School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China; Soil Remediation Research Center of Sun Yat-sen University and Zhisheng Environmental Protection Group Ltd., Guangzhou, 510275, China.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China; Guangdong Provincial Key Lab of Environmental Pollution and Remediation Technology, Guangzhou, 510275, China; Shenzhen Research Institute, Sun Yat-sen University, Shenzhen, 518057, China.
Chemosphere. 2018 Nov;211:1035-1042. doi: 10.1016/j.chemosphere.2018.07.088. Epub 2018 Jul 23.
A two stage multi-fraction 1-order kinetic model was established herein, which incorporates Cd species distribution in the contaminated site, chelate dosage and washing time, and two distinct extraction mechanisms are also emphasized there. The model was found to successfully simulate the experimental data of Cd extraction by EDTA; with the obtained parameters, we also got a similarly good agreement in other two Cd-contaminated soils. All normalized root-mean-square error, the index of agreement and modeling efficiency values showed that this model can be used to predict Cd kinetic extraction process in different types of soils with an excellent validity. Both simulated and experimental results indicate that a greater EDTA dosage reasonably leads to a higher Cd extraction efficiency and a faster extraction by the direct EDTA-complex. Different Cd species also show different extraction behavior. Part of Cd species associated with Fe/Mn hydro(oxides) (FeMnOx) become destabilized by slow EDTA-promoted dissolution but not yet detached, leading to an apparently high removal efficiency of Cd in FeMnOx fraction dependent on EDTA dosage. While the removal of exchangeable Cd and carbonates (EXCH+CARB) seemed unchanged with the EDTA dosage, due to the transformation of the undetached Cd in FeMnOx fractions. However, an extreme dosage (i.e. molar ratio of EDTA to metal equal to 20 herein) may accelerate the detachment of these destabilized Cd species, resulting in a substantially high extraction efficiency of EXCH+CARB fraction.
本文建立了一个两阶段多分数 1 阶动力学模型，该模型结合了污染场地中 Cd 物种的分布、螯合剂用量和洗涤时间，还强调了两种不同的提取机制。该模型成功地模拟了 EDTA 提取 Cd 的实验数据；通过获得的参数，我们在另外两种 Cd 污染土壤中也得到了类似的良好拟合。所有归一化均方根误差、一致性指数和模型效率值均表明，该模型可用于预测不同类型土壤中 Cd 动力学提取过程，具有很好的有效性。模拟和实验结果均表明，更大的 EDTA 用量会导致更高的 Cd 提取效率和更快的直接 EDTA 配合物提取。不同的 Cd 物种也表现出不同的提取行为。一部分与 Fe/Mn 氢氧化物（FeMnOx）结合的 Cd 物种由于缓慢的 EDTA 促进溶解而变得不稳定，但尚未脱离，导致 FeMnOx 部分中 Cd 的去除效率明显较高，这取决于 EDTA 用量。而可交换态 Cd 和碳酸盐（EXCH+CARB）的去除似乎不受 EDTA 用量的影响，这是由于 FeMnOx 部分中未脱离的 Cd 发生了转化。然而，极端的用量（即本文中 EDTA 与金属的摩尔比等于 20）可能会加速这些不稳定 Cd 物种的脱离，从而导致 EXCH+CARB 部分的提取效率大幅提高。
