Silver coated anionic cellulose nanofiber composites for an efficient antimicrobial activity.

Herein, we report a comparative study of silver coated anionic cellulose nanocomposite before (CMC-Ag) and after (AgNPs/CMC) chemical reduction for antibacterial activity. Cellulose nanofibers were prepared by deacetylation of electrospun cellulose acetate nanofibers, which were then treated with sodium chloroacetate to prepare anionic cellulose nanofibers (CMC). Aqueous AgNO3 solution with different concentrations was employed to produce nanofiber composites. To obtain AgNPs/CMC, the resultant Ag/CMC nanofibers were chemically reduced with NaBH4. The nanocomposites were characterized by FE-SEM, FTIR, XPS and SEM-EDS. Antimicrobiality tests were conducted using S. aureus and Escherichia coli bacteria following standard test method JIS L1902, 2008. The EDS results confirmed higher silver content in CMC-Ag nanofibers than AgNPs/CMC nanofibers. The antimicrobial test and EDS results demonstrated higher silver release (larger halo width) by the former in comparison to later which confers better antimicrobiality by CMC-Ag nanofibers.

Mass transfer of trichloroethylene through the palladized iron coated reactive geomembrane.

Palladized iron coated reactive geomembrane (Pd/Fe RGM) was developed to mitigate the mass transfer of chlorinated volatile organic compounds through HDPE geomembrane. It had good performance in mitigating the mass transfer of TCE at the preliminary study. This study focused on the effects of Pd/Fe coating on the mass transfer parameters and the reaction rate constant of RGM. Also, the effects of sulfide and aging on the RGM were evaluated. It was proved that the effect of Pd/Fe coating on partition and diffusion coefficients of toluene was not significant by batch immersion test results with student's t-test. The reactivity of Pd/Fe RGM had a linear correlation with an increase in the Pd/Fe loading rate on RGM. However, it was lower than the reactivity of the Pd/Fe powder by a factor of one hundred because the effective surface area of Pd/Fe was blocked partially by the geomembrane and the opportunity to contact Pd/Fe and TCE was reduced. The reactivity of Pd/Fe RGM decreased severely at 10mM sulfide concentration and with long-term aging of RGM in the atmosphere for three years. However, the reactivity of aged RGM was recovered slightly by acid treatment, but not completely.