Papers by Author: Lei Yang

Abstract: In this paper, a novel and highly efficient hydroxyapatite (HA) carrier for cultivating hydrocarbon degradation bacteria (HDB) is introduced. The HA particles synthesized through a sol-gel method and different heat treatments were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET method. The microbial amount and activities of HDB cultivated on HA carriers were quantitatively investigated in order to assess their enriching capabilities. The results showed that HA synthesized at 550°C and the one without calcination could enrich HDB 3 and 2 magnitude orders more than the activated carbon, respectively. Mechanisms of bacterial enrichment on HA and activated carbon were also studied, and it is believed that the high bioactivity and the surface morphology of HA were responsible for the efficient reproduction of HDB. It is concluded that HA is a potential candidate to replace the conventionally used activated carbon as a novel carrier applied in the filed of bioremediation for oil contaminated soil.

Abstract: Stir-froth-polymerization is a novel technique for producing highly porous ceramics, in which bubbles are formed by a mechanical frothing in aqueous slurry of ceramic powders. Many work had be done about the porosity, the permeability and the mechanical strength of the porous ceramics derived from this method, but there are still a lot of things remain unclear. This paper focuses on the mechanism of frothing, and the influence of parameters in the mechanical frothing. It was found that the stir time, the stir speed and the viscosity of the slurry have influence on the average cell-size and the distribution of them respectively. The average cell-size can be controlled in the range from 60 to 160 μm by adjusting the parameters.

Abstract: Sol-gel method is one of the most potential techniques for mass-production of nano hydroxyapatite. In this paper, particle size control techniques, including dripping speed control, addition of several dispersants such as ammonium citrate, castor oil and silane coupling agent, as well as usage of insoluble and water soluble starch additives, were investigated. The particle size and microstructures of as synthesized hydroxyapatite were studied by X-ray diffraction, Scanning electron microscopy and dynamic light scattering. The results indicated that all the control techniques had considerable effects on decreasing the crystallite size, and the starch additives also exhibited obvious effect on preventing the agglomeration of nano crystallites during the synthesizing process.