Institute of Environmental Engineering, Warsaw University of Life Science, 02-787 Warsaw, Poland.
Institute of Materials Engineering, University of Rzeszow, 35-310 Rzeszow, Poland.
Int J Mol Sci. 2023 Feb 23;24(5):4448. doi: 10.3390/ijms24054448.
A very low concentration of manganese (Mn) in water is a critical issue for municipal and industrial water supply systems. Mn removal technology is based on the use of manganese oxides (MnO), especially manganese dioxide (MnO) polymorphs, under different conditions of pH and ionic strength (water salinity). The statistical significance of the impact of polymorph type (akhtenskite ε-MnO, birnessite δ-MnO, cryptomelane α-MnO and pyrolusite β-MnO), pH (2-9) and ionic strength (1-50 mmol/L) of solution on the adsorption level of Mn was investigated. The analysis of variance and the non-parametric Kruskal-Wallis H test were applied. Before and after Mn adsorption, the tested polymorphs were characterized using X-ray diffraction, scanning electron microscope techniques and gas porosimetry analysis. Here we demonstrated the significant differences in adsorption level between MnO polymorphs' type and pH; however, the statistical analysis proves that the type of MnO has a four times stronger influence. There was no statistical significance for the ionic strength parameter. We showed that the high adsorption of Mn on the poorly crystalline polymorphs leads to the blockage of micropores in akhtenskite and, contrary, causes the development of the surface structure of birnessite. At the same time, no changes in the surfaces of cryptomelane and pyrolusite, the highly crystalline polymorphs, were found due to the very small loading by the adsorbate.
水中极低浓度的锰（Mn）是市政和工业供水系统的一个关键问题。Mn 去除技术基于在不同 pH 值和离子强度（水的盐度）条件下使用锰氧化物（MnO），特别是二氧化锰（MnO）多晶型物。研究了多晶型类型（水钠锰矿 ε-MnO、软锰矿 δ-MnO、黑锰矿 α-MnO 和硬锰矿 β-MnO）、pH 值（2-9）和离子强度（1-50 mmol/L）对 Mn 吸附水平的影响的统计显著性。应用方差分析和非参数 Kruskal-Wallis H 检验进行了分析。在 Mn 吸附前后，使用 X 射线衍射、扫描电子显微镜技术和气体孔隙率分析对测试的多晶型物进行了表征。在此，我们证明了 MnO 多晶型物类型和 pH 值之间在吸附水平上存在显著差异；然而，统计分析证明 MnO 的类型具有四倍的更强影响。离子强度参数没有统计学意义。我们表明，Mn 在非晶态多晶型物上的高吸附导致水钠锰矿中微孔的堵塞，相反，导致软锰矿表面结构的发展。同时，由于吸附物的负载非常小，高度结晶的多晶型物（黑锰矿和硬锰矿）的表面没有发现变化。
