Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Recycling waste from aluminium anodizing plants

Anodizing plants produce several types of acid and basic wastes, of either high or low concentration. The neutralization of these wastes produces a precipitate as a filter cake which is 80% water, which has to be sent for disposal. In this project, the change of composition of the wastes has been studied in order to secure their recyclability.

We have resolved, with a positive economic balance, the recyclability of aluminium to the Bayer Process. We have obtained useful material for the paper industry, and for clarifying of dirty waters. We have also obtained a material with a high alumina content (up to 98%). Other applications of the anodizing waste include the production of zeolites, with methods at low pressure (atmospheric) and low temperatures (up to 100 C).

The operating costs for the production of anodized products have been decreased by minimizing the consumption of additives by recycling the sulphuric acid partially to the anodizing bath. We have also improved the quality of products by developing adequate control loops and securing the permanent composition of the baths for a long time.