【作者】 陈晴空；

【导师】 吉芳英；

【作者基本信息】 重庆大学 ， 环境科学与工程， 2014， 博士

【摘要】 近年来，随着我国环保、能源等相关政策和法规的逐步建立和完善，对工业用水的回用率提出了较高要求。水回用率提高虽然有效节约了水资源，降低了生产成本，但也使水中的有机物逐渐累积，导致排出的有机废水具有成分复杂、高浓度、高生物毒性和生物难降解的特点，传统生物水处理工艺难以对其进行有效处理。高级氧化技法（AOPs）被认为是处理高浓度难降解有机废水的有效途径，能彻底将水中有机污染物分解成无害的CO2和H2O。其中，基于Fe2+和H2O2构成的Fenton反应和TiO2光催化氧化技术理论上能在常温、常压下反应，反应速率快且操作简单，非常适合于工业有机废水处理。但在实际工程中，由于Fe2+在pH＞3.7时易被氧化并生成Fe（OH）3沉淀，Fenton反应需要投加过量含Fe2+药剂来保证对H2O2的催化，确保污染物的降解。虽然Fe（OH）3有一定絮凝作用，但会产生大量化学污泥，造成二次污染；而TiO2光催化反应则需足够强度的紫外光源保证TiO2被有效激发，对光穿透能力差、色度较大的有机废水处理效果较差，大量纳米TiO2粉末状催化剂易因团聚而不能和污染物分子进行有效反应，且难以从水中去除和回收，也易造成催化剂浪费和二次污染。因此，往往需要配备辅助设施才能适应不同水质，保证工艺有效运行和处理效果，导致技术成本较高。论文的主要研究内容与结论如下：①针对上述技术瓶颈，作者创新性地设计并使用溶胶-凝胶法合成了一种“双效催化剂”—Co-TiO2。“双效”是指在近中性条件下（pH=6.9），Co-TiO2能在无光环境下催化PMS（KHSO5）发生基于硫酸根自由基（SO₄·^-）的类Fenton催化氧化反应（Co-TiO2/PMS，SR-Fenton）；同时，还能在光照条件下作为光催化剂，通过光催化氧化（Photo/Co-TiO2，Photo）去除水中的有机污染物。试验结果表明：pH=6.9时， Co-TiO2/PMS反应对50mg/L的罗丹明B（RhB）和苯酚（PhOH）的降解率为77.5%和64.9%。可见光（Vis）照射下，Vis/Co-TiO2反应光催化降解RhB和PhOH，降解率分别为45.6%和52.3%。当Vis、Co-TiO2和PMS同时存在于反应体系中时，SR-Fenton和光催化形成了协同催化氧化体系。基于此，作者融合SR-Fenton和TiO2光催化过程开发了一种新型“SR-Fenton/光催化协同技术（Vis/Co-TiO2/PMS，SR-Fenton/Photo）”。试验表明，相同条件下，Vis/Co-TiO2/PMS体系对RhB和PhOH的降解率（ηD）都上升为100%，反应时间由2h缩短到80min。根据Vis/Co-TiO2/PMS反应对100mg/L的RhB和PhOH的ηD计算出体系中SR-Fenton和TiO2光催化的协同效率（ηSyn）分别为15.7%和12.6%。此外，Co-TiO2的重复利用性好，Co2+离子溶出率（ηLCo2+）仅为1.4%。同时，Co-TiO2有一定的铁磁性，具有磁力回收的潜力。②本文对Co-TiO2/PMS、Vis/Co-TiO2和Vis/Co-TiO2/PMS为对比体系进行了研究，以探讨Co-TiO2的催化机理和SR-Fenton/光催化的协同机制：1)针对Co-TiO2/PMS反应体系，通过XPS和UV-DRS检测表明Co-TiO2催化剂表面有Co3O4颗粒。自由基淬灭试验结果显示Co-TiO2/PMS体系中主要自由基种类是SO₄·^-，结合原位ATR-FTIR分析确定Co3O4颗粒是Co-TiO2催化剂的SR-Fenton活性点位。以草酸盐定量法测得1.0g Co-TiO2可催化1mol PMS产生1molSO4。针对Vis/Co-TiO2反应体系，XRD测试结果表明一部分Co2+离子掺入了TiO2晶格。基于第一性原理计算并结合UV-DRS、VBXPS测试确定Co-TiO2催化剂的Eg=2.30eV，EVBT=2.0eV，ECBB=-0.3eV，是窄带系半导体，能有效利用可见光，Co-TiO2的可见光活性主要来源于Co2+的掺杂。同时，EEM测试表明Co2+掺杂降低了光生电子-空穴对（hvb+/ecb）的复合率，增强了Co-TiO2的光催化活性。2)对Co-TiO2催化剂Co元素XPS图谱的研究发现Vis/Co-TiO2/PMS协同反应前后Co-TiO2催化剂表面Co3O4颗粒中的Co（II）比例由33%上升到46%；而Co-TiO2/PMS反应前后Co3O4中的Co（II）却由33%下降到12%。可能是光催化产生的强还原性电子将Co3O4中的部分Co（III）还原成了Co（II），提高了SR-Fenton催化效率。同时，PMS能有效提高光催化过程的表观量子产率（ΦApp），加入PMS后，UV/TiO2反应的ΦApp由0.0074增大到0.073μmol/J，可推知PMS能捕获光生电子（ecb）。SR-Fenton和光催化效率的提高，都增强了体系的氧化能力。通过自由基淬灭法发现pH=6.9时，Vis/Co-TiO2/PMS反应为OH和SO₄·^-自由基的混合体系，自由基总量比Co-TiO2/PMS体系上升34%。3)利用GC/MS、LC/MS跟踪RhB在Vis/Co-TiO2/PMS反应中的主要降解中的浓度，发现它们的生成量大于Co-TiO2/PMS和Vis/Co-TiO2反应，生成速率也较快。准一级动力学方程能较好拟合三种反应过程。协同作用在反应动力学上的表现为Vis/Co-TiO2/PMS反应的表观速率常数（kobs）（0.01399min-1）比Vis/Co-TiO2（0.00161min-1）和Co-TiO2/PMS反应（0.0699min-1）增大了一个数量级；同时，表观活化能（E Appa）由Co-TiO2/PMS反应的51.3kJ/mol下降到Vis/Co-TiO2/PMS的39.5kJ/mol。基于kobs计算协同系数（Sc）为1.8。③最后，将Vis/Co-TiO2/PMS协同体系用于去除水中的微量POPs/EDCs物质阿特拉津和PAHs物质萘和菲。结果表明阿特拉津能被Vis/Co-TiO2/PMS体系有效降解，部分有毒中间产物也被完全去除。当以Vis为光源，[ATZ]0=0.1mM、mcata=0.01g、PMS/[ATZ]0=1:2、pH=6.9时，反应50min，ATZ即被完全降解，反应协同效率（ηSyn）和协同系数（Sc）分别达37%和5.30。萘和菲也能被协同体系快速去除，水中的NOM物质对它们降解率影响不明显。对比类似研究，Vis/Co-TiO2/PMS协同体系有效节省了药剂投加量、反应时间短、降低了技术成本。因此，论文合成的Co-TiO2双效催化剂和构建的SR-Fenton/Photo协同催化氧化体系部分解决了传统Fenton催化依赖酸性反应环境、药剂投加量大、含铁化学污泥以及TiO2光催化依赖紫外光源和催化剂难回收的问题。更多还原

