Research On The Technology Of The Fluoride Adsorption Capacity And Regeneration Of Alumina

In China, there are large number of the high-risk areas of endemic fluorosis.Fluorine-containing water cause serious damage to human health. Now, aluminaadsorption process has been widely applied to removing fluoride from groundwater.However, in practical applications, the difference of process conditions duringpreparation causing the different crystalline form and pore size between aluminaparticles, so the actual effect of fluoride removal will be affected.Batch experiments focused on defluoridation and regeneration performance ofthree kinds of typical commercial alumina were conducted in this study. The XRDanylysis and SEM were used. The great role of the crystalline construct of alumina inthe defluoridation and regeneration characteristics and the regeneration effect ofdifferent regenerants to alumina were studied through static state test and regenerativetest. The results showed that the crystalline construct of alumina have an effect on thedefluoridation and regeneration of alumina. Among the three types of alumina, η-Al₂O₃using in the experiment has a better effect of defluorination which has not been reportedin the current study. So the following research mainly focuse on the defluorinating andregeneration process of η-Al₂O₃. The factors affecting the adsorption capacity ofη-Al₂O₃were studied to determine the optimum conditions and useful life of η-Al₂O₃.All the results aimed to provide a reference for the enhancement of fluoride adsorptioncapacity of alumina.The results are following:1) The crystalline construct of alumina plays a great role in the defluoridation andregeneration. The three adsorbents （γ-AlOOH, η-Al₂O₃and transitional phases of aluminumoxide） used in this research have the similar physical characteristics and theyfollow the same kinetics and adsorption isotherm models. The fluoride adsorptioncapacity of three adsorbents varied with alumina types.2) The alkaline regenerants are suit for three adsorbents while the acidicregenerants which may lead to a fast decay of adsorption are not. Sodium carbonate andsodium bicarbonate have better regeneration effect to regenerate γ-AlOOH. The bestregenerant of η-Al₂O₃is sodium carbonate. Alkaline regenerants all have a stable effectto regenerate the transitional phases of aluminum oxide.3) As the large capacity of absorption, long using life and better regenerating effect,η-Al₂O₃can be used in the high fluoride water treatment which has high economicefficiency and a good application prospect.4) Before using, η-Al₂O₃should be activated. Concentration difference may effectdefluorination. The saturated η-Al₂O₃should be regenerated by5%sodium carbonateand then neutralized with1%sulfuric acid. Under dynamic condition, the filtration rateand the thickness of the filter have a significant impact on the effect of defluorination.Reducing the filtration rate and increasing the filter layer appropriately may isconducive to improve the adsorption capacity of alumina causing a better effect ofdefluoridation.