Preliminary Study of Hydrometallurgical Extraction of Silver from Selected E-Waste

Abstract

Electronic relays (ER) are a type of switch which are an essential part of electronic devices used to open or close circuits by using electronic components without any mechanical operation. After decommissioning, it can be considered as an important source of base and precious metals with high economic value. The annual growth rate of about 4-5 % in 2016 is one of the fastest growing waste stream, and only about 20 % of e-waste is recycled. After the use-phase, electronic devices become electronic waste (e-waste); consequently, it is important to consider e-waste as a secondary supply for the recovery of precious metals. In this study, a simple hydrometallurgical recovery method for silver (Ag) extracting from used electronic relays was performed. The silver extractions consisted of six stages: disassembling of relays, removal of base metals, leaching in nitric acid, precipitation, conversion silver oxide and melting. Measurements of extracted precious metals were carried out by scanning electron microscope (SEM) and EDS (Energy Dispersive Spectrum) analysis. The purity rate of the final deposit was 94.9 % on the surface of the sample, and the final silver recovery yielded 0.44 % of the raw material. During the second stage of the experiment, mixed types of electronic relays were used to compare the yields. Electronic relays can be considered as an important source of base and precious metals with high economic value. The final yield of the mixed electronic relays reached up to 0.54 % of Ag with the purity of over 95 %.