Ion Exchange Removal of Hexavalent Selenium in Raw Water
|School||Kunming University of Science and Technology|
|Keywords||Ion exchange resin hexavalent selenium adsorption regeneration|
Selenium is a nonmetallic element that is essential trace element for humans and animals, trace amounts of selenium has anti-cancer effects and protection of the liver. But if the body absorbs too much selenium, lead poisoning, caused by gastrointestinal disorders. Selenium will have air, water, soil pollution caused by certain. In the aquatic environment, mainly in the tetravalent selenium (Se (Ⅳ)) and hexavalent (Se (VI)) two valence. The distribution of selenium in natural waters depends on the type of rock erosion and water pH. pH, a greater impact on the river selenium. For example, the iron in the United States, Colorado, Se, surface water pH value of less than 7, almost all the selenium content of less than 1μg/L; in pH value of 7.8～8.2, due to easily oxidizable selenite soluble in water, selenite, selenium in water for more than 1 mg/L, or even up to 400 mg/L. Selenium pollution comes mainly from anthropogenic and geochemical factors, industrial pollution, "waste" is the main source of anthropogenic pollution.China, the United States, the Soviet Union the provisions of selenium in drinking water should not exceed 0.01 mg/L. Maximum allowable irrigation water selenium content, the provisions of China is 0.01 mg/L, the U.S. requirement of 0.05 mg/L. This raw water for water-scarce areas of selenium (Ⅵ) exceeded the serious phenomenon, and the development and utilization of water resources in the high selenium content, the use of ion exchange processing to meet the state standards for drinking water quality, to address the raw water the problem of excessive selenium to find an effective method. The subject of using 201×7 strong base anion exchange resin by Se (Ⅵ) to repair contaminated raw water for the practical application of engineering methods to repair the polluted water selenium provide references.The main contents of this paper:(1) selection of 201×7 strong base anion exchange resin, the resin content, PH value of the raw water, raw water temperature, raw water turbidity and stirring time on the selenium (Ⅵ) the impact of the removal rate static experimental studies; (2) was addition of selenium (Ⅵ) and dynamic experimental research, measured resin except selenium (Ⅵ) in the breakthrough curve, and the resin addition to selenium (Ⅵ) mechanism was analyzed; by adsorption isotherm experiments on ion exchange resins in addition selenium (Ⅵ) adsorption model; (3) Regeneration of resin were studied, and resin regeneration principle was discussed.The results show that,201×7 strong base anion exchange resin optimum conditions for the amount of resin 4.00g/L, raw water, PH value between 6.0～12.0, the original water temperature under 20℃at room temperature, stirring time in the 1 hours or more, Se (Ⅵ) removal rate can reach 95%, raw water turbidity of selenium (Ⅵ) removal has little effect. Experiment is obtained by taking selenium (Ⅵ) adsorption isotherm of a type, with the exception of selenium (Ⅵ) Freundlich equation constant and the Freundlich adsorption model. Of sodium hydroxide, ammonia, sodium hydroxide and sodium chloride solution, the mixture of three recycled compared to 6% obtained with sodium hydroxide solution was the best resin regeneration, the regenerated resin exchange capacity can be restored. Ion exchange to remove the raw water with hexavalent selenium method is simple, practical, removal efficiency. Thus, ion exchange removal of hexavalent selenium raw water is effective and feasible.