Use of concentrated solar energy to synthesize alumina from an aluminium hazardous waste

Twenty-Eighth International Conference on Solid Waste Technology and Management. Filadelfia, PA, USAThe aim of this paper is to evaluate the feasibility of obtaining alumina from boehmite prepared from a hazardous waste, using a free, clean, and unlimited power as the solar energy. The objective was to compare results from using a furnace powered by conventional energy with a system using a renewable energy. The waste, coming from the slag milling operations in aluminum industry, is hazardous because of releasing toxic gases (hydrogen, ammonia, methane and hydrogen sulfide) in the presence of water. The process developed to synthesize alumina consisted of two stages: in the first one, a precursor of alumina, boehmite was obtained by hydrothermal treatment of the waste; in the second one, boehmite was transformed in alumina, in air atmosphere, using a solar energy concentrator (Fresnel lens). The solar installation provides a power density of 260 W cm-2 which allows to reaching temperatures upper 1000 ºC at 10 min of exposition. Tests were performed at different times ranged between 5-90 min. Samples were characterized by XRD, FTIR and DTA/TG. Metastable aluminas star to appear at 5 min and the stable phase corundum at 10 min.N