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Himalayan rock salt contains a variety of minerals and trace elements, which is conducive to human health. The solutions of black rock salt and rose salt are alkaline, and the content of water insoluble matter is 0.34 and 0.083%, respectively. The element composition of water insoluble matter in rock salt is determined and analyzed. It is found that the main component of two kinds of rock salt water insoluble matter is soil. Due to the presence of water insoluble matter in rock salt, according to the different specific gravity of molten sodium chloride and insoluble matter, rock salt was purified by high-temperature melting method. Rose salt is mainly studied during purification. The results showed that the content of insoluble matter in rose salt decreased from 0.083 to 0.0024% after holding at 950°C for 40 min; the contents of arsenic, barium, and lead decreased to 0.0032, 0.61, and 0.21 mg·kg−1, respectively; the content of sodium increased to 39.24%, the contents of calcium, magnesium, and iron reached to 2,200, 855, and 1.31 mg·kg−1, respectively.

Zinc oxide dust contains various valuable metals of high recovery value; however, the recovery rate of germanium (Ge) from zinc oxide dust remains low in industrial production. To address this challenge, this study investigated the leaching behaviour and occurrence state in the residue of Ge. Mineralogical analysis of Ge-containing zinc oxide dust, combined with sulphuric acid leaching tests, revealed negative correlation between iron (Fe) and silicon (Si) content in the dust and the leaching rate of Ge. Given this finding, the leaching behaviour of Ge and its occurrence state in the leach residue, was further studied using mixed zinc oxide dust (Mixed Dust). This study demonstrated challenges in completely decomposing Ge-containing insoluble phases in the sulphuric acid system, and Ge primarily existed in silicate and insoluble solids (mainly zinc ferrite) with the leach residue, accounting for 69.74% and 18.42% of its distribution, respectively. The insoluble phases of Fe and Si in the leach residue were decomposed through a three-stage enhanced leaching process. The results indicated that the leaching rate of Ge was significantly increased to 95.98% by dissolving insoluble solids such as zinc ferrite and disrupting the lattice of silicate minerals. La poussière d'oxyde de zinc contient divers métaux de valeur ayant une valeur de récupération élevée. Cependant, le taux de récupération du germanium à partir de la poussière d'oxyde de zinc reste faible dans la production industrielle. Pour relever ce défi, cette étude a examiné les raisons du faible taux de lixiviation du germanium (Ge), en se concentrant sur son comportement de lixiviation et son état d'occurrence dans le résidu. L'analyse minéralogique de la poussière d'oxyde de zinc contenant du Ge, combinée à des essais de lixiviation à l'acide sulfurique, a révélé une corrélation négative entre la teneur en fer (Fe) et en silicium (Si) de la poussière et le taux de lixiviation du Ge. Étant donné ces résultats, on a étudié davantage le comportement de lixiviation de Fe, Si et Ge dans un système d'acide sulfurique, ainsi que l'état d'occurrence du Ge dans le résidu de lixiviation, en utilisant de la poussière d'oxyde de zinc mélangée (Poussière Mixte). L'étude a démontré les défis liés à la décomposition complète des phases insolubles contenant du Ge dans le système d'acide sulfurique. L'adsorption de Ge sur le Si a conduit à la précipitation de Ge dans le résidu. Par conséquent, le Ge existait premièrement dans les silicates et les solides insolubles (principalement la ferrite de zinc) dans le résidu de lixiviation, tenant compte de 69.74% et 18.42% de sa distribution, respectivement. Les phases insolubles de Fe et Si dans le résidu de lixiviation ont été décomposées par un procédé de lixiviation améliorée en trois étapes. Les résultats ont indiqué que le taux de lixiviation du Ge avait considérablement augmenté jusqu'à 95.98% en dissolvant des solides insolubles tels que la ferrite de zinc et en perturbant le réseau des minéraux silicatés. [ABSTRACT FROM AUTHOR]

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This paper presents the use of an oxygen pressure-based acid leaching process for the selective extraction of basic metals from a complex zinc ore containing high concentrations of lead (6.00%) and copper (2.47%). The effects of leaching temperature, ore particle size distribution, leaching time, liquid-to-solid ratio, and oxygen partial pressure on the leaching efficiencies of zinc and copper were investigated, and the phase transformation behaviour of lead compounds was studied. Under the optimal conditions that is, a particle size of −48/+40 μm, initial sulfuric acid concentration of 150 g/L, liquid-to-solid ratio of 6:1, leaching time of 150 min, leaching temperature of 150°C, and oxygen partial pressure of 0.8 MPa – the leaching efficiencies of zinc, copper, and iron were 98.85%, 82.69%, and 33%, respectively. The leaching residue showed that almost all of the zinc sulfide was dissolved as ZnSO4, and most of the negatively charged bivalent sulfur was converted to zero-valent element sulfur. Through the pressure leaching reaction, galena in the concentrate was converted to lead jarosite (PbFe6(SO4)4(OH)12) and elemental sulfur. The formation of lead jarosite facilitated the removal of a significant portion of iron during leaching, reducing the subsequent purification burden. [ABSTRACT FROM AUTHOR]

This study employed low-grade hematite acquired from zinc hydrometallurgy to synthesize α-Fe2O3 pigment via high-temperature hydrothermal treatment. This study investigated the effects of hydrothermal conditions on α-Fe2O3 pigment. The results indicate that hydrothermal treatment causes the internal rearrangement of Fe (oxyhydr)oxides into Fe oxides. A high-quality α-Fe2O3 pigment with a Fe content > 69% and Zn and S content < 0.15% and 0.25% was successfully synthesized using the HCl-H2O medium at > 260°C. The average crystal size of α-Fe2O3 pigment was found to be between 45 nm and 80 nm. The α-Fe2O3 pigment consists of prismatic crystals with a smooth surface and distinct edges. The UV-VIS-NIR spectra demonstrated that the α-Fe2O3 pigment strongly absorbs light in the wavelength range of 200–420 nm, and its absorption edge falls between 420 nm and 550 nm. Additionally, the α-Fe2O3 pigment has chromatic values of L* = 37.27–38.69, a* = 5.07–6.26, and b* = 1.70–2.49. All α-Fe2O3 products show similar colors. This work introduces an environmentally friendly method for synthesis of high-quality α-Fe2O3 pigment using iron removal residue in zinc hydrometallurgy. [ABSTRACT FROM AUTHOR]

Iron (Fe) removal is a critical step in the hydrometallurgical zinc (Zn) extraction process. Hematite, a stable Fe precipitate, offers an environmentally friendly option that complies with environmental protection standards. While existing research primarily focuses on hematite process technology, there is a lack of studies on how ions in ZnSO4 leaching solutions affect Fe removal efficiency and hematite particle size distribution. This study investigated the influence of manganese II (Mn(II)) and magnesium II (Mg(II)) concentrations and temperature on both Fe removal efficiency and hematite particle size distribution in ZnSO4 leaching solution. The results indicated that at various temperatures, the highest Fe removal efficiency occurred with an initial Mn(II) concentration of 10 g/L and an Mg(II) concentration of 15 g/L. As the concentrations of Mn(II) and Mg(II) as well as temperature increased, FeSO₄ crystallization also increased, which adversely affected hematite precipitation. The average particle size of hematite decreases from 300 to 100 nm, resulting in a more uniform particle size distribution, which correlated with the homogeneous solution saturation precipitation mechanism. However, the number of rod-shaped, regular small particles decreases, while the number of irregular, blocky particles increased. [ABSTRACT FROM AUTHOR]