Temple University, Department of Civil and Environmental Engineering, 1947 North 12 Street, Philadelphia, PA 19122, United States.
Temple University, Department of Civil and Environmental Engineering, 1947 North 12 Street, Philadelphia, PA 19122, United States.
Sci Total Environ. 2021 Jan 1;750:142274. doi: 10.1016/j.scitotenv.2020.142274. Epub 2020 Sep 11.
The presence of dissolved organic matter (DOM) can impact metal sulfide (MeS) precipitation and mobility. Thiol containing ligands such as cysteine have been shown to be effective capping agents in single metal MeS studies, allowing NPs to persist in oxic environments. In this study, both single (Cd or Zn) and multi-MeS (Cu, Pb, Cd, Zn, and As) nanoparticle (NP) formation was characterized to understand the impact of the thiol cysteine (CYS) on early stage (3 h) MeS NP behavior. Short duration single metal batch experiments, in the absence and presence of CYS, confirmed that MeS species readily formed solids with limited dissolved fraction; however, multi-metal systems exhibited divergent behavior reflecting a wider range of NP sizes and an increased dissolved concentration. Multi-metal batch experiments revealed that metals were generally sequestered into MeS solids in accordance with MeS solubility products (i.e., from least to most soluble: Cu > Pb ~ Cd > Zn). CYS concentrations in excess of sulfide (10:1 CYS:S ratio) stabilized MeS within the Small NP size fraction (3.2 nm < d < 43 nm) and limited Pb, Cd, and Zn dissolution compared to molar ratios of 1:1. In the combined presence of CYS and Ca, multi-MeS particle aggregation increased substantially compared to monovalent systems. Dissolution increased for Pb and Zn as a function of matrix ionic strength whereas dissolved Cu trends changed as a function of cation valence state (e.g., Na vs. Ca). Most noteworthy, single-metal Zn and Cd batch experiments demonstrated that single-metal studies can overestimate MeS NP resistance to oxidative dissolution compared to multi-metal counterparts. Thus, caution should be taken when broadly applying mechanisms and rates elucidated from single-metal systems.
溶解有机质 (DOM) 的存在会影响金属硫化物 (MeS) 的沉淀和迁移。含巯基的配体，如半胱氨酸，已被证明在单金属 MeS 研究中是有效的封端剂，使 NPs 能够在氧化环境中存在。在这项研究中，我们对单金属 (Cd 或 Zn) 和多金属 (Cu、Pb、Cd、Zn 和 As) MeS 纳米颗粒 (NP) 的形成进行了特征描述，以了解巯基半胱氨酸 (CYS) 对早期 MeS NP 行为的影响。在不存在和存在 CYS 的情况下，进行了短期单金属批量实验，证实 MeS 物种很容易形成固体，溶解部分有限；然而，多金属体系表现出不同的行为，反映出更广泛的 NP 尺寸范围和增加的溶解浓度。多金属批量实验表明，金属通常按照 MeS 溶解度积 (即，从最不溶性到最可溶性：Cu > Pb ~ Cd > Zn) 被螯合到 MeS 固体中。CYS 浓度超过硫化物 (10:1 CYS:S 比) 稳定了小 NP 尺寸部分 (3.2nm < d < 43nm) 的 MeS，与摩尔比为 1:1 相比，限制了 Pb、Cd 和 Zn 的溶解。在 CYS 和 Ca 的共同存在下，与单价体系相比，多金属 MeS 颗粒的聚集大大增加。随着基质离子强度的增加，Pb 和 Zn 的溶解增加，而 Cu 的溶解趋势则随阳离子价态的变化而变化（例如，Na 与 Ca）。最值得注意的是，单金属 Zn 和 Cd 批量实验表明，与多金属相比，单金属研究可能高估了 MeS NP 对氧化溶解的抵抗力。因此，在广泛应用单金属体系中阐明的机制和速率时应谨慎。
