SBIR-STTR Award

The use of solar and/or artificially irradiated semiconductor powders to photocatalytically mineralize 12-400 ppm trichloroethylene (TCE) contaminated water obtained from a candidate Superfund site is proposed. These semiconductor powders are inexpensive, nontoxic, recyclable and have been successfully employed to mineralize TCE, pentachlorophenol and many other halogenated hydrocarbons rapidly. The studies performed to date have almost exclusively used purified water spiked with the toxicant to be decomposed. However, water obtained from a Superfund site contains other contaminants and minerals, together with pH and turbidity factors that are impossible to duplicate in the laboratory. This poses a significant challenge to the photocatalytic system's ability to destroy the targeted contaminants. The successful decomposition of TCE in this water will represent an important extension of photocatalytic water purification from the laboratory into the field. This Phase I effort will lay the groundwork for the Phase II design of an on-site, prototypical outdoor photocatalytic reactor for water purification at a Superfund site.

Trichlorethylene (TCE) is the most frequently found contaminant at National Priority List (NPL) Sites. In the Phase I investigation, the rapid destruction of 100 ppm TCE in waters derived from sampling wells of a Superfund Site was demonstrated utilizing the equivalent UV radiation present at one Sun intensity. In one of the waters, TCE destruction was anomalously slow and photocatalyst deactivation was premature. This was attributed to the photoelectroplating of chromium or heavy metals onto the photocatalyst powder. This effect can be used to advantage for the removal of toxic metal ions and organics from water. The proposed Phase II study will comprehensively investigate the photocatalytic decomposition of various concentrations of TCE in the presence of the Metal ions Pb+2, Cd+2, Cu+2, Hg+.2, Cr+6, Cr+3, Fe+2, and Fe+3. These metals are found in the first 37 most frequent substances, out of 472 identified, at NPL sites. Various process strategies will be investigated for effecting the simultaneous or sequential removal of organic compounds and metal ions from contaminated waters at NPL Sites vis photocatalysis. The investigators expect to demonstrate and elucidate photocatalytic processes for the simultaneous and/or sequential removal of co-contaminants such as halocarbon and heavy metals from waters at Superfund Sites. This technology has the potential to destroy in situ, almost all aqueous organics and to remove heavy metals. Some of the commercial applications are in mitigating water pollution, purifying municipal and residential water supplies, and metals removal from mining activities. Federal government applications exist in the purification of waste-waters contaminated by nerve-agents, propellants, explosives, and radioactive metals.