Zinc Leaching Residue Research Articles

Stepwise bioleaching of Cu-Zn mixed ores with comprehensive utilization of silver-bearing solid waste through a new technique process

In this work, a new technique process for processing Cu-Zn mixed ores containing chalcopyrite and marmatite was proposed to avoid the complex Cu-Zn flotation and extraction separation processes, as well as for the comprehensive utilization of abandoned silver-containing zinc leaching residue (ZLR). In the first step, stepwise bioleaching of Cu-Zn mixed ores in the presence of mixed moderately thermophilic microorganisms and Fe3+ was conducted for recovering Zn from marmatite. Copper was then efficiently extracted from the copper-containing bioleaching residues through catalytic bioleaching by using ZLR as catalyst. The final bioleaching residues were subsequently leached by thiourea for recovering Ag efficiently. The provided technique process accomplished the stepwise dissolution of Cu-Zn mixed ores and the comprehensive utilization of silver-bearing ZLR. The intermediate species, the electrochemical dissolution process and the electrochemical interactions between chalcopyrite and marmatite were also discussed to interpret the detailed mechanisms of stepwise bioleaching.

Recovery of valuable metals from zinc leaching residue by sulfate roasting and water leaching

Zinc leaching residue (ZLR), produced from traditional zinc hydrometallurgy process, is not only a hazardous waste but also a potential valuable solid. The combination of sulfate roasting and water leaching was employed to recover the valuable metals from ZLR. The ZLR was initially roasted with ferric sulfate at 640 °C for 1 h with ferric sulfate/zinc ferrite mole ratio of 1.2. In this process, the valuable metals were efficiently transformed into water soluble sulfate, while iron remains as ferric oxide. Thereafter, water leaching was conducted to extract the valuable metals sulfate for recovery. The recovery rates of zinc, manganese, copper, cadmium and iron were 92.4%, 93.3%, 99.3%, 91.4% and 1.1%, respectively. A leaching toxicity test for ZLR was performed after water leaching. The results indicated that the final residue was effectively detoxified and all of the heavy metal leaching concentrations were under the allowable limit.

A comprehensive utilization of silver-bearing solid wastes in chalcopyrite bioleaching

In this work, two types of abandoned silver-bearing solid wastes of zinc leaching residue (ZLR) and firebrick were used as silver catalysis in chalcopyrite bioleaching by mixed moderately thermophilic culture. Bioleaching results showed that the chosen ZLR and waste firebrick both remarkably promoted chalcopyrite bioleaching, and chalcopyrite was not passivated at high redox potential (more than 600mV vs. Ag/AgCl) in the presence of silver-bearing solid wastes. The bioleaching residues were subsequently leached by thiourea to recover silver. Results indicated that silver was more easily to be extracted from bioleaching residues than from untreated silver-bearing solid wastes, and high silver recovery of about 90% can be finally achieved. Hence, this work is potentially useful to provide a promising technique for promoting chalcopyrite bioleaching and for comprehensive utilization of silver-bearing solid wastes.

Germanium separation and purification by leaching and precipitation

In this research work, extraction and purification of germanium from zinc leach residues (ZLR) were investigated. The results of ICP, XRF, and atomic adsorption spectroscopy (AAS) tests show that contents of germanium, iron, lead, and zinc within the leaching residue were 105×10−6, 3.53%, 10.35%, and 8.8%, respectively. XRD results indicate that the main minerals were in different forms of sulfates (CaSO4·2H2O, PbSO4 and ZnSO4·6H2O), silicate (SiO2), and oxide (Fe2O3). Dissolution of leaching filter cake was carried out using 5 parameters and each in 4 levels (acid concentration, temperature, time, liquid-to-solid ratio, and stirring speed) by Taguchi method (L16), and then optimization of the effective parameters by response surface method. Under optimum conditions, zinc and germanium dissolution efficiencies were 88.71% and 8%, respectively. Leaching tests with sulfuric acid (added di-ammonium oxalate monohydrate) and hydrochloric acid (HCl) on the residues obtained from previous-stage sulfuric acid dissolution, yielded germanium and iron recoveries of 83%, 88%, 40%, and 90%, respectively. Thus, leaching experiment with sulfuric acid (added di-ammonium oxalate monohydrate) was superior to that with hydrochloric acid due to high and low extraction amounts of germanium and iron, respectively. Precipitation experiments revealed that germanium purification with tannic acid presented a better result compared to sodium hydroxide and ammonia. Under optimum conditions, contents of germanium and iron in the solution after precipitation were 0.1505% and 14.7% with precipitation yields of 91% and 52%, respectively.

