| 1. |
- Kero Andertun, Jakob, et al.
(author)
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Characterisation and leaching behavior of CaO-modified iron-silicate slag produced in laboratory and industrial scales
- 2021
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In: Canadian metallurgical quarterly. - : Taylor & Francis. - 0008-4433 .- 1879-1395. ; 60:4, s. 294-305
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Journal article (peer-reviewed)abstract
- Water-granulated CaO-modified iron-silicate slags have shown beneficial properties for cement applications. To further evaluate potential applications, the leaching properties must be understood. Therefore, this study aims to characterise and assess the metal leaching of iron-silicate slags (2.6% CaO) modified with lime (CaO, up to 20 wt.%) produced on both laboratory and industrial scales. The granulated samples showed amorphous contents for the studied CaO range. Generally, the metal content of the samples decreased with the increasing CaO content. Batch leaching tests were conducted on the slags, and the metal leaching and CaO content of the slag were strongly correlated. The leaching of Zn and Cu decreased with the increasing CaO content in the slag. Overall, the slags with 12–13% CaO exhibited minimal leaching of Zn, Cu, Ni, and Sb. These findings indicate that CaO influences the properties of the slag and can suppress metal leaching from water-granulated iron-silicate slags.
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| 2. |
- Kero Andertun, Jakob, et al.
(author)
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Characterisation and leaching behaviour of granulated iron silicate slag constituents
- 2022
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In: Canadian metallurgical quarterly. - : Taylor & Francis. - 0008-4433 .- 1879-1395. ; 61:1, s. 14-23
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Journal article (peer-reviewed)abstract
- Due to increased copper production and the associated environmental consequences, copper production processes need to be improved, considering the impact of their byproducts, among others slag. This study investigated the leaching of individual constituents of iron silicate slag from a copper smelter. This was done by characterising granulated samples of its constituents – glass, matte, speiss – to determine their leaching contribution. It was observed that leaching in distilled and deionised water without pH regulation achieved various natural pH for the constituents. At natural pH, glass (Cu, Zn) and speiss (Ni, Sb) contributed to leaching. Static pH titrations showed the increased leaching of Zn, Cu, Ni, As, and Sb with decreasing pH. The results showed that, an iron silicate slag consisting of glass, matte and speiss, contributes to leaching as follows: matte – Cu and Ni, speiss – Cu, Ni, As, and Sb. Zn leaching is similar among the constituents.En raison de l’augmentation de la production de cuivre et des conséquences environnementales associées, on a besoin d’améliorer les processus de production du cuivre, tenant compte de l’impact de leurs sous-produits, parmi lesquels les scories. Cette étude a examiné la lixiviation des constituants individuels des scories de silicate de fer provenant d’une fonderie de cuivre. Ceci a été accompli en caractérisant les échantillons granulés de ses constituants –verre, matte, smaltite–pour déterminer leur contribution à la lixiviation. On a observé que la lixiviation dans de l’eau distillée et désionisée sans régulation du pH atteignait divers pH naturels pour les constituants. Au pH naturel, le verre (Cu, Zn) et la smaltite (Ni, Sb) contribuaient à la lixiviation. Les titrages de pH statique ont montré une augmentation de la lixiviation du Zn, Cu, Ni, As et Sb avec une diminution du pH. Les résultats ont montré que les scories de silicate de fer composées de verre, de matte et de smaltite contribuent à la lixiviation comme suit: matte–Cu et Ni, smaltite–Cu, Ni, As et Sb. La lixiviation du Zn est similaire parmi les constituants.
