ABSTRACT
Porous hydroxyapatite (HAP) nanoparticles with the specific surface area of 76.1 m2 g-1 were facilely prepared using calcium nitrate and phosphoric acid as the starting materials and ammonia aqueous solution as the pH regulator by a hybrid precipitation and hydrothermal method at lower reaction temperatures of 35 and 110 °C. The adsorption of Cr(III), Pb(II), and Cu(II) ions on HAP nanoparticles was well simulated by the pseudo-second-order adsorption kinetics and Langmuir adsorption isotherm. The maximum adsorption capacities of HAP nanoparticles for Cr(III), Pb(II), and Cu(II) ions were 96.9, 440.5, and 69.9 mg g-1, respectively, at 20 °C based on the Langmuir adsorption isotherms. The thermodynamic analysis revealed that the adsorption processes of Cr(III), Pb(II), and Cu(II) ions on HAP nanoparticles were spontaneous and endothermic.
ABSTRACT
Objective The aim of the study was to develop a kind of new fluoride composite resin .We explored the practica-bility of preparing fluorinated filler by using hollow silica microsphere as a carrier of sodium fluoride (NaF) as well as its fluoride-re-lease properties in composite resin . Methods Hollow silica microspheres with mesoporous shells were prepared by the sacrificial template method.NaF was loaded into hollow silica microspheres by the impregnation method .Scanning electron microscopy ( SEM) was used to determine the morphologies of hollow silica microspheres before and after NaF loading .Hollow nanosilica microsphere con-taining NaF and NaF powder were respectively mixed with resin at the same intial NaF concentration of 13.9, 27.8 and 55.6 mg/mL for comparison, which were taken as the experiment group and the control group .The samples were put into 100 mL artificial saliva at 37℃to caculate the cumulative fluoride release quantities from 1 d to 47 d.Results The morphology of hollow microsphere did not chang significantly before and after NaF loading .In the experiment group ,the cumulative quantities of fluoride release were 0.026, 0.105, 0.21 mg/cm 2on 1 d and increased to 0.088, 0.239, 0.484 mg/cm 2on 47 d according to respective initial NaF concentration . While in the control group, the corresponding figures were 0.006, 0.025, 0.04 mg/cm2on 1 d and 0.022, 0.045, 0.056 mg/cm2on 47 d.The difference between these two groups was of great statistical significance . Conclusion Hollow silica microsphere could be used as a carrier of NaF .Fluorinated nanosilica filler using hollow microsphere promotes the fluoride release in composite resin .