Mechanism study of electrochemical oxidation in the terylene diaphragm cell

Introduction T he dem and for new technologies to rem ove or to detoxify organics, especially those that are toxic to biological treatm ent processes from aqueous effluents, is w idely recognized. T he electrochem ical m ethod for treatm ent of such kinds of w astew ater has attracted a great deal of attention recently, m ainly because of its ease of control, am enability to autom ation, high efficiency and environm ental com patibility(C om ninel- lis and N erini, 1995). A t present, dim ens…     

Enhancement of the flux for polypropylene hollow fiber membrane in a submerged membrane-bioreactor by surface modification

IntroductionThe combination of membrane separation withthe process of biological reactor is called membranebioreactor (MBR). Studies on MBRs have receivedconsiderable attentions due to the deterioration of thewater environment and the advantages they poss…     

Radiation-induced reduction of chromium(Ⅵ) in aqueous solution by γ-irradiation in a laboratory-scale

Radiation-induced reduction of chromium(Ⅵ)(Cr(Ⅵ) by γ-irradiation was studied with an initial concentration of 42 mg/L in aqueous solutions. Several factors which might affect the reduction of Cr(Ⅵ) to Cr(Ⅲ) were examined. pH of aqueous solution affects the reduction efficiency significantly. Acidic condition of aqueous solution accelerates the process. At pH 2, a reduction of 86.2%was achieved with the absorbed dose of 15 kGy, while, with the same dose, at pH 5 and 7, the reduction of Cr (Ⅵ) were only 36.3%and 22.2%, respectively. Ethanol (0.1% in V:V) and sodium carbonate (1 mmol/L) were added into the solution respectively as relatively non-toxic hydroxyl radical scavengers. Reduction rate increased greatly in the presence of ethanol at each pH. Reduction efficiency of Cr(Ⅵ) was enhanced in neutral condition with the addition of sodium carbonate, however, no enhancement was found in acidic condition. The reduction of Cr(Ⅵ) was restrained when the solution was saturated with oxygen; however, the restraint was not significant.     

艾士卡-离子色谱法测定植物叶片中含硫量

建立了艾士卡-离子色谱测定植物中含硫量的方法,该法利用植物样品与艾士卡试剂的混合灼烧,将植物中的硫转化为硫酸盐进行测定,再根据硫酸根的含量计算植物中含硫量。经验证,该方法检出限为0.01%,精密度为2.3%~3.9%,回收率为91.7%~104.3%,适用于植物中含硫量的测定。     

羟基自由基与DNA中腺嘌呤碱基间反应的AM1研究

UV诱发的羟基自由基,引起了DNA互补碱对间的交联。本文论证了UV引起的互补碱对交联是UV诱发基因突变的主要根源。UV与化学致癌剂不同,可以引起双氢键AT对转化成叁氢键GC或CG对的点突变,这与腺嘌呤A在UV作用下转化成2－羟基腺嘌呤有关。本文采用高级半经验AM1方法,对UV诱发产生的羟基自由基在腺嘌呤8－位及2－位的羟基化反应,进行了计算探讨。证明在两个位置上的反应均经两步完成,反应的活化能较小并且焓变为负值、反应无论在动力学或热力学上均有利于发生。8－羟基腺嘌呤或8－羟基鸟嘌呤的存在,虽然是羟基自由基作用于DNA的标志性产物,但因其不影响小沟槽的氢键键合,很易被修复而不影响基因变异。但DNA双股中的2－羟基腺嘌呤碱或其互变异构体,则引起AT→GC或AT→CG的双氢键键合向叁氢键键合的突变。     

Hydroxyl radical concentration profile in photo-Fenton oxidation process: generation and consumption of hydroxyl radicals during the discoloration of azo-dye Orange II

Dynamic behaviors of hydroxyl (OH) radical generation and consumption in photo-Fenton oxidation process were investigated by measuring OH radical concentration during the discoloration of azo-dye Orange II. The effects of operating parameters for photo-Fenton discoloration, i.e. dosages of H₂O₂ and Fe, initial dye concentration, solution pH and UV irradiation, on the generation and consumption of OH radicals playing the main role in advanced oxidation processes were extensively studied. The scavenger probe or trapping technique in which coumarin is scavenger of OH radical was applied to estimate OH radical concentration in the photoreactor during the photo-Fenton discoloration process. The OH radical generation was enhanced with increasing the dosages of Fenton regents, H₂O₂ and Fe. At the initial stage of photo-Fenton discoloration of Orange II, the OH radical concentration rapidly increased (Phase-I) and the OH radical concentration decreased after reaching of OH radical concentration at maximum value (Phase-II). The decrease in OH radical concentration started when the complete discoloration of Orange II was nearly achieved and the H₂O₂ concentration became rather low. The dynamic behavior of OH radical concentration during the discoloration of Orange II was found to be strongly linked with the change in H₂O₂ concentration. The generation of OH radical was maximum at solution pH of 3.0 and decreased with an increase of solution pH. The OH radical generation rate in the Fenton Process was rather slower than that in the photo-Fenton process.     