An innovative technology for recovery of zinc, lead and silver from zinc leaching residue

Zinc leaching residue is a good source of zinc and has a great potential to be utilized. However, it is very difficult to recover lead, zinc and silver from the residue by traditional technologies. In this study, a new technology based on conversions of PbSO4 and ZnSO4 in the residue to their respective sulfides by reduction roasting with coal powder followed by a flotation treatment was developed. The effects of roasting temperature, coal dosage, reaction time and pyrite dosage were investigated at a laboratory scale. The results showed that the conversion extent of PbSO4 and ZnSO4 under the optimal experimental conditions was 71.89 and 69.76%, respectively. A flotation concentrate containing 39.13% Zn, 6.93% Pb and 973.54 g/Mg Ag was obtained from the treated material, and the recovery of Zn, Pb and Ag was 48.38, 68.23 and 77.41%, respectively. The tailing containing ZnFe2O4 or Fe3O4 could be either stockpiled or further disposed.

Study on separating of zinc and iron from zinc leaching residues by roasting with ammonium sulphate

The hydrometallurgical processes for zinc recycling from zinc leaching residues (ZLR) generate a huge volume of iron residues. Iron residues lead to serious losses of metal value and secondary pollution. Efficient separation of zinc and iron is an ideal idea for avoiding iron residues by control zinc and iron phase from ZLR. In this study, a novel process for separating zinc and iron present in ZLR is developed consisting of sulfates roasting and selective leaching. The extraction of zinc increased to 92.63% while iron decreased to 2.04%. Zinc was leached efficiently from ZLR for comprehensive recovery with iron concentration of zinc enriched leachate below 0.38g/L, so that the effective separation of zinc and iron was achieved. The iron content from this new process was increased higher than 45% for a potential use as an iron-making material after the removing of lead, zinc and cadmium from the leached residue. The iron removal process and iron residues could be avoided in the hydrometallurgical process.

Selective reduction process of zinc ferrite and its application in treatment of zinc leaching residues

The traditional zinc hydro-metallurgy generates a large amount of zinc ferrite residue rich in valuable metals. The separation of iron is crucial for resource recycling of valuable metals in zinc ferrite residue. A novel selective reduction roasting–leaching process was proposed to separate zinc and iron from zinc leaching residue which contains zinc ferrite. The thermodynamic analysis was employed to determine the predominant range of Fe3O4 and ZnO during reduction roasting process of zinc ferrite. Based on the result of thermodynamic calculation, we found that V(CO)/V(CO+CO2) ratio is a key factor determining the phase composition in the reduction roasting product of zinc ferrite. In the range of V(CO)/V(CO+CO2) ratio between 2.68% and 36.18%, zinc ferrite is preferentially decomposed into Fe3O4 and ZnO. Based on thermogravimetric (TG) analysis, the optimal conditions for reduction roasting of zinc ferrite are determined as follows: temperature 700–750 °C, volume fraction of CO 6% and V(CO)/V(CO+CO2) ratio 30%. Based on the above results, zinc leaching residue rich in zinc ferrite was roasted and the roasted product was leached by acid solution. It is found that zinc extraction rate in zinc leaching residue reaches up to 70% and iron extraction rate is only 18.4%. The result indicates that zinc and iron can be effectively separated from zinc leaching residue.

Leaching of lead from zinc leach residue in acidic calcium chloride aqueous solution

A process with potentially reduced environmental impacts and occupational hazards of lead-bearing zinc plant residue was studied to achieve a higher recovery of lead via a cost-effective and environmentally friendly process. This paper describes an optimization study on the leaching of lead from zinc leach residue using acidic calcium chloride aqueous solution. Six main process conditions, i.e., the solution pH value, stirring rate, concentration of CaCl2 aqueous solution, liquid-to-solid (L/S) ratio, leaching temperature, and leaching time, were investigated. The microstructure and components of the residue and tailing were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). On the basis of experimental results, the optimum reaction conditions were determined to be a solution pH value of 1, a stirring rate of 500 r·min−1, a CaCl2 aqueous solution concentration of 400 g·L−1, a liquid-to-solid mass ratio of 7:1, a leaching temperature of 80°C, and a leaching time of 45 min. The leaching rate of lead under these conditions reached 93.79%, with an iron dissolution rate of 19.28%. Silica did not take part in the chemical reaction during the leaching process and was accumulated in the residue.

