Pan Bingcai, Zhang Qingrui, Du Wei, Zhang Weiming, Pan Bingjun, Zhang Qingjian, Xu Zhengwen, Zhang Quanxing
State Key Laboratory of Pollution Control and Resources Reuse, Department of Environmental Engineering, Nanjing University, Nanjing 210093, People's Republic of China.
Water Res. 2007 Jul;41(14):3103-11. doi: 10.1016/j.watres.2007.03.004. Epub 2007 Apr 12.
Selective removal of heavy metals from water has been of considerable concern for several decades. In the present study, the amorphous zirconium phosphate (ZrP) was synthesized and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron micrography (SEM), thermogravimetric analysis (TGA) as well as pH-titration experiments. Uptake of heavy metals including lead, cadmium, and zinc onto ZrP was studied by using a polystyrene sulfonic-acid exchanger D-001 as a reference sorbent and Ca(2+) as a competing cation due to its ubiquity in natural or industrial waters. The results indicated that the uptake of heavy metals onto ZrP is essentially an ion-exchange process and dependent upon solution pH. In comparison with D-001, ZrP exhibited more favorable sorption of heavy metals particularly in terms of high selectivity, as indicated by the distribution coefficients of ZrP even several orders higher than D-001 towards heavy metals when calcium ion coexisted at a high level in solution. The Fourier transform-infrared (FT-IR) spectroscopic investigation indicated that the uptake of calcium, cadmium, and zinc ions onto ZrP is only driven by the electrostatic interaction, while that of lead ion is possibly dependent upon the inner-sphere complex formation with ZrP. XPS results further elucidated that ZrP displays different sorption affinity towards heavy metals in the same order as selectivity sequence of Pb(2+)>Zn(2+) approximately Cd(2+)>Ca(2+), which can be explained by hard and soft acids and bases (HASB) theory. Moreover, uptake of heavy metals onto ZrP approached to equilibrium quickly and the used ZrP could be readily regenerated for reuse by the dilute HCl solution. Thus, all the results suggest that amorphous ZrP has excellent potential as a sorption material for water treatment.
几十年来，从水中选择性去除重金属一直备受关注。在本研究中，合成了非晶态磷酸锆（ZrP），并通过X射线光电子能谱（XPS）、X射线衍射（XRD）、扫描电子显微镜（SEM）、热重分析（TGA）以及pH滴定实验对其进行了表征。以聚苯乙烯磺酸交换剂D-001作为参考吸附剂，以Ca(2+)作为竞争阳离子，研究了ZrP对包括铅、镉和锌在内的重金属的吸附，因为Ca(2+)在天然水或工业水中普遍存在。结果表明，重金属在ZrP上的吸附本质上是一个离子交换过程，并且取决于溶液的pH值。与D-001相比，ZrP对重金属表现出更有利的吸附，特别是在高选择性方面，当溶液中钙离子含量较高时，ZrP对重金属的分配系数比D-001高几个数量级就表明了这一点。傅里叶变换红外（FT-IR）光谱研究表明，钙离子、镉离子和锌离子在ZrP上的吸附仅由静电相互作用驱动，而铅离子的吸附可能取决于与ZrP形成的内球络合物。XPS结果进一步阐明，ZrP对重金属的吸附亲和力按Pb(2+)>Zn(2+)≈Cd(2+)>Ca(2+)的选择性顺序排列，这可以用软硬酸碱（HASB）理论来解释。此外，重金属在ZrP上的吸附很快达到平衡，用过的ZrP可以很容易地用稀盐酸溶液再生以供再利用。因此，所有结果表明非晶态ZrP作为一种水处理吸附材料具有优异的潜力。
