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1

Separation and purification of light rare earth elements from chloride media using P204 and Cyanex272 in sulfonated kerosene under non-saponification conditions

Fan Peiqiang, Zhang Wenjie, Tong Xiong, Xie Xian, Xie Ruiqi, Song Qiang, Du Yunpeng, Cao Yang

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 6

art. no. 172444

EN

The extraction of light rare earths (Pr and Nd) from chloride medium was investigated using a mixture of di(2-ethylhexyl) phosphoric acid (P204) and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272) in sulfonated kerosene. The P204+Cyanex272 system exerted a synergistic effect on the separation of light rare earths, and the separation coefficient was higher than when P204 and Cyanex272 were used as extractants alone. The separation coefficient of Pr and Nd in the extraction system reached 1.75 when the pH of the aqueous phase material solution was approximately 2.5, and 1.5 mol/L hydrochloric acid as a stripping agent effectively eluted the rare earth ions in the loaded organic phase. Combining the slope method, infrared spectroscopy, and nuclear magnetic resonance spectroscopy, we explored the mechanism of the extracted Nd and Pr into the organic phase complex, and finally entered the organic phase with Re(HA2)2B. The P-O-H bond and P=O bond in the extractant P204 and Cyanex272 formed a coordination bond with Re3+. Therefore, this extraction method also provides a reference for a more environmentally friendly and efficient procedure for separation and purification of light rare earth elements Pr and Nd.

2

Activation of quartz flotation by Cu2+, Ni2+ in the sodium ethylxanthogenate (EX) system

Liu Yang, Tong Xiong, Xie Rui-Qi, Xie Xian, Song Qiang, Fan Pei-Qiang

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 2

art. no. 166368

EN

During the flotation of metal sulfide minerals, due to the interference of unavoidable ions, the quartz also partially floats in some cases. The studies on the mechanism of quartz being activated and floating up are still insufficient. In this study, the influence of the Cu2+ and Ni2+ unavoidable ions on the floatation of quartz was studied by micro-flotation experiments, adsorption detection, zeta potential measurement, solution composition calculation, infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses, and atomic force microscopy (AFM) observation. This provides a theoretical reference for further understanding the mechanism of sodium ethylxanthogenate and quartz surface, as well as the development of a new quartz depressant. The results of flotation showed that after activation by Cu2+ (1×10-4 mol/dm3) and Ni2+ (5×10-5 mol/dm3), the quartz was captured by sodium ethylxanthogenate (EX: 1.4×10-4 mol/dm3) under alkaline conditions (pH=10), while the best recoveries were obtained as 80% and 43%, respectively. The results of adsorption and zeta potential measurements showed that the precipitation rate of Cu2+ was greater than that of Ni2+ under alkaline conditions. Additionally, both Cu2+ and Ni2+ electrostatically adsorbed on the quartz surface and changed the zeta potential of quartz. The solution composition calculation further showed that Cu(OH)+, Cu(OH)2(s), and Ni(OH)+, Ni(OH)2(s) were the main components in the solution under alkaline conditions. The FT-IR and XPS analyses and AFM observations demonstrated that Cu and Ni species adsorbed on O atoms on the quartz surface, providing active sites for EX adsorption, and EX combines with Cu and Ni species on the quartz surface to generate -O-Cu-EX and -O-Ni-EX complexes. Finally, the quartz floated up due to the formation of hydrophobic products and firm adsorption.

3

Effective separation of specularite and aegirite using chitosan as a novel depressant

Li Mingyang, Zhang Pengpeng, Gao Xiangpeng, Tong Xiong, Xie Xian

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 6

art. no. 151692

EN

As a typical iron-bearing silicate gangue, aegirite often associates with specularite. Due to the iron element contained in aegirite, it has similar surface properties to specularite. Flotation is by far one of the most efficient methods of processing this kind of iron ore. But the traditional depressants unable to take action in the separation of specularite and aegirite. Chitosan was used as a novel depressant to attempt to separate specularite from aegirite through microflotation tests, adsorption tests, contact angle measurements, Zeta potential measurements, and XPS analysis. The flotation results indicate that chitosan show more strong depression effect on specularite than aegirite. Zeta potential measurements, contact angle measurements and adsorption tests demonstrate that chitosan is more inclined to adsorb on the specularite surface than aegirite, which hinders the subsequent adsorption of collector sodium oleate and increases difference in hydrophobicity between the two minerals. The XPS results of specularite validate the adsorption of chitosan on specularite, and illustrate that electrons of chitosan were partially transferred to oxygen and iron atoms in specularite during the adsorption process.

4

Comparison of the depression effect of two thiol depressants on the separation of specularite and aegirite

Li Mingyang, Zhang Chen, Gao Xiangpeng, Xie Xian, Tong Xiong

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 6

art. no. 152164

EN

In this work, two thiol-type reagents, thioglycolic acid (TGA) and mercaptopropionic acid (MPA), were firstly exploited and compared as aegirite depressants with sodium oleate (NaOl) as the collector to separate specularite from aegirite by flotation. The adsorption performances and mechanisms of TGA and MPA on aegirite surface were investigated via flotation experiments, Zeta potential tests, adsorption measurements, contact angle dimensions, and surface characterizations. The results of flotation indicated that TGA and MPA exhibited a considerable depression impact on the flotation of aegirite but little effect on specularite. TGA depicted more excellent depression performance than MPA, which was confirmed by HLB calculation. The results demonstrated that TGA and MPA favorably adsorbed on aegirite surface instead of specularite, hindering the subsequent adsorption of NaOl on specularite and resulting in the surface being hydrophilic. XPS results revealed that TGA and MPA were significantly adsorbed on the surface of aegirite through an interaction between the carboxyl and thiol groups of the depressants and the Si and Fe on the surface of aegirite.

