Hydrometallurgical Extraction Of Zinc Research Articles

Enhanced removal of organic matter from oxygen-pressure leaching solution by modified anode slime

Organic matter has become a typical harmful impurity, posing a serious problem and catastrophic effects in the hydrometallurgical extraction of zinc. The highly efficient and inexpensive method for the removal of organics from the leaching solution is of great practical significance for the efficient operation of zinc hydrometallurgy. For this reason, the removal of organic matter from oxygen-pressure leaching solution using modified anode slime was investigated by TOC analysis, FTIR spectroscopy, XRD, GCMS, and other characterization methods, and its mechanism was also discussed. The results show that the removal of organic matter using anode slime modified with sulfuric acid was significantly improved, and the removal of TOC reached 57.83% for anode slime modified at a temperature of 80 °C with a ratio of sulfuric acid to anode slime of 14 mL/100 g, which was more than 2.7 times that of untreated anode slime. The good removal effect of organic matter using the modified anode slime could be attributed to the transformation of inert α-MnO2 to active MnOOH by concentrated sulfuric acid-mediated modification. It was also found that the acid–solid ratio and temperature exhibited a significant effect on the modification of anode slime. The XPS analysis results of Mn 2p, Mn 3s, and O 1s, combined with the XRD patterns of the modified products indicated that the modification of anode slime led to the conversion of MnO2 in anode slime to MnOOH in the presence of H2SO4. However, MnO2 was further converted into high crystallinity MnOOH, even MnSO4 when the temperature exceeded 80 °C or the acid–solid ratio exceeded 18 mL/100 g, resulting in the decreased degradation performance for organic matter. The characterization results of FTIR spectroscopy and GCMS show that modified anode slime does not exhibit a degradation effect on all types of organic substances in leaching solution; however, it is very effective for some alcohols, olefins, and esters.

The Effectiveness of Zn Leaching from EAFD Using Caustic Soda

Electric arc furnace dust (EAFD) is a toxic waste which is mainly rich in iron oxide, zinc, and lead. Hydrometallurgical extraction of zinc from Jordanian EAFD in alkaline medium was investigated; NaOH, NaHCO3, and Na2CO3 were used as leaching agents. The pH values for the prepared solutions were 8.3, 8.2, and 12.55 for NaHCO3, Na2CO3, and NaOH, respectively. The effect of NaOH concentration (1, 3, 5, 7, and 9 M), contact time (5 min to 3 h), temperature (20, 40, and 60), and solid-to-liquid ratio (SLR; 20, 40, 80, and 120 mg/ml) on the leachability of zinc from EAFD were tested. The initial EAFD and the resulting leach residues were characterized using X-ray diffraction (XRD) and X-ray fluorescence (XRF). EAFD contained 25.9% Zn, 18.0% Fe, and 3.2% Pb. A maximum zinc recovery of 92.9% was achieved using 6 M NaOH at 60 °C with solid loading of 20 g/L and 3 h leaching time. NaHCO3 and Na2CO3 were not efficient leaching agents for Zn extraction since the recoveries were only 2.6 and 4.5%, respectively. Zn and Pb were depleted in the residues with an E-factor of 0.5–0.6 and 0.1–0.25, respectively. Iron was enriched in the residues; the E-factor was around 2. The EAFD contained mainly zincite, franklinite, and magnetite. After 3 h leaching, only traces of zincite exist in the residues, while sylvite and halite were completely dissolved.

Hydrometallurgical Extraction of Zinc and Iron from Electric Arc Furnace Dust (EAFD) using Hydrochloric Acid

Hydrometallurgical Extraction of Zinc and Iron from Electric Arc Furnace Dust (EAFD) using Hydrochloric Acid

Hydrometallurgical extraction of zinc from CaO treated EAF dust in ammonium chloride solution

Zinc in Electric Arc Furnace dust or EAF dust mainly exists as ZnFe2O4 and ZnO. While ZnO can be simply dissolved into either an acidic or alkaline solution, it is difficult to dissolve ZnFe2O4. In our previous work, we introduced a process called “CaO treatment”, a preliminary pyrometallurgical process designed to transform the ZnFe2O4 in the EAF dust into ZnO and Ca2Fe2O5. The halogens and others heavy metals were favorably vaporized during CaO treatment with no essential evaporation loss of zinc and iron, leaving CaO treated dust which consisted mainly of ZnO and Ca2Fe2O5 and no problematic ZnFe2O4 compound. In this work, the selective leaching of zinc over iron and calcium in the CaO treated dust was investigated using an NH4Cl solution. The effects of temperature, reaction time and NH4Cl concentration on dissolution behavior were examined. While most of the zinc in the CaO treated dust was extracted after 2h at 70°C with 2M NH4Cl, only about 20% of calcium was leached in NH4Cl solution. However, the iron did not dissolve and remained as Ca2Fe2O5 in residue. It was confirmed that zinc can be effectively recovered using NH4Cl solution.

Manganese recovery from secondary resources: A green process for carbothermal reduction and leaching of manganese bearing hazardous waste

During the hydrometallurgical extraction of zinc by electrowinning process, a hazardous solid waste called anode mud is generated. It contains large quantity of manganese oxides (55–80%) and lead dioxide (6–16%). Due to the presence of a large quantity of lead, the anode mud waste is considered hazardous and has to be disposed of in secure landfills, which is costly, wastes available manganese and valuable land resources. For recovery of manganese content of anode mud, a process comprising of carbothermal treatment using low density oil (LDO) followed by sulphuric acid leaching is developed.

