生物电Fenton系统氧化降解水体中微囊藻毒素-LR

建立以Fe@Fe_2O_3/非催化碳毡(NCF)为阴极电极的生物电Fenton(BEF)系统,研究其对微囊藻毒素-LR(MCLR)的去除效果,并对反应机理进行探究。实验采用从培养的铜绿微囊藻中提取得到的MC-LR。结果表明,以80%甲醇作提取剂,采用磁力搅拌技术时,MC-LR的提取效率最高,达到1.066 mg·g-1干藻细胞。BEF系统4 h内能完全降解初始浓度为0.5 mg·L-1的MC-LR。由于MC-LR是极性化合物,BEF系统对MC-LR的吸附很少,主要通过Fenton氧化作用去除。通过液相色谱-质谱联用检测到2种可能的降解产物质荷比m/z 947.8和971.3,推测MC-LR在BEF系统中可能的降解途径主要包括:Mdha上CC—CO键的氧化;酰胺键的水解;Adda上苯环的氧化。     

白腐菌S.commune降解微囊藻毒素-LR的研究

为研究真菌对微囊藻毒素的降解作用,以白腐菌S.commune为降解菌,微囊藻毒素-LR(MC-LR)为降解目标进行生物降解,考察了白腐菌预培养方式及降解过程中的培养方式、充氧方式、温度、初始pH以及MC-LR初始浓度对降解效果的影响.结果表明,白腐菌可有效降解MC-LR,经液体预培养白腐菌对MC-LR的降解效果好于固体预培养,白腐菌静置培养过程中每天充入纯氧1min有助于MC-LR的降解,白腐菌降解MC-LR的最佳初始pH为4.5,适宜温度为30～35℃.白腐菌对MC-LR的降解能力随MC-LR初始浓度的增加而降低.在最佳条件下,当MC-LR初始质量浓度为1 mg/L时,其完全降解需要2d；当MC-LR初始质量浓度为15 mg/L时,其完全降解需要7d.高浓度MC-LR(30 mg/L以上)会对白腐菌生长产生抑制作用.MC-LR降解中间产物的具体结构尚不清楚,有待未来深入分析研究.     

微囊藻毒素-LR降解菌的筛选及降解特性研究

从上海市淀山湖表层水体中筛选分离出了1株降解微囊藻毒素-LR(MC-LR)的细菌并研究了其降解特性。根据细胞形态结构、生理生化特征及其16S rDNA基因序列分析,鉴定分离菌株DHU-28(GenBank序列登录号为HM047512)属嗜麦芽寡养单胞菌(Stenotrophomonas maltophilia)。微囊藻毒素降解实验结果表明,该菌株能在以MC-LR为唯一碳源、氮源的无机盐培养基中生长,6 d内可将初始质量浓度为15 mg/L的MC-LR降解为8.12 mg/L,降解效率达到45.9%。菌株DHU-28的最适生长温度是30℃,最适生长pH为7.0。酵母粉、蛋白胨、葡萄糖等营养物质可以明显促进菌株对MC-LR的降解效率,尤其是加入50 mg/L酵母粉后,6 d降解率达到63.2%。     

微囊藻毒素生物降解的研究进展

蓝藻水华污染造成的最主要危害之一是产生和释放以微囊藻毒素(microcystins,MCs)为主的多种藻毒素,其在饮用水中的存在可以导致人类癌症,因此对人们的健康构成了严重威胁.从MCs降解微生物菌种、酶催化降解途径和降解基因3个方面,介绍了近年来国内外MCs生物降解的研究进展.     

火山石生物滤床对微囊藻毒素的去除

微囊藻水华爆发导致大量微囊藻毒素释放至地表水环境中,严重威胁着饮用水供水安全.通过不同条件火山石自然曝气生物滤床(活性挂膜、灭活挂膜、未挂膜和无填料滤床)对不同形态、构型(MC-LR、MC-RR)的微囊藻毒素的去除实验,探讨其去除效率、途径和机理.结果表明,火山石自然曝气生物滤床对微囊藻毒素的去除是微生物降解和基质吸附共同作用的结果.胞外毒素和胞内毒素的总去除率分别为58％和91％.其中,胞外毒素主要通过微生物降解作用途径去除,占胞外毒素总去除率的(41±4.2)％,胞内毒素则主要通过基质吸附途径去除,占胞内毒素总去除率的(64±5.1)％.生物膜吸附、光降解等其他途径无明显作用.另外,不同构型的微囊藻毒素在火山石自然曝气生物滤床中均能有效去除,MC-LR和MC-RR的去除率分别为68％和54％.     

