Hoopes process

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Hoopes process" – news · newspapers · books · scholar · JSTOR (May 2017) (Learn how and when to remove this template message)

The Hoopes process is a

Introduction

It is a method used to obtain aluminium of very high purity. The metal obtained in the Hall–Héroult process is about 99.5% pure, and for most purposes it is taken as pure metal. However, further purification of aluminium can be carried out by the Hoopes process. This is an electrolytic process.

The process

The cell used in this process consists of an iron tank lined with carbon at the bottom. A molten alloy of copper, crude aluminium and silicon is used as the anode. It forms the lowermost layer in the cell. The middle layer consists of molten mixture of

+ BaF₂). The uppermost layer consists of molten aluminium. A set of graphite rods dipped in molten aluminium serve as the cathode. During electrolysis, Al³⁺ ions from the middle layer migrate to the upper layer, where they are reduced to aluminum by gaining 3 electrons. Equal numbers of Al³⁺ ions are produced in the lower layer. These ions migrate to the middle layer. Pure aluminium is tapped off from time to time. The Hoopes process gives about 99.99% pure aluminium.

References

Further reading

• Schwarz, V.; Wendt, H. (1995). "Electrorefining of aluminium scrap from chloride melts". Journal of Applied Electrochemistry. 25.
  S2CID 94160544
  .