Fixed-bed column study for gold recovery from e-waste leaching solution using glutaraldehyde-crosslinked-chitosan beads

Abstract

Electronic waste (e-waste) has received increased attention as an alternative source of metals in the framework of urban mining. In particular, recovery of gold from e-wastes such as printed circuit board (PCB) has become increasingly attractive due to its high gold content and economic value. Hydrometallurgical methods have been used for the gold recovery from e-waste, in which acid leaching, separation/concentration, and recovery processes are typically applied. Glutaraldehyde-crosslinked chitosan (GCC) beads are a low-cost bio-adsorbent and capable of effectively separating auric ion (Au3+) from acidic leaching solutions of a PCB sample. The objective of this study was to design and optimize a fixed bed column using GCC beads as a novel gold recovery process from e-waste. Laboratory scale column experiments were conducted to derive and compare the breakthrough curves of gold at three different conditions for the column diameter and flow rate combination (i.e., 15 mm & 1.0 ml/min, 20 mm & 1.8 ml/min, and 30 mm & 4.0 ml/min) while keeping the linear flow rate at 0.57 cm/min. Similar gold breakthrough curves were observed for the three tested columns, and the effluent gold concentration reached the 5% of the influent at the operation time of ~900 hours. This result supports that the column scale up can be achieved by increasing the diameter and flow rate with keeping the constant linear flow rate of 0.57 cm/min. The efficiency of gold's desorption from the GCC was evaluated in batch and column experiments by testing the effects of desorption reagent composition (thiourea/HCl) and temperature. In the batch tests, ~90% of gold recovery rate could be achieved by using 1 M thiourea & 1 M HCl at the temperature of 75 oC, while only ~56% of gold recovery rate was achieved in the column tests, requiring further optimization of the desorption.