Reclamation of copper from spent ammoniacal Printed Circuit Board (PCB) etch solutions. Issue 2 (April 2018) - Shah, Khyati
Highlights: Copper (51.8 g/L) is extracted from spent ammoniacal etch solutions using LIX84I. Quantitative extraction with 50%LIX 84I at O/A1.5 in three counter-current stages. Ammonia transfer in oil phase was insignificant due to maximum copper loading. Precipitation-stripping resulted in 98.57% recovery of copper as copper oxalate. High purity copper oxide obtained as value added product. Abstract: Ammoniacal spent etch liquors is a potential source for copper recovery. In the present investigation copper was extracted from spent ammoniacal PCB etch solutions using hydroxyoxime LIX 84I. Maximum extraction was observed at equilibrium pH of 8.9. Three counter-current stages were required for quantitative extraction of 51.8 g/L copper from the spent liquor using 50%v/v extractant at an O/A ratio of 1.5. It was also possible to achieve quantitative extraction with 20% v/v extractant concentration at an equilibrium pH of 8.9 and O/A ratio 4.5:1. Precipitation −stripping of the loaded organic phase using oxalic acid led to reclamation of copper as copper oxalate. Contacting the oil phase fully loaded with copper in 50% v/v extractant, with 1 M oxalic acid at equal O/A resulted in 77.4% copper getting stripped in first contact, quantitative stripping was achieved in the second contact with fresh acid. There was a close agreement between the experimental and predicted yields based on solubility plots developed for copper-oxalic acid system. Co-extracted ammonia to the organic phase was stripped as soluble ammonium oxalate offering an inherent advantage over the conventional stripping process where build-up of ammonium sulphate is observed during electrowinning process. Calcinations for three hours formed copper oxide, XRD and chemical analysis confirmed the formation of pure copper oxide. The copper present in waste etchant could thus be appropriately converted to value added product.