Experimental Study On Fluoride Removal From High Fluoride-Containing Wastewater

The fluorine is one of necessary nutritional trace element for human health. Drinking water with 0.5~1mg/L concentration of fluoride is fit. But when excess fluorine is absorbed by body it can lead to "Dental Fluorosis" When the fluoride concentration reached 4~6ppm, even caused fluorosis. In our country, the technology of fluoride removal from high fluoride-containing wastewater in the chemical combination industry has not grown up. The main disadvantage of the technology is high equipment charge, high running fee and disposal effect instability. In this paper, studying on fluoride removal by lime and alumina , to provide a new method for fluoride removal from high fluoride-containing wastewater.In the research of removing fluoride by lime sedimentation method, by arranging a series experiment, confirm the optimal process parameter and manipulating conditions, establish chemical kinetics equation on the fluoride removal, study the effect of reflux CaF2 sludge. Xi'an Jinzhu jindai is a fluoride chemical combination company, during the produce process , which send out a lot of acidic and containing high fluoride wastewater, the wastewater containing fluoride 3000mg/L and pH0.8. After the company applying the result of this part experiment, the fluoride containing reduced to below 10mg/L.In the research on the use of activated alumina removal fluoride, explore the parameter of activated alumina activation and regeneration. Definitude the effect factor that influence activated alumina removal fluoride, get the consecutive diposal process dominating factor, study the adsorption isotherm of activated alumina and the rate of the adsorption.Fluoride can be removal from wastewater by growing crystals in a fluidized-bed reactor.Optimal conditions for crystallizing have been investigated on a laboratory scale pellet reactor initially seeded with phosphorite.In this paper, the study of using calcium salt coagulant and precipitation method disposal highacidic and high furoride-containing wastewater state that when the [Ca2+]=10g/Lm, that is afflux [Ca2+]/[F]=1.75, adding A12(SO4)3 400~600mg/L and PAM 2mg/L, pH controlled at 9, the fluoride in the wastewater can be reduced to below 10mg/L,which fit the regulate let out concentration hi the "Generalized Sewage let out Criterion" (GB8979-96). Reflux CaF2 sludge is inefficient to the fluoride concentration at 3000mg/L, but to the fluoride concentration at 40mg/L is useful. The results indicated that rate of fluoride removal with the kinetics equation of third order reaction in precipitation reaction. The study of fluoride removal by growing crystals in a fluidized-bed indicate that with an effluent-pH of 7-9, a [Ca2+]/[F~] feeding ratio of l~1.3mol/mol,an fluoride-load of less 2kg F per square meter reactor cross-section per hour and a hydraulic load of 35~50m/h,the effluent fluoride concentration was below 5mg/L. The study on fluoride removal by activated alumina state that there are many factors influencing the adsorption capacity. The adsorption isotherm of activated alumina conforms to Langmuir adsorption equation as qe = 1.035Ce/l + 0.246Ce in 25 C. The adsorption capacity decreases with pH, as pH varies from 4 to 9. In the continuous-flow column experiment,the contact-time is a very important factor, the pull-down speed of adsorption curve in the continuous-flow column is related to the concentration and flow rate of the raw water.