The red mud challenge (Day 156)
30th October 2014
Its low density and strength, coupled with its outstanding resistance to corrosion, make it one of the most useful metals we have.
Aluminium and its alloys are essential to the aerospace and construction industries where it finds widespread use as a structural material.
Our homes wouldn’t be the same without Aluminium either. Modern doors and window frames are commonly constructed from PVC coated aluminium. Many kitchen utensils are made from aluminium as are the cans that contain beer and soft drinks.
And where would we be without that handy roll of ‘tin’ foil, which is of course made from – you’ve guessed it; aluminium.
Aluminium is part of our everyday lives and it will come as no surprise that the International Aluminium Institute has reported that over 55 million tonnes of the stuff were produced world-wide in the twelve months leading up to September 2014.
But there’s a snag – isn’t there always.
A key step in the manufacture of aluminium is the production of aluminium oxide, commonly known as ‘alumina’. We get the alumina by refining bauxite, the most common aluminium ore using the Bayer process.
This method, which involves digesting the bauxite in sodium hydroxide at 175 degrees centigrade - in a process essentially unchanged since 1887 - produces large quantities of waste frequently referred to as ‘red mud’; in fact we generate more than two tonnes of red mud for every tonne of alumina produced.
So it’s little wonder that there may be as much three billion tonnes of red mud waste accumulated in holding ponds and lagoons all over the world.
Red mud was catapulted into the public consciousness in October 2010 when almost 1.9 million litres of it burst through a levee in Hungary inundating local communities and killing ten people.
The contamination affected a large area and reached as far as the Danube, although swift intervention by local agencies, supported by international experts prevented Strauss’s famous blue river being turned into a red one.
The red mud challenge has outfoxed scientists and engineers for more than 125 years, but that might be about to change thanks to some smart work by chemical engineers and chemists in Canada.
Quebec based company Orbite Aluminae has developed an alternative solution to produce alumina from bauxite and aluminium rich clays without generating red mud.
Additionally, and unlike the Bayer process, it can also treat bauxite containing high levels of silicon, as well as kaolin, nephelite, and fly ash.
And significantly, Orbite’s technology has been shown to extract alumina from red mud residue. Orbite’s process uses hydrochloric acid and semi-continuous leaching to produce alumina suitable for use in aluminium smelters from most aluminous materials.
But at the same time, this new process can also recover other valuable raw materials including iron oxide, titanium dioxide, rare earth elements rare metals.
Orbite vice president, Yves Noel, collected the Canadian Green Chemistry and Engineering Award at the 64th Canadian Chemical Engineering Conference in Niagara Falls last week.
Speaking at a special presentation dinner, Noel told the audience: “We are turning an environmental and economic liability into an asset, transforming a waste into a host of valuable products. As a result, remediation project economics are no longer dependent on legislation-driven economics.”
Thanks to Orbite a solution to the red mud problem may be in sight. The world can continue to depend on aluminium without the safety and environmental pitfalls presented by current technology.