Application of Photocatalytic Hollow Glass Microbeads in the Cleanup of Oil Spills

Abstract

Crude oil films on water are dissolved by photocatalytic oxidation. The photocatalyst, titanium dioxide, when excited by near-ultraviolet light, accelerates the oxidation of both the alipathic and the aromatic components of crude oil. The photocatalyst is maintained at the air-oil interface through attachment to sandlike ceramic microbeads that are hollow and buoyant. Experiments in the laboratory show that the near-ultraviolet solar irradiance is not rate limiting in the 25 to 50 W/m2 range. Thus the rate of cleanup is not expected to vary with season or latitude except in the Arctic winter. The projected cleanup times range from one week to several months. Times are shorter when larger amounts of beads are applied per barrel of oil and when the beads are smaller, more buoyant, or less aggregated by the oil. The rate of cleanup was found to be limited by oxygen mass transport and was accelerated by waves. Photocatalytic oxidation of crude oil, like natural noncatalytic oxidation, results in elimination of polycyclic aromatic hydrocarbons, some of which are carcinogens. Both the natural and the photocatalytic processes oxidize the aromatic hydrocarbons to phenols. However, the phenols are more rapidly eliminated in the photocatalytic reaction than they are in the natural photooxidation process.

Photocatalytic Degradation of Chlorinated Phenoxyacetic Acids by a New Buoyant Titania-Exfoliated Graphite Composite Photocatalyst

“…The activity saturation indicates full coverage of the particle surface by titania. Similar saturation of the photocatalytic activity at high titania coverage was observed for titania-coated glass beads . The data scattering for the titania-rich catalysts is ascribed to agglomeration of catalyst particles during the preparation step, which causes poor reproducibility.…”

“…Thus, to prevent loss of the titania and to concentrate the titania where it is most likely to be neededat the liquid−air interfacebuoyant catalysts are needed. Serpone and co-workers and Heller and co-workers , introduced the coated hollow glass beads, Dagan and Tomkiewicz proposed floating titania aerogels, and our group proposed methyl silicate floating composites …”

Fundamental Reactions in Illuminated Titanium Dioxide Nanocrystallite Layers Studied by Pulsed Laser

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The primary step in the reaction mechanism is the photogeneration of pairs of electrons and holes in the TiO 2 particles (reaction 1). Trapping of the electrons (reaction 2) and holes (reaction 3) occurs within less than 30 ps.…”

“…Interest in the detailed mechanism of illuminated TiO 2 reactions arises from the intensive use of aqueous TiO 2 in photocatalytic organic reactions and its application for complete mineralization of pollutants from wastewaters. − The primary step in the reaction mechanism is the photogeneration of pairs of electrons and holes in the TiO 2 particles (reaction 1). Trapping of the electrons (reaction 2) and holes (reaction 3) occurs within less than 30 ps. − Second-order decay in the picosecond time range has been attributed to fast electron−hole recombination at high laser intensities (reaction 4) .…”

Photocatalytic Dechlorination of Aqueous Carbon Tetrachloride Solutions in TiO2 Layer Systems: A Chain Reaction Mechanism

“…Interest in the detailed mechanism of illuminated TiO 2 reactions arises from the intensive use of aqueous TiO 2 in photocatalytic organic reactions and its application for detoxification of pollutants from wastewaters. − Considerable amount of work has been recently carried out on photocatalytic removal of chlorinated methane and other hydrocarbons, both in gas phase − and in solution. − Thermal catalysis of organic halogens in gas as well as liquid 39 phase has also been reported. These steady-state illumination studies of TiO 2 powders focused on product analysis at high light intensities and long illumination times, attempting to find the conditions for complete mineralization and the role of oxidative and reductive pathways and the role of additives.…”