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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]

In this study, ultrasound-enhanced calcium carbonate precipitation was used to enrich indium in zinc oxide dust leachate, and the effects of precipitation endpoint pH and ultrasound power on the indium precipitation behaviour were investigated, and the optimal conditions of ultrasound-enhanced precipitation were obtained to be the precipitation endpoint pH of 4.0 and the ultrasound power of 200 W. The precipitation rate of indium under these conditions was 99.79 %. At the same time, the effects of ultrasonication and conventional stirring on the indium precipitation kinetics were compared, which proved that ultrasound can shorten the time for precipitation to reach equilibrium and reduce the amount of calcium carbonate used, and the theory of ultrasonication activation energy was put forward. The activation energy of ultrasonication was Eu-a = 2.63 KJ/mol, and that of conventional precipitation was 9.78KJ/mol, which proved that ultrasonication could reduce the activation energy of the precipitation reaction, and promote the rapid precipitation reaction. The kinetic model of ultrasound-enhanced indium precipitation is lnC0-lnCt = exp(0.11339–318.54/W).t + A. In addition, the mechanism of ultrasound-enhanced calcium carbonate precipitation of indium was revealed by XRD, SEM-EDS, XPS and TEM analyses of the precipitated residue, it was demonstrated that ultrasound can inhibit the precipitation of zinc, and the ZnCO3 phase was found in the ultrasonically precipitated residue. This study provides a new idea for indium enrichment, and the future focus will be on the scale-up of the ultrasound-enhanced precipitation device.

This study investigates the ultrasonic-microwave synergistic intensive leaching of indium from zinc oxide dust and compares it with conventional leaching, single ultrasonic leaching, and microwave leaching. Additionally, the temperature rise behavior of zinc oxide dust in a sulfuric acid system is examined. The results demonstrate that ultrasonic-microwave co-leaching significantly reduces leaching time compared with conventional leaching and improves the leaching rate of indium compared with single ultrasonic leaching and microwave leaching. The optimal process conditions for ultrasonic-microwave synergistic leaching are determined to be an ultrasonic power of 200 W, microwave power of 200 W, leaching time of 30 min, sulfuric acid concentration of 180 g L−1, and liquid to solid ratio of 8:1. Under these conditions, the leaching rates of indium, zinc, aluminum, and iron are 91.25, 97.69, 74.57, and 48.62%, respectively. In contrast, under the same conditions, the leaching rates of indium and zinc by single ultrasonic leaching were 89.01 and 94.12%, respectively, and the leaching rates of indium and zinc by single microwave leaching were 88.59 and 95.59%, respectively. These findings indicate a synergistic effect of ultrasound and microwave. The accuracy of the single factor optimization experiment results was verified using the response surface analysis method to optimize the experimental conditions. The results indicated that the single factor optimization experiment was accurate. Studies in chemical kinetics studies demonstrated that the leaching of indium is primarily influenced by ultrasound microwave power and sulfuric acid concentration. Additionally, the leaching process is governed by chemical reactions. Arrhenius diagram was used to plot the (1/W–lnK) and (ln[H2SO4] − lnK) diagrams. The reaction coefficient for ultrasound-microwave is − 7.5, and the reaction order for sulfuric acid is 0.815. The chemical kinetic models are: 1 − (1 − x)1/3 = exp(− 4.12 − 7.5/W).t, 1 − (1 − x)1/3 = exp(− 4.654 + 0.815ln[H2SO4]).t. The mechanism of ultrasonic-microwave synergistic enhancement for leaching indium from zinc oxide dust was elucidated. This research introduces a novel method for indium leaching, which holds significant theoretical and practical implications. Future research should focus on enhancing the amplification technology of ultrasonic-microwave leaching equipment. [ABSTRACT FROM AUTHOR]

