Reductive Acid Leaching Research Articles

Reductive acid leaching of cadmium from zinc neutral leaching residue using hydrazine sulfate

Zinc neutral leaching residue (ZNLR) from hydrometallurgical zinc smelting processing can be determined as hazardous intermediate containing considerable amounts of Cd and Zn which have great threats to the environment. The ZNLR contained approximately 35.99% Zn, 15.93% Fe and 0.26% Cd, and Cd mainly existed as ferrites in the ZNLR in this research. Reductive acid leaching of ZNLR was investigated. The effects of hydrazine sulfate concentration, initial sulfuric acid concentration, temperature, duration and liquid-to-solid ratio on the extraction of Cd, Zn and Fe were examined. The extraction efficiencies of Cd, Zn and Fe reached 90.81%, 95.83% and 94.19%, respectively when the leaching parameters were fixed as follows: hydrazine sulfate concentration, 33.3 g/L; sulfuric acid concentration, 80 g/L; temperature, 95 °C; duration of leaching, 120 min; liquid-to-solid ratio, 10 mL/g and agitation, 400 r/min. XRD and SEM-EDS analyses of the leaching residue confirmed that lead sulfate (PbSO4) and hydrazinium zinc sulfate((N2H5)2Zn(SO4)2) were the main phases remaining in the reductive leaching residue.

Kinetics of Reductive Acid Leaching of Cadmium-Bearing Zinc Ferrite Mixture Using Hydrazine Sulfate

The reductive acid leaching kinetics of synthetic cadmium-bearing zinc ferrite was investigated, and the influence of reaction temperature, sulfuric acid and hydrazine sulfate were studied. The results illustrated that an increase in the reaction temperature, initial sulfuric acid and hydrazine sulfate significantly enhanced the extraction efficiencies of cadmium, zinc and iron. The leaching kinetics were controlled by a surface chemical reaction based on a shrinking core model. The empirical equation 1 �ð 1 � XÞ 1=3 ¼ krt applied was found to fit well with the kinetics analysis; the leaching processes of cadmium, zinc and iron were similar and the activation energies were 79.9 kJ/mol, 77.9 kJ/mol and 79.7 kJ/mol, respectively. The apparent orders of cadmium-bearing zinc ferrite dissolution with respect to sulfuric acid concentration were 0.83, 0.83 and 0.84 for Cd, Zn and Fe, respectively.

Manganese extraction by reduction–acid leaching from low-grade manganese oxide ores using CaS as reductant

The extraction of manganese from low-grade manganese oxide ores using CaS derived from CaSO4 as reductant was investigated. The effects of mass ratio of CaS to ore, reduction temperature, reduction time, liquid to solid ratio (L/S ratio), stirring speed, leaching temperature, leaching time and H2SO4 concentration on the leaching rates of Mn and Fe during the reduction–acid leaching process were discussed. The leaching rates of 96.47% for Mn and 19.24% for Fe were obtained under the optimized conditions of mass ratio of CaS to manganese oxide ore 1:6.7, L/S ratio 5:1, stirring speed 300 r/min, reduction temperature of 95 °C for 2.0 h in the reduction process and leaching stirring speed of 200 r/min, H2SO4 concentration of 1.5 mol/L, leaching temperature of 80 °C for 5 min in the leaching process. In addition, this process can be employed in the recovery of manganese from various manganese oxide ores, and Mn leaching rate above 95% is obtained.

Enhanced recovery of nickel from chromite overburden (COB) using dissimilatory Fe (III) reducers: A novel Bio-Reduction Acid Leaching (BRAL) approach

