Han Joonkyoung, Nomaan Sheik Mohammad, Katz Lynn E
The University of Texas at Austin, Department of Civil, Architectural and Environmental Engineering, 301 E. Dean Keeton St. C1786, Austin, TX 78712, USA.
The University of Texas at Austin, Department of Civil, Architectural and Environmental Engineering, 301 E. Dean Keeton St. C1786, Austin, TX 78712, USA.
Sci Total Environ. 2023 Sep 20;892:164462. doi: 10.1016/j.scitotenv.2023.164462. Epub 2023 May 30.
As water scarcity drives the use of more saline water sources, contaminant fate and transport models must capture the impact of high concentrations of alkaline earth metal ions (AEMs) and background electrolytes in these more complex waters. By utilizing macroscopic adsorption data from various electrolyte systems, a Charge Distribution - Multisite Complexation (CD-MUSIC) model, capable of incorporating electrolyte adsorption, was able to accurately simulate the adsorption behavior of alkaline earth metal ions onto goethite. The modeling effort was guided by previous spectroscopic and surface complexation modeling of alkaline earth metal adsorption and built on previous CD-MUSIC modeling that accounted for changes in crystal face contributions to the surface site density as a function of specific surface area. The model was constrained to consider only two dominant surface complex species for each metal ion adsorption reaction. These two species were selected from 44 possible species through objective curve fitting of single-solute macroscopic adsorption data. While most of the alkaline earth metal surface complexes formed outer-sphere complexes at the goethite surface, an inner-sphere species was utilized for Mg. With the surface complex species and equilibrium constants obtained from this study, the calibrated model successfully predicted alkaline earth metal ion adsorption over a wide range of solution and surface conditions; the model predictions encompassed a wide range of pH (5-11), solute/solid ratio (1.37 × 10- 8.33 × 10 mol/g), ionic strengths (0.01 M - 0.7 M), and background electrolytes (Na, Cs, Rb, Cl, and NO) using the same crystal face contribution methodology for site density, capacitance values, and surface acidity constants adopted for proton and cadmium adsorption in previous work (Han and Katz, 2019). Model simulations for a range of background water chemistries demonstrated the potential for Mg to reduce Cd adsorption to goethite in model seawater and oil- and gas-produced waters.
随着水资源短缺促使人们使用更多的咸水资源，污染物的归宿和迁移模型必须考虑这些更复杂水体中高浓度碱土金属离子（AEMs）和背景电解质的影响。通过利用来自各种电解质系统的宏观吸附数据，一种能够纳入电解质吸附的电荷分布 - 多位点络合（CD - MUSIC）模型能够准确模拟碱土金属离子在针铁矿上的吸附行为。该建模工作以先前碱土金属吸附的光谱学和表面络合建模为指导，并建立在先前的CD - MUSIC建模基础上，该建模考虑了晶面对表面位点密度的贡献随比表面积的变化。该模型被限制为每个金属离子吸附反应仅考虑两种主要的表面络合物种。通过对单溶质宏观吸附数据进行客观曲线拟合，从44种可能的物种中选择了这两种物种。虽然大多数碱土金属表面络合物在针铁矿表面形成外层络合物，但对于Mg使用了内层物种。利用本研究获得的表面络合物种和平衡常数，校准后的模型成功预测了在广泛的溶液和表面条件下碱土金属离子的吸附；模型预测涵盖了广泛的pH范围（5 - 11）、溶质/固体比（1.37×10 - 8.33×10 mol/g）、离子强度（0.01 M - 0.7 M）以及背景电解质（Na、Cs、Rb、Cl和NO），使用了与先前工作（Han和Katz，2019）中质子和镉吸附所采用的相同的晶面对位点密度、电容值和表面酸度常数的贡献方法。一系列背景水化学的模型模拟表明，在模型海水以及油气生产水中，Mg有可能降低Cd在针铁矿上的吸附。
