Establishment of a Hydrometallurgical Scheme for Cleaning Cu-Ni Smelter Slag From Botswana and Its Economic Evaluation (original) (raw)
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Base metals recovery from copper smelter slag by oxidising leaching and solvent extraction
Hydrometallurgy, 2002
Due to its amorphous structure, smelter slag cannot efficiently be leached with sulphuric acid; the formation of silica gel induces an increase of leach liquor viscosity, difficult pulp filtration and crud formation during solvent extraction. The problem was solved by leaching with sulphuric acid under hydrogen peroxide, which also performs simultaneous iron oxidation and removal.A copper smelter slag from Lubumbashi, Democratic Republic of Congo, containing 1.4% Cu, 0.7% Co, 8.9% Zn and 20.9% Fe(II), has been used in this study. The leaching tests have been carried out at normal pressure on ground slag samples (<100 μm). Silica gel-free solutions containing copper, cobalt and zinc were produced, so that pulp filtration could be easily carried out.The dissolved base metals were successfully extracted from solution by solvent extraction using kerosene Shellsol D70 as diluent. Copper was extracted with LIX 984 and stripped with sulphuric acid solution. Thereafter, cobalt and zinc were collectively extracted with D2EHPA and then separated by selective scrubbing with sulphuric acid solutions of different dilutions. This method provided an overall recovery of 80% Cu, 90% Co and 90% Zn in separated solutions which could be further treated by electrowinning or salt precipitation.
Minerals, 2020
An innovative, economical, and environmentally sound hydrometallurgical process has been proposed for recovering Cu, Ni, and Co from copper-rich converter slag by organic acids. In the leaching experiments, the effects of organic acid concentrations, pulp density, temperature, and time were investigated. Optimum recovery of 99.1% Cu, 89.2% Ni, 94% Co, and 99.2% Fe was achieved in 9–10 h at 308 K (35 °C) temperature and 15% pulp density with 2 N citric acid using <45 µm particles. Pourbaix diagrams of metal-water-citrate systems were supplemented to examine solubility of ligands at the desired conditions. Furthermore, the leaching mechanism was based on the SEM-EDS (energy-dispersive X-ray spectroscopy) and XRD characterization as well as the leaching results obtained.
Investigation of Effective Parameters in Copper Slag Ammonia Leaching
In this research copper recovery from Ghaniabad smelter slag by ammonia leaching was studied. Main mineralogical phases (Magnetite, fayalite and augite) and chemical composition of slag was determined using XRD and XRF analysis. Copper content of sample was determined 1.7% by chemical digestion and atomic adsorption spectroscopy. Bornite and chalcocite were identified as the main copper bearing phases by microscopic observations. The ammonia/ ammonium carbonate leaching experiments were carried out and the effect of different parameters such as ammonia concentration, ammonium carbonate concentration, temperature, solid/ liquid ratio and leaching time were investigated. Temperature and ammonia concentration were found as most important parameters. Under optimum leaching conditions (2 M NH 3 , 0.4 M (NH 4 ) 2 CO 3 , solid/ liquid ratio= 10%, 70 °C and 4 h), 78% of Copper were effectively recovered. The partially undissolved copper was assumed to be in silicate phases.
Waste Management and Treatment of Copper Slag BCL, Selebi Phikwe Botswana: Review
Procedia Manufacturing, 2019
The production of copper bears both viable product and by product know as slag which is a challenge to dispose and poses a problem to the environment. BCL holds copper slag is seen as waste which is ironopulent containing heavy metals which can seep into ground water and affect environment. These metal accumulate in millions of tonnes year after year posing as a threat to the environment and need to be managed to avoid them being harmful. This paper explores metallurgical ways of treating the slag and utilizing it in different ways. Extracting metals such as iron is one way of managing the slag, as previous research and present indicate that iron can be recovered from copper slag. This will help manage the waste slag and rehabilitate land sustainably. The copper slag can also be used in cement and concrete production and provides potential environmental and economic benefits for all parties involved. The BCL dump will be regarded as raw material rather than waste hence igniting management and treatment of waste to sustainability.
