不同{021}/{110}晶面暴露比针铁矿对于As(V)吸附特性的研究
Adsorption properties of goethite with different {021}/{110} crystal surface exposure ratios for As(V)
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摘要: 为了探究针铁矿不同晶面吸附As(V)的作用,该研究制备两种具有不同比例{021}/{110}晶面的针铁矿,通过等温吸附和吸附动力学试验,研究不同初始As(V)浓度、pH和竞争阴离子影响下,两种针铁矿吸附As(V)的差异性。结果表明,As(V)在针铁矿表面的吸附更符合Freundlich和准二级动力学模型;经比表面积归一化,发现含有更高比例{021}/{110}晶面的Goe-B表面拥有更好的吸附性能,在pH=4时吸附量达到0.304 mg/m2,是Goe-A的1.57倍。pH会影响针铁矿的吸附,吸附量随着pH的增加而降低,而在碱性条件下Goe-B表现出更强的吸附能力。而随着As(V)浓度的增加,大量配体吸附引起的点位竞争效应会大于pH变化引起的静电力作用。吸附前后XRD的变化表明As(V)主要吸附在针铁矿表面,而不是结合到针铁矿的晶体结构中;而FTIR和XPS分析发现,As(V)通过与Fe-OH配体交换形成了新的络合物(Fe-O-As)吸附在针铁矿表面。研究显示,含有更高比例{021}/{110}晶面的针铁矿具有更好的吸附性能,是修复环境砷污染的理想吸附剂。Abstract: In order to explore the adsorption of As(V) by different goethite crystal faces, this study prepared two kinds of goethite with different proportions of {021}/{110} crystal faces. Through isothermal adsorption and adsorption kinetics experiments, the differences of the adsorption of As(V) by the two kinds of goethite under the influence of different initial As(V) concentrations, pH and competitive anions were studied. The results show that the adsorption of As(V) on the goethite surface is more consistent with Freundlich and pseudo-second-order kinetic model. According to the normalization of specific surface area, it is found that the surface of Goe-B containing a higher proportion of {021}/{110} crystal plane has better adsorption performance. At pH=4, the adsorption capacity reaches 0.304 mg/m2, which is 1.57 times of that of Goe-A. pH will affect the adsorption of goethite, and the adsorption amount decreases with the increase of pH, but the adsorption capacity of Goe-B is stronger under alkaline conditions. With the increase of As(V) concentration, the point competition effect caused by the adsorption of a large number of ligands is greater than the electrostatic force effect caused by the change of pH. The changes of XRD before and after adsorption indicate that As(V) is mainly adsorbed on the surface of goethite, rather than binding to the crystal structure of goethite. However, FTIR and XPS analysis showed that As(V) formed a new complex (Fe-O-As) by exchanging with Fe-OH ligand and adsorbed on the surface of goatee. Studies have shown that goethite with a higher proportion of {021}/{110} crystal planes has better adsorption performance and is an ideal adsorbent for environmental remediation of arsenic pollution.
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Key words:
- goethite /
- crystal plane /
- complex /
- adsorption /
- arsenic pollution
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