【Abstract】 Recent years, with the gradual establishment and improvement of environmentaland energy-related policies and regulations in China, the industrial water has beenrequired to have a higher recycling rate. Although the increasing of the water reusesaves the water resources and reduce production costs effectively, but also causes theaccumulation of organic matter in the water. So, the high concentration of varioustoxicity and refractory organic pollutants were usually rich in the industrial wastewater,and the traditional biological waste water treatment process is difficult to remove themeffectively. But, the advanced oxidation processes （AOPs） are considered to be aneffective way to deal with them, it can completely decompose the organic pollutantsinto harmless CO2and H2O. Among different AOPs, the Fenton reaction （Fe2+/H2O2）and TiO2photocatalytic oxidation technology are best suited to the industrial organicwastewater treatment as they can react at room temperature and atmospheric pressure,furthermore, their reaction rates are fast and the operation conditions are simple,theoretically. Actually, Fenton reaction requires excessive dose of Fe2+to catalyze H2O2decomposition to ensure the degradation of pollutants, because the Fe2+ions will beoxidized and precipitated in the form of Fe（OH）3at pH>3.7. The large quantities ofchemical ferric sludge will cause secondary pollution, in spite of Fe（OH）3has someflocculating effect. On the other hand, the TiO2photocatalysis is required sufficientintensity UV as light source. In the case of some dark color wastewater, the lightpenetration is weak, the treatment effect is poor. Furthermore, a large number ofnano-TiO2powders are not react with pollutant molecules effectively as reunited. Also,the suspended nano powders are difficult to remove from the water by filtration or othermethods, and it also lead to secondary pollution, easily. Therefore, in practicalengineering Fenton and TiO2photocatalysis need auxiliary facilities to adapt to differentwater quality and ensure the effective operation of the processes, and the treatmenteffect, so resulting in higher technology costs.The main contents and conclusions of the paper are as follows:①In order to overcome these technological bottlenecks, the authors innovativelydesigned and synthesized a “bifunctional catalyst”-Co-TiO2by using sol-gel method.