ABSTRACT
The important properties in the development of adsorbents for uranium extraction from seawater include specific selectivity to uranium ions and anti-biofouling ability in the ocean environment. In this paper, we report a novel strategy for efficient selective extraction of uranium from aqueous solutions and good anti-bacterial properties by surface ion-imprinted zeolite molecular sieves. Guanidine-modified zeolite molecular sieves 13X (ZMS-G) were synthesized and used as the support for the preparation of uranium(vi) ion-imprinted adsorbents (IIZMS-G) by ligands with phosphonic groups. The prepared IIZMS-G adsorbent was characterized via Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The results showed that guanidine groups have been successfully introduced onto the support while its morphology structure was maintained. The adsorption performance and selectivity to U(vi) ions, antibacterial property, and reusability of IIZMS-G were evaluated. The results showed that the maximum adsorption capacity reached 141.09 mg g-1 when the initial concentration of metal ions was 50 mg L-1 at pH 6 and 20 °C. The adsorption process followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. The IIZMS-G exhibits an efficient selective adsorption of U(vi) ions from aqueous solutions with competing ions. In addition, the IIZMS-G exhibited excellent inhibitory effects on Escherichia coli and Staphylococcus aureus, and the inhibitory rate was 99.99% and 98.96% respectively. These results suggest that the prepared IIZMS-G adsorbent may promote the development strategy of novel high selectivity and antifouling adsorbents for uranium recovery from seawater.
ABSTRACT
Candida rugosa lipases were immobilized onto collagen fibers through glutaraldehyde cross-linking method. The immobilization process has been optimized. Under the optimal immobilization conditions, the activity of the collagen-immobilized lipase reached 340 U/g. The activity was recovered of 28.3 % by immobilization. The operational stability of the obtained collagen-immobilized lipase for hydrolysis of olive oil emulsion was determined. The collagen-immobilized lipase showed good tolerance to temperature and pH variations in comparison to free lipase. The collagen-immobilized lipase was also applied as biocatalyst for synthesis of butyl butyrate from butyric acid and 1-butanol in n-hexane. The conversion yield was 94 % at the optimal conditions. Of its initial activity, 64 % was retained after 5 cycles for synthesizing butyl butyrate in n-hexane.
