向日葵秸秆对U(VI)和Pb(Ⅱ)的选择吸附性能及机理研究  

Extended Study of Sunflower Straw in the Selective Adsorption Behaviors and Mechanisms for U( VI) and Pb( Ⅱ)

作　　者：艾莲[1,2] 罗学刚[1,2] 林晓艳[1,2] 梅强[1] 

机构地区：[1]西南科技大学材料科学与工程学院,四川绵阳621010 [2]西南科技大学生物质材料教育部工程研究中心,四川绵阳621010

出　　处：《林产化学与工业》2014年第2期9-16,共8页Chemistry and Industry of Forest Products

基　　金：国防基础科研重点项目(B3120110001);西南科技大学2013年研究生创新基金项目资助(13ycjj04)

摘　　要：以含有单一的U(VI)、Pb(Ⅱ)溶液以及U(VI)和Pb(Ⅱ)混合溶液为吸附质,系统探讨了pH值、吸附剂量、吸附时间和初始离子浓度对向日葵秸秆吸附效果的影响。采用准一级动力学方程、准二级动力学方程、粒内扩散模型、Langmuir和Freundlich等温吸附方程对实验数据进行拟合,从分配系数和分离因子角度对吸附选择性进行分析,并对吸附机理进行探讨。结果表明:吸附20 mg/L的U(VI)-Pb(Ⅱ)溶液的最佳pH值为4.0、吸附剂量为2.0 g/L、吸附时间为720 min,U(VI)和Pb(Ⅱ)的去除率分别为77.55%、87.44%;U(VI)和Pb(Ⅱ)的吸附动力学在单离子和复配体系下均符合准二级动力学模型;吸附等温线均符合Langmuir等温吸附模型,单离子最大吸附量分别为327.0和67.59 mg/g,且当U(VI)高于200 mg/L时Pb(Ⅱ)的吸附过程也能用Freundlich模型描述。当离子初始浓度较低时向日葵秸秆对Pb(Ⅱ)具有更高的吸附选择性,而较高时则相反。向日葵秸秆吸附前后的SEM、EDX和FT-IR图谱表明,吸附U(VI)和Pb(Ⅱ)的主要方式为络合和离子交换。The adsorptive properties of sunflower straw for U （ Ⅵ） and Pb （ Ⅱ） were systematically evaluated in single and binary solutions using batch experiments as a function of solution pH, adsorbent dosage, contact time and initial ion concentration. The kinetic data were analyzed by the pseudo-first-order, pseudo-second-order kinetic and intraparticle diffusion models. The equilibrium sorption data were examined using the Langmuir and Freundlich isotherm equations. It was shown that that a dose of 2.0 g/L of sunflower straw in an initial ions concentration of 20 mg/L with an initial pH of 4. 0 and a contact time of 720 min resulted in the maximum U （Ⅵ） and Pb （Ⅱ） removal efficiency （about 77. 55 % and 87. 44 %, respectively） in U （Ⅵ）/Pb （ Ⅱ） binary system. The kinetic and isotherm experimental data were fitted to the pseudo-second-order rate equation and the Langmuir isotherm model with much satisfaction for single and binary metal systems, respectively. The sorption data of Pb （ Ⅱ） also conformed successfully to the Freundlich equation at U （ Ⅵ） concentration more than 200 mg/L. The maximum adsorption capacity in single system for U （Ⅵ） and Pb （Ⅱ） was calculated to be 327. 0 and 67. 59 mg/g, respectively. The sunflower straw displayed an excellent selectivity in the adsorption of Pb （ Ⅱ） over U （ Ⅵ） in the binary system at lower initial concentrations of ions and the case was vice versa at higher concentrations. Furthermore, SEM, EDX and FT-IR analyses revealed that U （ Ⅵ） and Pb （ Ⅱ） adsorption onto sunflower straw could be predominantly controlled by the ion exchange as well as complexation mechanism.

关 键 词：向日葵秸秆 选择性 U(Ⅵ) Pb(Ⅱ) 吸附机理 

分 类 号：TQ35[化学工程] X591[环境科学与工程—环境工程]