水泥-生石灰对铬污染土固化效果及微观孔隙特征的影响
|
摘要
为评价水泥和生石灰对铬污染土壤的固化效果及固化土在工程中再利用的可行性,采用固化稳定法进行六价铬污染土壤的修复试验,将重铬酸钾(K_2CrO_7)人工添加至粉砂土以模拟污染土,通过无侧限抗压强度、浸出毒性、核磁共振孔隙和微观三维形貌试验,研究水泥和生石灰对铬污染土的固化效果及其微观孔隙特征。结果表明:固化土强度随龄期增加而显著增加,且达到废弃物的填埋标准,同时随六价铬离子浓度增大强度先增加后稳定或减少;六价铬离子浓度小于900 mg·kg~(-1)时,生石灰掺量对于固化土强度存在阈值为4%,低于4%时随着生石灰掺量增加强度呈上升趋势,浸出毒性降低且达到浸出标准,同时0.1~1μm孔隙占比最高,结构致密;高于4%时随着生石灰掺量增加强度呈下降趋势,浸出毒性波动变化,1~10μm的大孔径增多,结构致密性差,平整度降低。研究表明,掺入合适比例的水泥和生石灰对铬污染土有较好的固化效果,可防控受污染土壤中六价铬浸出和渗透到地下水带来的环境问题。
This study evaluated soils contaminated with heavy metals in terms of the solidification effect, prevention of migration of heavy metal ions, reduction of the significant drop in mechanical properties of the soil structure, and reuse in other projects, potassium dichromate(K2 Cr O7)was manually added to silt soil to simulate contaminated soil, based on the method of solidification stability. Unconfined compressive strength testing, leaching testing, nuclear magnetic resonance testing, and three-dimensional microtopography testing of soil samples were performed to study the curing effect and micropore characteristics of chromium-polluted soil under the coupling effect of cement and quicklime. The results were as follows:The strength of the soil increased significantly with age and reached the landfill waste standards; at the same time, the strength increased first and then stabilized or decreased with an increase in hexavalent chromium ion concentration.When the hexavalent chromium ion concentration was less than 900 mg·kg~(-1), the amount of quicklime had a threshold value of 4% for the strength of hardened soil. Below the threshold value, the strength of the hardened soil showed an upward trend with increasing quicklime content. The leaching toxicity decreased and satisfied standard requirements, with the pore size distribution concentrated in the range 0.1~1μm and the structure compact. Above the threshold value, the strength of the hardened soil showed a downward trend with increasing quicklime content; the fluctuation in leaching toxicity increased as the pore size increased; and the proportion of the pore size range 1~10 μm increased, while the compactness and evenness reduced. This study provides a reference for solving environmental problems caused by leaching of six-valent chromium from contaminated soil and its permeation to groundwater.
This study evaluated soils contaminated with heavy metals in terms of the solidification effect, prevention of migration of heavy metal ions, reduction of the significant drop in mechanical properties of the soil structure, and reuse in other projects, potassium dichromate(K2 Cr O7)was manually added to silt soil to simulate contaminated soil, based on the method of solidification stability. Unconfined compressive strength testing, leaching testing, nuclear magnetic resonance testing, and three-dimensional microtopography testing of soil samples were performed to study the curing effect and micropore characteristics of chromium-polluted soil under the coupling effect of cement and quicklime. The results were as follows:The strength of the soil increased significantly with age and reached the landfill waste standards; at the same time, the strength increased first and then stabilized or decreased with an increase in hexavalent chromium ion concentration.When the hexavalent chromium ion concentration was less than 900 mg·kg~(-1), the amount of quicklime had a threshold value of 4% for the strength of hardened soil. Below the threshold value, the strength of the hardened soil showed an upward trend with increasing quicklime content. The leaching toxicity decreased and satisfied standard requirements, with the pore size distribution concentrated in the range 0.1~1μm and the structure compact. Above the threshold value, the strength of the hardened soil showed a downward trend with increasing quicklime content; the fluctuation in leaching toxicity increased as the pore size increased; and the proportion of the pore size range 1~10 μm increased, while the compactness and evenness reduced. This study provides a reference for solving environmental problems caused by leaching of six-valent chromium from contaminated soil and its permeation to groundwater.
引文
[1]樊浩伦,申向东,周海龙,等.水泥固化锌污染红黏土强度与微观孔隙特征[J].农业环境科学学报,2016,35(6):1064-1070.FAN Hao-lun,SHEN Xiang-dong,ZHOU Hai-long,et al.Strength and micropore characteristics of cement-solidified/stabilized zinc-contaminated red clay[J].Journal of Agro-Environment Science,2016,35(6):1064-1070.
[2]王凤永,郭朝晖,苗旭峰,等.东方香蒲(Typha orientalis Presl)对重度污染土壤中As、Cd、Pb的耐性与累积特征[J].农业环境科学学报,2011,30(10):1966-1971.WANG Feng-yong,GUO Zhao-hui,MIAO Xu-feng,et al.Tolerance and accumulation characteristics of Typha orientalis Presl for As,Cd and Pb in heavily contaminated soils[J].Journal of Agro-Environment Science,2011,30(10):1966-1971.
