Can hazardous waste become a raw material? The case study of an aluminium residue: a review

The huge number of research studies carried out during recent decades focused on finding an effective solution for the waste treatment, have allowed some of these residues to become new raw materials for many industries. Achieving this ensures a reduction in energy and natural resources consumption, diminishing of the negative environmental impacts and creating secondary and tertiary industries. A good example is provided by the metallurgical industry, in general, and the aluminium industry in this particular case. The aluminium recycling industry is a beneficial activity for the environment, since it recovers resources from primary industry, manufacturing and post-consumer waste. Slag and scrap which were previously considered as waste, are nowadays the raw material for some highly profitable secondary and tertiary industries. The most recent European Directive on waste establishes that if waste is used as a common product and fulfils the existing legislation for this product, then this waste can be defined as 'end-of-waste'. The review presented here, attempts to show several proposals for making added-value materials using an aluminium residue which is still considered as a hazardous waste, and accordingly, disposed of in secure storage. The present proposal includes the use of this waste to manufacture glass, glass-ceramic, boehmite and calcium aluminate. Thus the waste might effectively be recovered as a secondary source material for various industries.