More than 85% of 10 mg L-1 of pentachlorophenol (PCP) was removed by magnesium/silver (206/1.47 mM) bimetal system in the presence of acetic acid. Dechlorination was found to be sequential and phenol was identified as the ultimate hydrocarbon skeleton along with some accumulation of tetra-, tri-, and dichlorophenols. The dechlorination reaction was found to follow second-order kinetics. Lower PCP removal efficiency (35%) was observed when the reaction was carried out in the absence of acid using Mg-0/Ag system. When the reaction was conducted using Mg-0 alone in the presence of acid, substantial sorption Of PCP Occurred with very low efficiency of PCP dechlorination. Dechlorination studies on 10 mg L-1 initial concentrations of 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and 2,4,5-trichlorophenol (2,4,5-TCP), under identical conditions as to PCP, revealed that dechlorination efficiency and reaction rate constants decrease with decreasing number of chlorine atoms on the target compound. A correlation (R-2 > 0.9) between the dechlorination rate constants and E-LUMO for chlorophenols was obtained. (c) 2006 Elsevier Inc. All rights reserved.