Evaluation of metal-ions containing sludges in the preparation of black inorganic pigments


Inorganic pigments were prepared from industrial wastes: galvanizing sludges resulting from Cr/Ni plating processes (S. G, and T) and a sludge generated from steel wiredraw process that is Fe-rich (F). These industrial wastes were characterized in order to determine the main compositional variations and discover their influence on the colour characteristics of pigments for glazes and ceramics. The toxic character was also investigated and established. Attempting to form the black spinel structure, several combinations of sludges were prepared and then calcined at 1000 degrees C. XRD and microscopy analysis confirmed the presence of nichromite for compositions with higher Ni amounts, while trevorite was detected in iron-rich formulations. The combination of S and F sludges (SF compositions) generates pigments with higher black colorimetric quality, which is similar to, and sometimes better than, a commercial black pigment. Pigments containing GF and TF sludges develop brown hues on glazes and on porcelain stoneware bodies, being this effect more evident upon industrial firing trials. The addition of minor amounts of cobalt or manganese enhances the black coloration, and might adjust some formulation deviations. (C) 2010 Elsevier B.V. All rights reserved.



subject category

Engineering; Environmental Sciences & Ecology


Hajjaji, W; Seabra, MP; Labrincha, JA

our authors


The work was supported by FCT (project PTDC/CTM/72318/2006). The support of Revigres in performing the industrial trials should also be emphasized.

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