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Lead species formation on pure hemimorphite surface and its performance for subsequent sulfidization

Liang Guanyu, Zhang Song, Xian Yongjun, Chen Luzheng

Physicochemical Problems of Mineral Processing

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2024

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Vol. 60, iss. 2

art. no. 187064

EN

Hemimorphite is important-supplementary resource for the commercial zinc production, but it easy loses into tailings due to extreme difficulty for its surface sulfidization. Adding active metal ions after sulfidization have been widely proposed for enhancing hemimorphite floatability, but its desired efficiency in flotation practice has not yet been completely achieved caused by the instability of sulfide layer. Whereas pre-adsorption of active metal ions to modify the hemimorphite surface has strong potential to make up for this shortcoming. Herein, the feasibility and appropriate environment of free Pb2+ for modifying the pure hemimorphite surface was evaluated. Subsequently, the performance of Pb2+ adsorption for enhancing sulfidization stability and floatability of hemimorphite were investigated. The X-ray photoelectron spectroscopy results indicated that the Pb2+ adsorption on hemimorphite surface was achieved through the Pb ions displacement for Zn ions, and it was bond to oxygen-containing groups on hemimorphite surface. Such adsorption was strengthened with the increasing of solution pH, owing to the abundant Pb hydroxyl species precipitated on mineral under alkaline conditions, in term of the results of visual MINTEQ modeling and time-of-flight secondary-ion mass spectrometry. In addition, the X-ray photoelectron spectroscopy results showed dominant Pb hydroxyl species further reacted with sulfur during subsequent sulfidization to generate much more S species than that of without Pb2+ pre-modification. Meanwhile, such sulfide layer composed by Pb2+ on the mineral surface presented much higher stability than Zn-S species, which was verified via adsorption and desorption tests. As a result, the sulfidization and flotation recovery of hemimorphite increased after Pb2+ pre-adsorption.

2

Influence of hydrated Ca2+ and Mg2+ complexes on the sulfidization of smithsonite : density functional based tight binding (DFTB+) study

Wu Zhiqiang, Tang Xiaoqin, Chen Jianhua, Chen Ye

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 6

art. no. 156040

EN

Ca2+ and Mg2+ are the most dominating unavoidable ions in the smithsonite flotation. In this paper, the effect of Ca2+ (Mg2+) on the surface of smithsonite sulfidization in a system where water molecules are present was investigated using density functional based tight binding (DFTB+) simulations for the first time. The results indicated that the adsorption of hydrated Ca2+ complexes is stronger than that of hydrated Mg2+ complexes on the hydrated smithsonite (101) surface. In addition, at low concentrations of sodium sulfide, there is no adsorption of HS- on the surface pre-adsorbed with hydrated Ca2+ complexes, but only on the surface pre-adsorbed with hydrated Mg2+ complexes. At high concentrations of Na2S, S2- weakens the adsorption of hydrated Ca2+ complexes due to competitive adsorption, but the presence of S2- could desorb hydrated Mg2+ complexes from the surface. The results compared the differences in effects of Ca2+ and Mg2+ on smithsonite sulfidization, which could provide an atomic scale basis for researching the surface sulfidization of oxide minerals.

3

New insights into the promotion mechanism of (NH4)2SO4 in sulfidization flotation: a combined experimental and computational study

Chen Daixiong, Liu Mengfei, Hu Bo, Dong Yanhong, Xue Wei, He Peng, Chen Fang, Zhu Jianyu, Zhang Chenyang

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 5

57--70

EN

Ammonium sulfate ((NH4)2SO4) exhibits promoting effects in malachite sulfidization flotation. However, the promotion mechanism remains poorly understood. In this study, micro-flotation tests, zeta-potential measurements, scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and materials studio simulation (DFT) were used to investigated the promotion mechanism of (NH4)2SO4. Micro-flotation test demonstrates that the recovery of malachite from 73% increased to 83%, when the (NH4)2SO4 was added. Contact angle and zeta potential test results indicate that addition of Na2S•9H2O changes the surface properties of malachite and provide the conditions for adsorption of butyl xanthate (BX). After promoting the sulfidization by (NH4)2SO4, BX is more effective in improving the hydrophobicity. SEM-EDS and AFM results show that (NH4)2SO4 can improve performance and stability of sulfidization. X-ray photoelectron spectroscopy indicates that after sulfidization, polysulfides and cuprous were appeared in malachite surface, infers that a redox reaction occurs between sulfur and copper on the surface of malachite. After addition of (NH4)2SO4, the percentage of polysulfides and cuprous were increased, it implies (NH4)2SO4 can accelerate the redox reaction. Computational results show that after adding (NH4)2SO4, the adsorption energy of HS- on the malachite surface is reduced, implies that (NH4)2SO4 can improve the stability of HS-adsorption on the surface of malachite.

4

Effect of sulfidization on the stability of adsorption of isoamyl xanthate on malachite

Xiong Kun, Wen Shuming, Liu Zilong, Deng Jiushuai, Mao Yingbo

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 3

493--503

EN

The activity and stability of adsorbed isoamyl xanthate (IX) on a malachite surface before and after sulfidization were studied by calculating the malachite dissolved component and adsorption energy and performing experiments pertaining to the zeta potential, adsorption and desorption experiments, and flotation experiments. In the malachite slurry solution, the main components of copper are Cu2+, CuCO3, HCuO2-, CuO2-, and Cu(CO3)22-, and the concentration distribution of these components is related to the slurry pH value. Between pH 5 to 9, the main copper component in the slurry is CuCO3. The malachite surface is negatively charged; however, the sulfur ions or hydrosulfide ions can still adsorb on the surface at a pH of more than 8.2, which indicates that the sulfidization of malachite corresponds to the chemical adsorption, and the surface electrical properties of the malachite are not obvious to the sulfidization. The adsorption activity of malachite on IX is stronger than that of the sulfide malachite; however, the desorption ratio of IX with respect to the malachite is higher than that pertaining to the sulfide malachite. The adsorption energy of IX on the malachite and sulfide malachite surface was -449.6 kJ/mol and -1134.7 kJ/mol, respectively, and the IX adsorbed on the sulfide malachite surface was more stable. The flotation experiments indicated that the sulfidization of malachite reduced the consumption of IX; however, the recovery of malachite was improved.

5

Effect of pH on surface characteristics and flotation of sulfidized cerussite

Feng Q., Wen S., Zhao W., Liu J., Liu D.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 2

676--689

EN

The effect of pH on surface characteristic and flotation of sulfidized cerussite was studied by micro-flotation tests, dissolution experiments, scanning electron microscopy (SEM) energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). The micro-flotation tests demonstrated that higher recovery of cerussite was achieved in acidic solutions than that in alkaline solutions. Despite the addition of high collector concentrations, cerussite flotation did not improved in alkaline solutions. The dissolution performance of sulfide-treated cerussite at different pH values indicated that the lead sulfide layer on the surface of sulfide-treated cerussite could exist in acidic solutions and it was more stable at acidic pH than in alkaline solutions. This finding was proved by the SEM-EDS and XPS analyses.