Department of Civil and Environmental Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08826, South Korea.
Department of Civil and Environmental Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08826, South Korea.
Environ Pollut. 2021 Apr 1;274:116577. doi: 10.1016/j.envpol.2021.116577. Epub 2021 Jan 23.
Owing to its physicochemical similarity to strontium (Sr), calcium (Ca) was tested as a key component of a soil washing solution for Sr-contaminated soil collected near a nuclear power plant. A four-factor, three-level Box-Behnken experimental design combined with response surface modeling was employed to determine the optimal Sr washing condition for Ca-based solution. The Ca concentration (0.1-1 M), liquid-to-soil ratio (5-20), washing time (0.5-2 h), and pH (2.0-7.0) were tested as the independent variables. From the Box-Behnken design, 27 sets of experimental conditions were selected, and a second-order polynomial regression equation was derived. The significance of the independent parameters and interactions was tested by analysis of variance. Ca concentration was found to be the most influential factor. To determine whether the four variables were independent, three-dimensional (3D) response surface plots were established. The optimal washing condition was determined to be as follows: 1 M Ca, L/S ratio of 20, 1 h washing, and pH = 2. Under this condition, the highest Sr removal efficiency (68.2%) was achieved on a soil contaminated with 90.1 mg/kg of Sr. Results from five-step sequential extraction before and after washing showed that 84.0% and 82.9% of exchangeable and carbonate-bound Sr were released, respectively. In addition, more tightly bound Sr, such as Fe/Mn oxides-bound and organic matter-bound Sr, were also removed (86.2% and 64.5% removal, respectively).
由于其物理化学性质与锶（Sr）相似，因此钙（Ca）被测试为一种从核电站附近采集的受 Sr 污染土壤的土壤洗涤溶液的关键成分。采用四因素三水平 Box-Behnken 实验设计结合响应面建模来确定 Ca 基溶液用于 Sr 洗涤的最佳条件。Ca 浓度（0.1-1 M）、液固比（5-20）、洗涤时间（0.5-2 h）和 pH 值（2.0-7.0）作为独立变量进行测试。从 Box-Behnken 设计中，选择了 27 组实验条件，并得出了二次多项式回归方程。通过方差分析测试了独立参数和相互作用的显著性。发现 Ca 浓度是最具影响力的因素。为了确定这四个变量是否独立，建立了三维（3D）响应面图。确定的最佳洗涤条件如下：1 M Ca、L/S 比为 20、洗涤 1 h 和 pH=2。在此条件下，对 Sr 污染水平为 90.1 mg/kg 的土壤进行洗涤，Sr 的去除效率最高（68.2%）。洗涤前后五步连续提取的结果表明，可交换态和碳酸盐结合态 Sr 的释放量分别为 84.0%和 82.9%。此外，还去除了更紧密结合的 Sr，如 Fe/Mn 氧化物结合态和有机质结合态 Sr（去除率分别为 86.2%和 64.5%）。
