Effect of N-substituents on performance of thiourea collectors by density functional theory calculations

Using density functional methods, some properties were studied such as the energies and compositions of frontier molecular orbitals and the atomic charges, which are related to the reactive behavior of thioureas containing different N-substituent groupings. The calculation results indicate that the N-substituent groupings have significant effect on the flotation performance of thiourea collectors. The order of electron-donating ability is N-propyl-N′-benzyl-thiourea (PBZYTU)>N-propyl-N′-ethyl-thiourea (PETU) >N-propyl-N′-allyl-thiourea (PALTU)≫ N-propyl-N′-acetyl-thiourea (PACTU) >N-propyl-N′-ethoxycarbonyl-thiourea (PECTU) >N-propyl-N′-benzoyl-thiourea (PBZOYTU), and the order of feedback-electron-accepting ability is PBZOYTU>PACTU>PECTU≫ PALTU>PETU>PBZYTU. This implies that PBZOYTU, PACTU or PECTU can react with copper atoms having (t2g)6(eg)3Cu(II) or t6e4Cu(I) configuration on the surfaces of copper sulfide minerals through normal covalent bond and back donation covalent bond, and exhibit excellently collecting performance for copper sulfide minerals. These are consistent with the experimental data reported in the literatures.