Optimization of operational conditions for biodegradation of chlorophenols by laccase-polyacrilonitrile beads system

The oxidative biodegradation of 2- and 4-chlorophenol (CPs) catalyzed by immobilized laccase from Trametes versicolor was conducted in a bed reactor. The effects of reaction conditions (reaction time, dosage of immobilized enzyme, flow rate, pH value and temperature, initial concentration) on CPs removal efficiency (RE  ) were investigated. By using in the immobilization solution an enzyme dosage of 2.5 mgfree enzgcarrier−1, the maximum ratio of laccase to PAN-beads is resulted 0.25 mgimm enzgcarrier−1.RE values greater than 70% were obtained when 40 mL of 1 mM substrate solution were circulated for 90 min at 75 mL min−1 in the bed reactor filled with 12 g of laccase-PAN beads. The optimal pH for CPs biodegradation was 5 and it was not related to substituent position on aromatic ring. Experiments with immobilized laccase demonstrated good removal at high initial substrate concentrations and high thermal stability. The affinity of 2-CP was higher than that of 4-CP.Finally, the 2-CP was also biodegraded as tertiary mixtures with 2,3,4,5-tetrachlorophenol (TCP) and pentachlorophenol (PCP). The presence of TCP and PCP decreased the removal efficiency of 2-CP. The order of the relative degrading capacity becomes TCP > PCP > 2-CP.

Figure optionsDownload as PowerPoint slideHighlights
► The oxidative biodegradation of 2- and 4-chlorophenol (CPs) catalyzed by immobilized laccase was conducted in a bed reactor.
► The effects of reaction conditions (reaction time, enzyme dosage, flow rate, pH, temperature, initial concentration) on CPs removal efficiency were determined.
► The catalytic system was proved stable and highly efficient at pH 5 and at high temperatures.
► The laccase has a greater affinity for 2-CP than 4-CP.
► The 2-CP was biodegraded as tertiary mixtures with 2,3,4,5-tetrachlorophenol and pentachlorophenol.