| Fluoride is an essential trace element in the human body,it can effectively prevent dental caries when the fluoride ion concentration in drinking water is 0.7 mg/L.Fluoride content in water at 1.5-4.0 mg/L will lead to dental fluorosis,while drinking high concentrations of fluoride-containing groundwater for a long time will lead to female infertility,brain damage,Alzheimer’s disease,thyroid disease,etc.,which seriously threaten the human body.Therefore,it is of great significance for the study of wastewater containing trace amounts of fluorine.In this paper,the process of removing trace fluoride wastewater by natural and modified gibbsite was studied,the best fluorine removal conditions and the best modification scheme for gibbsite were obtained.The second-order defluoridation method was designed to treat the wastewater containing trace amount of fluorine to achieve the purpose of deep defluoridation.Studied on the defluorination performance of gibbsite,298 K,pH=5.0-5.5,fluoride ion concentration 30 mg/L,added 40g/L gibbsite and stirred for 120 min,the defluoridation rate reached 69.10% and the adsorption capacity was 0.5192 mg/g.The fluoride ion concentration in the solution decreased to 9.29 mg/L.The Pseudo-second-order model and the Freundlich adsorption isotherm model can better describe the process of removing fluoride by gibbsite.Studied on the defluorination performance of modified gibbsite,298 K,pH=5.0-5.5,fluoride ion concentration 30 mg/L,added 40g/L modified gibbsite and stirred for 120 min,the defluoridation rate reached 89.73% and the adsorption capacity was 0.6752 mg/g.The fluoride ion concentration in the solution decreased to 3.09 mg/L,the second-order defluoridation method can finally reduce the fluoride ion concentration in the solution to0.36 mg/L.The Pseudo-second-order model and the Freundlich adsorption isotherm model can better describe the process of removing fluoride by modified gibbsite.And it had good regenerability and can be reused. |
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