Effects of zinc salt addition on perfluorooctanoic acid (PFOA) removal by electrocoagulation with aluminum electrodes.

In this study, the electrocoagulation (EC) of perfluorooctanoic acid (PFOA) by an aluminum electrode with the addition of zinc salt was investigated. Adding ZnCl2 successfully prevented a rise in pH during EC and increased the efficiency from 73.7% to over 99%. In addition, the longer the carbon chain of a PFA was, the better the removal of that PFA by electrocoagulation. The main functions of ZnCl2 were to prevent the rise in pH and improve flotation because the flocs with added ZnCl2 were easy to gather together and had a faster floating speed. The XPS results demonstrated the occurrence of bonding between aluminum and fluoride. This finding indicates that complexation between aluminum and fluoride may be the main mechanism for removal when aluminum electrodes are used to remove perfluoroalkyl (PFA) compounds.