水环境中木质素光降解及其对有机物相关指示参数影响研究进展

木质素是陆源有机物的重要组成部分,同时也是一种良好的陆源有机物的生物标志物。光化学降解是造成木质素在水环境中指示参数变化的重要原因。简要介绍了木质素的分子结构、特征指示参数和作为生物标志物的指示原理,重点介绍水环境中木质素光化学降解的机理及影响因素,总结了由木质素光降解引起的木质素指示参数及其他有机物相关参数(例如13 C同位素、CDOM)的变化特征,综述了陆地湖泊、河流、河口及海洋等水环境中木质素光降解的研究情况。最后,指出水环境中木质素光降解的一些研究方向,包括利用CDOM光谱特征研究光降解过程、与其他参数结合表征来源以及加强光降解与生物降解相互作用的研究等。     

臭氧活性炭与背光催化联用降解水中三氯乙醛的研究

研究了臭氧活性炭与背光催化联用技术降解水中三氯乙醛的效果及其影响因素。研究结果表明,外加氧化剂的浓度、TiO_2负载量、起始液的pH、起始物浓度及光照时间对其降解效果有着明显影响。臭氧活性炭与光催化联用可有效降低水中三氯乙醛。当TiO_2负载量为2g、臭氧浓度1mg/L及活性炭质量150g,对起始物浓度20mg/L和pH 6.65的三氯乙醛溶液光照反应60min,三氯乙醛的光降解率可达99.9%。     

UV和UV/H_2O_2光解饮用水中六六六效果的研究

采用UV、UV/H2O2两种工艺分别光氧化降解饮用水中低浓度持久性有机氯农药benzene hexachloride(BHC),试验研究了不同初始浓度的α-BHC和H2O2、不同光照强度及pH对α-BHC去除效果的影响。结果表明光降解过程符合一级反应动力学模型;α-BHC的光降解速率常数随着初始浓度、光强、pH的增加而增加。一定浓度范围的H2O2有助于α-BHC的光降解,但过高反而抑制其反应速率。UV/H2O2联用对α-BHC的去除具有协同作用。     

Fenton反应催化降解苯胺及影响因素研究

对Fenton反应催化降解水中苯胺和影响催化氧化效果的几种因素进行研究和探讨。试验表明,除废水pH,Fenton试剂用量是影响苯胺降解的主要因素外,水中Cl-也对催化性能产生明显的抑制作用。虽单纯的Fenton反应对苯胺的催化降解率可达98%以上,但CODCr去除率却相对较低,表明Fenton反应对苯胺降解后的某些中间产物难于再进一步矿化,而紫外线辐照可提高Fenton反应的催化降解性能和CODCr去除率,实现对某些中间产物的持续矿化作用。     

Ti-MCM-41分子筛对水中双酚A的催化光降解反应历程

利用中压汞灯作为光源,采用Ti-MCM-41悬浮体系,对水中内分泌干扰物双酚A(BPA)进行了光降解反应,通过傅立叶红外光谱(FT-IR)、气相色谱-质谱联用(GC/MS)研究了水溶液中BPA的催化光降解的产物与反应历程.分析结果表明:水溶液中BPA光降解的中间产物主要为2-甲基-2,3-二氢-苯并呋喃和4-羟基乙酰苯酚,进一步地氧化使得苯环和脂环发生开环反应,生成小分子有机物,并最终矿化为CO2.     

研究生论文摘要

水中微量有机物的光催化降解特性及反应器数值模拟研究生:韩文亚导师:祝万鹏(清华大学环境科学与工程系100084)水中微量有机物的处理是水处理中的一个重要研究方向,光催化技术在去除各类环境介质中的微量污染物方面具有很大的应用潜力,但其降解速率太低。本论文围绕提高光催化降解速率这一目标展开研究。以对氯苯甲酸、对氯酚、对苯二酚和对硝基酚为模型化合物,研究了它们的光催化降解特性,结果表明:在UV光源辐射下,光催化降解效果的主要因素是溶解氧、溶液的流态以及光源的辐射强度;光降解和光催化降解过程对有机物降解的选择性较大。在V…     

