【作者】 李炳智；

【导师】 徐向阳；

【作者基本信息】 浙江大学 ， 环境工程， 2010， 博士

【摘要】 氯代硝基苯（ClNBs）是一大类含氯含硝基芳香烃化合物,广泛用作医药、染料、农药生产的中间体,同时也是美国EPA、欧共体及中国优先控制的持久性有毒难降解有机污染物。由于ClNBs长期的大规模生产和应用,致使我国许多河流、湖泊、农田甚至地下水均受到不同程度的污染,对人体健康和水环境安全构成了严重威胁,为此开发高效经济的废水处理和污染修复创新工艺十分迫切。本论文以臭氧化和催化臭氧化技术为手段,以ClNBs及其生产废水为研究对象,开展了臭氧化、催化臭氧化降解ClNBs,催化臭氧化一生物降解耦合工艺处理高浓度ClNBs生产废水等相关研究,取得了如下研究结果:1、以邻、间、对氯硝基苯（o-ClNB、m-ClNB和p-ClNB）为目标污染物,通过研究pH和气体流速对臭氧质量传递系数的影响确立ClNBs稳态臭氧化条件,进而开展污染物初始浓度、自由基猝灭剂（TBA）等关键因子对臭氧化系统ClNBs去除效率的影响研究,以期揭示臭氧化体系去除水中ClNBs类难降解有机物的稳态动力学及机理。实验结果表明,ClNBs的降解遵循准一级反应动力学,其速率常数随pH的升高而增加,随初始污染物和自由基猝灭剂浓度的增加而下降;ClNBs的去除速率速率依次为:o-ClNB＜m-ClNB＜p-ClNB,并与臭氧反应的剂量比均为1:1。动力学分析发现,o-ClNB、m-ClNB和p-ClNB与O₃直接反应速率常数（k_D）分别为6.342×10^-3、3.890×10^-2、6.442×10^-2L·mol^-1·s^-1,与羟基自由基反应的间接速率常数(K_OH)分别为2.037×10⁹、2.398×10⁹、3.869×10⁹L·mol^-1·s^-1;pH≥7时,ClNBs臭氧化95%以上为·OH贡献。利用GC-MS、LC-MS对三种ClNBs的臭氧化中间产物分析发现,产物主要分为酚类物质和开环的脂肪族化合物,推测ClNBs臭氧化降解途径可能为:·OH通过亲电反应取代苯环上的氯基、硝基或氢原子,形成芳环自由基进而氧化为酚类物质,进一步脱氯、脱硝基或氢被夺去生成多羟基的取代酚后再开环（或直接发生苯环开环）,最终转化为小分子的醛、酮和羧酸等化合物。由于氯和硝基取代位置的不同,导致苯环上碳原子的电子云密度具有一定的差异,研究发现p-ClNB在臭氧化过程中氯基和硝基可以被·OH取代生成硝基酚和氯酚,而在o、m-ClNB的氧化产物中未检出硝基酚和氯酚,三种ClNBs苯环上的氢均可被·OH取代,生成硝基氯酚,·OH与苯环上H发生取代反应的几率与相应碳原子的电子云密度具有一定的相关性。2、比较了七种金属离子及其组合均相催化臭氧化降解ClNBs的效能,通过研究pH值、金属离子投量和羟基自由基猝灭剂对ClNBs臭氧化去除性能、有效臭氧消耗量的影响,优选高效强化臭氧化效率的金属离子并推测可能的催化机理。实验结果表明,金属离子的投加均可强化臭氧化系统ClNBs的去除速率及矿化程度。单一离子系统中增加金属的投量可以提高ClNBs的去除速率,然而金属离子浓度超过一定范围污染物去除速率不再增加;在单一金属离子投量为0.4mM、pH 2.0时,强化因子顺序为:Co²⁺≥V⁴⁺＞Fe²⁺≥Fe³⁺≥Zn²⁺≥Ni²⁺＞Mn²⁺,反应介质pH的改变对金属离子强化臭氧化系统性能的影响较大;在组合离子臭氧化系统中,Mn²⁺、V⁴⁺离子共存对ClNBs臭氧化去除存在抑制作用;通过比较污染物降解过程臭氧消耗情况发现,O₃/Mn^<sup>2+-C²⁺双金属催化臭氧化系统具有较好的ClNBs去除特性。同时,TBA明显抑制ClNBs的去除,表明均相催化臭氧化系统中ClNBs的去除机制以自由基反应为主。3、以硅藻土为载体制备锰氧化物（MnO_x）和钴氧化物（CoO_x）复合金属催化剂,研究了其对硝基苯（NB）和p-ClNB臭氧化的催化特性,应用SEM、XRD、FTIR和XPS等技术对催化剂进行了表征。结果表明,活性组分摩尔比、焙烧温度和焙烧时间对催化剂的催化性能影响显著;FTIR分析显示催化剂富含表面羟基,且负载金属以多种价态存在于催化剂表面;XRD和XPS结果进一步揭示负载金属以二价、三价和四价的氧化物形式分布于催化剂表面。与单独臭氧化体系相比,pH 3.0和pH 7.0时投加1g/LMn/Co负载硅藻土催化剂后污染物矿化率分别增加46～57%和35～40%;催化臭氧化显著提高了主要羟基芳香族中间产物、Cl^-和NO₃^-的形成以及小分子羧酸LMWCA（乙酸、草酸）的氧化速率,同时反应体系中还检测到低浓度H₂O₂;加入TBA后明显抑制了催化臭氧化反应的进行,EPR捕获实验检测出·OH捕获剂5,5-二甲基1-吡咯啉N-氧化物（DMPO）和·OH加合物的1:2:2:1特征信号,说明催化反应体系存在·OH,且产生的·OH浓度比单独臭氧化体系高,为此我们提出了催化臭氧化强化目标污染物去除的协同作用机理。4、以多孔硅藻土基陶瓷填料为载体制备了一体化Mn/Co非均相催化剂,比较了单独臭氧氧化、多孔填料/臭氧及改性多孔填料/臭氧三种工艺处理氯代硝基苯生产废水的性能。实验结果表明,加入多孔填料和Mn/Co改性的多孔填料提高了臭氧氧化生产废水TOC和COD去除速率,前者TOC、COD去除分别增加2～11%和2.5～24%,而后者对生产废水TOC、COD去除的促进作用最为明显,分别增加35%和38%。通过填料改性能够提高填料本身的催化活性,进而强化臭氧氧化生产废水的处理效能。废水经过120min的催化臭氧化处理,色度得到基本脱除,可生化性明显改善（BOD₅/COD从0.02增至0.5左右）,发光细菌急性毒性降低约25倍。从这个角度而言,催化臭氧化与生物处理工艺耦合处理此类废水是可行的。5、比较研究了单一生物和催化臭氧化（COP）/生物耦合工艺处理氯代硝基芳烃（CNACs）生产废水的性能。实验结果表明,单一生物处理可以去除生产废水中的主要污染物,但由于其色度、氨氮、TOC和COD去除效果差,处理出水难以达标;Mn/Co改性陶瓷催化剂催化臭氧氧化生产废水的试验发现,废水色度有效降低,可生化性明显提高,且催化剂经过70次的重复使用后仍保持较高活性,显示其良好的长效性和稳定性。设计了催化臭氧化-生物耦合工艺,进水COD 2840-3120mg/L、催化臭氧化停留时间1h、SBR停留时间10h条件下稳定运行一个月,出水平均氨氮、COD、BOD₅、TOC浓度和色度去除率分别为80%、95.8%、93.8%、97.6%和99.3%,出水氨氮、COD、BOD₅和色度分别为10mg/L、128mg/L、27.5mg/L和20倍。结果揭示构建的耦合系统是一种有应用前景、适于处理含难降解CNACs生产废水的经济、高效工艺。更多还原

