采用热合成法制备磁性埃洛石作为吸附剂,吸附水溶液中四环素类抗生素,研究了温度、浓度、pH、起始浓度的影响,并且分析了热力学与动力学的研究

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Synthesis of Magnetic Halloysite Composites forthe Effective Removal ofTetracycline Hydrochloride from Aqueous Solutions

Weisheng Guan1, Xu Wang1,*, Jianming Pan2, Junru Lei1, Ya Zhou1, Chenchen Lu1andYongsheng Yan2(1) School of Environmental Science and Engineering, Chang’an University, Xi ‘an 710054, P. R.China. (2) School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, P. R. China.(Received 10 June 2012; revised form accepted 11 September 2012)

ABSTRACT:Herein, we explain an effective method for the synthesis of

halloysite/CoFe2O4magnetic composites (magnetic halloysite nanotubes or

MHNTs) and their use as as adsorbents to effectively remove tetracycline

hydrochloride (TC–HCl) from aqueous solutions. The synthesized composites

were characterized by the following methods: Fourier transform infrared, X-ray

diffraction, transmission electron microscopy, vibrating sample magnetometry

and atomic absorption spectrometry. Our study results indicated that MHNTs

have strong magnetic (Ms =34.02 emu/g) and low leakage properties. The

adsorption capacities of MHNTs were investigated by performing a series of

experiments with different pH, temperatures, initial concentrations and reaction

time. The Langmuir isotherm model fitted to equilibrium data better than the

Freundlich model. The kinetic properties of the composites were well-described

by applying the pseudo-second-order equation. Even after carrying out two

repeated experimental cycles, the reusability of the synthesized composites did

not obviously degenerate.

1. INTRODUCTION

Controlling water quality is one of the most critical issues that immediately needs to be addressed inorder to protect the environment. Because tetracycline (TC) antibiotics inhibit the activity of a varietyof microorganisms, they are widely used as broad-spectrum antibiotics in human beings and animals,and also as pesticides in agriculture (Farrington et al. 1991; Liu et al. 2012). Consequently, there hasbeen a widespread use of TCs, which has had a negative impact on the environment. Some of theirhazardous effects owing to their extensive use include causing serious problems to non-targetorganisms, increasing the resistance to antibiotics in microorganisms, and causing harmful side effectsto humans (Jia et al. 2008; Navarro et al. 2009; Ji et al.2011). Therefore, the removal of TCs fromthe aquatic environment is necessary and vital. At present, there are several ways to remove TCs inwastewater, including solvent extraction, supercritical fluid extraction, microwave-assisted extraction,membrane separation technology and solid-phase extraction techniques (Chen and Wang 1996;Rissato et al. 2004; Sanusi et al. 2004; Sharif et al. 2006; García-Rodríguez et al. 2010). Comparedwith these methods, adsorption has several advantages, such as reduced cost, less secondary pollution,easy application, recycling the adsorbents used, and finally, it is a relatively effective method, andtherefore, the method is widely used to treat wastewaters. Activated carbon is the conventionaladsorbent for the adsorption process in wastewater treatment because it has an amazing surface areaand a high affinity towards numerous organic chemicals. However, owing to its high cost, it is*Author to whom all correspondence should be addressed. E-mail: wangxu076@yahoo.cn.