电厂飞灰对水体中典型抗生素的吸附特性研究

发布时间：2018-08-22 21:13

【摘要】：我国是抗生素生产和使用大国,抗生素不合理使用或滥用现象严重。抗生素的作用时间和代谢时间较长,在自然环境中难以实现有效降解,一旦进入环境将严重威胁人类健康和生态安全,目前抗生素已成为水环境中最重要的污染物之一。吸附法作为处理水体中抗生素的重要方法之一,吸附材料的选择、吸附条件的优化以及吸附机制的探究已成为研究的热点。燃煤飞灰是燃煤颗粒中所含矿物质经一系列变化而形成,具有比表面积大、表面能高及多活性点的特殊物理化学性质。我国是以煤炭为主要能源的发展中国家,燃煤飞灰作为火力发电厂的一种工业固体废物,年产生量巨大,实现飞灰的综合利用、提高其再利用率,从而减少灰场飞灰贮存量,已成为当务之急。飞灰具有性能稳定、价格低廉的特点,为实现其作为吸附剂处理水体中的污染物提供了可能。本课题分别以电厂燃煤飞灰及其主要成分——氧化铝为吸附剂,在改变吸附剂初始投加量、振荡频率、温度和溶液pH值等条件下,研究了其对水溶液中三种典型抗生素——磺胺(SA)、四环素(TC)和诺氟沙星(NOR)的吸附特性,分析了各吸附体系的动力学、热力学,并在理论上通过分子动力学(Molecular dynamics, MD)简化模型模拟研究了其作用机制,从而为水体中抗生素吸附材料的选择提供了新的方法,也为实现电厂飞灰的资源化利用提供了新的途径。研究结果表明：(1)氧化铝及电厂飞灰吸附去除水体中抗生素的过程,吸附效果受多种因素的影响。在本实验初始投加浓度范围内(0.1～5.0 g·L-1),吸附剂投加质量浓度越高,吸附效果越明显且平衡吸附量越低；在所研究的温度范围(15、25和35℃)内,吸附过程温度控制在25℃时三种抗生素的吸附效果最佳；高频率的振荡可促进吸附；不同pH值条件下吸附剂对各种抗生素的吸附效果差异较大,SA、TC和NOR三种抗生素的吸附过程对应不同的最佳pH值,分析认为这与溶液中不同pH值下抗生素和电厂飞灰中各种成分的溶解度、存在形态及表面电荷种类有关。(2)氧化铝及电厂飞灰吸附三种典型抗生素的机制可通过吸附等温线模型、动力学及热力学分析解释。不同吸附体系对Langmuir和Freundlich吸附等温线模型复合情况不一致,吸附体系整体符合状况不佳,可能与实际飞灰中的成分较为复杂及氧化铝与抗生素的作用机制有关。三种抗生素所对应的体系均较符合准二级动力学模型,表明吸附过程的吸附速率与吸附质浓度的平方成正比。所有吸附体系均符合颗粒内扩散模型,表明氧化铝、电厂飞灰吸附抗生素的过程受膜扩散和内扩散的共同控制,且内扩散速率常数kint随着吸附剂质量浓度的增加而递减,这与传质过程的推动力及抗生素分子的扩散趋势有关。(3)对于氧化铝和电厂飞灰吸附水体中抗生素的体系,均有以下规律：同样吸附剂投加浓度下,吸附剂对TC去除效果最佳,对NOR其次,对SA去除效果最不理想。MD模拟计算的能量数据也与这一结果相符,表明所设计的模拟体系具有合理性及可靠性。
[Abstract]:China is a big country in the production and use of antibiotics, and the irrational use or abuse of antibiotics is serious. Antibiotics have a long acting time and metabolism time. It is difficult to achieve effective degradation in the natural environment. Once entering the environment, it will seriously threaten human health and ecological safety. At present, antibiotics have become one of the most important pollutants in the water environment. Adsorption is one of the most important methods to treat antibiotics in water. The selection of adsorptive materials, the optimization of adsorptive conditions and the study of adsorptive mechanism have become the focus of research. China is a developing country with coal as the main energy source, Coal-fired Fly Ash as a kind of industrial solid waste of thermal power plant, the annual output is huge, realize the comprehensive utilization of fly ash, improve its reuse rate, thereby reducing the fly ash storage in ash yard, has become an urgent matter of the moment. It is possible to use it as an adsorbent for the treatment of pollutants in water. In this paper, three typical antibiotics, sulfonamide (SA) and tetra-sulfonamide (IV), were studied under the conditions of changing the initial dosage of adsorbent, oscillation frequency, temperature and pH value of solution. The adsorption characteristics of cyclinE (TC) and norfloxacin (NOR) were analyzed. The kinetics and thermodynamics of each adsorption system were analyzed. The mechanism of action was simulated by molecular dynamics (MD) simplified model. Thus a new method was provided for the selection of antibiotic adsorbent materials in water and the resource of fly ash from power plant was realized. The results show that: (1) the adsorption efficiency of alumina and fly ash is affected by many factors in the process of removing antibiotics from water. Within the temperature range (15, 25 and 35 degrees), when the temperature of the adsorption process is controlled at 25 degrees, the adsorption effect of the three antibiotics is the best; the high frequency oscillation can promote the adsorption; the adsorption effect of the adsorbent on various antibiotics under different pH conditions is quite different; the adsorption process of SA, TC and NOR three antibiotics corresponds to different optimal pH values, points. The mechanism of adsorption of Three Typical Antibiotics on alumina and fly ash can be explained by adsorption isotherm model, kinetic and thermodynamic analysis. Langmuir and Freundlic in different adsorption systems. The results show that the adsorption rate of the three antibiotics is equal to that of the adsorbate concentration. All adsorption systems conform to the intraparticle diffusion model, indicating that the process of adsorption of antibiotics by alumina and fly ash is controlled by both membrane diffusion and internal diffusion, and the internal diffusion rate constant kint decreases with the increase of adsorbent concentration, which is related to the driving force of mass transfer process and the diffusion trend of antibiotic molecules. 3) For the system of adsorbing antibiotics in water by fly ash of alumina and power plant, there are the following rules: under the same concentration of adsorbent, the adsorbent has the best effect on TC removal, and the second is NOR, and the effect on SA removal is the least ideal. The energy data calculated by MD simulation is also consistent with this result, which shows that the simulation system designed is reasonable and feasible. By sex.
【学位授予单位】：南京师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773

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