Use of extraction chromatography in the recycling of critical metals from thin film leach solutions

Phosphors and optoelectronic thin film electronic device layers contain critical metals including lanthanides and indium that should be recycled. Solvent impregnated resins (SIRs) containing (i) DEHPA (ii) DODGAA and (iii) DODGAA with the ionic liquid [C(4)mim][Tf2N] are investigated in extraction chromatography methodologies to recover and separate critical metals from dilute solutions that model those leached from thin films. Optimum adsorption of metals occurs at pH 1.5-3.5 but is highest on DODGAA-[C(4)rnim][Tf2N]. The recovery and separation of adsorbed metal species on the DODGAA-[C(4)mim][Tf2N] SIR resin from solutions containing the glass matrix ions, Ca(I1) and Al(III), along with In(111) and Sn(IV) or lanthanide ions is achieved by elution with HNO3. Ca(II) and Al(III) are completely eluted with 0.1 M HNO3 retaining the target critical metal species on the resin. Separation of In from Sn is achieved by elution of In(III) with 2.5 M HNO3 and Sn(IV) with 5 M acid. La is separated from the other lanthanides by elution of La(III) with 2.5 M HNO3 and the remaining lanthanides with 5 M acid. The SIR resins can be reused over a series of at least five cycles of loading, stripping, and rinsing to reduce reagent costs and achieve economic critical metal recovery by extraction chromatography. (C) 2016 Published by Elsevier B.V.