【作者】 郭学涛；

【导师】 黄伟林；

【作者基本信息】 华南理工大学 ， 环境科学与工程， 2014， 博士

【摘要】 抗生素作为一种高效药物被广泛用于人和动物，以预防和治疗疾病，同时也作为饲料添加剂促进动物的生长。抗生素使用后，大部分抗生素药物以其母体或者活性代谢物的形式进入环境中，给人体健康和生态环境造成潜在的威胁。目前国内外学者对抗生素在环境中的环境化学行为已经展开了一些研究，但对抗生素在环境中的迁移和转化的认识依然不够充分，且对于抗生素在环境介质上的吸附机制，及在自然环境中发生的非生物转化认识依然不足。因此，本文以泰乐菌素（TYL）和磺胺二甲基嘧啶（SMT）为研究对象，考察了环境中大量存在的铁氧化物（针铁矿）和腐殖酸对抗生素的吸附特性及吸附机理，进而又考察了环境条件对针铁矿在可见光作用下对抗生素的催化降解的影响，最后研究了针铁矿与腐殖酸之间的微观界面作用对两种抗生素吸附和光降解的影响。论文取得的主要研究成果如下：1.系统研究了TYL和SMT在针铁矿上的吸附特性和吸附机制。研究发现：TYL和SMT在针铁矿上的吸附分别在5h和12h达到吸附平衡，且吸附动力学均可用二级动力学和扩散模型较好的拟合，且吸附速率随着初始浓度的增加逐渐降低，吸附过程主要包括外部扩散、界面层扩散以及孔内扩散。TYL在针铁矿上的吸附是一个自发的放热的过程而SMT在针铁矿上的吸附则是一个自发的吸热的过程。TYL和SMT在针铁矿上的吸附均是非线性的吸附且吸附受溶液pH和离子强度影响较大。TYL在针铁矿上的吸附主要受静电作用、氢键作用、离子交换和表面络合作用的影响，其中表面络合作用是主导吸附的关键因素。而SMT在针铁矿上的吸附主要受静电作用、范德华力、氢键作用、表面络合和π-π EDA的共用电子对作用共同主导。2. TYL和SMT在腐殖酸上吸附在24h均可达到吸附平衡，且吸附动力学可以用二级动力学和扩散模型较好的拟合，且吸附速率随着初始浓度的增加逐渐降低。TYL和SMT在腐殖酸上的吸附是一个自发的放热过程，吸附等温线可以用线性吸附模型和Freundlich模型较好的拟合；TYL和SMT在腐殖酸上的吸附与溶液pH值和离子强度有关，吸附均随着溶液pH值和离子强度的增加而减小。TYL在腐殖酸上的吸附主要受静电作用、疏水性作用、氢键作用、离子交换作用的影响，其中离子交换是主导吸附的关键因素。而SMT在腐殖酸上的吸附，主要受静电斥力、氢键作用力、离子交换、疏水性作用力和表面络合是主导。3. TYL和SMT在可见光的作用下有一定的自然降解能力，并且当有针铁矿存在时催化降解速率明显提高，且其光催化降解速率随着TYL和SMT初始浓度的增加减少，随着溶液离子强度的增加而减小，随着溶液中溶解性有机质（DOM）浓度的增加而增加，TYL的降解速率随着溶液pH值的增加先减小再增加而SMT的催化降解速率随着pH值的增加而逐渐减小。TYL和SMT在针铁矿上光解与其在针铁矿上的吸附及溶液中的溶解Fe3+浓度相关，其光催化可能包括均相反应和异相反应两个过程。且溶液中DOM的存在有助于光解作用，DOM的浓度越高，TYL和SMT的光解速率越大。因此在评估抗生素的环境风险时，应当综合考虑各种不同环境因素对抗生素在环境中转化过程的影响。4.针铁矿与腐殖酸之间的微观界面作用的研究，通过一系列表征（SEM、EDX、FTIR及拉曼光谱）研究了负载腐殖酸后的针铁矿。研究发现针铁矿通过其表面上的活性位点及活性基团和腐殖酸进行结合，这种结合方式以化学方式为主。通过研究负载腐殖酸后的针铁矿对两种抗生素的吸附及光催化降解特性，考察了针铁矿与腐殖酸之间的微观界面作用对抗生素在环境中迁移和转化的影响。研究发现当有腐殖酸存在时，针铁矿对抗生素的吸附速率和能力都明显提高，并且吸附随着负载腐殖酸浓度的增加而逐渐增加，负载腐殖酸后的针铁矿对抗生素的吸附主要表现为疏水性的分配作用、氢键作用、离子交换和表面络合机制为主。且腐殖酸的存在也有利于针铁矿对TYL和SMT的光解，负载腐殖酸后的针铁矿对TYL和SMT的催化降解效率随着复合物中腐殖酸浓度的增加逐渐增加。针铁矿与腐殖酸形成的复合物配体，在氧化TYL和SMT的同时针铁矿发生了溶解，生成了大量的Fe2+，Fe2+在液相中与腐殖酸可以再次进行络合，生成的配体可以再次参与氧化还原反应，又可形成高价铁的络合物，从而通过铁离子的循环促使光化学反应循环从而提高催化降解的效率。更多还原

