INVESTIGATION OF THE EFFECT OF N-SUBSTITUENTS ON PERFORMANCE OF THIOUREAS AS SPECIAL COLLECTORS FOR COPPER SULFIDES BY AB INITIO CALCULATIONS

摘要

Using ab initio methods, the chemical parameters such as the energies and compositions of frontierrnmolecular orbitals (FMOs) and the sulfur atom charges indicating the reactive behavior of thioureasrncontaining different N-substituent groupings were theoretically determined. The results of therncalculations indicated that the efficiencies of N-substituent thioureas depend on the investigatedrnparameters, and the N-substituent groupings have significant effect on flotation performance ofrnthioureas as selective collectors for copper sulfide minerals. The order of electron-donating ability isrnN-propyl-N′-ethyl-thiourea (PETU) > N-propyl-N′-benzyl-thiourea (PBZYTU) > N-propyl-N′-allylthiourearn(PALTU) N-propyl-N′-benzoyl-thiourea (PBZOYTU) > N-propyl-N′-ethoxycarbonylthiourearn(PECTU) > N-propyl-N′-acetyl-thiourea (PACTU), and the order of feedback-electronacceptingrnability is PBZOYTU > PACTU > PECTU PALTU > PBZYTU > PETU. This impliesrnthat PBZOYTU, PACTU or PECTU can react with copper atoms having (t_(2g_)~6(e_g)~3Cu(II) or t~6e~4Cu(I)rnconfiguration on the surfaces of copper sulfide minerals through normal covalent bond and backrndonation covalent bond, but the interaction of PBZOYTU, PACTU or PECTU with iron atoms havingrnt_(2g))~6(e_g)°Fe(II) or (t_(2g)~a)~3(e_g~a)~2Fe(III) configuration on the surface of iron sulfide minerals is weak.rnPBZOYTU, PACTU or PECTU should have excellent performance as flotation collectors with improvedrncollecting power for copper sulfide minerals and selectivity against iron sulfide. The theoreticallyrnobtained results for PECTU are consistent with the experimental data reported in the literature, andrnthe theoretical results for PBZOYTU or PACTU will be proved by flotation tests in the future.