London, July 8 : Japanese scientists have suggested that newsprint is a vital ingredient in a new process for recovering gold and other precious metals from industrial waste metal solutions.
Though old electronic consumer devices such as computers, televisions and mobile phones are an important source of precious metals, recovering them isn't easy and usually requires large quantities of chemicals that are known to damage the environment.
According to a report in New Scientist, now, a team of Japanese chemists has said that it can do a similar job using inexpensive and renewable materials.
Katsutoshi Inoue and colleagues at Saga University in Japan, crushed and washed old newspapers and then combined the pulp with a chlorine compound.
The chlorinated paper was then treated with dimethylamine (DMA) and formaldehyde to form what they call a DMA-paper gel. Finally, this is dried to powder form.
Inoue's team tested the DMA-paper gel's ability to bind to, or adsorb, metal using a standard industrial sample consisting of a liquor produced by dissolving old metallic components in hydrochloric acid.
The liquor contains the common metals copper, zinc and iron, each in concentrations ranging from 190 to 840 parts per thousand.
However, it also contains 250 parts per million of gold and 11 to 16 parts per million of platinum and palladium.
The gel turned out to be highly selective in the metals it adsorbed. It took up over 90% of the gold, platinum and palladium, but almost negligible quantities of copper, zinc and iron.
The waste paper is a crucial part of the gel's structure: the amorphous nature of the cellulose within the paper allows chemicals to penetrate easily into its matrix and leads to a high carrying capacity - one kilogram of gel can hold 906 grams of gold.
"And you can use the gel again after the metal (is removed)," said Chaitanya Raj Adhikari, a member of Inoue's team.
"Our gel is prepared from inexpensive, renewable resources and it has high selectivity and capacity for precious metals," according to Adhikari. "Those properties make it a wonderful adsorbent," he added.