Selective recovery of tungsten from printed circuit board recycling unit wastewater by using emulsion liquid membrane process

Aqueous waste containing low concentrations of tungsten are generated during printed circuit board (PCB) or e-waste recycling process. Study has been initiated to develop a suitable emulsion liquid membrane (ELM) technique for the separation and recovery of tungsten [W(VI)] from such waste using Aliquat 336 in hexane as a carrier and sodium hydroxide as a stripping agent. The waste, having a composition of nearly 600 ppm W(VI), 150 ppm Pb(II) and below 5 ppm concentrations of Cu(II), Mn(II), Zn(II), Co(II), Ca(II), Mg(II), Na(I) and K(I) at pH 5, was used as the feed phase. Various factors that affect the emulsion stability, as well as percentage extraction of W(VI), have been optimized to obtain maximum enrichment of W(VI). An attempt was made to recover W(VI) without making any substantial changes to the waste composition. Under optimized conditions, the extraction percentage of W(VI) was found to be 80% with 4 times enrichment in stripping phase. The separation factor for W(VI) vs. other co-ions was found to be very high thereby indicating selective recovery of W(VI) from the wastewater by using ELM process. (C) 2015 Elsevier Ltd. All rights reserved.