Production of added-value materials from a hazardous waste in the aluminium tertiary industry: Synergistic effect between hydrotalcites and glasses

摘要

© 2015 Elsevier Ltd. All rights reserved. The powdered solids trapped in filter sleeves in the aluminium tertiary industry are currently disposed of in secure landfills as a result of environmental considerations. Their classification as a hazardous waste is due to their high aluminium content as metallic aluminium or in compounds such as aluminium nitride. These compounds can react with a very low moisture content to release toxic or hazardous gases such as hydrogen and ammonia. This paper presents a low-cost process for the full recovery of this hazardous waste in three steps leading to the production of two different added-value materials. In the first step, mild acid hydrolysis of the waste is carried out to obtain a concentrated aluminium solution and an inert cake. The following steps consist of hydrotalcite synthesis with the resulting solution, and the production of transparent glasses in the CaO-Al2O3-SiO2 system with the cake. Characterisation of the products obtained indicates that the hydrotalcites can adsorb anionic pollutants (molybdates) in a simple way, while the glasses afford improved optical properties in comparison with those prepared by direct vitrification of the waste.