In recent years, problems related to soil contaminated with polychlorinated biphenyls (PCB) have been increasing. Toshiba Corporation of Japan has developed a technology, called geosteam technology, for the remediation of PCB-contaminated soil. This technology achieves the dependable destruction of PCBs by a chemical reaction using steam.

After a step-by-step verification of this technology through tests, Term Corporation, in co-operation with Toshiba and Konoike Construction Co. Ltd., has constructed Japans first commercial plant for remediation of PCB-contaminated soil in Kitakyushu City. Contact: Technology Planning Division, Toshiba Corporation, 1-1, Shibaura 1-chome, Minato-ku, Tokyo 105-8001, Japan. E-mail: review@toshiba.co.jp.

Source: www.toshiba.co.jp

Researchers from Queens University, Canada, have assessed the feasibility of a two-step treatment process for the remediation of soil contaminated with a model mixture of polycyclic aromatic hydrocarbons (PAHs): phenanthrene, pyrene and fluoranthene.

The initial step of the process involved contacting contaminated soil with thermoplastic polymeric pellets (polyurethane). The ability of three different mobilizing agents water, Biosolve surfactant and isopropyl alcohol to enhance recovery of PAHs from soil was investigated, and the results were compared with the recovery of PAHs from dry soil. The presence of isopropyl alcohol had the greatest effect on PAH recovery, with absorption of about 80 per cent of the original mass of PAHs in the soil by the polymer pellets in 48 hours.

The second stage of the treatment involved regeneration of the PAH-loaded polymers via PAH biodegradation, which was carried out in a solid/liquid two-phase partitioning bioreactor. In addition to the PAH-containing polymer pellets, the bioreactor also contained a microbial consortium that was pre-selected for its ability to degrade the model PAHs. After 14 days, 78, 62 and 36 per cent of phenanthrene, pyrene and fluoranthene, respectively, had been desorbed from the polymer and degraded. The rate of phenanthrene degradation was limited by mass transfer of phenanthrene from the polymer pellets. A combination of mass transfer and biodegradation rate might have been limiting for pyrene and fluoranthene.

Source: www.clu-in.org

Australian scientists have developed a new technology that can easily break down recalcitrant chlorinated hydrocarbons (CHC) on site. Our technology is based on the use of granulated activated carbon which, together with a common solvent and an electron enhancer, helps hydrogen turn a CHC into a hydrocarbon and salt, thereby converting a harmful compound into harmless ones, said Dr. David Garman, Executive Director of Environmental Biotechnology CRC (EBCRC).

The novel process, developed by EBCRC researchers, mimics a biological process by using molecules to assist with reactions that would not occur under normal conditions. It permits the re-use of activated granulated carbon used to remove and breakdown CHCs. A biologically based compound, such as a vitamin, is added to assist inorganic reduction of CHCs.

The process regenerates activated granulated carbon by solubilizing the bound halogenated hydrocarbons to a gas and a liquid that will allow their safe destruction. The activated carbon is then recycled for reuse or disposed of as a low impact waste. Contact: Environmental Biotechnology CRC, Australian Technology Park, Locomotive Workshop, Suite 3010, Eveleigh, NSW 2015, Australia. Tel: +61 (2) 9209 4970; Fax: +61 (2) 9209 4980; E-mail ebcrc@ ebcrc.com.au.

Source: www.sciencealert.com.au

In the United States, UOP LLC and three inventors Mr. Leon Yuan, Mr. Steven M. Poklop and Mr. William D. Schleter have patented a process for removing dioxin and furan from a vent stream of facilities such as a refinery or a petrochemical production facility. The process can include: (a) passing a first stream from a catalyst regeneration zone, comprising halogen and at least a dioxin and a furan, through a halogen removal zone, comprising an adsorbent to adsorb at least one halogen; and (b) combining the first stream from the halogen removal zone with a second stream from a heater from the catalyst regeneration zone, and obtain a combined stream at a temperature of above 150C and an oxygen content no less than 1 per cent.

