Defluordiation Of Drinking Water By Different Modified Resin

The fluorine is a kind of minor chemical element which is extensively existed in nature, and also one of necessary minor element of human body. For the mankind, fluoride in drinking water is a blade sword: on the one hand, the fluoride is one of the minor chemical elements that the human body needs, absorbing just the right amount of fluoride can prevent from dental caries effectively; but on the other hand, the fluoride is a chemical element which is easy to attach itself to bones. The excessive absorption of fluoride will influence the metabolism of the calcium and phosphorus of human body, resulting in fluorosis in degree, such as the diseases of dental fluorosis and Kaschi-Beck. The fluoride exists in all natural water, with the average content between 0.01mg/L～1.5mg/L. According to the World Health Organization, the concentration of fluoride in drinking water should be 1.5mg/L. China is one of the most popular and serious countries in the world, where endemic fluorosis spread widely in drinking water and endanger the people's heath. Fluoride groundwater extensively distributes in our country, especially in the Northeast, North, Northwest China, with approximate 72.26 million people drinking excessive fluoride water.The cation-exchange resin is a kind of resin with functional base groups, which can be transformed by different solutions and used to effectively remove various mental ions of water. The principle of defluordiation of drinking water in this research is to introduce the cation-exchange resin to defluoridate water. In this study the defluoridation is transformed into model-H resin,model-Al resin and model-La resin, and the research findings are that the highest efficiency of defluridation is Al cation-exchange resin, the model-La takes the second place and the lowest is strong acid cation exchange resin. And the Al cation exchange resin is analyzed by SEM, BET and IR. Chitosan, a kind of naturally occurring polysaccharide in the fungi and arthropod, was found to show an excellent ability of absorbing fluoride in drinking water treatment in terms of its biologic compatibility and avirulence. This study examines in drinking water the adsorption of fluoride with the iron-modified chitosan resin which was prepared with the chitosan as the raw material, and discusses the adsorption effects in different conditions involving the saturated adsorption time, initial concentration, adsorbent dose, pH value and other ions. It is found that model-Al₁₃ chitosan resin and model-Fe chitosan resin are characteristic of the high ,little effect from pH, easy and the stable removal effect. Additionally model-Al₁₃ chitosan resin is better than model-Fe chitosan resin in terms of adsorption effects. For both model-Al₁₃ chitosan resin and model-Fe chitosan resin which adsorb, the optimal time of adsorbing fluoride in water is 12h, and the most adsorption is 150μg/g. Under these optimized conditions, the efficiency of removal of fluoride reaches up to more than 80%, and the pH value has little effect for removal rate. PO₄^3- contained in the drinking water whose effect of removal fluoride rate for the two kinds of chitosan resin has not obtained the significant level and could be out of the consideration. However the concentration of SO₄^2- and Cl^- in the solutions greatly effect the removal rate of chitosan resin and the effect is gradually increased according to the of the concentration of fluoride. After being treated with ammonia, the adsorbed chitosan resin could be effectively reused for many times and maintains the same removal rate. The regenerated chitosan resin is similar to the original resin. Chitosan resin, one of the good adsorbent for fluoride, owns the high value of research and apply for the removal of fluoride in the drinking water.