From Rolf Clayton
David Cohen paints a pessimistic picture of the world’s remaining resources of a number of industrially important metals such as platinum, gallium and indium (26 May, p 34). However, the article did not explore sufficiently the possibility of exploiting the single largest resource of a wide range of industrially valuable metals – the sea.
For example, you gave world resources of copper as 937 million tonnes, yet there are around 1350 million tonnes in the sea; for gold the figures are 89,700 tonnes and 1.8 million tonnes in the sea; for indium 6000 tonnes and 9000 million tonnes; for uranium 3.3 million tonnes and 1350 million tonnes.
About 30 to 40 years ago a number of papers were published that examined the possibility of recovering metals from the sea, using ion-exchange technology. The proposal was that barrages, such as one across the UK’s Severn estuary, could incorporate huge banks of selective ion-exchangers that would selectively remove gold, uranium and other metals from the seawater. This would have achieved two objectives: the generation of tidal power and the recovery of industrially valuable metals.
Perhaps now is the time to go back to the past and re-evaluate these ideas.
Advertisement
London, UK