超声引发聚苯乙烯磺酸钠的降解

用低功率、高频率的超声波对水溶液中的聚苯乙烯磺酸钠进行降解,研究溶液浓度、pH值等对降解反应的影响,用凝胶色谱法测定降解产物的分子量及其分布,用红外光谱法以及紫外分光光度法表征了降解过程中的产物结构变化,用2,2-二苯基-1-苦肼基(DPPH)对降解过程中产生的自由基进行捕捉,证实降解反应经历了自由基历程。     

常见药物左旋多巴的臭氧氧化降解技术

研究了臭氧氧化水环境中污染物左旋多巴的降解效果,重点考察了pH、臭氧流量、污染物浓度等因素。结果表明,臭氧氧化降解左旋多巴效果显著,在pH为5、污染物浓度为1 000 mg/L、臭氧流量为48 mg/min的条件下能得到较好的去除率。通过数据分析初步判定在降解过程中产生了甲酸、乙酸、草酸等中间产物。     

Ti-Ce-MCM-41介孔分子筛光催化降解壬基酚的研究

介绍了双金属掺杂介孔分子筛Ti-Ce-MCM-41的合成及结构表征,并用来催化降解内分泌干扰化学物壬基酚。该催化剂以十六烷基三甲基溴化铵为模板剂,钛酸四丁酯为钛源,采用水热方法合成。在光降解实验中,讨论了溶液的初始浓度、催化剂投加量、pH值以及光照时间对去除率的影响。结果表明:在催化剂投加量为4mg/L,光照时间为90 min,pH值为5时,可以达到最佳去除效果。     

Ti/MCM-22/MCM-41微介孔复合材料光催化降解酸性红B模拟废水的研究

采用纳米自组装法制备了具有吸附性和光催化性的Ti/MCM-22/MCM-41微介孔复合材料,利用X射线衍射、N2吸附、扫描电镜等方法对其进行表征。将复合材料用于光催化降解酸性红B的实验,考察了催化剂用量、光照时间、pH值和染料初始浓度对光催化降解率的影响,并对光降解产物进行了紫外光谱分析。结果表明:当染料的初始浓度为50 mg/L,废水pH在6左右,催化剂投加量为0.1 g/L,光照时间120 min,酸性红B的去除率可达98%以上,光催化降解反应遵循一级反应动力学方程。降解产物的紫外光谱图表明,降解后酸性红B的两个特征吸收带消失,结构的共轭系被打破,颜色消失,说明该复合材料去除水中的酸性红B主要是通过光催化作用。     

Photodegradation of sulphadimethoxine in water by medium pressure UV lamp

The photodegradation rate of sulphadimethoxine (SMT) in water was studied under polychromatic UV light, in a bench scale apparatus. SMT photolysis was carried out at pH levels of 2.5, 6.5 and 10 to study the impact of acid base properties on the degradation of SMT. The highest SMT photolysis fluence based rate was found at pH=2.5 (k=7.22x10(-4) cm2/mJ) and the lowest rate at pH=10 (k=4.72x10(-4) cm2/mJ), thus the reaction rate decreases with an increase in pH between pH values of 2.5-10. Results indicated that direct photolysis is not satisfactory for degradation of SMT by polychromatic UV lamp as a fluence of approximately 7,000 mJ/cm2 is needed to break down 99% of SMT at pH 6.5. The photodegradation products of SMT were studied at various pH values. Photodegradation of SMT results in dissimilar relative amounts of intermediates formed at different pH values which may exert a photon demand and impact on SMT photodegradation rate.     

Photodegradation of Pb-3,4-dihydroxybenzoic acid complex under UV light illumination

The degradation of 3,4-dihydroxybenzoic acid (3,4-DHBA) in the presence and absence of Pb(2+) under UV illumination was studied. Addition of Pb(2+) caused the formation of precipitate during photoreaction when the solution pH was higher than 6. The presence of Pb(2+) remarkably inhibited the degradation of 3,4-DHBA and its photodegradation intermediates, while complexation of 3,4-DHBA and its photodegradation intermediates with Pb(2+) decreased the free Pb(2+) in aqueous solutions. Molecular oxygen played an important role in photodegradation of 3,4-DHBA in the presence of Pb(2+). UV-Vis spectroscopy was used to investigate the interaction between Pb(2+) and 3,4-DHBA at different pH conditions, and FT-IR was used to characterize the precipitate formed during photoreaction. The mineralization of 3,4-DHBA was investigate by total organic carbon analysis.     