The nickeliferous chromite overburden (COB) awaits a suitable technology to extract the obstinate nickel ingrained in its goethite matrix. In the present study, a novel Bio-Reduction Acid Leaching (BRAL) approach has been proposed using dissimilatory iron reducing bacteria (DIRB) which is inherently capable of transforming iron mineral phases via bio-reduction (BR). Mineralogical characterization of the bio-reduced COB using XRD and FTIR confirmed the phase transformation of goethite to hematite and magnetite with exposure of the nickel oxide peaks. Further, morphological characterization using FESEM vividly highlighted the changes of acicular goethite to granular magnetite deposits on the extra polymeric substance (a scaffold for electron transfer) secreted by DIRB consortium over the surface of COB. Further, enhanced nickel extraction was achieved with a reductive acid leaching (AL) approach with 6N sulfuric acid and 2% glucose (reducing agent) at 65°C for 6h. A cumulative of 83.6% nickel was achieved through this BRAL approach. The pregnant leach solution (PLS) generated as a result of the AL approach was subjected to a hydrometallurgical route to recover metallic nickel. Solvent extraction (SX) of the PLS was performed using 0.5M NaD2EHPA as extractant. The pregnant nickel-loaded electrolyte was subjected to electrowinning (EW) to recover metallic nickel of 99.6% purity. The process flow-sheet is believed to provide a suitable eco-friendly, potential method to efficiently extract nickel from low grade nickel laterites to meet the ever growing demands caused by depletion of high grade nickel sulfidic ores.

Preparation of Zn–Mn ferrite from spent Zn–Mn batteries using a novel multi-step process of bioleaching and co-precipitation and boiling reflux

Synthesis of wide-application Zn–Mn ferrite soft magnetic materials using spent Zn–Mn batteries as starting raw materials has attained growing attentions in recent years. The multi-step series processes of reductive acid leaching and oxidative co-precipitation and high temperature calcination or hydrothermal reaction were generally utilized to carry out the conversion. In this work, a novel multi-step process of bioleaching and co-precipitation at 30°C and boiling reflux at 100°C, which was characteristic of low cost, environmental friendliness and energy saving, was attempted to accomplish the conversion for the first time. The results showed that synthesis of Zn–Mn ferrite using bioleaching liquor as a precursor was feasible. NaOH was the best coprecipitator for manufacturing the soft magnetic material from bioleaching liquor compared with NaHCO3 and NH4HCO3. Higher pH value of the second co-precipitation at 13.0, higher total concentration of Mn2++Zn2++Fe2+ at 2.0mol/l and longer reflux time at 5h were essential for greater magnetization and better crystallinity. Under optimum conditions, this novel multi-step process harvested soft magnetic material with highest saturation magnetization of 102emu·g−1, offering an alternative to convert spent Zn–Mn batteries into Zn–Mn ferrite.

Study on Extraction of Iron From Chromite

Research about extraction of iron from chemical-grade South African chromite by carbothermic reduction and hydrochloric acid leaching was conducted in this study. It was found that temperature had a remarkable effect on the extraction yield of iron and that the optimum experimental temperature was 1100 °C, which coincides with the theoretically predicted value. The effect of reduction duration and the process of precipitate development at 1100 °C were also investigated. It was found that selective reduction of iron reached near completion within 2 h with only minor loss of chromium. Results also demonstrated that 20% hydrochloric acid was strong enough to extract iron from the reduction product selectively and at the same time increased the porosity of the chromium-rich solid particle. Ultimately, there is a clear improvement of the Cr/Fe ratio, Cr2O3% and specific surface area of chromite, and magnetite was obtained as by-product.

리튬전지 전극물질 재활용을 위한 습식공정의 개선

A new hydrometallurgical route was investigated for improvement in the recycling of valuable metals from electrodes of lithium batteries. The recycling process involves reductive acid leaching, doublesolvent extraction, and direct electro-winning in an organic solution. The dissolution rate of metal from the electrodes was up to 90% in 2 M sulfuric acid with hydrogen peroxide (10 vol%) at 75 °C, within 60 min. The improvement of dissolution by hydrogen peroxide seems to be due to reduction of Co(III) to Co(II), which can readily be dissolved. Cobalt and lithium were extracted into Cyanex 272 and a room-temperature ionic liquid of [EMIM] TFSI, respectively, whereas most nickel and manganese did not move to the organic phases. Lithium in the [EMIM] TFSI could be directly reduced as a form of metal by non-aqueous electrowinning. The dense electrodeposits were composed of metallic lithium and an alloy with a gold substrate. †(Received September 26, 2013)

