Comparative study for the removal and destruction of pentachlorophenol using activated magnesium treatment systems

Chlorophenols are highly toxic, environmentally-persistent compounds which have been classified as probable human carcinogens by the United States Environmental Protection Agency. Due to the high toxicity of these compounds, it is necessary to treat water and soils with concentrations of chlorophenols above the detection limit set by regulatory agencies. The aim of this work is to demonstrate the capabilities of using ball-milled magnesium for the dechlorination of PCP. Comparison of dechlorination processes were performed in an attempt to determine the most effective system for degradation of PCP to phenol. Three systems with powerful capabilities of treatment were studied: ball-milled zero-valent magnesium (ZVMg), ball-milled zero-valent magnesium carbon (ZVMg/C), and ball-milled zero-valent magnesium with palladium (ZVMg/Pd). In addition to measuring PCP disappearance, all byproducts were identified and quantified for each degradation system. The results of these studies indicate that all three of the systems degrade PCP within 30 min. The most rapid and complete PCP dechlorination is achieved using ball-milled Mg/Pd and a matrix consisting of at least 0.02 g Mg0/mL ethanol, and 10 μL acetic acid/mL ethanol, in which case 20 ng/μL of PCP was dechlorinated to chlorophenols in approximately 15 min with complete dechlorination achieved in six days. Carbon mass balances of 90.16% for Mg, 94.76% (Mg/C) and 97.05% (Mg/Pd) verify dechlorination was responsible for declining concentrations of PCP. The reactions of PCP degradation and phenol formation were found to follow pseudo-first order kinetics for all systems. Further work will consist of optimization and development of field-scale applications.