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| Effects and mechanisms of nano zero-valent iron-modified biochar on Cd stabilization in contaminated soils |
| Received:February 27, 2022 |
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| KeyWord:Cd;nano zero-valent iron modified biochar（nZVI-BC）;remediation of contaminated soil;stabilizing mechanism |
| Author Name | Affiliation | E-mail | | XU Yaqiong | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | | | WANG Xuejia | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | | | LI Ronghua | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | | | XIAO Ran | Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, Southwest University, Chongqing 400715, China
College of Resources and Environment, Key Laboratory of Efficient Utilization of Soil and Fertilizer Resources, Southwest University, Chongqing 400715, China | | | ZHANG Zengqiang | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | zhangzq58@126.com |
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| Abstract: |
| To study the long-term stabilization mechanisms of nano zero-valent iron-modified biochar（nZVI-BC）on soil Cd, especially the interfacial interaction between nZVI-BC and Cd during the aging process of biochar, the influence of nZVI-BC on Cd immobilization in neutral-alkaline soils was investigated using combined methods（including batch adsorption experiments and simulation trials） and characterized using novel spectrum analysis techniques. The results showed that the nZVI loading significantly improved the adsorption capacity of biochar for Cd（Ⅱ）, and the saturated adsorption capacity of nZVI-BC for Cd（Ⅱ）was 4.3 times higher than that of BC（125.5 mg·g-1 vs 23.61 mg·g-1）. The adsorption of Cd（Ⅱ）by nZVI-BC agreed with the Pseudo-second-order kinetic equation, and the adsorption process was mainly chemical adsorption. Its isothermal adsorption was more consistent with the Langmuir model, which belongs to monolayer adsorption. With the increase in culture time, the Cd loading on the surface of the biochar gradually increased, and the oxygen-containing functional groups formed on the BC surface after aging were the main reason for the increase in Cd saturation adsorption capacity. In contrast, the Cd load on the nZVI-BC first increased and then decreased gradually. Precipitation and surface complexation were the main mechanisms for nZVI-BC to fix Cd in the soil, and the reduction of Fe content and oxidation were the main reasons for the reduction of Cd fixation. However, the adsorption of Cd by nZVI-BC remained at a high level and was much higher than that of BC. In conclusion, nZVI-BC can be used as a highly effective stabilizing material for Cd remediation in moderately polluted farmlands. |
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