超声波-光催化氧化降解邻氯苯酚的研究

对超声波-光催化氧化降解邻氯苯酚(2-cp)进行了研究,探讨了溶液初始pH值、TiO2投加量、H2O2投加量和溶液初始浓度对邻氯苯酚降解率的影响.并对几种不同处理方法降解邻氯苯酚的结果进行了对比.结果表明,超声波和紫外光的协同效果明显,在相同的反应时间内,超声波能够明显提高光催化降解邻氯苯酚的降解率.超声波和紫外光连用,具有良好的工业应用前景.     

阳澄湖和滆湖微囊藻毒素分布及其与富营养化因子的关系

2013年6—10月进行了阳澄湖和滆湖的水样采集及分析,对水体中胞内和胞外3种微囊藻毒素(MC-LR,MCRR,MC-YR)和TN、TP、Chl-a等富营养化指标在两湖的分布情况及关系进行了研究。结果表明,阳澄湖的微囊藻毒素及富营养化因子浓度在不同点位的差异小,而滆湖从北部到南部呈下降趋势,两湖相比,滆湖的浓度远远高于阳澄湖;富营养化因子影响微囊藻毒素的浓度分布和变化;相关性分析表明MC-LR、MC-RR和MC-YR与CODMn、TN、TP、PO3-4-P、Chl-a分别呈极显著正相关性(P0.01),MC-LR、MC-YR与NH+4-N呈显著负相关(P0.05);逐步回归性分析显示Chl-a是影响3种微囊藻毒素浓度的关键因子,可以通过Chl-a对水体中MCs的浓度进行预测,为微囊藻水华和微囊藻毒素污染的预警提供重要的科学参考。     

饮用水中柱孢藻毒素与类毒素-A控制研究进展

柱孢藻毒素和类毒素-A是目前饮用水处理领域关注的两种新兴藻类分泌毒素。柱孢藻毒素分子结构稳定、沸点高、水中溶解度高,可引起严重的急性肝中毒,同时具有较强的细胞毒性与基因毒性。类毒素-A分子量小、结构简单、神经毒性极大,被称为"极速致死因子"。鉴于其广泛存在于蓝藻生长的水源水中,其浓度与微囊藻毒素相当,对饮用水安全构成较大威胁,为此对柱孢藻毒素与类毒素-A的结构特征、毒性、检测方法及控制方法进行了综述。两种溶解性藻毒素在饮用水常规处理中均难以有效去除,氯化消毒对柱孢藻毒素的降解具有较好的效果而难以氧化类毒素-A,臭氧氧化和高级氧化对两种藻毒素的去除具有一定的效果。如何强化净水工艺中柱孢藻毒素和类毒素-A的有效控制是目前该领域新的研究方向之一。     

微囊藻毒素的产生及其影响因子

介绍了光照、温度、营养元素、pH值等环境因子对微囊藻的生长及其毒素生成的影响.一定强度的光照促进毒素的合成,微囊藻生长在较低的温度或营养元素受限制时,生长速率下降,但毒素产率较高.微囊藻毒素的含量在藻的指数生长后期与稳定期达最大值,毒素产率则在指数生长初期达最大.不同环境因子可能通过不同途径影响毒素的产生,需进一步研究藻毒素的功能及合成途径.     

光电耦合技术处理3,4-二甲基苯胺废水的协同效应

高级催化氧化法的复合水处理工艺经常出现协同效应,但对于协同效应的产生机理仍不清楚。因此,针对光电耦合催化氧化体系,采用协同度为量化指标,研究了不同光照、电流密度、曝气强度、初始pH等条件对光电耦合催化体系降解3, 4-二甲基苯胺(3,4-DMA)的协同效应的影响;并通过光助电催化实验、电助光催化实验和羟基自由基检测实验,探讨了协同效应存在的原因。结果表明,光电耦合催化氧化系统存在协同效应,且协同度受外部条件的影响。协同效应产生的原因主要包括:外加电场促进体系产生了更多的羟基自由基;紫外光照使得3,4-DMA及其降解中间产物受到激发而提高了对羟基自由基等活性氧物种的利用率;电催化过程中的析氧副反应为光催化提供了电子受体,从而提高了系统的总体降解效率。这为深入研究和人为调控协同效应提供了新的方法。     

Ag／ZnO光催化降解甲基对硫磷研究

描述了掺杂体系Ａｇ／ＺｎＯ用于甲基对硫磷水溶液光催化降解,有氧存在下,经ＵＶ照射对甲基对硫磷光降解是有效的,并讨论了影响光降解中甲基硫磷诸因素,初步探讨了光降解机理和动力学,起始降解物为Ｃ２Ｈ６Ｐ＾＋Ｓ和Ｏ２ＮＨ４Ｏ,且是一级反应,半衰期为１．８２ｍｉｎ。     

