Selective solvent extraction of Cu(II) from aqueous solutions using an acyl-based thiourea: Extraction study and DFT analysis of reaction mechanism

Currently, copper-containing wastewater poses a great threat to the surrounding living areas due to its toxic and non-biodegradable properties. The solvent extraction technique for removing copper(II) from wastewater has been identified as a straightforward and effective method. In this study, novel acyl-containing thiourea extractants, namely N-benzoyl-N′,N′-diethyl thiourea (BDETU), N-benzoyl-N′,N′-dibutyl thiourea (BDBTU) and N-benzoyl-N′-butyl thiourea (BBTU), were prepared and employed as extractants for the efficient removal of Cu(II) ions from aqueous solution. Experimental results indicated that the highest extraction efficiency of Cu(II) by BDETU was 99.4% under the optimal extraction conditions, which surpassed the performance of both BDBTU and BBTU. The reusability and selectivity experiments further confirmed the enduring high extraction efficiency of BDETU over 8 consecutive extraction-stripping cycles. These findings suggest that BDETU exhibits promising prospects for wide-ranging applications owing to its excellent extraction stability and selectivity. The investigation into the extraction mechanism of Cu(II) with acyl thiourea molecule revealed that one mole of Cu(II) was extracted with two moles of extractants through the formation of Cu-O-C and Cu-S-C bonds.