Process studies for photocatalytic rejuvenation of spent industrial Bayer liquor. A new low-energy photocatalytic process for the continuous treatment of spent liquor from the Bayer process for alumina production has been demonstrated. This new technology can process up to 1500 litres of industrial caustic effluent per day with a reduction in carbon dioxide release. The photo-treated refinery wastewater also provides water savings of 30 per cent.