German scientists from the Max Planck Institute have developed a relatively simple technology for recycling toxic red sludge, a byproduct of aluminum production. It can be used to produce environmentally friendly steel using high temperatures. The study was published in the scientific journal magazine Nature.
The aluminum industry produces approximately 180 million tonnes of corrosive red mud each year, which is highly alkaline and contains traces of heavy metals. In Australia, Brazil and China, this waste is often dried and dumped in giant landfills, resulting in high recycling costs. During heavy rains, red mud is often washed away and then blown away as dust by the wind. Toxic sludge can erode the concrete walls of cemeteries, leading to leaks and causing environmental disaster.
Experts used a conventional electric arc furnace used in metallurgical industries. In it, waste is melted using plasma containing 10% hydrogen. As a result of the hydrogen reduction reaction, it can be easily recycled by separating it from the iron oxides contained in the sludge. The metal is so pure that it can be used immediately to produce steel.
The remaining oxides are no longer corrosive and harden into a glass-like material when cooled. It can be used in the production of fillers for the construction industry.
According to researchers, 4 billion tons of red mud have accumulated worldwide today. Approximately 700 million tons of steel can be extracted from here. If renewable electricity from green hydrogen (produced by splitting water) is used in the production process, steel production from slurry would avoid 1.5 billion tonnes of carbon dioxide emissions.
Previously in Russia was created Material made of chitin and clay for cleaning radioactive waste.