Recycling of Precious Metal Gold from Waste Electrical and Electronic Equipments (WEEE): A review

Abstract

Gold finds a wide range of application in electronic devices i.e. in mobile phone PCBs, coated plates, connectors etc. This is because of its high conductivity, ability to carry low ampere current, high sensitivity and resistance to corrosion. Due to the increasing demand of electronic devices conventional reserves of gold are depleting. At the same time life of electronic goods is decreasing because of rapid changes in device features and abilities. This produces a large amount of obsolete electronic gadgets which gradually results into a large amount of electronic waste. Even during production of electronic products, steps involved generate waste water containing gold which can be recycled. In order to meet the increasing demands and conserve resources, it is necessary to recycle the e-waste generated. Gold recovery is also necessary because of its high market value and vast application in different fields such as jewelry, coinage, medical appliances etc. Recovery of gold from e-waste has gained attention because of its concentration in e-waste which is around 100 times more than that is found in gold ores. The present paper gives an idea of the various hydrometallurgical processes such as cementation, adsorption, solvent extraction etc used in the recovery of gold from electronic scrap. The paper also highlights the use of different types of leachants such as Cyanide, Thiourea, Thiosulfate etc. for the recovery of gold. Chemical reactions and the process parameters viz. pH, temperature, concentration of leachant, pulp density, stirring speed etc. involved in different processes are also reported. Based on the review made, some flow sheet and recommendations have been proposed for effective and feasible recovery /recycling of gold from e-waste.