Ultrasound-enhanced electrochemical mineralization of perfluorooctanoic acid in aqueous solutions: Assessed by response surface methodology

Abstract

Aims: The sonoelectrochemical mineralization of the synthetic aqueous solution of the perfluorooctanoic acid (PFOA) on Ti/PbO 2 anode was investigated using the response surface methodology based on a central composite design (CCD). Materials and Methods: The CCD was performed using three different variables such as current density (CD) (mA/cm 2 ), pH, and supporting electrolyte (EL) concentration (mM). The total organic carbon (TOC) removal was determined as an indicator of PFOA mineralization. A Shimadzu TOC analyzer was used to measure the TOC of the samples. The Ti/PbO 2 electrode was prepared using the electrochemical deposition method. In order to enhance the electrochemical mineralization, ultrasonic (US) radiation was used. The US frequency was 20 kHz. Results: The optimum conditions for PFOA mineralization in synthetic solution were EL concentration of 94 mM, pH of 2, and CD of 83.64 mA/cm 2 , which resulted in complete TOC removal. The results indicated that the most effective factor for PFOA mineralization was CD. Besides, the TOC removal efficiency significantly increased with increasing CD. Conclusions: Under optimum conditions, the mineralization of PFOA was almost completed after 90 min of sonoelectrolysis. Therefore, sonoelectrolysis was found to be a more effective technique for mineralization of an environmentally persistent compound.