“Bifunctional” means: When pH=6.9, the Co-TiO2catalyst can initiate SR-Fentonreaction via catalyzed PMS （KHSO5） to produce sulfate radicals （SO4） in dark （Co-TiO2/PMS, SR-Fenton） or exited by light （Photo/Co-TiO2, Photo） as photocatalyticcatalyst, respectively. Therefore, Co-TiO2catalyst is able to be applied in both dark andbright environments to removal organic pollutants in water flexibly. The results showthat: within2h reaction time, the degradation rates of50mg/L of rhodamine B （RhB）and phenol （PhOH） were77.5%and64.9%, respectively, in Co-TiO2/PMS process, atpH=6.9. At the same time, under visible （Vis） irradiation, the RhB and PhOHphotocatalytic degradation rate were45.6%and52.3%by Vis/Co-TiO2process.When the light, Co-TiO2and PMS coexist in the reaction system, SR-Fenton andphotocatalysis formed a synergistic oxidation system. Based on this, the authors hasdeveloped a novel “SR-Fenton/photocatalytic synergistic oxidation technology（Vis/Co-TiO2/PMS, SR-Fenton/Photo）” which integrated SR-Fenton and TiO2photocatalytic process in a heterogeneous catalytic system. Tests showed that under thesame conditions, degradation rate of RhB and PhOH （ηD） both increased to100%inVis/Co-TiO2/PMS system, and the reaction time reduced to80min. Calculation ofsynergistic coefficient （ηSyn） of SR-Fenton and TiO2photocatalysis based on the ηDof100mg/L RhB and PhOH degradation in Vis/Co-TiO2/PMS process were15.7%and12.6%. In addition, Co-TiO2showed good reusability and the Co2+ions leaching rate（ηLCo2+） was only1.4%. Magnetic test indicated that the Co-TiO2catalysts hasferromagnetic, so it has potential to recovery by magnetic force.②To analyze the catalytic mechanism of Co-TiO2in the SR-Fenton/Photosynergistic system, this paper used Co-TiO2/PMS, Vis/Co-TiO2and Vis/Co-TiO2/PMSas comparison system:1) In the study of the Co-TiO2/PMS process, the UV-DRS and XPS spectra showedthe Co3O4particles loaded on the surface of Co-TiO2catalyst. The radical quenchingtest showed theSO₄·^-was the main radical specie of Co-TiO2/PMS reaction, and thein-situ ATR-FTIR analysis determined the Co3O4particles were the SR-Fenton activesites of Co-TiO2catalyst. Using oxalate to quantify the radicals in the reaction madesure that1.0g Co-TiO2can catalyze1mol PMS to produce1molSO₄·^-. In the study ofVis/Co-TiO2process, the XRD spectra showed that a part of the Co2+ions has implantedinto the TiO2lattice.Based on first-principles calculation and UV-DRS, VBXPS tests,the Eg, EVBT, and ECBBwere2.30,2.0, and-0.3eV. So, it is a narrow-band semiconductor,can utilize visible light effectively. The visible light photocatalytic activity of Co-TiO2might be attributed to the Co2+ions doping. Meanwhile, EEM tests showed that theCo2+-doping also reduced the combination of photo-generated electron-hole pairs （hvb+/ecb）, and enhanced photocatalytic activity of Co-TiO2.2) From the Co XPS spectra of the fresh and spent Co-TiO2catalyst ofVis/Co-TiO2/PMS reaction, the Co（II） proportion of Co3O4particles, loaded on thesurface of Co-TiO2catalyst, rose from33%to46%; while it dropped from33%to12%in the Co-TiO2/PMS reaction. This results told us the strong reductive photo generatedelectrons from