河流沉积物吸附四环素类抗生素的行为规律研究

发布时间：2017-12-27 12:38

本文关键词：河流沉积物吸附四环素类抗生素的行为规律研究　出处：《东华大学》2017年硕士论文　论文类型：学位论文

【摘要】：四环素类抗生素(TCs)是一种常见的抗生素类药物,已被广泛应用于临床治疗以及水产畜牧养殖业中。由于四环素类抗生素的大量使用,未被充分吸收利用的药物会通过各种方式进入水体以及土壤环境中。世界范围内大多数国家和地区的河流、海洋、地下水、土壤以及沉积物中都检测除了四环素类抗生素的残留。四环素类抗生素极易富集在土壤和沉积物中,因此对四环素类抗生素在水体-沉积物中迁移转化的研究受到国内外学者的关注。由于四环素类抗生素的离子特性以及沉积物组成结构的复杂性,有必要进一步研究环境条件和沉积物组分对沉积物吸附四环素类抗生素过程的影响。本文主要通过室外采集沉积物样品结合室内模拟实验,探究四环素类抗生素在河流沉积物上的吸附行为规律。考察了四环素类抗生素在沉积物上的吸附动力学、热力学特性,水土比、p H和有机质对吸附作用的复合影响;以及使用化学方法选择性去除沉积物中的锰氧化物、铁锰氧化物和有机质,通过对比去除组分前后沉积物吸附量大小,探究沉积物中吸附四环素类抗生素的主要组分。以期进一步阐明四环素类抗生素在河流中的迁移机理和规律,为评价四环素类抗生素的环境风险提供科学依据。经研究已获得以下结论:(1)动力学和热力学研究结果表明,沉积物对TC和OTC的吸附符合Langmuir和Freundlich等温模型;吸附过程是吸热过程,温度的上升有利于吸附的进行。吸附过程符合准二级反应动力学方程,为慢速反应过程。由热力学研究得知该吸附过程是自发进行的吸热反应。TC和OTC的吸附动力热力学特征基本一致,沉积物对TC的吸附量略大于OTC。(2)考察不同水土比(mg:mg)条件下沉积物对TC吸附率随p H变化趋势的结果表明,水土比的改变使达到最大吸附率的p H条件和最大吸附率值都发生了转变,在水土比为0.125和0.25时,达到最大吸附率的p H值是3,最大吸附率分别是96.8和95.3%;水土比0.5时,达到最大吸附率的p H值转变为了5,且最大吸附率降低至82.82%;发生这种转变的原因可能在低吸附平衡浓度时沉积物吸附TC主要通过阳离子交换作用,而在高吸附平衡浓度时吸附主要通过络合作用、氧化作用等。关于有机质对吸附的影响,不是一直会保持单纯的促进或抑制作用,而是在某些条件下起促进作用,某些条件下起抑制作用。若条件发生改变,促进作用可能突变为抑制作用。具体如:p H=3时,吸附平衡浓度高时有机质的存在抑制了沉积物对TC的吸附,而随着平衡浓度的降低转变为促进吸附;p H=5时,平衡浓度高时有机质促进沉积物对TC的吸附,并随着平衡浓度降低转变为抑制吸附;p H=9时,无论平衡浓度高低有机质的存在均会促进沉积物对TC的吸附。(3)对沉积物主要组分(铁氧化物、锰氧化物、有机质)对沉积物吸附TCs吸附能力及贡献的研究结果表明,沉积物及其主要组分对TCs的吸附过程特征符合Langmuir吸附等温方程,相关系数达0.95以上;达到吸附饱和时沉积物中各组分对TCs的吸附能力大小顺序为锰氧化物有机质铁氧化物残渣态;各组分对TCs的绝对吸附贡献量大小顺序为锰氧化物残渣态铁氧化物有机质。其中,锰氧化物在沉积物中含量较小,只有0.05%,却对TCs的吸附贡献率最大(55.83%)。即所采集的九龙江典型沉积物对TCs的吸附起最主要和关键作用的组分是锰氧化物。不同地理位点的沉积物理化性质差异很大,对TCs的吸附能力与锰氧化物含量有一定的相关性,验证了前述结论。
[Abstract]:Tetracycline antibiotic (TCs) is a common antibiotic drug, which has been widely used in clinical treatment and aquaculture. Because of the large use of tetracycline antibiotics, the drugs that are not fully absorbed into the water and the soil environment in a variety of ways. The residues of tetracycline antibiotics are detected in rivers, oceans, ground water, soil and sediments of most countries and regions worldwide. Tetracycline antibiotics are easily concentrated in soil and sediment. Therefore, the research on migration and transformation of tetracyclines in water sediment has attracted the attention of scholars at home and abroad. Because of the ionic characteristics of tetracycline antibiotics and the complexity of sediment composition and structure, it is necessary to further study the effects of environmental conditions and sediment components on the adsorption of tetracycline antibiotics in sediments. In this paper, the adsorption behavior of tetracycline antibiotics on river sediments was investigated by collecting sediment samples and indoor simulation experiments. Effects of tetracycline adsorption kinetics on sediments, the thermodynamic characteristics of the composite effect of ratio of water to P, H and organic matter on sorption; and the use of chemical method for selective removal of sediment in manganese oxide, iron and manganese oxides and organic matter removal components before and after adsorption of sediment size by comparing the main Group on sediments in the adsorption of tetracycline antibiotics. In order to further clarify the mechanism and law of the transfer of tetracycline antibiotics in rivers, it provides a scientific basis for evaluating the environmental risk of tetracycline antibiotics. The following conclusions have been drawn: (1) the kinetic and thermodynamic studies show that