Study On The Adsorption And Removing Fluoride From Drinking Water By Bone Char And Zeolite

Fluoride is one of the necessary trace elements for human being. However, those who drink water with high fluoride for a long time may suffer from fluorosis. High-fluoride water is widely spread in China, mainly in the shallow groundwater in north, northwest and northeast. Qurrently, 77 million people, who mostly concentrate in the vast rural areas, are still drinking water with excessive fluoride. 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 on treating technology of high-fluoride drinking water at home and abroad. However, some problems are existed in some 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 be urgently researched and developed to meet the decentralized water supply in rural areas and small towns according to the characteristics of high-fluoride water.There are many advantages in adsorption treatment of high fluoride drinking water. The key is to optimize the performance of adsorbents. The modification methods on adsorbents– bone char and zeolite were studied in the experiment. The mechanism on modifying adsorbent was primarily discussed. The main technical parameters were determined on adsorption treatment of high fluoride drinking water by modified artificial zeolite. The key factors of affecting efficiency of removing fluoride were revealed. The study provided scientific basis for the development of efficient and practical small-scale set for treating high-fluoride drinking water.The result show that bone char and natural zeolite can only deal with high-fluoride water with F- concentration of 3mg/L, it doesn't meet research purposes. The modification methods on artificial zeolite by NH₄Cl-FeCl₃ and NH₄Cl-KAl(SO₄)₂ were studied by the experiment. The high-fluoride water with F- concentration of 20¹00mg/L, can be treated to meet the requirements of drinking water standards in 8¹2 hours by modified artificial zeolite which was immersed in 3% NH₄Cl solution and 5% FeCl₃ solution or 3% NH₄Cl solution and 4% KAl(SO₄)₂ solution. Results show that F- removal performance of artificial zeolite modified by NH₄Cl-KAl(SO₄)₂ excels that by NH₄Cl-FeCl₃,and it is low cost, easy to operate.The equation and Freunlich equation were fitted zeolite adsorption system processing. Natural zeolite modified by NaOH-FeCl₃ and artificial zeolite modified by NH₄Cl-KAl(SO₄)₂ agree with Langmuir isotherm model, which adsorption capacity was 0.367mg/g, and 4.673mg/g, artificial zeolite modified by NH₄Cl-FeCl₃ agree with Freunlich isotherm model, 1/n is 0.419, indicating zeolite adsorption of fluoride ions have an advantage.Additionally, regeneration of artificial zeolite modified by 3%NH₄Cl and 4%KAl(SO₄)₂ had been done,and showing practical value of this work.