The aim of this study is to investigate the effect of various factors on the photodegradation of organic pollutants in natural environment with co-existence of iron oxides and oxalic acid. 2-Mercaptobenzothiazole (NOT) was selected as a model pollutant, while gamma-Fe2O3 was selected as iron oxide. The crystal structure and morphology of the prepared gamma-Fe2O3 was determined by X-ray diffractograms (XRD) and scanning electron microscopy (SEM), respectively. The specific surface area was 14.36 m(2)/g by Brunauer-Emmett-Teller (BET) method. The adsorption behavior of,gamma-Fe2O3 was evaluated by Langmuir model. The effect of the dosage of iron oxide, initial concentration of oxalic acid (C-ox(0)), initial pH value, the light intensity and additional transition metal cations on MBT photodegradation was investigated in the gamma-Fe2O3/oxalate suspension under UVA light irradiation. The optimal gamma-Fe2O3 dosage was 0.4 g/L and the optimal C-ox(0) was 0.8 mM with the UVA light intensity of 1800 mW/cm(2). And the optimal dosage of gamma-Fe2O3 and C-ox(0) for MBT degradation also depended strongly on the light intensity. The optimal gamma-Fe2O3 dosage was 0.1, 0.25 and 0.4 g/L, and the optimal C-ox(0) was 1.0, 0.8, and 0.8 mM with the light intensity of 600,1200 and 1800 mW/cm(2), respectively. The optimal initial pH value was at 3.0. The additional transition metal cations including Cu2+, Ni2+ or Mn2+ could significantly accelerate MBT degradation. This investigation will give a new insight to understanding the MBT photodegradation in natural environment. (c) 2007 Elsevier B.V. All rights reserved.