Textile polyacrylonitrile (PAN) fibers, which contain nitrogen, were carbonized at different temperatures and activated during 10 h in order to assess their performance as ozonation catalysts in the oxalic acid degradation The fiber carbonized at 800 degrees C shows the best performance due to its basic character and, mainly, the high concentration of nitrogen surface groups, particularly N-pyridinic (N6) groups. The carbonization of PAN fibers is a simple and effective method to prepare materials with good catalytic activity in ozonation processes (C) 2015 Elsevier B.V. All rights reserved.