Researched Species Distribution Of Cr In Body Of Water/Sediment In The Haidian Stream And Restored Water Polluted By Cr(?)

Heavy metal of chromium(Cr)is a kind of environmental pollutant.In the water environment,microbial can not decomposition it,but the plant can absorbed and thus it can into the living body through the food chain,cause serious harm to human health.The degree of harm mainly depends on the forms and the level of content of chromium in the water environment.The main forms of chromium in the water environment are Cr(?)and Cr(?),trace of Cr(?)is essential to maintain the normal metabolism of glucose in the human body,and Cr(?)is a teratogenic,mutagenic,carcinogenic highly toxic substances.In addition,Cr(?)and Cr(VI)also has a long-term and can not be permanently removed characteristics in the natural water.At present,at home and abroad have accumulated and developed more effective treatment methods for different sources of chromium-containing wastewater,such as:adsorption,reduction,electrolysis,ion exchange and biological methods.A typical polluted waters quality of Haidian stream is related to the life and economic development of the local peopleis in Haikou.Therefore,study on the contents of chromium in different forms,the characteristics of migration and transformation and the hexavalent chromium removal has a theoretical and practical significance.In this paper,part of the Haidian stream waters as the object of study,studied the chromium morphology and the migration and transformation of the law in the collected water/sediment samples.The experimental method to obtain a new method for the treatment of a certain concentration of chromium containing solution.The main contents and test results are as follows:(1)The nonionic surfactant Triton X-114 n anionic surfactant sodium dodecyl sulfate(SDS)were selected to form a complex system to applied in the optimized cloud point extraction step.The established cloud point extraction-flame atomic absorption method was used to determine the occurrence of chromium in the water/sediment samples of the Haidian.Among them,the water sample was measured at a thickness of 0.45 u m,the RSD of the samples was less than 5.0%,and the recoveries were between 85%and 105%.Because the chromium is one of the harder heavy metal elements in the sediments,the sediments are pretreated with the EPA 306A method and then treated with a new masking agent(consisting of diethyl triamine pentaacetic acid and 30%triethanolamine The solution was mixed at a ratio of 1:25)to mask the interference caused by iron ions in the sample.According to all the measured results,compared with the general extraction method found that the method not only reduces the pre-oxidation treatment of different valence of chromium experimental steps,but also to avoid the color of the digestion may be in the diphenyl carbonyl two Hydrazine spectrophotometry(GB/T 7467-1987)in the determination of chromium may cause errors,so it is more efficient,simple and so on.(2)Analyzed the results of the determination of chromium in water/sediments at each sampling point.The tendency of Cr(VI)to convert to Cr(III)in the molten state from the calculated distribution coefficient.According to the "Surface Water Evaluation Criteria","Seawater Quality Standard" and "Marine Sediment Quality Standard",the study waters were classified as the fourth type of water body and the third type sediments respectively Judged that Cr(VI)pollution exists in some water bodies or sediments in the study area according to the standard.Further,the cause of contamination may be due to frequent human activities around the stream,resulting in an increase in the Cr(VI)content relative to the background value,which is obtained by the ratio of the secondary phase to the primary phase distribution.The results show that heavy metal of chromium is mainly present in Cr(?)and the content in the sediments is much larger than that in the water.(3)The removal experiments of Cr(VI)working solution with the same concentration were carried out by reduction precipitation method and activated carbon adsorption method respectively.First,the removal efficiency of five kinds of reducing agents such as sodium pyrosulfite(Na2S2O5),sodium bisulfite(NaHSO3),sodium sulfite(Na2SO3),sodium dithionite(Na2S2O4)and sodium thiosulfate(Na2S2O3)were obtained by orthogonal test.The optimum experiment was carried out by the orthogonal test of five kinds of reducing agents such as sodium pyrosulfite(Na2S2O5),sodium bisulfite(NaHSO3),sodium sulfite(Na2SO3),sodium hydrosulfite(Na2S2O4)and sodium thiosulfate(Na2S2O3)condition.Compared the adsorption effect activated carbon on the Cr(VI)working solution under the condition of unmodified and modified with different concentrations of manganese nitrate.The results showed that the activated carbon was better after modification with 0.03 mol�L-1 manganese nitrate.Then,the modified activated carbon was applied to the adsorption experiment of Cr(VI)working solution to studied the conditions affecting the adsorption.The results showed that the treatment effect is relatively good at the pH value 3,the time is 300 min,at 25 ?.(4)In the past,both domestic and foreign have been continuously improved methods in the treatment of chromium pollution,but most of them are based on a single governance law improvement,the two governance methods for collaborative governance research is relatively small.Therefore,compared the experimental results of the two treatment methods in the previous experiment.Analyzied and summarized the advantages and disadvantages of each treatment and processed the process,tried to integrate the two methods to applied standard working fluid in the feasibility of validation experiments.Compared the control effect of the last three kinds of experimental methods show that the treatment method combined the reduction precipitation with the activated carbon adsorption is more efficient,economical and practical.