电流密度对电化学氧化垃圾渗滤液效率影响

主要研究了不同电流密度对高氨氮垃圾渗滤液的电化学氧化效率,重点考察了电流密度(10、20、30、40 mA/cm)2对电解过程中的电解速率、电流效率、能耗以及三氯甲烷生成的影响。结果表明:在电流密度为30 mA/cm2时,电解6 h氨氮降解速率为7 mg/(L·min),COD降解速率为4.4 mg/(L·min),氨氮的氧化去除要先于COD的氧化去除;随着电流密度增加,电流效率逐渐增加,在电流密度为30 mA/cm2时达到45.23%,之后电流效率开始下降,电流密度为40 mA/cm2时电流效率为34%;能耗分析表明:随着电流密度增加,电解单位氨氮所需能耗先降低后升高,在电流密度为30 mA/cm2时达到最低0.09 kWh/g NH4+-N。在电流密度为40 mA/cm2时,电解6 h后三氯甲烷浓度从低于检测值升高至0.684 mg/L,产生速率为1.8μg/(L·min),三氯甲烷生成速率随着电流密度的增加而增加。     

电化学氧化预处理垃圾渗滤液的可行性研究

文章采用电化学氧化技术预处理渗滤液,在以钛涂钌铱为阳极、不锈钢为阴极,极板距离1.5cm,电流密度60mA/cm2,不外加电解质的情况下,电解120min,渗滤液的COD去除率达到48.6%,NH4+离子浓度去除率达53.6%,BOD5/COD比值由0.15提高到0.38,达到了较好的预处理效果。     

电催化降解含酚废水动力学及影响因素研究

采用填充床电化学反应器,以IrO2-Ta2O5/Ti为阳极,纯钛板为阴极,在室温条件下处理苯酚模拟废水。文章基于阶段反应理论,研究了填充床电化学系统降解苯酚废水的动力学模型,探讨了进水流速、电流密度、初始酚浓度等因素对模拟废水中苯酚和COD去除率的影响规律;在此基础上,对不同电流密度下的系统能耗进行分析。结果表明:当系统处于扩散控制阶段时,苯酚降解遵循一级反应动力学模型,在反应控制阶段属于零级反应;当起始苯酚浓度为600 mg/L(Na2SO43%),反应时间60 min,进水流速1.1 L/h,电流密度20 mA/cm2时,苯酚去除率可达99.92%,COD去除率为85.21%;随着电流密度增大,能耗提高。     

Fe-PTFE-nano-PbO_2/Ti电极电催化氧化对硝基酚废水研究

研究了模拟废水对硝基酚(p-NP)的电化学降解情况,实验中以Fe-PTFE-nano-PbO2/Ti为阳极,石墨为阴极,讨论了电流密度、p-NP初始浓度、电解质(Na2SO4)浓度、溶液初始pH这些因素对p-NP降解的影响。实验表明,电流密度越大,生成的·OH更多,去除效果越好;p-NP初始浓度越小,电解速度高于扩散速度,反应速率越快,浓度越高,产生的更难降解的与p-NP竞争有机物中间产物越多,反应速率越低;Na2SO4浓度越大,SO42-产生的中间产物因具有氧化作用,在一定浓度范围内促进有机物的降解;溶液pH越小,析氧电位越低,越不容易发生析氧副反应,提高降解效率,有利于有机物降解。实验中电流密度20 mA/cm2,p-NP起始浓度100 mg/L,Na2SO4浓度0.02 mg/L,pH为5.1时条件最优,有机物降解效果较好,120 min时p-NP去除率99.23%,COD去除率77.38%,矿化率较高。     

Ti/RuO_2-Pt电极电化学降解苯酚废水研究

研究以典型的难降解有机污染物苯酚为对象,用Ti/RuO2-Pt阳极进行电催化氧化降解研究,讨论了电解质、苯酚初始浓度、电流密度以及氨氮对苯酚降解效果的影响。研究结果表明:以NaCl为电解质比Na2SO4为电解质时处理苯酚的效果明显,而且电流密度越大、NaCl的添加量越多,苯酚全部降解所需的时间越短;在10mA/cm2的电流密度,0.3g/L氯化钠的添加量下,将苯酚从8mg/L降解为0需要30min。在电流浓度10mA/cm2,氯化钠添加量1.0g/L下,苯酚由20、40、80mg/L降解为0分别需要30、60、130min,降解时间随着浓度的增加呈接近正比增加;氨氮的存在不影响苯酚的电化学降解,而且苯酚优先降解,然后氨氮降解。     

