No abstract

This paper describes a new concept of dense, dual-phase membrane consisting of two phases conducting, respectively, CO 3 2and electrons for selective permeation of CO 2 and O 2 at high temperatures. Membranes with a molten carbonate phase in a porous stainless-steel support were synthesized by a direct infiltration method. Membrane preparation conditions were optimized to obtain stable, gas-tight dual-phase membranes at high temperatures (>450 °C). The dual-phase membranes exhibit low single-gas permeance for pure CO 2 and N 2 (<5 × 10 -9 mol s -1 m -2 Pa -1 ) in 450-650 °C but substantially higher CO 2 permeance for CO 2 mixed with O 2 at high temperatures. CO 2 , after interacting with O 2 , transports through the molten carbonate phase in a form of CO 3 2-, with electrons transporting through the porous metal support. With further improvement, the dual-phase membranes may offer application in producing O 2 -enriched CO 2 streams for the oxyfuel combustion process. The concept can be also extended to prepare CO 2 perm-selective dense membranes for high-temperature CO 2 separation.

Photocatalytic activity of Ag/TiO(2) composites obtained by photoreduction treatment (PRT) was investigated. The composite materials, containing various ratio of silver nanoparticles (0.6-3.7 wt %) were obtained by depositing silver on the Evonic-Degussa P25 titania surface. Selected samples whose color varied between light rose and purple brown were examined by SEM, TEM, XPS, DRS, and BET techniques. Flat band potential was determined using Roy method. TEM analysis showed spherically shaped silver nanoparticles of the diameter 4-12 nm. The XPS measurements revealed that silver particles were obtained mainly in metallic form. DRS spectra and photovoltage measurements showed that silver nanoparticles modified the P25 spectral properties but they changed neither the band gap nor the location of flat band potential. The photocatalytic activity of Ag/P25 composite was compared to the photocatalytic activity of pure P25 in the photooxidation reaction of an important potable water contaminant humic acid (HA) and two model compounds, oxalic acid (OxA) and formic acid (FA). The photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that a small amount of silver nanoparticles deposited on the titania surface triggers the increase in photocatalytic activity; this increase depends, however, on the decomposed substance.