Papers by Author: He Bin Shi

Abstract: A middle grade siliceous phosphorite from Yunnan province was selected to treat Cd²⁺ bearing aqueous solutions. The siliceous phosphorite was tested by X-ray fluorescence spectrometer, X-ray diffraction, infrared spectrometer and scanning electron microscopy. The results present that the valuable mineral is nanostructured carbonated fluorapatite and the major gangue mineral is quartz. The amount of Cd²⁺ sorbed by the siliceous phosphorite tends to increase with the increase of initial pH or the initial Cd²⁺ concentration of the simulated waste water. The reaction process of Cd²⁺ removal from aqueous solutions is highly fitted with the pseudo-second order kinetic model. The results indicate that nanostructured carbonated fluorapatite bearing siliceous phosphorite can effectively immobilize aqueous Cd²⁺.

Abstract: This paper reports a novel coprecipitation process for the preparation of strontium-barium hydroxyapatite [Sr_5-xBa_x(PO₄)₃OH]. Strontium nitrate, barium nitrate and phosphoric acid were dissolved in water to form a homogeneous Sr-Ba-P aqueous solution. The samples were characterized by powder X ray diffraction, Fourier transformed infrared spectroscopy and scanning electron microscopy. The results showed that the barium phosphate [Ba₃(PO₄)₂] phase appeared at the samples prepared at the pH value lower than 12. A series of Sr_5-xBa_x(PO₄)₃OH samples had beenobtained by adding sodium hydroxide aqueous solution into the Sr-Ba-P solution to pH12.5 and following aging at 60 °C for 24h. The so-prepared samples are metallic cation-deficient hydroxyapatite solid solutions. The samples present low degree of crystallinity, irregular short rod-like morphology and nanometer size. The crystal cell parameters of Ca_5-xSr_x(PO₄)₃OH samples are nearly linear to their barium content, and their infrared absorption bands of PO₄^3- groups shift to lower wave numbers with the increase of the barium content.

Abstract: Calcium-strontium hydroxyapatite [Ca_5-xSr_x(PO₄)₃OH, Ca-SrHA] were prepared by a novel coprecipitation process. The homogeneous aqueous solution of calcium nitrate, strontium nitrate and phosphoric acid was used as starting material, and ammonia was used as precipitator. A series of Ca-SrHA samples had been synthesized by adding ammonia into the precursor solution to pH10 and following aging at 60°C for 18h. The samples were characterized by X-ray diffraction, Fourier transformed infrared spectroscopy and scanning electron microscopy. The results show that so-prepared samples present essential characteristics of Ca-SrHA. All samples have a short rod-like morphology. The cell parameters of Ca_5-xSr_x(PO₄)₃OH are linear to the value of x, and the infrared absorption bands of PO₄^3- groups shift to lower wave numbers with the increase of x.

Abstract: This paper reports synthesis of hydroxyapatite nanoparticles by three precipitation methods. Homogeneous aqueous solution of Ca(NO3)2 and H3PO4 was used as precursor solution, and NH3•H2O was precipitator. Calcium deficient hydroxyapatite nanorods were obtained by adding the precipitator into precursor solution, near stoichiometric hydroxyapatite nanoparticles were derived from adding precursor solution into the precipitator, and smaller hydroxyapatite nanoparticles were prepared by adding precipitator and precursor solution simultaneously into a reaction vessel. The stoichiometry of hydroxyapatite was mainly affected by pH at precipitation reaction process. The crystal size and shape of hydroxyapatite particles was related to Ostwald ripening. The stoichiometry and morphology of hydroxyapatite nanoparticles can be controllable by selecting suitable coprecipitation process.

Abstract: This paper presents a typical coprecipitation method to synthesize silicate-substituted calcium deficient hydroxyapatite (SiCDHA). A homogeneous aqueous solution of Ca(NO3)2• 4H2O, H3PO4 and Si(CH3CH2O)4 (TEOS) was used as precursor, and NH3 aqueous solution as precipitator. A series of samples were prepared by adding the precipitator to the precursor then following a general coprecipitation route. The results showed that the so-prepared samples were SiCDHA. SiCDHA was thermal unstable and decomposed to tricalcium phosphate and wollastonite-like phase. These new phases were helpful to improve the bioactivity of sintered SiCDHA ceramics.