Fate of arsenic during up to 4.5 years of aging of Fe-III-As-V coprecipitates at acidic pH: E ffect of reaction media (Nitrate vs. Sulfate), Fe/As molar ratio, and pH
Fate of arsenic during up to 4.5 years of aging of Fe-III-As-V coprecipitates at acidic pH: E ffect of reaction media (Nitrate vs. Sulfate), Fe/As molar ratio, and pH
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FeIII-AsV 在酸性 pH 下共沉淀长达 4.5 年的老化过程中砷的命运：反应介质（硝酸盐与硫酸盐）、Fe/As 摩尔比和 pH 的影响
DOI：
10.1016/j.cej.2020.124239
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发表时间：
2020
影响因子：
15.1
通讯作者：
Jia Yongfeng
中科院分区：
文献类型：
--
作者：
Zhang Danni;Cao Rui;Wang Shaofeng;Wang Ying;Bi Ran;Jia Yongfeng
在酸性矿山废水和湿法冶金实践中产生的砷酸铁(FeIII-ASV)共沉淀物是环境中砷污染的潜在来源之一。然而，在酸性条件下，FeIII-AsV共沉淀物的As行为以及转化过程仍未完全清楚。本工作系统地研究了反应介质(硫酸盐和硝酸盐)、Fe/As摩尔比和酸性pH值对FeIII-AsV共沉淀物在不同温度下的转化速度、路线和产物的影响，在长达4.5年的老化过程中。X射线衍射、透射电子能谱、拉曼光谱和扩展X射线吸收精细结构能谱分析表明，在pH为4的硫酸盐和硝酸盐介质中，以低结晶的砷酸铁为前驱体，Fe/As摩尔比为2的FeIII-AsV共沉淀物转变为蝎子石。相比之下，Fe/As=1：4的样品在硫酸盐和硝酸盐介质中分别形成了类珊瑚石和赤铁矿。Fe/As=2和4的样品在陈化过程中砷被释放到液相中。Fe/As=2和4的样品在硫酸盐介质中的水砷浓度([As]AQ)都大于在硝酸盐介质中的[As]AQ。此外，在Fe/As摩尔比为8和16、pH为2.5的条件下，随着[As]AQ的降低，转化产物为针铁矿和黄钾铁矾土。结果还表明，六线水合铁是许多Fe-As转化过程中常见的中间体。
Iron-arsenate (FeIII-AsV) coprecipitate generated in acid mine drainage and hydrometallurgical practices is one of the potential sources of As contamination in the environment. However, the As behavior as well as the transformation process of the FeIII-AsVcoprecipitate is still not fully understood under acidic conditions. This work systematically studied the effect of reaction media (sulfate vs. nitrate), Fe/As molar ratios, and acidic pH values on the transformation rates, routes, and products of the FeIII-AsVcoprecipitates at different temperatures during up to 4.5 years of aging. X-ray diffraction (XRD), transmission electron spectroscopy (TEM), Raman spectroscopy, and extended X-ray absorption fine structure spectroscopy (EXAFS) results showed that the FeIII-AsVcoprecipitates with Fe/As = 2 transformed to scorodite at pH 4 in both sulfate and nitrate media with poorly crystalline ferric arsenate as precursor. In comparison, for the Fe/As = 4 samples, parascorodite and hematite were formed in sulfate and nitrate media, respectively. Arsenic was released into the liquid phase during the aging process for the samples with Fe/As = 2 and 4. The aqueous As concentrations ([As]aq) in sulfate media were larger than those in nitrate media for both the Fe/As = 2 and 4 samples. In addition, the transformation products were goethite and Na-jarosite at Fe/As = 8 and 16, pH 2.5 with the decrease of [As]aq. The results also indicated that 6-line ferrihydrite was a common intermediate for many Fe-As transformation processes.