Fabrication of novel SnO2-Sb/carbon aerogel electrode for ultrasonic electrochemical oxidation of perfluorooctanoate with high catalytic efficiency

A novel SnO 2 -Sb/CA electrode, possessing high surface area, strong adsorption capacity, good electrical conductivity and electrocatalytic activity, was firstly proposed for ultrasonic electrochemical oxidation (US-EC) of persistent high concentration perfluorooctanoate (PFOA) in this study. The optimal calcination temperature for sinking micro-sized SnO 2 -Sb particles existed on the surface of CA into the structure of CA as nanoparticles was 600   °C. Its application on degrading PFOA (60   mL of 100   mg   L −1 ) exhibited efficient electrocatalytic performance. After 5   h electrolysis, over 91% of PFOA was degraded with a first-order kinetic constant of 0.52   h −1 and over 86% TOC removal was achieved, while 47% PFOA removal and 33% TOC removal were obtained in traditional electrochemical (EC) process. The main role of determining the decomposition efficiency, i.e., the mass transport, hydroxyl radical (·OH) generation and electrode surface reaction, were greatly enhanced in US-EC system. Additionally, the generated intermediates existing on electrode surface and in solution were separately detected after different electrolysis time and the proper mechanism for efficient removing PFOA in US-EC process was investigated in detail. At early reaction stage (<0.5   h), the intermediate products on SnO 2 -Sb/CA surface were C 5 F 11 COO − , C 4 F 9 COO − , C 3 F 7 COO − , C 2 F 5 COO − , CF 3 COO − , while in solution were C 5 F 11 COO − , C 4 F 9 COO − , C 3 F 7 COO − . At late reaction stage (>5   h), the intermediates either on electrode surface or in solution became the same including C 5 F 11 COO − , C 4 F 9 COO − , C 3 F 7 COO − .