Wang Yan, Tan Wen-Feng, Feng Xiong-Han, Qiu Guo-Hong, Liu Fan
College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
Huan Jing Ke Xue. 2011 Oct;32(10):3128-36.
Adsorption characteristics of mineral surface for heavy metal ions are largely determined by the type and amount of surface adsorption sites. However, the effects of substructure variance in manganese oxide on the adsorption sites and adsorption characteristics remain unclear. Adsorption experiments and powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) were combined to examine the adsorption characteristics of Pb2+, Cu2+, Zn2+ and Cd2+ sequestration by birnessites with different Mn average oxidation state (AOS), and the Mn AOS dependent adsorption sites and adsorption characteristics. The results show that the maximum adsorption capacity of Pb2+, Cu2+, Zn2+ and Cd2+ increased with increasing birnessite Mn AOS. The adsorption capacity followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The observations suggest that there exist two sites on the surface of birnessite, i. e., high-binding-energy site (HBE site) and low-binding-energy site (LBE site). With the increase of Mn AOS for birnessites, the amount of HBE sites for heavy metal ions adsorption remarkably increased. On the other hand, variation in the amount of LBE sites was insignificant. The amount of LBE sites is much more than those of HBE sites on the surface of birnessite with low Mn AOS. Nevertheless, both amounts on the surface of birnessite with high Mn AOS are very close to each other. Therefore, the heavy metal ions adsorption capacity on birnessite is largely determined by the amount of HBE sites. On birnessite surface, adsorption of Cu2+, Zn2+, and Cd2+ mostly occurred at HBE sites. In comparison with Zn2+ and Cd2+, more Cu2+ adsorbed on the LBW sites. Pb2+ adsorption maybe occupy at both LBE sites and HBE sites simultaneously.
矿物表面对重金属离子的吸附特性在很大程度上取决于表面吸附位点的类型和数量。然而，氧化锰亚结构变化对吸附位点及吸附特性的影响仍不清楚。结合吸附实验、粉末X射线衍射（XRD）和X射线光电子能谱（XPS），研究了不同平均氧化态（AOS）的水钠锰矿对Pb2+、Cu2+、Zn2+和Cd2+的吸附特性，以及锰AOS依赖的吸附位点和吸附特性。结果表明，Pb2+、Cu2+、Zn2+和Cd2+的最大吸附量随水钠锰矿锰AOS的增加而增大。吸附量顺序为Pb2+＞Cu2+＞Zn2+＞Cd2+。研究结果表明，水钠锰矿表面存在两个位点，即高结合能位点（HBE位点）和低结合能位点（LBE位点）。随着水钠锰矿锰AOS的增加，用于重金属离子吸附的HBE位点数量显著增加。另一方面，LBE位点数量的变化不显著。在低锰AOS的水钠锰矿表面，LBE位点的数量远多于HBE位点。然而，在高锰AOS的水钠锰矿表面，两者的数量非常接近。因此，水钠锰矿对重金属离子的吸附能力在很大程度上取决于HBE位点的数量。在水钠锰矿表面，Cu2+、Zn2+和Cd2+的吸附主要发生在HBE位点。与Zn2+和Cd2+相比，更多的Cu2+吸附在LBE位点。Pb2+的吸附可能同时占据LBE位点和HBE位点。
