| Abstract |
The non-ferrous metal industry, such as Cr/Ni/Cu plating, produces acid sludge which is usually neutralized with lime slurry in batch processes, and the resulting waste is dewatered by vacuum filtration or filter-pressing. Dewatered sludge contains calcium sulphate (CaSO4) coming from the neutralization process, as well as transition metals (Cr, Ni and Cu), oil, grease and suspended solids. In this communication, two residual sludges from Cr/Ni/Cu plating have been dried (110 degrees C) and fired (1100 degrees C), and both dried (gray coloured) and fired powders (black coloured) have been characterized by DTA-TG, XRD and SEMEDX techniques. XRD shows only quartz crystallization in dried samples, while NiCr2O4 chromite spinel and NiO periclase crystallize in fired powders, along with CaSO4 anhydrite and CaSiO3 wollastonite. The powders have been introduced as ceramic pigments into three different conventional glazes: a) a lead bisilicate (PbO.2SiO(2)) double fire frit (1000 degrees C), b) a double fire frit with low lead content (1000 degrees C), and c) a double fire frit without lead (1050 degrees C). Glazed samples were characterized by UV-Vis-NIR (diffuse reflectance) and CIEL/a/b/(color parameters). Dried powders induce glaze defects (pin-holing and crawling), but fired powders did not show these faults exhibiting more intense (higher L-*) and yellowish (higher b(*)) black colors than the standard spinel. (c) 2018 Elsevier B. V. All rights reserved. |
