绿色合成纳米氧化铁对污染土壤中镉的钝化研究

虽然绿色合成纳米材料已成功地用于去除废水中的重金属,但利用绿色合成纳米材料钝化土壤中重金属的报道很少.本文利用植物叶提取液制备纳米氧化铁(GION),并将其用于钝化土壤中重金属镉的研究,观察中、短培养周期下对镉钝化的稳定性.实验室条件下设置50%田间最大持水量培养,对照、1%、3%、9%GION 4个处理.分别于第60、120 d采样分析土壤中镉、pH、铁、酶等相关指标的变化.结果表明,GION对土壤中镉有较好的钝化效果,60 d与120 d之间有效态镉的含量无显著差异,说明GION对土壤中镉的钝化作用随时间增长相对稳定.120 d的数据显示,相比对照组,1%、3%、9%GION处理下有效态Cd(0.1 mol·L~(-1) CaCl_2)分别降低了19.1%、16.7%、66.7%,交换态Cd(Tessier法)分别降低了12.5%、18.8%、56.3%.GION能够显著提高土壤的pH和铁的含量.pH提高能够显著降低Cd的有效性.(NH_4)C_2O_4-Fe则分别增加了0.7、1.1、1.9倍,DCB-Fe分别增加了0.4、2.9、6.0倍.另外,随培养时间的延长,(NH_4)C_2O_4-Fe和DCB-Fe增加而HCl-Fe~(2+)含量降低.说明GION影响土壤中铁物种的活性,增强其生物化学过程而转化为更加稳定的形态,该过程将改变镉在土壤中的赋存形态.通过扫描电镜-能谱(SEM-EDS)发现,GION处理残渣态中Fe的含量远高于对照组,说明镉可能随铁进入残渣态.土壤中脲酶和转化酶活性升高而过氧化氢酶则没有显著的变化.该结果说明GION降低了土壤中镉的生物有效性,土壤得以恢复,从而提升了土壤酶活性.综上所述,GION具有环境友好的特点,且对镉具有稳定的钝化作用,可作为一种良好的中低污染重金属污染土壤的修复剂.

Immobilization of cadmium in soil by green synthesized iron oxide nanoparticles

Green synthesized nanomaterials have been successfully used to remove heavy metals in wastewater, immobilizing heavy metals in soils is still unclear.In this study, iron oxide nanoparticles (GION) were prepared from euphorbia cochinchinensis extract and following used to immobilize cadmium (Cd) in soil, where soil was tested under after 60 and 120 d incubation with a 50% water hold capacity with control.Results show 1the Cd in soil were immobilized effectively by GION, and there was no significantly difference between 60 and 120 d, indicating that the immobilization of Cd by GION was stability in 60 d and 120 d incubation.At 120 d, the available Cd (0.1 mol·L^-1 CaCl₂) in the 1%, 3% and 9% GION treatments decreased by 19.1%, 16.7%, 66.7%, and he exchangeable Cd (Tessier) decreased by 12.5%, 18.8%, 56.3% respectively.2the pH and Fe species in soil increased with increasing GION dosage, resulting in decreasing the available of Cd effectively.With increasing in pH.The (NH₄)C₂O₄-Fe and DCB-Fe increased by 0.4, 2.9, 6.0 times and 0.7, 1.1 and 1.9 times, respectively.In addition, in the GION treatments, (NH₄)C₂O₄-Fe and DCB-Fe increased, while HCl-Fe²⁺ decreased with incubation time, indicating that GION affected the activity of iron species in soil, and enhancing its biochemical process and transform it into a more stable fractions, leading to further change the fraction of Cd in soil by SEM-EDS. Furthermore, the abundance of Fe in the 9% GION treatment was much higher than that of the control.3the activity of urease and invertase activity increased, while catalase did not change significantly, revealing that GION immobilized Cd by reducing the bioavailability of cadmium in soil, resulting in the increasing enzyme activity.Since GION is environmentally friendly and in the stable immobilizing Cd.GION could be potentially used to Cd in contaminated soil.