改性纳米Fe_3O_4去除水溶液中四环素的研究

Adsorbing power of modified nano-Fe_3O_4 in removing tetracycline from the aqueous antibiotic pollutants

利用共沉淀法制备了表面活性剂PVP-K30以及PEG-4000改性纳米Fe3O4吸附剂,采用X射线衍射仪(XRD)、透射电子显微镜(TEM)、震动样品磁强计(VSM)表征了改性Fe3O4的形貌、尺寸以及磁性质;以盐酸四环素(TC)为吸附对象,研究了改性剂、反应温度和TC起始质量浓度等对Fe3O4吸附性能的影响,同时利用红外光谱仪(IR)研究吸附机理。结果表明,改性后纳米Fe3O4结晶度及分散性明显提高,较25 nm的未改性Fe3O4,PVP和PEG-4000改性Fe3O4颗粒分别减小至20 nm和10 nm;同时改性产物均保持了较高磁性性能。在吸附盐酸四环素(TC)过程中,PEG-4000改性Fe3O4吸附容量最高(47.62mg/kg),PVP改性Fe3O4的吸附能力(36.1 mg/kg)优于未改性Fe3O4(13.45 mg/kg)。PEG-4000改性Fe3O4吸附TC过程中,Langmuir等温线模型优于Freundlich等温线模型,表明吸附剂对四环素分子为单层分子吸附,其吸附动力学遵循孔内扩散模型,并以表面吸附为主,粒内扩散为辅;改性Fe3O4吸附TC行为中羟基间形成的氢键起主要吸附作用。改性Fe3O4吸附剂经3次解吸仍显示出较高的吸附容量。

In this paper, we have prepared surfactants PVP - K30 and PEG- 4000 modified nano-Fe3O4 via coprecipitation method and attempted to characterize the modified products by means of X-ray diffraction （XRD）, transmission electron microscopy （TEM） and vi- brating sample magnetometer （VSM）. The results of our experiments indicate that after being modified, the crystalline and dispersion of nano-Fe3O4 can greatly increase their size of PVP, with their PEG - 4000 increased to 20 nm and 10 nm, respectively, in comparison with their unmodified counterpart with a size of 25 nm. In addition, the modified nanoparticles can maintain their high magnetic perfor- mance. When we attempted to employ the modified products in our experiments to test their ability to adsorb the tetracycline （TC） from aqueous solutions through bio-adsorption, we conducted the batch mode experiments in terms of testing the modifying agents, tempera- tures and initial concentration of TC so as to make clear the adsorptive behaviors of the products. The experimental results have shown that without modification, the adsorption capacity of pure Fe3O4 was only about 13.45 %, whereas adding the modifying agent PVP surfactant cangready improve the adsorption capacity by 36.1%, and PEG - 4000 modified Fe304 increase its absorptive capacity by 47.62%. In addition, the adsorption process of PEG- 4000 of the modified Fe304 on TC has improved, with their Langmuir isotherm model made better fited for the equilibrium data than the did Freundlich model. This ab- sorption isotherm results of PEG - 4000 modified Fe3O4 demonstrate that the TC is the monomolecular adsorbent onto the surface of the Fe304. The kinetic properties of the modified Fe3O4 can well be de- scribed by the intraparticular diffusion model, dominated by the sur- face adsorption and intra-particular diffusion acted as a kind of auxil- iary adsorption. What is more, the analysis based on IR has given us a clue to the adsorption behavior of PEG - 4000 modified Fe3O4, which indicates that hydrogen-bond-formation is supposed to plays a leading role in removing TC from the aqueous solution. Finally, our research has also disclosed the fact that the resulting modified Fe3O4 enjoys a great reusability without noticeable deterioration in their own performance at least to three repeated recyles.