【作者】 雷利荣；

【导师】 李友明；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2012， 博士

【摘要】 化学浆制浆废水经物化和生物处理后仍含有较高浓度的有机物,且呈现较深的色度,不能满足国家的排放标准,若不进行深度处理直接外排,将污染受纳水体,危害区域水环境生态安全。目前,对南方混合阔叶木化学浆制浆废水的污染特性、废水中的难生物降解有机物的特性、以及废水的深度处理技术方面的研究鲜有报道。本论文对南方混合阔叶木化学浆制浆废水的污染特性以及臭氧、催化臭氧处理效果及机理进行了较为系统深入的研究。以南方混合阔叶木化学浆制浆废水为研究对象,采取常规分析和红外、紫外、色谱、质谱等现代分析技术,研究废水的污染特性、特征污染物及在生物处理过程中的变化。结果发现,南方混合阔叶木化学浆制浆废水含有较高浓度的溶解态有机物,废水的溶解性CODcr和BOD5为1.5kg·m-3废水和0.4kg·m-3废水；废水中存在对微生物有抑制作用的物质,使废水的可生物处理性较差,BOD5/CODcr为0.27。同时,制浆废水的成分非常复杂,主要有机污染物包括酯类、苯酚类、烷烃类和有机酸类化合物,芳香族化合物的相对含量为58.16%。根据废水中检测到的主要污染物对发光细菌的半数发光抑制率EC50,废水中主要的特征污染物为苯酚类、氯酚类化合物、有机氯化物和邻苯二甲酸酯类化合物。生物处理过程显著降低了制浆废水的污染负荷,水解酸化和活性污泥法处理后废水的CODcr和BOD5去除率分别达到67%和88%,废水的BOD5/CODcr下降至0.14,处理后废水中有机污染物种类明显减少,各色谱峰的面积和强度大大下降。但是,制浆废水经生物处理后仍然存在一定浓度的难生物降解有机物,主要是邻苯二甲酸二正辛酯和6,6’-二叔丁基-2,2’亚甲基二对甲酚等木素降解产物。这些难生物降解的有机物造成了制浆废水生物处理出水仍具有较高的CODcr。同时,生物处理过程加深了废水的色度,可能是因为生物处理过程生成了新的羰基和羟基等发色团和助色团。为探索化学浆制浆废水深度处理以及降解去除废水中难生物降解有机物的可行途径,通过设计臭氧及催化臭氧处理制浆废水的流程、制备有催化活性的氧化铝负载过渡金属氧化物催化剂,研究臭氧及催化臭氧处理制浆废水二级生物处理出水的效果。结果表明,在适当的条件下可以制备物理性质稳定的催化剂,制备的氧化铝负载过渡金属氧化物催化剂的表面上负载有相应的氧化锰、氧化镍、氧化钛或氧化锆,且氧化锰、氧化镍或氧化锆能有效进入催化剂内部并负载在内部的孔道上；同时,制备的催化剂外表面和内部分布有数量众多的微孔、颗粒物、片状物或团聚物,比表面积很大。说明在催化臭氧处理废水过程中,废水中的有机污染物和臭氧能够和催化剂上的MnOx、NiOx、TiOx或ZrOx充分接触,发生催化反应。但是,氧化钛只能负载在γ-Al2O3的外表面上,未能有效进入到催化剂颗粒的内部。单独臭氧处理对制浆废水CODcr的去除效果随着反应体系pH值的提高不断增强,反应速率常数也随着提高,但是臭氧并不能使制浆废水中的有机污染物完全矿化,废水CODcr去除率并不高。臭氧在pH为3.38和8.17时处理废水120分钟后,CODcr去除率分别为41%、49.1%。同时,臭氧对制浆废水的脱色效果显著,处理45分钟后废水的色度去除率超过90%。制备的氧化铝负载过渡金属氧化物催化剂具有明显的催化性能,显著增强了臭氧对制浆废水CODcr和色度的去除效果,有效改善了废水的可生物降解性；同时,不同过渡金属氧化物对臭氧具有不同的催化活性,催化剂的性能也与制备条件有关系。MnOx(10%)/Al2O3-600催化臭氧处理制浆废水120分钟后废水CODcr的去除率为72.6%,比单独臭氧处理提高23.5%,废水色度的去除率超过98%；废水的BOD5/CODcr在处理20分钟后从0.14提高到0.59,可生物降解性明显改善。MnOx-TiOx/Al2O3-600催化臭氧处理制浆废水120分钟后对废水CODcr的去除率达到79.6%,比单独臭氧处理提高30.5%,废水色度的去除率超过99%。氧化铝负载复合过渡金属氧化物催化剂的活性和复合的过渡金属氧化物的化学组成密切相关,还与制备条件有关系。制备的MnOx-TiOx/Al2O3和MnOx-TiOx-ZrOx/Al2O3表面负载的MnOx、TiOx或ZrOx发挥了协同催化作用,显著增强了臭氧对制浆废水CODcr的去除效果,改善了废水的可生物降解性。利用紫外光谱、红外光谱、气相色谱-质谱分析废水的污染特性,结果表明：应用制备的催化剂催化臭氧深度处理制浆废水能有效降解去除废水中的有机污染物和邻苯二甲酸二正辛酯、二对甲酚等难生物降解的有机物,破坏废水中有机物的发色基团,使制浆废水的污染负荷大大下降,同时降低了废水的毒性。通过系统研究臭氧及应用制备的催化剂催化臭氧处理废水过程中溶解态臭氧浓度、反应器出口气体中臭氧浓度的变化,以及反应体系中自由基捕集剂的存在对废水处理效果的影响,探讨非均相催化臭氧氧化法降解去除废水中有机污染物的机理。结果发现,在催化臭氧处理制浆废水过程中,废水中溶解态臭氧的浓度、反应器出口气体中臭氧的浓度均低于单独臭氧处理的水平；自由基捕集剂的存在对单独臭氧处理废水的效果产生了有限的影响,而对催化臭氧处理废水的效果影响非常显著。这说明在应用制备的催化剂催化臭氧处理制浆废水过程中,废水中溶解的臭氧在催化剂作用下迅速分解生成自由基,使废水中溶解态臭氧的浓度下降,促进了气态臭氧向废水中溶解态臭氧的扩散,引起反应器出口的气体臭氧浓度下降,与此同时,生成的自由基迅速与废水中的有机物反应,使废水的CODcr快速下降。因此,在应用制备的催化剂催化臭氧处理制浆废水过程中,臭氧的消耗量增加,而利用率和效率明显提高。这同时说明羟基自由基持续有效的生成是非均相催化臭氧氧化法显著增强废水中有机污染物降解去除效果的根本原因。更多还原

【Abstract】 The southern hardwood chemical pulp effluent contains high concentration of organiccompounds and presents deep color after physicochemical treatment combined withbiological treatment, and the biologically treated effluent could not meet emission standard.Furthermore, the effluent would contaminate receiving water and endanger ecologicalenvironment if tertiary treatment is ignored. In this research, pollution characteristics ofsouthern hardwood chemical pulp effluent and its treatment efficiency and mechanism ofozonation and heterogeneous catalytic ozonation were studied.Pollution feature, characteristic pollutants of southern hardwood chemical pulp effluentand its modification during biological treatment process were investigated throughconventional analysis, infrared （IR） and ultraviolet （UV） spectra, gas