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抗生素是一类常用药品,其中氟喹诺酮(FQs)类药物是抗生素的主要代表品种之一,其广泛应用于医疗、畜牧和水产养殖业等[1-4]. 但由于抗生素的滥用和不当处置导致FQs等药物污染水体[5-6];据国内外报道,诸多国家的江、河、湖泊等地表水中均检测发现FQs[7-9]. 在众多水处理工艺中,相比于混凝、光催化及高级氧化等[10-12],吸附法具有操作简单且处理效果佳等优点[13-14]. 近年来,天然高分子类吸附剂由于其价格低廉且环境友好等重要特点而被广泛关注[15]. 单宁酸(TA)是自然界中仅次于纤维素和木质素的第三大天然高分子材料[16-17],存在于柿子皮、葡萄皮及杨梅等植物中,来源广泛,成本低廉,易提取且生物相容性好。此外,TA含有丰富的酚羟基及羧基等含氧官能团,可与多种重金属及有机污染物等通过鳌合、静电吸引、氢键等相互作用[18-19]. 然而,TA在去除FQs污染物中的研究还鲜有报道,但FQs与TA在分子结构上均含有芳香环及羟基等官能团,它们应能以多种相互作用方式有效结合[16-20]. 因此TA被认为是一种潜在可高效去除FQs的绿色吸附剂材料. 然而TA易溶于水,一般不能直接作为吸附剂使用[20]. 由于TA可与多种金属离子发生鳌合作用,如:铁(Fe)、锆(Zr)、钛(Ti)、铜(Cu)、钼(Mo)、钌(Ru)、钆(Gd)等,可有效提高其成形性[21-23],且这种鳌合作用反应条件温和,反应效率高且操作简单[24]. 其中钛离子为+4价,具有较高电荷,除可有效鳌合固定TA还可与水体中多种有机污染物作用,具有潜在的协同吸附作用,且金属钛生物毒性低环境友好[25]. 开发基于天然高分子单宁酸复合钛盐的绿色吸附剂材料具有重要的现实意义,然而至今上述相关材料的开发及应用机制研究还很不充分.
本文采用四氯化钛为改性剂,通过调节钛盐用量,一步法制备系列单宁酸-钛(TA-Ti)复合吸附剂材料. 应用傅里叶红外光谱(FTIR)、X射线光电子能谱(XPS)、环境扫描电子显微镜(ESEM)、能量色散X射线能谱(EDS)、X射线衍射(XRD)及Zeta电位等手段考察复合吸附剂的分子结构及表面微观形貌. 以一种常见的FQs氧氟沙星(OFL)为代表,系统考察TA-Ti对OFL的吸附性能,详细研究溶液pH、污染物浓度、吸附时间及共存无机盐与天然有机物等对其吸附性能影响。对具有与OFL相似结构的FQs环丙沙星(CIP)和恩诺沙星(ENR)及其两种亚结构类似物氟甲喹(FLU)和1-(2-氟苯基)哌嗪(FPP)的吸附效果进行对比,结合吸附前后吸附剂FTIR和XPS的变化,以及吸附动力学与等温吸附模型分析,深入探讨TA-Ti对OFL的吸附机制.
单宁酸-钛复合吸附剂的制备及其对氟喹诺酮类抗生素的吸附去除
Preparation of tannic acid - titanium composite adsorbent and its adsorption performance and mechanisms in removal of fluoroquinolone antibiotics
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摘要: 本文以一种绿色环保且来源广泛的天然高分子单宁酸(TA)为原材料,四氯化钛为改性剂,一步法制得一系列单宁酸-钛(TA-Ti)复合吸附剂.首先通过多种表征技术考察了吸附剂的分子结构及其表面微观形貌等;针对目前在地表水中已发现的氟喹诺酮类抗生素(FQs),以氧氟沙星(OFL)为代表,系统研究了TA-Ti对OFL的吸附性能,详细考察了溶液pH、污染物浓度、吸附时间及不同共存物等对TA-Ti吸附性能的影响;并对具有与OFL相似结构的FQs及其两种亚结构类似物的吸附效果进行对比,结合吸附前后吸附剂傅里叶红外光谱和X射线光电子能谱谱图的变化,以及吸附动力学与等温吸附模型分析等,深入探讨了TA-Ti对OFL的吸附机制.TA可通过静电吸引、氢键、负电荷辅助氢键及π—π相互作用等与FQs作用;此外,钛离子不仅作为TA的交联剂,同时还可通过螯合作用协同吸附FQs,有效提高TA对FQs的吸附性能,对OFL理论最优吸附量为1.028 mmol·g−1. 本文提供了一种绿色环保的高效吸附剂材料,可有效地净化FQs有机微污染水体,提高用水安全.Abstract: In this work, a series of novel composite adsorbents (TA-Ti) was fabricated using tannic acid (TA) as the raw material and titanium tetrachloride as the modifier. TA is a commonly natural polymer with the advantages of wide source and environmental-friendliness. The molecular structure and surface morphology of this composite adsorbent were investigated by various characterizations. Fluoroquinolones antibiotics (FQs) were currently found in surface water. Among various FQs, ofloxacin (OFL) was selected as a representative in this work. The adsorption performance of TA-Ti in removal of OFL has been investigated systematically. The effects of solution pH, OFL concentration, contact time, coexisting inorganic salt and natural organic substance were studied in detail. The behaviors of TA-Ti in adsorption of some FQs with similar structures to OFL and their two substructural analogies were compared. The adsorption mechanisms have been discussed in detail on the basis of the changes in the Fourier transform infrared and X-ray photoelectron spectra of TA-Ti before and after adsorption as well as the analysis of the adsorption kinetics and isotherms. The efficient adsorption of FQs by TA-Ti was ascribed to the synergetic effects of electrostatic attraction, hydrogen bonding, negatively charged assisted hydrogen bonding, and π—π interactions between TA and FQs; besides, Ti4+ not only acted as a cross-linking agent for TA but also synergistically adsorbed FQs through chelation effect, thereby causing a notably improved adsorption performance. The theoretical maximal OFL uptake of TA-Ti was 1.028 mmol·g−1. In short, this work provided an environmentally-friendly and high-efficient adsorbent that can effectively purify organic micro-polluted water and further improve water safety.