Zinc oxide dust (ZOD) is an industrial solid waste produced in the production process of wet smelting Zn, with large output and great pollution to the environment. The recycling of metallurgical solid waste such as zinc oxide dust is very important to achieve the sustainable development of the circular economy. An experimental study of zinc (Zn) leaching from zinc oxide dust using an ultrasound-enhanced ammonia–ammonium chloride system was performed. The effects of ultrasonic power, leaching time, total ammonia concentration, and other factors on the leaching rate of zinc from zinc oxide dust were investigated. The results revealed that the leaching rate of Zn reached up to 80.70% under the condition of ultrasound power of 1000 W, reaction time of 15 min, total ammonia concentration of 6 mol/L, [NH3]:[NH4+] of 1:1, L/S of 5:1, temperature of 45 °C, and stirring speed of 100 r/min. The conventional leaching was conducted under similar conditions, except that the time was controlled to 40 min and the zinc leaching rate was 71.15%. The leaching rate of Zn in the ultrasound condition was improved by 9.55% compared with that in the conventional leaching process. XRD, laser particle size, and SEM-EDS analyses were conducted to study the leaching residues of ZOD. The analysis results showed that in the ultrasound condition, the largest leaching rate of soluble ZnO phases was achieved after 15 min of leaching. Under the ammoniacal system, it was difficult to leach ZnFe2O4, Zn2SiO4, and ZnS phases, which partly accounted for the low zinc leaching rate. Additionally, through ultrasound-enhanced treatment, the ZnO particles encapsulated in ZOD particles were broken into smaller sizes and exposed to the leaching solution. Thus, the leaching rate of Zn was improved. The experimental results show that ultrasound can tremendously improve the effect of Zn extraction from ZOD, shorten reaction time, and help reduce energy consumption and environmental pollution, making it a promising application in the treatment of secondary Zn resources. [ABSTRACT FROM AUTHOR]

Based on the analysis of the physicochemical characteristics and thermodynamics of zinc peroxide dust, the leaching of zinc and enriching of indium from zinc oxide dust by sulfuric acid was studied. The effects of sulfuric acid mass concentration, liquid volume/solid mass ratio, leaching time, leaching temperature, stirring speed and leaching times on leaching zinc and enriching indium were investigated. The results show that under the conditions of sulfuric acid mass concentration of 100 g/L, liquid volume/solid mass ratio of 5 mL/1 g, leaching time of 90 min, leaching temperature of 60 °C and stirring speed of 500 r/min for leaching once, indium is almost not leached assuringly, zinc leaching rate can reach more than 70%. And high enrichment of indium, lead and other metals can be realized. [ABSTRACT FROM AUTHOR]

Insufficient reaction between dust and sulfuric acid during leaching of zinc oxide dust containing germanium is a major reason for the low leaching efficiency of germanium. This paper makes use of the unique physical effect of ultrasonic wave to play an important role in strengthening the leaching process. Research found that with ultrasonic enhanced leaching, on the one hand, the surface tension and viscosity of the leaching solution decreased by 5.94 and 32.73 %, respectively; on the other hand, for the leached mineral, the contact angle decreases, the surface free energy increases by 9.43 %, the particle size decreases 40.92 %, and the specific surface area and pore volume respectively increase 94.10 and 54.05 %, which reduces the contact resistance between sulfuric acid and dust, making the reaction between them more completely and in-depth. Therefore, the leaching rate is accelerated and the germanium leaching efficiency is increased. Under ultrasonic condition, the leaching efficiency of germanium is enhanced by 3.94 % and the time to reach equilibrium is shortened by about 40.00 %. The above findings can provide theoretical guidance for the extended application of ultrasound in hydrometallurgy and the efficient leaching of germanium-containing zinc oxide dust. [ABSTRACT FROM AUTHOR]

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recovering germanium from zinc oxide dust (ZOD) produced from Pb–Zn smelter is an important pathway to extract germanium. However, the leaching efficiency of industrial germanium production is not satisfactory (usually less than 75 %). Therefore, the leaching behavior of Ge in different phases was discovered in this work. Ge in the ZOD mainly occurs in oxide, sulfide, silicate, and solid insoluble. The potential decides the oxidative dissolution of sulfide. The leaching recovery of zinc and germanium were 90 % and 80 % with oxidant, and 78 % and 80 % without oxidant, respectively. The effect sequence of oxidant type on the Zn leaching efficiency was MnO2 > H2O2 ≈ oxygen > air, but the type and addition of oxidant had no obvious effect on the leaching recovery of germanium. The final pH of leaching slurry limits the dissolution of oxide and hydrolysis-polymerization of impurity ions (such as Fe(III) and Si). Decreasing the final pH is beneficial to the leaching reaction of Zn and Ge. The germanium presented in oxide and sulfide is easy to leach, while the leaching of germanium existed in silicate and solid insoluble is relatively difficult. The structure of aluminate can be destroyed effectively using a 40 g/L HF solution. When the leaching percent of SiO2 is 86.82 %, the leaching recovery of Ge is 96.57 %. For the ZOD with higher content of Fe and Si, germanium leaching is negatively correlated with the content of Fe and Si in the ZOD. The results provide a scientific basis for improving the leaching recovery of germanium. [ABSTRACT FROM AUTHOR]