5

Insight into the effect of galvanic interactions between sulfide minerals on the floatability and surface characteristics of pyrite

Yang Bo, Tong Xiong, Xie Xian, Huang Lingyun

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 2

24--33

EN

Complex sulfide ores are usually found as a mixture of various sulfide and gangue minerals, and froth flotation is the predominant method for the selective separation of sulfide minerals. Adherence and contact between sulfide minerals are inevitable during froth flotation, and galvanic interactions between sulfide minerals will occur because of differences in rest potentials. However, the effect of these galvanic interactions on the selective flotation of sulfide minerals have been rarely studied. In this work, the effect of the galvanic interaction between pyrite and sphalerite on the flotation behavior and surface characteristics of pyrite was investigated by micro-flotation tests, collector adsorption tests, electrochemical techniques and XPS (X-ray photoelectron spectroscopy) surface analysis. The micro-flotation tests indicated that the floatability of pyrite decreased in the pH range of 4.0 to 9.5 and increased under strongly alkaline pH conditions (pH > 10) due to the galvanic interaction. The collector adsorption results demonstrated that the adsorption capacity of the collector on the pyrite surface was significantly reduced because of the galvanic interaction between pyrite and sphalerite. The electrochemical measurements revealed that the decrease in the oxidation current of xanthates to dixanthogen was responsible for the decreasing adsorption capacity of the collector on the pyrite surface. The XPS results indicated that the formation of the S"O$ "% oxidation product on the pyrite surface decreased at a strongly alkaline pH due to the galvanic interaction. Therefore, pyrite floatability improved at an alkaline pH. These results consistently showed that the galvanic interaction between pyrite and sphalerite had an important influence on the floatability and surface characteristics of pyrite.

6

Effect of particle size on the oxidation and flotation behavior of galena particles

Lu Yalin, Tong Xiong, Xie Xian, Yang Bo, Hua Zhongbao

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 1

208--216

EN

The aim of this study was to determine the effect of particle size on the oxidation and flotation behavior of galena particles. Coarse (-0.074+0.038 mm), intermediate (-0.038+0.025 mm) and fine (-0.025 mm) galena particles were used in this study. Dissolution tests demonstrated that the amount of oxidation products increased with the decrease of particle sizes. The surface oxidization of galena was the greatest at pH 7.3, followed by pH 12 and 9, which were consist with the result of XPS. The micro-flotation results indicated that the effect of pH on the flotation recovery of galena enhanced with the reduction of particle sizes. The decreasing of particle sizes increases both the sorption rate of collector and the dissolution of galena, while the generation of hydrophilic product caused by dissolution is dominant, rendering the mineral hydrophilic. This study shows the differences in the surface oxidation and flotation behavior of different size fractions of galena particles. To promote the flotation recovery of the fine size fraction of galena particles, alleviating their oxidation is the key.

7

Density functional theory study of H2O adsorption on different sphalerite surfaces

Deng Zheng-bin, Tong Xiong, Huang Ling-yun, Xie Xian

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 1

82--88

EN

Effects of In, Ge, Fe substitution in the lattice of sphalerite on wettability were usually ignored, therefore the optimal flotation condition could be difficult to find due to lacking of sufficient theoretical study on water adsorption, resulting lower recoveries of different sphalerites. Adsorption of H2O on different sphalerite surfaces was studied using density functional theory (DFT) method. All computational models were built in a vacuum environment to eliminate the effects of oxygen and other factors. H2O molecule prefers to stay with ideal sphalerite, indium-beard sphalerite, germanium-beard sphalerite and marmatite surfaces rather than water. Compared with ideal sphalerite surface, Fe atom improves the hydrophilicity of surface, while In and Ge atoms reduce the hydrophilicity.

8

Ammonium chloride’s weakening effect on the copper activation of pyrite in flotation and the surface regulation mechanism behind it

Zhang Shengdong, Chen Yumeng, Tong Xiong, Xie Xian, Lu Yalin

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 5

1070--1081

EN

The traditional separation process of pyrite and marmatite is carried out under highly alkaline conditions. Therefore, a large amount of lime is demanded and the zinc recovery cannot be guaranteed. However, under weakly alkaline conditions, copper-activated pyrite has good floatability, which is difficult to separate from marmatite. In this paper, ammonium chloride (NH4Cl) is used for depressing the flotation of copper-activated pyrite to achieve the separation of these two minerals under weakly alkaline environment. The flotation tests show that NH4Cl can significantly reduce the floatability of pyrite in weakly alkaline conditions. The results of adsorption tests and X-ray photoelectron spectroscopy (XPS) analyses indicate that NH4Cl can obviously change the composition of pyrite surface by increasing the content of iron/copper hydroxide and reducing the content of copper sulfides. Calculation of the solution composition demonstrates that the addition of NH4Cl results in the occurrence of Cu(NH3)n2+ and the pH buffering property. Based on these results, it can be concluded that the depression of NH4Cl on copper activated pyrite is mainly derived from two aspects: 1) the pH buffering property of the conjugated acid-base pair (NH4+/NH3) can impede the decline of OH- concentration, which results in more hydroxide adsorbed on pyrite; 2) NH3 (aq) competes with the pyrite surface to consume Cu2+through complexation, which causes a reduction in the amount of copper sulfides formed on the pyrite surface.