Iron-mediated reactions of polychlorinated biphenyls in electrochemical peroxidation process (ECP).
A study was conducted to explore some of the basic processes of polychlorinated biphenyl (PCB) destruction by a new technology termed electrochemical peroxidation process (ECP). ECP represents an enhancement of the classic Fenton reaction (H2O2 + Fe2+) in which iron is electrochemically generated by steel electrodes. Focus was on the extent of adsorption of a mixture of Aroclor 1248 on steel electrodes in comparison to iron filings. Commercially available zero-valent iron filings rapidly adsorbed PCBs from an aqueous solution of Aroclor 1248. Within 4 h, all the PCBs were adsorbed at 1%, 5%, and 10% Fe0 (w/v) concentrations. Little difference in adsorption was found between acidic (2.3) and unamended solutions (pH 5.5), even though significant differences in iron oxidation state and Fe2+ concentrations were measured in solution. PCB adsorption also occurs on steel electrodes regardless of the pH or electric current applied (AC or DC), suggesting the combination of oxidizing (free radical-mediated reactions) and reducing (dechlorination reactions) iron-mediated degradation pathways may be possible. Extraction of the iron powder after 48 h of contact time yielded the progressive recovery of biphenyl with increasing Fe mass(from 0.4% to 3.5%) and changes of the PCB congener-specific pattern as a consequence of dechlorination. A variety of daughter congeners similar to those accumulated during anaerobic microbial dechlorination of Aroclor 1248 in contaminated sediments indicate preferential removal of meta- and para-chlorines.
Arienzo
M
M
Dipartimento di Scienze Chimico-Agrarie, Università degli Studi di Napoli Federico II, Italy. arienzo@katamail.com
Chiarenzelli
J
J
Scrudato
R
R
Pagano
J
J
Falanga
L
L
Connor
B
B
D000327:Adsorption; D004563:Electrochemistry; D004566:Electrodes; D004785:Environmental Pollutants / Q000032:analysis*; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D011078:Polychlorinated Biphenyls / Q000737:chemistry*
D004785:Environmental Pollutants; D016877:Oxidants; D006861:Hydrogen Peroxide; D011078:Polychlorinated Biphenyls; D007501:Iron