chromatography （GC）and mass spectrometry. It was found that in the effluent concentration of dissolved organiccompounds is high, with the dissolved chemical oxygen demand (COD_cr) and dissolvedbiochemical oxygen demand （BOD₅） of1.5kg·m^-3and0.4kg·m^-3respectively. In addition,the value of BOD₅/COD_cris0.27, indicating bad biodegradability of the effluent. An analysisfor the data from GC-MS shows that the effluent contains a large number of organiccompounds, mainly including lipoid substances, phenols, alkanes and organic acids, and theralative content of aromatic compounds is up to58.16%. Simultaneously, based on thephotobacterium EC50of the major organic compounds measured, the main pollutants to becontrolled in the effluent are phenols, chlorophenols, organic chlorides and phthalates.After biological treatment of hydrolytic acidification combined with active sluge process,COD_crand BOD₅removal rates of the effluent were67%and88%respectively, and BOD₅/COD_crof the effluent decreased to0.14, indicating great decreasement of pollution conditionof the effluent. Furthermore, organic pollutant species of the effluent obviously reduced andchromatographic peak area and strength greatly decreased after biological treatment. However,some recalcitrant organic compounds still exist in the biologically treated effluent which aremainly Di-n-octyl phthalate,6,6’-di-tert-butyl-2,2’-methylenedi-p-cresol and other lignindegradation products. These recalcitrant organic compounds contribute greatly to the residualCOD_crof the biologically treated effluent. Simultaneously, color of the effluent deepens after biological treatment, which may be ascribed to the generation of carbonyl and hydroxylgroups in the structure of organic compounds in the biological treatment process.In order to search for the feasible method of tertiary treatment and removal of recalcitrantorganic compounds of the effluent, reactor and flow of ozonation and heterogeneous catalyticozonation of the effluent were designed, and catalysts of alumina loaded with transition metaloxides were prepared through impregnation method. Then, treatment efficiency of the effluentwith ozonation and catalytic ozonation was researched. It was found that catalysts with stablephysical properties could be prepared under proper condition, and MnO_x, NiO_xand ZrO_xcould be stably loaded both on exterior and interior surface of alumina particles in the processof catalysts preparation other than TiO_x, which could only be loaded on the exterior surface ofcatalysts. Simultaneously, there are numerous micropores, microparticles or tiny slices on thesurface of the prepared catalysts, which accounts for the large specific surface area of thecatalysts. These properties of the prepared catalysts indicate that in the process of catalyticozonation, organic compounds and ozone in the effluent could closely contact with MnO_x,NiO_x, ZrO_xor TiO_xloaded on the surface of the prepared catalysts to initiate the reactions ofcatalytic ozonation.In the process of single ozonation of the effluent, COD_crremoval rate and reaction rateconstant both increased with the pH ascending, but organic compounds in the effluent couldnot be thoroughly mineralized, with COD_crremoval rates of41%and49.1%for pH of3.38and8.17respectively. Simultaneously, the effluent