Sonocatalytic Degradation of Naphthalene and Phenol in the Presence of Inert Glass Beads and Single-Walled Carbon Nanotubes

Abstract

In this study, a series of sonocatalytic degradation experiments were carried out to determine the degradation of naphthalene and phenol in aqueous solution at an ultrasound frequency of 28 kHz. The effectiveness of inert glass beads (GBs) as catalysts was compared with that of single-walled carbon nanotubes (SWNTs) as catalysts using a contact time of 60 min. The most effective catalyst combination for the production of 102.2 mu M of H2O2 was the use of SWNTs 5 mg L-1 with GBs 10 g L-1 as the catalyst. For the given contact time and frequency, sonochemical reactivity was determined from the rate constants of H2O2 production. Statistical analysis of the data revealed that naphthalene degradation follows pseudo-first order kinetics, whereas phenol degradation follows zero order kinetics. Naphthalene and phenol sonodegradation occurred in the following order (with the observed rate constant in parentheses): SWNTs 25 mg L-1 + GBs 10 g L-1 > SWNTs 25 mg L-1 = no addition >= GBs 10 g L-1 >= SWNTs 5 mg L-1 + GBs 10 g L-1 >= SWNTs 5 mg L-1 > GBs 50 g L-1 for naphthalene, and SWNTs 5 mg L-1 + GBs 10 g L-1 congruent to GBs 10 g L-1 >= SWNTs 25 mg L-1 + GBs 10 g L-1 >> SWNTs 25 mg L-1 congruent to no addition congruent to SWNTs 5 mg L-1 congruent to GBs 50 g L-1 for phenol.