Destruction of pentachlorophenol using glow discharge plasma process

Pentachlorophenol (PCP), found in wood preservatives and pesticides, is an acutely toxic recalcitrant organochlorine carcinogenic compound. A point-to -plane glow discharge plasma (GDP) process was used to study the destructio n of 30-50 ppm (120-188 mu M) sodium salt of pentachlorophenol (PCP) in an aqueous solution. PCP was converted to less than 10% of its initial concent ration in 1-3 h, at room temperature and low pressure (50 Torr). Effects of varying the headspace gas chemistry, stirring rate, pH, and current upon r ate of PCP conversion were investigated. Organic acids, including formate, acetate, butyrate, and oxalate, were formed as byproducts after 1-3 h of GD P treatment of PCP. The chloride recovery suggests 50-70% dechlorination. T he PCP removal rate exhibited mixed order kinetics. A reaction model develo ped to verify mixed order kinetics compares well with the experimental data . The increase in order may be due to the production and subsequent destruc tion of several reaction products throughout the process. An increase in cu rrent and stirring rate increased the rate of PCP removal in the GDP reacto r. However, the rate of PCP removal decreased when the initial pH of the so lution is raised to 11.4. Rapid removal of PCP was observed when the headsp ace gas was argon, air, or oxygen. Bench scale data was used to compare the power efficiency of the GDP process with atmospheric pressure corona disch arge, Results suggest that the cost of power for PCP conversion by glow dis charge was less than that of atmospheric pressure corona discharge. Additio nally, the operating cost for PCP destruction in aqueous solution using UV based advanced oxidation technologies was found to be comparable with power costs for PCP conversion using GDP.