Clean technology recovery

To be used as photocatalysts, especially in the so-called clean technologies, active materials must fulfill the following requirements (1) very low toxicity, (2) resistance to photo-corrosion, (3) high availability, (4) high catalytic efficiency, and (5) low cost. From all the materials cited above, titanium dioxide and its derivatives seem to offer the best answer to these requirements, being by far the most commonly utilized photocatalysts. To be used in gas-phase photocatalysis, in addition to the above requirements, two other conditions are still necessary, that is, a very small pressure drop and an easy recovery. 

The green chemistry advantages of using triflates are not only that it helps avoid the use of hazardous catalysts, but also that the triflates themselves can be recovered and reused rather easily. In one series of reactions involving the reaction between phenethyl alcohol and acetic acid, for example, Barrett s team found that yields of 95-98 percent were possible, with catalyst recovery amounting to no less than 98 percent and, in most cases, nearly 100 percent. The team concluded one of their reports on the use of triflate catalysts by suggesting that the catalysts they used were "readily recyclable and we believe this to be a major step forward in the area of clean technology for aromatic nitration (Francis J. Waller, et ah, "Lanthanide(III)... 

This chapter ends with a brief survey of efforts to extend asymmetric hydrogenation by operating in defined phases, unusual media, at surfaces or on soHd supports. In part, this chemistry is driven by the demands for clean technology in fine chemicals manufacturing the absence of solvent waste is an attractive goal. In addition, commercial considerations dictate that soluble metal catalysts should not contaminate the product. The operational criterion for impurity control is often delectabihty, and hence improvements in analytical techniques serve to increase the demand for complete catalyst recovery. The rarely reaUzed prospect of a recyclable asymmetric catalyst serves to provide a further stimulus to developments in this area. 

Electrochemistry can also be used in a variety of other clean technologies, including separations by electrodialysis, recovery of metal ions from waste streams, and destruction of cyanide ion and organic compounds in waste streams.436... 

Technologies to minimize resource consumption, to promote waste recovery and to develop clean processes and products... 

The bottom water recovery system uses existing wells or new wells to create the water recovery system for removal of the water used to wash the contaminated soil. Reverse leaching or soil washing can be conducted by controlling the water levels within the tank. This design minimizes the volume of clean ex situ water entering the system for treatment. Extremely dense clays may be difficult to treat with this technology. 

For practitioners of in situ technologies, note that U.S. EPA has issued a policy statement that reinjection of contaminated groundwater is allowed under Resource Conservation and Recovery Act (RCRA)35 36 as long as certain conditions are met. This policy is intended to apply to remedies involving in situ bioremediation and other forms of in situ treatment. Under this policy, groundwater may be reinjected if it is treated aboveground prior to reinjection. Treatment may be by a pump-and-treat system or by the addition of amendments meant to facilitate subsurface treatment. Also, the treatment must be intended to substantially reduce hazardous constituents in the groundwater (either before or after reinjection) the cleanup must be protective of human health and the environment and the injection must be part of a response action intended to clean up the environment.37... 

The C02 gas quality has significant impact on the capture cost by this technology, and uncertainties on the future regulatory requirements of C02 quality for its transport and storage has influence on the process configuration of the oxy-combustion plant, gas cleaning unit performance, overall C02 recovery capacity and on the energy requirements for C02 compression and purification. 

Direct or technology use use of C02 with different technologies and market applications such as use for oil recovery, for dry cleaning, waste carbonation, food, water treatment or extraction with supercritical C02 compounds, including others. 

Gas-to-liquid technology is at the same time an economically viable option for the recovery of stranded gas and an option to produce clean fuels or chemical feedstocks. Besides the financial incentive to monetise otherwise worthless gas, GTL has received added impetus in recent years, especially with regard to diesel fuel also, the trend in industrialised nations to reduce sulphur and particle contents in fuels is likely to accelerate. However, GTL competes with LNG for reserves of inexpensive, stranded natural gas further declines in LNG supply costs could undermine the attraction of GTL. The future of GTL further hinges on the reduction of... 

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