Low leaching efficiency of germanium has always been a difficult point hindering the efficient utilization of zinc oxide dust containing germanium. Based on the previous research results that the formation of insoluble Fe4Ge3O12 leads to germanium loss in the leaching process, a new process of reduction leaching of zinc oxide dust containing germanium enhanced by ultrasonic and iron powder is proposed. Under optimized conditions, the germanium leaching efficiency can be increased by 9.17%, reaching 93.43%. When leaching, the addition of iron powder can reduce the Fe3+ formed in the leaching process and hinder the formation of insoluble Fe4Ge3O12, which can increase the leaching efficiency of germanium by 5.30%. At the same time, strong mechanical action of ultrasonic can fully disperse the iron powder in the leaching system, avoiding the phenomenon of insufficient local reduction. More importantly, the addition of ultrasonic can reduce the dissolved oxygen in the solution system and produce strong reducing hydrogen free radicals (·H), strengthening the reduction leaching effect, thus the germanium leaching efficiency is further increased by 3.87%. The research results provide a new method and theoretical guidance for the efficient utilization of zinc oxide dust containing germanium, which is of great significance.

Germanium plays an essential role in many high-tech fields because of its excellent electrical and optical properties. As a zinc refining by-product, zinc oxide dust (ZOD) is one of the most important sources of germanium recovery. However, the low leaching efficiency of germanium seriously hinders germanium recovery. This study focuses on the phase evolution and elemental distribution of zinc and germanium during the zinc refining process by analyzing the occurrence state of zinc and germanium in products and the key factors and chemical reactions causing the loss of zinc and germanium during the process. In the sulfuric-acid leaching process without an oxidant, the sulfides encapsulating germanium cannot be leached, which resulted in a loss of germanium. In addition, the formation of an insoluble PbSO 4 coating layer and silica compounds during the sulfuric-acid leaching impeded the leaching reactions. Accordingly, pre-treatment by oxidative leaching with Fe3+ and the role of NaAc in dissolving PbSO 4 were tested. The efficiency of Ge recovery is approximately 30 % higher than that of the conventional leaching process. [Display omitted] • Whole process analysis of behaviors of zinc and germanium during the zinc refining process. • Phase evolution and element distribution of zinc and germanium. • Summarize the main factors limiting germanium recovery and their origin. • Corresponding suggestions for improving the recovery process of zinc and germanium. [ABSTRACT FROM AUTHOR]

• Demonstrating the efficacy of microwave roasting on the properties of ZnO dust. • Analyze the phase transformations and structural changes by microwave roasting. • Offering a comparison between the microwave-assisted process and conventional methods. • The leaching percentage of germanium increase by 22 % after proper microwave roasting. In this study, a microwave roasting-sulfuric acid leaching process was proposed to increase the efficacy of extracting germanium (Ge) from Ge-bearing zinc oxide (ZnO) dust. Microwave energy has a selective cleavage effect on ZnO dust. Proper microwave roasting of Ge-bearing ZnO dust can fracture the ZnO dust, reduce the particle size, increase the particle size uniformity and specific surface area, and transform the phase of Fe 4 Ge 3 O 12 , thus improving the leaching percentage of Ge from the ZnO dust. The optimized conditions were as follows: microwave heating temperature of 290°C, microwave heating time of 5 min, liquid-solid ratio of 6 mL/g, leaching time of 4 h, initial concentration of sulfuric acid of 9 mol/L, and leaching temperature of 60 °C; the leaching percentage of Ge was 84.4 %. In contrast, the leaching percentage of Ge was found to be 62.4 % under the same conditions without roasting. In this study, we described a promising strategy for leaching Ge from ZnO dust via the microwave roasting-sulfuric acid leaching process. [Display omitted] [ABSTRACT FROM AUTHOR]

A carbothermal reduction process simulating EAF process is used to handle the zinc oxide dust, and the zinc in the dust can be extracted and recovered efficiently. The crude zinc and lead-tin alloy were obtained finally. The effects of temperature, holding time, and reductant dosage on zinc volatilization rate were investigated, and the “Pelletizing - Calcination- Carbothermic reduction” experiment was conducted. The results found the optimal reduction condition was as follows: the temperature of 1300℃, reductant dosage of 14.04%, and holding time of 120 min. After the calcination at 900℃ for 120 min, the removal rates of fluorine, chlorine, and sulfur in the dust were 98.18%, 96.38% and 28.58% respectively, and the volatilization rate of zinc was 99.83% in the reduction process. The zinc content of the crude zinc was 68.48%.

