Molecular dynamics insight into the behaviour of 5-nonylsalicylaldoxime and its complex with Cu(II) in different diluent/water systems

Abstract

The solvent extraction is a well-established method for separation and purification of copper. The performance of ubiquitous components in the process affects the extraction efficiency. A study on the molecular behaviour of 5-Nonylsalicylaldoxime (NSAO) and its complex with copper (Cu-NSAO) in three different diluents (toluene, cyclohexane and decane)/water systems is presented. The effects of diluents on the separation of phases and their solubility in the aqueous phase were investigated by use of non-bonded interaction analyses. The results showed excellent agreement with the reported experimental data. Moreover, the diluent effect on the thickness of interfacial zones was studied in diluent/water systems. Cyclohexane had a satisfactory performance at the interface region in all simulations. After that, the behaviour of NSAO at the interface and depth of two phases was investigated. At the beginning of the simulations, the NSAO molecules had an unusual situation (polar head is located into the organic phase while long alkyl tail into the aqueous phase) at the interface. During the simulations, the position and orientation of NSAO molecules changed. After a while, NSAOs became parallel to the interface and then completely orientated to the right position (the polar head is pointed towards the aqueous phase while hydrophobic tail into the organic phase). The results of non-bonded interaction between NSAO and water molecules indicated that the hydrophilic/hydrophobic property of extractant was significantly influenced by the type of diluent. On the other hand, the NSAOs that were placed at the depth of organic and aqueous phases, they migrated towards the interface and adsorbed there. Finally, three Cu-NSAO complexes were placed at the interface of diluent/water system. The results showed that the complexes migrated to the depth of organic phase to decrease steric hindrance.