Physical features of ultrasound assisted enzymatic degradation of recalcitrant organic pollutants

Abstract

This work has attempted to provide answer to the interaction of sonolysis and enzymatic treatment on degradation of recalcitrant dyes in a combined treatment. The model system comprises of two dyes, acid red and malachite green as model pollutants, along with horseradish peroxidase as a model enzyme and ultrasound of 20 kHz frequency. A dual approach of coupling experimental results with simulations of cavitation bubble dynamics has been adopted. Utilization of oxidation potential of horseradish peroxidase has been found to be a function of convection level in the medium. Cavitation phenomenon is found to have an adverse effect on enzyme action due to generation of high amplitude shock waves, which denature the enzyme. Degradation of dye at high static pressure increases due to absence of cavitation and high energy interaction (or collisions) between enzyme and dye molecules, which are beneficial towards enzymatic oxidation of the latter. High intensity convection generated by ultrasound also obviates need for an external shielding agent such as PEG that prevents attachment of the phenoxy radicals to enzyme that blocks the active sites of the enzyme.