ABSTRACT
This research has designed innovative Ag/TiO(2) polysiloxane-shield nano-reactors on the PET fabric to develop novel durable bio-photocatalyst purifiers. To create these very fine nano-reactors, oppositely surface charged multiple size nanoparticles have been applied accompanied with a crosslinkable amino-functionalized polysiloxane (XPs) emulsion. Investigation of photocatalytic dye decolorization efficiency revealed a non-heterogeneous mechanism including an accelerated degradation of entrapped dye molecules into the structural polysiloxane-shield nano-reactors. In fact, dye molecules can be adsorbed by both Ag and XPs due to their electrostatic interactions and/or even via forming a complex with them especially with silver NPs. The absorbed dye and active oxygen species generated by TiO(2) were entrapped by polysiloxane shelter and the presence of silver nanoparticles further attract the negative oxygen species closer to the adsorbed dye molecules. In this way, the dye molecules are in close contact with concentrated active oxygen species into the created nano-reactors. This provides an accelerated degradation of dye molecules. This non-heterogeneous mechanism has been detected on the sample containing all of the three components. Increasing the concentration of Ag and XPs accelerated the second step beginning with an enhanced rate. Further, the treated samples also showed an excellent antibacterial activity.
Subject(s)
Coloring Agents/chemistry , Siloxanes/chemistry , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Bacteria/drug effects , Catalysis , Coloring Agents/isolation & purification , Cross-Linking Reagents , Hydrogen Peroxide/chemistry , Kinetics , Microbial Sensitivity Tests , Nanoparticles , Nanotechnology , Oxidants/chemistry , Particle Size , Photochemistry , Silver/chemistry , Titanium/chemistry , X-Ray DiffractionABSTRACT
Biofilters with long lifetime and high storage stability are very important for bioremediation processes to ensure the readiness at the occurrence of sudden contaminations. By using the freeze-gelation technique, living cells can be immobilized within a mechanically and chemically stable ceramic-like matrix. Due to a freeze-drying step, the embedded microorganisms are converted into a preserved form. In that way, they can be stored under dry conditions, which comply better with storage, transport, and handling requirements. Thus, in contrast to other immobilization techniques, there is no need for storage in liquid or under humid atmosphere. The biological activity, mechanical strength, and the structure of the biologically active ceramic-like composites (biocers) produced by freeze gelation have been investigated by using the phenol-degrading bacteria Rhodococcus ruber as model organism. Samples of freeze-gelation biocers have been investigated after defined storage periods, demonstrating nearly unchanged mechanical strength of the immobilization matrix as well as good storage stability of the activity of the immobilized cells over several months of storage at 4 °C. Repeated-batch tests demonstrated further that the freeze-gelation biocers can be repeatedly used over a period of more than 12 months without losing its bioactivity. Thus, these results show that freeze-gelation biocers have high potential of being scaled up from laboratory test systems to applications in real environment because of their long bioactivity as well as mechanical stability.
