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

Cao Qinbo, Yan Wenchao, Wen Shuming, Liu Dianwen, Li Yanjun

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 1

art. no. 157409

EN

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.

2

Interaction of sulfuric acid with dolomite (104) surface and its impact on the adsorption of oleate anion: a DFT study

Cao Qinbo, Zou Heng, Chen Xiumin, Yu Xingcai

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 1

34--42

EN

Sulfuric acid (H2SO4) is a specific depressor for apatite rather than for dolomite. The H2SO4treated dolomite can still be floated effectively by oleate. However, the role of H2SO4 in the adsorption of oleate onto dolomite surface remains unclear. In this work, density functional theory calculations were conducted to probe the interactions among sulfate anion (SO42−), oleate anion and the dolomite surface. The adsorption behaviors of SO42− anion onto the perfect and CO3-defect dolomite surfaces were compared. Such results show that SO42−anion could only adsorb onto the defective dolomite surface, where it bonded with a Ca atom. The remaining Ca and Mg atoms at the defect site could further react with the oleate anion, generating new Ca/Mg–O ionic bond. In this regard, oleate and SO42−anions may both present on the dolomite surface. This phenomenon accounts for the flotation of H2SO4-treated dolomite.

3

Insights into the interaction between octyl hydroxamic acid and the rutile surface activated by lead ion

Cao Qinbo, Chen Xiumin, Zou Heng, Yu Xingcai

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 5

928--938

EN

The flotation of rutile can be enhanced using lead ion as an activator. However, the binding behavior of collector on the activated rutile surface is still not fully understood. In this work, flotation and theoretical calculation approaches were employed to evaluate the activation behavior of lead ion in the flotation of rutile with octyl hydroxamic acid (OHA). Flotation results indicated that the activation flotation with lead ion should be conducted at pH 6.5. The binding features of OHA molecule on the inactivated and Pb-activated rutile surfaces were both investigated by density functional theory (DFT) studies. The OHA molecule may dissociate into OHA− anion on the inactivated rutile surface, generating a new Ti–O bond. Differently, the chelate complex of Pb-OHA anion was generated on the activated rutile surface, producing two Pb–O bonds. The adsorption of OHA onto the activated rutile surface was more stable than that on the inactivated rutile surface, due to the formation of more chemical bonds on the activated rutile surface. The DFT calculation results delineated the role of Pb2+ in the rutile flotation with OHA.

4

Binding features of N-hexadecanoylglycine on two terminations of fluorapatite (001) surface and their effect on fluorapatite flotation

Zou Heng, Liu Dianwen, Cao Qinbo, Chen Xiumin

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 5

949--959

EN

N-hexadecanoylglycine (C16Gly) is a newly synthesized collector, which can be used as an efficient collector for fluorapatite (FA) rather than for dolomite. To extend our knowledge regarding the C16Gly collector, the contact angle method was employed to understand the flotation selectivity of C16Gly in the FA and dolomite system. On the other hand, the possible binding models of C16Gly anion on Ca-rich and PO4-rich terminations of FA (001) surface were investigated with density functional theory calculations to reveal the interaction between the C16Gly and the FA surface. Results showed that C16Gly anion could interact with these two terminations to generate 12 low-energy configurations, including bidentate, tridentate and chelating binding models. The C16Gly anion preferred to adsorb onto the Ca-rich termination, which is caused by the weaker electrostatic repulsion force between the C16Gly anion and the PO4 groups on this termination. The adsorption of C16Gly on these terminations was more stable than that on the dolomite (104) surface, which is one of the reasons for the preferential flotation of FA from dolomite using C16Gly as a collector. These findings provide further insights into the selectivity of C16Gly during the flotation of FA and dolomite.

5

Adsorption of lead ion on the hydrated rutile (110) surface: a DFT calculation study

Zou Heng, Cao Qinbo, Chen Xiumin, Liu Dianwen

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 4

951--959

EN

The adsorption behavior of lead species on the hydrated rutile surface was investigated with inductively coupled plasma mass spectrometry (ICP-MS) measurements and density functional theory (DFT) calculations. ICP-MS experiments suggested that lead species can be readily absorbed by the rutile powder in water at pH 6.5. From the ICP-MS results and the species distribution of Pb2+, it was concluded that Pb2+ was the major lead species adsorbing at the rutile/water interface at the pH of 6.5. DFT calculation results indicated that Pb2+ could adsorb at four different sites on the surface. At each site, water molecules or OH groups were involved in the reaction with Pb2+. The water molecules/OH groups on the rutile surface play an important role during the adsorption of Pb2+ on the hydrated rutile surface.