Degradation of dyes in aqueous solutions by the Fenton process

Degradation of 20 different dyes in aqueous solutions by the Fenton process was performed. These dyes include 6 types: acidic, reactive, direct, cationic, disperse and vat dyes. The former four types of dyes were decolorized and their TOC values were decreased greatly, while the color and TOC removals of the latter two types were lower. The catalytic activities of four metal ions on the degradation efficiencies of Vat Blue BO, which was chosen as a model dye because of its lowest color and TOC removals, were compared in the dark and under the ultraviolet light irradiation. The catalytic ability of different metals was Fe2+>Cu2+>Mn2+>Ag+ in the dark, and the same sequence was obtained under irradiation condition with greater degradation efficiency. Furthermore, the efficiencies of three oxidation processes, including H2O2/UV, Fe2+/H2O2 and Fe2+/H2O2/UV were compared. The results showed that the oxidation by Fe2+/H2O2/UV was the strongest, and even greater than the arithmetic sum of the other two processes, which suggests the synergistic effect of ultraviolet and ferrous ions on the degradation reaction.     

Reduction of chromate (CrO4(2-)) by an enrichment consortium and an isolate of marine sulfate-reducing bacteria

An enrichment consortium and an isolate (isolate TKW) of sulfate-reducing bacteria (SRB) have been obtained from metal-contaminated marine sediments of Tokwawan, Hong Kong SAR. These bacteria are capable of reducing highly toxic and soluble hexavalent chromium (Cr6+) enzymatically into less toxic and insoluble trivalent chromium (Cr3+) under anaerobic conditions. The enrichment consortium almost completely (98.5%) reduced 0.6 mM Cr6+ in 168 h and the rate of reduction was 0.5 g (Cr6+) g(protein)(-1)h(-1). In comparison, with Cr6+ as the sole electron acceptor (as a surrogate for SO4(2-)), isolate TKW reduced 94.5% of the initially added Cr6+ (0.36 mM) in 288 h, with the rate of 0.26 g (Cr6+) g(protein)(-1)h(-1). Adsorption by these bacteria was not the major mechanism contributing to the transformation or removal of Cr6+. The biomass and Cr3+ in the cultures increased simultaneously with the reduction of Cr6+. These indigenous SRB might have potential application in bioremediation of metal contaminated sediments.     

硝化速率法用于活性污泥活性测试的研究

以城市污水厂回流污泥中的硝化细菌(氨氧化细菌和亚硝酸盐氧化细菌)为受试生物,HgCl2为标准毒性物质,通过对两组实验--氨氧化速率实验(NH 4-N→NO-2-N)和亚硝酸盐氧化速率实验(NO-2-N→NO-3-N)的研究表明,氨氧化细菌对HgCl2的灵敏度(IC50=0.034 mmol/L)明显高于亚硝酸盐氧化细菌(IC50=0.20 mmol/L).氨氧化速率法测试活性污泥活性时,使用NH 4-N或NO-X-N指标需要120 min或更长的时间,但使用NO-2-N指标仅需30 min就可完成测试,而且结果重现性要比NH 4-N和NO-X-N好,其变异系数CV为5.9 %.     

Effects of organic acids on adsorption of lead onto montmorillonite,goethite and humic acid

Adsorption isotherms for Pb onto six soil components (quartz, feldspar, kaolinite, montmorillonite, goethite and humic acid) were studied. The influence of pH, EDTA and citric acid on the adsorption of Pb onto montmorillonite, goethite and humic acid were considered. Results indicate that the experimental data fit the Langmuir Adsorption Isotherm. The adsorption capacity for Pb at pH 6 was found to be in the order: humic acid (22.7 mg g(-1)) > goethite (11.04 mg g(-1)) > montmorillonite (10.4 mg g(-1)) > kaolinite (0.91 mg g(-1)) > feldspar (0.503 mg g(-1)) > quartz (0.148 mg g(-1)). Generally, the amount of Pb adsorbed onto montmorillonite, goethite and humic acid decreased with increasing concentrations of EDTA and citric acid and with increases in alkality. However, there were two exceptions: (1) addition of citric acid increased the amount of Pb adsorbed onto humic acid; and (2) the amount of Pb adsorbed onto goethite decreased with increasing pH in the presence of EDTA. Some mechanisms involved in the adsorption reactions are discussed.     

