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Kinetics and mechanism of sphalerite leaching by sodium nitrate in sulphuric acid solution  [PDF]
Soki? M.,Markovi? B.,Matkovi? V.,?ivkovi? D.
Journal of Mining and Metallurgy, Section B : Metallurgy , 2012, DOI: 10.2298/jmmb111130022s
Abstract: Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time on the leaching degree of zinc were investigated and kinetic analysis of the process was accomplished. With temperature increasing from 60 to 90°C, the zinc leaching increased from 25.23% to 71.66% after 2 hours, i.e. from 59.40% to 99.83% after 4 hours. The selected kinetic model indicated that the diffusion through the product layer was the rate-controlling step during the sphalerite leaching. The activation energy was determined to be 55 kJ/mol in the temperature range 60-90°C. XRD, light microscopy and SEM/EDX analyses of the complex concentrate and leach residue confirmed formation of elemental sulphur and diffusion-controlled leaching mechanism.
Potential use of a chemical leaching reject from a kaolin industry as agricultural fertilizer
Ribeiro, Fabiana Rodrigues;Egreja Filho, Fernando Barboza;Fabris, José Domingos;Mussel, Wagner da Nova;Novais, Roberto Ferreira;
Revista Brasileira de Ciência do Solo , 2007, DOI: 10.1590/S0100-06832007000500011
Abstract: the industrial refining of kaolin involves the removal of iron oxides and hydroxides along with other impurities that cause discoloration of the final product and depreciate its commercial value, particularly undesirable if destined to the paper industry. the chemical leaching in the industrial processing requires treatments with sodium hyposulfite, metallic zinc, or sulfuric and phosphoric acids, in order to reduce, dissolve and remove ferruginous compounds. to mitigate the environmental impact, the acidic effluent from the leaching process must be neutralized, usually with calcium oxide. the resulting solid residue contains phosphorous, zinc, and calcium, among other essential nutrients for plant growth, suggesting its use as a macro and micronutrient source. samples of such a solid industrial residue were used here to evaluate their potential as soil fertilizer in an incubation greenhouse experiment with two soil samples (clayey and medium-textured). the small ph shift generated by applying the residue to the soil was not a limiting factor for its use in agriculture. the evolution of the concentrations of exchangeable calcium, and phosphorous and zinc extractability by mehlich-1 extractant during the incubation period confirms the potential use of this industrial residue as agricultural fertilizer.
Study on indium leaching from mechanically activated hard zinc residue  [PDF]
Yao J.H.,Li X.H.,Li Y.W.
Journal of Mining and Metallurgy, Section B : Metallurgy , 2011, DOI: 10.2298/jmmb1101063y
Abstract: In this study, changes in physicochemical properties and leachability of indium from mechanically activated hard zinc residue by planetary mill were investigated. The results showed that mechanical activation increased specific surface area, reaction activity of hard zinc residue, and decreased its particle size, which had a positive effect on indium extraction from hard zinc residue in hydrochloric acid solution. Kinetics of indium leaching from unmilled and activated hard zinc residue were also investigated, respectively. It was found that temperature had an obvious effect on indium leaching rate. Two different kinetic models corresponding to reactions which are diffusion controlled, [1-(1- x)1/3]2=kt and (1-2x/3)-(1-x)2/3=kt were used to describe the kinetics of indium leaching from unmilled sample and activated sample, respectively. Their activation energies were determined to be 17.89 kJ/mol (umilled) and 11.65 kJ/mol (activated) within the temperature range of 30°C to 90°C, which is characteristic for a diffusion controlled process. The values of activation energy demonstrated that the leaching reaction of indium became less sensitive to temperature after hard zinc residue mechanically activated by planetary mill.
Leaching behavior of zinc and copper from zinc refinery residue and filtration performance of pulp under the hydrothermal process  [PDF]
Lei Cao,Ya-long Liao,Gong-chu Shi,Yu Zhang,Mu-yuan Guo
- , 2019, DOI: https://doi.org/10.1007/s12613-019-1706-z
Abstract: This study aims to investigate the leaching behavior and filtration performance of zinc refinery residue under hydrothermal conditions. The relationships between the structure and morphology of silicon in the leaching residue and the pulp filtration performance were explored by determining the pulp filtration speed, analyzing quantitatively the silicon content in the leachate, and characterizing the leaching residue structure. The results show that hydrothermal leaching induces the coagulation–hydrolysis of the silicon in solution, consequently altering the microstructure of the leaching residue, and that silicon oxygen tetrahedra ([SiO4]4?) form the main skeleton structure of the residue. The results obtained also show that the leaching rates of zinc and copper are 98.1% and 98.7%, respectively, and that the filtration speed is 526.32 L/(m2·h) under the conditions of sulfuric acid concentration of 140 g/L, leaching temperature of 160°C, leaching time of 3.0 h, oxygen partial pressure of 0.75 MPa, stirring speed of 600 r/min, and a liquid-to-solid ratio of 10 mL/g.
Leaching Characteristics of Heavy Metals in MSW Fly Ash Under Different Condition

