Stabilizing effect of different stabilizers on waste slag polluted by zinc and cadmium
YU Bingbing1,2,3,, YAN Xianghua2,3,,, WANG Xingrun2,3, LI Lei2,3, ZHANG Yuxiu1 1.School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China 2.National Engineering Laboratory of Safety Remediation Technology for Polluted Sites, Beijing 100101, China 3.State Key Laboratory for Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Abstract:The heavy metal concentrations in waste slag are high and difficult to deal with. In order to solve the problem, typical sulfides, phosphates, CaO, MgO and composite reagents were used to stabilize the highly acidic waste slag polluted by zinc and cadmium. The stabilization effect was evaluated by the water extraction method (HJ 557-2010). The maximum allowable discharge concentration in the standard GB 8978-1996 was taken as the standard requirement. Waste slag can be disposed safely after stabilization. The results demonstrate that among the addition of single reagent such as phosphate and sulphide at the same molar ratio, Na3PO4·12H2O showed the best stabilization effect on Zn and Cd, Na2S·9H2O showed the best stabilization effect on As, and the comprehensive stabilizing effect (η) when Zn, Cd, As and Cu elements simultaneously met the standard followed the order: Na2S·9H2O(η=96.36%)>(NH4)2HPO4(η=87.42%)>Na3PO4·12H2O(η=82.26%). The comprehensive stabilizing effect (η) of single MgO, CaO and composite reagents followed the order: 0.4% MgO>0.4% CaO>(0.4% CaO+0.61% Na2S·9H2O)>(0.4% CaO+0.32% (NH4)2HPO4)>1.2% (Na2S·9H2O∶(NH4)2HPO4∶Na3PO4·12H2O=2∶1∶3). The combination of MgO, Na3PO4·12H2O and calcium-sulfide was the optimized stabilizer. These results can provide solid data for the treatment of heavy metal contaminated waste slag with high efficiency in China. Key words:slag/ heavy metal/ stabilizer/ leaching toxicity/ stabilization efficiency.
图1Na2S·9H2O对废渣中Zn、Cd、Cu和As水浸出浓度的影响 Figure1.Effect of Na2S·9H2O on the H2O leaching concentration of Zn, Cd, Cu and As in waste slag
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1.School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China 2.National Engineering Laboratory of Safety Remediation Technology for Polluted Sites, Beijing 100101, China 3.State Key Laboratory for Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China Received Date: 2019-07-30 Accepted Date: 2019-09-19 Available Online: 2019-12-28 Keywords:slag/ heavy metal/ stabilizer/ leaching toxicity/ stabilization efficiency Abstract:The heavy metal concentrations in waste slag are high and difficult to deal with. In order to solve the problem, typical sulfides, phosphates, CaO, MgO and composite reagents were used to stabilize the highly acidic waste slag polluted by zinc and cadmium. The stabilization effect was evaluated by the water extraction method (HJ 557-2010). The maximum allowable discharge concentration in the standard GB 8978-1996 was taken as the standard requirement. Waste slag can be disposed safely after stabilization. The results demonstrate that among the addition of single reagent such as phosphate and sulphide at the same molar ratio, Na3PO4·12H2O showed the best stabilization effect on Zn and Cd, Na2S·9H2O showed the best stabilization effect on As, and the comprehensive stabilizing effect (η) when Zn, Cd, As and Cu elements simultaneously met the standard followed the order: Na2S·9H2O(η=96.36%)>(NH4)2HPO4(η=87.42%)>Na3PO4·12H2O(η=82.26%). The comprehensive stabilizing effect (η) of single MgO, CaO and composite reagents followed the order: 0.4% MgO>0.4% CaO>(0.4% CaO+0.61% Na2S·9H2O)>(0.4% CaO+0.32% (NH4)2HPO4)>1.2% (Na2S·9H2O∶(NH4)2HPO4∶Na3PO4·12H2O=2∶1∶3). The combination of MgO, Na3PO4·12H2O and calcium-sulfide was the optimized stabilizer. These results can provide solid data for the treatment of heavy metal contaminated waste slag with high efficiency in China.
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--> --> --> 我国铅锌工业总规模大，常年位于世界第一，仅2018年，精Zn产量达5.68×106 t，约占全球总量的40%，我国Zn冶炼主流工艺为“焙烧—浸出—电积”，其生产过程中产生大量含Zn、Cd和As等的冶炼废渣，统计表明，平均生产1 t Zn，产生0.96 t废渣[1]，废渣历史积存量和年新增量大，难以得到有效的消纳利用，通常采用无害化填埋、堆置储存等方式进行处置。在长期的堆置过程中，受风蚀、淋溶和浸蚀等作用影响，废渣中的重金属释放，对周边人群健康和土壤、地下水等生态环境造成严重威胁[2]。 稳定化是废渣常见的无害化处理方式，通过加入稳定剂降低重金属的迁移性，而稳定剂的选择是关键。目前，常用稳定剂一般包括有机、无机和生物质型3种[3]。其中，无机型药剂因对重金属稳定效果好而广被应用[4-6]，其对重金属主要是通过化学键合、物理包容、吸附或形成惰性沉淀物等作用进行稳定[7-8]。目前，研究应用多以含硫、磷、铁、钙、镁等药剂为主[7-11]，但多集中在Zn、Pb等个别污染指标，而针对废渣中As、Cd等其他多污染物共存的系统化研究还较为欠缺，特别是个别稳定剂对废渣中As反而存在活化作用则较少关注，受介质类型、污染程度、稳定剂种类、投加量、配伍等因素的影响，不同药剂实际稳定化效果还须进行综合比对和考证。 本研究以湖南某大型冶炼企业渣场堆存的铅锌冶炼废渣为研究对象，采用Na2S·9H2O、(NH4)2HPO4、Na3PO4·12H2O、CaO、MgO为稳定化药剂，并进行了药剂配伍研究，以水浸提法[12]模拟废渣堆存过程的浸蚀淋溶影响，考察了不同药剂对Zn、Cd、Cu、As的综合稳定化效果及其对环境的影响，以期为国内铅锌冶炼废渣的无害化处置提供参考。
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