The washing effects of using different acid solutions (0.1 N; CH3COOH, C2H2O4, and C6H8O7) on the activity of spent three way catalysts (TWCs) in oxidizing volatile organic compounds (VOCs) were investigated to recycle the spent catalyst. The spent TWCs and acid solution treated TWCs are characterized by using X-ray diffraction (XRD), N-2 adsorption, transmission electron microscope (TEM) and an inductively coupled plasma (ICP) analysis. The spent TWCs are found to show a great potential for removal of organic compounds. Among the regeneration methods applied, the oxalic acid as a washing chemical agent proved to be quite effective in enhancing the catalytic activity of the spent TWCs compared to other acids (citric acid and acetic acid). Furthermore, the catalytic activities are clearly explained in terms of the remaining Pt/Al ratio of the TWCs, the ionization potential and dipolar moments of the organic compounds. (C) 2010 Published by Elsevier B.V.