水溶液中有机砷的化学氧化过程：动力学和降解途径分析

发布时间：2018-08-21 08:10

【摘要】：有机砷被作为饲料添加剂被广泛地应用于畜牧业中。近年来,有机砷的污染问题越来越受到人们的重视,尤其是有机砷经过自然降解转化,会生成剧毒的无机砷,对环境和人类带来潜在的威胁。阿散酸和洛克沙胂是其中两种最为主要的有机砷饲料添加剂,关于它们的研究还是比较有限的。本文研究了水溶液中有机砷在化学氧化过程中的动力学、热力学以及降解机理。论文的主要内容如下：高锰酸钾氧化降解阿散酸过程符合修正动力学模型。研究了酸碱度、腐植酸以及离子强度对降解过程的影响,酸性条件下,阿散酸的降解速率较大,腐植酸的存在会促进阿散酸的降解,离子强度对整个降解过程没有影响。从热力学的角度分析了降解过程,采用GC-MS推测了降解途径,阿散酸在高锰酸钾的氧化作用下,几乎没有矿化,砷完全被脱下,生成五价砷和苯胺。次氯酸钠氧化降解阿散酸过程采用一般动力学拟合,对阿散酸的反应级数为0.5,对次氯酸钠的反应级数为1.8,整个反应是一个级数为2.3的反应过程。研究了酸碱度、腐植酸以及2种常见离子对降解过程的影响,酸性条件下,阿散酸的降解速率较大,腐植酸的存在会抑制阿散酸的降解,铵根离子抑制了降解过程,碳酸氢根离子对降解过程有一定的促进作用。在真实水体中次氯酸钠降解阿散酸的效果不甚理想。通过砷形态和GC-MS测定了中间产物,砷被氯取代,生成的三价砷迅速被氧化成为五价砷,同时生成三氯苯胺。次氯酸钠氧化降解洛克沙胂过程符合伪一级动力学,对洛克沙胂的反应级数为1,对次氯酸钠的反应级数为1,整个反应是一个二级反应。研究了酸碱度、腐植酸以及2种常见离子对降解过程的影响,酸性条件下,洛克沙胂的降解速率较大,腐植酸的存在会促进洛克沙胂的降解,铵根离子抑制了降解过程,碳酸氢根离子对降解过程有一定的促进作用。在真实水体中次氯酸钠降解洛克沙胂的效果比较理想。通过砷形态和LC-MS测定了中间产物,砷被氯取代,生成的三价砷迅速被氧化成为五价砷,同时生成三氯硝基苯胺。
[Abstract]:Organic arsenic is widely used in animal husbandry as feed additive. In recent years, more and more attention has been paid to the pollution of organic arsenic, especially organic arsenic, which can produce highly toxic inorganic arsenic after natural degradation and transformation, which brings potential threat to the environment and human beings. Arsanilic acid and roxarsone are two of the most important organic arsenic feed additives. The kinetics, thermodynamics and degradation mechanism of organic arsenic in aqueous solution during chemical oxidation were studied. The main contents of this paper are as follows: the oxidation and degradation of arsonic acid by potassium permanganate accords with the modified kinetic model. The effects of acidity, humic acid and ionic strength on the degradation process were studied. Under acidic conditions, the degradation rate of arsonic acid was higher. The presence of humic acid could promote the degradation of arsonic acid, but the ionic strength had no effect on the whole degradation process. The degradation process was analyzed from the viewpoint of thermodynamics. The degradation pathway was inferred by GC-MS. Under the oxidation of potassium permanganate, there was almost no mineralization, and arsenic was completely removed to form pentavalent arsenic and aniline. The process of oxidative degradation of arsonic acid by sodium hypochlorite was fitted by general kinetics. The order of reaction was 0.5 for sodium hypochlorite and 1.8 for sodium hypochlorite. The whole reaction was a process of order 2.3. The effects of pH, humic acid and two common ions on the degradation process were studied. Under acidic conditions, the degradation rate of arsonic acid was higher. The presence of humic acid inhibited the degradation of arsonic acid, and the degradation process was inhibited by ammonium ion. Bicarbonate ions can promote the degradation process to some extent. The effect of sodium hypochlorite on the degradation of arsonic acid in real water is not satisfactory. The intermediate product was determined by arsenic morphology and GC-MS. Arsenic was replaced by chlorine and the resulting trivalent arsenic was quickly oxidized to pentavalent arsenic and trichloroaniline was formed at the same time. The oxidation degradation of roxarsone by sodium hypochlorite accords with pseudo-first-order kinetics. The order of reaction for roxarsone and sodium hypochlorite is 1, and the whole reaction is a second-order reaction. The effects of pH, humic acid and two common ions on the degradation of roxarsone were studied. The degradation rate of roxarsone was higher under acidic conditions. The presence of humic acid promoted the degradation of roxarsone, and the degradation process was inhibited by ammonium ion. Bicarbonate ions can promote the degradation process to some extent. The degradation of roxarsone by sodium hypochlorite in real water is ideal. The intermediate product was determined by arsenic speciation and LC-MS. Arsenic was replaced by chlorine and the resulting trivalent arsenic was quickly oxidized to pentavalent arsenic and trichloronitroaniline was formed at the same time.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X131.2

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