Synthesis of chromium containing pigments from chromium galvanic sludges

In this work the screening results of the scientific activity conducted on laboratory scale to valorise chromium (III) contained in the galvanic sludge as chromium precursor for ceramic pigments are reported. The valorisation of this waste as a secondary raw material (SRM) is obtained by achievement of thermal and chemical stable crystal structures able to colour ceramic material. Two different pigments pink CaCr0.04Sn0.97SiO5 and green Ca3Cr2(SiO4)3 were synthesized by solid-state reactions using dried Cr sludge as chromium oxide precursor. The obtained pigments were characterized by X-ray diffraction and SEM analysis. Furhermore the color developed in a suitable ceramic glaze was investigated in comparison with the color developed by the pigments prepared from pure Cr2O3. The characterization carried out corroborates the thermal and chemical stability of the synthesized pigments and, especially for the Cr-Sn pink pigment, the powders develop an intense color that is very similar to the color developed by the pigments obtained starting from pure Cr2O3.