Preparation Of Hydroxyapatite Coated Quartz Sands And Its Effect In Uranium Removal By PRB Technology

In this paper,hydroxyapatite coated quartz sands was prepared.The adsorbent was characterized by XRD,SEM,EDS and Zeta potential to study the structure and composition.Then the effect of pH value,dosages of composite material,contact time and initial U(Ⅵ)concentration on removal of U(Ⅵ)were investigated.In addition,adsorption isotherms and adsorption kinetics for each materials were studied.Finally,to confirm the best experimental condition,the factors of influence on removal of U(Ⅵ)were investigated by dynamic PRB column adsorption.And the Thomas model and Yoon-Nelson model were used to fit the experimental adsorption data.(1)Hydroxyapatite coated quartz sands was prepared by sol-gel method.The research shows the surface of absorbent is gray,and the adsorbent is porous with high specific surface area and better cover rate.(2)In the study of static adsorption experiment,the hydroxyapatite-coated quartz sands with three size of 0.15-0.3 mm,0.3-0.6 mm and 0.6-1.18 mm were prepared,and the U adsorption data fit Langmuir and Freundlich model,the removal of U fit pseudo-second-order kinetic equation.Under the condition of pH=4,contact time were 90 min,and initial U(Ⅵ)concentration were 3 mg/L,the U(Ⅵ)removal rate of 0.5 g(10 g/L),3 g(60 g/L),15 g(300 g/L)were 97.04%,98.27% and 97.04%,respectively.And their adsorption capacity were 0.29 mg/g,0.049 mg/g,0.0097 mg/g respectively.(3)Continuous PRB column studies showed that the particle size of quartz,the dosage of hydroxyapatite,the flow rate and initial U(Ⅵ)concentration have important influence on the adsorption capacity of composite material.On the condition that particle size of quartz varied from 0.6 to 1.18 mm,the ratio of quartz and hydroxyapatite is 0.0157,the flow rate is 6 mL/min,initial U(Ⅵ)concentration were 7 mg/L,and pH=4.01,the maximal U(Ⅵ)absorption capacity is 20.8 mg/g,the U removal efficiency is 67.6%.The Thomas and Yoon-Nelson models were good applied to the adsorption of U(Ⅵ).It provide dependable design data for practical application of Hydroxyapatite-coated quartz sands.