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Process Safety and Environmental Protection, Vol.121, 1-11, 2019
Chelating extraction of metals from e-waste using diethylene triamine pentaacetic acid
In this study, the chelating extraction of base metals namely, Cu, Zn, Ni from printed circuit board (PCB) of obsolete computer was carried out using diethylene triamine pentaacetic acid (DTPA) as a safer ligand. At a liquid to solid ratio (L/S ratio) of 50 and the comminuted PCB in the size range of 0.038-1 mm, the maximum extraction of around 97% Cu at 4.5 d and more than 99% each of Zn and Ni at 3 d was achieved using 0.5 M DTPA at pH of 9, temperature of 50 C and mixing speed of 450 rpm. Using 0.9 M H202 under optimized process conditions, around 99% Cu and 82% Ni leaching were achieved in 8 h along with complete leaching of Zn in 1 h only. Kinetics development using the shrinking core model (SCM) indicated that the metal extraction from the PCB comminution fines using DTPA is controlled by diffusion process. Further, metal recovery of around 98% each for Cu and Ni and 95% for Zn was achieved by the chemical precipitation of the leachate. Chelating extraction using DTPA coupled with the chemical precipitation of the leachate has the potential to emerge as a complete solution for metal recycling from e-waste. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.