Thermodynamics and kinetics of extracting zinc from zinc oxide ore by the ammonium sulfate roasting method

Thermodynamic analyses and kinetic studies were performed on zinc oxide ore treatment by （NH4）2SO4 roasting technology. The results show that it is theoretically feasible to realize a roasting reaction between the zinc oxide ore and （NH4）2SO4 in a temperature range of 573-723 K. The effects of reaction temperature and particle size on the extraction rate of zinc were also examined. It is found that a surface chemical reaction is the rate-controlling step in roasting kinetics. The calculated activation energy of this process is about 45.57 kJ/mol, and the kinetic model can be expressed as follows： 1 - （1 - α）1/3 = 30.85 exp（-45.57/RT）·t. An extraction ratio of zinc as high as 92% could be achieved under the optimum conditions.

Recovery of zinc from low-grade zinc oxide ores by solvent extraction

The recovery of zinc from low-grade zinc oxide ores with solvent extraction-electrowinning technique was investigated by using D2EHPA as extractant and 260 # kerosene as diluent. The results show that it is possible to selectively leach zinc from the ores by heap leaching. The zinc concentration of leach solution in the first leaching cycle is 32.57 g/L, and in the sixteenth cycle the zinc concentration is 8.27g/L after solvent extraction. The leaching solution is subjected to solvent extraction, scrubbing and selective stripping for enrichment of zinc and removal of impurities. The pregnant zinc sulfate solution produced from the stripping cycle is suitable for zinc electrowinning. Extra-pure zinc metal was obtained in the electrowinning test under conventional conditions.

Extracting reaction mechanism analysis of Zn and Si from zinc oxide ore by NaOH roasting method

The orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore with NaOH aiming to comprehensively utilize zinc oxide ore.The optimized reaction conditions were molar ratio of NaOH to zinc oxide ore 6:1,roasting temperature 450°C,holding time 150 min.The molar ratio of NaOH to zinc oxide ore was the most predominant factor affecting the extraction ratios of zinc oxide and silica.The mineral phase transformations were investigated by testing the phases of specimens obtained at different temperatures.The process was that silica reacted with molten NaOH to form Na_2SiO_3 at first,then transformed into Na_4SiO_4 with temperature rising.ZnCO_3 and its decomposing product ZnO reacted with NaOH to form Na_2ZnO_2.Na_2ZnSiO_4was also obtained.The reaction rate was investigated using unreacted shrinking core model.Two models used were chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the reaction rate was combine-controlled by two models.The activation energy and frequency factor were obtained as 24.12 k J/mol and 0.0682,respectively.

Zinc extraction from zinc oxidized ore using(NH4)2SO4 roasting−leaching process

An improved method of(NH4)2SO4 roasting followed by water leaching to utilize zinc oxidized ores was studied.The operating parameters were obtained by investigating the effects of the molar ratio of(NH4)2SO4 to zinc,roasting temperature,and holding time on zinc extraction.The roasting process followed the chemical reaction control mechanism with the apparent activation energy value of 41.74 kJ·mol^−1.The transformation of mineral phases in roasting was identified by X-ray diffraction analysis combined with thermogravimetry–differential thermal analysis curves.The water leaching conditions,including the leaching temperature,leaching time,stirring velocity,and liquid-to-solid ratio,were discussed,and the leaching kinetics was studied.The reaction rate was obtained under outer diffusion without product layer control;the values of the apparent activation energy for two stages were 4.12 and 8.19 kJ·mol^−1.The maximum zinc extraction ratio reached 96%while the efficiency of iron extraction was approximately 32%under appropriate conditions.This work offers an effective method for the comprehensive use of zinc oxidized ores.

Reaction condition optimization and kinetic investigation of roasting zinc oxide ore using (NH_4)_2SO_4

An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using（NH_4）_2SO_4. The optimized reaction conditions are defined as an（NH_4）_2SO_4/zinc molar ratio of 1.4：1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of（NH_4）_2SO_4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric-differential thermal analysis was used for（NH_4）_2SO_4 and zinc mixed in a molar ratio of 1.4：1 at the heating rates of 5, 10, 15, and 20 K·min-1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle-Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.

