【作者】 刘牛；

【导师】 刘凡； 谭文峰；

【作者基本信息】 华中农业大学 ， 土壤学， 2012， 博士

【摘要】 四环素类抗生素(tetracycline antibiotics, TC)是一种常见的兽用抗生素,由于大量不合理的施用,造成土壤、沉积物及水环境的潜在污染,其在环境中的行为和归趋已成为土壤学和环境科学等领域研究的热点之一。蒙脱石是土壤和环境中常见的粘土矿物,其具有可膨胀性、比表面积大、阳离子交换量高等特点,被广泛应用于环境污染的治理材料。本论文以蒙脱石为材料,选择三种不同烷基链长的季铵盐表面活性剂对其进行修饰,制备出一系列有机蒙脱石。采用X-射线衍射(XRD)、扫描电镜(SEM)、红外图谱(FTIR)、热重(TG)与差热(DTA)分析及孔径分析等技术与手段,研究了烷基链链长和加入量对蒙脱石矿物晶体结构和层间域的影响；结合动力学吸附、等温吸附实验,探讨有机蒙脱石对溶液中盐酸四环素的吸附性能,阐明二者之间的相互作用机理。主要结果如下：1.经季铵盐表面活性剂(四甲基溴化铵/Tetramethylammonium bromide, TMAB;十二烷基三甲基溴化铵/dodecyltrimethylammonium bromide, DDTMAB;十六烷基三甲基溴化铵/hexadecyltrimethylammonium bromide, HDTMAB)修饰的蒙脱石,相比于钠基蒙脱石(Na-mont)来说,其层间距增大、有机碳含量增加,而比表面积减小,孔径以介孔为主,矿物表面亲水性减弱、疏水性增强。热重与差热分析结果表明,有机蒙脱石与蒙脱石相比,表面及层间含水量减少,结构水脱羟温度随着季铵盐表面活性剂加入量的增加(0.2CEC、1.0CEC)而降低。当加入量较低(0.2CEC)时,TMA阳离子在蒙脱石矿物层间是分散的、孤立的存在,DDTMA和HDTMA阳离子在蒙脱石层间均以水平单层排列；当加入量高(1.0CEC)时,TMA阳离子在蒙脱石层间单层排列、结合紧密,DDTMA阳离子是水平双层排列,HDTMA阳离子在矿物层间有水平单层和倾斜单层两种排列方式。2.有机蒙脱石对四环素的初始吸附速率均高于钠基蒙脱石,初始2h内可达到最大吸附量的80%以上,24h内基本达到吸附平衡,高加入量的有机蒙脱石达到吸附平衡的时间相对较短。准二级动力学方程能较好地拟合有机蒙脱石对四环素的吸附动力学过程。3.钠基蒙脱石和有机蒙脱石对四环素的等温吸附曲线均符合Langmuir模型和Freundlich模型。有机蒙脱石对四环素的吸附容量(1000-2000mmol/kg)均高于钠基蒙脱石(769mmol/kg),且有机蒙脱石对四环素的性能主要受修饰剂类型的影响,最大吸附量(Qmax)随季铵盐链长的增加而增加。4.Freundlich方程拟合结果表明,有机蒙脱石对四环素的吸附参数(n和KF)均高于钠基蒙脱石,且随着有机修饰剂加入量的增加,参数n值增大,矿物表面异质性增强,对四环素的吸附性能增强。随着有机碳含量的增加,矿物中有机碳吸附常数(KOC)减小,对四环素的吸附性能增强,表明季铵盐阳离子在矿物层间的排列方式可能是影响吸附性能的另一要素。5.当体系pH较低(3～4)时,pH对有机蒙脱石吸附四环素的影响最明显,且随着季铵盐加入量的增加而增加；随着体系pH的升高(4～5.5),有机蒙脱石对四环素的吸附分配作用逐渐降低；当体系pH介于5.5-7,吸附分配系数趋于恒定,体系pH对有机蒙脱石吸附四环素的影响较小。吸附分配系数(KD)可较好地反映体系pH对有机蒙脱石吸附四环素的影响。更多还原