Based on the problems existing in the existing process, the ultrasonic field enhanced potassium dichromate atmospheric leaching of zinc and germanium in zinc oxide dust was studied, and three main factors (liquid‐solid ratio, leaching temperature and potassium dichromate concentration) were optimized by the Box‐Behnken design (BBD) model. XRD, ICP‐OES, EPMA and SEM results show that the occurrence state of Ge is highly correlated with ZnS. Promoting the dissolution of ZnS is the basis for improving the leaching rates of Zn and Ge. Finally, under the conditions of liquid‐solid ratio of 7 mL/g, leaching temperature of 90 °C and potassium dichromate concentration of 19.16 g/L, the leaching rates of zinc and germanium were 99.968 % and 90.395 %, respectively. The error between the prediction results of the quadratic model and the experimental results is small, and the correlation coefficients are greater than 0.99, indicating that the model is credible. [ABSTRACT FROM AUTHOR]

Zinc-containing solid waste produced during the smelting process of iron and steel plant is volatilized by fuming to produce zinc oxide dust, which has the characteristics of wide sources, complex components, and large fluctuations of raw materials. In view of the problems of poor adaptability of raw materials, low direct yield of zinc and difficult enrichment of lead in leaching residue during the traditional zinc hydrometallurgy process, a new method of oxidation and pressure acid leaching technology was proposed. The effects of liquid-solid ratio, reaction time, leaching temperature, oxidant, and other factors on the leaching efficiency of zinc, indium, and main metal irons were investigated. The results showed that the leaching efficiency of zinc is more than 80% under the optimal of oxidation neutral leaching at the temperature of 60 ℃, the liquid-solid ratio of 3. 9 mL/g, the leaching time of 1 h, the neutralization time of 2 h, and the dosage of hydrogen peroxide of 62 mL/kg. In this case, the concentration of iron in the leaching solution less than 20 mg/L, and the precipitation of zinc and iron can be realized simultaneously, which is easy for subsequent solution treatment. In the pressure acid leaching process, the sulfide is oxidized via using the precipitated ferric irons in the oxidation neutral leaching. Results display that the total leaching efficiency of zinc and indium reached 98% and 90%, respectively, at the conditions of no oxidant, temperature 125 ℃, liquid-solid ratio 2. 5 mL/g and leaching time of 3 h, and the acid concentration of leaching agent is 150 g/L. Moreover, zinc and indium were leached simultaneously and efficiently, and the valence state of iron in the leaching solution can be controlled synchronously. The concentration of iron ions in the pressurized acid leaching solution is about 17 g/L, in there, and the concentration of the ferrous ions is about 16 g/L. The content of lead in the residue is more than 30%, and the enrichment ratio is high. What's more, the aims of increasing the zinc direct yield, simplifying the process, improving the adaptability of raw materials, and the efficient resource utilization of zinc oxide dust were realized via oxidation leaching-pressure acid leaching method. [ABSTRACT FROM AUTHOR]

Currently in China, the waste acid generated from large-scale smelting plants is treated as “wastewater with high concentration of heavy metals”, which leads to high cost and many wastewater treatment residues (hazardous wastes). In this paper, based on the main components of waste acid and zinc oxide dust, the adoption of a cyclic leaching process was proposed, in which zinc oxide dust is leached by waste acid, thus enabling the recovery of copper (Cu) and zinc (Zn) from the circulating leaching solution and the central treatment of arsenic (As). The main factors affecting the first and second cyclic leaching processes were investigated, including the final pH, leaching temperature, and leaching time. After leaching was completed, several factors in the first and second As removal processes were investigated, including the H2O2 dosage, Na2S dosage, removal temperature, and removal time. The following optimal conditions were identified: the optimal final pH, leaching temperature, and leaching time for the first leaching are 1.5, 85 ℃, and 5 h, respectively. The optimal final pH and leaching temperature for the second leaching are 4 and 85 ℃, respectively. The optimal H2O2 dosage, removal temperature, and removal time for the first As removal are 0.067 mL per 1 mL of the secondary circulation leaching solution, 40 ℃, and 1.5 h, respectively. The optimal Na2S dosage for the second arsenic removal is 0.02 mL per 1 mL of the second circulation leaching solution, and the removal temperature and removal time were determined to be 35 ℃ and 2 h, respectively. Under these conditions, the concentrations of As, Cu, and Zn can be reduced to 3.26, 2.63, and 50.63 mg·L−1, respectively. The pH of the wastewater after processing was neutral, which meets the integrated wastewater discharge standard with minor treatment. In this way, valuable components in the waste acid can be comprehensively recovered, and the harmful element As centrally treated, thus reducing the production of hazardous wastes, saving energy, and reducing emissions.

