Effect Of Aluminum Sulfate On Dynamic Removal Of Fluoride By Activated Alumina

Fluoride is essential to human health. The reasonable amount of fluoride absorbing by human body health has a positive role in human health, but if the amount of fluoride taken is too high or too low,it will seriously affect our health. Activated alumina is commonly used as fluoride adsorbent agent, with specific fluoride removal capacity. The shortcoming is the time of effective removal of fluoride in one defluorination period is short, and it needs to be regenetated frequently. In order to prolong the time of effective removal of fluoride in one defluorination period through the activated alumina filter column, we add aluminum sulfate to the column.Activated alumina filter column with aluminum sulfate added can removal fluoride with coagulation except for activated alumina defuoridation. Aluminum sulfate, as a commonly used regeneration agent, has regenerative effect on activated alumina, and the sulfate ions has competitive adsorption with fluoride ions.The project choose activated alumina with a particle size of 2-4 mm.This project used three ways to inject aluminum sulfate: column mixing, pre column mixing, raw water mixing.We choose 1mg/l, 5mg/l, 10mg/l, 15mg/l as the concentration of aluminum sulfate in the filter column. The results showed that:(1) the optimal pH of the active alumina was 5, the adsorption equilibrium time was 5 h, and the effect of fluoride removal by the active alumina was the most affected by the sulfate ion.(2) with the increase of aluminum sulfate, the removal rate of fluoride in the effluent increased. When the dosage of aluminum sulfate in the filter column was 1 mg/L, 5 mg/L, 10 mg/L and 15 mg/L, the removal rates of fluoride ions in water were 5.13%, 7.68%, 7.91% and 8.57%, respectively.(3) for the activated alumina filter column with aluminum sulfate in it, the time of effective removal of fluoride in one defluorination period extended. When the concentration of aluminum sulfate, added by column mixing, in filter column was 1 mg / L, 5 mg, 10 mg / L, 15 mg / L, the time of effective removal of fluoride in one defluorination period extended to 8 h, 9 h, 8 h, 7 h,with 6 h for the control group; When the concentration of aluminum sulfate, added by pre column mixing, in filter column was 1 mg / L, 5 mg, 10 mg / L, 15 mg / L, the time of effective removal of fluoride in one defluorination period extended to 10 h, 10 h, 7 h, with 6 h for the control group.(4) for the activated alumina filter column with aluminum sulfate in it, in one defluorination period, the volume of water treated, the amount of fluoride actually removed and the caculated amount of fluoride removal by adsorption increased. By pre column mixing, the concentration of aluminum sulfate was 5 mg / L, 10 mg / L and 15 mg / L, the volume of water treated increased to 6.01 L, 6.01 L, 4.21 L, with 3.61 L for the control group; the amount of fluoride actually removed increased to 27.20 mg, 26.31 mg, 18.81 mg, with 15.87 mg for the control group; the caculated amount of fluoride removal by acsorption increased to 24.89 mg, 23.93 mg 17.01 mg, with 15.87 mg for the control group.