ZnFe_2O_4/多壁碳纳米管制备及其对水中盐酸四环素的吸附性能

Preparation of ZnFe_2O_4/multi-walled carbon nanotube magnetic composites and the adsorption of tetracycline hydrochloride in the aqoeous solution

以碳纳米管、硝酸铁和硝酸锌为材料,通过化学沉积方法制备磁性功能化的碳纳米管。将铁氧体纳米粒子负载到多壁碳纳米管的表面,得到ZnFe2O4/CNTs磁性复合材料,通过SEM、TEM、XRD、VSM进行表征。该材料在室温下为超顺磁性,饱和磁化强度为16.104A.m2/kg,在酸性溶液(pH值为2)中,Fe3+的最大渗出量为10.56mg/g。用所制备的ZnFe2O4/CNTs复合材料对盐酸四环素溶液进行吸附试验。结果表明,该材料在一定范围内吸附容量随污染物质量浓度增加而增大,随温度升高而减小。在25℃、盐酸四环素初始质量浓度为20mg/L时,ZnFe2O4/CNTs复合材料的吸附容量为21.8 mg/g,污染物去除率达到54.5%。

This paper is inclined to report our experimental research results in preparing the magnetic functional carbon nanotubes with the chemical sediment method by using carbon nanotubes,iron nitrate and zinc nitrate.We have first of all prepared the ferrite nanoparticles adhering to the surface of multi-walled carbon nanotube,magnetic nano composite materials of ZnFe2O4/CNTs,and then separated the magnetic materials quickly from an external magnetic field.The ZnFe2O4/CNTs magnetic composites we have prepared were characteristically analyzed by scanning electronic microscopy（SEM）,transmission electronic microscopy（TEM）,X-ray diffractometry（XRD） and vibrating sample magnetometry（VSM）.When the composite samples were scanned through the SEM and TEM,it was found that a lot of nano-particles would have been loaded on the surface of purified CNTs,and then new composites were to be formed in a typical hollow-layered structure.The XRD pictures prove that,with some new diffraction peaks appearing,the crystal type and the structure of the new composites have changed.The diffraction peaks corresponding to the structures（220）,（311）,（400）,（511）,（440） and（533） suggest that the nano-particles ZnFe2O4 were acting as the magnetic phase in MWCNTs,which can be seen from the VSM picture ZnFe2O4/CNTs with a saturation magnetization（Ms） being 16.104 A·m2/kg.It exhibited the superparamagnetic characteristic features without coercive force and residual magnetism,indicating that the bulk ZnFe2O4 is ferromagnetic in room temperature.However,the magnetic composites of ZnFe2O4/CNTs were superparamagnetic due to the smaller size of nanoparticles of ZnFe2O4.They were remaining stable in the neutral and alkaline solutions.However,it was possible for the Fe3＋ leakage of ZnFe2O4/CNTs composites to be detected by the method of flame atomic absorption spectrophotometry.On the condition of the solution with the pH value of 2,the Fe3＋ leakage of ZnFe2O4/CNTs composites equals 10.56 mg/g.Under the given condition,it was possible to use the composites to adsorb the tetracycline hydrochloride in aqueous solution.Hence,the results of our experiments show that the adsorption capacity proves bigger at the lower temperatures and higher concentrations of pollutants.When the initial concentration is 20 mg/L,at the temperature of 25 ℃,the adsorption capacity is 21.8 mg/g,with a pollutant removing rate of 54.5%.