[3]单鑫,陈荟蓉,禹洪丽,等.不同炭材料吸附Cr(Ⅵ)的热力学研究[J].环境工程学报,2016,10(3):1109-1115.SHAN Xin,CHEN Hui-Rong,YU Hong-li,et al.Study of thermodynamics for adsorption of Cr(Ⅵ)by different carbon materials[J].Chinese Journal of Environmental Engineering,2016,10(3):1109-1115.
[4]夏星辉,陈静生.土壤重金属污染治理方法研究进展[J].环境科学,1997,18(3):72-76,94-95.XIA Xing-hui,CHEN Jing-sheng.Advances in the study of remediation methods of heavy metal-contaminated soil[J].Chinese Journal of Environmental Science,1997,18(3):72-76,94-95.
[5]蒋忠.异位污染土壤修复设备关键部件设计分析及送料控制策略的研究[D].上海:华东理工大学,2015.JIANG Zhong.The Design and analysize of key parts and research of the feeding control strategy of the ex-situ soil remediation equipment[D].Shanghai:East China University of Science and Technology,2015.
[6]李玲,唐晓声,李海建.六价铬污染土壤还原稳定修复[J].广东化工,2016,43(3):95-96.LI Ling,TANG Xiao-sheng,LI Hai-jian.Reduction and stabilization remediation of hexavalent chromium contaminated soil[J].Guangdong Chemical Industry,2016,43(3):95-96.
[7]韩超,申向东,薛慧君,等.镉污染土在水泥-粉煤灰-石灰共同作用下固化效果及孔隙特征[J].农业环境科学学报,2017,36(4):686-693.HAN Chao,SHEN Xiang-dong,XUE Hui-jun,et al.Curing effect and pore characteristics of cadmium contaminated soil under the action of cement-fly ash-lime[J].Journal of Agro-Environment Science,2017,36(4):686-693.
[8]姚武,佘安明,杨培强.水泥浆体中可蒸发水的1H核磁共振弛豫特征及状态演变[J].硅酸盐学报,2009,37(10):1602-1606.YAO Wu,SHE An-ming,YANG Pei-qiang.1H-NMR relaxation and state evolvement of evaporable water in cement pastes[J].Journal of the Chinese Ceramic Society,2009,37(10):1602-1606.
[9]Coates G R,Xiao L Z,Prammer M G.NMR logging:Principles and applications[M].Houston:Haliburton Energy Services,1999.
[10]薛慧君,申向东,邹春霞,等.水泥土早期力学性能影响因素分析[J].硅酸盐通报,2014,33(8):2056-2062.XUE Hui-jun,SHEN Xiang-dong,ZOU Chun-Xia,et al.Analysis of the factors affecting the early mechanical properties of cement soil[J].Bulletin of the Chinese Ceramic Society,2014,33(8):2056-2062.
[11]宋学庆.水泥固化锌离子污染土力学特性试验研究[J].工程勘察,2016,44(6):28-32.SONG Xue-qing,Experimental study on mechanical properties of zinc ion contaminated soils stabilized by cement[J].Geotechnical Investigation&Surveying,2016,44(6):28-32.
[12]UK Environment Agency.Waste acceptance at landfills:Guidance on waste acceptance procedures and criteria[EB/OL].[2017-10-19].https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/296422/geho1110btew-e-e.pdf.
[13]贾尚华,申向东,解国梁.石灰-水泥复合土增强机制研究[J].岩土力学,2011,32(增刊1):382-387.JIA Shang-hua,SHEN Xiang-dong,XIE Guo-liang.Reinforcement mechanism of lime-cement soil[J].Rock and Soil Mechanics,2011,32(Suppl 1):382-387.
[14]李喜林,张佳雯,陈冬琴,等.水泥固化铬污染土强度及浸出试验研究[J].硅酸盐通报,2017,36(3):979-983,990.LI Xi-lin,ZHANG Jia-wen,CHEN Dong-qin,et al.Strength and leaching for remediation of chromium contaminated soil using cement[J].Bulletin of the Chinese Ceramic Society,2017,36(3):979-983,990.
[15]刘玲,刘海卿,张颖,等.石灰和粉煤灰固化修复六价铬污染土试验研究[J].硅酸盐通报,2015,34(11):3361-3365.LIU ling,LIU Hai-qing,ZHANG Ying,et al.Experimental study of lime and fly ash for solidification remediation of hexavalent chromium contaminated soil[J].Bulletin of the Chinese Ceramic Society,2015,34(11):3361-3365.
[16]Li X,Zhang L M.Characterization of dual-structure pore-size distribution of soil[J].Canadian Geotechnical Journal,2009,46(2):129-141.
