Forecasting of Perspective Flotation Reagents on the Base of Structure Based Virtual Screening
The molecular models of complexes of poorly studied mineral clusters and reagents in developing the principles of evaluation of forecasting in flotation reagent activity have been created and optimized by using Chem Bio 3D and ChemOffice2005 by Cambridge Soft with optimization by MM2. It is proposed to use structure based virtual screening (SBVS) and reduce enormous amount of chemical compounds to a more manageable number for synthesis and screening which could lead to potential flotation candidates. The metal tellurides and arsenic sulfides as poorly explored types of minerals have been investigated. HOMO, SOMO, LUMO and total energies, atomic charges and s, p, d-population were determined for the various compounds. The strategy of prognosis of collector activity evaluation (PCAE) has been proposed as a consistent approach to estimate the interaction between a collector and a mineral cluster to search the analogue of butyl xanthate. The relationship between PCAE and flotability has been established. Our results indicate that the lower PCAE the stronger the interaction between the collector and the mineral cluster. The binary complexes of various reagents on the mineral surface have been studied. It was shown that the lowest magnitude of PCAE was obtained for arsenopyrite with binary mixture of dibutyl dithiophosphoric acid and diethylaminoethyl xanthic acid that indicated the high chemical activity of the combination of reagents. Forecasting of perspective flotation reagents by screening of chemical compounds and theoretical results obtained from research can provide a basis for innovative technology in mineral processing.
Effect of N-substituents on performance of thiourea collectors by density functional theory calculations
Abstract 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 (t 2g ) 6 (e g ) 3 Cu(II) or t 6 e 4 Cu(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.
Solution properties of thionocarbamate collectors
Abstract Potentiometric titrations, solubility measurements, ultraviolet (UV) and Fourier Transform Infrared (FTIR) spectroscopy were used to investigate the solution properties of the copper sulfide collectors, O-isopropyl-N-ethyl thionocarbamate (IPETC) and O-isobutyl-N-ethoxycarbonylthionocarbamate (IBECTC). The molar absorptivity spectra of IBECTC and IPETC were monitored as a function of pH. IPETC exists as a single, spectroscopically distinct, neutral species in aqueous solution to a pH value of at least 10.5. Three clearly defined isosbestic points appear in the molar absorptivity spectra of IBECTC with increasing solution pH and indicate the presence of at least two spectroscopically distinct species, representing acidic and basic forms of the collector. The p K a (8.1) and molar absorptivity spectra of the basic species of IBECTC were calculated from the UV spectra. A similar p K a value for IBECTC was found by potentiometric titration. Solubility studies confirmed these observations, demonstrating that the basic form of IBECTC is more than ten times more soluble than the acid form. Based on FTIR studies, a molecular configuration of IBECTC − is proposed. Microflotation studies of chalcopyrite, performed as a function of pH in the presence of these collectors, showed a recovery-pH response which correlated with the collectors' solution behaviour.