【Abstract】 Chloronitrobenzenes（ClNBs）,as a large class of aromatic compounds that contain chloro- and nitro- groups,are widely used as intermediates for the chemical synthesis of medicines,dyes and pesticides,and are also declared to be the priority persistent toxic and difficult degraded organic pollutants by the EPA of USA,EEC and China.Due to their mass production and uses for a long time,many rivers,lakes,farmlands and even groundwater in China have been polluted at different levels,which becomes a serious threaten to human health and water environment.Therefore,it is of impendence to develop highly-efficient and cost-effective innovative processes for wastewaer treatment and pollution remediation.Ozonation,catalytic ozonation of ClNBs and catalytic ozonation-biological coupling for the treatment of high concentrations of ClNBs-producing wastewater were investigated in this thesis,and the main results are as follows:1.Selecting ortho-,recta- and para-chloronitrobenzene（respectively denoted o-ClNB, m-ClNB and p-ClNB） as the model pollutants,the steady-state kinetics and mechanism of the degrdation of the pollutants in aqueous solution by ozone alone were investigated. Through studying the effect of pH and gas flowrate on mass transfer coefficient of ozone, steady-state conditions of ClNBs ozonation were determined.Afterwards,the effect of initial pollutant concentration,pH and radical scavenger（tertiary butyl alcohol,TBA） on ClNBs removal were investigated.Results demonstrated that the decomposition of ClNBs was a pseudo-first-order reaction with respect to the pollutant concentration and overall rate constant increased with an increase in the pH,however declined with an increase in the pollutant and radical scavenger concentration.Removal rate of ClNBs followed the order of o-ClNB＜m-ClNB＜p-ClNB,stoichiometric ratios of ozone and ClNBs were 1.0, reaction constants of o-ClNB,m-ClNB and p-ClNB reacting directly with ozone were 6.342×10^-3,3.890×10^-2 and 6.442×10^-2 L·mol^-1·s^-1,respectively.The reaction rate constants of o-ClNB,m-ClNB and p-ClNB with·OH,measured by means of a competition kinetics,were 2.037×10⁹,2.398×10⁹ and 3.869×10⁹ L·mol^-1·s^-1,respectively. More than 95%of ClNBs removal in ozonation system was due to hydroxyl radical oxidation at pH≥7.Results of GC-MS,LC or LC-MS show that main intermediate products of ClNBs were aromatic phenolic substances and nonaromatic acyclic substances.In the ozonation process of p-ClNB,-Cl and -NO₂ could be replaced by·OH,chlorophenol and nitrophenol were formed meanwhile.But in the ozonation process of o-ClNB and m-ClNB,neither nitrophenol nor chlorophenol was detected.The hydrogen on the phenyl of all these three ClNBs could be replaced by·OH,thus nitrochlorophenol was produced. The difference of the substitutional place of-Cl or -NO₂ on the phenyl could lead to the difference of the electron cloud density of carbon,the probability of the reaction between·OH and the hydrogen on the phenyl has some relationship with electron cloud density of carbon.The reaction between·OH and ClNBs is probably similar