the adsorption of TC and OTC on sediments conforms to the isothermal models of Langmuir and Freundlich. The adsorption process is endothermic process, and the rise of temperature is conducive to the adsorption. The adsorption process is in accordance with the kinetic equation of the quasi two order reaction, which is a slow reaction process. Thermodynamics studies have shown that the adsorption process is a spontaneous endothermic reaction. The thermodynamic characteristics of adsorption dynamics of TC and OTC are basically the same, and the amount of adsorption of the sediments to TC is slightly greater than that of OTC. (2) the effects of different ratio of water and soil (mg:mg) under the conditions of sediment adsorption rate of TC changes with P H trend. The results show that the change ratio of the soil so as to achieve the maximum adsorption rate of P H and the maximum adsorption rate values have changed, in the ratio of water was 0.125 and 0.25, the maximum adsorption rate of p the H value is 3, the maximum adsorption rate were 96.8 and 95.3%; and 0.5, the maximum adsorption rate of P H value change to 5, and the maximum adsorption rate decreased to 82.82%; the reasons for this change may be in the low concentration sediment adsorption equilibrium adsorption of TC by cation exchange, and in the high concentration of adsorption equilibrium adsorption mainly by complexation oxidation. The effect of organic matter on adsorption does not always maintain simple promotion or inhibition, but plays a promoting role under certain conditions. If the condition changes, the effect of promotion may be inhibited. Specific such as: P H=3, the adsorption equilibrium at high concentrations of organic matter could inhibit the adsorption of TC, and with the decrease of equilibrium concentration change in order to promote the adsorption; P H=5, the high concentration of organic matter promoted the adsorption equilibrium of sediments on TC, and with the equilibrium concentration reduced into p inhibited adsorption; H=9 both the equilibrium concentration, the existence of the organic matter will promote the sediment sorption of TC. (3) the major components of sediments (iron oxide, manganese oxide and organic matter) of sediment TCs adsorption capacity and the contribution of the results show that the sediments and the characteristics of the main components of the adsorption process of TCs accords with Langmuir adsorption isothermal equation, the correlation coefficient reached to 0.95; adsorption reached saturation in the sediments of each component the adsorption capacity of TCs order of manganese oxide organic iron oxide residue; components of absolute adsorption of TCs on the contribution of the order of manganese oxide iron oxide residue organic matter. Among them, the manganese oxide content in the sediments is small, only 0.05%, but the largest contribution to the adsorption of TCs (55.83%). That is, the main and key component of the adsorption of nine typical Longjiang sediments on TCs is manganese oxide. The physicochemical properties of different geographic loci are very different. There is a certain correlation between the adsorption capacity of TCs and the content of manganese oxide, which validates the previous conclusion.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X522

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