【作者】 袁磊；

【导师】 陈忠林；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2013， 博士

【摘要】 随工业迅猛发展和人类物质生活水平的提高，水环境污染已成为目前普遍关注的问题。水中的一些难降解有毒有害污染物，虽然浓度低，但危害大、去除难，传统给水处理工艺不能有效地去除这些有毒有害微污染物，直接威胁城镇供水水质安全。非均相催化臭氧氧化技术，因其高效氧化性能、催化剂易分离、处理成本低、工艺简单等特点，已成为当前研究热点。本文即是从提高浮石催化活性这一关键环节入手，制备浮石基过渡金属羟基化物催化剂的基础上，研究浮石和所制备的复合催化剂催化臭氧氧化去除水中难降解有机物，获得新型催化臭氧氧化技术。探讨催化剂微观结构、表面特性与催化活性之间的内在规律。该类催化剂具有来源易得、生产成本低和制备简单等优点，具有良好市场应用前景。浮石作为催化剂催化臭氧氧化水中对氯硝基苯(pCNB)表现了较强的催化活性，与单独臭氧氧化工艺比较，浮石催化臭氧氧化工艺对水中pCNB和总有机碳(TOC)去除率明显提高，浮石与臭氧降解水中pCNB具有协同作用，浮石吸附pCNB能力很弱。实验中成功制备了浮石基羟基化锌(ZnOOH/浮石)催化剂，材料对气体具有一定的吸附能力和吸附容量，检测发现，表面含有丰富的表面羟基。ZnOOH/浮石具有明显的催化能力，催化臭氧氧化pCNB的去除率由臭氧氧化时的55.7%提高至93.4%，比浮石催化臭氧氧化pCNB去除率提高21个百分点。ZnOOH/浮石对pCNB的吸附能力比浮石有所增强。考察了ZnOOH/浮石催化臭氧氧化水中pCNB的效能和影响参数，结果表明，pCNB的去除率与臭氧浓度、催化剂投量、反应温度和pCNB初始浓度呈正相关；随着水纯净度的降低，pCNB的去除率升高；水体中Ca2+、Mg2+、Cl-、NO-3、K+和Na+对ZnOOH/浮石催化臭氧氧化pCNB的去除率影响可以忽略不计，SO2-具有一定的表面络合能力，使浮石的催化活性下降，4ZnOOH/PO3-4可以显著抑制ZnOOH/浮石的催化活性；CO2-3/HCO-3碱度对催化臭氧氧化pCNB的去除率有明显影响，高碱度明显降低了pCNB的去除率；随着反应体系中腐殖酸浓度的增加，催化臭氧化pCNB的去除率先增后降；ZnOOH/浮石随着焙烧温度的升高其催化活性降低；催化剂重复使用后，pCNB的去除率稳定，保持良好的催化活性。反应过程中体系有微量的离子溶出，但均低于国标限值。浮石和ZnOOH/浮石的引入均可明显加快臭氧的分解速度，分别使水中臭氧的分解速率常数提高了1.19和2.84倍，在2种催化反应体系中均检测到了·OH的产生。叔丁醇可以大幅度的抑制催化反应中pCNB的降解，证明催化臭氧氧化工艺中pCNB的氧化是以·OH为主、O3为辅的氧化反应。催化剂在溶液pH≈pHpzc时催化活性最强，表明-OH状态的表面可以引发臭氧分解生成·OH。催化剂表面羟基是分解水中臭氧的活性位，具有较高催化活性的催化剂通常有较大的表面羟基密度。催化剂表面活性羟基吸附水中的臭氧进而发生链式分解反应，反应过程中有高氧化性的·OH生成。更多还原

