Influence of Electrolyte Impurities from E-Waste Electrorefining on Copper Extraction Recovery

Jovana Djokić,Zlatko Nikolovski,Zoran Andjić,Dragana Radovanović,Željko Kamberović

doi:10.3390/met11091383

Abstract

In order to reflect possible issues in future sole e-waste processing, an electrolyte of complex chemical composition reflecting system of sole e-waste processing was obtained by following a specially designed pyro-electrometallurgical method. The obtained non-standard electrolyte was further used for the purpose of comprehensive metal interference evaluation on the copper solvent extraction (SX) process. Optimization of the process included a variation of several process parameters, allowing determination of the effect of the most abundant and potentially the most influential impurities (Ni, Sn, Fe, and Zn) and 14 other trace elements. Moreover, comparing three commercial extractants of different active chelating groups, it was determined that branched aldoxime reagent is favorable for Cu extraction from the chemically complex system, as can be expected in future e-waste recycling. The results of this study showed that, under optimal conditions of 20 vol.% extractant concentration, feed pH 1.5, O/A ratio 3, and 10-min phase contact time, 88.1% of one stage Cu extraction was achieved. Co-extraction of the Fe, Zn, Ni, and Sn was under 8%, while Pb and trace elements were negligible. Optimal conditions (H2SO4 180 g/L, O/A = 2, and contact time 5 min) enabled 95.3% Cu stripping and under 6% of the most influential impurities. In addition, an impurity monitoring and distribution methodology enabled a better understanding and design of the process for the more efficient valorization of metals from e-waste.

Highlights

Resource shortage, environmental and human health issues, and economic incentives have promoted recycling to become mandatory in the modern world
Selected e-waste fractions were used as feed in a specially designed pyro-electrometallurgical processing, which allowed for the generation of an electrolyte of extremely complex chemical composition and high abundance of impurities
The obtained electrolyte burden with Ni, Sn, Fe, and Zn, and 14 trace metals were used in numerous solvent extraction experiments in order to define optimal conditions for the selective Cu extraction-stripping process

Summary

Introduction

Environmental and human health issues, and economic incentives have promoted recycling to become mandatory in the modern world. Efforts to reduce natural exploitation, preserve the environment, and promote the reuse and valorization of previously discarded materials, thereby minimizing process waste, have become one of the most important goals. In terms of metal content, printed circuit boards (PCB) are the most valuable part of e-waste, containing more than 60 elements of the periodic table, from 28% [2] to 40% [3] of metals, including base and precious metals, rare, scarce elements, and hazardous, toxic, metals. Besides metals, this material contains various organic compounds. The application and significance of the electrometallurgical approach in the production of metals from solution are given in a detailed review by Rai et al, emphasizing that there are limitations in e-waste processing due to the complexity of the material itself [8]

Methods

Results

Conclusion