YAN Jian-hu,LI Jian-xin,CHI Yong,NI Ming-jiang,CEN Ke-fa,

环境科学 , 2004,
Abstract: The leaching characteristic of heavy metals in MSW fly ash was studied under acidic and alkaline condition. The result showed the leaching characteristic of Pb, Zn, Ni, Cr and Hg had similar law, which was these heavy metals could leach out under acidic condition and alkaline condition(pH>12), and the leaching amount increased with the leachate density or L/S increasing. For example, under acidic and alkaline condition, the leaching amount of Pb increased from 0.457 mg/kg, 51.142 mg/kg to 104.576 mg/kg, 59.692 mg/kg respectively when L/S increased from 20 to 40 Cd and Cu could leaching out only under acidic condition. Under acidic condition the leaching rate of Cd, Pb and Zn were higher then the others.
Alkaline leaching of metal melting industry wastes dseparation of zinc and lead in the leach solution
环境科学学报(英文版) , 2000,
Abstract: In this work, a thorough examinations on the extractability of zinc and lead present in the steelmaking dusts using alkaline leaching process and the effectiveness of the zinc and lead separation in the resultant leaching solutions using sulfide precipitation method were made. It was found that only about 53% of zinc and over 70% of the lead could be leached out of the dusts, while the other 47% of zinc and 306 of lead were left in the leaching residues. The zinc and lead in the resultant leaching solution can be effectively and selectively separated. When the weight ratio of sodium sulfide (M. W. = 222-240) to Pb was kept at 1.8, the lead in the solution could be precipitated out quantitatively while all the zinc was remained in the solution. The zinc left in the solution can be further recovered by the addition of extra sodium sulfide with a weight ratio of sodium sulfide to the zinc over 2.6. The resultant filtrate can be recycled to the leaching of dust in the next leaching process.
An Expert Control and Fault Diagnosis Scheme for the Leaching Zinc Process

WU Min,GUI Wei-hua,
吴 敏

控制理论与应用 , 2001,
Abstract: This paper proposes an expert control and fault diagnosis scheme for the leaching zinc process, which concerns determining and tracking the optimal pHs of the leach overflows, and ensuring the safe running of the process. A real world application of this scheme shows that it not only improves the control performance but also correctly diagnoses faults.
Leaching Kinetics of As, Mo, and Se from Acidic Coal Fly Ash Samples  [PDF]
Ghanashyam Neupane, Rona J. Donahoe, Siddhartha Bhattacharyya, Prakash Dhakal
Journal of Water Resource and Protection (JWARP) , 2017, DOI: 10.4236/jwarp.2017.98060
Abstract: Annually, coal-fired electric power plants produce large volumes of potentially hazardous coal combustion products (CCPs) including fly ash. Since majority of the coal fly ash and other CCPs deposited in dry land fills or wet lagoons, they pose risk of contamination to local environment. In this study, we present results of leaching kinetics for As, Mo, and Se from three acidic fly ash samples collected from coal-fired power plants in the southeastern United States. This study shows that the leachate concentrations of As, Mo, and Se increase over time. Three kinetics equations, pseudo-second order, Elovich, and power-function, are able to adequately describe the experimental leaching kinetics data. Experimental leaching data and modeling results indicate that the rate limiting leaching of As, Mo, and Se is controlled by the diffusional process responsible for transferring these elements from interior to the surface of the particles as well as the dissolution of the fly ash particles. Therefore, it is important to adopt effective containment/treatment schemes to avoid potential and persistent dispersion of trace elements from ash disposal facilities to surrounding environment for a long time.
Ultrasound effects on zinc recovery from EAF dust by sulfuric acid leaching  [PDF]
K. Brunelli,M. Dabalà
- , 2015, DOI: https://doi.org/10.1007/s12613-015-1080-4
Abstract: In this work, an ultrasound-assisted leaching process was studied for the recovery of zinc from electric arc furnace (EAF) dust, in which zinc was mainly present in the form of franklinite (60%). Hydrometallurgy is emerging as a preferred process for the recovery of a variety of metals, and the use of ultrasound could offer advantages over the conventional leaching process, especially for the dissolution of franklinite. Franklinite is a refractory phase that is difficult to leach and represents the main obstacle in conventional hydrometallurgy processing. Atmospheric leaching with different sulfuric acid concentrations (0.2–2.0 M) at two temperatures (323 and 353 K) was performed. The tests were conducted using both conventional and ultrasound-assisted leaching. After the leaching tests, the solid residues were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques, whereas the leach liquor was analyzed by inductively coupled plasma spectroscopy (ICP). The use of ultrasound facilitated the dissolution of franklinite at low acid concentrations and resulted in a greater zinc recovery under all of the investigated operating conditions.
Deep cleaning of a metallurgical zinc leaching residue and recovery of valuable metals  [PDF]
Peng Xing,Bao-zhong Ma,Peng Zeng,Cheng-yan Wang,Ling Wang,Yong-lu Zhang,Yong-qiang Chen,Shuo Wang,Qiu-yin Wang
- , 2017, DOI: https://doi.org/10.1007/s12613-017-1514-2
Abstract: Huge quantities of zinc leaching residues (ZLRs) generated from zinc production are dumped continuously around the world and pose a potential environmental threat because of their considerable amounts of entrained heavy metals (mainly lead). Most ZLRs have not been properly treated and the valuable metals in them have not yet been effectively recovered. Herein, the deep cleaning of a ZLR and recovery of valuable metals via a hydrometallurgical route were investigated. The cleaning process consists of two essential stages: acid leaching followed by calcium chloride leaching. The optimum conditions for extracting zinc, copper, and indium by acid leaching were a sulfuric acid concentration of 200 g·L?1, a liquid/solid ratio of 4:1 (mL/g), a leaching time of 2 h, and a temperature of 90°C. For lead and silver extractions, the optimum conditions were a calcium chloride concentration of 400 g·L?1, a pH value of 1.0, a leaching time of 1 h, and a temperature of 30°C. After calcium chloride leaching, silver and lead were extracted out and the lead was finally recovered as electrolytic lead by electrowinning. The anglesite phase, which poses the greatest potential environmental hazard, was removed from the ZLR after deep cleaning, thus reducing the cost of environmental management of ZLRs. The treatment of chlorine and spent electrolyte generated in the process was discussed.
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