Abstract
In the current study, four new phenolic oxime ligands (HL1ox-HL4ox) containing diazo groups (-N$=$N-) were synthesized and used for liquid-liquid extraction of heavy metal ions [Cu(II), Ni(II), and Zn(II)]. The new compounds were characterized by analytical and spectroscopic methods. Solid-state structures of HL1ox-HL3ox were determined by single-crystal X-ray diffraction studies. Hirshfeld surface analysis of the compounds was performed to determine the contribution of different intermolecular contacts to the stability of the structures. The HL1ox-HL4ox ligands showed higher extraction performance for Cu(II) ion than Ni(II) and Zn(II) ions. The effect of pH on extraction capacity was investigated and the oxime compounds showed high extraction capacity at low pH values. The effects of the substitute groups (at the meta position of the phenol ring) on the extraction were investigated. Within the oxime ligands, the HL3ox compound exhibited higher extraction capacity for Cu(II) ions. The better extraction value of HL3ox is attributed to the weak hydrogen bond type interactions, which result in more stable complexes.
Highlights
Hydrometallurgy is often preferred to conventional pyrometallurgy by industry since it usually results in excellent materials and energy balances because of the reusability of the reagents.[1]
The HL1ox–HL4ox compounds were used for solvent extraction of metal ions
The oxime compounds (HL1ox–HL4ox) were obtained by the condensation reaction of the azo-aldehyde compounds with hydroxylamine in ethanol
Summary
Hydrometallurgy is often preferred to conventional pyrometallurgy by industry since it usually results in excellent materials and energy balances because of the reusability of the reagents.[1]. The metal ore is solved in an aqueous medium (leaching), and the metal to be recovered is separated and concentrated using liquid-liquid extraction and the resulting high-purity aqueous solution is reduced to generate the metal. 2 Solvent extraction has been widely applied to extract valuable metals from ore processing. 4 Conventionally, to recover the base metal, metal cations are transferred selectively to a water-immiscible phase by using ion-exchanger ligands, which release an equivalent number of cations, usually protons, back to the aqueous feed solution. 6 Copper production using phenolic oxime extractants accounts for approximately 25% of copper production in the world.[7] The sensitivity and selectivity of phenolic oxime extractants for Cu(II) compared to other base metal ions results from the more stable pseudomacrocyclic structure of the copper complex (Figure 1). The HL1ox–HL4ox compounds were used for solvent extraction of metal ions. The effects of time and pH on the extraction capacity were investigated in detail
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