Studies On The Recovery Of Serpentine Gangue-Preparation Of Magnesium Salt Whiskers

Magnesium salt whiskers, with mechanical properties of high strength elastic modulus and wear, are a promising intensifier of composite. Magnesium salt whiskers were prepared from Serpentine gangue and sodium hydroxide and sulfuric acid by hydrothermal synthesis in autoclave. Chemical analysis, transmission electron microscopy (TME),X-ray diffraction(XRD),differential thermal analysis-thermal gravity analysis(DTA-TG) were employed to test and analyze systematically the composition, and morphology of the products and preparation process.Firstly, the process of magnesium sulfate from the sulfuric acid leaching filtrate of serpentine is described. The effects of the gangue granularity, the temperature of the system, the heating time, the concentration of sulfuric acid, the ratio of liquid to solid on preparation of bitter salt are discussed. The results indicate that the best condition for the preparation of bitter salt is as follows: the gangue granularity of 100 mesh, reaction temperature of 70 ℃, the concentration of sulfuric acid of 40%, the ratio of liquid to solid of 3:1, and the ratio of acid to Serpentine gangue of 110%～ 120%.Secondly, Magnesium salt whiskers cloud be prepared from magnesium sulfate by hydrothermal synthesis. The effects of pH, the concentration, whisking, filling and the heating time are discussed. Furthermore, the course of whiskers growth was discussed.The results indicate that hydrothermal is a excellent method to synthesize Magnesium salt whiskers, whiskers gained by this method have the uniform sector morphology and stable properties, with 100μm in length, 0.5μm in diameter, 100～ 400 in length/diameter ratio. The products were of 152 type structure, which was denoted as MgSO₄·5Mg(OH)₂·2H₂O. The best condition for the preparation of whiskers is as follows: hydrothermal temperature of 160℃²00℃, the pressure of 304.0～890.6kPa, the whisking speed of 800r/min,and reaction time of 4 hours.The study indicates that it is feasible to utilize Serpentine gangue to Magnesium salt whiskers. And it provides a new approach for utilizing of Serpentine gangue and is of great interests for cost reduction.