The oxidation and sorption mechanism of Sb on delta-MnO2
The oxidation and sorption mechanism of Sb on delta-MnO2
复制标题
Sb在δ-MnO2上的氧化和吸附机理
DOI：
10.1016/j.cej.2018.02.091
复制
发表时间：
2018
影响因子：
15.1
通讯作者：
Wang Yu-Jun
中科院分区：
文献类型：
--
作者：
Sun Qian;Liu Cun;Alves Marcelo Eduardo;Ata-Ul-Karim Syed Tahir;Zhou Dong-Mei;He Jian-Zhou;Cui Pei-Xin;Wang Yu-Jun
锰氧化物由于其丰富的含量和活性被认为是土壤中许多污染物命运的潜在调节剂。采用静态平衡实验、动力学实验和多种光谱技术研究了锑在δ-MnO 2上的氧化和吸附机理。实验结果表明，δ-MnO 2表面Mn（IV）位具有较高的Sb（III）氧化能力，氧化反应是质子驱动的。然而，氧化过程逐渐抑制锑酸锰沉淀物的积累，反应性较低的Mn（III）的生产，以及产品Mn（II）和Sb（V）在表面上的位置阻塞效应。X射线粉末衍射（XRD）和透射电镜（TEM）结果表明，与Sb（V）直接吸附不同，Sb（III）的氧化破坏了δ-MnO 2的表面结构，暴露出更多的活性中心。Sb（V）的吸附沿着Sb（III）的氧化，因此，可以归因于几种结合模式，即，Mn（II）阳离子桥，与Mn（II）沉淀，沿着与表面Mn（IV）和Mn（III）位点的内球络合。通过X射线光电子能谱（XPS）、X射线吸收精细结构谱（EXAFS）和衰减全反射傅里叶变换红外光谱（ATR-FTIR）分析，Sb（V）吸附在δ-MnO 2的边缘位置，形成Mn-O（H）-Sb（V）单齿单核配合物。研究结果有助于更好地理解地下环境中Sb与δ-MnO 2的地球化学动力学。
Manganese (Mn) oxide is considered as a potential regulator of the fate of many contaminants in soil due to its abundance and reactivity. The present study investigated the oxidation and sorption mechanisms of antimony (Sb) on δ-MnO2, by combining batch equilibrium experiments, kinetic experiments and various spectroscopic techniques. The collective results confirmed the high Sb(III)-oxidizing capacity of Mn(IV) sites on δ-MnO2and the oxidation reaction was proton-driven. However, the oxidation process was gradually inhibited by the accumulation of manganese antimonate precipitates, the production of less reactive Mn(III), and the site-blocking effects of products Mn(II) and Sb(V) on the surface. Different from the direct sorption of Sb(V) by δ-MnO2, the oxidation of Sb(III) destroyed the surface structure of δ-MnO2and exposed more reactive sites as evidenced by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The stronger Sb(V) sorption along with the oxidation of Sb(III), therefore, could be attributed to several binding modes, i.e., Mn(II) cation bridge, precipitation with Mn(II), along with inner-sphere complexations with surface Mn(IV) and Mn(III) sites. Sb(V) was sorbed at the edge sites of δ-MnO2forming monodentate mononuclear complex with a configuration of Mn-O(H)-Sb(V) as confirmed by supplementary X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (EXAFS) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy techniques. The findings altogether help to contribute to a better understanding on the geochemical dynamics of Sb with δ-MnO2in subsurface environment.