A Study On Fluoride Removal By Activated Alumina And Bone Char

The presence of fluoride ion in drinking water may be beneficial or detrimental to people health depending on its concentration. Drinking water with the concentration of fluoride kept within prescribed limits can reduce dental cavities and enhance the bone. However, when water supplies contain excessive fluoride concentration, it can result in dental or fluorosis, more severely it can cause crippling. In china there are several ten millions peoples suffer from endemic disease caused by extra intake of fluoride from drinking water. It is important to explore the methods of fluoride removal from drinking water.In this paper, research on the use of activated alumina and bone char was dong on both batch reactor and continuous-flow column. Batch reactor tests were performed to study the effects of pH, initial fluoride concentration and adsorbent size. Continuous-flow column studies were performed to evaluated fluoride removal characteristics, regeneration procedures and extent of deterioration of the adsorbents.Batch rector experiments show the adsorption capacity of the two materials linearly increase within the initial fluoride concentration range from 0~30mg/L. and higher removal capacities were achieved at pH range 4.0 to 9.0. Adsorption isotherm of activated alumina and bone char can be described by Langmuir adsorption isotherm in the form qe=0.72cy(l+0.074ce) and Freundlich isotherm in the form qe=0.88ce1/1.'94 respectively.Continuous-flow column experiments show there have higher removal capacity for activated alumina and bone char when empty-bed contact time was controlled within 12~15min and about 15min separately. According to a series of cycles of exhaustion and regeneration experiments. The effective regeneration procedure is soaking the adsorbent 30~50h with 1-2% Al2(SO4)3 for activated alumina and 20~30h with 1-1.5% NaOH for bone char.Studies show both activated alumina and bone char are excellent adsorbents for the removal of fluoride from drinking water. Fluoride concentration below 1 .0mg/L can be acquired easily with them and meets the requirement of drinking water standards.