Electrochemical Replacement Plating: The value of a historical technique in addressing contemporary issues

This paper presents new jewellery & silverware that was created from a residency at the Love Chemistry Group part of Edinburgh University. The Love group have developed a new chemical compound or ligand that uses hydrometallurgy (a green method) to select gold from a solution of metals recovered from electronic waste. The residency was an opportunity to experience the hydrometallurgy process using computer circuit board fingers that I purchased from ebay and experiment with different surface finishes possible with metals in solution. I worked with an area of chemistry called ‘electrochemistry’. This is a branch of chemistry that looks at ‘reduction’ and ‘oxidation’ reactions, commonly referred to as ‘redox reactions’ where the electrons of one metal compound in solution will be lost while the other solid metal will gain electrons. This exchange of electrons creates a force measured in volts hence the name electrochemistry. Effectively this is a form of plating known as electrochemical replacement plating. This is sometimes also referred to as electrochemical displacement plating. We know from the electrochemical series, that is the list of metals arranged in order of how easily the metal atoms lose electrons, that some metals are more reactive than others. For example, silver ions are oxidising, therefore should oxidise copper (remove electrons) to form copper ions and, at the same time, deposit silver metal. But this wouldn’t work the other way around – ie copper will not deposit onto silver as it is more reactive than silver. I experimented with droplets of different solutions from the metal recovery process on small pieces of different silver alloys to see what effects could be achieved. The first solution containing all of the metals recovered (Copper, gold, cobalt, iron etc) created a beautiful effect, with the copper (the largest quantity of metal extracted) contained in the solution crystallizing around the edges as it dried out. These droplets were around one centimeter in diameter. I created a time-lapse video of this process, in which around three-and-a-half hours is condensed into a one-minute sequence. This result is fairly robust and does not break off the silver easily.