School of Environment and Energy, South China University of Technology, Guangzhou 510006, China.
School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China.
Sci Total Environ. 2021 Sep 1;785:147367. doi: 10.1016/j.scitotenv.2021.147367. Epub 2021 Apr 27.
Metal sulfides, which are important indicators of sulfur cycling, are usually divided into two categories according to sulfur chemical valence: (1) monosulfides (S) and (2) disulfides (S). The two sulfur species are separated and quantified by a sequential-extraction method. Specifically, monosulfides are extracted as acid-volatile sulfide (AVS) using 6 M HCl prior to the extraction of disulfides using acidic CrCl, which is defined as chromium-reducible sulfur (CRS). However, the conventional AVS procedure does not result in the quantitative extraction of S from the acid-insoluble metal monosulfide, copper sulfide (CuS). Consequently, residual sulfur in CuS (CuS-S) may be extracted as CRS resulting in the inaccurate separation of these two sulfur species. In this study, we used stannous chloride (SnCl) to improve CuS-S recovery in the AVS procedure and permit the separate extraction of sulfur from CuS and pyrite (FeS), the most abundant disulfide in nature. Our results show that the addition of SnCl increased the recovery of CuS-S as AVS from less than 36% to as high as 92% in the absence of pyrite and Fe and 89% in the presence of pyrite and Fe. In addition, based on the observed correlation between the concentration of SnCl and the dissolution of FeS, we identified the appropriate concentration of SnCl needed to avoid the dissolution of FeS in the AVS procedure. SnCl also minimized the oxidation of CuS-S by Fe released from ferric minerals during the extraction of AVS. Based on the results of a series of sequential-extraction experiments, we show that an amendment of SnCl in the AVS procedure followed by CRS permits the quantitative separation of CuS-S and FeS-S while also preventing interference by Fe. Our method will find application in research concerned with the fate of metals and the biogeochemistry of sulfur in the environment.
金属硫化物是硫循环的重要指标，通常根据硫的化学价分为两类：(1) 单硫化物 (S) 和 (2) 双硫化物 (S)。这两种硫物种通过连续提取方法分离和定量。具体来说，单硫化物用 6 M HCl 作为酸挥发性硫化物 (AVS) 提取，然后用酸性 CrCl 提取双硫化物，定义为铬还原硫 (CRS)。然而，传统的 AVS 程序并不能从酸不溶性金属单硫化物(硫化铜 (CuS)) 中定量提取 S。因此，CuS 中的残留硫 (CuS-S) 可能会作为 CRS 被提取出来，从而导致这两种硫物种的分离不准确。在本研究中，我们使用氯化亚锡 (SnCl) 来改进 AVS 程序中 CuS-S 的回收，并允许从 CuS 和黄铁矿 (FeS) 中单独提取硫，FeS 是自然界中最丰富的双硫化物。我们的结果表明，在没有黄铁矿和 Fe 的情况下，添加 SnCl 可将 CuS-S 的 AVS 回收率从不到 36% 提高到高达 92%，而在存在黄铁矿和 Fe 的情况下回收率为 89%。此外，基于观察到的 SnCl 浓度与 FeS 溶解之间的相关性，我们确定了在 AVS 程序中避免 FeS 溶解所需的适当 SnCl 浓度。SnCl 还最大限度地减少了在提取 AVS 过程中从铁矿物中释放的 Fe 对 CuS-S 的氧化。基于一系列连续提取实验的结果，我们表明，在 AVS 程序中添加 SnCl 后再进行 CRS 提取，可以定量分离 CuS-S 和 FeS-S，同时防止 Fe 的干扰。我们的方法将应用于研究金属的命运和环境中硫的生物地球化学。