to the electrophilic substitution reactions of aryl.2.Efficiency and possible mechanism of homogeneous catalytic ozonation of ClNBs in aqueous solution by seven kinds of metallic ions and their combinations were compared, it was focus on the effects of pH,catalyst dosage and radical scavenger in above-mentioned system.Ozone consumption in terms of pollutant degradation and TOC elimination was also compared under the same operating conditions.Experimental results indicated that these single metallic ion and metal combinations can accelerate the rates of ClNBs removal and TOC elimination.In single metallic ion systems,increasing the catalyst concentration increased the removal rate of ClNBs;However,further increasing the catalyst concentration caused no further significant increase.When 0.4 mM catalyst was added,the effective factors at pH 2.0 followed the order Co²⁺＞V⁴⁺＞Fe²⁺＞Fe³⁺＞Zn²⁺＞Ni²⁺＞Mn²⁺ and those at pH 5.0 followed the order Co²⁺＞Ni²⁺＞Zn²⁺＞V⁴⁺＞Mn²⁺＞Fe³⁺＞Fe²⁺,suggesting that catalytic ozonation was strongly influenced by reaction media pH.In metal combination systems,the coexistence of Mn²⁺ and V⁴⁺ reduced the removal of CINBs.Considering ozone consumption during ozonation,O₃/Mn²⁺-Co²⁺ system showed the highest removal efficiency.The negative effect of the radical scavenger on the catalytic ozonation processes suggests that the degradation reaction in catalytic ozonation systems proceeds by mainly radical-type mechanisms.3.Diatomite supported MnO_x-CoO_x catalysts were prepared by the incipient impregnation method,its activity was investigated through catalytic degradation of nitrobenzene（NB） and p-ClNB by simultaneous use of it and ozone.The catalyst was characterized by SEM,XRD,FTIR and XPS.Results demonstrated that the effects of molar ratio of active components,roast temperature and time are significant;At the same time,FTIR analysis indicated that the supported metals mainly existed as multivalence mixtures and the abundant surface hydroxyl led to high dispersion of MnO_x-CoO_x; Combination of XRD and XPS analyses indicated that the supported metals were present on catalyst surface as forms of well dispersed divalent,trivalent and tetravalent oxides; The study of performance and mechanism of catalytic ozonation of NB and p-ClNB by diatomite supported bimetallic catalysts showed that addition of 1 g/L catalyst accelerated pollutants removal,especially TOC removal,enhanced TOC increments in case of pH 3.0 and pH 7.0 were 46-57%and 35-40%,respectively.Further study observed that catalytic ozonation accelerated formation of intermediate phenolic aromatics,Cl^-,NO₃^- and oxidation of acetic acid and oxalic acid,low concentrations of H₂O₂ was generated in reaction system meantime;TBA addition distinctly inhibited the proceeding of oxidation reaction,EPR experiments also showed that the existence of·OH in catalytic ozonation process,and the concentration of·OH is much higer than that in ozone alone,which is possible reason why