Table 3.

Overview about the qualitative solubility of 30 metal oxides in the DES [Hbet]Cl/4U/2.5GLY at 150 °C compared to the IL [Hbet]₂[NTf₂]Cl at 175 °C. ^[40]

Metal oxide	Solubility in DES	Comment	Solubility in IL
Al2O3	Negligible	–	Negligible
BaO	Full	Clear, colorless solution after 5 min	Full, subseq. BaCl2 precipitation
Bi2O3	Negligible	(BiO)2CO3 formation instead of dissolution	Full, subseq. BiOCl precipitation
CaO	Full	Clear, colorless solution after 10 min	Full
CoO	High	Rapid blue coloration of solution, still undissolved reagent after 24 h	Full
Co3O4	High	Rapid blue coloration of solution, still undissolved reagent after 24 h	Full
Cr2O3	Negligible	–	Negligible
Cu2O	Full	Dark blue solution after 45 min	Full, subseq. CuCl precipitation
CuO	Full	Dark blue solution after 2 h, blue precipitate	Full
Fe2O3	Negligible	–	Low
FeOOH	Negligible	–	Full
Ga2O3	Negligible	–	Negligible
GeO2	Full	Clear, colorless solution after 1 h	Negligible
LiCoO2	High	Rapid blue coloration of solution, still undissolved reagent after 24 h	Full
MgO	Full	Clear, colorless solution after 1 h	Full
MnO	Full	Clear, slightly brownish solution after 10 min	Full
MnO2	High/Full	Depending on MnO2 purity brown solution after 3 h	Full
MoO3	Full	Brown solution after 1 h	Low
NiO	Negligible	–	Low
PbO	Full	Clear, colorless solution after 10 min	Full, subseq. PbCl2 precipitation
PbO2	Full	Clear, yellow solution after 10 min	Full
Sb2O3	Negligible	–	High
SnO	High	Dissolution and subsequent Sn6O4(OH)4 precipitation ageing to SnO	Full
SrO	Full	Clear, colorless solution after 10 min	Full
TiO2	Negligible	–	Negligible
V2O3	Low	–	High
VO2	Low	–	–
V2O5	Full	Dissolution and subsequent precipitation of amorphous solid	Full
WO3	Low	–	Negligible
ZnO	Full	Clear, colorless solution after 5 min	Full