Effects of Ultrasound on the Degradation of Pentachlorophenol by Boron-Doped Diamond Electrodes

 

Gustavo S. Garbellini,^1,* Giancarlo R. Salazar-Banda,² Luis A. Avaca¹

¹ São Paulo University, Institute of Chemistry of São Carlos, CP 780, 13560-970 São Carlos - SP, Brazil

² Tiradentes University / Institute of Technology and Research, 49032-490 Aracaju - SE, Brazil

 

DOI: 10.4152/pea.201006405

 

Abstract

The beneficial effects of the ultrasound (US) like the cleaning of electrode surface and enhancement of mass transport were evaluated in association with potentiostatic electrolyses for the degradation of pentachlorophenol (PCP) at 3.0 V vs. Ag/AgCl, using a boron-doped diamond (BDD) electrode during 270 minutes. Different decay levels of the PCP spectrum bands in 220, 251 and 321 nm, respectively, were observed after application of ultrasound without electrochemical process (18.1, 17.7 and 19.8 %), silent electrolyses (29.3, 71.6 and 70.8 %), pulsed sonoelectrolysis (31.0, 75.1 and 76.3%) and sonoelectrolyses (39.2, 80.0 and 82.6 %). For silent and sonoelectrolyses processes, cleaning/reactivation of the BDD surface by acetonitrile and/or electrochemical treatment was necessary. The pulsed sonolectrolysis were carried out purposely without cleaning/reactivation of the surface. The results showed greater PCP degradation for insonated studies than those obtained for the silent electrolyses, due to the increase of mass transport, minimization of the electrode fouling and the combined generation of hydroxyl radicals by both ultrasound and the polarized BDD surface. These tools (US and BDD), especially the pulsed sonoelectrolysis, can improve the degradation of pesticides and their metabolites in the environment and enable the use of sonoelectrochemistry for wastewater remediation.

Keywords: ultrasound, diamond electrode, degradation, pesticides, sonoelectrolysis.

 

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Acknowledgements

The authors thank CNPq (Proc.142930/2005-9 and 304018/2009-0) and Fapesp (Proc. 06/50692–2) of Brazil for the scholarships and financial support to this work.

 

* Corresponding author. E-mail address: gustgarb@yahoo.com.br

Received 15 July 2010; accepted 9 November 2010