A new process of leaching zinc oxide dust by ozone oxidation in a sulfuric acid system was studied. The main factors affecting the leaching rate, such as ozone time, leaching temperature, initial acidity, leaching time, and liquid/solid mass ratio, were comprehensively investigated. The results show that leaching efficiency depends on all the above factors. The optimum conditions for leaching Zn and Ge from zinc oxide dust are as follows: ozone time 10 min, leaching temperature 90 ℃, initial acidity 160 g/L, leaching time 60 min, and liquid/solid mass ratio 7:1. Under the optimum conditions, the leaching rates of Zn and Ge are 95.79% and 93.65%, respectively. The leaching rates of zinc and germanium in the ozone leaching are 4.05% and 10.49% higher than those of the atmospheric leaching, respectively. Therefore, it is determined that ozone in solution plays a key role in rapidly oxidizing sulfide and releasing encapsulated germanium. Sulfuric acid-ozone media can efficiently extract Zn and Ge from zinc oxide dust.

[Display omitted] • This study developed a new strategy for the utilization of the zinc oxide dust resource. • Preparation of spinel zinc ferrite by conversion of the insoluble zinc and iron components in zinc oxide dust by roasting. • After ball milling for 2 h, the roasted product showed excellent activity for organic pollutants degradation and magnetic separation and recycling. • The mechanisms of solid phase reaction and modification of roasted product by ball milling were investigated. The resource utilization of zinc oxide dust (ZOD) is mainly focused on the efficient recovery of zinc by acid leaching at present. Because of a large amount of iron in ZOD and zinc components existing in multi-phase, the problems of low zinc recovery and the separation of zinc and iron ions in the leaching solution are unavoidable. Considering the characteristics of ZOD and the advantages of spinel zinc ferrite (ZnFe 2 O 4) in the advanced oxidation degradation of organic wastewater, a new strategy for clean utilization of ZOD is proposed. The leaching efficiency of soluble zinc components in ZOD reached 96.7 % by selective dissolution with low concentration sulfuric acid solution, and the leaching solution without iron ions can be directly used for electrolytic zinc recovery. The insoluble components of zinc and iron in the leaching residue were converted into ZnFe 2 O 4 by solid phase roasting. By adjusting the roasting temperature, time and molar ratio of Fe/Zn in roasting process, the proportion of zinc elements in the form of ZnFe 2 O 4 reached 99.56 % and a single spinel zinc ferrite product was obtained. Zinc ferrite product activated by ball milling for 2 h (ZFO-2) showed very high catalytic activity in the treatment of organic wastewater by peroxonosulfate (PMS). In the presence of 1 mM PMS and 1 g/L ZFO-2 at 20 °C, the ZFO-2/PMS system achieved a removal rate of over 90 % within 40 min for wastewater containing RhB, MO and MG (10 mg/L). In addition, ZFO-2 is ferromagnetic and easily recovered by magnetic separation. The new strategy proposed in this paper takes into account the efficient recovery of soluble zinc components and the cooperative high-value utilization of insoluble components of zinc and iron in ZOD, which is a comprehensive utilization method with more sustainable resource allocation. [ABSTRACT FROM AUTHOR]

Germanium, an important metal, is widely used in many high-tech fields, such as semiconductor, aerospace measurement and control, nuclear physical detection, etc. Zinc oxide dust is an industrial solid waste produced by lead-zinc smelting enterprises. Germanium in zinc oxide dust has considerable recycling potential and is a research focus at h om e and abroad. In this paper, the occurrence state and extraction status oI germanium in zinc oxide dust are reviewed. The research progress of germanium extraction and recovery methods from zinc oxide dust at home and abroad was systematically reviewed. The basic principles of atmospheric pressure acid leaching, pressure acid leaching, ultrasonic strengthening acid leaching and microwave pretreatment were described. The advantages and disadvantages of different methods were pointed out from the applicability of process routes, control of reaction conditions,recovery and extraction efficiency of germanium, energy consumption and cost. It is suggested that in the leaching process of zinc oxide dust, the refractory substances in the dust can be leach at the same time, so that the zinc and germanium can be leached efficiently and the iron valence state in the solution can be controlled synchronously. Further study on the mechanism of strengthening leaching, simplifying the production process and reducing the production cost are the development direction of zinc and germanium recovery in the future. [ABSTRACT FROM AUTHOR]

