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

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.

Synthesis and Characterization of Mesoporous Mg- and Sr-Doped Nanoparticles for Moxifloxacin Drug Delivery in Promising Tissue Engineering Applications

“…According to Virgo et al [ 56 ], different anionic structural units could be identified according to the number of NBO. A superscript number is assigned to the number of bridging oxygens (BO) present in silicate tetrahedral units, with Q0 representing zero BO and all NBO ([SiO 4 ] 4− ), Q1 one BO and 3 NBO ([Si 2 O 7 ] 6− ), Q2 two BO and two NBO ([SiO 3 ] 2− ), Q3 three BO and one NBO ([Si 2 O 5 ] 2− ) and Q4 four BO and zero NBO (SiO 2 ) [ 38 , 57 , 58 ]. The addition of acidic oxides, as network formers, results in an increase in the number of BO.…”

“…The addition of acidic oxides, as network formers, results in an increase in the number of BO. On the other hand, basic oxides act by disrupting the network, thus producing free oxygen ions (O 2− ) and NBO (O − ) and reducing the number of BO (O 0 ) [ 58 ], according to the Equation (1): O 0 + O 2− = 2O − …”

“…The kind and amount of Si-O structural units is related to the degree of depolymerization of the silicate network. Specifically, the degree of the polymerization should be decreased with basicity, confirmed by the decrease in the BO (bridging oxygens) [ 58 ]. In this respect, the addition of Ca seems to slightly affect the peak at 800 cm −1 which is attributed to the Si–O symmetric stretching vibration.…”

Slag Chemistry and Behavior of Nickel and Tin in Black Copper Smelting with Alumina and Magnesia-Containing Slags

“…Recently, Hasan et al [18] studied the structure of ferrous calcium-silicate slags with MgO addition using Fouriertransform infrared (FTIR) spectrometry. They showed that the overall degree of polymerization (DOP) of the silicate network and the average number of bridging oxygen (BO) decreased with increasing both the Fe/SiO 2 ratio and basicity (defined as CaO/SiO 2 ratio).…”