Hydrometallurgical extraction of zinc from Jordanian electric arc furnace dust

Zinc was extracted in a Jordanian Steel Plant using an electric arc furnace dust. Sulfuric, nitric and hydrochloric acids were used at different concentrations to recover zinc from dust particles. The highest zinc extraction was obtained at low acid concentration of less than 1 mol/L in the order of H 2SO 4 followed by HNO 3 and then HCl. The kinetics of zinc extraction using H 2SO 4 showed a maximum zinc recovery of 72% obtained by using 0.1 mol/L acid concentration, 900 rpm agitation speed and 50 °C.

Zinc recovery from steel-making wastes by acid pressure leaching and hematite precipitation

Abstract The hydrometallurgical extraction of zinc from EAF dust and steel-making sludge was studied. These materials were treated with sulphuric acid at elevated pressure using microwave heating. More than 92% of zinc can be leached out using 0.3 M acid solution at 260 °C. Fe(II) remained in solution while most of the Fe(III) was precipitated as hematite. The iron concentration in the leach liquor decreased markedly when hydrogen peroxide solution was added at the start of the experiment. In this case, zinc extraction reached almost 99%. The hydrolytic precipitation of ferric sulphate was investigated at 200 °C for a low iron concentration. The reaction was found to be first-order with respect to Fe(III), and the apparent rate constant was 0.01 min − 1 .

Importance of roasted sulphide concentrates characterization in the hydrometallurgical extraction of zinc

The production of electrolytic zinc from sulphide ores consists mainly of four stages: roasting, acid leaching, purification and electrolysis. The roasting step plays an important role in zinc extraction due to the transformation from sulphide to oxide structure which provides more reactivity in presence of acid solutions. Incomplete particle roasting and presence of highly stable zinc ferrite (ZnFe 2O 4) formed in the pyrometallurgical step are the two major obstacles in the hydrometallurgical extraction of zinc. The objective of this study is to detect problems observed in an industrial electrolytic zinc circuit. For this purpose, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy (SEM/EDS) techniques were used to characterize sulphide and roasted concentrate samples. Microscopic investigations of cross-sectional particles revealed incomplete roasting in some particle sizes and the presence of ferrite clusters inside the roasted ores.

THE HYDROMETALLURGICAL EXTRACTION OF ZINC BY AMMONIUM CARBONATE: A REVIEW OF THE SCHNABEL PROCESS

The use of ammonium carbonate for the extraction of metals such as copper and nickel is well known. Less well known is the fact that ammonium carbonate extraction was used for the commercial recovery of zinc decades before its application to either copper or nickel. This article reviews the published data on the Schnabel Process (the hydrometallurgical extraction of zinc by ammonium carbonate) covering the period of 1880–2005.

Hydrometallurgical Extraction of Zinc and Copper – A 57Fe-Mössbauer and XRD Approach

The most commonly used route in the hydrometallurgical extraction of zinc and copper from a sulphide ore is the concentrate-roast-leach-electro winning process. In the present investigation a zinc-copper ore from the Maranda mine, located in the Murchison Greenstone Belt, South Africa, containing sphalerite (ZnS) and chalcopyrite (CuFeS2), was studied. The 57Fe-Mossbauer spectrum of the concentrate yielded pyrite, chalcopyrite and clinochlore, consistent with XRD data. Optimal roasting conditions were found to be 900°C for 3 h and the calcine produced contained according to X-ray diffractometry equal amounts of franklinite (ZnFe2O4) and zinc oxide (ZnO) and half the amount of willemite (Zn2SiO4). The Mossbauer spectrum showed predominantly franklinite (59%), hematite (6%) and other Zn- or Cu-depleted ferrites (35%). The latter could not be detected by XRD analyses as peak overlapping with other species occurred. Leaching was done with HCl, H2SO4 and HNO3, to determine which process would result in maximum recovery of Zn and Cu. More than 80% of both were recovered by using either one of the three techniques. From the residue of the leaching, the Fe-compounds were precipitated and <1% of the Zn and Cu was not recovered.

Hydrometallurgical extraction of zinc from zinc ferrites

The production of steel in electric arc furnaces (EAF) generates a by-product called EAF dusts. Due to the presence of significant amounts of leachable compounds of zinc, lead, cadmium, chromium and nickel, EAF dusts are classified as hazardous wastes. The quantity of EAF dust generated per year around the world represents a possible recovery of about 900 t of zinc. The major obstacle in the hydrometallurgical extraction and beneficial reuse of zinc is the presence of highly stable zinc ferrite ZnFe 2O 4. The amount of zinc in this form is about 50% of the total zinc. The objective of the process studied is to extract zinc from zinc ferrites contained in EAF dusts without destroying the iron oxide matrix, which can be recycled in the steel industry. The process is a hydrometallurgical treatment of waste based on the destruction of the ferrite structure. For this, ZnFe 2O 4 is treated by FeCl 3·6H 2O. The reaction consists of O 2−/Cl − exchange allowing the recovery of zinc as ZnCl 2 and iron as hematite αFe 2O 3. The separation of these products is obtained by aqueous leaching. In a first step, the process was studied on zinc ferrites synthesised in the laboratory, then extended to real samples. All the zinc is extracted after a 8 h treatment at 150 °C with a molar ratio FeCl 3·6H 2O/ZnFe 2O 4 of 10. The ultimate solid residues, which have been concentrated in iron, should be oriented towards the steel industry. The process has been also applied to roasted zinc concentrates containing zinc ferrite.