Optimization of the removal of phenol by soybean seed coats using response surface methodology

Peroxidase from soybean seed coats catalyzes the oxidation and polymerization of aromatic compounds in the presence of H2O2. The present study investigated the optimization of the phenol removal from wastewaters by direct using of soybean seed coats that can be extended to large scale, as a cost-effective option in comparison to pure enzyme. A central composite design was used to evaluate the effect of the following factors on the phenol removal: H2O2 concentration (1-40 mmol/L), polyethylene glycol (PEG) concentration (0-1 g/L) and the amount of soybean seed coats (10-60 g/L). The results showed that PEG concentration had no significant effect on phenol conversion. Additionally, by increasing the amount of soybean seed coats, the extent of phenol conversion was increased and a higher concentration of H2O2 was required to reach the maximum phenol conversion. Under optimum conditions for 1 mmol/L initial phenol, 50 g/L soybean seed coats, 14 mmol/L H2O2 and 0.8 g/L PEG, the phenol conversion after 30 min was 78%. After 2 h, the catalyzed process was capable of achieving 90-92% removal of the total phenol from synthetic wastewater. A cubic model was also developed that was verified by predicting some independent experimental results.