Decontamination of water using adsorption and photocatalysis

A treatment strategy employing adsorption and solar assisted photocatalytic processes was field tested at Tyndall Air Force Base (Florida) for removal and destruction of organic contaminants in groundwater. The adsorbents were impregnated with photoactive catalysts and used in packed beds to remove pollutants from water for 18 h per day. The spent adsorbents were regenerated for 6 h per day in the presence of sunlight while passing hot water (90°C) counter current to flow direction during the adsorption process. The organics that were not destroyed during regeneration by the catalyst-impregnated adsorbent were destroyed using a fixed bed photocatalytic reactor. The process was examined for 10 cycles of adsorption and regeneration for treatment of water contaminated with BTEX (benzene, toluene, ethyl benzene, o-xylene, m-xylene, and p-xylene) compounds. The efficiency (ratio of amount of organics removed to amount of organics adsorbed) of the process to regenerate the adsorbents was examined for each cycle. A laboratory study was also conducted under controlled conditions using tetrachloroethylene as a model compound to examine the regeneration efficiency for 8 cycles of adsorption and regeneration.