Adsorption of Hydrogen Fluoride on Certain Smelter-Grade Aluminas

The ability of alumina to control atmospheric emission of HF during aluminum smelting is controlled by the mechanisms of HF adsorption on the alumina. A fundamental study of HF adsorption demonstrated the relationship between adsorption capacity and humidity, and a mechanism for the chemical linkages which govern adsorption is proposed. Adsorption efficiency in both laboratory and production tests shows a sharp decline once a certain quantity of HF has been adsorbed, and this saturation value is directly proportional to the specific surface area of the alumina. However, there is a discrepancy not yet explained: the maximum adsorption capacity in laboratory tests is roughly twice that determined under production conditions.