Global Substance Flow Analysis of Gallium, Germanium, and Indium: Quantification of Extraction, Uses, and Dissipative Losses within their Anthropogenic Cycles

SummaryThis study provides a global substance flow analysis for gallium (Ga), germanium (Ge), and indium (In) for 2011, quantifying the amount of metal lost during extraction, beneficiation/smelting/refining, manufacturing of intermediate products, and the amount embodied in end‐use products. Thus far, studies illustrating their cradle to end‐use life cycle on a global scale are either missing or outdated, and thus opportunities to increase their supply remain unknown and/or not quantified. The results illustrate the losses and inefficiencies stages, thereby identifying potential additional supply by process improvement, recovery, and recycling. Results show that there are significant opportunities to meet future demand of Ga and Ge by concentrating recovery efforts in the extraction and beneficiation/smelting/refining stages. Further, 1.4% Ga, 0.7% Ge, and 54% In of the theoretical available amount in the attractor ores are extracted to meet the primary refined demand in 2011. Of the 9,065 tonnes (t) of Ga embodied in the Bayer liquor (from aluminum production), only 263 t are refined. This is owing to low capacities of Ga refining, combined with a refining efficiency of 60%. Ge presents a similar case for the same reasons, in which only 43 t of Ge of the 7,636 t of Ge available from zinc leach residue are refined. Meeting future In demand, on the other hand, will require greater efforts in increasing end‐of‐life recycling. Process efficiencies for Ga (46%), Ge (56%), and In (78%) demonstrate further potential. We quantify the flows into use by distinguishing among dissipative and nondissipative end uses, as well as the recyclable fraction for each metal for 2011.

Cleaning of high lead-bearing zinc leaching residue by recovery of lead with alkaline leaching

In the hydrometallurgical zinc production processes, huge quantities of solid leaching residues containing different metallic compounds threat the environment are continuously generated around the world. Due to increasing demand of metals and the depletion of high grade natural resources, these types of wastes are gaining great importance in the metallurgical industries. In this study, cleaning of zinc leaching residue, containing 19% Pb in the form of anglesite, by recovering of lead with alkaline leaching was investigated. For this purpose; the effects of NaOH concentration, leaching time and temperature on the Pb recovery from the residue were studied. Under the optimum conditions using NaOH concentration of 11%, L/S ratio of 5, temperature of 100°C, and leaching time of 60min, the leaching ratio of Pb reached up to 99.6%. Kinetic analysis of the experimental data showed that the leaching was ash layer diffusion controlled with activation energy of 2.78kJ/mol. Pb could be effectively separated from the pregnant leach solution with chemical precipitation by Na2S and CO2. TCLP and EU Directive EC/2003/33 tests applied to the remaining leach residue showed that it was environmentally stable and non-hazardous waste, respectively.

Leaching and recovery of zinc from leaching residue of zinc calcine based on membrane filter press

The feasibility of leaching and recovery of zinc from zinc leaching residue (ZLR) based on a membrane filter press (MFP) was investigated. Experimental results show that zinc calcines with particle sizes of less than 106 μm and chambers of widths of 30 mm are appropriate for establishing uniform filter cakes to obtain acceptable leaching and recovery results. The leaching of zinc from ZLR performed via washing at 90 to 96 °C for 90 min with spent electrolyte using a MFP results in a zinc extraction rate of 97%, and almost all of the zinc leached are recovered after water washing with MFP, thereby avoiding any loss in the ZLR. Compared with the traditional hot concentrated acid leaching process, the process based on MFP as a leaching reactor is able not only to ensure a high extraction rate but also to reduce the leaching time. Moreover, the thickening, pulping, second leaching, washing, filtering and pressing could be integrated and realized using a single MFP.

Selective reduction of PbSO4 to PbS with carbon and flotation treatment of synthetic galena

In order to recover lead from the zinc leaching residues, a new technology involving selective reduction of lead sulfate to lead sulfide with carbon followed by flotation was investigated. The reduction thermodynamics of PbSO4 was discussed and the effects of molar ratio of C to PbSO4, reaction temperature and time were examined by thermogravimetry (TG) and XRD. Verification tests were further carried out to prove the conclusions of thermodynamic and TG analyses, and the transformation extent could reach 86.45% under the optimal roasting conditions. The prepared galena was then subjected to micro-flotation tests, and the highest lead recovery could reach up to 75.32%.

