Removal of aqueous phenolic compounds from a model system by oxidative polymerization with turnip (Brassica napus L var purple top white globe) peroxidase

Turnip roots, which are readily available in Mexico, are a good source of peroxidase, and because of their kinetic and biochemical properties have a high potential as an economic alternative to horseradish peroxidase (HRP). The efficiency of using turnip peroxidase (TP) to remove several different phenolic compounds as water-insoluble polymers from synthetic wastewater was investigated. The phenol derivatives studied included phenol, 2-chlorophenol, 3-chlorophenol, o-cresol, m-cresol, 2,4-dichlorophenol and bisphenol-A. The effect of pH, substrate concentration, amount of enzyme activity, reaction time and added polyethylene glycol (PEG) was investigated in order to optimize reaction conditions. A removal efficiency greater than or equal to85% was achieved for 0.5 mmol dm(-3) phenol derivatives at pH values between 4 and 8, after a contact time of 3 h at 25degreesC with 1.28 U dm(-3) of TP and 0.8 mmol dm(-3) H2O2. Addition of PEG (100-200 mg dm(-3)) significantly reduced the reaction time required (to 10 min) to obtain >95% removal efficiency and up to 230% increase in remaining TP activity. A relatively low enzyme activity (0.228 U dm(-3)) was required to remove >95% of three phenolic solutions in the presence of 100-200 mg dm(-3) PEG. TP showed efficient and fast removal of aromatic compounds from synthetic wastewaters in the presence of hydrogen peroxide and PEG. These results demonstrate that TP has good potential for the treatment of phenolic-contaminated solutions. (C) 2002 Society of Chemical Industry.