Mechanism of the enhanced degradation of pentachlorophenol by ultrasound in the presence of elemental iron

Ultrasound combined with elemental iron (US/Fe-0) is effective in oxidizing organic contaminants in water. The sonolysis degradation of pentachlorophenol (PCP) was significantly enhanced by a factor of 4.2 with the addition of elemental iron, mainly via reaction with hydroxyl radicals ((OH)-O-center dot radicals), and the synergistic mechanism of the enhancement in the combined system was investigated. Experiments were performed with (1) sole ultrasonic treatment; (2) ultrasound in presence of iron; (3) ultrasound combined with copper powder as the same particle size as iron powder; (4) ultrasound in presence of Fe(II). It was observed that PCP degradation and (OH)-O-center dot radicals production were both enhanced in these combined methods, and the pitting on the sonicated iron surface was apparent. These results indicated that the rate enhancements in US/Fe-0 system were attributed to (1) the iron solid effect and the catalysis of Fe(II) produced from corroded-iron with promoting the production of (OH)-O-center dot radicals; (2) the increased surface area of iron particles by acoustic cavitation with promoting the adsorption process. (c) 2006 Elsevier B.V. All rights reserved.