Rafiu B. Bale

Development of a combined pyro- and hydro-metallurgical route to treat spent zinc–carbon batteries

The potential of solvent extraction using Cynanex272 for the recovery of zinc from spent zinc carbon batteries after a prior leaching in hydrochloric acid has been investigated. The elemental analysis of the spent material was carried out by ICP-MS. The major metallic elements are: ZnO (41.30%), Fe(2)O(3) (4.38%), MnO(2) (2.69%), Al(2)O(3) (1.01%), CaO (0.36%) and PbO (0.11%). The quantitative leaching by hydrochloric acid showed that the dissolution rates are significantly influenced by temperature and concentration of the acid solutions. The experimental data for the dissolution rates have been analyzed and were found to follow the shrinking core model for mixed control reaction with surface chemical reaction as the rate-determining step. About 90.3% dissolution was achieved with 4M HCl solution at 80 degrees C with 0.050-0.063 mm particle size within 120 min at 360 rpm. Activation energy value of 22.78 kJ/mol and a reaction order of 0.74 with respect to H(+) ion concentration were obtained for the dissolution process. An extraction yield of 94.23% zinc by 0.032M Cyanex272 in kerosene was obtained from initial 10 g/L spent battery leach liquor at 25+/-2 degrees C and at optimal stirring time of 25 min. Iron has been effectively separated by precipitation prior to extraction using ammoniacal solution at pH 3.5, while lead and other trace elements were firstly separated from Zn and Fe by cementation prior to iron removal and zinc extraction. Finally, the stripping study showed that 0.1M HCl led to the stripping of about 95% of zinc from the organic phase.

Hydrometallurgical application for treating a Nigerian chalcopyrite ore in chloride medium: Part I. Dissolution kinetics assessment

The dissolution kinetics of a Nigerian chalcopyrite ore in hydrochloric acid was studied in this article. Acid concentration, reaction temperature, and ore particle size were chosen as experimental parameters. The chemical and morphological studies of the ore before and after leaching at optimal conditions were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is revealed that increasing the acid concentration and system temperature and decreasing the ore particle size greatly enhances the dissolution rate. The dissolution kinetics was found to follow the shrinking core model for the diffusion control mechanism where the activation energy (Ea) of 32.92 kJ·mol−1 was obtained for the process and supported by morphological changes at a higher dissolution of 91.33%.

Leaching kinetics of a Nigerian complex covellite ore by the ammonia-ammonium sulfate solution

Hydrometallurgical treatment of copper sulfide ore is increasingly establishing itself as a feasible route for the extraction of copper and recovery of associated precious metals value. This is attributed to the merits of this route, which include suitability for low-grade and complex ores, high recoveries, competitive economics, and other operational features. The leaching kinetics of Nigerian complex covellite ore was investigated in ammonia-ammonium sulfate solution. The concentration of ammonia and ammonium sulfate, the ore particle size, and the temperature were chosen as parameters in the experiments. The results show that temperature, concentration of ammonia-ammonium sulfate has favorable influence on the leaching rate of covellite ores; however, leaching rate decreases with increasing particle size. At optimal conditions (1.75mol/L NH4OH+0.5mol/L (NH4)2SO4, −90+75 μm, 75 °C, with moderate stirring) about 86.2% of copper ore reacted within 120 minutes. The mechanism of the leaching was further established by characterizing the raw ore and the leached residue by EDXRF - chemical composition, SEM - structural morphology and XRD - phase identification studies. From the X-ray diffraction analysis, the partially unreacted Cu and S phases were presumed to be CuO, and the iron present in the CuS phase was mainly converted to hematite (Fe2O3·H2O), as the CuS phase disintegrated and remained in the residue afterward.

Treatment of a Nigerian covellite ore. Part I: Dissolution kinetics study by ammonia solution

In the present work, the leaching kinetics of covellite ore in ammonia solution was studied and the following variables, the solution concentration, reaction temperature and particle size were considered. A kinetics model representing the effects of these variables on the leaching rate was developed and it was ascertained that the leaching rate increases with increasing solution concentration, reaction temperature and decreasing particle size. At optimal conditions, 75.1% of covellite ore was reacted within 120 min and the leaching reaction was diffusion controlled by surface chemical mechanism. The calculated activation energy of 56.98 kJ/mol supported the proposed dissolution process.

Purification of a Nigerian Wolframite Ore for Improved Industrial Applications

Increasing demands for pure wolframite ore in the form of ammonium paratungstate (APT), tungsten oxide cannot be over emphasized. Thus, treatment of a Nigerian wolframite ore containing admixtures of scheelite (CaWO4: 96-900-9631) and stolzite (PbWO4: 96-900-9813) by hydrometallurgical route was investigated in hydrochloric acid chelated with phosphoric acid to extract tungsten via solvent extraction. During leaching, parameters such as leachant concentration, chelate dosage and reaction temperature on ore dissolution were examined. At optimal conditions (1.5 mol/L HCl + 2.0 mol/L H3PO4 solution; 75 °C), 95.0% of the initial 10 g/L ore reacted within 120 min. The derived activation energy of 56.80 kJ/mol supported the proposed dissolution mechanism. The unreacted product analyzed by XRD was found to contain siliceous impurities. Tungsten recovery from leachate was carried out by solvent extraction with Aliquat 336 in kerosene. Pure tungsten was recovered as APT and beneficiated to produce high grade industrial tungsten oxide of industrial values.

Dissolution behaviour of a beryl ore for optimal industrial beryllium compound production

ABSTRACT This study involves the leaching of the beryl ore with sulphuric acid (H2SO4) solution for predicting optimal beryllium extraction conditions with the aim of assessing the importance of leachant concentration, reaction temperature and particle size on the extent of dissolution. A kinetic model to represent the effects of these variables on the leaching rate was developed. It was observed that the dissolution of beryl ore increases with increasing H2SO4 concentration, temperature, decreasing particle size and solid to liquid ratio. At optimal leaching conditions, 89.3% of the ore was reacted by 1.25 mol/L at 75°C temperature and 120 minutes with moderate stirring, where 1612.0 mg/L Be2+, 786.7 mg/L Al3+, 98.1 mg/L Fe3+ and 63.4 mg/L Ag+ were found as major species in the leach liquor. The unleached products constituting about 10.7% were examined by X-ray diffraction (XRD) and found to contain primarily, siliceous compounds such as Xonotlite, Antigorite, Chrysolite and Kaolinite.

Preparation of High Grade Industrial Copper Compound from a Nigerian Malachite Mineral by Hydrometallurgical Process

Increasing demands for copper and copper sulphate with diverse industrial applications has prompted the development of a low-cost and eco-friendly technique as a substitute for conventional ore treatments by reduction-roasting route, requiring high energy consumption. In this study, hydrometallurgical treatment of a Nigerian malachite through acid leaching and solvent extraction was investigated. The effects of leachant concentration, reaction temperature and particle size were examined. The rate of ore dissolution increased with increasing H2SO4 concentration, temperature and decreasing particle size. At optimal leaching conditions, 96.2% of the ore reacted with 2.0 mol/L H2SO4 solution at 75 °C within 120 min. The calculated activation energy was 25.41 kJ/mol, supporting the proposed diffusion controlled mechanism for the dissolution process. The leach liquor at optimal conditions was further beneficiated to obtain high grade industrial copper sulphate using a combinations of solvent extraction and precipitation methods, leading to 98% process efficiency.