The Preparation Of Calcium Oxide Nanoparticles With Controllable Morphology By Chitosan And Its Application In Defluorination

The element fluoride is needed by both humans and animals,but the ingestion of elevated fluoride concentrations via drinking water will cause a number of diseases,such as fetal cerebral function,neurotransmitter and dental/skeletal fluorosis.The adsorption process among various methods used for defluorination of water,offers not only satisfactory results but is widely used due to the advantage of low production cost,simplicity of design and operation.Chitosan,as the world's second largest rich polysaccharide,containing a lot of activity of amino and hydroxyl groups,has good biocompatibility and non-toxicity,which has more important role in the purification of water.It also could as the regulator for calcium-based minerals.Due to the relatively lower potential health risks as well as the good affinity for fluoride anion,calcium-based minerals have been widely carried out for the adsorption of fluoride.The improvement of adsorption capacity can be accomplished by regulation of particle size,shape and structure.Thus,here we report the controllable synthesis of petal-like nano-sheets of brushite by using chitosan??-chitosan and ?-chitosan?as the regulator.The main original conclusions of this work are drawn.?1?Due to the relatively lower potential health risks as well as the good affinity for fluoride anion,calcium-based minerals have been widely carried out for the adsorption of fluoride.The improvement of adsorption capacity can be accomplished by regulation of particle size,shape and structure.Thus,here we report the controllable synthesis of petal-like nanosheets of brushite by using chitosan as the regulator.The addition of chitosan polymer in calcium precursor not only could serve ideal nucleation sites but also could play a role in confining the calcium phosphate aggregates and thus controlling the size of the brushite flakes.When the concentration of chitosan was 0.01 wt%,the as-synthesized brushite showed nanosheet-structured with the dimensions ranged from 100 200 nm and displayed best fluoride adsorption capacity of 231.5 mg/g according to the fitted Langmuir model,which was comparatively higher than that of the previously reported calcium-based adsorbents.Moreover,the p H change and common co-existing anions such as Cl^-,NO_3-,SO₄^2- and HCO₃^- almost had no negative effect on F-adsorption while the co-existing of CO₃^2- obviously reduced the removal rate of F-in solution.We hope that this petal-like nanosheets based on green nanotechnology can help to achieve the goal of safe drinking water.?2?In this study,the nano composite of chitosan and phosphorite were synthesized by using CaCl₂ and NaH₂PO₄ as the precursor and chitosan as the regulator.The XRD,TEM and SEM analyses indicated that this nano composite was composed of brushite and monetite.Meanwhile,the defluorination performance of this novel adsorbent was evaluated.The results indicated that the nano composite which was prepared with 0.01 wt% ?-Chitosan showed the best F- adsorption efficiency.The removal rate of F-could achieve 99.3% at the concentration ranged 10 mg/L to 50 mg/L with 2 h.The sorption of fluoride ions to nano composite agreed well to the Langmuir adsorption model,and its maximum capacity was 123.67 mg/g.Additionally,this adsorbent could maintain high defluorination efficiency in a wide p H range from 3 to 10.The co-existing ions of Cl^-,NO_3-,SO₄^2-,HCO₃^- and CO₃^2- almost had no negative effect on Fadsorption.Overall,the results reported herein indicated that this nano composite with high adsorption efficiency and health safety is very attractive and implies a potential of practical application for F-removal in drinking water.Chitosan could control the morphology of brushite.Petal-like nanosheets of brushite was synthesized by ?-chitosan as the regulator,while brushite and monetite were synthesized by ?-chitosan,and Petal-like structure of brushite had a bigger capacity.