不同高级氧化法对水中低浓度药物甲硝唑降解过程的比较

采用UV、H₂O₂、UV/H₂O₂、Fenton、UV/Fenton和UV/TiO₂方法，对水中低浓度的药物甲硝唑进行降解。通过HPLC和UV-Vis光谱得到的甲硝唑去除率。详细讨论了Fe²⁺、TiO₂和H₂O₂的初始浓度以及溶液的初始pH值对降解效率的影响。结果表明，UV/Fenton和UV/TiO₂ 2种系统对水中低浓度甲硝唑均有很好的去除效果，但前者的光催化效率更高。在甲硝唑浓度=6 μmol/L，H₂O₂和Fe²⁺的初始浓度分别为0.5 mg/L和2.94 μmol/L，pH=4的条件下，UV/Fenton方法对甲硝唑水溶液光催化的最佳效率为95.8%。     

TiO2光催化降解水中土霉素的动力学研究

环境中抗生素的出现及其引起的危害正受到越来越多的关注。以高压汞灯为光源，选用较为广泛的抗生素土霉素（OTC）为处理对象。考察了初始质量浓度、反应过程中光照、催化剂投加量、溶液起始pH、溶液中DOM和NO^-₃对光催化降解的影响，研究了其光降解动力学。结果表明，TiO₂光催化氧化法能够有效去除水中半微量的OTC，OTC的光降解过程符合一级反应动力学模型；UV/TiO₂联用工艺对TOC也有很好的去除效果，反应90 min，TOC去除率可达74%；OTC的初始浓度从30 mg/L增大到90 mg/L，反应速率从0.0619 min^-1降低到0.0130 min^-1；随着光催化剂投加量的增大，光降解速率常数先增大后减小；增加溶液的pH值，速率常数逐渐减小；溶液中的DOM和NO^-₃也可以影响光降解效率。     

UV/TiO2薄膜体系光降解酞酸酯研究

采用自制玻璃负载TiO2薄膜,研究了UV-V is/TiO2以及UV/TiO2/H2O2体系对2种酞酸酯DBP和DEHP的光催化降解情况。研究结果表明,TiO2在暗处对酞酸酯没有降解作用;UV/TiO2体系能有效光降解DBP和DEHP,TiO2具有明显的光催化作用,增强因子分别为fDBP=2.06,fDEHP=1.53;在一定浓度范围内DBP在UV/TiO2体系中的降解速率与其初始浓度成负一级动力学关系;UV/TiO2/H2O2体系对DBP的光降解能力远大于UV/TiO2和UV/H2O2体系,H2O2能显著提高TiO2的光催化活性。     

Photocatalytic degradation of the herbicide erioglaucine in the presence of nanosized titanium dioxide: comparison and modeling of reaction kinetics

The present work mainly deals with photocatalytic degradation of a herbicide, erioglaucine, in water in the presence of TiO2 nanoparticles (Degussa P-25) under ultraviolet (UV) light illumination (30 W). The degradation rate of erioglaucine was not so high when the photolysis was carried out in the absence of TiO2 and it was negligible in the absence of UV light. We have studied the influence of the basic photocatalytic parameters such as pH of the solution, amount of TiO2, irradiation time and initial concentration of erioglaucine on the photodegradation efficiency of erioglaucine. A kinetic model is applied for the photocatalytic oxidation by the UV/TiO2 system. Experimental results indicated that the photocatalytic degradation process could be explained in terms of the Langmuir-Hinshelwood kinetic model. The values of the adsorption equilibrium constant, K, and the second order kinetic rate constant, k, were 0.116 ppm-1 and 0.984 ppm min-1, respectively. In this work, we also compared the reactivity between the commercial TiO2 Degussa P-25 and a rutile TiO2. The photocatalytic activities of both photocatalysts were tested using the herbicide solution. We have noticed that photodegradation efficiency was different between both of them. The higher photoactivity of Degussa P-25 compared to that of rutile TiO2 for the photodegradation of erioglaucine may be due to higher hydroxyl content, higher surface area, nano-size and crystallinity of the Degussa P-25. Our results also showed that the UV/TiO2 process with Degussa P-25 as photocatalyst was appropriate as the effective treatment method for removal of erioglaucine from a real wastewater. The electrical energy consumption per order of magnitude for photocatalytic degradation of erioglaucine was lower with Degussa P-25 than in the presence of rutile TiO2.     

