负载型三维粒子电极降解甲基橙模拟废水研究

采用负载型活性炭为填充电极的三维电极法处理甲基橙模拟废水,研究了不同粒子电极的处理效果,考察了影响模拟废水中色度与COD去除率的因素,探讨了甲基橙降解的反应动力学,并运用紫外-可见吸收光谱初步研究了甲基橙的降解机理.结果表明,负载锰的氧化物的粒子电极处理效果最好,降解3h后,色度与COD去除率分别达95%与80%;通过单因素实验确定的最佳实验条件:槽电压12V,初始pH值为3,辅助电解质浓度0.05mol/L.反应动力学分析显示,甲基橙降解反应表现为一级反应动力学.紫外-可见吸收光谱分析结果表明,以负载型活性炭为粒子电极的三维电极法对模拟废水中的色度与COD具有很好的降解效果.     

交联壳聚糖-CdS颗粒可见光催化脱色甲基橙研究

利用壳聚糖对金属离子的配位络合作用和吸附性能,模拟生物矿化仿生制备交联壳聚糖/CdS复合粒子。以甲基橙为处理对象,氙灯模拟可见光,研究了该复合材料对甲基橙的降解脱色性能。用Langmuir-Hinshelwood方程从动力学的角度,考察了不同催化剂浓度、甲基橙的初始浓度、反应体系的pH值、外加无机阴离子等对甲基橙降解脱色的影响。结果表明,该复合材料的吸附性能和光催化活性产生的协同作用能较有效促进甲基橙染料的脱色,在低质量浓度条件下可见光催化过程为假一级反应。光催化剂的最佳用量为1.5g/L,甲基橙降解的最佳pH为4.0。Cl-和Br-均对MO的光催化脱色起抑制作用,而NO3-的添加明显促进MO的光催化速率。     

磷钨酸光催化降解甲基橙溶液的研究

以磷钨酸为光催化剂,在紫外灯照射下,对模拟染料废水甲基橙溶液进行光催化降解反应;研究了催化剂加入量、甲基橙初始质量浓度、外加TiO2和氧化剂H2O2、KIO4对甲基橙溶液光催化脱色效果的影响。结果表明:100mL20mg/L甲基橙溶液光催化剂最佳用量80m g;在较低浓度下,甲基橙溶液的光催化降解反应符合一级动力学方程;在特定条件下,(TiO2+H3PW12O40)/UV、(H2O2+H3PW12O40)/UV和(KIO4+H3PW12O40)/UV光催化体系对甲基橙溶液光催化脱色效果优于H3PW12O40/UV光催化体系。     

磺化酞菁钴光催化降解甲基橙染料的试验研究

针对难降解的偶氮染料废水,在以磺化酞菁钴CoPcS为催化剂的情况下,实验研究了催化剂浓度、光照强度、温度、甲基橙初始浓度对降解效果的影响。结果表明:当催化剂CoPcS浓度0.2 g/L,光照强度250 W,温度40℃,pH=1,甲基橙10 mg/L时,在30 min内,甲基橙的降解率高达98.06%。最佳试验条件:pH值为1,催化剂浓度0.2 g/L,甲基橙初始浓度15 mg/L,温度40℃。影响因素主次为:pH值〉甲基橙初始浓度〉温度〉催化剂浓度,该反应符合零级反应动力学方程。     

镀铜铁内电解法用于甲基橙的脱色研究

采用镀铜铁内电解法对甲基橙染料废水进行了降解脱色研究,考察了pH、铁屑投加量、反应时间、初始浓度对脱色效果的影响,并对镀铜铁内电解降解甲基橙的过程进行了原位循环伏安跟踪监测。结果表明:最佳反应条件为酸性条件pH值2~4,铁屑投加量为400g/L,反应时间为100min,脱色率为96.0%;镀铜铁内电解降解甲基橙过程发生了氧化还原反应,生成了甲基橙的氧化产物与还原产物。     

