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Abstract: In the present review the percolative phenomena has been analyzed. Percolation is related to transport phenomena in microemulsions, in particular the electric charge transport. The influence of different additives upon electric percolation has been commented. The effects of the additives considered upon the microemulsion properties appear to come about through their association with the surfactant interface. The effects of these agents on the ease with which interdroplet channels allowing transfer of droplet contents are formed are not only responsible for their effects on percolation temperature, but also have serious implications for the rates of fast chemical reactions performed in microemulsions. Keywords: Microemulsion, Surfactants, Transport phenomena, Percolation, Aditives, Percolation Temperature.Download Full Article |
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Abstract: Nowadays, photocatalysis is being applied as a promising technique for decontamination, purification, deodorization, etc. of polluted air and wastewaters. This technique attempts also to generate renewable and non-polluting fuels utilizing various carbon and hydrogen sources. In this context, studies on photo-catalytic generation of H2 using 0.1% w/v TiO2 photo catalyst as a suspension in water was carried out using 350 nm light. This was explored further in presence of various metal ions such as Ag+, Cu2+, Fe2+, Au3+ and V5+ at different ambient such as air and CO2, in presence of a hole scavenger (2-propanol and formic acid). H2 yields in CO2-purged systems as analyzed in GC-TCD were reasonably higher, and increased further when metal ions were added into the systems. Based on H2 yields, HCOOH was found to be a more supportive hole scavenger as compared to 2-propanol in metal ions containing systems. Besides the formation of low to high concentrations of various gaseous products, nanoparticles of gold, silver and copper were also observed as photolysis products. This indicated that the presence of both reduced metal ions and their in-situ generated nanoparticles at various stages either in the free/unbound and/or associated with TiO2 photocatalyst in aqueous systems, together play a significant role in enhancing the H2 yields. Keywords: H2, TiO2, hole scavenger, photolysis, metal ions, nanoparticles.Download Full Article |
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Abstract: This work studies the use of olive oil mill waste (OMW) treated as subcritical or supercritical water to produce both, a biofuel by liquefaction and a gas fuel by gasification. The increasing amount of OMW, both liquid and solid, is becoming a serious environmental problem. This wastewater is highly resistant to biodegradation and contains a wide variety of compounds such as polyphenols, polyoils, organic acids, etc, that require depuration treatments to remove the odour and pollutant load before being discharged. This work studies both, liquefaction and gasification of OMW streams in subcritical and supercritical water in different batch reactors at temperatures between 200 and 530 ºC and pressures between 150 and 250 bar. This study also tests the effectiveness of various types of homogeneous (KOH 0.01 g/gsample dry) and heterogeneous catalysts (TiO2, V2O5 and Au-Pd 0.1-0.5 g/gsample dry) for supercritical water gasification (SCWG) and studied the way they affect biomass conversion yields. It also covers the effect that the use of different organic compound concentrations (23, 35, and 80 g O2/l of chemical oxygen demand concentration (COD)) and compositions (mixtures of solid and liquid OMW) has on energy production results. A maximum of 82% oil yield was obtained from the hydrothermal liquefaction of OMW under optimum conditions (330 ºC, 150 bar, 23 g O2/l as initial concentration and 30 minutes reaction time). Meanwhile, a yield of 88.6 mol H2/kgOMW dry was obtained when Au-Pd was used as a catalyst for the gasification of OMW supercritical water. Keywords: Gasification, liquefaction, supercritical water, subcritical water, olive mill wastewater, biofuel, gas fuel.Download Full Article |
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Abstract: In the present work, the effect of phenol on the supercritical extraction of the organic matter from Tarfaya's oil shale with toluene was evaluated. The experimental results showed clearly that phenol had a significant effect on the yield and the composition of the oils obtained. Moreover, it was shown that phenol was a very efficient modifier for oil shale, giving a good yield of recovery and a suitable maturation of the organic matter. The pitches prepared by mixing phenol and toluene contain more aromatics and have a high char yield at 950 °C compared to those obtained by extraction with supercritical toluene alone. Keywords: Oil shale, Supercritical extraction, Toluene, Phenol, Pitch.Download Full Article |
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Abstract: Photo-catalytic mineralization of eosin in aerated 0.1% (w/v) TiO2 suspended aqueous systems with and without Au3+using 350 nm photo light was carried out. Eosin mineralization rate was significantly faster in 2´10-4 M Au3+ containing systems in contrast to sole TiO2 systems, which is due to the participation of Au3+ and it’s in situ generated various reduced intermediates including gold nanoparticles during mineralization. Furthermore, pulse radiolysis (a well known transient measurement technique) was adopted to analyze the reaction intermediates (eosin-OH adducts and/or eosin radical cation) produced in mineralization by generating in situ ·OH and N3· species. The reaction rates for ·OH and N3· reactions with eosin evaluated respectively 5.4´109 and 3.0´109 dm3 mol-1 s-1 for the formation of radical cations were slower than the eosin-OH adduct formation rate (reaction rate = 1.4´1010 dm3 mol-1 s-1). Furthermore, it is proposed that the initially generated eosin-·OH/hole adduct is undergoing mineralization in the presence of air/oxygen. Keywords: TiO2, Photolysis, Au(III) ions, Eosin, Gold nanoparticles, Mineralization. |