Recycling metals from industrial waste

Researchers at Brunel University have developed an electrochemical process for the recovery of precious and heavy metals from industrial waste, which could reduce water treatment and cut landfill costs.

Instead of paying for the treatment of wastewater and the disposal of contaminated sludge, companies will be able to recycle and sell valuable metals such as cobalt, copper and iridium.

The Brunel team has developed a new type of electrochemical cell. Known as a concentrator cell, it increases efficiency by concentrating metal ions close to one of the electrodes (usually the cathode). This reduces the distance that ions have to travel - in effect creating a new cell with a concentrated electrolyte at the electrode.

Concentrator cells are suitable for in-process and end-of-pipe recovery installations. They maintain a constant pH, so there is no need to add alkali as in standard cells. In addition, they can simultaneously remove organic pollutants that would reduce metal recovery efficiency and contaminate wastewater.

Results of trials show that concentrator cells can successfully treat metal solutions commonly produced in processes ranging from plating to etching of printed circuit boards, refining of platinum group metals and printing. The cells are also effective at recovering high value metals such as iridium and silver, as well as toxic heavy metals such as lead and cadmium.

Potential cost savings of £6,000/t have been achieved in a typical application to recover cobalt from mining waste. With iridium, a difficult metal to recover, a concentrator cell can recover 80% of the metal waste.

Concentrator cells can also be combined with photolytic cells to achieve simultaneous destruction of organic contaminants alongside the collection of metals.

Brunel University (01895) 274000



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