Abstract
The work describes the results of the first application of 2,6-bis(4-methoxybenzoyl)-diaminopyridine (L) for the recovery of noble metal ions (Au(III), Ag(I), Pd(II), Pt(II)) from aqueous solutions using two different separation processes: dynamic (classic solvent extraction) and static (polymer membranes). The stability constants of the complexes formed by the L with noble metal ions were determined using the spectrophotometry method. The results of the performed experiments clearly show that 2,6-bis(4-methoxybenzoyl)-diaminopyridine is an excellent extractant, as the recovery was over 99% for all studied noble metal ions. The efficiency of 2,6-bis(4-methoxybenzoyl)-diaminopyridine as a carrier in polymer membranes after 24 h of sorption was lower; the percentage of metal ions removal from the solutions (%Rs) decreased in following order: Ag(I) (94.89%) > Au(III) (63.46%) > Pt(II) (38.99%) > Pd(II) (23.82%). The results of the desorption processes carried out showed that the highest percentage of recovery was observed for gold and silver ions (over 96%) after 48 h. The results presented in this study indicate the potential practical applicability of 2,6-bis(4-methoxybenzoyl)-diaminopyridine in the solvent extraction and polymer membrane separation of noble metal ions from aqueous solutions (e.g., obtained as a result of WEEE leaching or industrial wastewater).
Highlights
Solvent extraction (SE), a process of separating metal ions from aqueous solutions by extraction into organic solvents immiscible with water, has been used for many years to recover various metals, both common and rare [1,2,3,4]
This paper describes the results of the application of 2,6-bis(4-methoxybenzoyl)diaminopyridine for the recovery of noble metal ions such as Au(III), Ag(I), Pd(II) and Pt(II) from aqueous solutions using SE and polymer membrane processes
The results of the current research have shown that separation methods such as classic solvent extraction and membrane extraction are effective in recovering precious metals from aqueous solutions
Summary
Solvent extraction (SE), a process of separating metal ions from aqueous solutions by extraction into organic solvents immiscible with water, has been used for many years to recover various metals, both common and rare [1,2,3,4] This well-established separation method has been widely used as a tool for the recovery of precious metals from different types of industrial waste, including waste electrical and electronic equipment (WEEE) [5,6,7]. This paper describes the results of the application of 2,6-bis(4-methoxybenzoyl)diaminopyridine (shown in Figure 1) for the recovery of noble metal ions such as Au(III), Ag(I), Pd(II) and Pt(II) from aqueous solutions using SE and polymer membrane processes. Despite the ability to form complexes with metal ions, so far 2,6-bis(4methoxybenzoyl)-diaminopyridine has not been used as an extractant in liquid–liquid extraction designed for the recovery of noble metals ions, nor as a carrier in polymer membranes
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