【Abstract】 Tetracycline antibiotics (TCs) are one of the most commonly veterinary pharmaceuticals. Misuse of TC, TC has been a potential pollutant in soil, sediment and aquatic environments. Therefore, the behavior and fate of tetracycline are always the hot topic in the field of soil science and environmental science. Montmorillonite is one of the most common clay minerals in soils, and has always been used as materials for environmental pollution treatment, due to its high specific surface area (SSA), swelling ability and high cation exchange capacity. In this study, a series of organo-montmorillonites (organo-monts) have been synthesized by using the sodium montmorillonite (Na-mont), which is modified by three different alkyl chain quaternary ammonium surfactants (QACs), respectively. The crystalline structure and interlayer spaces of the tested samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared adsorption spectrum (FTIR), thermal gravimetric (TG) and differential thermal analysis (DTA), pore size and microscope scanning methods (SEM). The adsorption properties and mechanisms of tetracycline organo-monts were investigated by using the adsorption kinetic and isotherm adsorption experiments. The main results were listed as follows:1. The basal spacing and organic carbon contents of the organo-monts modified by QACs (tetramethylammonium bromide, TMAB; dodecyltrimethylammonium bromide, DDTMAB and hexadecyltrimethylammonium bromide, HDTMAB) increased with respect to Na-mont. The SSAs of organo-monts were decreased, and the main pores were mesoporous. The hydrophilic of organo-monts surfaces decreased, and the hydrophobic properties enhanced. The TG-DTA results suggested that the water contents of organo-monts and its interlayer decreased, and the temperatures of dehydroxylation decreased with increasing amount of QACs (0.2CEC and1.0CEC). At low loading (0.2CEC), the TMA cations were single, isolated with each other in the interlayer, and the DDTMA and HDTMA cations were lateral monolayer in the interlayer. While at high loading (1.0CEC), the TMA cations were interaction with each other, and it makes the silicate sheet closely together; DDTMA cations were lateral bilayer in the interlayer and HDTMA cations were lateral monolayer and paraffin-type monolayer between the silicates.2. The initial adsorption rates of all organo-monts were higher than Na-mont. The adsorption kinetics reactions of organo-monts and Na-mont were rapid and80%of adsorption capacities of the tested samples were achieved in the first2h and the adsorption reaction reached equilibrium state after24h. The adsorption equilibrium times of high loading organo-monts were short than that of low loading. The processes of TC adsorption on the organo-monts could be well fitted by the pseudo-second-order equation.3. Both the Langmuir and Freundlich model could well fit the adsorption isotherms. The maximum adsorption capacities of TC on the organo-monts (1000-2000mmol/kg) were considerably higher than that on Na-mont (769mmol/kg). The maximum sorption capacities (Qmax) of TC on organo-monts were increased as the QACs loading increased, and it was influenced by the types of QACs.4. The Freundlich parameters (n and KF) values of organo-monts were higher than that of Na-mont, and the parameter of n values increased with the loading increasing. The promotion of the TC adsorption on the surface of montmorillonite was caused by a more homogeneous sorbent. The values of organic carbon normalized partition coefficient (Koc) for each organo-monts decreased with increasing organic carbon contents. The arrangement of QACs in the interlayers of silicates is one of the possible factors affected the sorption properties.5. The adsorption partition coefficient (KD) was relatively high at low pH (3-4), and all the organo-monts with high QACs loading have higher KD than those with low loading. The adsorption partition coefficient decreased significantly at pH4-5.5and remained nearly constant between pH5.5and7, the pH has almost no influence on organo-monts adsorption of TC. The adsorption partition coefficient (KD) could well reveal the effect of pH on adsorption on organo-monts.更多还原