The present work, carried out within the project VALMETAIS, proposes a hydrometallurgical process for copper and nickel recovery from galvanic sludges produced by Ni/Cr plating plants. The procedure has been developed on laboratory scale and the results validation was verified in a small sized pilot scale. The project starts with a leaching process of sludge in sulphuric acid solution in three stages followed by copper cementation step, using iron scrap as precipitating agent. It was found that metals dissolution was almost completed for the three stages of leaching process. Extraction rates of 99% for Cu and Ni were achieved under the leaching. The solid residue separated from the leaching solution is mostly constituted by gypsum (CaSO 4), and presents heavy metal content below 1%. Copper cementation process was performed at a pH of 2. Such pH level led to insignificant precipitation of other metals present in the leaching solution, particularly chromium. The recovery rate of copper is about 99% with a purity grade of 99% which enables its application as a commercial product. Nickel hydroxide precipitation was performed by adding sodium hydroxide solution. Results showed a successfully nickel hydroxide extraction obtaining 99% with a purity grade of more than 98%. These evidences demonstrate the high potential of this methodology to treat and derive economic benefits from galvanic sludge. The end products cooper and nickel can be applied as a commercial product generating a profit and the gypsum based sludge from the leaching process can be reutilized as component of construction materials. INTRODUCTION Industrial units of surface metal plating generate wastewaters that need to be treated to produces good quality water to be recycled into the process. During the wastewater treatment, usually by physical-chemical methods, significant amounts of sludge are produced. For nickel and chromium plating processes the resulting sludge is classified as hazardous waste according to Council Decision 2000/532/CE and represents a potential source of environmental contamination. This classification is due to the high concentration of mobile/leachable species, such as heavy and/or transition metals like chromium and nickel [1,2]. In fact, besides water (typical solids content is under 40%) and some soluble salts, the galvanic sludge is composed of metallic species and additives and its composition dependent of the processing conditions [3,4]. These sludges are frequently sent to landfills with no valorization or economic benefits. This is clearly the least desirable option from both the environmental and economical points of view. For that reason available alternatives or appropriate routes that enable the valorization of those wastes with material recovery must be developed. Different studies have been carried out in order to develop possible technologies for the chemical fixation of galvanic sludges in clay based ceramic materials, such as common formulations for tiles and bricks. The main mechanism for the inertization of phases with high levels of heavy metals in ceramic matrixes was described by Magalhães et al [5,6]. Alternatives technologies for
Organic acid leaching of base metals from copper granulated slag and evaluation of mechanism
Canadian Metallurgical Quarterly, 2017
A hydrometallurgical method is discussed to selectively extract base metals such as copper, cobalt, nickel and iron from the copper granulated slag (0.53% Cu) at atmospheric pressure. It involves firststage leaching of slag with organic (citric acid) to selectively recover cobalt, nickel and iron. The residue containing high copper was subjected to second-stage leaching with inorganic (sulphuric) acid. Leaching parameters such as acid concentration, pulp density, temperature and time were optimised to extract metals from the granulated slag. A maximum recovery of 4.47% Cu, 88.3% Co, 95% Ni and 93.8% Fe were obtained in first-stage leaching with 2 N citric acid at room temperature using 10% pulp density (w/v) in 8-9 h. On subjecting the leach residue to the second-stage leaching with 2 M sulphuric acid, 66-72% Cu was recovered in 4 h. The kinetics of the metal leaching from the slag was established by the XRD and SEM-EDAX studies of the residues. RÉSUMÉ On discute d'une méthode par hydrométallurgie pour extraire sélectivement les métaux de base comme le cuivre, le cobalt, le nickel et le fer à partir de scories granulées de cuivre (0.53% Cu) à la pression atmosphérique. La méthode implique une première étape de lessivage des scories avec une matière organique (acide citrique) afin de récupérer sélectivement le cobalt, le nickel et le fer. Le résidu à teneur élevée en cuivre a été exposé à une deuxième étape de lessivage avec un acide inorganique (acide sulfurique). On a optimisé les paramètres de lessivage comme la concentration de l'acide, la densité de la pulpe, la température et la durée, afin d'extraire les métaux à partir des scories granulées. On a obtenu une récupération maximale de 4.47% de Cu, 88.3% de Co, 95% de Ni et 93.8% de Fe lors de la première étape de lessivage avec de l'acide citrique 2N à la température de la pièce en utilisant une densité de pulpe de 10% (poids/ volume), en 8 à 9 h. En exposant le résidu de lessivage à la seconde étape de lessivage avec de l'acide sulfurique 2 M, on a récupéré de 66 à 72% de Cu en 4 h. On a établi la cinétique de lessivage du métal à partir des scories au moyen d'études de XRD et de SEM-EDAX des résidus.
