Simple and complete separation of copper from nickel in the ammoniacal leach solutions of metal coated ABS plastic waste by antagonistic extraction using a mixture of LIX 84-I and TBP

A solvent extraction-based method using mixed extractants of LIX 84-I and TBP has been developed for complete separation of copper from nickel in the ammoniacal leach solutions of ABS plastic waste. The selective separation of copper was facilitated by the antagonistic effect of the extractants on depressing nickel extraction. The FTIR spectra indicated the possibility of hydrogen bonding between H-atom of hydroxyl group of LIX 84-I and O-atom of phosphoryl group of TBP while lowering the availability of extraction sites of LIX 84-I and increasing the bulky alkyl groups in the organic phase, causing the antagonism desired for Ni extraction. A McCabe-Thiele diagram of copper exhibited that a four counter-current stage at operational conditions of 0.5 M LIX 84-I + 0.5 M TBP, aqueous/organic (A/O) phase ratio of 1.3/1 and 25 degrees C was required to achieve the quantitative selective extraction of copper from real solution of ABS plastic waste with Cu2+ and Ni2+ concentration of 8.14 and 2.57 g/L, respectively, without any coextraction of nickel to the organic phase. Complete stripping and enrichment of copper was reached after a three counter-current stage using 2.0 M H2SO4 solution at O/A phase ratio of 2/1; copper in the stripped solution was found to be 21.03 g/L. Recycling of the mixed extractants for reuse in copper and nickel separation was demonstrated, and thereafter, a recommended flowsheet of recycling metals from ABS plastic waste was given. The antagonistic extraction system comprising of oxime-based extractant, LIX 84-I, and organophosporus extractant, TBP, presented in this study shows a potential for sustainable metal separation process.

Automated summary

A new method using mixed extractants of LIX 84-I and TBP was developed for complete separation of copper from nickel in ammoniacal leach solutions of ABS plastic waste. Antagonistic effect of the extractants on depressing nickel extraction facilitated the selective separation of copper. The system showed a potential for sustainable metal separation process through recycling of mixed extractants.