From Alumina to Aluminum: The Hall-Heroult Process
By Cody Berry
Last time we covered the Bayer Process which takes the alumina out of raw bauxite ore. This week we will cover the next step in the aluminum making process. In 1880, a 20-year-old first year student at Oberlin College in Ohio named Charles Martin Hall started his research into the production of aluminum. The idea was to use electric current to extract pure aluminum from the alumina that was probably produced through the Bayer Process. In 1886, Hall and French chemist Paul Heroult simultaneously invented what became known as the Hall-Heroult process.1
The process that both Hall and Heroult came up with involved dissolving the alumina using electrolysis in another mineral called cryolite. The alumina and cryolite are mixed together in a carbon-lined steel pot. Carbon anodes are inserted into the top of the bath and an electric current is passed through it all. This causes the oxygen atoms to separate from the alumina and combine with the carbon anode, leaving behind molten aluminum in the bottom of the pot. The molten metal is removed and placed in a holding furnace from which it can be cast into ingots.2
Charles Martin Hall was the founder of what became known as the Aluminum Company of American, or Alcoa. After perfecting his aluminum smelting method, Hall went to Pittsburgh, Pennsylvania, where the Pittsburgh Reduction Company was founded. They grew to be the largest producer of aluminum in the United States.3 The Pittsburgh Reduction Company built their first ore drying plant in Saline County, Arkansas in 1903, and in 1907, they became Alcoa.4
Citations:
1 The Aluminum Association, “Primary Production 101,” https://www.aluminum.org/primary-production-101, Date Accessed April 8, 2025.
2 The Aluminum Association, “Primary Production 101,” https://www.aluminum.org/primary-production-101, Date Accessed April 8, 2025.
3 Oberlin College, “Charles Martin Hall (1863-1914),” https://www2.oberlin.edu/external/EOG/OYTT-images/CMHall.html, Date Accessed April 9, 2025.
4 Gordon Scott Bachus, A Printed and Pictorial History of Bauxite, Heritage Publishing Company: North Little Rock, 1968, 2000, and 2007, p. 7-8.