Industrial technology for mass production of SnO_2 nanoparticles and PbO_2 microcube/microcross structures from electronic waste

摘要

Waste Printed Circuit Boards (WPCBs) are one of the major recycling challenges in this century with Through-Hole Solder Joint (THSJ) components representing more than 40 wt% of their metallic fraction. THSJs are composed mainly of three metals - Cu, Sn, and Pb; in addition, THSJs can contain a very small amount of Pd and other additives such as Ni, Fe, 111, etc. Recently, dissolution treatment has successfully been used to liberate THSJs as received as well as copper foils, contacts, and tracks. In order to close the lifecycle loop of WPCB metallic fraction, this research has an aim to recover Sn and Pb from the liberated THSJs in the form of SnO2 nanoparticles and PbO2 micro cross/cubic structures as high added-value products using sustainable leaching technique. Nitric Acid was employed to prepare leaching solution, whereas ultrasound treatment was used to precipitate SnO2 and PbO2 precursor from the solution. With time, particles of other metals (Pd, Ni, Fe, Al, etc.) started to precipitate, acting as catalysts (or doping agents) and increasing the precipitation of SnO2 and PbO2. Under the effect of sound waves, temperature, and catalysts, SnO2 and PbO2 precursors transformed into nanoparticles and micro cross/cubic structures; formation and refining degree of these structures was controlled by changing the treatment time. Micro-filtration process was used to separate SnO2 nanoparticles from PbO2 microstructures. Also, copper was recovered from the remaining acidic solution as a Cu(OH)(2) by neutralization with NaOH at pH 8. SEM-EDS, TEM, FTIR, XRD, and ICP were used to examine the extracted THSJs, produced nano/micro products and recovered metals. The results showed that the SnO2 and PbO2 had average sizes of 7 nm and 1 pm respectively, while the preparation costs were 6 times lower in comparison to the commercial counterparts. Finally, the authors suggested a layout for applying the developed approach on an industrial scale while referring to the concepts of Circular Economy and Sustainable Development. (C) 2018 Elsevier Ltd. All rights reserved.