Stephen F. Yates

Crossflow Microfiltration-Fouling Mechanisms Studies

Abstract Our objective has been to improve the commercial potential of a crossflow microfiltration process with lime softening of surface waters rich in humic and fulvic acids. These components complicate the filtration of CaCO3 solids both in the filter cake layer and through direct interactions with the nylon membrane support surface. We characterized the humic/fulvic acid fouling and developed several strategies for alleviating the problem. Physical cleaning methods like crossflow and backflush alone are ineffective. We devised chemical pretreatment and chemical cleaning procedures which improve performance.

Scale-Up and Testing of a Novel Ion Exchanger for Strontium

Abstract The preparation of sodium nonatitanate was successfully scaled up to the 10 kg scale. The resulting material is highly selective for strontium, especially in alkaline solutions, giving a distribution coefficient (Kd) of 21,000 mL/g for strontium in a solution of 55 ppm Sr, 5 M NaNO2, and 0.1 M NaOH. Column studies with pelletized sodium titanate show that this form has good mass transfer kinetics, and a high dynamic capacity for strontium (2.0 meq/g from a solution of 47 ppm Sr, 5 M NaNO3, and 0.1 M NaOH). One of the highlights of this work is that our exchanger maintains its high selectivity for strontium in the presence of a variety of complexants.

Air Purification Technologies Useful for Aircraft Cabin Applications

Aircraft crew and passengers are focusing increased attention on aircraft cabin air quality. The cabin is ventilated using outside air, which is generally very pure. However, there is increasing interest for ensuring that high quality air is supplied when the outside air is contaminated, during equipment malfunction, or when air contaminants or odors are generated within the aircraft cabin. Aircraft air quality systems must operate under conditions of high flow rate, severe weight and volume limitations, and low power. Moreover, contaminants to be removed are present at very low concentrations. Adsorptive technologies can be effective, but are frequently heavy, can become secondary sources because of their adsorbed inventory, and often require costly maintenance schedules. Catalytic oxidation has advantages of broader effectiveness, greater reliability, and less maintenance. This paper will discuss air purification technologies developed for use on recirculated cabin air. Laboratory studies have been used to develop a durable and highly effective photocatalyst which, in the presence of ultraviolet lamps, converts air contaminants to carbon dioxide and water. Scale up of this technology to a 1000 cfm scale has allowed demonstration of the effectiveness of this technique under realistic conditions. The prototype reduced ethanol, as a typical air contaminant, at >50% conversion at feed concentrations typical of commercial flights, with no byproduct generation above the odor threshold.