Preparation of calcium chloride-anodized aluminum composite for water vapor sorption

In the present study, we propose a novel solid sorbent, which is composed of anodized aluminum and calcium chloride, for water sorption chillers and heat pumps. Aluminum is electrolyzed in acid baths with the result that a thin and porous aluminum oxide film is formed on its surface. The anodic alumina films prepared using an electrolytic bath of sulfuric acid have an average thickness from 8 to 100 μm and mean pore diameter from 6 to 22 nm. The physical properties of anodized aluminum can be controlled by electrolytic conditions such as current density, processing time and temperature. A calcium chloride-anodized aluminum composite sorbent has been prepared by a solution impregnating method. The amount of calcium chloride impregnated on the alumina films reaches up to 16.1 wt%, and the deposition of calcium chloride in the alumina layer has been confirmed by X-ray analysis. The experimental results shows that bare anodized aluminum adsorbs very little water vapor, but the prepared calcium chloride-anodized aluminum composite is active against water vapor even in the low pressure range. Hence, this composite is a promising sorbent for adsorption chillers and heat pumps using water as working fluid.

► CaCl2-anodized aluminum composites as novel sorbents for water vapor. ► Film structure of anodized aluminum can be controlled by preparation conditions. ► Solution impregnation at reduced pressure enables CaCl2 deposition in film pores. ► CaCl2-anodized aluminum composites are active against water vapor in lower pressure range.