Sorption properties of peroxidase-catalysed polyphenolic resin enable aromatics’ capture

Abstract

Soybean peroxidase catalyses the removal of many phenols and anilines through polymerisation and precipitation. The precipitates might sorb other wastewater compounds simultaneously through a hydrophobic interaction. To model this interaction, phenol was chosen as the substrate and 4-(phenylazo)benzoate as the sorbate, and the system was quantitatively evaluated with the Langmuir isotherm. Sorption occurred either during or after enzymatic conversion of phenol (dynamic or static, respectively). The two systems showed Langmuir association constants of 0·088 and 0·13 l/mg and maximum sorption capacities of 51 and 16 mg/g, respectively. Both parameters compare favourably with those for the sorption of benzene, toluene and xylenes on activated carbon. A composite Langmuir parameter, (maximum capacity/dissociation constant), is suggested as the criterion for evaluating potential sorbent–sorbate couples. The model system demonstrates the feasibility of using enzymatically generated phenolic precipitates to remove toxic hydrophobic aromatic non-substrates from wastewater, when they co-occur with a substrate such as phenol. In the future, the use of polyaryl sorbents for aryl sorbates should be more broadly characterised and the criterion used for comparison should be the composite Langmuir parameter.