摘要
利用水稻秸秆与凹凸棒石在缺氧条件下热解制备稻秆生物炭/凹凸棒石复合材料(BA),并通过氢氧化钠改性提升其吸附性能.通过吸附动力学、等温吸附及改变初始pH等吸附试验研究复合材料在Cd、Pb 一元及二元污染体系中的吸附行为,并结合扫描电镜能谱(SEM-EDS)、比表面积及孔径分析(BET)、傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)及X射线光电子能谱分析(XPS)等表征手段深入分析改性后复合材料对溶液中重金属Cd、Pb的吸附机理.试验结果表明氢氧化钠改性复合材料(NBA)对Cd2+和Pb2+的吸附容量分别为117.05和274.65 mg·g-1,其去除效率比BA分别增加31.2％和51.7％.在二元金属体系中NBA吸附能力也明显优于BA,准二级动力学模型和Langmuir等温模型能更好地用于模拟吸附结果,表明该吸附主要为单分子化学吸附过程.此外,竞争吸附分析表明在Cd、Pb共存溶液中,与Cd2+相比,Pb2+更易被复合材料吸附.通过SEM-EDS、FTIR、XRD和XPS等表征方法确定了 NBA对Cd2+和Pb2+的吸附机制,主要包括其与表面含氧官能团的络合作用、与矿物质的沉淀作用及π-电子作用.综上,改性复合材料NBA在实际废水处理中是一种极具潜力的吸附剂.
Abstract
A novel rice straw biochar/attapulgite composite(BA)was prepared by pyrolysis under anoxic conditions with rice straw and attapulgite,which was modified with sodium hydroxide to improve its adsorption performance.Batch adsorp-tion experiments,including adsorption kinetics,isothermal adsorption and change of initial pH,were conducted to investi-gate the adsorption behavior of composite materials in single and binary pollution systems of Cd and Pb.SEM-EDS,BET,FTIR,XRD,and XPS were used to analyze the adsorption mechanisms of modified composites of Cd and Pb.The results show that the adsorption capacity of sodium hydroxide modified composite(NBA)for Cd2+and Pb2+was 117.05 and 274.65 mg·g-1,respectively,and the removal efficiency of NBA was increased by 31.2％and 51.7％,respectively,compared with BA.In the binary metal system,the adsorption capacity of NBA was also significantly better than that of BA.The pseudo-second-order kinetics model and the Langmuir isotherm model could describe the Cd2+and Pb2+adsorption processes of the composites better,which proves that the adsorption is mainly a single molecule chemical adsorption process.In addition,competitive adsorption analysis showed that Pb2+was more easily adsorbed by composite materials than Cd2+in coexisting solutions.The characterization method determined the adsorption mechanism of NBA for Cd2+and Pb2+,mainly including the complexation with surface functional groups,precipitation with minerals and π-electron interac-tion.In conclusion,NBA is a highly potential adsorption material for the treatment of heavy metal pollution in wastewater.
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