title: Degradation of pentachlorophenol by a novel peroxidase-catalyzed process in the presence of reduced nicotinamide adenine dinucleotide.
abstract: A novel horseradish peroxidase (HRP)-catalyzed H₂O₂ process in the presence of reduced nicotinamide adenine dinucleotide (NADH) was applied to remove aqueous pentachlorophenol (PCP). Parameters (pH, H₂O₂ concentration, HRP activity and NADH dosage) on PCP removal were investigated. It was found that initial 0.05mM PCP was removed by 98% in HRP-NADH-H₂O₂ system at pH 5.0 and 30°C for 1h. Addition of O₂ in HRP-NADH-H₂O₂ system enhanced the removal rate of PCP due to promoting hydroxyl radicals (.OH) and superoxide anion radical (.O₂⁻) generation, which were confirmed by electron paramagnetic resonance (EPR)-spin trapping method. PCP removal efficiency decreased when .O₂⁻ and H₂O₂ were scavenged by superoxide dismutase and catalase in HRP-NADH-O₂ system, indicating that .OH/.O₂⁻ played a great role in the degradation of PCP. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that octachlorinated dibenzodioxin (OCDD) in residual solution was reduced after treated by the HRP-NADH-O₂ process, resulting in lower toxicity of treated solution than conventional enzymatic process. Two enzymatic-catalysis pathways were proposed for PCP removal in HRP-NADH-H₂O₂/O₂ system: (i) OH/.O₂⁻ free radical oxidation (ii) conventional phenoxy polymerization.
authors.affiliation: School of Chemical Engineering and Technology, Tianjin University, Tianjin, PR China.
authors.forename: Haitao
authors.initials: H
authors.lastname: Li
authors.forename: Yuping
authors.initials: Y
authors.lastname: Li
authors.forename: Hongbin
authors.initials: H
authors.lastname: Cao
authors.forename: Xingang
authors.initials: X
authors.lastname: Li
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D004785:Environmental Pollutants / Q000737:chemistry; D052918:Environmental Restoration and Remediation / Q000379:methods; D006735:Horseradish Peroxidase / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D009243:NAD / Q000737:chemistry*; D010416:Pentachlorophenol / Q000737:chemistry*; D009195:Peroxidase / Q000737:chemistry*; D010575:Pesticides / Q000737:chemistry*
chemical_list: D004785:Environmental Pollutants; D010575:Pesticides; D009243:NAD; D006861:Hydrogen Peroxide; D010416:Pentachlorophenol; D006735:Horseradish Peroxidase; D009195:Peroxidase