然沸石。负载Fe(III)改性沸石的XPS深度分布表明，在铅和镉的情况下，表面吸附机制占主导地位，而锌在沸石样品上的负载主要是离子交换过程。
The adsorption of Pb2+, Cd2+, and Zn2+from equimolar multicomponent solutions onto natural and Fe(III)-modified zeolites was studied by batch experiments in order to determine the influence of the competitive effect on the efficiency ions removal at different initial concentrations and different temperatures. Kinetic and equilibrium studies showed that affinity of both zeolites was the highest for Pb2+and much lower for Zn2+and Cd2+. The competitive effect was negligible at lower concentrations, while Zn2+and especially Cd2+ions adsorption was suppressed as the concentrations were increased. Affinity of natural zeolite toward the ions was lower than that of the modified zeolite, as was shown for adsorption from single-component solutions. External film diffusion was the rate-controlling step at lower concentrations and for ions of higher affinity for the adsorbent, while intraparticle diffusion was dominant at higher concentrations and for ions of lower affinity for the adsorbent. The increasing spontaneity of the adsorption process with increasing temperature and the positive values of enthalpy of adsorption indicated the endothermic nature of the adsorption process. Structural investigations of the adsorbents loaded with Pb2+, Cd2+, and Zn2+ions by X-ray photoelectron spectroscopy (XPS) confirmed the higher content of the ions in the surface and subsurface regions of the Fe(III)-modified than of the natural zeolite. XPS depth profiles of the loaded Fe(III)-modified zeolite showed that surface mechanisms of adsorption were dominant in the case of lead and cadmium, while zinc loading on the zeolite sample was governed mainly by an ion-exchange process.