高容量咪唑型螯合树脂的制备及其对Cd(Ⅱ)和Zn(Ⅱ)的吸附性能

Preparation of High-capacity Imidazole Type Chelating Resin and Its Adsorption Properties to Cd( Ⅱ) and Zn( Ⅱ)

以氯甲基化交联聚苯乙烯树脂(CMCPS)为载体和大分子引发剂,1-乙烯基咪唑(VIM)为单体,溴化亚铜/2,2'-联吡啶为催化剂体系,采用表面引发原子转移自由基聚合技术(SI-ATRP),将1-乙烯基咪唑接枝到CMCPS树脂表面,制得新型咪唑型螯合树脂(VIM-CMCPS),并采用X射线光电子能谱、元素分析和扫描电镜对其进行表征。考察了该螯合树脂对Cd2+和Zn2+的吸附性能、动力学和热力学参数。该螯合树脂表面VIM接枝密度达1.008 mg/m2。结果表明,该树脂对Cd2+和Zn2+的吸附量随溶液初始浓度和温度的升高而增加,当p H值分别为3.6和2.4时,对Cd2+和Zn2+的吸附效果最佳,树脂的静态饱和吸附容量分别为653.1 mg/g和793.3 mg/g,Langmuir和Freundlich方程均呈现良好的拟合度。热力学平衡方程计算得ΔG<0,ΔH=24.47 k J/mol,ΔS>0,表明该吸附过程是自发、吸热、熵增加的过程。动力学研究表明,该过程符合准二级动力学模型。

A new high-capacity imidazole type chelating resin was synthesized via surface-initiated atom transfer radical polymerization（ SI- ATRP） method. 1-Vinylimidazole（ VIM） was grafted onto the surface of the chloromethyl polystyrene resin by SI- ATRP using organic metal compound formed in the Cu Br /2,2＇-bipyridine（ Bpy） system as catalyst at room temperature. The chelating resin was characterized by means of isoelectronic X ray spectrum,elementary analysis and electron microscopy,and its adsorption properties,parameters of kinetics and thermodynamics were determined. The amount of VIM on the surface of polystyrene resin was calculated to be 1. 008 mg / m2. Adsorption capacity for cadmium（ Ⅱ） and zinc（ Ⅱ） increased with increasing initial metal ion concentration and temperature,and its highest values were 653. 1 mg / g for cadmium（ Ⅱ） at p H 3. 6 and 793. 3 mg / g for zinc（ Ⅱ） at p H 2. 4. The experimental results showed that the equilibrium adsorption data fitted well to both Langmuir and Freundlich isotherms. The thermodynamic equilibrium functions were also determined as follows： ΔG 0,ΔH = 24. 47 k J / mol,ΔS 0,so the adsorption was spontaneous,endothermic and entropy increasing. The kinetic experimental data were correlated with second-order kinetic model.