An experimental study was carried out on the extraction process of zinc oxide dust with tartarate. The effects of NH$ H20、NH$ (NH4)2O6C4H4 H2O、NHS C4H6O6 H2O、NH3 C4H8Na2 O8 H2O and(NH4)2 O6C4 H4 H2 O systems on the zinc leaching rate were investigated, respectively, The results showed that the extraction effect of NH3 C4 H6 0$ H2 O system was better. The influences of tartaric acid concentration, leaching time and stirring speed on the zinc leaching rate under the NH3 C4 H6 0$ H2 O system were further studied. The results showed that the zinc leaching rate reached 76. 59% under the condition： the concentration of tartaric acid was controlled at 0. 7mol/L, the concentration of ammonia water was 5 mol/L, the leaching time was 40 min, the stirring speed was 400 r/min, the liquid solid ratio was 5: 1, and the leaching temperature was 25 °C. The concentration of tartaric acid, time, stirring speed and the ratio of liquid to solid were significantly affected for the zinc leaching rate. X ray diffraction (XRD)and FT IR spectrum analysis showed that the coordination dissolution of ZnO could be realized in NH3 C4 H$ Oe H2O system, and ZnS was difficult to be dissolved in the ammoniacal system of tartaric acid and tartarate. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The technological experiments of neutral leaching-acid leaching on alkaline leaching residues of zinc oxide dusts from lead smelting were studied systematically. The results show that the leaching rate of zinc and cadmium from alkaline residues increases first with the increase of leaching temperature, liquid-solid ratio, agitation speed and time, and then slows down. The liquid-solid ratio has no significant effect on the leaching rate of zinc and indium during acid leaching. The leaching rate of zinc and indium increases first and then decreases with the increase of initial acid concentration, leaching temperature, and time. The optimum conditions for neutral leaching are:the temperature 338 K, liquid-solid ratio 5∶1, the stirring speed 400 r/min, and the leaching time 1 h. Under this condition, the leaching rates of zinc and cadmium are 80. 3%and 76. 3%, respectively. The optimum conditions for acid leaching of neutral leaching residue are:the initial sulfuric acid concentration 100 g/L, the leaching time 2 h, the leaching temperature 363 K, and the liquid-solid ratio 5∶1. Under this condition, the leaching rates of zinc and indium are 97. 1% and 85. 5%. [ABSTRACT FROM AUTHOR]

Cavity perturbation method was used to determine the dielectric properties (ε′, ε″, and tan δ) of zinc oxide dust. The process of dechlorination from zinc oxide dust by microwave roasting was evaluated considering the effect of different roasting temperatures and holding times. The research results showed that the ZnCl2 and PbCl2 with high-loss factor were heated preferentially by microwave, and the dechlorination rate can reach 97.22% after microwave roasting at 650°C for 40 min. The phases of zinc oxide dust before and after microwave roasting were observed and characterized by X-ray diffraction (XRD) analysis. The kinetics of dechlorination from zinc oxide dust was investigated. The three kinetic factors were obtained by the dynamic isothermal method, which provided a theoretical basis for dechlorination from zinc oxide dust. Thermodynamic analysis showed that the volatilization of chlorides was mainly ionic crystal phase transition process. The volatile kinetics of zinc oxide dust were controlled by the solid state diffusion and interface chemical reaction, during the microwave heating, with an activation energy E=46.6 KJ/mol and the reaction order n is level 1.

The new technology of dechlorination from zinc oxide dust by microwave roasting was investigated, combined with the advantages of microwave selective heating and based on a thermodynamic analysis of zinc and lead halides. The associated dechlorination reactions were discussed in details and the effect of all the influencing parameters such as roasting temperature, holding time, stirring speed and air flow were systematically investigated. Experimental results showed that zinc oxide dust dechlorination rate could reach over 95% and meet the requirements of wet smelting electrolysis, given an air flow of 300 L/h, a stirring speed of 60 r/min, a roasting temperature of 650 °C and a holding time of 30 min. Microwave roasting provided a new solution to the dechlorination from zinc oxide dust.

