Reductive destruction and decontamination of aqueous solutions of chlorinated antimicrobial agent using bimetallic systems.

Palladium, ruthenium and silver were investigated as catalysts for the dechlorination of dichlorophen (DCP, 2,2'-methylenebis(4-chlorophenol)), an antimicrobial and anthelmintic agent largely used as algicide, fungicide and bactericide. Experiments were undertaken under oxic and anoxic conditions for experimental durations up to 180 min (3h). The anoxic conditions were achieved by purging the solutions with nitrogen gas. Reactions were performed in a 12+/-0.5 mg L(-1) DCP solution (V=20 mL) using 0.8 g of Fe(0) (40 g L(-1)). Along with micrometric Fe(0), five Fe(0)-plated systems were investigated: Pd (1%), Ru (0.01%), Ru (0.1%), Ru (1%) and Ag (1%). Metal plating was controlled by atomic absorption spectroscopy. DCP degradation was monitored using: (i) two HPLC devices, (ii) ion chromatography, (iii) UV and fluorescence spectrophotometry. Results indicated: (i) total dechlorination with Fe/Pd, (ii) partial dechlorination (40%) with Fe/Ru, and no reaction with Fe/Ag. DCP is vanished completely after 90 min of contact with Fe/Pd following a first order kinetic. The observed degradation rate k(obs) was about (3.98+/-0.10)x10(-2)min(-1), the calculated half-life t(1/2) about 17.4+/-0.9 min and a t(50) about 10.1+/-0.5 min. A DCP degradation pathway map was also proposed.