Study on the pre-treatment of oxidized zinc ore prior to flotation

The pre-treatment of zinc oxide bearing ores with high slime content is important to ensure that resources are utilized optimally. This paper reports an improved process using hydrocyclone de-sliming, dispersion reagents, and magnetic removal of iron minerals for the pre-treatment of zinc oxide ore with a high slime and iron content, and the benefits compared to traditional technologies are shown. In addition, this paper investigates the damage related to fine slime and iron during zinc oxide flotation, the necessity of using hydrocyclone de-sliming together with dispersion reagents to alleviate the influence of slime, and interactions among hydrocyclone de-sliming, reagent dispersion, and magnetic iron removal. Results show that under optimized operating conditions the entire beneficiation technology results in a flotation concentrate with a Zn grade of 34.66% and a recovery of 73.41%.

Laboratory Study on the Removal of Fluorine from High Fluorine Bearing Zinc Oxide Ore

An ever increasing demand for zinc has resulted in worldwide efforts to exploit complex and lean grade reserves of zinc oxide ore. In this study experiments were done on zinc recovery from high-fluorine bearing zinc oxide ore. First the effect of different variables on fluorine removal was investigated. Optimum experimental conditions occurred when the temperature was 1173 K, roasting time was 90 min and air flow was at a velocity of 5 m/min, the fluorine removal from the samples reached over 93%. The results obtained indicate that fluorine removal is not enhanced by adding diluted sulfuric acid or water as a binder. Second the roasted materials were leached with a diluted sulfuric acid, neutralized, flocculated and filtrated. The which satisfies the requirement of fluorine residual fluorine content in the leached content in the leached solutions for the solutions was less than 38 mg/L production of electrolytic zinc.

Extraction and recycling technologies of cobalt from primary and secondary resources:A comprehensive review

Cobalt has excellent electrochemical,magnetic,and heat properties.As a strategic resource,it has been applied in many hightech products.However,the recent rapid growth of the battery industry has substantially depleted cobalt resources,leading to a crisis of cobalt resource supply.The paper examines cobalt ore reserves and distribution,and the recent development and consumption of cobalt resources are summarized as well.In addition,the principles,advantages and disadvantages,and research status of various methods are discussed comprehensively.It can be concluded that the use of diverse sources(Cu-Co ores,Ni-Co ores,zinc plant residues,and waste cobalt products)for cobalt production should be enhanced to meet developmental requirements.Furthermore,in recovery technology,the pyro-hydrometallurgical process employs pyrometallurgy as the pretreatment to modify the phase structure of cobalt minerals,enhancing its recovery in the hydrometallurgical stage and facilitating high-purity cobalt production.Consequently,it represents a promising technology for future cobalt recovery.Lastly,based on the above conclusions,the prospects for cobalt are assessed regarding cobalt ore processing and sustainable cobalt recycling,for which further study should be conducted.

Mathematical model of the direct reduction of dust composite pellets containing zinc and iron

Direct reduction of dust composite pellets containing zinc and iron was examined by simulating the conditions of actual production process of a rotary hearth furnace （RHF） in laboratory. A mathematical model was constructed to study the reduction kinetics of iron oxides and ZnO in the dust composite pellets. It was validated by comparing the calculated values with experimental results. The effects of furnace temperature, pellet radius, and pellet porosity on the reduction were investigated by the model. It is shown that furnace temperature has obvious influence on both of the reduction of iron oxides and ZnO, but the influence of pellet radius and porosity is much smaller. Model calculations suggest that both of the reduction of iron oxides and ZnO are under mixed control with interface reactions and Boudouard reaction in the early stage, but only with interface reactions in the later stage.

