Dechlorination of chlorophenols by magnesium–silver bimetallic system

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 Mg0/Ag system. When the reaction was conducted using Mg0 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 (R2>0.9R2>0.9) between the dechlorination rate constants and ELUMOELUMO for chlorophenols was obtained.

Graphical abstractDechlorination of pentachlorophenol was achieved by Mg0/Ag system in the presence of acid. Dechlorination was sequential and phenol was identified as the product with accumulation of tetra-, tri-, and dichlorophenols.Figure optionsDownload full-size imageDownload as PowerPoint slide