The anodizing plant produce several types of acid and basic wastes, high and low concentration concentration wastes. The neutralization of these waste produce a precipitates and after a filter cake with 80% of water, which have to be sent to disposal. In this project we study the change of composition of this wastes in order to secure his recyclability.
We have resolved with a positive economic balance the recyclability of Al to the Bayer Process of these waste for the Al recovery.
We have obtain useful material for the paper industry and for clarifying of dirty waters. We have also obtain a material with high content Al2O3 next to 98%.
Other application of the anodizing waste is the production of zeolites with methods of low pressure (atmospheric) and low temperatures next to 100 °C.
We have decrease the operative cost of anodized products by minimizing the comsuption of additives recycling the H2SO4 partially to the anodizing bath. We have also improved the quality of products developing adequate control loops and securing the permanent composition of the baths for long time.
A monographic study have been made with the comparison between two running anodizing plants in relation to their safety systems face to evaluate and to control the risk and consequences of accidental pouring of their liquid effluents.
In aluminium anodizing processes, the classical surface treatment of this metal, large quantities of waste (anodic mud) are produced. The average amount of mud which is produced for every Kg of anodized aluminium is 250g/Kg Al. Given this figure, and on the basis of the estimated quantity of anodized aluminium produced in EEC countries in 1990, the actual amount of anodic mud generated is around 100,000 tons per year.
This anodic mud is a general problem for many European anodizing SMES because it is relatively difficult to manage and no significant applications have been found for it till now, due to its complex nature. In Europe, the anodic mud is usually destined for disposal in authorized waste disposal areas. But depending on how severe in application the environmental laws are in each country, an important part of the mud is uncontrolled, which causes a real ecological impact.
In order to solve the problem, the following ways will be explored:
1) To modify the mud generation process in order to obtain a mud suitable for use in the Bayer process for alumina production.
2) To exploit the anodic mud as sizing agent in paper making industry.
3) To investigate alternative applications of the anodic mud in wastewater treatment and to obtain marketable products.
Funding SchemeCSC - Cost-sharing contracts
1699 CODEX Lisboa
09016 Iglesias Cagliari