Ozonation of oxalic acid in aqueous solution was conducted using multi-walled carbon nanotube (MWCNT) as the catalyst. The effects of operating conditions on the catalytic performance of MWCNT for oxalic acid removal were investigated. The catalyst dosage and the reaction temperature exert positive effects on the oxalic acid removal by MWCNT catalytic ozonation. The maximum degradation efficiency of oxalic acid is obtained with its initial concentration of 1.0 mM. The degradation efficiency of oxalic acid increases with the initial pH value in the range of 1.0-3.0, whereas an opposite trend is observed when the initial pH value further increases from 3.0 to 6.1. The effect of initial pH value indicates that the oxalic acid adsorption on catalyst surface is essential for its effective removal by MWCNT catalytic ozonation. The inhibition of tert-butanol on the activity of MWCNT at initial pH 6.1 is more significant compared with the case of initial pH 3.0, suggesting that the contribution of bulk reactions to oxalic acid removal would be strengthened at a high initial pH value. (C) 2011 Elsevier B.V. All rights reserved.