Hydrogen production from electrochemical treatment of textile dyeing wastewaters
D. Cuesta-Mota, Anna Serra, Xavier Guimerà Villalba, Lluc Canals Casals, Víctor López Grimau
Abstract
Textile dyeing processes produce non-biodegradable, intensively coloured effluents, which contain unreacted dye molecules and are not efficiently treated by conventional biological treatments. Electrochemical processes are an alternative with an added value that is normally ignored because of a lack of evidence and supporting studies: the simultaneous production of hydrogen and its potential. This study assesses the capability of electrochemical processes to eliminate the colour from textile dyeing wastewaters while hydrogen is produced as a by-product. Four textile dyeing effluents containing the four most commonly used reactive azo dyes were treated in a Hofmann Voltameter. The results indicate that lower current densities are more energy-efficient working conditions for both studied variables (discolouration and hydrogen production), although they lead to a slower process. Discolouration of the effluents is >90 % with a consumption of 5 kWh/m3 in the most efficient conditions. The presence of the dye has no effect on hydrogen generation flows or performance in function of the applied current. Hydrogen production efficiencies of around 80–95 % are achieved, compared to the theoretical maximum. The effluent's electrical conductivity is the only variable that affects the results, with greater conductivity implying better energy performance. The hydrogen produced had no impurities due to the effluent composition and stored up to 20 % of the energy consumed during the treatment under the most efficient working conditions (20–25 mA/cm2). Therefore, it is available for energy recovery and represents an incentive to use electrochemical treatment of wastewaters with anode-cathode separation and hydrogen capture on the cathode.