color was effectively removed throughsingle ozonation, with color removal rate of more than90%after45min ozonation.When the effluent was treated with ozonation catalyzed by the prepared catalysts, COD_crand color removal efficiency obviously enhanced and biodegradability of the effluentimproved evidently, compared with single ozonation. While catalytic performance of theprepared catalysts is not only dependent on the metal oxides loaded on surface of catalyst, butalso the preparation condition. It was found that COD_crremoval rates of the effluent afterozonation catalyzed by MnO_x/Al₂O₃-600and MnO_x-TiO_x/Al₂O₃-600for120min are72.6%and79.6%which are higher than single ozonation by23.5%and30.5%, and color removalrates are98%and99%respectively. Simultaneously, BOD₅/COD_crof the effluent increasesfrom0.14to0.59after ozonation for20min catalyzed by MnO_x/Al₂O₃-600, indicating obvious enhancement of biodegradability of the effluent.For the catalysts loaded with composite metal oxides, catalytic performance is dependenton the combined metal oxides and preparation condition of the catalysts. The preparedMnO_x-TiO_x/Al₂O₃and MnO_x-TiO_x-ZrO_x/Al₂O₃presented high catalytic ability and effectivelyenhanced COD_crremoval efficiency and biodegradability of the effluent during ozonation.An analysis for the data from IR spectra, UV spectra and GC-MS shows that recalcitrantorganic compounds of Di-n-octyl phthalate and6,6’-di-tert-butyl-2,2’-methylenedi-p-cresoland other organic compounds of the effluent could be effectively degraded and removed byheterogeneous catalytic ozonation, and chromophores of the organic compounds were greatlydestroyed, which obviously decreased the pollution condition and toxicity of the effluent.In order to search for the mechanism of heterogeneous catalytic ozonation, modificationof ozone concentration dissolved in effluent and in reactor outlet gas was investigated andeffect of radical scavenger on treatment efficiency was studied both for single ozonation andcatalytic ozonation. It was found that ozone concentrations dissolved in effluent and in reactoroutlet gas during catalytic ozonation was both lower than single ozonation, and that althoughthe effect of radical scavenger on treatment efficiency of single ozonation was unobvious, theexistence of radical scavenger in reaction system greatly reduced treatment efficiency ofcatalytic ozonation. Based on these results, it is suggested that during the process ofheterogeneous catalytic ozonation, ozone rapidly decomposes on surface of catalyst togenerate hydroxyl radical and ozone concentration dissolved in effluent accordingly decreases,which accelerates the diffusion of ozone from gas to effluent and reduces the ozoneconcentration in reactor outlet gas. Simultaneously, hydroxyl radicals generated react withorganic compounds in effluent, which results in rapid decrease of COD_crof the effluent. As aresult, ozone consumption increases, and ozone utilization rate and efficiency obviouslyenhance for catalytic ozonation. Consequently, it is reasonable to conclude that enhancementof removal efficiency of organic compounds during heterogeneous catalytic ozonation lies onthe continuous generation of hydroxyl radicals. The result is helpful to understand themechanism of heterogeneous catalytic ozonation.更多还原