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| 3. |
- Kero Andertun, Jakob
(author)
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Leaching of water-granulated iron silicate slags and their compounds : A study of synthetic and industrial slag systems
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Copper smelter slag is a residue product of the pyrometallurgical extraction of copper. Due to its physical properties, the iron silicate type of copper smelter slag has many possible application areas, e.g., different aggregates and abrasives. During the copper-making process, some copper becomes distributed in the slag; therefore, copper recovery from the slag is commonly done through slag treatment processes. Despite treatment, copper-containing inclusions can remain in the final slag. In order to secure the environmental properties of slags containing inclusions, the leaching mechanisms needs to be understood, which is the focus of the thesis presented.Synthetic and industrial iron silicate slags have been studied with respect to the impact of the slag constituent’s oxide (glass), sulfide (matte) and metalloids (speiss) on leaching as well as the impact of chemical composition (ZnO and CaO content). The synthetic slags are melted in laboratory furnaces. The industrial slags have undergone a Zn-fuming and settling process (including CaO additions for some slags) to recycle and reduce the zinc content and further separate copper-containing inclusions such as sulfide (matte) and metalloid (speiss) species. The materials investigated in the thesis are solidified using water granulation.All materials are characterized by their chemical compositions and mineralogy. Further, industrial slag constituents are investigated regarding their leaching contribution. Syntheticiron silicate (oxide) is investigated regarding the influence of ZnO content and granulation temperature on Zn leaching. CaO-modified industrial iron silicate slags are investigated regarding the leaching of specific elements (e.g., Cu, Zn, Ni, As, Sb). The leaching tests examine the effect of pH, oxidation and time using water leaching, acid and oxidating leaching and dynamic leaching methods.Characterizing the slag constituents shows that the glass mainly contains amorphous iron silicate. The matte contains mainly copper sulfides, and speiss contains copper metalloids. The leaching results show that the glass contributes to Cu and Zn leaching at pH 8.4, and the speiss contributes to Ni and Sb leaching at pH 7.8. Further, the leaching contribution of matte and speiss increased with decreasing pH. The main leaching elements from the matte and speiss include Cu, Ni, As and Sb.Characterization of the ZnO-modified iron silicate shows that Zn is mainly distributed in glass and partly in fayalite. Further, the Zn leaching increases with granulation temperature, ZnO content in the glass and decreasing pH.Characterization of CaO-modified slags shows that up to 20 wt.% CaO dissolves into the glass phase. An increased CaO content resulted in increased Ca leaching, yielding higher pH. Leaching of Zn, Cu, Ni and Sb was on the other hand shown to decrease. Further, long-term leaching studies confirm increasing pH and Ca leaching. In contrast, the leaching of Cu, Zn and Ni showed a peak after a certain time, which was lowered with increasing CaO content in the slags. The leaching of As and Sb increased with increasing leaching time, but the increase diminished with increasing CaO content in the slags. A lower pH and an oxidating environment increased the leaching of Zn, Cu and Ni.The summarized results from this thesis indicate that the glass contributes to Zn leaching while copper-containing inclusions matte and speiss contribute to the leaching of Cu, Ni, As and Sb. The leaching of elements from the copper-containing inclusions matte and speiss can be limited by ensuring a pH buffer preventing acidification, for example, by CaO modification. CaO modifications decrease the slag leaching resistance, which contributes to increasing pH in the leachate by Ca-dissolution and hence decreased leaching of copper-containing inclusions in the slag. Also, the Zn leaching from the slag decreased with increasing pH in the leachate.
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| 4. |
- Kero Andertun, Jakob, 1991-, et al.
(author)
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Long-Term Leaching Effects on CaO-Modified Iron Silicate Slag
- 2022
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In: Minerals. - : MDPI. - 2075-163X. ; 12:11
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Journal article (peer-reviewed)abstract
- Granulated iron silicate slag, a by-product of pyrometallurgical copper extraction, has excellent properties for construction applications. Slag modification with CaO enhances the application properties regarding pozzolanic reactivity, potentially extending slag use in the future. The slags’ short-term leaching behavior has already been investigated with promising results, while the long-term leaching effects are less studied. Therefore, this study aims to determine the long-term leaching effects on CaO-modified iron silicate slags. The CaO-modifications were conducted during full-scale slag treatment operation. The slags were characterized and leached, and the remaining slags were investigated regarding the formation of secondary phases. The long-term leaching of main and trace elements was determined over 30 days using a dynamic leaching method corresponding to an extended time period. The leaching tests showed increased leaching of the main slag elements (Si, Ca). Zn and Cu showed peak leaching after four days of leaching, and the leaching of As and Sb decreased with the increasing CaO content in the samples. After dynamic leaching, secondary phases formed on the Cu-containing inclusions on the sample surfaces. Independent of the CaO content, the leaching of Cu was increased when subjected to external acidic and oxidating conditions using static pH titration at pH 5 in dilute nitric acid.
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| 5. |
- Kero Andertun, Jakob, et al.
(author)
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The Effect of Zn Content and Granulation Temperature on Zn Leaching in an Fe-Saturated (FeXZn(1−X))2SiO4 System
- 2022
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In: Minerals. - : MDPI. - 2075-163X. ; 12:6
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Journal article (peer-reviewed)abstract
- The zinc in the fayalite slag of copper smelters, in which Zn-containing raw materials are used, is mainly found to be in oxidic phases, such as glassy iron silicate. During the slag water granulation process, the molten slag is heated, whereby the granulated slag achieves varying granulation temperatures. Therefore, in this study, we aimed to characterize and assess the leaching behavior of a synthesized Fe-saturated (FeX,Zn(1−X))2SiO4 system to understand the dependance of the zinc leaching behavior on the parameters of the ZnO content (1–10 wt.%) and granulation temperature (1300 or 1400 °C). It was found that the Zn leaching increased with the increasing Zn content and granulation temperature, using both batch and static pH leaching methods. Zn leaching was further increased at pH 5 using diluted nitric acid under oxidation conditions. Among the oxides in the samples—fayalite, spinel, and glass—glass was found to contribute to Zn leaching, owing to its weathering during pH-titration.
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