An approach for treating the uncertainties in the impact of climate change

Past accumulated data supported by the predictions of climate models suggest that our world is getting warmer. Scientists are trying to construct mathematical models of both climate and crop systems to identify what types of climate changes could constitute a significant risk or benefit for agriculture. However, due to the many uncertainties regarding these models, it is impossible to make unequivocal predictions. At present, almost all the research in this area is carried out without considering the uncertain nature of the problem. The approach outlined here attempts to find a way to deal with the above uncertainty problem. Artificial intelligence techniques are being developed with the aim of performing inferences based on uncertain information. In our method, causal graphs are used for explicit representation of the relationships between climatic factors and yield. Probabilities are used to express the uncertainties associated with these links, and Bayes' theorem is applied to deal with uncertainty reasonings. This approach has the additional advantage of allowing the prediction to be readily updated as results from improved climate and crop models become available. These opportunities are being evaluated initially by using the model for potato growth developed at the Scottish Crop Research Institute.     

臭氧-曝气生物滤池处理酸性玫瑰红染料废水

在实验室配制含酸性玫瑰红染料的印染废水,采用臭氧氧化-曝气生物滤池工艺开展处理试验.试验运行结果表明,臭氧氧化处理能提高模拟废水的可生化性,BOD/COD值由原水的0.18上升到0.36.经组合工艺处理后出水COD＜40 mg/L,色度40倍以下,SS约50 mg/L,处理效果良好.     

催化湿式氧化中负载型催化剂的稳定性与应用

催化剂在应用过程中必须具有良好的催化活性和稳定性。优化制备的CuO／γ-Al2O3催化剂用于处理高浓度难降解的乳化液废水时具有良好的催化活性。在200℃时反应2h，TOC去除率为81．3％，比未加催化剂的湿式氧化提高了14．9％。该催化剂对分散兰废水具有更高的活性和稳定性：在220℃反应1．5h后，COD和TOC去除率分别为68．8％和56．5％，比非催化氧化分别提高了18．7％和18．9％。     

Fenton氧化-生物接触氧化工艺处理甲醛和乌洛托品废水

采用Fenton氧化一生物接触氧化工艺处理含甲醛和乌洛托品的模拟废水（简称废水）,在H2O2（体积分数30％）加入量2．5g／L、H2O2与Fe^2＋质量浓度比3．75、反应时间3h、不调节废水初始pH的Fenton氧化预处理最佳操作条件下,废水COD从1000mg／L左右降至300mg／L,COD去除率达72％。原废水完全无法直接进行生化处理,经Fenton氧化预处理后其BOD,／COD约为0．5,易于生化处理。Fenton氧化一生物接触氧化工艺处理废水,生物接触氧化停留时间为12h时,废水COD去除率高达94％,处理后出水COD小于70mg／L,处理效果很好。     

Mussel watch program for organic contaminants along the Korean coast, 2001–2007

The level and extent of organic contaminants along the Korean coast were estimated through the mussel watch program, established in 2001. Mussels and oysters were collected at 20 sites along the Korean coast in 2001 and at 25 sites from 2002 to 2007. The mussel tissues were analyzed for PCBs, organochlorine presticides, PAHs, BTs, and PCDD/Fs. PCBs, PAHs, BTs, and PCDD/Fs were ubiquitous contaminants along the Korean coast, showing mean detection frequencies of more than 95% over 7 years. The concentrations of organic contaminants in mussels along the Korean coast were relatively low or moderate compared with foreign studies. Concentrations of DDTs, PCBs, and PCDD/Fs were below the action or maximum levels for humans established by USFDA and EU. Elevated concentrations above the 85th percentile were found for PCBs, PAHs, BTs, and PCDD/Fs at sites near industrial complexes or big harbors, for HCHs at sites near non-industrial complexes, and for DDTs at sites near both non-industrial and industrial complexes. Using two nonparametric tests to assess temporal trends, the Spearman test revealed that BTs and PCDD/Fs had significant decreasing trends at four sites (Gwangyang Bay, Cheonsu Bay, Garorym Bay, and the Incheon coast) and at six sites (Hupo coast, Guryongpo coast, eastern part of Geojedo, Gunsan coast, Garorym Bay, and Asan Bay), respectively.     

Comparative study of torrefaction of empty fruit bunches and palm kernel shell

Journal of Material Cycles and Waste Management - This paper describes the effect of torrefaction on the characteristics of empty fruit bunches (EFB) and palm kernel shell (PKS). The torrefaction...