电化学氧化法处理高浓度垃圾渗滤液的研究

实验利用电化学氧化法法除垃圾渗滤液中部分难降解有机物，以提高废水的可生化性，为后续生物处理创造条件。系统考察了温度、极板间距、氧离子浓度、pH值等因素对电化学处理垃圾渗滤液效果的影响，并通过GC-MS分析，探讨渗滤中有机污染物的去除情况，包括渗滤液中典型有毒难降解有机化合物的电化学氧化结果。结果表明：温度升高，COD和NH2-N的去除率均提高；极板间距太大或太小都会降低去除效果，极板间距10mm，处理效果较好，COD和NH3-N去除率分别达到86%和100%；随着渗滤液中Cl^-浓度的增加，COD去除率明显提高，同时高浓度Cl^-和较高的电流密度对垃圾渗滤液中难降解有机污染物的处理有相当强的协同作用效应，可以明显提高处理效果；在强酸性和强碱性条件下的电化学反应都不利于对COD、NH3-N的去除；在添加Cl^-4000mg/L，极板间距为10mm，电流密度为15A/dm^2，pH为8，初始温度为50℃的条件下，经4h的电化学氧化，COD、氨氮和色度的去除率分别达88%、100%和98%，苯酚的去除率为82%，电流效率可达84%以上。可见电化学氧化法不仅可有效的去除COD、氨氮、色度，而且对有毒的难降解有机污染物（苯酚等）有很好的去除作用，采用电化学氧化作为垃圾渗滤液废水处理的前处理，可大大改善后续生物处理的效果。     

Ti/Ti4O7阳极电化学氧化降解水中的美托洛尔

等离子喷涂法制备了钛基亚氧化钛电极(Ti/Ti_4O_7),以该电极为阳极,研究了电化学氧化法对水中美托洛尔的去除效果.考察了电流密度(5~25 mA·cm~(-2))、极板间距(5~25 mm)和初始浓度(3~50 mg·L~(-1))对美托洛尔电化学降解效率的影响;分析美托洛尔电化学降解过程中溶液总有机碳(TOC)和毒性的变化,鉴别反应中间产物并计算其毒性.研究表明:Ti/Ti_4O_7阳极电化学降解美托洛尔反应符合一级反应动力学规律(R20.95),降解效率随电流密度的增大而增大,随极板间距和初始浓度的增大而减小;TOC去除率在反应40 min后可达56.5%;反应过程中产生了质合比为266、250、223和207的中间产物,造成美托洛尔溶液的生物毒性在电化学反应过程中先升高后下降.     

电絮凝法处理PVC化工废水的试验研究

利用电絮凝法处理PVC化工废水,研究了极板材料、原水pH值、反应时间、电流密度、极板间距对处理效果的影响。实验结果表明,电絮凝法去除PVC化工废水中的浊度和COD时,在使用铝合金极板,pH值为8.0,电流密度为30 mA/cm2,极板间距为1.5 cm,反应20 min后出水浊度≤5NUT,COD≤60 mg/L。优于传统药剂絮凝对浊度和COD的去除率。电絮凝处理PVC化工废水的机理包括电絮凝、电化学氧化还原及电气浮等协同作用。     

超声辅助电催化氧化降解苯酚影响因素的研究

为探讨水体中苯酚的超声辅助电催化氧化降解,考察了超声的频率和声强、溶液的pH值、温度、支持电解质的浓度,电流密度以及苯酚的浓度等因素的影响。在超声声强分别为21.1W/cm2和27.1W/cm2下电催化氧化降解40min,COD去除率分别为59.3%和64.4%,明显高于无超声作用下41.6%的COD去除率;在中性和弱碱性介质中(pH0值在7￣11之间)苯酚的降解效果较好,pH0=10时,苯酚降解的准一级反应速率常数最大;体系的初始pH值超过11,苯酚的降解速率下降很快,这主要是因为体系的碱性太强导致许多副反应的发生,降低了电流效率,反而不利于污染物的氧化降解;溶液中的支持电解质Na2SO4的浓度(CNa2SO4)为10g/L时,苯酚降解的准一级反应速率常数和电催化氧化降解反应时的槽电压均达到最优;在电催化氧化降解过程中,随着电流密度的增加,污染物的氧化降解速率和效率也随之增大。综合考虑降解效率和电流效率两方面因素,电流密度在10￣30mA/cm2范围内较为适宜。     

