Thermal Stability of Inorganic Pigments Synthesized from Galvanic Sludge

Pigments used in ceramic glazes have been obtained by chromium ions extraction from galvanic sludge and their precipitation as barium chromate and lead chromate from technological solutions. The chemical composition was determined by XRF method. Complex thermal analysis TG-DSC, XRD and SEM methods have been used for microstructural characterization and thermal treatment behaviour evaluation, in order to establish the compatibility with the ceramic matrix. XRD spectra have highlighted only lead chromate specific interferences in the monoclinic phase and barium chromate in the orthorhombic phase, suggesting an advanced degree of purity. Weight losses of 2.2% for barium chromate and 3.1% for lead chromate have been recorded on the TG curve at 800 C. As a result of thermal treatment, barium chromate has changed its colour from yellow to green.