Nickel solvent extraction from cold purification filter cakes of Angouran mine concentrate using LIX984N

Cold purification filter cakes generated in the hydrometallurgical processing of Angouran mine zinc concentrate commonly contain significant amounts of Zn, Cd, and Ni ions and thus are valuable resources for metal recovery. In this research, a nickel containing solution that was obtained from sulfuric acid leaching of the filter cake following cadmium and zinc removal was subjected to solvent extraction experiments using 10vol%LIX984N diluted in kerosene. Under optimum experimental conditions （pH 5.3, volume ratio of organic/aqueous （O：A） = 2：1, and contact time -5 min）, more than 97.1% of nickel was extracted. Nickel was stripped from the loaded organic by contacting with a 200 g/L sulfuric acid solution, from which 77.7% of nickel was recovered in a single contact at the optimum conditions （pH 1-1.5, O：A =5：1, and contact time =15 min）.

Zn release from fluid inclusions in a natural sphalerite

The type, size, and compositions of fluid inclusions in a natural sphalerite were investigated and the total concentration of Zn released from the fluid inclusions was measured. To compare the total concentration of Zn released from the fluid inclusions with that dissolved from the sphalerite itself, dissolution experiments and theoretical calculations for the dissolution equilibrium of the sphalerite were also performed. The results indicate that large numbers of fluid inclusions with various sizes exist in the sphalerite, which can be divided into four types, i.e., pure gaseous inclusions, pure liquid inclusions, gas-liquid inclusions, and gas-liquid inclusions containing solid minerals. These inclusions were broken open during the grinding process, and their compositions were released to the solution. The total concentration of Zn released from these inclusions reaches 18.35×10^-6 mol/L, which is much higher than that of Zn dissolved from the sphalerite itself （1.93×10^-6 mol/L） and the theoretical calculation value （2.73×10^-8 mol/L）.

DRAWING PREDOMINANCE DIAGRAM OF M_1—M_2—x—y SYSTEM AND ITS APPLICATION

Discussions were made of the principle,method and computer program for drawing the pre- dominance diagrams of the bi-metal co-existed system M_1-M_2-x-y in which the multi-me- tallic compounds may be produced by interaction between compounds of both metals.The formation of zinc ferrite and its stable region have been analyzed through drawing Zn-Fe-S-O system predominance diagrams.The availability of the diagram is given the di- rection to roast the zinc sulfide ore as well.

The Origin of Pb-Zn Deposits in the Northern Kuandian Area, Liaoning Province

Carbonates and clastic rocks are well developed in the second-order basins of an Paleoproterozoic aulacogen in the northern Kuandian area, Liaoning Province. The carbonates cousist of two parts, the upper and the lower carbonate forma- tions. The clastic rocks occured between the two formations. Two Pb-Zn ore belts exist in both of upper and lower carbo- nate formations and are called B and A-belt respectively. Several tens of Pb-Zn ore bodies are found in A-belt. Some Pb -Zn ore bodies are apparent in vertical zoning in a sequence of Fe-Zn-Pb-Ba from the lower to the upper. Geological and geochemical researches show that the ore components in the A-belt was exhalated from the liquid source bed deeply and was precipitated in a closed second-order basins. While those in the B-belt was derived from the upper crust and was de- opsited in a normal oceanic enviornment. The second-order basins in Liaodong-Ji’nan-North Korean Peninsular aulaco- gen at the margin of the Archean craton are promising sites for looking for the deposits formed by exhalation of the liquid source bed deeply under crust.

Disposal of zinc extraction residues via iron ore sintering process:an innovative resource utilization

Zinc extraction residue,a solid waste generated from the treatment of zinc-containing dust in rotary kilns,is commonly stockpiled in steel companies for extended periods.It poses significant disposal challenges and environmental pollution risks.So far,research on the treatment of zinc extraction residues has been slow,inadequate,and sporadic.For this gap,a novel approach was proposed to effectively treat the zinc extraction residue via the iron ore sintering process.It was feasible to add 1 wt.%of zinc extraction residues to the sintering raw materials.The more adequate mineralization reaction resulted in higher yield and tumbler indexes,despite a slight decrease in sintering speed.Although this may result in a slight decrease in sintering speed,the more complete mineralization reaction leads to improved sintering yield and tumbler index.Interestingly,the addition of zinc extraction residues reduced the CO and NO_(x) concentrations in the sintering flue gas.Thus,the iron ore sintering process provided a viable solution for resource utilization and environmentally friendly treatment of zinc extraction residues.