Malayaite Ceramic Pigments Prepared from Industrial Wastes: Formulation and Characterization

Abstract

In this work chrome-tin red malayaite pigments Ca(Cr,Sn)SiO5 were obtained from industrial wastes: a marble sawing sludge, a galvanizing sludge from the Cr/Ni process and a foundry sand. The pigments were prepared using the common solid state reaction process. The influence of Cr2O3/SnO2 ratio, calcination temperature and introduced sludges compositions, on its structural stability, was investigated by X-ray diffraction coupled with SEM/EDS. Standard formulations, obtained from commercial reagents, were also prepared and characterized for sake of comparison. CIELab colour measurements and UV-Vis spectroscopy were used to evaluate the stability (thermal and chemical) and applicability of the synthesized pigments in colouring distinct ceramic matrixes fired at high temperatures (1050°C-1200°C). The pigment was added (1/20 wt. ratio) to a transparent and shining lead free glaze and to a porcelain stoneware body (1/10 wt. ratio). The incorporation of three industrial wastes, in the chrome-tin red malayaite pigment, was possible without a notorious change in terms of colouring effect allowing decreasing the synthesis temperature.