阳(阴)离子复配修饰两性磁性膨润土的表面特征差异及对苯酚吸附的影响

Comparison of Amphoteric-Cationic and Amphoteric-Anionic Modified Magnetic Bentonites: Characterization and Sorption Capacity of Phenol

以膨润土(BT)为基质,采用共沉淀法制备负载Fe3O4的磁性膨润土(MBT),在两性表面活性剂十二烷基二甲基甜菜碱(BS-12)修饰(BS-MBT)的基础上,以阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)/阴离子表面活性剂十二烷基磺酸钠(SDS)为复配修饰剂,通过湿法分别制备2种两性复配修饰磁性膨润土(BS-CT-MBT/BS-SDS-MBT),采用扫描电镜、X-射线衍射、热重、红外光谱对样品进行表征,测定磁性、比表面积和孔容等性质,通过批处理实验法对比两性复配修饰磁性膨润土对苯酚的吸附.结果表明,两性复配修饰膨润土具有良好的磁分离性能.与BS-MBT相比,BS-CT-MBT的C、N质量分数增大,复配修饰剂质量分数增加,孔容和比表面积减小,BS-SDS-MBT的C、N质量分数减小,复配修饰剂质量分数减少,孔容减小,比表面积增大.在pH 6.0的0.1 mol·L^(-1)Na Cl溶液中各修饰剂的解吸率低于9%.各土样对苯酚的等温吸附数据符合Henry模型,以分配吸附为主,吸附量顺序为BS-CT-MBT>BS-MBT>BS-SDS-MBT>BT>MBT,修饰剂质量分数是影响苯酚吸附的决定性因素,CTMAB提升土样吸附苯酚能力的效果高于SDS.

Magnetic bentonite is modified by an amphoteric surfactant（dodecyl dimethyl betaine,BS-12）,then modified by a cationic surfactant（Cetyl Trimethyl Ammonium Bromide,CTMAB） and anionic surfactant（Sodium lauryl sulfonate,SDS）.Amphotericcationic modified magnetic bentonite（BS-CT-MBT） and amphoteric-anionic modified magnetic bentonite（BS-SDS-MBT） are obtained.Structural identification of the samples were characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,thermogravimetric analyses（TG）,Fourier transform infrared spectra（FTIR）,and vibrating sample magnetometer（VSM）.The carbon-nitrogen content,specific surface area,and pore volume were also evaluated.Batch isotherm studies were conducted to evaluate the sorption of phenol.The results show that BS-CT-MBT and BS-SDS-MBT can be separated by magnetic separation.The carbon content-nitrogen content and content of surfactants of the BS-CT-MBT increase,while surface area and pore volume decrease compared to those of BS-MBT.Compared with BS-MBT,the carbon-nitrogen content,content of surfactants,and pore volume of BSSDS-MBT are decreasing and surface area is increasing.The desorption rate of the surfactants is less than 9% at pH 6.0 and in 0.1 mol·L^-1 Na Cl solution.The Henry equation is the optimal description for the phenol sorption isotherms,implying a partitioning sorption process.The amount of phenol sorption follows the order：BS-CT-MBT〉BS-MBT〉BS-SDS-MBT〉BT〉MBT,which significantly correlates with the variation of the content of surfactant.Amphoteric magnetic bentonites modified by CTMAB have better absorption performance for phenol than those modified by SDS.