Characterization of industrial secondary desulphurization slag by chemical fractionation with supportive X-ray diffraction and scanning electron microscopy

• Slag characterization through fractionation, parallel XRD analyses and SEM-EDS
• Only pseudo-total Cr and V notably recovered from the six-week slag samples
• Fluctuation in slag composition can have a significant effect on slag Cr
• 353 mg kg− 1 (d.w.) reducible V coupled with larnite/merwinite dissolution
• SEM-EDS identification of V association hindered by overlapping with peaks

Secondary desulphurization slag from integrated carbon steelmaking was investigated to attain information on respective utilization possibilities or effects upon final disposal. Pseudo-total element concentrations were determined during a six-week sampling period with EN 12457-2/12457-3 compliance test recoveries, scanning electron microscopy + X-ray microanalysis (SEM-EDS) and trace element fractionation with supportive X-ray diffraction (XRD) of parallel extraction residues. Only trace elements Cr and V showed significant pseudo-total recoveries with 210 and 1270 mg kg− 1 (d.w.), respectively. 88% of the respective Cr was attained in the residual fraction of the extraction procedure, as a labile H2O-extractable Cr(VI) concentration of 1.6 mg kg− 1 (d.w.) was attained during the EN 12457-2 test. The RSD value of Cr (32%) in the determined pseudo-total contents of weekly subsamples indicated that fluctuation in slag composition can have a significant effect on the trace element contents of the material. In the case of V, 28% (353 mg kg− 1, d.w.) of the respective pseudo-total concentration was recovered in the NH2OH∙HCl-extractable fraction, in which XRD suggested only the potential dissolution of larnite. A majority of V (i.e., 65%) was recovered in the residual fraction coupled with the potential dissolution of magnetite and merwinite, as recovery in the HOAc-extractable fraction remained below the limit of quantitation. Additional SEM-EDS investigations proved unsuccessful in exclusively identifying potential V association in the slag samples due to overlapping with additional peaks.