| Mg-Al-Me (Me=La,Ce,Zr)复合氧化物制备及其除氟性能 |
| 摘要点击 2676 全文点击 1166 投稿时间：2016-05-23 修订日期：2016-07-18 |
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| 中文关键词 稀有金属 含氟废水 吸附等温线 吸附动力学 动边界模型 |
| 英文关键词 rare metal wastewater containing fluoride adsorption isotherm adsorption kinetic moving boundary model |
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| 中文摘要 |
| 采用双滴共沉淀-煅烧法制备Mg-Al-Me（Me=La，Ce，Zr）金属复合氧化物吸附剂，通过扫描电子显微镜（SEM）和X射线衍射（XRD）对制备的吸附剂进行表征. 采用批实验考察了吸附时间，初始氟浓度和共存离子（Cl-、NO3-、SO42-、CO32-、HCO3-、PO43-）对氟吸附性能的影响. 结果表明，3种吸附剂对氟吸附过程可用准二级动力学模型描述. 3种吸附剂对氟吸附速率主要受液膜扩散速率、颗粒内扩散速率和吸附反应速率共同控制. 等温吸附结果显示Mg-Al-La对氟吸附能力最大，Mg-Al-Ce次之，Mg-Al-Zr最小，3种材料对氟吸附规律均符合Langmuir等温吸附方程，其最大饱和吸附量分别为54.22、51.65、50.89 mg·g-1. 共存离子对3种材料吸氟存在不同程度的竞争，其影响次序是Cl- < NO3- < SO42- < CO32-≈HCO3-43-. |
| 英文摘要 |
| The Mg-Al-Me(Me=La, Ce, Zr) composites were prepared by co-precipitation method of Mg, Al, Me(Me=La, Ce, Zr) salt solutions with a molar ratio of 20:1:4. The sample were calcined at 500℃ for 5h as the adsorbents for removal of fluoride. The adsorbents were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The patterns of SEM indicated that three calcined sorbents were somewhat agglomerated particles to form a sheet structure after adsorption. The patterns of XRD showed that the three adsorbents fored a metal composite oxide. The effects of adsorption time, initial concentration of fluorine and coexisting ions (Cl-, NO3-, SO42-, CO32-, HCO3-, PO43-) fluorine adsorption properties on three adsorbents were tested by batch adsorption experiments. The results showed that the kinetics of fluorine on three adsorbents were well fitted by pseudo-second-order model. And the adsorption rate of fluoride on three adsorbents decreased in the order of Mg-Al-Zr > Mg-Al-La > Mg-Al-Ce. Regression results of adsorption rate controlling step test by moving boundary model indicated that intra-particle diffusion rate was not the only rate-limiting step in the adsorption of fluoride on the three materials. The equilibrium isotherm showed that the adsorption capacity of fluoride uptake by three adsorbents decreased in the order of Mg-Al-La > Mg-Al-Ce > Mg-Al-Zr. The adsorption isotherm of three adsorbents was very well described by the Langmuir models, and their linear correlations were 0.9958, 0.9790, 0.9975, respectively. The maximum adsorption capacities of fluoride on Mg-Al-La, Mg-Al-Ce, Mg-Al-Zr calculated by Langmuir model were as high as 54.22, 51.65, 50.89 mg·g-1, respectively. The results showed that the co-existing anions such as CO32-, HCO3-, PO43- had an inhibitory effect on the Mg-Al-La, Mg-Al-Ce, Mg-Al-Zr adsorption of fluoride. The effect of coexisting anions on fluoride adsorption increased in the order of Cl- < NO3- < SO42- < CO32-≈HCO3-43-. |
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