DISSOLUTION AND PRECIPITATION OF ZINC AND MANGANESE OBTAINED FROM SPENT ZINC-CARBON AND ALKALINE BATTERY POWDER

The aim of this study was to investigate manganese and zinc recoveries from spent zinc-carbon and alkaline battery powder. The effect of sulfuric acid concentration, ascorbic acid dosage, reaction temperature and leaching time on zinc and manganese dissolutions was investigated. The optimum reductive acid leaching conditions were determined as: 3 hours, 70 °C, 0.5 M of sulfuric acid concentration, 13 g/dm 3 of ascorbic acid dosage, 1/20 g/cm 3 of solid/liquid ratio and 200 rpm of stirring speed. Under these conditions, dissolution efficiencies were 99.99% for Zn and 99.25% for Mn. In addition, dissolution kinetics of manganese was undertaken, and the activation energy was found to be 7.04 kJ/mol. Using 3 M NaOH as precipitating agent at room temperature, 95.35% of Zn (at pH 8) and 93.66% of Mn (at pH 10) were precipitated from the leaching solution. Under the same conditions, using 3 M KOH, precipitations of Zn and Mn were 91.63% and 96.39%, respectively. Based on the experimental results, a flowsheet of zinc and manganese recovery was proposed.

Simultaneous recovery of Zn and MnO2 from used batteries, as raw materials, by electrolysis

High purity electrolytic manganese dioxide (EMD) is the main raw material used for manufacturing of zinc and manganese based portable batteries (alkaline with manganese AlMn and zinc carbon Zn–C). Lately, due to the progressive depletion of MnO2 natural resources, the quantity of artificially electrolytic produced MnO2 has started to increase to satisfy the demand.This paper describes an electrolytic process for the simultaneous production of the following components:•MnO2, with the same quality as the one used in portable batteries;•commercial quality zinc, resulted from Zn and Mn sulphate solution obtained from reductive acid leaching (see Buzatu et al., 2012 paper). The sulphate solution is a by-product of used portable batteries crushing process.The electrolysis process was conducted in a specialized laboratory facility. The study was particularly focused on the following electrolysis process parameters:•evolution of MnO2 deposit efficiency based anodic current density;•sulphuric acid concentration influence on zinc metal and MnO2 deposit. The results have allowed the identification of optimal conditions for electrolysis.

Preparation and Electrochemical Performance of Nano-Co3O4 Anode Materials from Spent Li-Ion Batteries for Lithium-Ion Batteries

A hydrometallurgical process for the recovery of cobalt oxalate from spent lithium-ion batteries was used to recycle cobalt compound by using alkali leaching, reductive acid leaching and chemical deposition of cobalt oxalate. The recycled cobalt oxalate was used to synthesize nano-Co3O4 anode material by sol-gel method. The samples were characterized by thermal gravity analysis and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and charge/discharge measurements. The influence of molar ratio of Co2+ to citric acid and calcination temperature on the structure and electrochemical performance of nano-Co3O4 was evaluated. As the molar ratio of Co2+ to citric acid is 1:1, the face-centered cubic (fcc) Co3O4 powder shows the discharge capacity of 760.9 mA h g−1, the high coulombic efficiency of 99.7% in the first cycle at the current density of 125 mA g−1, and the excellent cycling performance with the reversible capacity of 442.3 mA h g−1 after 20 cycles at the current density of 250 mA g−1.

Reductive Acid Leaching of Low Grade Manganese Ores

Manganese recoveries from low-grade ores using organic acids as reducing agents were investigated in the present work. The acid leaching potential of both oxalic acid and citric acid were estimated. Manganese leaching amount were measured by using standard manganese curve and estimated by titration method. Effects of various acid concentrations on leaching efficiency were studied. The observed result suggested prominent manganese recovery of 66% by oxalic acid at 2 M concentration whereas citric acid had less effect on leaching showing leaching percentage upto 40% in 6 days. Acid leaching of manganese ore with both the acids gave a comparative data stating that oxalic acid leached better than citric acid.

Reductive acid leaching of laterite and metal oxides — A review with new data for Fe(Ni,Co)OOH and a limonitic ore

The reductive leaching of nickel laterite has attracted the interest of many researchers due to the enhanced kinetics of nickel and cobalt dissolution in the presence of acids and reducing agents during atmospheric, pressure, heap or bio leaching processes. Systematic studies on synthetic oxides and natural ores can shed light on the reaction mechanism and lead to investigations of beneficial reagents for further studies. This paper briefly reviews the literature and describes a comparative study of metal leaching from synthetic goethite spiked with nickel or cobalt and a limonitic laterite ore to rationalise the role of reducing agents in acid media. Results are discussed on the basis of the effect of speciation, surface chemical reactivity of oxides and heterogeneous kinetic models.

