Treatment System for Soil Polluted by VCOCs Utilizing Photocatalysis

三氯乙烯(TCE)、四氯乙烯(PCE)等挥发性氯化有机化合物(VCOCs)被广泛用作干洗衣物、清洗半导体等的溶剂。它们已经失去了控制，造成了土壤和地下水的污染。这些污染是严重的环境问题，因为这些化学物质是致癌和有毒的。我们设计并提出了一种利用“TiO2光催化片”处理VCOCs污染土壤的系统。该片材由二氧化钛粉末和吸附剂(活性碳)组成。该吸附剂不仅能捕获从土壤中蒸发出来的VCOCs，还能捕获光气和二氯乙酰氯(DCAC)等有害中间体。利用二氧化钛光催化降解气相中的三氯乙烯，对该体系进行了研究。一块地是旧厂址，另一块地是一家活跃的清洁车间。被污染的…老厂址内更多的土壤被掺入热土(CaO)以挥发化学物质(PCE)，光触媒薄片覆盖在土壤上。由于状态已经保持了三个星期，在此期间光触媒薄片一直受到太阳光的照射。土壤气相中的PCE浓度在最初的两天内急剧下降，七天后低于可检测的下限。土壤中PCE浓度也低于0.01 mg/L，为日本环境限量。另一种主动清洗车间地下污染土壤的处理系统是通过真空排气装置从污染土壤中抽吸处理VCOCs气体。吸入的气体被引导到具有光催化片的吸附装置。当被VCOCs气体饱和的床单，我们将其挂在太阳光下，并在设备中重复使用。实际应用结果表明，采用光触媒和太阳光相结合的系统对VCOCs污染土壤的处理是有效的。较少

Volatile chlorinated organic compounds (VCOCs) such as trichloroethylene (TCE) and tetrachloroethylene (PCE) have been widely used as solvent for dry cleaning of clothes, washing of semiconductors, and so on. They have been disposed out of control, causing the soil and groundwater pollutions. These pollutions are serious environmental problems because these chemicals are carcinogenic and toxic. We have designed and proposed a treatment system for soil polluted by VCOCs utilizing "TiO_2 photocatalyst sheets". The sheet consists of TiO_2 powder and adsorbent (activated carbon). The adsorbent traps VCOCs evaporated from the soil and also traps undesirable intermediates such as phosgene and dichloroacetyl chloride (DCAC) observed by TiO_2-mediated photocatalytic degradation of TCE in gas phase.The system utilizing the photocatalyst sheets and solar light was investigated in the actual polluted field. One field was an old factory site, and the other was an active cleaning shop. The polluted … More soil in the old factory site was mixed with "Hotsoil (CaO)" to volatilize the chemicals (PCE), and the photocatalyst sheets were covered over the soil. As the status has been kept for three weeks, the photocatalyst sheets have illuminated by solar light for the period. PCE concentrations in gas phase of the soil decreased drastically for initial two days, and they were below detectable limit after seven days. The PCE concentrations in the soil were also below 0.01 mg/L whose concentration is Japan's environmental limit of PCE. The other system to treat the polluted soil under the ground in the active cleaning shop was an aspiration treatment of VCOCs gases from the polluted soil through the well by vacuum pomp. The aspirated gases were led to an adsorption device having the photocatalytic sheets. When the sheets saturated by VCOCs gas, we hanged out the sheets under solar light and reused them in the device. The results in the actual fields show that the system using photocatalyst sheets and solar light is effective on the treatment of the soil polluted by VCOCs. Less