钛基氧化物阳极氧化降解水中2,4-二氯酚

采用热氧化法制备了具有TiO2、RuO2和IrO2涂层的钛基氧化物电极(Ti/TiO2/RuO2/IrO2),并以其为工作电极考察了:①水中2,4-二氯酚(DCP)的循环伏安特性;②pH值、阳极电位和反应时间对阳极氧化降解DCP的影响;③阳极氧化对DCP水溶液可生化性的影响.结果表明,电极的氧化物负载量显著影响DCP的循环伏安特性.较高的介质pH值利于DCP的电化学氧化降解,而低pH值更易导致DCP挥发.低阳极电位下,DCP主要通过阳极直接氧化降解,因受电流密度过低的限制其降解效果较差;高阳极电位下,DCP主要通过阳极间接氧化降解,当阳极电位为1.8V,反应时间为360min时,DCP去除率可达100%,COD的去除超过50%,但能耗较高.COD的检测与紫外-可视光谱曲线表明,DCP的电化学氧化降解过程产生了有机中间体.Ti/TiO2/RuO2/IrO2阳极氧化可显著提高DCP水溶液的可生化性,表明其在氯酚废水预处理或脱毒领域有一定应用潜力.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.     

Removal of cadmium using MnO2 loaded D301 resin

MnO2 loaded weak basic anion exchange resin D301 （Anion exchange resin, macroreticular weak basic styrene） as adsorbent has been prepared and applied to the removal of cadmium. The adsorption characteristics have been investigated with respect to effect of pH, equilibrium isotherms, removal kinetic data, and interference of the coexisting ions. The results indicated that the Cd^2＋ could be efficiently removed using MnO2 loaded D301 resin in the pH range of 3-8 from aqueous solutions with the co-existence of high concentration of alkali and alkaline-earth metals ions. The saturate adsorption capacity of the Cd^2＋ was 77.88 mg/g. The adsorption process followed the pseudo first-order kinetics. The equilibrium data obtained in this study accorded excellently with the Langmuir adsorption isotherm.     

Effect of coagulation pretreatment on the fouling of ultrafiltration membrane

The purpose of this study is to understand the effect and mechanism of preventing membrane fouling, by coagulation pretreatment, in terms of fractional component and molecular weight of natural organic matter （NOM）. A relatively higher molecular weight （MW） of hydrophobic compounds was responsible for a rapid decline in the ultrafiltration flux. Coagulation could effectively remove the hydrophobic organics, resulting in the increase of flux. It was found that a lower MW of neutral hydrophilic compounds, which could remove inadequately by coagulation, was responsible for the slow declining flux. The fluxes in the filtration of coagulated water and supernatant water were compared and the results showed that a lower MW of neutral hydrophilic compounds remained in the supernatant water after coagulation could be rejected by a membrane, resulting in fouling. It was also found that the coagulated flocs could absorb neutral hydrophilic compounds effectively. Therefore, with the coagulated flocs formed on the membrane surface, the flux decline could be improved.     

Penetration analysis of elements and bioleaching treatment of spent refractory for recycling

Acidithiobacillus ferrooxidans ATCC23270 and Acidithiobacillus thiooxidans TM-32 were used for bioleaching of spent refractories of aluminium and copper melting furnaces for their recycling.Firstly,penetration of elements into aluminium melting furnace refractory was investigated and it was found that up to 7 cm from surface was contaminated.Comparison on leaching efficiency by the strains ATCC23270 and TM-32 found that the strain ATCC23270 could treat larger amount of the refractories than the strain TM-32 could do.In the experiment of bioleaching of spent refractory aluminium melting furnace by the strain ATCC23270,high leaching efficiency were obtained on Al,Si,and Ca,and extremely low leaching performance was,however,shown on the rest of elements i.e.,Na,Mn,and Zn.Under the strain TM-32 use,relatively high leaching performance was recognized on Al,Si,Ca,Na,Mn,and Zn.In the experiment of bioleaching for spent refractory copper melting furnace,almost the same leaching trends were shown on Cu,Zn,Al,and Si under the strains ACTT23270 and TM-32 uses.     

Simultaneous removal of ammonium and phosphate by zeolite synthesized from coal fly ash as influenced by acid treatment

Zeolite synthesized from fly ash （ZFA） without modification is not efficient for the purification of NH4＋ and phosphate at low concentrations that occur in real effluents, despite the high potential removal capacity. To develop an effective technique to enhance the removal efficiency of ammonium and phosphate at low concentrations, ZFA was modified with acid treatment and the simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated. It was seen that when compared with untreated ZFA, only the treatment by 0.01 mol/L of H2SO4 significantly improved the removal efficiency of ammonium at low initial concentrations. The behavior was well explained by the pH effect. Treatment by more concentrated H2SO4 led to the deterioration of the ZFA structure and a decrease in the cation exchange capacity. Treatment by 0.01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial P concentrations, while the treatment by concentrated H2SO4 （≥0.9 mol/L） resulted in a limited maximum phosphate immobilization capacity （PIC）. It was concluded that through a previous mild acid treatment （e.g. 0.01 mol/L of H2SO4）, ZFA can be used in the simultaneous removal of NH4＋ and P at low concentrations simulating real effluent.