Over the last 5,000 years, gold has become one of man’s most coveted metals. This is because it’s conductive, non-corrosive and malleable, which makes it useful in applications which range from space exploration to jewelry and electronics. The downside is that traditionally, gold mining required a toxin called cyanide which has become banned in many countries, prompting extraction firms to find a safer alternative.

The Cyanide Replacement

An Aalto University research team in Finland was able to find a non-toxic cyanide replacement which is scalable. Their findings have been published inside Chemical Engineering, but to understand how it works, you have to know a little about how traditional gold extraction is done.

In the past, after gold ore has been mined from underground, it has to be crushed into powder then passed within a collection of tanks via the procedure named leaching. Cyanide was traditionally applied for separating gold from its ore inside a leached solution.

The Finnish researchers have discovered a process where the recovery and leaching are accomplished through the usage of chloride, which is one of 2 elements which comprise table salt. While attempts have been made in the past to recover small levels of gold via industrialized chloride solutions, until recently no one could figure out a way to do it.

With this procedure, the level of recoverable gold obtainable through the usage of cyanide has an efficiency which is around eighty four percent. By comparison, using the traditional cyanide technique only provides an ore yield of around sixty four percent within control experiments.

EDRR (Electrodeposition Redox Replacement)

EDRR is the name for this new process that merges the top 2 techniques for leached gold extraction. The first technique is electrolysis, which utilizes electrical currents for reducing gold presence within a leaching solution, and the second is cementation, where the particles of various metals are added to a solution so that they can react with gold.

By using EDRR, the team was able to use shortened electrical bursts to produce thin metallic layers of copper within the electrode, which produced the reaction which encouraged the gold to then replace a copper layer. The advantage of using this approach is that its energy consumption is low and will not necessitate adding more elements.

The research conducted by the Finnish University was actually part of the bigger European sustainability program named SOCRATES. The Finnish mining company Metso Outotec took a special interest in the project and collaborated closely with the researchers. In fact, the majority of the experiments were conducted within a research center owned by the company in West Finland.

Additional Advantages of This Non-Toxic Technology

Another problem with the gold extraction methods used in the past, aside from the dangers of using the poison cyanide, is that valuable metals were always left behind. Today, as the demand for metals continues to grow around the world, a lot of miners are realizing that even smaller amounts are essential, and with EDRR the Finnish team believes it’s possible to boost the yield.