• A phase analysis method of germanium was established. • The ultrasonic enhanced leaching process was optimized. • Ultrasound can reduce the cluster structure of particles. • Ultrasound can strengthen the leaching of germanate. Aiming at the problem of low extraction efficiency of germanium in zinc oxide dust, a process of strengthening germanium leaching by ultrasonic wave in sulfuric acid leaching process was proposed. The effects of acidity, temperature, time, liquid-solid ratio, ultrasonic power and amount of iron powder on germanium leaching were investigated by response surface method, and the ultrasonic enhanced leaching process was optimized. Based on process mineralogy analysis, and germanium phase distribution analysis, which is obtained by self-establishment step-by-step extract method, the studied zinc oxide dust contains 94.1% germanium oxide and germanate, 5.13% germanium sulfide and 0.77% insoluble germanium. The results showed sulfuric acid concentration 131 g/L(1.34 mol/L), temperature 78 °C, time 22 min, liquid-solid ratio 7.6:1, ultrasonic power 270 W, iron powder content 0.71%. The leaching efficiency of germanium is 95.19%, which is 5.79% higher than that of conventional leaching method. It was found that ultrasound can destroy the particle size, reduce the cluster structure of leached products by 13.5%, inhibit the agglomeration of particles, and promote the leaching of germanate and germanium sulphide. This study is of great significance for the production of germanium. [Display omitted] [ABSTRACT FROM AUTHOR]

The present work provides a study on high concentration of arsenic removal from acid leaching solution of zinc oxide dust by water-quenched slag. The water-quenched slag is a waste slag produced from fuming furnace of lead pyrometallurgical process and used as a substitute of ferrous sulfate heptahydrate to precipitate arsenic at purification section. The effects of reaction temperature, reaction time, the addition of H2O2 and the addition of water-quenched slag on arsenic removal rate were systematically investigated. The reaction temperature of 70°C, reaction time of 1 h, H2O2 addition of 10.8 mL/L and water-quenched slag addition of 17.8 g/L are identified as the best technical parameters. At the optimum conditions, the arsenic (III) with high concentration (As 4.13 g/L) is efficiently removed (arsenic removal rate > 99%). The filtrate (Fe 1.21 mg/L, As 1.53 mg/L) with low concentrations of arsenic and iron and the stable filter residue are also obtained successfully. The United States EPA Toxicity Characteristic Leaching Procedure (TCLP) test shows that the As leachability never exceeds the regulatory limit of 5 mg/L As. The results suggest that the water-quenched slag shows potential for removing high concentration of arsenic from acid leaching solution of zinc oxide dust. [ABSTRACT FROM AUTHOR]

Low leaching efficiency of germanium has always been a difficult point hindering the efficient utilization of zinc oxide dust containing germanium. Based on the previous research results that the formation of insoluble Fe 4 Ge 3 O 12 leads to germanium loss in the leaching process, a new process of reduction leaching of zinc oxide dust containing germanium enhanced by ultrasonic and iron powder is proposed. Under optimized conditions, the germanium leaching efficiency can be increased by 9.17%, reaching 93.43%. When leaching, the addition of iron powder can reduce the Fe3+ formed in the leaching process and hinder the formation of insoluble Fe 4 Ge 3 O 12, which can increase the leaching efficiency of germanium by 5.30%. At the same time, strong mechanical action of ultrasonic can fully disperse the iron powder in the leaching system, avoiding the phenomenon of insufficient local reduction. More importantly, the addition of ultrasonic can reduce the dissolved oxygen in the solution system and produce strong reducing hydrogen free radicals (H), strengthening the reduction leaching effect, thus the germanium leaching efficiency is further increased by 3.87%. The research results provide a new method and theoretical guidance for the efficient utilization of zinc oxide dust containing germanium, which is of great significance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new leaching method of zinc and germanium was designed. • The occurrence state of Ge, Fe, Si and Zn before and after leaching was shown. • The leaching rate was increased by 10% and the reaction time was shortened by 50%. • Lead is highly enriched and recovered. As a byproduct of lead and zinc smelting, zinc oxide dust often contains abundant valuable metals such as zinc and germanium. To improve the leaching of zinc and germanium in sulfuric acid, the correlation between germanium and other elements in zinc oxide dust, the phase composition of the main elements, and Eh-pH dominant area of germanium were analyzed. Finally, ultrasonic waves and potassium dichromate were added to enhance the leaching of zinc and germanium in the leaching process. The results show that the best recoveries of zinc and germanium are 99.25 % and 90.44 %, respectively, under the optimum conditions. Compared with the existing process, the leaching rate is increased by 8 ∼ 10 % and the leaching time is reduced by more than 50 %. There are fewer impurities in the leaching residue after leaching, and the lead content is about 50 % and can be directly recycled back into the lead smelting process for recycling. In conclusion, the oxidation leaching of zinc and germanium from zinc oxide dust with potassium dichromate under ultrasound proves to be efficient, economical and practical. [ABSTRACT FROM AUTHOR]

