Separation of Aluminum from More Noble Elements in an Electrolysis Cell with Side-by-Side Geometry

Abstract

Currently, recycled metal is diluted with primary metal to keep the concentration of alloying elements within specification. This will be more difficult in the future, when a larger proportion of the metal is made from scrap. Particularly, there is a need for a process that can remove elements more noble than aluminum from the scrap metal. While electrolytic refining in a three-layer cell (the Hoopes process) is a possibility; the present paper presents a simpler and more flexible electrolysis cell where the anode metal (alloy) and the cathode metal (purified metal) are placed side-by-side. The principle was demonstrated in a laboratory cell. The current efficiency was above 80 pct and the specific energy consumption was about 7 kWh/kg Al. The refining effect was very good, e.g., the copper content in the 7xxx alloy used was reduced from 2.1 wt pct to less than 20 ppm. An industrial version of the cell used in the present work is suggested. The principles and design are generic and can be used for other purposes than recycling aluminum.