水溶液中有机砷的光化学降解转化研究

发布时间：2018-01-03 18:35

本文关键词：水溶液中有机砷的光化学降解转化研究　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：有机砷制剂作为饲料添加剂被广泛的应用于家禽养殖业中,常见的有机砷制剂有洛克沙胂(ROX)和阿散酸(ASA)。添加的有机砷大部分会随着家禽粪便排出,引起环境的砷污染,并可能对人类健康产生危害。光化学降解是环境中有机污染物重要的降解方式,可以使污染物发生分解和矿化。因此,本论文选取ROX等几种有机砷为研究对象,研究其在不同光降解过程中的降解,考察了环境因素(pH,无机阴离子和腐殖酸等)对其光降解的影响,并探讨了有机砷的光化学降解转化机制,旨在深入了解有机砷在环境中的光化学降解行为。(1)首先,本论文系统研究了ROX厌氧还原产物3-氨基-4-羟基苯胂酸(HAPA)在模拟自然环境下的光化学降解。研究结果表明,环境中短波紫外光(UVC)是导致HAPA的降解的主要原因,而溶解氧的单独存在短期内对HAPA的降解没有影响。并进一步研究HAPA在UVC254下的光化学降解动力学及其影响因素。在UVC254光照下,HAPA的光降解符合伪一级动力学模型。当pH为碱性时,HAPA的降解受到显著的促进。环境中存在的SO42-和Cl-会轻微抑制HAPA的降解,而HCO3-的存在对HAPA的降解有轻微的促进作用。HAPA的光降解主要是由于直接光解,反应过程中生成的1O2对HAPA的降解没有明显影响,但可以促进降解生成的三价砷向五价砷转化。根据反应中离子和中间产物的测定,推导出HAPA可能的降解途径,揭示出了HAPA在光照环境下降解转化机制。(2)其次,系统研究了硝酸根光敏化降解体系中,ROX和ASA的降解转化行为。研究结果表明,模拟太阳光下硝酸根的存在可以有效促进ROX的降解,其降解遵循伪一级动力学。溶液pH会显著影响ROX的降解,尤其在强酸溶液中,ROX降解速率显著增加。该体系中硝酸根吸收光子后可以产生强氧化性的·OH,·OH可以氧化降解ROX。ROX在降解过程中,生成了三价砷和五价砷,且五价砷为最终产物。通过研究太阳光下ROX在实际水体中的降解情况以及砷的形态分布情况,提出了ROX在有硝酸根的自然水体中的转化机制。(3)最后,研究了ROX在UV/PDS体系中的光化学催化降解。研究结果表明,UV和PDS耦合作用可以有效的降解ROX,降解符合二级反应动力学模型,其速率常数为kapp=2.543 s-1 M-1(R2=0.998)。环境因素如pH,无机阴离子,腐殖酸对ROX的降解有很大影响。中性条件下ROX降解最快,酸性和碱性条件都不利于ROX的降解。Cl-对ROX的降解有明显促进作用,而腐殖酸会显著抑制ROX的降解,当腐殖酸浓度为20 mg/L时,约62.5%的ROX降解被抑制。实际水体中ROX的降解受到明显抑制,尤其是污水处理厂出水中。UV/PDS体系中起主要作用的氧化活性物种是SO4-.。在降解过程中,NO3-和五价砷是主要的降解产物。ROX在UV/PDS体系中可以完全矿化,生成对环境无害的CO2,H2O和无机盐。
[Abstract]:As a feed additive, organic arsenic is widely used in poultry industry. The common organic arsenic preparations are roxarsone (Rox) and asalic acid (ASAA). Most of the organic arsenic added will be excreted with poultry feces, causing arsenic pollution in the environment. Photochemical degradation is an important degradation method of organic pollutants in the environment, which can decompose and mineralize pollutants. In this paper, ROX and other organic arsenic were selected as research objects to study their degradation in different photodegradation processes, and the effects of environmental factors such as pH, inorganic anions and humic acid on their photodegradation were investigated. The photochemical degradation mechanism of organic arsenic was discussed in order to understand the photochemical degradation behavior of organic arsenic in the environment. The photochemical degradation of 3-amino-4-hydroxyphenylarsonic acid (3-amino-4-hydroxyphenylarsonic acid), a product of ROX anaerobic reduction, was systematically studied in this paper. The degradation of HAPA is mainly caused by short wave ultraviolet light (UV) in the environment. However, the existence of dissolved oxygen alone had no effect on the degradation of HAPA for a short time. Furthermore, the photochemical degradation kinetics of HAPA under UVC254 and its influencing factors were studied. The photodegradation of HAPA accords with pseudo-first-order kinetic model. When pH is alkaline, the degradation of HAPA is significantly promoted. The presence of SO42- and Cl- in the environment can slightly inhibit the degradation of HAPA. The photodegradation of HCO3- was mainly due to direct photolysis, and the 1O2 produced during the reaction had no obvious effect on the degradation of HAPA. However, it can promote the conversion of trivalent arsenic to pentavalent arsenic. According to the determination of ions and intermediate products in the reaction, the possible degradation pathway of HAPA is deduced. The mechanism of degradation and transformation of HAPA in light environment was revealed. Secondly, the degradation and transformation behavior of HAPA and ASA in the system of nitrate Guang Min degradation were systematically studied. Simulation of the presence of nitrate in sunlight can effectively promote the degradation of ROX, its degradation follows pseudo-first-order kinetics. Solution pH will significantly affect the degradation of ROX, especially in strong acid solution. The degradation rate of ROX was significantly increased. After the nitrate absorbed the photons, the 路OH could produce strong oxidized 路OH, and 路OH could oxidize and degrade ROX.ROX in the process of degradation. Trivalent arsenic and pentavalent arsenic were formed, and pentavalent arsenic was the final product. The degradation of ROX in the real water and the distribution of arsenic species were studied. The conversion mechanism of ROX in natural water with nitrate was proposed. Finally, photochemical catalytic degradation of ROX in UV/PDS system was studied. The coupling of UV and PDS can effectively degrade Rox, and the degradation accords with the second-order reaction kinetics model. Its rate constant is kapp=2.543 s-1 M-1N R2O 0.9980.The environmental factors such as pH, inorganic anion. Humic acid has a great effect on the degradation of ROX. Under neutral conditions, ROX degradation is the fastest, acid and alkaline conditions are not conducive to the degradation of ROX. Cl- has a significant role in promoting the degradation of ROX. Humic acid significantly inhibited the degradation of ROX. When the concentration of humic acid was 20 mg/L, about 62.5% of ROX degradation was inhibited, and the degradation of ROX in the actual water was significantly inhibited. Especially in the effluent of wastewater treatment plant, the main oxidizing active species in the system of UV / PDS is so _ 4-..in the process of degradation. NO3- and pentavalent arsenic are the main degradation products. Rox can be completely mineralized in UV/PDS system to produce environmentally sound CO _ 2H _ 2O and inorganic salts.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X713

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