Effect of annealing treatment on the crystallisation and leaching of dumped base metal smelter slags

Maweja, Kasonde; Mukongo, Tshikele; Mbaya, Richard; Mochubele, Emela A.

doi:10.1016/j.jhazmat.2010.07.023

Cited by 13 publications

(7 citation statements)

References 16 publications

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“…This may be attributed to incorporation of these phases within individual wastes; Cu droplets (CS) are merged in glass, whereas Cu-sulfides (LM) are hidden between fayalite crystals. Glass is known for its higher susceptibility to dissolution as compared to crystalline phases [17,38] and this behavior of major phases was presumably a deciding factor. Zinc extraction from LM (Fig.…”

Section: Efficiency Of Element Extraction With Equi-normal Mineral Anmentioning

confidence: 99%

Bioleaching and toxicity of metallurgical wastes

Potysz

Pędziwiatr

Hedwig

et al. 2020

Journal of Environmental Chemical Engineering

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Metallurgical wastes contain metals that are unrecovered during industrial processing. The disposal of these wastes is technically difficult due to the potential release of metals through weathering. Therefore, alternative management methods are currently sought. The high leaching susceptibility of these wastes combined with the need for alternative sources of rare and critical metals creates a need for residual element recovery. This study evaluated the leaching potential of lead matte and copper slag through chemical mineral acid leaching as well as indirect bioleaching with organic acids and direct bioleaching using Acidithiobacillus thiooxidans. The leaching efficiency of these acids was compared based on different normality equivalents. Additionally, the effects of pulp density (1-10%) and extraction time (24-48 h) were assessed. Slag toxicity was assessed with a germination test in concentrated and diluted leachates using Brassica juncea. The results demonstrated that copper slag is particularly suitable for chemical treatment because as much as 91 wt.% Cu and 85 wt.% Zn or 70 wt.% Cu and 81 wt.% Zn were extracted using HNO 3 or bacterial leaching, respectively. The residual slag was characterized by significant metal depletion and the presence of gypsum, rendering it more suitable for further use or disposal. Lead matte released 65 wt.% Cu and 8 wt.% Zn using mineral acid leaching while 70 wt.% Cu and 12 wt.% Zn were released using bacterial leaching. Further process optimization is needed for lead matte to generate residue depletion in toxic metals. Toxicity assessment showed toxic characteristics in metal-loaded leachates originating from waste treatment that inhibited germination rates and root development.

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Section: Efficiency Of Element Extraction With Equi-normal Mineral Anmentioning

confidence: 99%

Bioleaching and toxicity of metallurgical wastes

Potysz

Pędziwiatr

Hedwig

et al. 2020

Journal of Environmental Chemical Engineering

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“…24,25) The reason is thought to be that the silicate structure in the amorphous phase collapsed easily during acid leaching, but crystalline phase had better chemical stability. 24) Therefore, in the present study, the different dissolution behavior of matrix phase is attributed to the crystalline state of the matrix phase. Under rapid cooling, slag did not have enough time to crystallize, and the amorphous matrix phase formed, which resulted in a higher dissolution ratio of the matrix phase.…”

Section: Effect Of Cooling Ratementioning

confidence: 99%

Effects of Cooling Rate and Acid on Extracting Soluble Phosphorus from Slag with High P<sub>2</sub>O<sub>5</sub> Content by Selective Leaching

Gao

Ueda

et al. 2017

ISIJ Int.

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With the use of low-grade iron ores with high P content, slag with high P 2 O 5 content generated after dephosphorization is considered a great potential source of P. Because of the solubility difference between the solid solution and matrix phase, it is possible to extract the P-rich solid solution selectively from slag by leaching. The soluble P obtained is suitable to produce phosphate fertilizers. To achieve selective leaching of P and increase its dissolution ratio, the effects of the cooling rate and acid on dissolution of the slag in aqueous solutions at pH 5 and 7 were investigated. This study found that during solidification, slow cooling facilitates coarsening of the solid solution and formation of the magnesioferrite phase. The solid solution was dissolved preferentially. At pH 7, the air-cooled slag showed the highest dissolution ratio of P. When the pH was decreased to 5, slag dissolution was significantly promoted. As the cooling rate decreased, the dissolution ratio of P increased. Slow cooling not only enhanced dissolution of the solid solution but also suppressed dissolution of the matrix phase. Citric acid performed better in promoting dissolution of slag. At pH 5, almost all of the solid solution was dissolved from the furnace-cooled slag. However, the dissolution ratio of Fe was also high. When nitric acid was used, 66.8% of the solid solution was dissolved, without dissolution of large amounts of the matrix phase. After leaching, the P 2 O 5 content in the residue reduced and the Fe 2 O 3 content increased.

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“…Environmental and socio-economic impacts of such slags are some compelling considerations in favour of further recovery of valuable metals [ 19 , 20 ]. The composition of the slag is dependent on the mineralogy of the ore, but it typically contains oxides of gangue elements such as iron, silicon, magnesium, calcium, phosphorus, and copper [ 21 , 22 , 23 ]. The slag also contains some proportions of copper matte that is mechanically dragged when tapping from the settling zone of the smelter crucible [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

Mineralogical Characterization of Historic Copper Slag to Guide the Recovery of Valuable Metals: A Namibian Case Study

Dzinomwa,

Mapani,

Nghipulile

et al. 2023

Materials

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The depletion of the ore reserves in the world necessitates the search for secondary sources such as waste products (tailings and slag). The treatment and cleaning up of such secondary sources also has a positive impact on the environment. A smelter in Namibia we examined had historic slag which accumulated over decades of its operating life, thus posing the challenge of how best to collect representative samples to evaluate and propose viable methods of recovering contained metals. In this study, analytical and mineralogical characterization of the slag was performed using X-ray fluorescence (XRF) analysis, atomic absorption spectrometer (AAS), ICP-OES, scanning electron microscopy energy dispersive spectroscopy (SEM-EDS) analysis, and optical microscopy analysis. The chemical analyses showed that the metal values contained in the slag were mainly copper, lead, and zinc whose average contents were approximately 0.35% Cu, 3% Pb, and 5.5% Zn. About 10.5% Fe was also contained in the slag. Germanium was detected by scanning electron microscopy, but was however below detection limits of the chemical analysis equipment used. Based on the results, approximate conditions under which the different slag phases were formed were estimated and the recovery routes for the various metals were proposed. Analysis by both optical and scanning electron microscopy revealed that Zn and Fe occurred mainly in association with O as oxides, while Cu and Pb were mainly associated with S as sulphides. The slag consisted of three different phases, namely the silicate phase (slag), metallic phase and the sulphide phases. The phases in the slag were mainly silicate phases as well as metallic and sulphide phases. It was observed that the metallic and sulphide phases were dominant in the finer size fractions (−75 µm) whereas the sulphide phase was also present in the coarser size fractions (+300 µm). An important finding from the microscopy examination was that the sulphide phases were interstitial and could be liberated from the slag. This finding meant that liberation and subsequent concentration of the sulphide phases was feasible using conventional processing techniques.

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Effect of annealing treatment on the crystallisation and leaching of dumped base metal smelter slags

Cited by 13 publications

References 16 publications

Bioleaching and toxicity of metallurgical wastes

Bioleaching and toxicity of metallurgical wastes

Effects of Cooling Rate and Acid on Extracting Soluble Phosphorus from Slag with High P<sub>2</sub>O<sub>5</sub> Content by Selective Leaching

Mineralogical Characterization of Historic Copper Slag to Guide the Recovery of Valuable Metals: A Namibian Case Study

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