| Fluorine is a necessary element for human health.Drinking water with certain concentration of flroride can prevent dental caries and enhance the bone , but water containing excessive concentration of fluoride may result in Fluorosis. The clinical manifestations are dental and skeletal fluorosis.If mild ,teeth were gradually softening, deformity, lost of gloss enamel, became yellow. So that serious may cause the skeleton to distort, get ache, the muscle of leg calcification,walking difficultly and finally paralysed. Now, in Chnia there are several areas where people suffering from endemic disease caused by intake extra fluoride from drinking water.High-fluoride water is widely spread in China, mainly in the shallow groundwater in north, northwest and northeast. Currently, 77 million people are still drinking water with excessive fluoride, who mostly concentrate in the vast rural areas. About 5 million people drink the water in which the concentration of fluoride is more than 5.0mg/L. Their health and safety are seriously affected.Lots of studies have been done in processing technology of high-fluoride drinking water at home and abroad. However,some problems are existed in varying degrees, such as high cost of treatment, poor adaptability and applicability, unstable efficiency of removing fluoride. To supply the safety drinking water to rural residents economical and applied treatment technology of high-fluoride drinking water should is urgently researched and developed to meet the decentralized water supply in rural areas and small towns according to the characteristics of high-fluoride water.The key point of this article is the exploration to reasonable fluoride removal method . Finally the physical parting method to eliminate fluoride was chosen. There are many advantages in adsorption treatment of high-fluoride drinking water. The key problem is to optimize the performance of adsorbents.Some experiments on artificial zeolite, natural zeolite, bone charcoal were comparied ,and the zeolite was determined as a fluoride sorbent. Its mechanism of fluoride removal was studied. After researching the physical property of natural zeolite , many kinds of activation plans have been chosen.Through data analysis which obtains in the experiment,the method saline soakage for modification of zeolite was determined. zeolite was modified with iron salt soakage, first soaked in 3% ammonium chloride solution for 6 hours, and dried, then soaked in ferric chloride(5%) solution for 6 hours. zeolite got good capacity of fluorine change and then to be carried experiments on the factors affecting fluoride removal, including Zeolite dosage, reaction time, pH and so on.The experiments of zeolite removing fluorine are carried in both the dynamic and the static method. The zeolite modification and the regeneration condition was explored, and Effect on eliminating fluorine was clear. The adsorption isothermal and the adsorption speed of fluorine removal using modified zeolite was also studied. The modification methods on artificial zeolite by NH4Cl-FeCl3 and NH4Cl-KAl(SO4)2 are studied in the experiment. The mechanism on modifying adsorbents is primarily discussed. The main technical parameters are determined on adsorption treatment of high fluoride drinking water by modified artificial zeolite. The key factors of affecting efficiency of removing fluoride are revealed. The study provides scientific basis for the development of efficiency and practical small-scale set of treating high-fluoride drinking water. The diameter and height of adsorption column is 150mm, high 800mm, The density of internal filling packing zeolite. is 640kg/m3... |
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