David Pines

Solid phase catalytic ozonation process for the destruction of a model pollutant

Pure metal oxides, mixed metal oxides, and platinum metals were evaluated as ozonation catalysts. Batch reactor experiments were performed using deionized water at pH 7 and semi-continuous ozonation experiments were performed using a natural water. p-Chlorobenzoic acid (pCBA), a non-adsorbing model micropollutant that does not react directly with molecular ozone, was included in both solution matrixes. Titanium dioxide, cobalt oxide, nickel oxide, copper oxide, and a mixed metal oxide comprised of copper, zinc, and aluminum did not accelerate the removal pCBA in deionized water. However, cobalt oxide and the mixed metal oxide catalyst were effective at accelerating the removal of pCBA in a natural water matrix. The mixed metal oxide catalyst may have the most potential as an ozonation catalyst because it also was very stable (i.e., low solubility). A ruthenium / alumina catalyst also increased the removal of pCBA, but this metal may follow a different reaction mechanism than the metal oxide catalysts.

Investigation of an Ozone Membrane Contactor System

Ozone mass transfer rates were determined for nine expanded porous Teflon membranes that had different pore size, thickness, and pore volume, a nonporous Teflon membrane, and a PVDF membrane. The mass transfer coefficient was 7.6 ± 0.5 × 10−5 m/s at Re of 2000 for all membranes tested even though pore sizes ranged from 0.07 to 6 μm and thickness from 0.076 to 0.25 mm. Mass transfer increased with liquid side Reynolds number. Therefore, it is likely that ozone mass transfer is liquid phase controlling and not membrane limited. For a hypothetical case of 4000 m3/d and 2 mg/L ozone transferred, plate and frame membrane and hollow fiber contactors are approximately one and two orders of magnitude smaller, respectively, than fine-bubble diffusers.

Computational Fluid Dynamic Analysis of Air Flow in Node 1 of the International Space Station

Proper design of the air ventilation system is critical to maintaining a healthy environment for the ISS crew. In this study, a computational fluid dynamic model was used to model the air circulation in Node 1 to identify the locations where there are low air velocities under nominal operating conditions and several reduced ventilation flow conditions. The reduced ventilation flow conditions analyzed were loss of cabin air fan, loss of inter-module ventilation from Node 1 to the US Lab, and loss of inter-module ventilation from the airlock to Node 1. For nominal operation of the ventilation system, about 5% of the node had air velocity of between 1 and 5 ft/min and 14% of the node had air velocity of between 5 and 10 ft/min. Loss of the cabin air fan and loss of Lab inter-module ventilation did not have a significant impact on the percentage of the node that would have low air circulation. However, the locations where the air was relatively stagnant were shifted depending on the case considered. The failure mode that had the most significant impact was loss of inter-module ventilation from the airlock. This case increased the percentage of the node with air velocity between 1 ft/min and 5 ft/min to 9.5%, and the percentage of the node with air velocity between 5 ft/min and 10 ft/min to 26%.