Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China.
Environ Sci Pollut Res Int. 2020 Nov;27(31):38397-38406. doi: 10.1007/s11356-020-07793-6. Epub 2020 Jan 29.
Proton adsorption behavior on the surface of Al-substituted goethites as a function of pH and ionic strength was investigated and simulated with the multisite surface complexation (MUSIC) model. In addition, X-ray diffraction, X-ray photoelectron spectroscopy, and field emission scanning electron microscope were used to characterize the crystal structure, chemical composition, micromorphology, and surface properties of the Al-substituted goethite. Al substitution was found to affect the crystal structure and micromorphology of goethite. The morphological differences did not result in significant differences in PZC value but largely affected the surface charge values. Goethite surface charge capacity increased progressively with increasing amount of Al substitution, which was attributed to increases in the density of surface coordinated sites due to the increase in (021)/(110) face ratio. The optimization calculations enabled a satisfactory fitting of the titration data of both pure goethite and Al-substituted goethite, and the MUSIC model facilitated a more specific understanding of the charging behavior of Al-substituted goethite. The singly (≡FeOH + ≡AlOH) and triply coordinated (≡FeO + ≡AlFeO) surface groups were most likely responsible for the basic charging behavior of goethite in the pH range of 4-10. All results indicate that the MUSIC model has excellent performance in characterizing Al-substituted goethite, and the model has promising application prospect in other substituted metal (hydr)oxides.
质子在 Al 取代针铁矿表面的吸附行为随 pH 值和离子强度的变化规律采用多配位表面络合（MUSIC）模型进行了研究和模拟。此外，采用 X 射线衍射、X 射线光电子能谱和场发射扫描电子显微镜对 Al 取代针铁矿的晶体结构、化学组成、微观形貌和表面性质进行了表征。研究发现，Al 取代会影响针铁矿的晶体结构和微观形貌。形态差异并未导致 PZC 值产生显著差异，但极大地影响了表面电荷值。针铁矿表面电荷容量随 Al 取代量的增加而逐渐增加，这归因于（021）/（110）面比率的增加导致表面配位位点数目的增加。优化计算实现了纯针铁矿和 Al 取代针铁矿滴定数据的良好拟合，并且 MUSIC 模型促进了对 Al 取代针铁矿荷电行为的更具体理解。在 pH 值为 4-10 的范围内，最可能负责针铁矿基本荷电行为的是单配位（≡FeOH + ≡AlOH）和三配位（≡FeO + ≡AlFeO）表面基团。所有结果均表明，MUSIC 模型在表征 Al 取代针铁矿方面具有出色的性能，并且该模型在其他取代金属（水合）氧化物中具有广阔的应用前景。
