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3 Physicochemical Problems of Mineral Processing

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Homogenization phenomena of surface components of fluorite and calcite

100%

Sun R. , Liu D. , Zhang B. , Lai H. , Wen S.

tom Vol. 57, iss. 1

250--258

The flotation separation of fluorite and calcite poses one of the most difficult problems in the mineral processing industry. In particular, the surface homogenization of fluorite and calcite worsens the result of fluorite flotation. In this paper, time of flight secondary ion mass spectrometry and principal component analysis are used to study the surface homogenization of fluorite and calcite during grinding and in solution using X-ray photoelectron spectroscopy, infrared spectroscopy, and solution chemical calculations. The results show that the surface composition of calcite converts to fluorite after mixed grinding and that the surface composition of fluorite also converts to calcite in clarified calcite solution.

New insights into pyrite-hydrogen peroxide interactions during froth flotation : experimental and DFT study

100%

Cao Q. , Yan W. , Wen S. , Liu D. , Li Y.

tom Vol. 59, iss. 1

art. no. 157409

Hydrogen peroxide (H2O2) is an efficient depressant for pyrite (FeS2) flotation. However, the depressing mechanism of H2O2 is not fully understood. In this paper, the depressing capacity of H2O2 for pyrite was examined by flotation tests. Results revealed that pyrite flotation could be inhibited by H2O2 at pH 6.4. The pyrite powder in H2O2 solution enhanced the release of O2 from H2O2. However, the O2 concentration in the solution was less than that of H2O2; thus, H2O2 is the major oxidant in the solution. Moreover, density functional theory calculations were performed to study the interactions between H2O2 and hydrated pyrite (100) surface. The H2O2 molecule tended to react with the pyrite surface to generate one S=O bond and an H2O molecule. The possible binding models of O2 molecules on the pyrite (100) surface were also studied for comparison. The O2 dissociation on the pyrite surface was more favorable than the adsorption of O2 as a whole. In addition, the orbital interaction in the S=O bond raised from the reaction of H2O2/O2 with the pyrite surface was also investigated by the density states analysis. These results provide some insights into the oxidizing effect of H2O2 in pyrite flotation.

The depression mechanism on pyrite in a low-alkaline system with combined depressants : Experiment, HSC, DFT and ToF-SIMS studies

86%

Li S. , Yuan J. , Ding Z. , Li J. , Yu A. , Wen S. , Bai S.

tom Vol. 59, iss. 3

art. no. 168454

Depression of pyrite in a low-alkaline system has sparked soaring interests for the multi-metal sulfide minerals flotation recently. This study investigates effects of combined depressants (Ca(ClO)2 and CaO) on pyrite flotation with butyl xanthate (KBX). Micro-flotation experiments indicate that the addition of 200 mg/L combined depressants (a mass ratios of CaO to Ca(ClO) 2 of 2:3) and 1.0×10−3 mol/L KBX at pH 9.5 can effectively depresses the flotation of pyrite, and a minimum pyrite recovery rate of 12.5% is obtained. Basic thermodynamic evaluation results confirm the participation of Ca(ClO) 2 significantly decrease the negative Gibbs free energies of pyrite oxidation reaction. Besides, the calcium species (Ca(OH) 2, Ca2+ and Ca(Cl) 2) will spontaneously transform into CaCO3,and it is the ultimate dominant calcium species in the CO32- system. Density functional theory (DFT) results indicate that CaCO3 can chemically adsorb onto the pyrite surface with an adsorption energy of -671.13 kJ/mol. The O1 and Ca atoms mainly contribute to the bonding process and are responsible for the stable adsorption of CaCO3. ToF-SIMS results provide strong evidence that the combined depressants increase the amount of hydrophilic species and decrease dixanthogen adsorption onto the pyrite surface. The thickness of the whole formed hydrophilic species is approximately 50 nm. Semiquantitative amounts of hydrophilic species follow the order of hydroxy calcium>iron carbonyl>calcium carbonate. Overall, hydrophilic species repulse adsorption of dixanthogen and significantly reduce the flotation performance of pyrite.