UV/H_2O_2降解水溶液中抗癫痫药物苯巴比妥

采用UV/H2O2法对水溶液中的抗癫痫药物苯巴比妥(PBB)进行降解处理。研究发现:PBB的光解率随H2O2量的增加而增加,随PBB初始浓度的增加而降低。在UV/H2O2体系下PBB紫外光解的最佳p H为10.9。Cl-的存在会降低PBB的光解率,低浓度HCO-3的存在会增加PBB的光解率,高浓度的HCO-3的存在会抑制PBB的光解率。采用离子色谱和LC-MS-MS对PBB光解后的主要产物进行分析,提出了PBB可能的紫外光降解途径。结果表明:UV/H2O2法是去除水溶液中PBB的一种十分有效的方法。     

新型微介孔复合材料La/13X/MCM-41光催化降解壬基酚的研究

以碱处理后的13X分子筛、硅酸钠为原料,加入模板剂,同时引入La2O3,在水热条件下晶化生成具有良好的吸附性能和光催化性能的新型微孔-介孔复合材料La/13X/MCM-41,并将其应用于壬基酚(NP)的光催化降解.通过XRD、TEM、FT-IR、N2吸附-脱附等技术对复合材料的微观结构进行了表征分析.考察了催化剂用量、NP初始浓度、初始pH、光照时间等对NP光催化降解效率的影响.结果表明:在催化剂用量为0.1 g/L、初始浓度为1 mg/L、初始pH为6、光照时间为210 min的最佳条件下,NP的光催化降解效率可达93％以上,反应符合一级动力学方程,复合材料La/13X/MCM-41具有较高的催化活性.     

Photocatalytic degradation of di(2-ethylhexyl)phthalate adsorbed by chitin A.

Di(2-ethylhexyl)phthalate (DEHP) is a ubiquitous environmental contaminant due to its extensive use as a plasticiser and its persistence. Currently, there is no cost-effective treatment method for its removal from industrial wastewater. In a previous study, DEHP was effectively adsorbed from aqueous solution by biosorption onto chitinous materials. Biosorption can pre-concentrate DEHP from the aqueous phase for further treatment. As biosorption cannot degrade DEHP, in this study the degradation (and detoxification) of DEHP adsorbed onto chitinous material by photocatalytic oxidation (PCO) is attempted. PCO relies on hydroxyl radical (.OH), which is a strong oxidising agent, for the oxidative degradation of pollutants. It is a non-selective process which can degrade DEHP adsorbed onto chitinous material. The first part of this study is the optimisation of the degradation of adsorbed DEHP by PCO. Adsorption was carried out in the physicochemical conditions optimised in the previous study, with 500 mg/L chitin A and 40 mg/L DEHP at initial pH 2, 22+/-2 degrees C and 150 rpm agitation for 5 min. After optimisation of PCO, a 61% removal efficiency of 10 mg/L of DEHP was achieved within 45 min under 0.65 mW/cm2 of UV-A with 100 mg/L TiO2, and 10 mM of H2O2 at initial pH 12. The optimisation study showed that UV-A and TiO(2) are essential for the degradation of DEHP by PCO. The degradation intermediates/products were identified by GC-MS analysis. GC-MS results showed that the di(2-ethylhexyl) side chain was first degraded, producing phthalates with shorter side chains. Further reaction produced phathalic anhydride and aliphatic compounds such as alkanol and ester. The toxicities of parental and degradation intermediates in the solution phase and on chitinous materials were followed by the Microtox test. Results indicated that toxicity can be removed after 4 h treatment by PCO. Thus the decontamination of DEHP by integrating biosorption and PCO is feasible.     