Factors on Leaching Zinc and Copper from Zinc Leach Residue

It is found that cuprous sulfite, zinc sulfate and zinc sulfide were the main phases of copper and zinc in zinc leach residue, through analyzing its composition and phase characteristics by XRF and XRD. The method that cooperate sulfuric acid leaching with oxidant was chosen. 60 g/L H2SO4 at 60 °C for 2 h with 4% KMnO4 and liquid/solid ratio of 5..1, 84.29 % of Cu and 92.02 % of Zn are extracted. The ion concentration of copper and zinc are tested by UV-VIS spectrophotometer and EDTA titration respectively. The results show that the amount of acid is sufficient for leaching at the condition of 60 g/L H2SO4 and liquid/solid ratio of 5..1. At the same time, copper change from low valence into high valence after adding KMnO4 which strengthen the leaching, and the chemical reaction can reach balance at 60 °C for 2 h. This method has good extraction effect on copper and zinc.

Sulfidation of heavy-metal-containing neutralization sludge using zinc leaching residue as the sulfur source for metal recovery and stabilization

Heavy-metal-containing neutralization sludge (NS) and sulfur-containing zinc leaching residue (ZLR), both of which are difficult to dispose of, are two of the main solid wastes produced in the Pb/Zn smelting process. This study focused on the application of ZLR as a sulfur source to sulfidize NS, which could then be separated by flotation for metal recovery. A mixture of NS, ZLR and additional sulfur was first mixed by ball milling, and then successively treated by hydrothermal sulfidation and flotation. Based on the chemical properties of NS and ZLR, the effects of the mass ratio of NS-to-ZLR, the amount of sulfur and ball milling time on sulfidation and the floatability and stability of the sulfidation product were investigated. The sulfidation percentages of Zn and Pb were as high as 82.6% and 95.6%, respectively. Flotation tests revealed that Zn and Pb can be enriched with a concentrate grade of 21.3% Zn and 3.4% Pb. Toxicity characteristic leaching procedure (TCLP) results indicated that stabilization of NS and ZLR occurred after sulfidation.

Reduction roasting of high iron bearing zinc calcine for recovery of zinc and iron

High iron bearing zinc sulphide ore is an important resource for zinc, and the reserve is very great in the world. It is very difficult to effectively obtain zinc and iron from the source by traditional technology. In this study, a novel method was proposed for recovery of zinc and iron from high iron bearing zinc calcine, and the key procedure, reduction roasting, was investigated. The effects of CO concentration, CO2 concentration, temperature and time on reduction roasting were studied respectively. The experimental results show that the content of soluble zinc and magnetic susceptibility reached 91·15% and 4·1×10−4 m3 kg−1 under the optimum conditions respectively. About 90%Zn and 9·5%Fe were dissolved from the reduction roasted zinc calcine by low acid leaching, and simultaneously, 84·3%Fe was recycled to the iron concentrate containing iron of 53·2% from zinc leaching residue by low intensity magnetic separation.Le minerai de sulfure de zinc à haute teneur en fer est une ressource importante du zinc et il en existe une grande quantité dans le monde. Il est très difficile d’obtenir efficacement le zinc et le fer de cette source par la technologie traditionnelle. Dans cette étude, on propose une nouvelle méthode pour la récupération du zinc et du fer à partir de produit calciné de zinc à haute teneur en fer, et on examine la procédure clef, le grillage réducteur. On a étudié respectivement les effets de la concentration de CO, de la concentration de CO2, de la température et de la durée sur le grillage réducteur. Les résultats expérimentaux montrent que la teneur en zinc soluble et la susceptibilité magnétique atteignaient respectivement 91·15% et 4·1×10−4 m3 kg−1 en conditions optimales. Environ 90% du Zn et 9·5% du Fe étaient dissous à partir du produit calciné de zinc de grillage réducteur par lessivage à acide faible, et simultanément, 84·3% du Fe était recyclé en concentré de fer contenant 53·2% de fer à partir du résidu de lessivage du zinc par séparation magnétique à faible intensité.

