Abstract Thioarsenic is one of the major arsenic species recently detected in high-arsenic groundwater, and precise detection of thioarsenic is very important for understanding arsenic transport in the environment. However, the existing methods usually involve complicated operation procedures at a high cost. In this work, a cost-effective new method was developed for direct measurement of monothioarsenate (MTA) using Liquid Chromatography Hydride-Generation Atomic Fluorescence (LC-HGAFS), and it was applied to study MTA adsorption on the sand, soil, and goethite. The standard MTA sample was prepared using As2O3, NaOH, and sulfur, and its purity was determined at different reaction temperatures to identify the thermal effect. Results showed that the major component of the prepared MTA sample was Na3AsSO3•7H2O and its purity was higher than 98% with only one impurity of arsenite. With the decrease of reaction temperature, the purity of the MTA sample decreased and both arsenite and arsenate impurities were present in samples. When MTA concentrations were at the range of 18–360 μg/L, it had an excellent linear relationship with the peak area with a coefficient determination (R2) greater than 0.9998 and an analytical detection limit of 33 μg/L. For three water samples containing different concentrations of arsenite, arsenate, and MTA, the relative errors between the detected and actual values were ranged from −0.11% to 8.21%. The adsorption of MTA on the sand, soil, and goethite reached equilibrium at 4 h, 8 h, and 8 h, respectively, and their maximum adsorption capacities were 122.47, 226.73 and 1979.75 μg/g, respectively. MTA adsorptions on sand and soil fitted well with Langmuir as well as Freundlich models, with R2 values greater than 0.98 and 0.96, respectively. MTA adsorption on goethite fitted better into the Freundlich model with an R2 value of 0.9863. Besides, the increasing pH values can suppress MTA adsorption on these three media because iron oxide is the major factor controlling the MTA adsorption on them.

中文翻译：

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LC-HGAFS直接测定硫代砷酸盐方法的开发及其吸附特性的应用

摘要 硫砷是近年来在高砷地下水中检测到的主要砷种类之一，准确检测硫砷对于了解环境中砷的迁移具有重要意义。然而，现有的方法通常操作步骤复杂，成本高。在这项工作中，开发了一种使用液相色谱氢化物发生原子荧光 (LC-HGAFS) 直接测量一硫代砷酸盐 (MTA) 的经济高效的新方法，并将其应用于研究 MTA 在沙子、土壤和针铁矿上的吸附. 使用 As2O3、NaOH 和硫制备标准 MTA 样品，并在不同反应温度下测定其纯度以鉴定热效应。结果表明，制备的MTA样品的主要成分为Na3AsSO3•7H2O，纯度大于98%，只有一种亚砷酸盐杂质。随着反应温度的降低，MTA样品的纯度降低，样品中同时存在亚砷酸盐和砷酸盐杂质。当 MTA 浓度在 18-360 μg/L 范围内时，它与峰面积呈极好的线性关系，测定系数 (R2) 大于 0.9998，分析检出限为 33 μg/L。对于含有不同浓度亚砷酸盐、砷酸盐和 MTA 的三个水样，检测值与实际值之间的相对误差范围为 -0.11% 至 8.21%。MTA在沙子、土壤和针铁矿上的吸附分别在4 h、8 h和8 h达到平衡，它们的最大吸附容量分别为 122.47、226.73 和 1979.75 μg/g。MTA 在沙子和土壤上的吸附与 Langmuir 和 Freundlich 模型非常吻合，R2 值分别大于 0.98 和 0.96。MTA 在针铁矿上的吸附更适合 Freundlich 模型，其 R2 值为 0.9863。此外，提高 pH 值可以抑制 MTA 在这三种介质上的吸附，因为氧化铁是控制 MTA 吸附在它们上的主要因素。