Optimization of a magnetically agitated photocatalytic reactor for water recovery

NASA will require a safe and efficient method for water recovery on long-term space missions. Photocatalysis represents a promising solution for part of a system designed for recovery of water from humidity condensate, urine, and shower waste. It eliminates the need for chemical oxidants that are dangerous and difficult to transport, and the considerable energy consumption of distillation. In terms of decreasing the equivalent system mass (ESM) with respect to these alternative technologies, considerations for the volume, mass, cooling and crew time are also important. This photocatalytic reactor generates the oxidant in the form of hydroxyl radicals and valence band holes by exposing silica-titania composite particles with a barium ferrite core to ultraviolet light. The magnetic core of the catalyst allows for separation, confinement, and agitation. This agitation, accomplished with a sinusoidal signal fed solenoid, allows greater mass transfer and improves mineralization of organics. In addition, fixed magnets strategically placed above the reactor confines the catalyst to where it receives maximum UV exposure. The composite catalyst, irradiated by an 8-watt 254 nm lamp, was able to decrease the 10 mg/L initial phenol concentration by an average of 92.2% after one hour. Although the frequency of the signal fed to the solenoid did not appear to have an impact on the extent of photodegradation (10-80 Hz), there was a strong correlation with the ball milling process. Building upon pioneering work of Mazyck and Drwiega (04-ICES 2404), this promising option for water recovery has been optimized with improvements in magnetic field, reactor design, and catalyst synthesis.