Sonolysis of alkylphenols in aqueous solution with Fe(II) and Fe(III)

The sonolytic degradation of alkylphenols (APs). such as butylphenol. pentylphenol, octylphenol, and nonylphenol (NP), in water was investigated at a sound frequency of 200 kHz with an acoustic intensity of 6 W cm(-2) under argon, oxygen, and air atmospheres. The sonolytic degradation rate of the APs under the conditions of the present study depended upon their alkyl chain length. The decrease in the degradation rate by the radical scavenging effect was in the range of about 48-82% for APs in the presence of 3 mM 2-methyl-2-propanol. The free radicals play a significant role in the sonolytic degradation process of the APs. In the presence of Fe(II) and Fe(III), the pseudo-first-order rate constants for the sonolytic degradation of 30 muM NP as a function of the concentration of Fe(II) and Fe(III) were estimated under argon and oxygen. The maximum rate constants were observed at 50 muM Fe(H) (0. 139 +/- 0.008 min(-1)) and 100 muM Fe(III) (0.103 +/- 0.001 min(-1)) under oxygen. The total organic carbon concentration (TOC) was investigated under same conditions. TOC decreased in the range of about 50-70 during the sonication in the presence of Fe(II) and Fe(III) under argon and oxygen. The sonochemical effects by the addition of Fe(II) and Fe(III) as catalyst during the sonication under the proper atmosphere result in a remarkable enhancement of degradation and mineralization. (C) 2002 Elsevier Science Ltd. All rights reserved.