| In this paper, nano-hydroxyapatite(HA) powders were prepared by the precipitation method. The adsorption property of HA for heavy metal ions Cu2+was systematic researched and compared with that of HA prepared by sol-gel method. The effect of the factors such as solution pH value, adsorption time, temperature, adsorbent ratio, initial concentration on the adsorption of HA for heavy metal ions was investigated. The adsorption isotherm was drawn. Chitosan(CS) and bovine hemoglobin(HB) were used to modify the HA by coprecipitation method and hydrothermal synthesis,respectively. The adsorption properties of the composites CS/HA and HB/HA were studied.The adsorption mechanism was explored.Ca(CH3COO)2and NaH2PO4were used as precursors and HA powders were prepared by the precipitation method. The as-prepared and annealed powders were characterized by differential thermal analyzer(DTA), X-ray diffractometer(XRD), Scanning Electron Microscope(SEM). The densities of the samples were measured by Archimedes principle. The results showed that the powders have uniform size particle distribution around1OOnm. Pure and well crystallized HA was obtained after annealing at the temperature of650℃and kept for2h.Using Cu(NO3)2solution as simulated heavy metals water pollution and investigates the adsorption property of HA, CS/HA and HB/HA were investigated using as show in the adsorption results the removal rate is84.96%under the temperature of25℃, pH=7. When the absorbent of5g/L was added to the Ca2+solution with an initial concentration of60mg/L after string for60min. The removal rate decreases with the increase of the initial concentration of Cu2+, while the adsorption capacity reveals an opposite tendency. The adsorption of HA for Cu2+is conform to the Langmuir adsorption equation. Contrast to the pure HA, two modified composites show higher adsorption abilities. And can remove the Cu2+quicker. Equilibrium absorption could be quickly reached within the initial30mins. The adsorption abilities of the two composites were compared. The adsorption capacity of HB/HA can reach to119mg/g of Cu2+, which is higher than that of CS/HA.The adsorption isotherms of the two composites were fitted by Langmuir equation and Freundlich equation, respectively. The results showed that the adsorption of HB/HA for Cu2+conforms to the Freundlich equation while the adsorption of CS/HA is well consistent with the Freundlich equation.First order, second order, Elovich and interparticle diffusion models were used to fit the adsorption results of two composites. It was shown that the adsorption of HA is fit to the second order kinetic equations and the process can be classed to two stages of fast surface adsorption and inter diffusion adsorption. |
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