[2]王凤永,郭朝晖,苗旭峰,等.东方香蒲(Typha orientalis Presl)对重度污染土壤中As、Cd、Pb的耐性与累积特征[J].农业环境科学学报,2011,30(10):1966-1971.WANG Feng-yong,GUO Zhao-hui,MIAO Xu-feng,et al.Tolerance and accumulation characteristics of Typha orientalis Presl for As,Cd and Pb in heavily contaminated soils[J].Journal of Agro-Environment Science,2011,30(10):1966-1971.
[3]单鑫,陈荟蓉,禹洪丽,等.不同炭材料吸附Cr(Ⅵ)的热力学研究[J].环境工程学报,2016,10(3):1109-1115.SHAN Xin,CHEN Hui-Rong,YU Hong-li,et al.Study of thermodynamics for adsorption of Cr(Ⅵ)by different carbon materials[J].Chinese Journal of Environmental Engineering,2016,10(3):1109-1115.
[4]夏星辉,陈静生.土壤重金属污染治理方法研究进展[J].环境科学,1997,18(3):72-76,94-95.XIA Xing-hui,CHEN Jing-sheng.Advances in the study of remediation methods of heavy metal-contaminated soil[J].Chinese Journal of Environmental Science,1997,18(3):72-76,94-95.
[5]蒋忠.异位污染土壤修复设备关键部件设计分析及送料控制策略的研究[D].上海:华东理工大学,2015.JIANG Zhong.The Design and analysize of key parts and research of the feeding control strategy of the ex-situ soil remediation equipment[D].Shanghai:East China University of Science and Technology,2015.
[6]李玲,唐晓声,李海建.六价铬污染土壤还原稳定修复[J].广东化工,2016,43(3):95-96.LI Ling,TANG Xiao-sheng,LI Hai-jian.Reduction and stabilization remediation of hexavalent chromium contaminated soil[J].Guangdong Chemical Industry,2016,43(3):95-96.
[7]韩超,申向东,薛慧君,等.镉污染土在水泥-粉煤灰-石灰共同作用下固化效果及孔隙特征[J].农业环境科学学报,2017,36(4):686-693.HAN Chao,SHEN Xiang-dong,XUE Hui-jun,et al.Curing effect and pore characteristics of cadmium contaminated soil under the action of cement-fly ash-lime[J].Journal of Agro-Environment Science,2017,36(4):686-693.
[8]姚武,佘安明,杨培强.水泥浆体中可蒸发水的1H核磁共振弛豫特征及状态演变[J].硅酸盐学报,2009,37(10):1602-1606.YAO Wu,SHE An-ming,YANG Pei-qiang.1H-NMR relaxation and state evolvement of evaporable water in cement pastes[J].Journal of the Chinese Ceramic Society,2009,37(10):1602-1606.
[9]Coates G R,Xiao L Z,Prammer M G.NMR logging:Principles and applications[M].Houston:Haliburton Energy Services,1999.
[10]薛慧君,申向东,邹春霞,等.水泥土早期力学性能影响因素分析[J].硅酸盐通报,2014,33(8):2056-2062.XUE Hui-jun,SHEN Xiang-dong,ZOU Chun-Xia,et al.Analysis of the factors affecting the early mechanical properties of cement soil[J].Bulletin of the Chinese Ceramic Society,2014,33(8):2056-2062.
[11]宋学庆.水泥固化锌离子污染土力学特性试验研究[J].工程勘察,2016,44(6):28-32.SONG Xue-qing,Experimental study on mechanical properties of zinc ion contaminated soils stabilized by cement[J].Geotechnical Investigation&Surveying,2016,44(6):28-32.
[12]UK Environment Agency.Waste acceptance at landfills:Guidance on waste acceptance procedures and criteria[EB/OL].[2017-10-19].https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/296422/geho1110btew-e-e.pdf.
[13]贾尚华,申向东,解国梁.石灰-水泥复合土增强机制研究[J].岩土力学,2011,32(增刊1):382-387.JIA Shang-hua,SHEN Xiang-dong,XIE Guo-liang.Reinforcement mechanism of lime-cement soil[J].Rock and Soil Mechanics,2011,32(Suppl 1):382-387.
[14]李喜林,张佳雯,陈冬琴,等.水泥固化铬污染土强度及浸出试验研究[J].硅酸盐通报,2017,36(3):979-983,990.LI Xi-lin,ZHANG Jia-wen,CHEN Dong-qin,et al.Strength and leaching for remediation of chromium contaminated soil using cement[J].Bulletin of the Chinese Ceramic Society,2017,36(3):979-983,990.
[15]刘玲,刘海卿,张颖,等.石灰和粉煤灰固化修复六价铬污染土试验研究[J].硅酸盐通报,2015,34(11):3361-3365.LIU ling,LIU Hai-qing,ZHANG Ying,et al.Experimental study of lime and fly ash for solidification remediation of hexavalent chromium contaminated soil[J].Bulletin of the Chinese Ceramic Society,2015,34(11):3361-3365.
[16]Li X,Zhang L M.Characterization of dual-structure pore-size distribution of soil[J].Canadian Geotechnical Journal,2009,46(2):129-141.