A novel method to recover zinc and iron from zinc leaching residue

A novel method to recover zinc and iron from zinc leaching residue (ZLR) by the combination of reduction roasting, acid leaching and magnetic separation was proposed. Zinc ferrite in the ZLR was selectively transformed to ZnO and Fe3O4 under CO, CO2 and Ar atmosphere. Subsequently, acid leaching was carried out to dissolve zinc from reduced ZLR while iron was left in the residue and recovered by magnetic separation. The mineralogical changes of ZLR during the processes were characterized by XRF, TG, XRD, SEM–EDS and VSM. The effects of roasting and leaching conditions were investigated with the optimum conditions obtained as follows: roasted at 750°C for 90min with 8% CO and CO/CO+CO2 ratio at 30%; leached at 35°C for 60min with 90g/l sulfuric acid and liquid to solid ratio at 10:1. The iron was recovered by magnetic separation with magnetic intensity at 1160G for 20min. Under the optimum operation, 61.38% of zinc was recovered and 80.9% of iron recovery was achieved. This novel method not only realized the simultaneous recovery of zinc and iron but also solved the environmental problem caused by the storage of massive ZLR.

Kinetic Analysis of Isothermal Decomposition Process of Zinc Leach Residue in an Inert Atmosphere. The Estimation of the Apparent Activation Energy Distribution

Thermal decomposition of zinc leach residue has been studied in a tubular furnace under a constant nitrogen gas flowing, at four different operating temperatures (600°C, 750°C, 950°C, and 1150°C). Using a detailed kinetic analysis, it was shown that the investigated process can be described by a two-parameter autocatalytic Šesták–Berggren reaction model. It was noted that the apparent activation energy values Ea increase progressively with a degree of conversion, accompanied by the appearance of a convex Arrhenius dependence. This behavior is a characteristic of a system of parallel competing reactions. It was concluded that the investigated isothermal decomposition process is characterized by unusually very low preexponential factor and low values of the apparent activation energy. Based on the derived density distribution function of Ea values, it was concluded that the isothermal decomposition process probably occurs through four reaction steps, where each step is characterized by one parallel reaction.

Recovery of zinc and other valuable metals from zinc leach residue by top blowing fuming method

In this paper, comprehensive utilisation of hydrometallurgy zinc residue, goethite especially, was proposed. The raw material used in this study was mixed residue while the mass ratio of goethite and lead–silver residue was fixed at 4∶1. Based on the characters of mixed residue, the top blowing fuming method was taken by using induction furnace. The effects of parameters such as CaO/SiO2 (0·61–0·91), C/feed mass ratio (18–26%) and reduction time (20–60 min) had been studied. Under the optimum conditions (CaO/SiO2 = 0·71; C/feed mass ratio of 24%; reduction time of 50 min), the average fuming efficiency of zinc, lead and sliver in the mixed residue could reach up to 97·2, 98·1 and 82% respectively.

A STUDY ON HEAVY METALS MOBILITY FROM ZINC PLANT RESIDUES IN IRAN

The transport of heavy metals from mining disposal site to groundwater and surface water is one of the most serious environmental problems in the world. The transport of heavy metals such as Zn, Cd and Mn from leaching filter cake in RECo, Zanjan, Iran was examined by using column leaching. Parameters studied included: flow rate, pH of input solution and leaching time. In this study, the maxi- mum dissolution percents of Zn, Cd and Mn in input solution pH of 5 were 45.50 %, 53.97% and 19.94%, respectively. To statistically analysis the experimental results, SPSS14 software was employed. The results of SPSS 14 indicated that for the Zn, Cd and Mn dissolution, time and flow rate were found re- spectively, the effective parameters for the pollution in zinc leach residues.

Technological mineralogy and environmental activity of zinc leaching residue from zinc hydrometallurgical process

Chemical, physical, structural and morphological properties of zinc leaching residue were examined by the combination of various detection means such as AAS, XRF, XRD, Mössbauer spectrometry, SEM-EDS, TG-DSC, XPS and FTIR. The toxicity characteristic leaching procedure (TCLP) was used to investigate the environmental activity of zinc leaching residue for a short contact time. The phase composition analysis indicated that the zinc leaching residue mainly consists of super refined flocculent particles including zinc ferrite, sulfate and silicate. The physical structural analysis showed that it has a thermal instability and strong water absorption properties. The results of TCLP indicated that the amounts of Zn and Cd in the leaching solution exceed 40 and 90 times of limit, respectively, which demonstrate that this residue is unstable in weak acidic environment for a short contact time.