Thomas H. Elmer

Recovery of Water from Atmospheric Air in Arid Climates

Abstract The possibility of using hydrated salts supported on carrier beds for extracting water from cool night air and solar energy for recovering the moisture for use as drinking water is dealt with. Equipment for obtaining sorption data in the laboratory is described. The rate of water adsorption by salts from air is a linear function of relative humidity, the amount adsorbed depending on the partial pressure of water exerted by the hydrated salt or by the aqueous salt that results on exposure to the moist air. To assure maximum adsorption it is important to select salts whose saturated aqueous solution exhibits minimal aqueous tension. Hydrated salts supported on carriers, composed of as widely different materials as porous glass, sand, and fibrous board, all release water equally well on heating, despite their large differences in physical makeup.

Flow of Air, Nitrogen, and Hydrogen through Porous Glass Tubes

Abstract A simple apparatus for obtaining diffusion data for porous tubes is described. It was used for determining the permeation rates of air, nitrogen, and hydrogen through porous 96% SiO2 glass tubes. To increase flow, these tubes were subjected to multiple etch/wash treatments using aqueous NH4F solutions at room temperature followed by successive hot washes in dilute mineral acid and distilled water. Further increases in permeation rates were achieved by subjecting the base glass used in the preparation of the porous glass to long heat treatments at its phase-separation liquidus prior to leaching and etching. Diffusion data show that the permeability of porous glass is not degraded on heating at temperatures up to 800°C, and that the separation ratios of the experimental glasses are in good agreement with values expected from Grahams law of diffusion. The role of heat treatment of the base glass, etch/wash treatments of the porous glass, and moisture in the gas stream are discussed.