【Abstract】 Antibiotics were widely used in humans and animals to treat microbial infections, andalso as feed additive to promote growth of livestock animals. After administration of anantibiotic, a significant fraction is excreted in the parent form or its metabolite forms alongwith urine and feces, and then directly or indirectly reaches the aquatic and terrestrialenvironmental, which would pose a negative effect on aquatic and terrestrial organism andhuman health. Recently, many studies have been done about the environmental chemicalbehavior of antibiotics in the environments. However, few studies have been done about thetransport and transforation of antibioltics in the livestock farms, which are the major sourcesof antibiotics in the environments. Meanwhile the sorption mechanism of antibiotics in theenvironmental medium and the abiotic transformation in the natural environment is stillinsufficient. So tylosin (TYL) and sulfamethazine (SMT), the widely used veterinaryantibiotics were chosen as the sorbates. The sorption properties and sorption mechanism ofantibiotics on goethite and humic acid were investigated. The influences of environmentalfactors on the photodegradation of tylosin by goethite and the influence of the microcosmicinterfacial interaction between goethite and humic acid on the and transform of antibioltics inthe aqueous phase were also investigated. The main experiments and conclusions are asfollows:1．Sorption of TYL and SMT on goethite was systemaly measured using a batchtechnique. The results showed that the sorption of TYL and SMT could attain apparentequilibrium within5hrs and12hrs. The sorption rates for TYL and SMT decreased as theinitial concentration increased. The sorption process might be constituted with the initialboundary layer diffusion or external surface, then the intraparticle diffusion or pore diffusionstage and finally equilibrium stage related with the sorption on the interior surface of sorbent.Thermodynamics calculations revealed that the sorption of TYL on goethite was exothermaland spontaneous and SMT was endothermic and spontaneous. Sorption of TYL and SMTwere nonlinear and the sorption capacities were influenced by the pH and ionic strength. Thesorption mechanism of TYL might be related with surface complexation, electrostatic repulsion, and H-bonding on goethite. But for SMT the sorption mechanisms might involveVan der Waalsforce, electrostatic interactions, H-bonding, outer and inner-sphere complexesand π-π EDA interactions.2．The apparent equilibration times of sorption of TYL and SMT on humic acid were24hrs and the sorption rates for TYL and SMT decreased as the initial concentrationincreased. The sorption of TYL and SMT on humic acid was fitted by Linear and Freundlichmodels and the sorption was exothermal and spontaneous. Sorption of TYL and SMT wereobvious influenced by the pH and ionic strength and sorption were decreased with theincrease of pH and ionic strength. The main factors for sorption of TYL on humic acid werehydrophobic interaction, H-bonding and ion exchange but ionic exchange might dominate thesorption. The sorption mechanism of SMT on humic acid might be related to hydrophobicinteractions, surface complexation, electrostatic repulsion, and H-bonding.3．TYL and SMT could be degradation under the action of visible light in the natureenvironment, but when goethite existed the rate of catalytic degradation increasedsignificantly. The photodegradation rate of TYL and SMT decreased with the increase ofinitial concentrations and ionic strength, but the photodegradation rate of TYL and SMTincreased with the increase of concentrations of DOM. For TYL the photodegradation ratewas primarily decreased and then increased with the the increase of pH, but for SMT it wasdecreased all the time with the increase of pH. The photodegradation of TYL and SMT ongoethite might be related to the sorption of antibiotics on goethite and the soluble Fe3+concentration in the solution and the degradation process included the homogeneous reactionin the solution and the heterogeneous reaction at goethite surface. The DOM in the solutioncould promote the photodegradation of TYL and SMT by goethite. It should be noted toassess the influence of environmental factors on the transforation of TYL and SMT in theenvironment.4．The microcosmic interfacial interactions mechanism between goethite and humicacid were investigated the characterization of SEM, EDX, FTIR and Raman spectroscopy. Itcould be found that goethite could combined with humic acid through the surface active sites and active group and the combination is priority with chemical methods. The influence ofmicrocosmic interfacial interaction between goethite and humic acid on the transport andtransforation of antibioltics in the aqueous phase were also investigated the sorption andphotocatalysis of TYL and SMT by the complex of goethite and humic acid. It could be foundthat sorption rate and capacity of TYL and SMT on goethite increased significantly in thepresence of humic acid and the sorption rate and capacity increased with the increasedconcentrations of humic acid in the complexs. The sorption mechanism of TYL and SMT onthe complex might be related to hydrophobic interactions, H-bonding, ion exchange andsurface complexation. The presence of humic acids was conducive to the photolysis of TYLand SMT by goethite and the catalytic degradation efficiency of TYL and SMT increased withthe increase of concentration of humic acid in the complex. The ligand of goethite and humicacid could generate Fe2+into the liquid phase when the catalytic degradation of TYL andSMT by the complex of goethite and humic acid. The Fe2+could combined with humic acidand the oxidation for its ligands, which could improve the efficiency of catalytic degradationform high iron complex compound through the cycling of iron ions.更多还原