Fly ash used for the remediation of heavy metals from acid coal waste leachate was studied through batch adsorption experiment and column leaching experiment. The results show that Freundlich model is suitable for the adsorption isotherms of Pb2+, Cu2+, Cd2+ and Zn2+ on fly ash. Adsorption kinetics show that heavy metals removal efficiency reachs equilibrium after 30 rain adsorption for initial concentration of 1.8 mmoL/L. Pseudo-second-order kinetic model is found to characterize the adsorption kinetics well. The adsorption capacity increases with pH increase, and the adsorption equilibrium for Pb2+, Cu2+, Cd2+ and Zn2+ reached at 3.5,6.0,7.5 and 8.0 respectively. Co-existing heavy metal ions have great impact on the specific heavy metal adsorption on fly ash, and the adsorption capacity followes the order of Pb＞Cu＞Cd＞Zn. During the column experiment,the coal waste leachate in the control column have the typical characteristics of aicd mine drainage, with low pH, high concentration of heavy metals;while the column fill with coal waste and fly ash drained leachates characterized by little alkaline pH,low iron and other metals concentration. The results show fly ash used in this study have potentials to treat heavy metals pollution from coal waste leachate.%采用批处理吸附实验和柱状淋溶模拟实验,分析粉煤灰吸附重金属、处理煤矸石酸性重金属淋滤液的效果及机理.结果表明:①粉煤灰对Pb2+、Cu2+、Cd2+和Zn2+的吸附等温线符合Freundlich等温模式,吸附过程符合准二级反应动力学模型,且均在30 min内达到吸附平衡,随着pH增加,4种重金属离子吸附率逐渐增加并趋于平衡(Pb、Cu、Cd、Zn分别在pH=3.5、6.0、7.5、8.0时达到平衡),在酸性环境下粉煤灰对4种金属离子具有较好的吸附性能;②在重金属竞争性吸附中,共存离子的存在抑制了目标离子的吸附,其中Pb受共存离子的影响最小,粉煤灰吸附强弱顺序为Pb＞Cu＞Cd＞Zn;③煤矸石柱状淋溶试验中,煤矸石淋滤液呈现较强酸性、较高重金属浓度的酸性矿山废水特征,而在粉煤灰处理中,淋滤液的pH值呈中性,重金属离子浓度显著下降,其主要机制为粉煤灰吸附、碱性中和、重金属与Fe共沉淀等.研究表明,实验用粉煤灰具有修复煤矸石酸性重金属淋滤液的潜力.
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