Process for the recovery of cobalt oxalate from spent lithium-ion batteries

A hydrometallurgical process for the recovery of cobalt oxalate from spent lithium-ion batteries (LIBs) has been developed using alkali leaching followed by reductive acid leaching, solvent extraction and chemical deposition of cobalt oxalate. The active cathode powder material was first leached with 5 wt.% NaOH solution for the selective removal of aluminum; and the residues were further leached with 4 M H 2SO 4 + 10% v/v H 2O 2 solution. The leaching efficiency of cobalt was 95% and lithium was 96% under optimum conditions of liquid/solid ratio 10:1, leaching time 120 min and a temperature 85 °C. The impurity ions of Fe(III), Cu(II), Mn(II) in the leach liquor were precipitated by adjusting the pH value. Cobalt(II) was then extracted selectively from the purified aqueous phase with saponified P507 (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) and chemically deposited as oxalate from the strip liquor with a yield of ~ 93% and purity > 99.9%. This process is simple, environmentally friendly and adequate for the recovery of valuable metals from spent LIBs.

Dried leaves — Novel reductant for acid leaching of manganese ore

In the present investigation results on the use of dried leaves as a reductant for manganese ore leaching is reported. A complete flow-sheet consisting of steps such as reductive acid leaching, enrichment of leach solution by recycling, iron removal and crystallization has been developed for the preparation of manganese sulphate monohydrate from manganese ore of Gujarat Mineral Development Corporation (GMDC), Ahmedabad, India. During leaching effects of pulp density, amount of acid, temperature, particle size of ore and reductant to ore ratio were studied. Almost total manganese extraction could be achieved under the following conditions: leaching time 8h, H2SO4 5% (v/v), pulp density 10% (w/v), temperature 950C and dried leaves to ore ratio 0.5. Mn enriched (> 90 g/L Mn) leach liquor was obtained by recycling the leach solution twice. The solution so obtained was purified by pH adjustment using lime slurry. A schematic flowsheet for the preparation of manganese sulphate monohydrate crystal is given.

Recovery of manganese from zinc alkaline batteries by reductive acid leaching using carbohydrates as reductant

Acid leaching of manganese from the powders of exhausted zinc alkaline batteries has been studied using carbohydrates as reducing agents. A mono-saccharide (glucose) and a di-saccharide (lactose) have been tested, the second as a template of industrial wastes. Manganese leaching was complete in the presence of both carbohydrates, along with zinc. Data from the factorial test with lactose have been analysed with ANOVA. The most significant effects for manganese extraction were sulphuric acid concentration, temperature, and lactose concentration.

Reductive acid leaching of spent zinc–carbon batteries and oxidative precipitation of Mn–Zn ferrite nanoparticles

The non-magnetic 8-mesh undersize material obtained by crushing, magnetic separation and sieving of spent zinc-carbon batteries assayed 23.9% Mn, 14.9% Zn, and 4% Fe. Reductive acid leaching of this material at a solid/liquid ratio of 1:10, and 60 °C with 2 mol dm − 3 H 2SO 4 and 0.39 mol H 2O 2 extracted 97.9% Mn, 98.0% Zn and 55.2% Fe after 60 min. The leach liquor composition was then adjusted to a Mn:Zn:Fe molar ratio of 1:1:4 suitable for producing MnZnFe 4O 8 ferrite powder by adding Mn(II), Zn(II) and Fe(II) sulfates. The effect of pH in the range pH 5–12 on the precipitation of Mn–Zn ferrite powder was investigated over 60 min using O 2 gas flow rate of 1.3 dm 3 min − 1 at 80 °C. The precipitated Mn–Zn ferrite at pH 12 were 20 nm particles that had a spinel structure. The saturation magnetizations of Mn–Zn ferrite powder (Mn 1 − x Zn x Fe 2O 4) were determined to be 39–91 emu/g with various zinc contents ( x = 0.2–0.8).

