超重力法制备CNT负载MnFe_(2)O_(4)纳米材料及吸附Pb(Ⅱ)应用

Preparation of CNT supported Mn Fe_(2)O_(4) nanomaterial based on highgravity technology and its application for the adsorption of Pb(Ⅱ)

为改善MnFe_(2)O_(4)纳米颗粒在实际应用中的团聚问题,结合多壁碳纳米管(CNT)原位负载,提出超重力法制备CNT负载MnFe_(2)O_(4)纳米材料(MnFe_(2)O_(4)/CNT)。以典型的重金属污染Pb(Ⅱ)作为研究对象,对其吸附性能进行研究。首先考察了MnFe_(2)O_(4)负载量对Pb(Ⅱ)吸附容量的影响,确定最佳MnFe_(2)O_(4)负载量为83.3wt%。采用XRD,SEM,N 2吸附-脱附比表面分析仪和VSM对最佳MnFe_(2)O_(4)负载量条件下的MnFe_(2)O_(4)/CNT进行表征。MnFe_(2)O_(4)/CNT展现出优异的磁性,其饱和磁化强度为35.85 emu/g,因而可应用于水体中污染物的磁性分离。吸附实验结果表明在初始Pb(Ⅱ)浓度300 mg/L和溶液pH=6的条件下,Pb(Ⅱ)在MnFe_(2)O_(4)/CNT上180 min达到吸附平衡,吸附平衡容量为80.7 mg/g,远高于单独的CNT(28.4 mg/g)。动力学研究表明Pb(Ⅱ)在MnFe_(2)O_(4)/CNT上的吸附符合Elvoch动力学模型,说明吸附机理中存在化学吸附。Freundlich等温线模型能够很好地描述Pb(Ⅱ)在MnFe_(2)O_(4)/CNT上的吸附过程,其代表发生在非均匀表面的多分子层吸附。另外,吸附等温线实验中获得的MnFe_(2)O_(4)/CNT最大吸附容量为106.2 mg/g,展现出了对重金属Pb(Ⅱ)优异的吸附性能,在去除溶液中重金属中具有较大的应用潜力。根据X射线光电子能谱分析,表明吸附机理涉及到Pb(Ⅱ)与MnFe_(2)O_(4)表面羟基的络合。

In order to overcome the agglomeration problem of MnFe_(2)O_(4) nanoparticles in practical applications,the high-gravity technology combining with the in-situ support of multiwalled carbon nanotubes(CNT)is proposed to prepare the CNT supported MnFe_(2)O_(4) nano-material(MnFe_(2)O_(4)/CNT).The typical heavy metal pollution Pb(Ⅱ)is selected as the research object to study the adsorption performance of MnFe_(2)O_(4)/CNT.First,the effects of different MnFe_(2)O_(4) loads on the adsorption capacity toward Pb(Ⅱ)are investigated,and the optimal MnFe_(2)O_(4) load is determined to be 83.3wt%.The obtained MnFe_(2)O_(4)/CNT in the optimal MnFe_(2)O_(4) load is charactered by XRD,SEM,N_(2) adsorption-desorption specific surface analyzer and VSM,and which exhibits an excellent magnetic property with a high saturation magnetization of 35.85 emu/g.Thus,the obtained MnFe_(2)O_(4)/CNT can be applied for the magnetic separation of pollutants in water.The results of adsorption experiments show that under the conditions of initial Pb(Ⅱ)300 mg/L and solution pH=6,the adsorption of Pb(Ⅱ)on MnFe_(2)O_(4)/CNT in solution reached equilibrium after 180 min,and the adsorption equilibrium capacity is 80.7 mg/g,which is much higher than pure CNT(28.4 mg/g).The kinetic study demonstrates that the adsorption behavior of Pb(Ⅱ)on MnFe_(2)O_(4)/CNT is most consistent with the Elvoch kinetic model,which suggests there exists a chemical adsorption in the adsorption mechanisms.Freundlich isotherm model describes well the adsorption process of Pb(Ⅱ)on MnFe_(2)O_(4)/CNT,which represents a multilayer adsorption process on heterogeneous surfaces.In addition,the maximum adsorption capacity of MnFe_(2)O_(4)/CNT obtained from adsorption isotherm experiment is 106.2 mg/g,which displays excellent adsorption performance for Pb(Ⅱ)and has a great potential in heavy metals removal in solution.According to the X-ray photoelectron spectroscopy analysis,it can be concluded that the adsorption mechanisms involve the complexation between Pb(II)and the hydroxyl groups on the surface of MnFe_(2)O_(4).