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As(III) adsorption–oxidation behavior and mechanisms on Cr(VI)-incorporated schwertmannite
Environmental Science: Nano ( IF 7.3 ) Pub Date : 2021-4-13 , DOI: 10.1039/d1en00104c
Hong Ying 1, 2, 3, 4, 5 , Kun Huang 1, 2, 3, 4, 5 , Xionghan Feng 1, 2, 3, 4, 5 , Yupeng Yan 6, 7, 8, 9, 10 , Mengqiang Zhu 11, 12, 13, 14 , Zimeng Wang 10, 15, 16, 17 , Qiaoyun Huang 1, 2, 3, 4, 5 , Xiaoming Wang 1, 2, 3, 4, 5
Affiliation  

Schwertmannite, chromate (Cr(VI)), and arsenite (As(III)) usually coexist in acid mine drainage (AMD) and surrounding areas, but their interactions and mechanisms are poorly understood. We have determined the behavior and mechanisms of As(III) adsorption–oxidation on Cr(VI)-incorporated schwertmannite (Cr-Sch), with co-adsorption and redox of As(III) and Cr(VI) on pure schwertmannite as a comparison, using batch experiments combined with in situ quick X-ray absorption spectroscopy (Q-XAS). As(III) adsorption isotherms on Cr-Sch can be better described by the Freundlich equation, ascribed to the presence of multiple heterogeneity adsorption sites. With increasing Cr(VI) incorporation, both As(III) adsorption and oxidation increase remarkably. Additionally, with increasing pH from 3 to 7, As(III) adsorption increases, whereas its oxidation increases up to pH 5 and then decreases at higher pH due to the surface passivation by the generated Cr(III) precipitates. Cr(VI) speciation (aqueous vs. structural) seems to have no significant effects on As(III) adsorption–oxidation if structural Cr(VI) is available. The As(III) adsorption–oxidation pathways and mechanisms on Cr-Sch include, firstly, adsorption of As(III) through surface complexation and anionic exchange, followed by a direct redox between As(III) and Cr(VI) on the surface; the newly generated As(V) and Cr(III) then co-adsorb or precipitate on the mineral surface, simultaneously decreasing their toxicity and mobility. These new insights are essential to predict the mobility and availability of As and Cr in schwertmannite-rich natural environments.

中文翻译:

Cr(VI)结合的Schwertmannite的As(III)吸附-氧化行为及其机理

Schwertmannite,铬酸盐(Cr(VI))和亚砷酸盐(As(III))通常共存于酸性矿山排水(AMD)及其周围地区,但对它们的相互作用和机理了解甚少。我们已经确定了As(III)在结合了Cr(VI)的Schwertmannite(Cr-Sch)上的吸附行为和机理,以及As(III)和Cr(VI)在纯Schwertmannite上的共吸附和氧化还原。比较,使用批处理实验与原位快速X射线吸收光谱法(Q-XAS)相结合。砷(IIICr-Sch上的吸附等温线可以用Freundlich方程更好地描述,原因是存在多个异质性吸附位点。随着Cr(VI)掺入量的增加,As(III)的吸附和氧化均显着增加。另外,随着pH从3增加到7,As(III)的吸附增加,而其氧化增加至pH 5,然后由于产生的Cr(III)沉淀物的表面钝化而在较高的pH下降低。Cr(VI)的形态(水溶液结构)似乎对As(III)吸附-氧化没有显着影响,只要结构Cr(VI)可用。As(III)Cr-Sch的吸附-氧化途径和机理包括:首先通过表面络合和阴离子交换吸附As(III),然后在表面上As(III)和Cr(VI)之间直接进行氧化还原;然后,新生成的As(V)和Cr(III)共吸附或沉淀在矿物表面上,同时降低了它们的毒性和迁移率。这些新见解对于预测富含Schwertmannite的自然环境中As和Cr的迁移率和可用性至关重要。
更新日期:2021-04-27
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