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1

Leaching behaviour of zinc from a smithsonite ore in sodium hydroxide solutions

Ehsani Ilhan, Ucyildiz Ayse, Obut Abdullah

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 2

407--416

EN

In this study, the leaching behaviour of zinc from a smithsonite ore sample (23.43% Zn) having goethite and calcite as main gangue minerals was investigated in sodium hydroxide solutions using Xray diffraction and chemical analyses. Within the studied NaOH concentration range (1-4 mole/dm3), higher leaching ratio values for Zn were obtained by leaching at 298 K because of the decreased stability of soluble zincate species in solution at higher temperatures. When the concentration of NaOH solution was increased from 1 to 3 mole/dm3 at 298 K, leaching ratio value of Zn increased from 3.8 to 70.1%. At 4 mole/dm3 NaOH concentration, Zn leaching ratio value (70.9%) levelled off due to the formation of solid hydrated calcium zincate phase in leaching solution. On the other hand, very low leaching ratio values of Zn were obtained by leaching in 1 mole/dm3 NaOH solution at 298 K (3.8%) and 363 K (1.4%) due to the formation of solid zinc hydroxide and solid zinc oxide phases, respectively. It was observed that increasing leaching time from 1800 to 14400 s at 3 mole/dm3 NaOH concentration, favoured the formation of hydrated calcium zincate phase and so decreased the leaching ratio of Zn to a lower value (60.6%). The effect of solid/liquid ratio was also investigated and it was found that when solid/liquid ratio was decreased, Zn leaching ratio values decreased at constant OH/Zn mole ratio and increased at constant NaOH concentration conditions. Besides, for some of the experiments, leaching ratio values of lead were also given.

2

Basic theory and optimization of gold containing antimony concentrate leaching by alkaline sulfide

Wu Hao, Feng Yali, Li Haoran, Liao Shengde, Wang Hongjun

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 1

248--257

EN

As sodium sulfide is easily oxidized to polysulfide and thiosulfate which have a gold leaching effect, gold would dissolve in leaching solution when extracting stibium from gold containing antimony concentrate by alkaline sulfide. Through leaching test and kinetics analysis, the decomposition regularity of sodium sulfide and leaching rate were studied under different leaching conditions. The results indicated that the gold content in antimony concentrate was 28.41g/Mg, and the content of antimony and sulfur was 36.01% and 14.04%, respectively. The main metallic minerals were native gold, arsenopyrite, stibnite, and the gangue minerals were mainly quartz. Anodic polarization curve shows reduced iron powder can increase the peak potential of the oxidation of the leaching solution and it can effectively prevent the decomposition of sodium sulfide and the dissolution of gold. Optimized stibium-extraction efficiency was achieved under the following conditions: a concentration of sodium sulfide and sodium hydroxide at 110g/dm³ and 20g/dm³, respectively; a ratio of iron powder to concentrate of 1:30; a ratio of liquid to solid of 5:1; agitation speed of 600rad/min; reaction temperature of 353.15K; and a reaction time of 3 h. Under the optimized conditions, high antimony recovery (97.35%) and low gold dissolution (1.32%) were achieved.

3

A novel method to extract vanadium from high-grade vanadium slag: non-salt roasting and alkaline leaching

Liu B., Meng L., Zheng S., Li M., Wang S.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 3

657--667

EN

A new method using non-salt roasting-alkaline leaching to treat vanadium slag was proposed in this study. The V(III) in vanadium slag is oxidized to V(V) by roasting and the latter can be effectively leached out as vanadate by alkaline leaching. This method possesses distinct advantage of being able to treat high-grade vanadium slag. For the South Africa high-grade vanadium slag, the maximum vanadium recovery of 98% was achieved when the reaction conditions were roasting temperature of 850 °C, roasting time of 2 h, alkali concentration of 30 wt.%, leaching temperature of 210 °C, and leaching time of 2 h. The roasting and leaching mechanisms have been well elucidated based on the XRD and SEM analysis results. The phases transitions of vanadium slag were clearly presented. This work has laid the foundation for the industrial application of non-salt roasting-alkaline leaching and provided new insights into effective extraction of high-grade vanadium slag.

4

Leaching of High Arsenic Content Dust and a New Process for the Preparation of Copper Arsenate

Sheng W., Shen Y.-Y., Sheng-Quan Z.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1167--1172

