Preparation Of Novel Nano Materials For Fluoride Adsorption From Water

Millions of people around the world suffers from fluorosis because of the excessive fluoride in groundwater.In some areas of Xinjiang,there is also a problem of excessive fluoride content in groundwater,which affects the safe use of water by local residents.The adsorption method is widely used for fluorine removal because of its low cost and easy operation.However,the traditional adsorbents are greatly affected by pH,which greatly affects the defluorination efficiency.The problem of fluoride removal from groundwater is imminent,and researches on high-efficiency,low-cost adsorbent are of great significance for the removal of fluoride ions in groundwater.Based on the above problems,this paper aims to prepare nanomaterials of metal oxides and research the fluoride removal in simulated water.The defluorination performance and the mechanism of nanoscale materials in complex simulated water was explored.The specific researches of this paper are as follows:?1?Mesoporous hollow CaO spheres?MHS-CaO?were prepared by wet impregnation method,and the fluoride removal in simulated water was studied.The composition and surface morphology of MHS-CaO and its adsorption properties for fluoride ions were investigated.The effects of different pH on adsorption efficiency and the mechanism of fluoride removal on MHS-CaO were investigated.The results of batch experiments showed that the optimum pH value of the reaction in the range of pH 3-11 is 3,and the adsorption process conforms to the Langmuir model and the pseudo-second-kinetic model.The maximum adsorption capacity?q_m?obtained by fitting data was 181.96 mg/g.And the adsorption process was controlled by more than one process based on the fitness of the intra-particle diffusion model.Thermodynamic studies showed that the adsorption process is a spontaneous endothermic reaction.During the adsorption processes,chloride,sulfate,and carbonate ions showed no significant effect on adsorption,thereby suggesting that the as-prepared MHS-CaO is a promising adsorbent.MHS-CaO was converted into Ca?OH?₂,When MHS-CaO was added to fluorine-containing water.The F^-ions were removed via a surface chemical reaction in which the OH^-of Ca?OH?₂ was substituted by F^-to form CaF₂.?2?Biochar loaded nano zero-valent iron?BC-nZVI?was prepared and the adsorption of fluoride in simulated water was explored.The composition and surface morphology of BC-nZVI and its adsorption properties for fluoride ions were studied.The effects of different pH on adsorption efficiency and the mechanism were investigated.The results of batch experiments showed that the optimal pH value was 6 in the range of pH 5-10,and the adsorption process of fluoride onto BC-nZVI conforms to the Langmuir model and pseudo-second-kinetic model.The maximum adsorption capacity?q_m?obtained by the fitting datas was 56.82 mg/g.And the adsorption process was controlled by more than one process based on the fitness of the intra-particle diffusion model.Thermodynamic studies showed that the adsorption process was a spontaneous endothermic reaction.The adsorption mechanism of fluoride on BC-nZVI showed that the nZVI of BC-nZVI reacts with O₂ in water to form hydrated iron oxide.The OH^-on the hydrated iron oxide by exchanges ions with fluoride ions to form a precipitate to remove the fluoride in solutions.?3?The continuous flow experiments of fluoride removal were carried out by using the adsorbents of MHS-CaO and BC-nZVI via peristaltic pump.The fluoride removal of tandem device was investigated by three factors:flooding velocity,temperature,and pH.The experimental results showed that the final concentration of F^-would be the lowest at pH 8 when the flooding velocity is 25.8 mL/h and the temperature is 25?,which can achieve Standards for Driving Water Quality.The materials of MHS-CaO and BC-nZVI have excellent effects on the fluoride removal in water.Compared with the traditional adsorbents,the novel materials have the advantages of high efficiency and fast reaction.This study provides theoretical support and technical guidance for the practical application of groundwater fluoride removal technology.