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Key words:
- fluoroquinolones /
- ofloxacin /
- tannic acid /
- titanium ion /
- adsorption performance /
- adsorption mechanisms
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图 3 (a)不同初始pH对TA-Ti1吸附FQs的影响,(b)TA-Ti1吸附前后的O1s XPS谱图,(c)TA-Ti1对不同FQs在不同初始pH条件下的吸附容量,(d) OFL与Ti4+反应前后的紫外吸收谱图和(e) TA-Ti1吸附前后的Ti2p XPS谱图
Figure 3. (a) Effect of different initial pH on adsorption of OFL, (b) O1s XPS spectra of TA-Ti1 before and after adsorption, (c) the adsorption capacities of TA-Ti1 for various FQs under various pH levels, (d) UV-vis spectra of OFL with and without Ti4+, (e) Ti2p XPS spectra of TA-Ti1 before and after adsorption
表 1 吸附实验条件.
Table 1. Conditions of adsorption experiments.
实验名称
Adsorption experiment吸附剂
Adsorbent投加量/mg Dosage pH 温度/K Temperature 吸附时间/h Contact time FQs浓度/(mol·L−.1)Concentration FQs体积/mL Volume 备注
RemarkspH影响 TA-Ti1
TA-Ti2
TA-Ti35 3.0—10.0 298 12 0.2 30 OFL, CIP, ENR, FLU, FPP 等温吸附 TA-Ti1 5 8.0 298 12 0.05—0.25 30 — 吸附动力学 TA-Ti1 50 8.0 298 0—12 0.2 300 — 无机盐影响 TA-Ti1 5 8.0 298 12 0.2 30 cNaCl = 0—
50 mmol·L−.1有机物影响 TA-Ti1 5 8.0 298 12 0.2 30 cHA = 0—
50 mg·L−.1表 2 氟喹诺酮类抗生素的结构参数及其色谱检测条件.
Table 2. Physicochemical parameters of various FQs and their chromatographic conditions.
FQs 分子结构
Molecular structure分子量
Molecular weightlg Kowa 流动相A和B比例
Ratio of mobile phase
A to B (V:V)紫外检测波长/nm
UV detection
wavelengthOFL[26-27]
pKa1 = 5.98
pKa2 = 8.00361 −0.39 82:18* 285 CIP[26-27]
pKa1 = 6.14
pKa2 = 8.85331 0.28 82:18* 285 ENR[26-27]
pKa1 = 6.20
pKa2 = 8.13359 0.7 82:18* 285 FLU[27]
pKa = 6.29261 50:50* 232 FPP[27]
pKa1 = 4.49
pKa2 = 8.63180 85:15* 232 *:流动相A是HPLC级0.8%(V:V)的乙酸溶液,流动相B为HPLC级乙腈.
*:Mobile phase A was HPLC grade 0.8% (V:V) acetic acid solution, and mobile phase B was HPLC grade acetonitrile.表 3 TA-Ti1对OFL吸附的吸附等温线和吸附动力学拟合参数表(pH8.0,温度298 K)
Table 3. Isothermal adsorption and adsorption kinetics fitting parameters of TA-Ti1 in adsorption of OFL at pH of 8.0 and 298 K
qmax,exp/
(mmol·g−1)朗缪尔模型
Langmuir model弗兰德里希模型
Freundlich modelqm /(mmol·g−1) b/(L·mmol−1) R2 Kf n R2 0.971 1.028 101.896 0.958 1.055 4.614 0.906 qmax,exp/
(mmol·g−1)准一级动力学模型
Pseudo-first-order model准二级动力模型
Pseudo-second-order modelElovich 模型
Elovich modelqe1, cal/
(mmol·g−1)k1/h−1 R2 qe2 cal/
(mmol·g−1)k2/
(g·(mmol∙h)−1)R2 qe3 cal/
(mmol·g−1)AE BE R2 0.971 0.889 5.293 0.898 0.932 8.630 0.967 1.003 0.724 0.112 0.982 颗粒内扩散模型
Intraparticle diffusionkp1/
(mmol·(g∙h0.5)−1)C1/
(mmol·g−1)R2 kp2/
(mmol·(g∙h0.5)−1)C2/
(mmol·g−1)R2 kp3/
(mmol·(g∙h0.5)−1)C3/
(mmol·g−1)R2 0.822 0.105 0.889 0.101 0.676 0.946 0.045 0.822 0.946 -
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