EN

In this research, the high arsenic content dust of copper smelting, as a raw material, the extraction of copper and arsenic from the high arsenic content dust in the leaching system containing acidic and alkaline compounds was investigated. Meanwhile, the effects of acid/alkaline initial concentration, liquid to solid ratio, leaching temperature, leaching time on the leaching rate of copper and arsenic were studied. The optimum conditions for the leaching of high arsenic content dust and preparation of copper arsenate were determined. The results showed that acidic/alkaline leaching of high arsenic content dust was particularly effective. 93.2% of the copper, and 91.6% of the arsenic were leached in an acidic leaching process and 95% of the arsenic, while less than 3% of the copper, less than 5% of the antimony, less than 2% of the bismuth was also leached in an alkaline leaching process. A new method (the parallel flow drop precipitate method) was developed in the synthesis of copper arsenate process. The parallel flow drop method was employed to adjust the molar ratio (copper to arsenic) of the mixed solution of the acid-leaching solution and the alkali-leaching solution by taking the drop acceleration of an acidic leaching solution and an alkaline leaching solution at 10 mL/min and 12 mL/min, at a temperature of 60°C and a reaction time of 1h. Copper arsenate was prepared by mixing an acidic leaching solution and an alkaline leaching solution. The main phases of copper arsenate were CuHAsO4·1.5H2O and Cu5As4O15·9H2O. Copper arsenate contained 30.13% copper and 31.10% arsenic.

5

Alkaline Leaching of Low Zinc Content Iron-Bearing Sludges

Gargul K., Jarosz P., Małecki S.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 1

43--50

EN

Various types of waste materials containing zinc (e.g. dusts and sludges from gas dedusting process) are obtained in steel industry. The contents of Zn in these materials may vary considerably. Even a low concentration of zinc in recirculated products precludes their recycling in ferrous metallurgy aggregates. Long storage of this type of material can lead to contamination of soil and water by zinc compounds which can be leached out by acid rain, for example. This paper focuses on research involving alkaline leaching tests of low zinc content iron-bearing materials. These tests were preceded by the analysis of the elemental, phase and grain size composition, and analysis of the thermodynamic conditions of the leaching process. The main aim of research was to decrease the content of the zinc in the sludge to the level where it is suitable as an iron-bearing material for iron production (~1% Zn). Leaching at elevated temperatures (368 K, 60 min) has led to a decrease in the zinc content in the sludge of about 66%. The research revealed that long hour leaching (298 K, 100 hours) carried out at ambient temperatures caused a reduction in zinc content by 60% to the value of 1.15-1.2% Zn.

6

Production of zinc powder from Co-Zn plant residue using selective alkaline leaching followed by electrowinning

Kamran Haghighi H., Moradkhani D., Sardari M. H., Sedaghat B.

Physicochemical Problems of Mineral Processing

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2015

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Vol. 51, iss. 2

411--425

EN

Annually, gigagrams of cobalt residues, called hot filter cake (HFC), are produced from the Co neutralization step at Iranian zinc plants. With respect to the composition of HFC )i.e., 15-25% Zn, 0.5–1.5% Co, 3–8% Mn(, it can be used as a secondary source of zinc, cobalt and manganese. In the present study, for the first time, treatment of HFC for separation and recovery of zinc has been studied. The residue was treated by employing selective alkaline leaching, in order to recover the maximum amount of zinc, followed by zinc electrowinning process. As a results, a solution was obtained from alkaline leaching under the optimum condition of 75 °C, sodium hydroxide of 8 M, solid-to-liquid ratio dm3 of 1:10, and stirring speed of 600 rpm, having zinc recovery of 88.5 %. In the following step, the electrowinning process, under the optimum working conditions being current density 350 A/m2 and time 10 hours, was carried out to produce a zinc powder with high purity of 99 percent. Finally, a simple and effective conceptual flow diagram was proposed for the process.

7

Characterization of the solid residue of enargite Cu3AsS4 after alkaline leaching.

Achimovicova M., Balaz P., Bastl Z., Sanchez M.

Fizykochemiczne Problemy Mineralurgii

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1999

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Vol. 33

7-14

EN

The characterization of solid after alkaline leaching of enargite Cu3AsS4 is discussed. X-ray diffractometry for characterization of the physico-chemical transformations in bulk of source enargite concentrate resulted from alkaline leaching was used. The surface layers of the samples of enargite concentrate were investigated with XPS spectroscopy. The leaching of mechanically activated enargite concentrate with Na2S leads to total extraction of arsenic (the content of As in a solid after leaching is 0.06%) and then decomposition of enargite (Cu3AsS4) with formation of new phases of copper sulphide and jarosite. XPS spectroscopy measurements did not registered the occurrence of arsenic in any chemical form in the sample of solid taken from leaching system.

PL

Przedyskutowano charakterystyczne cechy suchej pozostałości po alkalicznym ługowaniu enagritu Cu3AsS4. W celu charakteryzacji fizykochemicznych przemian w suchej pozostałości posłużono się dyfraktogramem rentgenowskim koncentratu enagritu otrzymanego z ługowania. Warstwy powierzchniowe próbek koncentratu enagritu badano przy pomocy spektroskopii XPS. Ługowanie mechanicznie aktywowanego enagritu z Na2S prowadzi do całkowitej ekstrakcji arsenu (zawartość As w suchej pozostałości po ługowaniu wynosi 0,06%), a następnie do dekompozycji enargitu Cu3AsS4 z utworzeniem nowych faz siarczku miedzi i jarosytu. Pomiary wykonane techniką spektroskopii XPS nie wykazały obecności arsenu w żadnej postaci w próbce otrzymanej po ługowaniu.