Abstract：
This study aimed to evaluate the effect of modified nanoscale zero-valent iron (SAS-nZVI) on chemical leaching of lead and cadmium composite contaminated soil by citric acid (CA). The synthesized SAS-nZVI was used as a leaching aid to improve the removal rate of soil heavy metals (HMs) by CA chemical leaching. The effects of various factors such as SAS-nZVI dosage, elution temperature and elution time were studied. At the same time, the effect of chemical leaching on the basic physical and chemical properties of soil and the morphology of HMs was evaluated. The results show that when the SAS-nZVI dosage is 2.0 g/L, the leaching temperature is 25 °C, and the leaching time is 720 min, the maximum removal rates of Pb and Cd in the soil are 77.64% and 97.15% respectively. The experimental results were evaluated using elution and desorption kinetic models (Elovich model, double constant model, diffusion model). The elution and desorption process of Pb and Cd in soil by SAS-nZVI-CA fitted well with the double-constant model, indicating that the desorption kinetic process of Pb and Cd is a heterogeneous diffusion process, and the elution process is controlled by diffusion factors. After leaching with SAS-nZVI-CA, the physical and chemical properties of the soil changed little, the mobility and toxicity of HMs in the soil were reduced, and the HMs content in the leaching waste liquid was reduced. It can be concluded that SAS-nZVI enhances the efficiency of CA in extracting Pb and Cd from soil, minimizes soil damage resulting from chemical leaching technology, and alleviates the challenges associated with treating leaching waste liquid.
摘要：
本研究旨在评价改性纳米零价铁(SAS-nZVI)对柠檬酸(CA)对铅镉复合污染土壤化学淋洗的影响。将合成的SAS-nZVI用作浸出助剂，以提高CA化学浸出对土壤重金属（HMs）的去除率。SAS-nZVI剂量等各种因素的影响，研究了洗脱温度和洗脱时间。同时,评价了化学淋洗对土壤基本理化性质和HMs形态的影响。结果表明,当SAS-nZVI投加量为2.0g/L时,浸出温度为25°C，浸出时间为720分钟，土壤中Pb和Cd的最大去除率分别为77.64%和97.15%。使用洗脱和解吸动力学模型(Elovich模型，双常数模型,扩散模型)。SAS-nZVI-CA对土壤中Pb和Cd的洗脱和解吸过程与双常数模型拟合较好,表明Pb和Cd的解吸动力学过程是非均相扩散过程，洗脱过程受扩散因素控制。用SAS-nZVI-CA浸出后，土壤的理化性质变化不大,HMs在土壤中的流动性和毒性降低，浸出废液中HMs含量降低。可以得出结论，SAS-nZVI提高了CA从土壤中提取Pb和Cd的效率，将化学浸出技术造成的土壤损害降至最低，并缓解了与处理浸出废液相关的挑战。
