Study On Preparation Of New Form Defluoridation By Ligant Exchange And Performance Of Defluoridation

Fluorine is one of essential trace elements that maintains normal physiological activity. The appropriate amount fluorine ions in drinking water is of great benefit to human body health, but too many fluoride ions in drinking water are harmful to the consumer's health. In our country, the type of drinking water gives the first place to local characteristics fluorosis. Groundwater and drinking water sources land with high fluorine distribute widely in arid and semiarid regions of North-West China, there are about 70 million of people suffering from endemic disease caused by extra intake of fluoride from drinking water. Our government always premium improvement and treatment of Fluorine containing water, but the research of defluoridation at present exists all kinds of limitations. So it is important to investigate the cost-effective methods of defluoridation from drinking water.In this paper, a detail analysing and discussion of the existing defluoridation methods is made. Silicate is utilized to synthesizing a fluoride sorbent carrier that is of porous characteristics similar to molecular sieve. The defluoridation material can be obtained by loading Al³⁺ on the skeleton of the material. By the good complexation of Al³⁺ and F^-, F^- can be removed from high fluorine containing water. The research work is divided three parts. Part one has carried out the condition experiment and contrast test of commercial 5 A and 4 A molecular sieves that changed nature to get rid of a fluorine from drinking water, and find the two kinds changed the nature molecular sieves having certain effect of removing fluorine from drinking water. In part two, sodium silicate is utilized to synthesizing a fluoride sorbent carrier that is of porous characteristics similar to molecular sieve. According to the contrast experiment of defluoridation effect, reach the best than turbid sticky being qualified for being: SiO₂ is 0.6 mol/L, Al₂O₃ is 0.3 mol/L, Na₂O is 0.8 mol/L; the best crystal composing time is 3 hours; the best crystal composing temperature is 100℃. In the part three job, the carrier of fluoride sorbent is of porous structure and can be modified . The defluoridation material can be obtained by loading Al³⁺ on the skeleton of the material. By the complexation of Al³⁺ and F, F can be removed from high fluorine containing water. The defluoridation effect of the defluoridation material under different conditions are discussed in ditail, such as defluoridation condition , disturbing condition as well as some elementary technology condition, the main conclusions have been summarized as follows: the range of pH is wide in defluoridation by a fluoride sorbent of silicate, and pH=4⁸; The sorption isotherms of silicate defluoridators correlate with Freundlich isotherm models, the sorption capacity of a fluoride sorbent of silicate is about 8.5mg/g, the sorbent has the capability of defluoridation less than 1 mg/L from a high concentration in drinking water. The effect of the fluoride sorbent of silicate that the nature has been changed is better than the changed nature commercial molecular sieves. The mechanism of defluoridation is a process of ligant exchang. This method has a high defluoridation capability. It will not take sequential pollution and can get high quality defluoridated water. So It will be a kind of prospective method in the defluoridation of drinking water and industry wastewater.