表面活性剂对土壤中多氯联苯洗脱影响研究进展

多氯联苯（PCBs）作为典型的持久性有机污染物（POPs）,在环境中广泛分布且具有生物毒性,土壤中的多氯联苯可通过食物链在生物体中富集,对生物体产生危害。多氯联苯易与土壤紧密结合,由于其难以降解,故去除土壤中多氯联苯非常困难。利用表面活性剂的亲水性和亲油性,可促进土壤中PCBs释放到水体中,水体中的多氯联苯便于进一步处理,以减轻对生态的危害。该文综述了近年来国内外对于表面活性剂促进多氯联苯从土壤向水体中释放的研究进展,在阐释了表面活性剂促进土壤中多氯联苯洗脱机理的基础上,具体分析了影响促进作用的各种因素。     

Sorption of polycyclic aromatic hydrocarbons into liposomes (artificial cell membranes) and the effects of dissolved natural organic matter

Dissolved natural organic matter (NOM) occurs widely in the aquatic environment and affects the fate of microorganic pollutants (e.g. intake, accumulation, movement, degradation, toxicity). The effect of NOM on the intake into biota (living cells) is very important. In the present study, the effects of coexisting NOM on the intake of microorganic pollutants into aquatic biota were experimentally evaluated. The NOM was concentrated from Lake Biwa water using a reverse osmosis filtration membrane. Two polycyclic aromatic hydrocarbons (PAH; pyrene and phenanthrene) were used as representative microorganic pollutants. Liposomes were synthesized in the laboratory to simulate living cell membranes and were used to investigate the intake of microorganic pollutants into aquatic biota. The experimental results (PAH onto NOM, NOM into liposomes, and PAH into liposomes) indicated that the sorption of PAH into liposomes was suppressed, apparently by PAH binding with NOM in the aqueous phase. This suggests that the accumulation and/or toxicity of microorganic pollutants can be retarded by NOM in the aqueous environment. Moreover, the experimental results indicated that sorption into liposomes (the liposome/water sorption coefficient, K_lipw) could be a better parameter for estimating the intake of microorganic pollutants into aquatic biota than the n-octanol/water partition coefficient (K_ow) in the aqueous environment.     

Biodegradation of phenol at low temperature using two-phase partitioning bioreactors.

Two-phase partitioning bioreactors offer many advantages for the removal of toxic pollutants. In particular, such systems can be loaded with very large quantities of pollutants without risks of microbial inhibition, they are self-regulated and they prevent the risks of hazardous pollutant volatilisation during aerobic treatment. However, their potential has never been tested at low temperatures. Phenol biodegradation by a cold adapted Pseudomonas strain was therefore tested at 14 or 4 degrees C using 2-undecanone, diethyl sebacate or 2-decanone as organic phases in a two-phase partitioning bioreactor. The three solvents were biocompatible at 14 degrees C but evidence was found that diethyl sebacate was biodegraded by the bacteria and this solvent was not tested further. Although only 2-decanone was suitable at 4 degrees C, phenol biodegradation was more efficient in 2-undecanone at 14 degrees C, reaching a maximum volumetric rate (based on the volume of aqueous phase) of approximately 1.94 g/L.day after 47 h of cultivation. In 2-decanone at 14 degrees C, evidence was found that phenol degradation was limited by the release of biosurfactants, which increased the solubility and toxicity of the solvent in the aqueous phase inhibiting microbial activity. This study therefore shows that pollutant removal at low temperature is feasible but that the production of biosurfactants can have a negative impact on the process and must be taken into consideration when selecting the organic solvent. Future work should therefore focus on the selection of solvents suitable for use at temperatures below 14 degrees C.     

Degradation of acephate using combined ultrasonic and ozonation method

The degradation of acephate in aqueous solutions was investigated with the ultrasonic and ozonation methods, as well as a combination of both. An experimental facility was designed and operation parameters such as the ultrasonic power, temperature, and gas flow rate were strictly controlled at constant levels. The frequency of the ultrasonic wave was 160 k Hz. The ultraviolet-visible(UV-Vis) spectroscopic and Raman spectroscopic techniques were used in the experiment. The UV-Vis spectroscopic results show that ultrasonication and ozonation have a synergistic effect in the combined system. The degradation efficiency of acephate increases from 60.6% to 87.6% after the solution is irradiated by a160 k Hz ultrasonic wave for 60 min in the ozonation process, and it is higher with the combined method than the sum of the separated ultrasonic and ozonation methods. Raman spectra studies show that degradation via the combined ultrasonic/ozonation method is more thorough than photocatalysis. The oxidability of nitrogen atoms is promoted under ultrasonic waves. Changes of the inorganic ions and degradation pathway during the degradation process were investigated in this study. Most final products are innocuous to the environment.