A DFT study on the structure-reactivity relationship of aliphatic oxime derivatives as copper chelating agents and malachite flotation collectors

Aliphatic oxime derivatives C7H15CX=NOH (X= H, CH3, NH2 or OH) have been commercially used as copper(II) extractants or flotation collectors, but the true nature of their reactivity toward Cu2+ or mineral surfaces still remains elusive. Using density functional theory (DFT) method, the structure-reactivity relationship of these aliphatic oxime derivatives was evaluated at B3LYP/6-311 + G(d, p) level. The results indicated that the O or N atoms in the head group of octanaldoxime (OTAO), methyl n-heptyl ketoxime (MHKO), N-hydroxyoctanimidamide(HOIM) and n-octanohydroxamic acid (OTHA) are the chemical reaction center. The reactivity of the aliphatic oxime ionic species increases successively with the replacement of hydrogen atom by methyl, amino and hydroxyl, suggesting that the affinity of them to copper species is as follows: OTHA > HOIM > TAO > MHKO, which coincides with the order of their binding energy toward Cu2+. The flotation performance of aliphatic oxime derivatives to malachite was in the order of OTHA > OTAO > HOIM > MHKO, which was in line with the combination effect of their reactivity and hydrophobicity. The established structure-reactivity relationship provides an atomic level understanding of the structural requirements for aliphatic oximes to recover cupric ions or copper oxide minerals. (C) 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.