The separation of the car catalyst material from the leaching solution was performed via centrifugation in a Microstar 12 tabletop centrifuge (VWR, Germany).
The leaching efficiencies of the PGMs in all systems before and after liquid–liquid separation were quantified with inductively coupled plasma–optical emission spectroscopy (ICP–OES) with appropriate sample dilution and matrix matching to accommodate for the high carbon content of the DES in the case of the leachates (1% EtOH in 5% HCl). The measurements were performed using a radial ICP–OES (Thermo iCAP 6500, Thermo Scientific, Waltham, MA, USA). A sample introduction kit consisting of a parallel path nebulizer (PEEK Mira Mist, Thermo Scientific, Ottawa, ON, Canada), a gas cyclonic spray chamber with a riser tube, and a torch injector tube with a 2 mm inner diameter was used.
1H-, 13C- and 31P-NMR spectra were recorded from CDCl3 and DMSO-d6 solutions on a Bruker AC 200 (200 MHz) or Bruker Avance UltraShield 400 (400 MHz) spectrometer. Chemical shifts (δ) were reported in ppm using tetramethylsilane as internal standard, and coupling constants (J) were given in Hertz (Hz). The following abbreviations were used to explain the multiplicities; s = singlet, d = doublet, t = triplet, q = quartet, quin = quintet, sext = sextet, m = multiplet.
The leaching efficiencies of the PGMs in all systems before and after liquid–liquid separation were quantified with inductively coupled plasma–optical emission spectroscopy (ICP–OES) with appropriate sample dilution and matrix matching to accommodate for the high carbon content of the DES in the case of the leachates (1% EtOH in 5% HCl). The measurements were performed using a radial ICP–OES (Thermo iCAP 6500, Thermo Scientific, Waltham, MA, USA). A sample introduction kit consisting of a parallel path nebulizer (PEEK Mira Mist, Thermo Scientific, Ottawa, ON, Canada), a gas cyclonic spray chamber with a riser tube, and a torch injector tube with a 2 mm inner diameter was used.
1H-, 13C- and 31P-NMR spectra were recorded from CDCl3 and DMSO-d6 solutions on a Bruker AC 200 (200 MHz) or Bruker Avance UltraShield 400 (400 MHz) spectrometer. Chemical shifts (δ) were reported in ppm using tetramethylsilane as internal standard, and coupling constants (J) were given in Hertz (Hz). The following abbreviations were used to explain the multiplicities; s = singlet, d = doublet, t = triplet, q = quartet, quin = quintet, sext = sextet, m = multiplet.