Hunter Heather A, Ling Florence T, Peters Catherine A
Department of Civil & Environmental Engineering, Princeton University, Princeton, New Jersey.
Environ Eng Sci. 2020 Apr 1;37(4):235-245. doi: 10.1089/ees.2019.0447. Epub 2020 Apr 6.
Coprecipitation can be an effective treatment method for the removal of environmentally relevant metals from industrial wastewaters such as produced waters from the oil and gas industry. The precipitation of barite, BaSO, through the addition of sulfate removes barium while coprecipitating strontium and other alkaline earth metals even when these are present at concentrations below their solubility limit. Among other analytical methods, X-ray fluorescence (XRF) nanospectroscopy at the Hard X-ray Nanoprobe (HXN) beamline at the National Synchrotron Light Source II (NSLS-II) was used to quantify Sr incorporation into barite. Thermodynamic modeling of (Ba,Sr)SO solid solutions was done using solid solution-aqueous solution (SS-AS) theory. The quantitative, high-resolution nano-XRF data show clearly that the Sr content in (Ba,Sr)SO solid solutions varies widely among particles and even within a single particle. We observed substantial Sr incorporation that is far larger than thermodynamic models predict, likely indicating the formation of metastable solid solutions. We also observed that increasing barite supersaturation of the aqueous phase led to increased Sr incorporation, as predicted by available kinetic models. These results suggest that coprecipitation offers significant potential for designing treatment systems for aqueous metals' removal in desired metastable compositions. Solution conditions may be optimized to enhance the incorporation of Sr by increasing sulfate addition such that the barite saturation index remains above ∼3 or by increasing the aqueous Sr to Ba ratio.
共沉淀法可能是一种从工业废水中去除与环境相关金属的有效处理方法，比如石油和天然气行业产生的采出水。通过添加硫酸盐使重晶石（BaSO₄）沉淀，可以去除钡，同时使锶和其他碱土金属共沉淀，即使这些金属的浓度低于其溶解度极限。在其他分析方法中，利用美国国家同步辐射光源II（NSLS-II）的硬X射线纳米探针（HXN）光束线的X射线荧光（XRF）纳米光谱法来定量分析锶在重晶石中的掺入情况。采用固溶体-水溶液（SS-AS）理论对（Ba,Sr）SO₄固溶体进行了热力学建模。定量的高分辨率纳米XRF数据清楚地表明，（Ba,Sr）SO₄固溶体中的锶含量在颗粒之间甚至单个颗粒内部都有很大差异。我们观察到大量的锶掺入，其数量远大于热力学模型的预测值，这可能表明形成了亚稳固溶体。我们还观察到，正如现有动力学模型所预测的那样，水相中重晶石过饱和度的增加导致锶掺入量增加。这些结果表明，共沉淀法在设计用于去除水中金属以获得所需亚稳组成的处理系统方面具有巨大潜力。可以通过增加硫酸盐添加量以使重晶石饱和指数保持在约3以上，或者通过提高水相中锶与钡的比例来优化溶液条件，以增强锶的掺入。