Characterisation and classification of solid wastes coming from reductive acid leaching of low-grade manganiferous ore

The present work was focused on the acid leaching process for manganese extraction in reducing environment to low-grade manganiferous ore that comes from Central Italy. The aim of this study was to establish optimum leaching operating conditions to reduce treatment costs of waste or, even better, to allow a waste valorisation as raw materials for other applications. Consequently, the main focus of the work was the characterization and classification of the solid wastes coming from the process carried out at different operating conditions; at the same moment the effect of process parameters on Mn extraction was also analysed. The effect of particles size on the manganese extraction in reductive acid leaching process was investigated, by using lactose as reducing agent. Particle size did not show a large influence on the Mn extraction yields in the investigated process conditions. This aspect suggests the use of the leaching waste for civil and/or environmental application: use of leaching solid wastes like filling material is to be applied, for example, for environmental restoration. The classification of the solid wastes, according to the Italian Laws about Release Test (RT), has demonstrated that the solid waste produced by leaching can be classifiable as “hazardous special waste”. An improvement of solid washing let to reduce the SO 4 2− and an appropriate treatment is necessary to reduce the dangerousness of these solids. Possible application of ore and waste as raw materials in the ceramic industry was demonstrated not to be feasible.

Recovery of zinc and manganese from alkaline and zinc-carbon spent batteries

This paper concerns the recovery of zinc and manganese from alkaline and zinc-carbon spent batteries. The metals were dissolved by a reductive-acid leaching with sulphuric acid in the presence of oxalic acid as reductant. Leaching tests were realised according to a full factorial design, then simple regression equations for Mn, Zn and Fe extraction were determined from the experimental data as a function of pulp density, sulphuric acid concentration, temperature and oxalic acid concentration. The main effects and interactions were investigated by the analysis of variance (ANOVA). This analysis evidenced the best operating conditions of the reductive acid leaching: 70% of manganese and 100% of zinc were extracted after 5 h, at 80 °C with 20% of pulp density, 1.8 M sulphuric acid concentration and 59.4 g L −1 of oxalic acid. Both manganese and zinc extraction yields higher than 96% were obtained by using two sequential leaching steps.

Reductive acid leaching of manganese dioxide with glucose: Identification of oxidation derivatives of glucose

The oxidation of glucose during the reductive leaching of pure MnO 2 and manganese ore in sulphuric acid at 90 °C MnO 2 was investigated. The aim was to identify the derivatives and the chemical pathway of glucose oxidation. Organic derivatives were monitored by HPLC using an Aminex HPX-78H column and UV detection. Chromatographic patterns of leaching solutions showed that major compound formed was formic acid. Minor quantities of glycolic, glyceric and traces of gluconic acids were identified. Results suggest that during the leaching reaction, the carbon chain of glucose is shortened by detachment of one carbon atom as formic acid.

Column leaching of a manganese dioxide ore: a study by using fractional factorial design

Reductive acid leaching of a manganese dioxide ore has been carried out in a fixed bed column in order to monitor and evaluate the effect of some process parameters on the manganese, iron and calcium extraction yields: although manganese is the metal of interest, iron and calcium were selected as representative of the most significant contaminants of the leach liquor. A two-level fractional factorial design was planned to study the effect of five process factors: temperature, reagent concentration, ore particle size, solid/liquid ratio and flow rate of leaching solution were taken in consideration in the experimental tests. The main effects and the interaction among the factors investigated were obtained by ANOVA, carried out for each selected leaching time, taking into consideration manganese, iron and calcium extraction yields as response of the process. This analysis permitted to establish temperature and reagent concentration exerting the most important positive effect on the manganese extraction yield: 93% of manganese dissolution was obtained after 4 h of leaching in the following experimental conditions: temperature 70°C, S/L ratio 1/2, specific flow rate 1223 L/m 2 h, +50% of reagent excess (H 2SO 4 and glucose) and 208–252 μm as ore size fraction. Each statistically significant main and interaction effects, evaluated in the selected leaching time, were correlated by empirical models in order to build a general model to perform simulation studies valid in the investigated range of experimental conditions but helpful for further modelling studies. Besides these experimental and simulation studies, the potential application of column leaching conditions in the extraction of manganiferous ores has been shown, although further work should be carried out in order to investigate a much more wide range of process conditions.