Design Aspects of a Continuous Flow Photocatalytic Reactor and its Application to Degrade Methylene Blue and Textile Wastewater

摘要

A continuous flow photocatalytic reactor was developed by combining the reaction kinetics and mass balance concept. The concept of cascade aerator was also considered in designing it as a stepped reactor. The reactor was used to investigate the photocatalytic degradation of methylene blue in aqueous solution by Ag~+ doped TiO2 (2 g/L) under UV irradiation by 15 W UV lamps (254 nm). Methylene blue solution (20 ppm) was found to be decolorized by >99, 97, 85 and 57% under flow rates of 1, 1.5, 2 and 3 L/h, respectively after 120 minutes. The corresponding mineralization was >80, 78, 75 and 54%, respectively. At higher flow rates (Re number 208.2 and 415.5) >99% decolourization was achieved by recycling the solution 5 and 7 times with fresh doses of photocatalyst. At steady state, maintained by repeating the addition of photocatalyst at fixed time intervals, the dye solution could be decolourized continuously by >99, 97 and 76% at flow rates of 1, 2 and 3 L/h, respectively while the mineralization was >82, 79 and 62%, respectively. The reactor was also effectively used to mineralize textile wastewater collected from a textile mill in Kolkata. The mineralization was greater than 75, 73 and 64% at flow rates of 1, 2 and 3 L/h, respectively after 120 minutes. The efficiency of the reactor depended upon the residence time of the contaminant in the reactor. At steady state, the design data simulated well with the corresponding experimental data.