基于静电和金属络合协同作用的MIL-101(Cr)-NH_(2)高效吸附水中单宁酸

Efficiently Remove Tannic Acid from Aqueous Solution by MIL-101(Cr)-NH_(2) Based on the Synergistic Effect of Electrostatic and Complexation Interaction

通过水热法制备了一种氨基改性的MIL-101(Cr),采用静态吸附法研究了MIL-101(Cr)-NH_(2)对废水中单宁酸的吸附性能。采用X射线衍射仪(XRD)、扫描电镜(SEM)、傅里叶变换红外光谱(FTIR)和氮气吸附法表征了材料的结构和形貌,研究了pH值、吸附时间、初始浓度及离子强度对其单宁酸吸附性能的影响,探究了其对单宁酸的吸附机理。随着溶液pH增大,MIL-101(Cr)-NH_(2)对单宁酸的吸附量逐渐升高,最佳pH为7.0。MIL-101(Cr)-NH_(2)对单宁酸的吸附过程符合拟二级动力学模型、Freundlich模型和Temkin模型,说明吸附过程为多层化学吸附。扩散模型拟合结果表明,膜扩散和粒子内扩散同时控制吸附过程。在T=303 K、pH=7时,MIL-101(Cr)-NH_(2)饱和吸附量高达2031 mg/g。通过Zeta电位和FTIR等表征分析发现,单宁酸主要靠静电作用和金属络合作用被吸附在MIL-101(Cr)-NH_(2)上。

An amino-functionalized MIL-101(Cr)(namely MIL-101(Cr)-NH_(2))was prepared by hydrothermal method and its adsorption performance of tannic acid in aqueous solution was investigated by batch experiments.The structure and morphology of MIL-101(Cr)-NH_(2)were characterized through powder X-ray diffraction instrument(XRD),scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FTIR)and nitrogen adsorption-desorption isotherms.The effects of initial pH,adsorption time,initial concentration and ion strength on the adsorption performance of tannic acid were explored and the adsorption mechanism was studied.The adsorption capacity of tannic acid onto MIL-101(Cr)-NH_(2)gradually increased with the increasing pH value and the optimal pH value was 7.0.The pseudo-second-order kinetic model,Freundlich model,and Temkin model fitted the adsorption data well,which indicated that tannic acid was adsorbed onto MIL-101(Cr)-NH_(2)by multilayer adsorption and the adsorption process was dominated by chemisorption.The fitting results of diffusion models suggested that film diffusion and intra-particle diffusion affected the adsorption process together.At T=303 K and pH=7,the equilibrium adsorption capacity of MIL-101(Cr)-NH_(2)was up to 2031 mg/g.The main mechanism controlling the adsorption of tannic acid onto MIL-101(Cr)-NH_(2)are the electrostatic interaction and Cr-O complexation interaction.