Ultraviolet reflector materials for solar detoxification of hazardous waste

摘要

Organic waste detoxification requires cleavage of carbon bonds. Such reactions can be photo- driven by light that is energetic enough to disrupt such bonds. Alternately, light can be used to activate catalyst materials, which in turn can break organic bonds. In either case, photons with wavelengths less than 400 nm are required. Because the terrestrial solar resource below 400 nm is so small (roughly 3% of the available spectrum), highly efficient optical concentrators are needed that can withstand outdoor service conditions. In the past, optical elements for solar application have been designed to prevent ultraviolet (UV) radiation from reaching the reflective layer to avoid the potentially harmful effects of such light on the collector materials themselves. This effectively forfeits the UV part of the spectrum in return for some measure of protection against optical degradation. To optimize the cost/performance benefit of photochemical reaction systems, optical materials must be developed that are not only highly efficient but also inherently stable against the radiation they are designed to concentrate. The requirements of UV optical elements in terms of appropriate spectral bands and level of reflectance are established based upon the needs of photochemical applications. Relevant literature on UV reflector materials is reviewed which, along with discussions with industrial contacts, allows the establishment of a database of currently available materials. Although a number of related technologies exist that require UV reflectors, to date little attention has been paid to achieving outdoor durability required for solar applications.