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

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.