Volatile chlorinated organic compounds (VCOCs) such as trichloroethylene (TCE) and tetrachloroethylene (PCE) have been indiscriminately disposed by the middle of the 1980’s, causing soil and groundwater pollution. We have designed a cleanup system for polluted soil utilizing "TiO₂ photocatalytic sheets" and solar light. In this paper, we report the constituents of the photocatalytic sheet to trap and decompose VCOCs from the soil, and a cleanup test utilizing the sheets in an actual polluted field.
The constituents of photocatalytic sheet were examined by evaluating photodecomposition activity of TCE and observing undesirable intermediates such as phosgene and chloroform released by the photodecomposition. First, the ratio of adsorbent (activated carbon) to TiO₂ powder was determined to decompose TCE completely as fast as possible without releasing the intermediates. Next, one activated carbon ("Small" in Fig) having main pore size of 1 nm was selected from the adsorption ability of TCE and the intermediates. Finally, photocatalytic sheet has been made of corrugated nonworen material containing both TiO₂ powder and the activated carbon, and the adsorption and photodecomposition activities of the sheets have been confirmed.
The VCOCs gases from actual polluted soil were extracted by the fan through the drilling well, and led to the photocatalytic sheets within the adsorption device. The sheets saturated with the gases were irradiated with solar light to renew and reuse. It was confirmed that the system using the photocatalytic sheets was effective in an actual polluted field of a cleaning shop.