【Abstract】 Industrial development and the improvement of living conditions have resulted in the extensive pollution of the water environment. Despite having low concentrations in water, some refractory organic pollutantshave serious harmful effects.However, conventional processes have beenshown to achieve very limited mineralization of organic micropollutants indrinking water treatment. Heterogeneous catalytic ozonation, asa promising advanced oxidation process, has recently receivedconsiderable attention in the field of water treatment for its high oxidationpotential.To provide active sites on catalystsand to improve ozone decomposition, pumice and ZnOOH/pumice were prepared in a laboratory and used as catalysts in this paper. Catalysts were applied in the catalytic oxidation of race concentrationsof p-chloronitrobenzene (pCNB). The relationshipamong the catalyst structure,surface hydroxyl, and catalytic activity in catalytic ozonationwas then determined. The catalysts, whichwere readily available, inexpensive, and easy to prepare, exhibit promising application potential for drinking water treatment.The use of pumice for heterogeneous catalytic ozonation significantly enhancesthe degradation efficiency and total organic carbon(TOC) removal of pCNB in an aqueous solution compared with ozonation alone because of the synergistic effect between ozone and the catalyst. The pCNB adsorption was insufficient to contribute significantly to the pCNB degradation during pumice-catalyzed ozonation.The catalyst prepared in the laboratory was pumice-supportedzinchydroxide(ZnOOH-pumice). Materials havea certain capability for the adsorption of gas.Experimental results show that the main functional group on the catalyst surface was hydroxyl.All hydroxidespossess abundant surface hydroxyl groups. At a reactiontime of20min during the catalytic removal of pCNB by ozonation alone, pumice/ozonation and ZnOOH-pumice/ozonation in distilled water increase from55.7%to72%and93%, respectively. In contrast to the experimental results of ozonation aloneand of catalytic ozonation processes, the adsorption of pCNB ontoZnOOH-pumice is insufficient to make a significant contribution to degradation efficiency and can therefore be neglected.The affecting factors of the catalytic ozonation of pCNB by ZnOOH-pumice were investigated. Results show that the removal of pCNB increased with the reaction temperature, ozone concentration,and initial concentration ofthe pCNB and catalyst, along with decreasing water purity. The effects of NO-3, Na+, and K+on the catalytic ozonation of pCNB can be ignored. Degradationefficiencywas slightly promoted in the presence of Ca2+and Mg2+. The ozonation of pCNBwas slightly inhibited by the high concentration of Cl-. Theremoval efficiency of pCNBdecreased in the presence of SO2-4, given that the hydroxyl inhibitors PO3-4and HCO-3can significantlyinhibit the catalytic degradation ofpCNB.The removal of pCNB decreased with increasing humic acidconcentration.The catalytic capability of the catalyst weakened with increasing calcinationtemperature. After10successive recycles, the catalyst remainedstable during the catalytic ozonation of pCNB.Ion dissolution was observed after catalyzed ozonation. How ver, the concentration of the residual ions was negligible. The concentrationof residual ionswas lower than the drinkingwater criterion in China.Pumice and ZnOOH-pumice significantly accelerate the decomposition of ozone in water.The rate constant of ozone decomposition increased by1.19times and2.84times when using pumice and ZnOOH-pumice, respectively.When pumiceand ZnOOH-pumice catalyzed ozone, higher·OH concentrations were generated under the same experimental conditions compared with those obtained from ozonealone. Tert-butanol significantly inhibited the degradation of pCNB in these three catalytic reaction systems.Enhancements of hydroxyl free radicals were achieved during catalyzed ozone decompositionusing pumice and ZnOOH-pumice. Thus,the catalytic oxidation of pCNB can be divided into two parts: main reaction withhydroxyl radicals and accessorial oxidation by ozone molecules. High pH also positively affected pumice-catalyzed ozonation,given that nearly uncharged surfaces (solution pH was close to the point of zero charge) are favorable for catalytic pCNB ozonation.The results of this study indicatethat hydrous oxide sites present on catalyst surface (S-OH) serve a key function in the catalytic ozonation mechanism.Surface hydroxyl groups were revealed to be important ctive sites onthe catalyst. Hydroxides, which show high catalytic activityduring ozone decomposition, possess abundant surface hydroxyl groups. Structuralhydroxyls or hydroxylsformed through the adsorption of hydrogen ions in waterare capable of catalyzing ozone decomposition. Ozone molecules in water can be adsorbed on these active hydroxyls, consequently promoting ozone decomposition with the production of·OH.更多还原