Application of immobilized horseradish peroxidase onto modified acrylonitrile copolymer membrane in removing of phenol from water

Abstract

A non-modified and modified with NaOH and ethylenediamine ultrafiltration membranes prepared from AN copolymer have been used as carriers for the immobilization of horseradish peroxidase (HRP) enzyme. The amount of bound protein onto the membranes and the activity of the immobilized enzyme have been investigated as well as the pH and thermal optimum, and the thermal stability of the free and immobilized HRP. The experiments have proved that the modified membrane is a better support for the immobilization of HRP enzyme. The latter has shown a greater thermal stability than the free enzyme. A possible application has been studied for reducing phenol concentration in water solutions through oxidation of phenol by hydrogen peroxide, in the presence of free and immobilized HRP enzyme on modified AN copolymer membranes. A higher degree of the phenol oxidation has been observed in the presence of the immobilized enzyme. A total removal of phenol has been achieved in the presence of immobilized HRP at concentration of the hydrogen peroxide 0.5 mmol L −1 and concentration of the phenol in the model solutions within the interval 5–40 mg L −1. A high degree of phenol oxidation (95.4%) has been achieved in phenol solution with 100 mg L −1 concentration in the presence of hydrogen peroxide and immobilized HRP, which demonstrates the promising opportunity of using the enzyme for bioremediation of waste waters, containing phenol. The immobilized HRP has shown good operational stability. Deactivation of the immobilized enzyme to 50% of the initial activity has been observed after the 20th day of the enzyme operation.