Peroxidase catalyzed co-polymerization of pentachlorophenol and a potential humic precursor

The transformation of xenobiotics in the soil was studied in a model experimental system using pentachlorophenol (PCP), an enzyme, and a potential humic precursor. It has been shown that potential humic precursors such as p-coumaric acid greatly accelerated the peroxidase-catalyzed reaction of PCP (Morimoto K. and Tatsumi K, 1997. Effect of humic substances on the enzymatic formation of OCDD from PCP. Chemosphere 34, 1277–1283). About 90% of the PCP reacted but almost no transformation products were detected by GC/MS analysis. Most of the transformed PCP was detected in the polymeric products by the determination of the adsorbable organic halide (AOX) in gel permeation chromatography (GPC) fractions. Pyrolysis gas chromatography/mass spectrometry (py-GC/MS) of the polymers showed that tetrachlorophenol (TeCP) was the major pyrolysis product. This accords with the ion chromatography observation that about 20% of the PCP chlorine was released as chloride ion. However, nitrobenzene oxidation produced only a small amount of PCP and no TeCP. Based on the selectivity of the two degradation methods, it is concluded that TeCP is bound to the polymer by a diphenylether linkage, and PCP by an ether linkage to the aliphatic side chain. Thus, it was concluded that the major part of the PCP was incorporated into the polymer from p-coumaric acid by the release of a chlorine atom from the PCP molecule to form a diphenylether linkage with the p-hydroxyl group of the p-coumaric acid polymer.