【作者】 李娟；

【导师】 江进；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2020， 博士

【摘要】 碘代芳香类有机物作为小分子碘代有机物（如碘仿和一碘乙酸）的重要前体物,其毒性高于碘代脂肪类副产物的毒性,且远高于氯代和溴代类似物的毒性。碘代芳香类有机物的生成直接影响水质安全,因此受到研究学者的关注。锰氧化物（高锰酸钾（KMnO₄）和二氧化锰（MnO₂））具有较好的稳定性和经济性,被广泛用于去除水环境中的有机和无机污染物。研究发现KMnO₄和MnO₂处理含碘水时将引起小分子碘代有机物的生成,威胁其在水处理中的广泛应用。然而,现阶段关于锰氧化物处理含碘水过程中,碘代芳香类有机物的生成规律以及相应调控方法的研究尚属空白。论文选取结构不同的酚类有机物为研究对象,考察了碘离子（I^-）存在条件下,KMnO₄和MnO₂氧化酚类有机物过程中碘代芳香类有机物的生成机制,并提出了利用化学氧化剂单过硫酸盐（PMS）调控碘代芳香类有机物生成的方法。论文首先探究了I^-对KMnO₄氧化不同酚类有机物效能的影响以及影响机制。结果表明:以尼泊金酯为模型酚类有机物建立的动力学模型可以很好拟合其在各个条件下的转化规律,证明了I^-对KMnO₄氧化酚类有机物效能的影响主要与原位生成的次碘酸（HOI）的暴露量有关。HOI暴露量越大,I^-对KMnO₄氧化酚类有机物效能的促进程度越大。HOI暴露量与有机物结构密切相关:含供电子基团的酚类有机物（如双酚A和三氯生）与KMnO₄反应速率高,体系中HOI暴露量较低;反之,含吸电子基团的酚类有机物（如双酚S和尼泊金酯）与KMnO₄反应速率低,体系中HOI暴露量较高。I^-促进KMnO₄转化酚类有机物效能的同时伴随着碘代芳香类有机物的生成,主要是HOI与酚类有机物发生一次或多次亲电取代反应而生成。一般而言,KMnO₄氧化体系中,HOI暴露量越大,碘代芳香类有机物的生成量也较大。在相同条件下,MnO₂氧化三种双酚类有机物的效能以双酚A>双酚AF>>双酚S的顺序递减,主要与双酚类有机物的结构有关。双酚A结构中的供电子烷基基团提高了其与MnO₂的反应活性,而双酚AF和双酚S结构中的氟烷基和硫氧基吸电子基团降低了它们与MnO₂的反应活性。MnO₂氧化双酚类有机物首先发生一电子转移产生酚氧自由基中间态,其进一步被氧化最终生成羟基化产物、碳碳或碳氧聚合产物以及断键氧化产物。I^-对MnO₂氧化双酚类有机物效能的影响与HOI暴露量密切相关。HOI暴露量越大,I^-对MnO₂氧化双酚类有机物效能的促进作用越明显;而HOI暴露量与溶液p H、有机物结构有关。双酚A与MnO₂反应活性高于I^-,体系中HOI暴露量低,在p H值为5.0-9.0范围内I^-对MnO₂氧化双酚A效能无明显影响。双酚AF和双酚S与MnO₂反应活性低于I^-,体系中HOI暴露量高,p H值为5.0-7.0条件下I^-明显促进MnO₂氧化它们的效能。而在p H值7.0-9.0范围内,MnO₂氧化能力较弱,难以氧化I^-,此时I^-对MnO₂氧化双酚AF和双酚S的效能无明显影响。I^-存在时,MnO₂氧化双酚AF和双酚S的过程中检测到多种碘代芳香类有机物,主要是HOI与双酚AF和双酚S或者它们的氧化产物发生一次或多次亲电取代而产生。生成的碘代芳香类有机物可进一步被MnO₂或HOI转化。PMS与I^-和HOI表现出极高的反应活性。实验结果表明,中性p H条件下,PMS氧化I^-的二级反应速率常数达1.1×10³ M^-1s^-1,远高于KMnO₄氧化I^-的速率(6.9 M^-1s^-1)。在p H值5.0-10.0范围内,PMS氧化HOI的二级反应速率仅次于臭氧且远高于KMnO₄,在p H值为10.0时高达7.9×10⁴ M^-1s^-1。碘形态质量守恒分析表明PMS氧化HOI最终生成稳定、无毒的碘酸盐（IO₃^-）。模型天然有机物和I^-共同存在时,PMS氧化体系中生成一定量的总碘代有机物和小分子碘代有机物（如碘仿和一碘乙酸）,并且其生产量随着p H升高而降低。相同条件下,PMS氧化体系中碘仿和一碘乙酸生成量均低于液氯和氯胺消毒体系中的生成量,主要由于PMS氧化体系中HOI暴露量较低。实验室配水和实际水体中,PMS的加入均显著降低了I^-对KMnO₄氧化尼泊金酯的促进作用,并且大大减少了体系中碘代芳香类有机物的生成量。PMS浓度越高或p H越高,其对KMnO₄氧化尼泊金酯过程中碘代芳香类有机物生成的抑制作用越明显,而相应的IO₃^-生成量越高。实验结果表明,PMS也可有效抑制MnO₂氧化尼泊金酯过程中碘代芳香类有机物的生成。更多还原

