Study of the Structure of FeOx-CaO-SiO2-MgO and FeOx-CaO-SiO2-MgO-Cu2O-PdO Slags Relevant to Urban Ores Processing through Cu Smelting

Mohammad Mehedi Hasan,M Al Hossaini Shuva,M Akbar Rhamdhani,Geoffrey A Brooks

doi:10.3390/met10010078

Mohammad Mehedi Hasan, M Al Hossaini Shuva + Show 2 more

Open Access

https://doi.org/10.3390/met10010078

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Journal: Metals	Publication Date: Jan 2, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Swinburne University of Technology

Abstract

Ferrous-calcium-silicate (commonly known as FCS) slags are used in the valuable metal recycling from urban ores through both primary and secondary copper smelting processes. In the present study, the structure of selected FCS-MgO (FCSM) and FCS-MgO-Cu2O-PdO (FCSM-Cu2O-PdO) slags, relevant to the processes, were investigated using Fourier-transform infrared (FTIR) spectrometry. Deconvolution of the FTIR spectra was carried out to calculate the relative abundance of different silicate structural units (Qn), the overall degree of polymerization (DOP) of the slags and the oxygen speciation in the FCS slags. It was observed that, for the slag investigated, the relative intensity of both the high-frequency band ≈ 1100 cm−1 (Q3) and low-frequency band ≈ 850 cm−1 (Q0) were affected by Fe/SiO2 ratio, basicity, temperature (T) and oxygen partial pressure (pO2). The DOP and the average number of bridging oxygen (BO) were found to decrease with increasing both Fe/SiO2 ratio and basicity. Improved semi-empirical equations were developed to relate the DOP of the slags with chemistry, process parameters and partitioning ratio (i.e., the ratio of the amount of element in the slag phase to metal phase, also known as distribution ratio) of Pd and Ge. Possible reactions, expressed as reactions between metal cations and silicate species, as a way to evaluate thermodynamic properties, are presented herein.

Highlights

Slags play a vital role in pyrometallurgical processes, such as in the production, recycling and refining of liquid metal
The characteristic Fourier-transform infrared (FTIR) spectra of the silicate anionic units are typically found in the wavenumber range of 700 cm−1 to 1200 cm−1
The increase of non-bridging oxygens (NBO)/T in silicate melts support the notion that the depolymerization of slag increases with increasing Fe/SiO2 ratio

Summary

Introduction

Slags play a vital role in pyrometallurgical processes, such as in the production, recycling and refining of liquid metal. The chemistry and structure of a slag controls the removal of impurities from the liquid metal to the slag, and vice versa—the partitioning of the selected valuable elements to metal phase from the slag [1,2]. The slag chemistry influences both the thermophysical and thermodynamic properties, such as density, viscosity, electrical conductivity, foaming index, thermal conductivity, surface tension, partition ratio, molar entropy, diffusivity and mixing free energy of silicates [3,4,5]. A clear understanding of the relations between the slags’ chemistry, structure and their properties is vital for designing suitable slags for the appropriate process conditions. Urban ores are the waste materials that are sources of many base metals and other valuable elements.

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