The Influence Of Iron-xoide Deposition From Groundwater On The Fluoride Adsorption By Activated Alumina

Groundwater was an important water sources for many domestic and industry user. Compare with surface water supplies,groundwater has some advantages,such as better quality,less vulnerable to pollution,less treatment to ensure safe and more accessible. However,because of the influence of hydro-geological and rocks chemical factors,there were some contaminant in groundwater,such as fluoride and iron ion.Therefore,in some areas we must remove the exception of iron,at same time,we maybe face the needed to defluoridation for other user.This dissertation based on the distribution characteristic of fluoride and iron in China mainland,aimed at synchronal controlling the excessive fluoride and iron in groundwater. Based on the filter media coated techniques and the principle of touching oxidation removal iron process,we coated the activated alumina surface with iron oxide and manufactured a new adsorbent named as Iron-Oxide-Coated- Alumina(IOCA).The influence of Ironoxide deposition on the fluoride adsorption with activated alumina was studied by batch and model filter fluoride adsorption experiment,the main factors included adsorption capacity, time of adsorption equilibrium,adsorption rate,pH,contact time and resume performance, and so on.The corresponding mechanism of fluoride removal by IOCA was discussed as well.SEM analysis revealed that iron-oxide-coated-alumina(IOCA) was coated with Fe₃O₄,the experiment results showed that iron-oxide coated could significantly enhance the absorption capacity of activated alumina,and the optimum pH range for fluoride removal of IOCA occurred in 5.0～8.0.The fluoride absorption capacity of IOCA does not increase with the mass of coated iron,even if a small amount of iron-oxide deposition mass on activated alumina,it could enhance the adsorption capacity of fluoride also.The process of fluoride adsorption with IOCA followed pseudo-second-order adsorption kinetic mode and the Langmuir equilibrium model was found to be suitable for describing the fluoride sorption well.Fluoride adsorption process of IOCA was complicated,the surface diffusion played key role on adsorption process as well as intraparticle diffusion.Analyzing results from(BDST) model showed that maximum sorption capacity of IOCA was 8.318g/L,activated alumina was 3.844g/L,maximum sorption capacity of IOCA was influenced strongly by the bed depth.Coated treatment with iron-oxide deposition could improve efficiency the fluoride adsorption capacity of activated alumina in groundwater treatment.This study is financially supported by the Scientific and technological innovation support projects of Xi'an City(YF01197).