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近几十年抗生素的滥用已造成了地表水和饮用水的污染[1-2].作为一种广谱抗菌剂—四环素(TC)在动物体内代谢不完全,其中60%—90%的母体化合物以原始或代谢形式排放到水生环境中,因其具有很好的化学稳定性,几乎不会自然分解[3].常规处理四环素的方法包括电解法[4]、光催化降解[5]、化学氧化[6]和生物过滤[7]这些方法因其流程复杂基础设施昂贵和可能二次污染而受到限制.因此开发一种高效、便捷和"绿色"去除TC的技术已成为一项重要而紧急的任务.
石墨烯是一种基于二维蜂窝状结构的纳米材料[8]。其比表面积理论值高达2630 m2·g−1,这为去除抗生素提供更多的吸附位点[9]。氧化石墨烯因其富含含氧官能团而具有优异的性能。活性较强的含氧官能团可与抗生素产生强相互作用,并具有很高的可修饰性[10−11]。早期人们侧重于石墨烯或氧化石墨烯吸附抗生素,但是由于石墨烯片层间的静电力使其具有疏水性以及石墨烯片层之间容易发生堆叠,这不利于抗生素的吸附[12−13]。因此,二维结构的石墨烯在应用中存在一定的问题。以石墨烯为基本单元的多孔三维石墨烯,可以克服二维石墨烯堆叠缺点,展现出更高的比表面积、较大的孔隙率,从而实现优异的吸附性能[14−15]。而且三维石墨烯作为吸附剂不仅避免了石墨烯吸附剂在水中造成的二次污染,还作为宏观体,更有利于固液分离[16]。
基于三维石墨烯多孔空间结构和超大比表面积,以及良好的吸附性能,采用环境友好的抗坏血酸还原氧化石墨烯,通过自组装形成具有三维网络结构的气凝胶三维石墨烯(3DG)。用扫描电镜(SEM)、透射电镜(TEM)和X射线衍射(XRD)等技术对3DG微观结构和化学组成进行了表征。将3DG作为吸附剂应用于去除水中四环素(TC),系统研究了TC的吸附机理和降解性能。
基于三维石墨烯去除水体中四环素
The removal of tetracycline in water based on 3D grapheme
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摘要: 三维石墨烯具有较大的比表面积和独特的空间孔结构,为捕获抗生素提供大量的活性位点,能够促进抗生素在多孔网络结构的运输。本研究采用化学还原自组装方法制备了有序多孔结构的三维石墨烯(3DG),并将其应用于去除水体中的四环素(TC)。研究结果显示, TC在3DG的吸附过程同时符合伪二级动力学和Langmuir方程。在最佳吸附pH=6时,3DG对TC最大饱和吸附量达到322.58 mg·g−1,并具备良好的再生性能,经过5次吸附-解吸重复试验后, 3DG对水体中TC的去除率仍可达68%。因此,3DG是一种在环境分析领域具有良好应用前景的吸附材料。Abstract: Three-dimensional graphene can provide abundant active sites for trapping the antibiotic and promoting the transportation of antibiotic in the porous network structure based on its large surface area and interconnected porous structure. In this study, porous three-dimensional graphene aerogel (3DG) was prepared by using chemical reduction and self-assembly method, and applied to remove tetracycline (TC) from water. The results revealed that 3DG exhibited good adsorption performance towards TC, with maximum adsorption amount being 322.58 mg·g−1 at pH=6, the adsorption process of TC on 3DG accords with pseudo-second-order kinetics and Langmuir model. 3DG has good regeneration performance. After 5 repeated adsorption-desorption experiments, the removal rate was kept 68%. Thus, 3DG is a promising adsorbent in field of environmental analysis.
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Key words:
- three-dimensional graphene /
- tetracycline /
- removal /
- regeneration
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表 1 3DG−TC的动力学模型参数
Table 1. Dynamic model parameters of 3DG−TC
C0/(mg·L−1) 伪一级动力学 伪二级动力学 K1/min−1 Qe1/(mg·g−1) R2 K2/(g·mg−1·min−1) Qe2/(mg·g−1) R2 50 0.0963 80.3526 0.6686 2.817×10−3 76.9231 0.9999 C0/(mg·L−1) The Weber and Morris Model K1p/
(g·mg−1·min−1/2)K2p/
(g·mg−1·min−1/2)K3p/
(g·mg−1·min−1/2)C1
(R2)C1
(R2)C.3
(R2)50 15.68 1.99 0.35 −0.52
(0.9912)55.67
(0.9591)70.04
(0.8583)C0/(mg·L−1) Boyd Model K1d K2d C1 C2 R12 R22 50 0.0596 0.4593 −0.1862 −26.0993 0.9274 0.9543 表 2 3DG吸附TC的热力学参数
Table 2. thermodynamic parameters on Adsorption of TC
熵变化(∆S)/
(J·mol−1)焓变化(∆H)/
(kJ·mol−1)吉布斯自由能变化(∆G)/(kJ·mol−1) 328 K 318 K 308 K 298 K 288 K 56.26 10.755 −2.938 −2.849 −2.759 −2.669 −2.580 表 3 3DG吸附TC的3种等温模型参数
Table 3. Parameters of three kinds of isotherm models on 3DG adsorption of TC
等温吸附模型 参数 288 K 298 K 308 K 318 K 328 K Langmuir Qmax/(mg·g−1) 277.78 294.12 303.03 312.5 322.58 KL/(L·mg−1) 0.0843 0.095 0.1162 0.2177 0.252 R2 0.9996 0.9993 0.9996 0.9975 0.9996 Freundlich 1/n 0.5626 0.5602 0.5573 0.557 0.5537 KF/(L·mg−1) 32.544 37.211 42.246 53.464 58.119 R2 0.9715 0.9491 0.9513 0.9758 0.9736 Tempkin KT/(L·mg−1) 0.6465 0.7533 0.8802 1.1909 1.3463 bT 34.924 34.519 34.399 33.064 33.713 R2 0.9956 0.9942 0.9914 0.9969 0.997 表 4 不同吸附剂对TC的最大吸附量
Table 4. Maximum adsorption capacity for TC using different adsorbents
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