Copper ammonia leaching from smelter slag
International Journal of Biology and Chemistry
Copper smelter slag can be considered as an important source for using in the copper hydrometallurgy. Ammonia leaching seems to be attractive for processing copper slag. Under the influence of ammonia, copper, which is part of the minerals of copper, forms soluble ammonia complexes, while iron precipitates as insoluble compounds. In the present work, the possibility of leaching the copper smelter slag (1.26 wt.% Cu) of the Balkhash smelter using NH 4 OH solutions was considered. The effect of experimental factors (leaching duration, reagent concentration, temperature, stirring rate, as well as a solid-to-liquid ratio) on the extraction of copper into solution was studied. It was found that the extraction of copper into solution increases with increasing temperature (in the studied range 298-333 K), pulp density (up to 10 pct) and stirring rate (up to 800 rpm). The concentration of NH 4 OH almost does not affect on the level of copper extraction in the range of 1-4 M. The following experimental conditions provide the recovery of 65% of Cu into ammonia solution: 1M NH 4 OH, T = 333 K, particle size 90% < 200 mesh, solid-to-liquid ratio 10 pct, stirring rate 800 rpm, and leaching duration 180 min, 65% of copper is extracted into the solution. Shrinking core model with mixture kinetics was used to describe the process of ammonia leaching of copper from smelter slag. The activation energy and pre-exponential factor for the reactions of copper dissolution were calculated to be 16.2 ± 0.7 kJ/mol and 0.138 ± 0.001 min-1 , respectively. The relatively low value of the activation energy indicates that the rate of the overall leaching process is controlled mainly by the processes of mass transfer rather than by the rate of chemical reactions of copper dissolution.
Small sized pilot scale experiments on the recovery cooper and nickel hydroxide from galvanic sludge
1St International Conference Wastes Solutions Treatments and Opportunities, 2011
The present work, carried out within the project VALMETAIS, proposes a hydrometallurgical process for copper and nickel recovery from galvanic sludges produced by Ni/Cr plating plants. The procedure has been developed on laboratory scale and the results validation was verified in a small sized pilot scale. The project starts with a leaching process of sludge in sulphuric acid solution in three stages followed by copper cementation step, using iron scrap as precipitating agent. It was found that metals dissolution was almost completed for the three stages of leaching process. Extraction rates of 99% for Cu and Ni were achieved under the leaching. The solid residue separated from the leaching solution is mostly constituted by gypsum (CaSO 4 ), and presents heavy metal content below 1%. Copper cementation process was performed at a pH of 2. Such pH level led to insignificant precipitation of other metals present in the leaching solution, particularly chromium. The recovery rate of copper is about 99% with a purity grade of 99% which enables its application as a commercial product. Nickel hydroxide precipitation was performed by adding sodium hydroxide solution. Results showed a successfully nickel hydroxide extraction obtaining 99% with a purity grade of more than 98%. These evidences demonstrate the high potential of this methodology to treat and derive economic benefits from galvanic sludge. The end products cooper and nickel can be applied as a commercial product generating a profit and the gypsum based sludge from the leaching process can be reutilized as component of construction materials.
Development of a Process for Copper Recovering from Galvanic Sludges
Galvanic coating processes are based on metal plating baths and are responsible for the production of large amounts of wastewaters. Subsequent physical-chemical treatment of the wastewaters generates solid wastes called galvanic sludges. These sludges have a hazardous character and are often disposed, mainly on landfills, without any economical or environmental benefits. The development of alternatives and viable ways to reduce the environmental impact and recover the valuable metals contained in those sludges such as copper, chromium, nickel or zinc, which content might reach 30% (wt.%, dry weight) are of utmost importance. The present work has been developed in the aim of the project VALMETAIS and proposes a hydrometallurgical process for copper recovery from galvanic sludges produced by Ni/Cr plating plants. This procedure has been developed on laboratory scale and is based on leaching of sludges in sulphuric acid solution followed by copper cementation step, using iron scrap as a precipitating agent. The sludge has been characterized for its chemical and physical properties. Chemical analysis showed a copper concentration of more than 10% (dry base). Preliminary leaching tests in both sulphuric acid and ammoniacal media were performed in order to determine the best operating conditions for this step of the process and to assure the best metal recovery conditions in subsequent separation methods. Sulphuric acid yielded much higher metal ion dissolution when compared with ammoniacal leaching. Optimal experimental leaching parameters were defined as follows: sulphuric acid solution 100 g/l, a solid to liquid ratio of 1:10, stirring speed of 400 rpm at room temperature and under atmospheric pressure. It was found that metals dissolution was almost complete in 30 minutes of reaction time. Extraction rates of 99% for Cu and Ni were obtained under the leaching conditions above mentioned. The solid residue separated from the leaching solution is mostly constituted by gypsum (CaSO 4), and presents a metal content below 1%. The subsequent extraction of cooper from the obtained solution is achieved by a cementation step with iron scrap. Copper precipitation was performed at a pH of 2 which was achieved through adding new sludge to the filtered leaching solution. Such pH level led to insignificant precipitation of other metals present in the leaching solution, namely chromium. The recovery rate of copper is about 90% and the purity grade of the resulting copper cement enables its application as a commercial product.