Parameters affecting the stability of the digestate from a two-stage anaerobic process treating the organic fraction of municipal solid waste

This paper focused on the factors affecting the respiration rate of the digestate taken from a continuous anaerobic two-stage process treating the organic fraction of municipal solid waste (OFMSW). The process involved a hydrolytic reactor (HR) that produced a leachate fed to a submerged anaerobic membrane bioreactor (SAMBR). It was found that a volatile solids (VS) removal in the range 40-75% and an operating temperature in the HR between 21 and 35 °C resulted in digestates with similar respiration rates, with all digestates requiring 17 days of aeration before satisfying the British Standard Institution stability threshold of 16 mg CO₂ g VS⁻¹ day⁻¹. Sanitization of the digestate at 65 °C for 7 days allowed a mature digestate to be obtained. At 4 g VS L⁻¹ d⁻¹ and Solid Retention Times (SRT) greater than 70 days, all the digestates emitted CO₂ at a rate lower than 25 mg CO₂ g VS⁻¹ d⁻¹ after 3 days of aeration, while at SRT lower than 20 days all the digestates displayed a respiration rate greater than 25 mg CO₂ g VS⁻¹ d⁻¹. The compliance criteria for Class I digestate set by the European Commission (EC) and British Standard Institution (BSI) could not be met because of nickel and chromium contamination, which was probably due to attrition of the stainless steel stirrer in the HR.     

O3/H2O2处理嘧啶废水的研究

采用O3/H2O2法对嘧啶废水进行处理,考察了不同反应条件对嘧啶和COD去除率的影响,并对O3/H2O2降解嘧啶的反应机制和动力学进行了初步探讨。实验结果表明,在pH值为11,反应时间为70 min,O3流量为4 g/h,H2O2投加量为50 mmol/L的条件下,废水的嘧啶和COD的去除率分别达到86.46%和74.97%。嘧啶的去除率随自由基抑制剂叔丁醇增加而降低,说明O3/H2O2降解嘧啶主要为体系中.OH的贡献。同时动力学研究表明,O3/H2O2对嘧啶的降解符合一级反应动力学模型。     

吸附-电催化氧化降解气态氯苯

采用高接触面积微孔曝气的方式,以吸附性多孔导电材料活性炭纤维（ACF）为电极,吸附电催化氧化两步联动降解气态氯苯,实现了在电解质水溶液中对高浓度非水溶性气态挥发性有机废气的有效处理。正交实验和单因素分析实验结合,确立最佳实验条件并着重考虑pH值、鼓气速率、电解电压、电解质浓度等因素对去除率的影响。在最佳实验条件下,气相中氯苯去除率达到74.3%（20℃）和72.9%（10℃）     

沉水植被构建对上海辰山植物园景观湖水质的影响

以辰山植物园景观湖为研究对象,研究了景观湖建成初期沉水植物群落构建对水体水质因子的影响;并应用相关性分析(correlation analysis)和主成分分析(principal components analysis)对各水质和生态因子之间的相互关系进行了研究。结果表明,景观湖沉水植被建成1年后,水体水质处于Ⅲ类,其中叶绿素a含量5.48±1.930μg/L、总氮1.40±0.136mg/L、总磷0.080±0.015 mg/L、透明度108±20 cm、高锰酸盐指数5.50±1.26 mg/L;除高锰酸盐指数(CODMn)外,其他水质指标均较构建前有显著改善;并且景观湖水质显著优于外河道补充水源水质。相关性分析表明,景观湖水体叶绿素a含量与N、P营养盐呈显著正相关,但却与水温呈极显著负相关,这显示了草型景观湖水质的显著特征;主成分分析显示,第一主成分包含硝态氮、亚硝态氮、总磷、活性磷、叶绿素、水温、透明度和pH等变量,第二主成分包括高锰酸盐指数和氨氮等变量;第一主成分中的水质参数可作为辰山植物园景观湖后续水生态管理中的主要监测对象;此外,主成分分析还显示TP对水体叶绿素的增加具有很高正权重。