Synthesis of ceramic pigments from industrial wastes: Red mud and electroplating sludge

The perception of industrial waste has changed, in the last decades, from an economic and environmental problem to a potential raw material. In this work, the synthesis of a stable pigment was prepared by combining two hazardous and unexplored wastes: red mud (RM, rich in Fe) and electroplating sludge (ES, rich in Ni/Cr). The wastes were mixed in different proportions and calcined at 1200 degrees C. Black and brown pigments were obtained from the mixture of RM/ES in 1:3 and 1:1 wt proportions, respectively. The color was given by the chrome-iron-nickel spinels, based on Ni2+ T-3(1g)(F-3) transitions (approximate to 13,000 cm(-1)), Cr3+ (4)A(2g) -> T-4(1g)(F-4) transitions (approximate to 24,400 cm(-1)) and Fe3+ (approximate to 15,000-approximate to 122,500 cm(-1)). The achieved coloring strength and thermal stability on various ceramic glazes render excellent prospects for the industrial application of such waste-based pigments. (C) 2018 Elsevier Ltd. All rights reserved.