Oxidative photocatalytic degradation has proven to be an effective method for the removal of toxic sodium oxalate, a major impurity in the Bayer liquor obtained during alumina processing. The proposed route also simultaneously converts the oxalate to causticizable solution. The reaction was carried out in an annular multiphase photoreactor with commercial TiO2 powder (99% anatase) as the catalyst. There was a strong influence of both catalyst content and initial pH of the reaction mixture. Conversion generally decreased with increased pH. Complete mineralization of the oxalate to caustic solution was achieved within a very short period of similar to 2 h at 303 K, 0.5 gl(-1) catalyst loading and an initial solution pH of similar to 2. We believe that the reaction proceeds via a homogeneous-heterogeneous mechanism involving interaction between adsorbed oxalate ions (generated from liquid phase dissociation of sodium oxalate) on the titania surface (holes) and hydroxyl species to give adsorbed hydrogen carbonate ions which later desorb to form the caustic NaHCO3 solution.