The response surface model for dechlorination process of zinc oxide dusts by microwave was built with an analysis of variance (ANOVA). It was introduced to analyze the dechlorination experimental results, and the model fit well. The central composite design (CCD) was applied to optimize and investigate the influence of roasting temperature, holding time, stirring speed and those interactions to dechlorination efficiency. According to the prediction and optimization function of Design Expert software, the optimum conditions of dechlorination by microwave roasting were found. When controlling roasting temperature to 626 °C, holding time 25 min and stirring speed 54 rpm, the experimental result of dechlorination efficiency could reach 90.13% which is very close to the predicted dechlorination efficiency of 90.48%, indicating that the response surface methodology optimization of process parameters for dechlorination of zinc oxide dusts by microwave roasting are reliable. [ABSTRACT FROM AUTHOR]

Sustainable disposal of granite waste (GW) and hazardous zinc oxide dust (ZOD) via the clean production of some cementitious pastes is the main target of this study. The rheological performance, setting times, physico-mechanical characteristics, morphological features, phase composition and antifungal activity, were investigated. Six composites have been prepared by blending OPC with different percentages of GW (0, 5, 10, 15, 20, 25 wt%) in addition to the other two green composites containing OPC-25%GW-1%ZOD and OPC-25%GW-2%ZOD. The rheological parameters of the blended fresh pastes have been measured by the Bingham model; the data confirmed that increasing the content of GW as well as elevating temperature up to 45 °C caused a significant increase in viscosity and yield stress. The outcomes of setting times demonstrated that ZOD acted as a strong retarder for hydration reaction. From the economic and environmental point of view, the GW can be used up to 25 wt% cement replacement, as reasonable compressive strength was delivered, 67 MPa after 28-days of curing under tap water. Various hydration products were detected via XRD, TGA/DTGA, FTIR and SEM. According to ASTM D4300-1, OPC-25%GW modified by 2 wt% ZOD demonstrated highly efficient anti-fungal for different micro-organism strains such as Aspergillus niger and Aspergillus terreus, and Aspergillus fumigatus. [Display omitted] [ABSTRACT FROM AUTHOR]

• Recycling of zinc oxide dust using ChCl-urea with nitrilotriacetic acid as complexing agents. • The effects of important parameters on the leaching process were investigated. • Optimization of process conditions using surface response methodology. • Under optimal experimental conditions, the maximum recovery of zinc was up to 87.9%. The leaching of zinc from zinc oxide dust was investigated in choline chloride-urea deep eutectic solvent (ChCl-urea DES) with the addition of nitrilotriacetic acid (NTA). The effect of important parameters on leaching process, such as leaching temperature, leaching time, liquid/solid ratio and NTA concentration was investigated and the optimization was done using surface response methodology (RSM) based on central composite design (CCD). The optimum condition for leaching of zinc from zinc oxide dust was identified to be a leaching temperature of 79.0 °C, a leaching time of 35.4 h, a liquid/solid ratio of 12.1 and an NTA concentration of 0.07 mol/L. A maximum of 87.9% of zinc was recovered under the optimum experimental conditions. The leaching process is controlled by diffusion and the corresponding activation energy is 26.2 kJ/mol. The resultant leaching solution was directly used for the electrodeposition of zinc, and pure zinc deposit is obtained. [ABSTRACT FROM AUTHOR]

A new process of leaching zinc oxide dust by ozone oxidation in a sulfuric acid system was studied. The main factors affecting the leaching rate, such as ozone time, leaching temperature, initial acidity, leaching time, and liquid/solid mass ratio, were comprehensively investigated. The results show that leaching efficiency depends on all the above factors. The optimum conditions for leaching Zn and Ge from zinc oxide dust are as follows: ozone time 10 min, leaching temperature 90 ℃, initial acidity 160 g/L, leaching time 60 min, and liquid/solid mass ratio 7:1. Under the optimum conditions, the leaching rates of Zn and Ge are 95.79% and 93.65%, respectively. The leaching rates of zinc and germanium in the ozone leaching are 4.05% and 10.49% higher than those of the atmospheric leaching, respectively. Therefore, it is determined that ozone in solution plays a key role in rapidly oxidizing sulfide and releasing encapsulated germanium. Sulfuric acid-ozone media can efficiently extract Zn and Ge from zinc oxide dust. [ABSTRACT FROM AUTHOR]

The present study measures dielectric properties (ε', ε" and tanδ) of zinc oxide dust produced in a rotary kiln, using a cavity perturbation method with microwaves at 2.45 GHz. The effect of apparent density of the dust on the dielectric properties was determined. The results indicated that zinc oxide dust has excellent absorbing performance and can reach 800 ºC in 6 minutes. The apparent density of zinc oxide dust and the microwave penetration depth were also related. [ABSTRACT FROM AUTHOR]