Photocatalytic oxidation of toxic organohalides with TiO2/UV: the effects of humic substances and organic mixtures

TiO2/UV photocatalytic oxidation of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), 1,2,3-trichlorobenzene and 4-chlorophenol were examined in aqueous solution in the presence of humic substances and organic mixtures to study if the degradation rates were affected. Both commercial and natural humic substances were observed to retard the photodegradation rates, with a greater effect from the natural humic substances. Acetonitrile and isopropanol also caused significant retardation of 4-chlorophenol photodegradation. The overall retardation can be attributed to the combination of light attenuation, inhibition and competition effects. Moreover, the TiO2/UV system favors the decomposition of compounds that have stronger adsorption onto the TiO2 surface. To engineer effective treatment facilities that use the TiO2/UV system for the treatment of toxic substances in wastewater, the methodology must allow for concerns about adventitious species which are present.     

Photocatalytic decomposition of crotamiton over aqueous TiO(2) suspensions: determination of intermediates and the reaction pathway

The photocatalytic degradation of crotamiton in aqueous solution using TiO₂ was investigated. To investigate the effect of initial pH, the photodegradation behaviors of three types of pharmaceuticals were compared (crotamiton, clofibric acid, sulfamethoxazole). The degradation rates of crotamiton in the pH range 3-9 were nearly equal, but those of clofibric acid and sulfamethoxazole were affected by pH. At pH > 6.5, TiO₂ particles, clofibric acid and sulfamethoxazole had negative charge, therefore, the repulsive force between TiO₂ particles and anionic pharmaceuticals occurred and a low reaction rate at high pH was observed. The effect of UV intensity and TiO₂ concentration on photodegradation efficiency was also investigated. Linear and logarithmical relationships between UV intensity, TiO₂ concentration and the reaction rate constant were confirmed. Furthermore, the structures of photodegradation intermediates formed concomitantly with the disappearance of crotamiton were estimated. Seven intermediates were characterized by LC/MS/MS analyses, and it was assumed that the photocatalytic degradation of crotamiton was initiated by the attack of electrophilic hydroxyl radicals on aromatic rings and alkyl chains.     

Photocatalytic Degradation of the Herbicide Erioglaucine in the Presence of Nanosized Titanium Dioxide: Comparison and Modeling of Reaction Kinetics

The present work mainly deals with photocatalytic degradation of a herbicide, erioglaucine, in water in the presence of TiO₂ nanoparticles (Degussa P-25) under ultraviolet (UV) light illumination (30 W). The degradation rate of erioglaucine was not so high when the photolysis was carried out in the absence of TiO₂ and it was negligible in the absence of UV light. We have studied the influence of the basic photocatalytic parameters such as pH of the solution, amount of TiO₂, irradiation time and initial concentration of erioglaucine on the photodegradation efficiency of erioglaucine. A kinetic model is applied for the photocatalytic oxidation by the UV/TiO₂ system. Experimental results indicated that the photocatalytic degradation process could be explained in terms of the Langmuir–Hinshelwood kinetic model. The values of the adsorption equilibrium constant, K, and the second order kinetic rate constant, k, were 0.116 ppm^{? 1} and 0.984 ppm min^{? 1}, respectively. In this work, we also compared the reactivity between the commercial TiO₂ Degussa P-25 and a rutile TiO₂. The photocatalytic activities of both photocatalysts were tested using the herbicide solution. We have noticed that photodegradation efficiency was different between both of them. The higher photoactivity of Degussa P-25 compared to that of rutile TiO₂ for the photodegradation of erioglaucine may be due to higher hydroxyl content, higher surface area, nano-size and crystallinity of the Degussa P-25. Our results also showed that the UV/TiO₂ process with Degussa P-25 as photocatalyst was appropriate as the effective treatment method for removal of erioglaucine from a real wastewater. The electrical energy consumption per order of magnitude for photocatalytic degradation of erioglaucine was lower with Degussa P-25 than in the presence of rutile TiO₂.     

3种染料化合物在UV-TiO2/H2O2和UV-TiO2体系中的光催化降解研究

采用自制的TiO2膜和平板式固定床型光催化氧化反应装置,对甲基橙、茜素红和罗丹明B 3种含有不同生色基团的染料化合物进行了TiO2光催化氧化降解研究,通过对照测定降解过程中吸光度、电导率、pH的变化,分析了在加入和不加入H2O22种情况下降解过程的异同,比较了3种染料化合物脱色的难易程度,揭示了降解产物中无机离子的变化规律及某些可能的产物类型.     

UV/Fenton法处理酸性红B研究

采用UV/Fenton高级氧化技术对酸性红B模拟废水进行处理,当进水浓度为400mg/L时,确定了各影响因素的最佳投加量:H2O2投加量为2 mL/L,Fe2 投加量为0.08g/L,最佳pH值为4;并采用一级动力学公式对酸性红B降解速率进行拟合,研究了反应条件对速率常数的影响.最后通过对单独UV法、单独Fenton法和UV/Fenton法3种处理方法效果的比较,发现UV与Fenton试剂具有协同作用.