Zhang Ruifeng, Yang Shilian, Dong Chuan, Qiao Yu, Zhang Jianmin, Guo Yingming
School of Urban Planning and Municipal Engineering, Xi'an Polytechnic University Xi'an 710048 PR China
RSC Adv. 2021 Oct 15;11(53):33798-33808. doi: 10.1039/d1ra06025b. eCollection 2021 Oct 8.
Ammonium and manganese removal by tunnel-structured manganese oxide is still enigmatic. Herein, tunnel-structured akhtenskites with different structural cations (Na-MnO , Mg-MnO Ca-MnO , Fe-MnO ) were synthesized by the KMnO and Mn reaction in the presence of different metal cations, and were used to remove ammonium and manganese from aqueous solution. The results of the batch adsorption experiments indicated that akhtenskites effectively removed NH and Mn, and the removal process fitted the pseudo-second-order model. By measuring the concentration of nitrate and nitrite, discriminating the adsorbed and oxidized Mn, and testing the zeta potential of the oxides, it can be concluded that NH was merely removed by electrostatic adsorption [triple bond, length as m-dash]Mn-O; Mn could also be adsorbed by ion exchange with [triple bond, length as m-dash]Mn-OH, and the adsorbed Mn could be partly oxidized. The structural properties of the akhtenskites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific area, and X-ray photoelectron spectroscopy (XPS). The experimental results showed that ions with higher valence can result in a higher percentage of Mn(iii) in akhtenskite. Mg can result in a lower proportion of lattice oxygen in the oxide, and Fe can increase the pH of the point of zero charge. Both of them were unfavored for the oxidation of Mn. Moreover, it was found that Ca-MnO had optimal removal performance in the catalytic oxidation of Mn owing to appropriate percentages of O and Mn(iii) and lower zeta potential. This study provides new insights into the synthesis and application of manganese oxides.
隧道结构氧化锰去除铵和锰的机制仍不明确。在此，通过在不同金属阳离子存在下使高锰酸钾与锰反应，合成了具有不同结构阳离子（Na-MnO 、Mg-MnO 、Ca-MnO 、Fe-MnO ）的隧道结构阿克滕石，并用于从水溶液中去除铵和锰。批量吸附实验结果表明，阿克滕石能有效去除NH 和Mn，且去除过程符合准二级模型。通过测量硝酸盐和亚硝酸盐的浓度、区分吸附态和氧化态的Mn以及测试氧化物的zeta电位，可以得出结论：NH 仅通过静电吸附被去除[三键，长度为m破折号]Mn-O；Mn也可通过与[三键，长度为m破折号]Mn-OH进行离子交换而被吸附，且吸附的Mn可部分被氧化。通过X射线衍射（XRD）、扫描电子显微镜（SEM）、布鲁诺尔-埃米特-泰勒（BET）比表面积和X射线光电子能谱（XPS）对阿克滕石的结构性质进行了表征。实验结果表明，高价离子可导致阿克滕石中Mn(iii)的比例更高。Mg可导致氧化物中晶格氧的比例更低，而Fe可提高零电荷点的pH值。二者均不利于Mn的氧化。此外，发现Ca-MnO 由于O和Mn(iii)的比例合适且zeta电位较低，在Mn的催化氧化中具有最佳去除性能。本研究为氧化锰的合成与应用提供了新的见解。