PAA改性纳米铁强化还原降解水中亚甲基蓝

利用纳米零价铁去除水中各类污染物是近年来的研究热点,但纳米零价铁颗粒在水中的团聚会导致反应活性降低,研究通过在纳米铁颗粒制备过程中添加分散剂聚丙烯酸(PAA),提高其分散性,强化其在水中反应活性,合成改性纳米零价铁颗粒(PAA-Fe),并首次用于降解水中的亚甲基蓝.对其SEM、TEM、XRD和比表面积表征结果表明,与未改性原始纳米零价铁颗粒相比,PAA-Fe颗粒表面较光滑,团聚减少、颗粒粒径减小,比表面积增大.改性剂PAA添加浓度为0.1 g·L-1时,经过60 min降解反应,PAA改性纳米铁颗粒对亚甲基蓝的脱色率为98.84%,较未改性颗粒脱色率提高了27.32%.改性纳米铁颗粒对亚甲基蓝的脱色效果受初始溶液的p H值、初始溶液的浓度、PAA-Fe投加量和反应温度影响.PAA-Fe与亚甲基蓝的脱色反应符合假一级反应动力学规律.     

活性炭/聚丙烯腈纤维对溶液中的甲基橙染料吸附动力学研究

采用自制添加活性炭的聚丙烯腈纤维为吸附剂,吸附染料甲基橙溶液,考察了活性炭含量、温度及溶液pH值等因素对纤维吸附染料甲基橙吸附量和吸附速率的影响。结果表明,活性炭/聚丙烯腈纤维吸附甲基橙染料符合表观二级动力学方程。吸附过程的限速步骤为甲基橙染料向活性炭/聚丙烯腈纤维中活性炭颗粒内部微孔扩散,自制的活性炭/聚丙烯腈纤维对甲基橙染料具有较大的吸附容量和较快的吸附速率,可作为甲基橙等染料废水治理的理想材料。     

Fenton法氧化甲基橙溶液的脱色动力学实验研究

实验对甲基橙的Fenton氧化脱色降解反应过程进行了研究,结果表明在pH值为3、反应温度为30℃的反应条件下,Fenton试剂氧化甲基橙溶液脱色反应可以用一级动力学过程来描述,而且其反应速率常数受到亚铁离子初始浓度和过氧化氢初始浓度的影响很大,经过数据拟合分别得到了反应速率常数与亚铁离子初始浓度和过氧化氢初始浓度之间的数学关系。实验还对30℃～60℃不同温度下的Fenton反应过程进行了考察,结果表明不同温度下Fenton氧化甲基橙的脱色反应仍可以用一级动力学过程来描述,而且其反应速率常数受温度变化的影响不大,基本保持恒定。     

氰化尾渣制备微电解填料及降解甲基橙研究

以氰化尾渣为原料,采用煤基直接还原工艺制备铁碳微电解填料,并将填料用于处理甲基橙等模拟废水.研究了焙烧温度、焙烧时间、煤用量等制备条件对填料降解甲基橙的影响.结果表明,在焙烧温度为1250℃,焙烧时间为60min,煤用量为30%的条件下制备的微电解填料对甲基橙废水的脱色效果最好.提高填料用量和降低溶液初始pH值有利于去除甲基橙.用于处理400mL浓度为100mg/L的甲基橙溶液,在填料用量为2g,溶液初始pH值在3~6的范围内,当降解时间为30min时,甲基橙脱色率均接近100%.XRD分析表明,最佳条件下制备的填料中主要结晶物相为零价铁.SEM显示填料中的零价铁颗粒粒度均在50μm以下,零价铁与残碳构成微电解填料.     

填充床电催化氧化工艺处理甲基橙废水实验研究

以甲基橙模拟废水为降解对象,研究了填充床电化学反应器对偶氮燃料废水的电催化降解特性;结果表明初始浓度450mg/L,电解质含量为2%的甲基橙废水在30A/m2电流密度下经180min降解出水甲基橙浓度为2.93mg/L,去除率达99.3%,UV分析表明降解过程以键裂解为主,无其他大分子组分生成,其浓度变化符合一级动力学降解模型;在此基础上,采用单因素变量实验方法研究了初始甲基橙浓度、电流密度、电解质含量及进水流速对甲基橙电催化过程中动力学常数k的影响,得到各因素控制下动力学常数的数学表达式。依据一级动力学模型给出填充床电化学反应器处理甲基橙废水的浓度预测方程,以其通过电化学反应操作条件的优化实现甲基橙废水的彻底降解或对出水甲基橙浓度的准确预测。     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.