State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, 400044, China; Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing, 400044, China.
Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing, 400044, China.
Environ Res. 2020 Nov;190:109992. doi: 10.1016/j.envres.2020.109992. Epub 2020 Aug 5.
Cr(VI)-contaminated soils could be remediated by using calcium polysulfide (CPS), while natural iron oxides as a main composition of soil would influence the pathways of the remediation. Through kinetic batch tests, the kinetics of Cr(VI) removal from soil, the effects of the contents of natural iron oxides, soil environmental conditions and mechanisms of Cr(VI) removal by using CPS with the presence of natural iron oxides were investigated. The results show that the removal of Cr(VI) by using CPS in soil fitted the pseudo-second-order model best, and the appearance of goethite increased the apparent rate constant from 0.0002 kg mg h to 0.0005 kg mg h. The presence of iron oxides enhanced the removal of Cr(VI) by using CPS, and an extended reductive atmosphere of soil was created. The enhancement of Cr(VI) removal increased with the contents of iron oxides from 0 to 9 g kg, and declined from 9 to 12 g kg. Acidic environment favored the removal of Cr(VI) from soil by using CPS with or without the iron oxides compared to neutral soil and increased it from 87% to 100% because of proton-consuming reactions and electrostatic attraction. Twenty-nine percent of exchangeable and bound-to-carbonates species of chromium declined after the remediation, while 24% bound-to-iron-and-manganese-oxide species increased simultaneously. The findings of the study indicate that natural iron oxides in soils catalyze the reduction of Cr(VI) in soil and facilitate significantly the remediation of Cr(VI)-contaminated soil by using CPS.
六价铬污染土壤可以用多硫化钙（CPS）进行修复，而土壤中天然氧化铁作为主要成分会影响修复途径。通过动力学批量试验，研究了 CPS 去除土壤中六价铬的动力学、天然氧化铁含量、土壤环境条件的影响以及 CPS 存在下天然氧化铁去除六价铬的机理。结果表明，CPS 在土壤中去除六价铬最符合准二级模型，针铁矿的出现使表观速率常数从 0.0002kgmg h 增加到 0.0005kgmg h。氧化铁的存在增强了 CPS 对六价铬的去除作用，并创造了一个扩展的还原性土壤气氛。增强的六价铬去除作用随着氧化铁含量从 0 增加到 9gkg 而增加，然后从 9gkg 下降到 12gkg。与中性土壤相比，酸性环境有利于 CPS 去除土壤中的六价铬，与没有氧化铁相比，这一比例从 87%增加到 100%，这是由于质子消耗反应和静电吸引。修复后，29%的可交换和结合碳酸盐的铬减少，而 24%的结合铁和锰氧化物的铬同时增加。研究结果表明，土壤中的天然氧化铁催化了土壤中六价铬的还原，显著促进了 CPS 对六价铬污染土壤的修复。