photocatalytic reaction reduced a part of Co（III） in Co3O4to Co（II）, andthe higher Co（II） amount improved the SR-Fenton catalytic efficiency. Meanwhile, thetrial also showed that PMS can effectively improve the apparent quantum yield （ΦApp）of TiO2photocatalytic process. After adding PMS to the UV/TiO2process, ΦAppofUV/TiO2reaction increases from0.0074to0.073μmol/J, and it can be inferred that thePMS can capture the photo-excited electrons. The enhancement of SR-Fenton andphotocatalysis of synergistic system improved the oxidizing ability of Vis/Co-TiO2/PMSreaction obviously. Using the radical quenching method to recognize the radicals inVis/Co-TiO2/PMS process, it can be found that when pH=6.9, OH andSO₄·^-both existin the hybrid system, and the radical total amount was34%more than the Co-TiO2/PMSreaction.3)Based on the results of GC/MS, LC/MS and quantity of major intermediates ofRhB degradation, we can found that the amount of by-products in the Vis/Co-TiO2/PMSprocess was greater than individual Co-TiO2/PMS or Vis/Co-TiO2reaction and theirgeneration rate was faster. The RhB degradation kinetics of Co-TiO2/PMS, Vis/Co-TiO2and Vis/Co-TiO2/PMS all fitted quasi-first-order kinetics well. The synergistic effectreflected in the reaction kinetics was that the apparent rate constants （kobs） ofVis/Co-TiO2/PMS （0.01399min-1） was one magnitude bigger than Vis/Co-TiO2（0.00161min-1） and Co-TiO2/PMS reaction （0.0699min-1）. Meanwhile, comparing withCo-TiO2/PMS the apparent activation energy （EAppa） was decreased from51.3kJ/mol to39.5kJ/mol. The synergistic coefficient calculated based kobs（Sc） was1.8.③Finally, the author using Vis/Co-TiO2/PMS synergistic system to remove thetrace POPs/EDCs substance atrazine and PAHs substance naphthalene and phenanthrene.Results indicated that the atrazine can be degrade effectively and some toxicintermediates are also completely removed. The reaction conditions were as follows:visible light source,[ATZ]0=0.1mM, mcata=0.01g, PMS/[ATZ]0=1:2, pH=6.9,50minreaction time. The synergistic efficiency （ηSyn） was37%and the synergistic coefficient（Sc） was5.30, respectively. Furthermore, the trace naphthalene and phenanthrene alsocan be rapid removal by the synergistic process, and their removal rates were not affected by NOM in water obviously. Compared with the similar studies, theVis/Co-TiO2/PMS synergistic system effectively saves the pharmaceutical dosageeffectively, furthermore, it also shorten the reaction time and reduce technology costs.Consequently, the Co-TiO2bifunctional catalyst and the synergisticSR-Fenton/Photo system build in this study partially overcome the drawbacks of acidicpH environment, large pharmaceutical dosage, and chemical sludge of traditionalFenton, as well as, ultraviolet light source dependence and catalyst recovery problem ofTiO2photocatalysis.更多还原