Study On Fluorite Removal By Coated Filter Media Of Zeolite And Bentonite

Fluorin is an essential trace element to human, appropriate amount of fluorin is indispensable for maintaining bone and tooth development, But long-term consumption of water with high fluorin would lead to dental fluorosis and skeletal fluorosis or more seriously, will lead to skeletal deformation, pain, joint stiffness, calcified tendons or legs, walking difficulties, even paralysis. Currently, there are still tens of millions of people in our country drinking high-fluorine water, high-fluorine water is a serious threat to human health. In order to explore cost-effective methods and techniques to remove fluorin, this paper conducted researches on defluorination performance of zeolite and ca-bentonite, analysised the law of bentonite and zeolite's adsorption of fluoride, and its modification, manufactured a series of variability media defluorant.This experiment and research using AICl₃ as a denaturant, using natural zeolite as a carrier, aluminum hydroxide in the chemical deposition coveraged the zeolite surface, and then under the conditions of high temperature baking at 450℃, generated；γ-Al₂O₃ coveraged in the zeolite surface, made(coprecipitation) of variability zeolite filter; adopting impregnation method so that Al3+ comes into the zeolite's internal skeleton space making ion exchange and made of(impregnation) variability zeolite filter; using zirconium oxychloride as a denaturant to modify bentonite, hydrated cations and zirconium ions came from zirconium salt Hydrolysis occurred exchange reaction with the cation came from bentonite, loaded in the face of bentonite, some parts of zirconium ions are adsorbed by bentonite, after added alkali, generated Zirconium oxide hydrate loaded in the face of bentonite, made of zirconium filter loading bentonite. Filter media's surface condition and the surface energy are different from those of non-modified filter, denaturation made their surface characteristics changed, the surface area increased, surface active adsorption sites and active adsorption points increased too, surface adsorption capability strengthened. Through numerous experiments, studied and analysised the variability media on the choice of carrier, the carrier surface pretreatment, and different coating methods.Through test of fluoride removal, non-modified zeolite and calcium bentonite statically and dynamically contrasted with variability zeolite and Zirconium load bentonite filter under the condition of different parameters. The results show:1. the static tests, the non-modified zeolite has a certain water fluoride removal rate(30%-40%), Note the zeolite adsorption capacity, (coprecipitation) variability zeolite fluoride removal capacity significantly improved compared to non-modified zeolite, 70% above; (impregnation) variability zeolite fluoride removal better effect, In the static test, variability zeolite fluoride removal rate steady at more than 77%.2. the static tests, Ca-bentonite adsorption experiments showed that in the absence of hydrochloric acid it almost has no fluoride ion adsorption performance, After heat and the acidification ,its fluoride removal performance can noticeably improved, initial solution with concentration of fluoride ion at 10mg/L and 5mg/L can be handled at the scope of the drinking water standards (0.5-1. Omg/L), after handled, the minimum concentration is 0.51mg/L and 0.84mg/L.3. zirconium loading bentonite has good stability in water, its application has good prospects, When the time for the adsorption equilibrium between 0.5～1h, With the initial concentration of fluoride ions increases, concentration of fluoride ions for balance increases. Fluoride ion adsorption for balance is high when the initial solution pH value between 6.58～7.95, When adding lg bentonite to 100mL solution which the initial fluoride concentration is at 15.2mg/Land 19.00mg/L, reacting an hour later, the fluoride ion concentration for balance in the solution is 0.28mg/L and 0.81mg/L, it's able to meet the potable water needs of the fluoride ion.In this study, also conducted a pilot study on affecting factors of the static and dynamic filtered defluorination.rate, such as the concentration of denaturing agent, filter media calcination temperature, concentration and pH of fluoride in the fluoride water, filtration rate in the dynamic filtration, etc used in making of denaturing filter. Through the test, made the static adsorption isotherms of filters listed above, with office graphics software mathematical fitting the isotherms, got adsorption types the static adsorption isotherms belongs, this thesis also made analysis and discussion on the theory of denaturing filter defluorination on the basis of comprehensive analysis of experimental data.