there was enhanced pollutants removal and mineralization in catalytic system.Based on experimental results,a synergistic menchanism of catalytic ozonation was presented.4.Integrative Mn-Co modified porous diatomaceous ceramic filling catalysts were prepared,the degradation performance of production wastewater in three different processes（ozonation + unmodified porous filling,ozonation alone and catalytic ozonation） was compared.The results showed that the COD and TOC removal rates in the production wastewater through ozonation were improved by employing porous filling and Mn/Co modified porous filling,the increments in TOC and COD removal were respective 2-11%and 2.5-24%for the former while the ones for the latter were 35%and 38%, respectively.The highest increase in TOC and COD removal efficiency was achieved in the presence of ozonation/Mn-Co modified porous filling and the modification process can improve the catalytic activity of porous filling for ozonation of the production wastewater.Afetr 2 h catalytic ozonation treatment,the color of the wastewater was almost removed,the biodegradability was significantly enhanced（BOD₅/COD increased from 0.02 to 0.5 or so） and the acute toxicity inhibition on photobacteria decreased by about 25 times.From this point of view,the coupling of catalytic ozonation with sequential biological treatment processes proved quite promising.5.Single biological and a combined catalytic ozonation process（COP） / biological treatment were evaluated for the treatment of production wastewater containing toxic and refractory chlorinated nitroaromatic compounds（CNACs）.The results demonstrated that single biological treatment could remove main pollutants present in production wastewater,however,due to its poor performance in color,ammonia,TOC and COD removal,the treated effluent still did not satisfy the soecific discharge standard.COP with Mn/Co modified ceramic catalysts can be successfully used as a pre-treatment process to biocompatibilize the wastewater.With prolonged reaction time,the wastewater became decolorized and more biodegradable,as well as reaching a higher oxidation state. Moreover,the catalyst preserved its catalytic properties after 70 times of reuse,displaying good durability and stability.An integrated treatment system consisting of 1 h catalytic ozonation and subsequent 10 h biological treatment was investigated and the performance of the system was measured for 30 days.The results showed that under conditons of influent COD concentrations of 2840-3120 mg/L,average effluent concentrations of NH₃-N,COD,BOD₅,TOC and color were 10 mg/L,128 mg/L,27.5 mg/L,25.0 mg/L and 20-multiple,respectively,with corresponding average removal efficiencies are about 80%, 95.8%,93.8%,97.6%and 99.3%,respectively.It is thus concluded that the integrated catalytic ozonation/biological process is a promising and economically viable technology for the treatment of production wastewater containing recalcitrant CNACs.更多还原