Generally, a refinery or petrochemical production facility includes: (a) a catalyst regeneration zone; (b) a halogen removal zone; and (c) an elimination zone for at least one dioxin or a furan compound. An ef-fluent from the halogen removal zone can be combined with an air stream from the regeneration zone or halogen removal zone. Thus, the system permits the combination of a vent gas stream that can have insufficient temperature and oxygen to an existing process stream that provides sufficient heat and oxygen, so that the operating conditions are sufficient to catalytically destroy dioxins and furans.

The system permits changing the temperature and oxygen content of the gas stream coming into the elimination zone without the expense for an additional heater. Should the throughput through the heater for the drying zone be reduced due to required regeneration conditions, the invention can improve existing heater operations by increasing the total throughput through the heater. Contact: UOP LLC, 25 East Algonquin Road, P.O. Box 5017, Des Plaines, Illinois 60017-5017, United States of America.


Source : www.wipo.int

Researchers at METEA Research Centre, Italy, have investigated a combined technology for the remediation of polychlorinated biphenyls (PCBs) in soil employing thermal desorption coupled with catalytic hydrogenation of recovered PCBs. The reactor employed was a bench-scale rotating desorption furnace through which nitrogen was flushed and used as carrier gas of desorbed PCBs. The desorbed PCBs were condensed into a hexane-acetone (1:1 v/v) or hexane solution, which was then hydrogenated using as catalyst phosphate-supported palladium or rhodium.

Analysis of the treated soil under variable operating conditions of temperature and desorption time showed a nearly total (99.8 per cent) removal of PCBs. The recovery yield of the desorbed PCBs was better than 75 per cent, and the subsequent hydrogenation reached 63 per cent of the collected PCBs in 5 hours or 100 per cent in 12 hours.


Source: www.clu-in.org

Chlorinated benzene, particularly 1,2-dichlorobenzene (1,2-DCB), has been widely used as one of surrogate compounds of dioxin to find the noble methods to control dioxin. However, the relationship between the catalytic activity of dioxin surrogate compound and dioxin has not been understood well. Mr. Jung Eun Lee and Mr. Jongsoo Jurng from the Centre for Environmental Technology Research, Korea Institute of Science and Technology (KIST), Republic of Korea, used a vanadium based catalyst (V₂O5/TiO₂) to compare catalytic activity of chlorinated benzenes and dibenzo-p-dioxins with low-chlorine content using the lab-scale system.

The researchers studied the catalytic conversions of low-chlorinated dioxins, [2-monochlorodibenzo-p-dioxin (2-MCDD), 2,3-dichlorodibenzo-p-dioxin (2,3-DCDD)] and polychlorinated benzenes [1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB), pentachlorobenzene (PeCB), 1,2-DCB, hexachlorobenzene (HCB)] using a V₂O5/TiO₂ catalyst to understand quantitative relationship between dioxin and benzene with the chlorination level. The catalytic decomposition of chlorinated aromatic compounds was 1,2-DCB > 1,2,3,4-TeCB > 2-MCDD > PeCB = 2,3-DCDD > HCB. It might be more reasonable that PeCB or HCB be used as the dioxin surrogate compound rather than 1,2-DCB.

The researchers also investigated the effect of both oxygen content and space velocity (SV) on the catalytic decomposition of 1,2-DCB in the presence of the catalyst because these factors should be considered significantly in combustion facilities to control various pollutants. The decomposition of 1,2-DCB shows dependency on SV while the effect of oxygen content on the catalytic decomposition is negligible in the range of 5-20 per cent. Contact: Mr. Jongsoo Jurng, Centre for Environmental Technology Research, Korea Institute of Science and Technology (KIST), 39-1 Hawolgok, Seongbuk, Seoul 130-791, Republic of Korea.

Source: www.springerlink.com