【Abstract】 Iodinated aromatic organics are important precursors of small molecular iodinated organics（e.g.,iodoform and mono-iodoacetic acid）with their toxicity generally higher than aliphatic organics as well as their chlorinated and brominated analogues.Formation of iodinated aromatic organics in water treatment processes shows great impact on water quality and safety.Hence,it has received significant scientific attention.Manganese oxidants（i.e.,permanganate（KMnO₄））and manganese dioxide（MnO₂）)are relatively stable and commercially cheap,and they have been widely used to remove organic and inorganic pollutants in aqueous environment.However,studies show that small molecular iodinated organics are generated during KMnO₄ and MnO₂ treatment of iodide（I^-）-containing waters,which significantly hinders their further application in water treatment.Yet,information on formation mechanism and regulation strategy of iodinated aromatic organics during KMnO₄ and MnO₂ oxidation remains unclear at present.In this work,phenolic compounds with different structures were selected.Formation mechaniusm of iodinated aromatic organic products during treatment of I^--containing waters by KMnO₄ and MnO₂ was studied.Moreover,regulation strategy of using chemical oxidant peroxymonosulfate to control formation of iodinated aromatic organic products was also proposed.Impact of I^-on transformation efficiency of various phenolic compounds by KMnO₄ were first explored,along with discussions on related mechanisms.The experimental results showed that:Kinetic modeling using Me P as a model phenolic compound could well fit its transformation by KMnO₄ under various conditions,suggesting that hypoiodous acid（HOI）played a key role in phenolic compounds transformation by KMnO₄in the presence of I^-.The higher the HOI exposures,the stronger the accelerating impact of I^-on transformation of phenolic compounds.HOI exposure is related to the structure of phenolic compounds:Phenolic compounds with electron-donating moieties（e.g.,bisphenol A and triclosan）have high reactivity with KMnO_4,thus a low HOI exposure was maintained in the system.In contrast,phenolic compounds with electron-withdrawing moieties（e.g.,bisphenol S and methylparaben）have low reactivity with KMnO₄,therefore a high HOI exposure was maintained in the system.Iodinated aromatic organic products were generated along with the accelerated transformation of phenolic compounds by KMnO₄ in the presence of I^-.Electrophilic substitution of HOI on phenolic compounds by one-or multi-steps resulted in their formation.Generally,higher I-Ar Ogs concentrations were obtained in higher HOI exposure.Oxidation efficiency of the three selected bisphenols by MnO₂ follows the order of bisphenol A>bisphenol AF>>bisphenol S under similar conditions,mainly resulting from the differences in their structures.The electron-donating alkyl moiety in bisphenol A enhanced its reaction with MnO₂,while the electron-withdrawing fluoro-alkyl group in bisphenol AF and thio-oxygen group in bisphenol S reduced their reactivities with MnO₂.Phenoxyl radicals were initially formed from MnO₂ oxidation of bisphenols via one-electron transfer,and they could be further oxidized to hydroxylated,carbon-carbon or carbon-oxygen polymeric,and bond-cleavage products.Impact of I^-on bisphenols oxidation by MnO₂ were closely related to HOI exposures.The higher HOI exposure,the stronger the accelerating effect of I^-.HOI exposure is determined by structure of phenolic compounds and solution p H.bisphenol A has a high reactivity towards MnO₂ than I^-,therefore lower HOI exposure was obtained in the system.I^-has slight impact on bisphenol A oxidation by MnO₂ at p H 5.0-9.0.Bisphenol AF and bisphenol S have lower reactivity towards than I^-,resulting in higher HOI exposure.Therefore,I^-obviously enhanced bisphenol AF and bisphenol S oxidation by MnO₂ at p H 5.0-7.0.At p H 7.0-9.0,MnO₂ cannot oxidize I^-due to its decreased oxidative ability,wherein I^-showed slight impact on bisphenol AF and bisphenol S oxidation by MnO ₂.Iodinated aromatic organic products were additionally generated from MnO ₂ oxidation of bisphenol AF and bisphenol S in the presence of I^-,mainly resulting from the one-or multi-steps electrophilic substitution reactions of HOI with bisphenols and/or their oxidation products.Peroxymonosulfate（PMS）showed high reactivities towards both I^-and HOI.The apparent second-order rate constants of PMS reaction with I^-was up to 1.1×10³M^-1s^-1 at neutral p H,which was much higher that of KMnO₄ with I^-(6.9 M^-1s^-1).The apparent second-order rate constant for PMS with HOI was only second to ozone but higher than KMnO₄ in the p H range of 5.0-10.0 with its value reaching around 7.9×10⁴ M^-1s^-1 at p H 10.0.The iodine mass balance analysis showed that HOI was oxidized to iodate（IO₃^-）,a stable and non-toxic sink of iodine,by PMS.Total organic iodine and iodinated organics with small molecular weight（e.g.,iodoform and monoiodoacetic acid）were formed during PMS oxidation in the co-presence of natural organic matter and I^-with their concentration decreasing with increasing p H.Formation of iodoform,and monoiodoacetic acid during PMS oxidation of model natural organic matters in the presence of I^-was lower than those formed during chlorination and chloramination processes under similar conditions,mainly due to lower HOI exposures in PMS system.Addition of PMS remarkably reduced the accelerating effect of I^-on methylparaben transformation by KMnO₄ as well as formation of iodinated aromatic organic products in both synthetic and authentic waters.Stronger inhibitive effect of PMS on iodinated aromatic organic products formation during KMnO₄ oxidation of methylparaben in the presence of I^-were obtained at higher PMS dosage or p H,meanwhile higher levels of IO₃^-was formed.Similar inhibitive effect of PMS on formation of iodinated aromatic organic products during MnO₂ oxidation of methylparaben were also observed.更多还原