Abstract:Using ZnCl2 and Sulfur as modifier, modified biochar based on cornstalk was prepared through utilizing limited oxygen pyrolysis process, and the best preparation conditions of modified biochar were explored by an orthogonal experiment. Modified biochar stabilization effect of mercury contaminated soil was tested and evaluated using concentrations of different mercury forms in soil leach as index, and the optimum adding amount of modified biochar was determined. The results showed that ZnCl2 and sulfur modified biochar could improve the stabilization effect of mercury in soil. The stabilizing effect of ZnCl2 and sulfur modified biochar is significantly higher than that of ZnCl2 or sulfur modified biochar alone. After modified biochar treatment, the exchangeable mercury in the leaching solution of mercury-contaminated soil decreased, while the content of organic binding mercury and residual mercury increased. The stabilization effect of ZnCl2 and sulfur co-modified biochar was significantly higher than that of ZnCl2 or sulfur modified biochar. The optimal preparation conditions of co-modified biochar were 30% ZnCl2, 5% sulfur and 1 h carbonation at 350 ℃. The optimal amount of co-modified biochar was 2%, and the mercury content in the soil leachate was 0.57 μg·L?1, far lower than the mercury limit of GB 5085.3-2007 (0.1 mg·L?1), which could greatly reduce the environmental risk of mercury in soil. Key words:biochar modification/ heavy metal pollution/ mercury contamination soil remediation/ soil stabilization.
图1不同改性剂对稳定化效果的影响 Figure1.Effects of different modifiers on biochar stabilization ability
SANCHEZ F, MATTUS C H, MORRIS M I, et al. Use of a new leaching test framework for evaluating alternative Treatment processes for mercury-contaminated soils[J]. Environmental Engineering Science, 2002, 19(4): 251-269. doi: 10.1089/109287502760271562
[5]
SYVERSEN T, KAUR P. The toxicology of mercury and its compounds[J]. Journal of Trace Elements in Medicine and Biology, 2012, 26(4): 215-226. doi: 10.1016/j.jtemb.2012.02.004
[6]
WALLSCHLl?GER D, DESAI M V M, SPENGLER M, et al. Mercury speciation in floodplain soils and sediments along a contaminated river transect[J]. Journal of Environmental Quality, 1998, 27(5): 1034-1044.
PAZ-FERREIRO J, LU H, FU S, et al. Use of phytoremediation and biochar to remediate heavy metal polluted soils: A review[J]. Solid Earth, 2014, 5(1): 65-75. doi: 10.5194/se-5-65-2014
[10]
SOHI S P, KRULL E, LOPEZ-CAPEL E, et al. A review of biochar and its use and function in soil[J]. Advances in Agronomy, 2010, 105(1): 47-82.
TAN G, XU N, XU Y, et al. Sorption of mercury (II) and atrazine by biochar, modified biochars and biochar based activated carbon in aqueous solution[J]. Bioresource Technology, 2016: S0960852416304503.
[18]
O'CONNOR D, PENG T, LI G H, et al. Sulfur-modified rice husk biochar: A green method for the remediation of mercury contaminated soil[J]. Science of the Total Environment, 2017, 621: 819-826.
[19]
LIU P, PTACEK C J, ELENA K, et al. Evaluation of mercury stabilization mechanisms by sulfurized biochars determined using X-ray absorption spectroscopy[J]. Journal of Hazardous Materials, 2018, 347: 114-122. doi: 10.1016/j.jhazmat.2017.12.051
[20]
DUAN X L, YUAN C G, JING T T, et al. Removal of elemental mercury using large surface area micro-porous corn cob activated carbon by zinc chloride activation[J]. Fuel, 2019, 239: 830-840. doi: 10.1016/j.fuel.2018.11.017
[21]
HONG D Y, ZHOU J S, HU C X, et al. Mercury removal mechanism of AC prepared by one-step activation with ZnCl2[J]. Fuel, 2019, 235: 326-335. doi: 10.1016/j.fuel.2018.07.103
1.School of Metallurgy, Northeastern University, Shenyang 110819, China 2.Shenyang Academy of Environmental Sciences, Shenyang 110167, China Received Date: 2020-08-11 Accepted Date: 2020-09-09 Available Online: 2021-04-23 Keywords:biochar modification/ heavy metal pollution/ mercury contamination soil remediation/ soil stabilization Abstract:Using ZnCl2 and Sulfur as modifier, modified biochar based on cornstalk was prepared through utilizing limited oxygen pyrolysis process, and the best preparation conditions of modified biochar were explored by an orthogonal experiment. Modified biochar stabilization effect of mercury contaminated soil was tested and evaluated using concentrations of different mercury forms in soil leach as index, and the optimum adding amount of modified biochar was determined. The results showed that ZnCl2 and sulfur modified biochar could improve the stabilization effect of mercury in soil. The stabilizing effect of ZnCl2 and sulfur modified biochar is significantly higher than that of ZnCl2 or sulfur modified biochar alone. After modified biochar treatment, the exchangeable mercury in the leaching solution of mercury-contaminated soil decreased, while the content of organic binding mercury and residual mercury increased. The stabilization effect of ZnCl2 and sulfur co-modified biochar was significantly higher than that of ZnCl2 or sulfur modified biochar. The optimal preparation conditions of co-modified biochar were 30% ZnCl2, 5% sulfur and 1 h carbonation at 350 ℃. The optimal amount of co-modified biochar was 2%, and the mercury content in the soil leachate was 0.57 μg·L?1, far lower than the mercury limit of GB 5085.3-2007 (0.1 mg·L?1), which could greatly reduce the environmental risk of mercury in soil.