Abstract
The current study presents an effort to develop a sustainable hydrometallurgical process for the recovery of copper from waste printed circuit boards (PCBs) to be applied at local small to medium industrial units. The process aims to separate and recover copper from filter dust produced during the crushing of PCBs using a hammer mill in a recycling facility. Due to the high plastic content in the dust (approximately 30% w/w), the metal fraction was separated gravimetrically, and the material originated consisted mainly of Cu (23.8%), Fe (17.8%), Sn (12.7%), Pb (6.3%), Zn (3.4%), Al (3.3%), Mn (1.6%), and Ni (1.5%). Prior to copper recovery, the dust was leached with HCl as a pretreatment step. During this step, more than 80% of iron, zinc, and tin were leached out. The resulting solid consisted mainly of Cu (37.6%) and Fe (10.7%), leading to a copper enrichment of around 60% in the powder. The leaching of copper was conducted in a two-step process using H2SO4 as a leaching agent with the addition of H2O2 as an oxidizing agent. The experimental conditions had low energy requirements (no heating or agitation needed). The leaching of Cu reached 98%. Despite the pretreatment step, the concentration of other metals (Fe, Zn, Ni) in the pregnant solution was too high to proceed to electrowining. Therefore, the organic solvent ACORGA M5640 was selected for the extraction of copper from the pregnant solution. The extraction was conducted in two stages at pH equilibrium 1.5, and the loaded organic phase was stripped with HCl in two steps. The strip liquor was suitable for electrowinning.
Highlights
In the last decades, the amount of electric devices in the market has increased
This study, part of the HYDROPCB project (Development of a hydrometallurgical process for metal recovery from Printed Circuit Boards in pilot scheme: A zero waste process), presents the results obtained in an effort to selectively recover copper from filter dust, produced during the crushing of printed circuit boards (PCBs) in a hammer mill at a local recycling facility (ECORESET SA)
The dust composition in plastic material was determined by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC)
Summary
The demand of raw materials in electric devices has increased [1]. Wasted printed circuit boards (PCBs) contain the highest concentrations of base and precious metals [3]. It is of great importance for them to be recycled. Sustainable metallurgical processes for metal recovery from e-wastes can be scaled up by local small to medium industrial units [8]. This study, part of the HYDROPCB project (Development of a hydrometallurgical process for metal recovery from Printed Circuit Boards in pilot scheme: A zero waste process), presents the results obtained in an effort to selectively recover copper from filter dust, produced during the crushing of PCBs in a hammer mill at a local recycling facility (ECORESET SA)
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