Solar photocatalytic water detoxification of paper mill effluents

To implement solar photocatalytic water detoxification in industrial processes, problems have to be identified. The effluents from paper mills contain non-biodegradable substances like polyphenolic polymer lignin. Photocatalysis is a suitable method to degrade this class of substances. Especially in good solar regions, like Brazil, solar radiation should be ideally used for that process. The German Aerospace Center and the Federal University of Uberlândia-MG, Brazil are cooperating in a project funded by the German International Bureau of the Federal Ministry of Education and Science and CNPq, Brazil to implement solar photocatalysis in the treatment of paper mill effluents. Therefore, the following tasks are worked on: model compounds for the contaminants have been identified and compared to the real effluents. Different photocatalysts and oxidizing agents were tested to shape the degradation process for use in an industrial application. Tests were carried out in lamp reactors as well as in solar reactors to determine the influence of the reactor on the degradation. The kinetic of the degradation was also determined. The test results have shown that the non-biodegradable substances can be very effectively degraded by photocatalytic treatment. Especially in solar reactors like the CPC type reactor, degradation takes place very fast. Total mineralization of the contaminants can be reached. The paper describes the project as well as the test results and will provide an outlook to the implementation of solar photocatalytic detoxification technology in Brazil.