Degradation of pentachlorophenol and 2,4-dichlorophenol by sequential visible-light driven photocatalysis and laccase catalysis.
Chlorophenols (CPs) can be degraded by visible-light driven photocatalysis or laccase catalysis. However, previous and present studies have shown that neither of the two methods was efficient when being used individually. Low degradation rates were observed for the degradation of pentachlorophenol (PCP) by laccase-catalysis and that of 2,4-dichlorophenol (2,4-DCP) by photocatalysis. To remove CPs more completely, a sequential photolaccase catalytic system was designed to degrade PCP and 2,4-DCP mixture in water at the optimal pH value. The results showed that photocatalysis prior to laccase-catalysis (PPL) is a better approach than laccase-catalysis prior to photocatalysis (LPP), eliminating CPs more efficiently and generating lower toxic products. The identified intermediate products consisted of adipic acid, hexanediol, glycol, propylene glycol, hydroquinol, and phthalandione. Based on the products identified, the sequential degradation process was proposed, including the interlace reactions involving quinoid oxidation, reductive dechlorination, and no-enzyme polymerization. Upon reaction optimization, a piston flow reactor (PFR) was designed to treat the continuous feeding of simulated wastewater containing PCP and 2,4-DCP. After a 128 h period of treatment, 87.4-99.5% total concentration of CPs were removed (PPL removed 99.7% PCP and 99.2% 2,4-DCP; LPP removed 95.9% PCP and 78.9% 2,4-DCP).
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
Lifeng
L
Yin
Zhenyao
Z
Shen
Junfeng
J
Niu
Jing
J
Chen
Yanpei
Y
Duan
D002384:Catalysis; D002733:Chlorophenols / Q000737:chemistry* / Q000633:toxicity; D052918:Environmental Restoration and Remediation; D004926:Escherichia coli / Q000187:drug effects; D042845:Laccase / Q000737:chemistry*; D008027:Light; D010084:Oxidation-Reduction; D010416:Pentachlorophenol / Q000737:chemistry* / Q000633:toxicity; D055668:Photochemical Processes; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000633:toxicity
D002733:Chlorophenols; D014874:Water Pollutants, Chemical; D010416:Pentachlorophenol; D042845:Laccase; C004762:2,4-dichlorophenol