Synthesis of black ceramic pigments from secondary raw materials

Black ceramic pigments were prepared from industrial wastes as raw materials, namely, Cr/Ni-rich sludge generated from Cr/Ni plating and Fe-rich galvanizing sludge generated during steel wiredrawing. The pigment was based on the chrome–iron–nickel black spinel (Ni,Fe)(Fe,Cr)2O4 catalogued as 13-50-9 in the DCMA classification and prepared by the common solid-state reaction method, under optimal formulation and processing conditions. The characterised synthesised pigments were tested in typical ceramic glazes and ceramic bodies. Optimal colour development was achieved when the spinel compound with the three elements Fe, Ni and Cr was the major phase formed. This situation was obtained for mixtures in which the amount of Cr/Ni-rich sludge varied between 50 and 75%. The colouring properties were similar to those imparted by a commercial black pigment.