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Mill scale (MS) is a iron-rich waste generated in the wire drawing process with high iron content and is still mainly disposed in landfills. The scientific community has been studied its use in other applications such as pigments, concretes, among others. This work aims to study a new added-value application for MS—the development of coloured ceramic pastes. For this purpose, the influence of the added amount (0, 1, 3, 5 and 10 wt.%), the pre-treatment (milling + sieving at 212 μ m), the maximum firing temperature (from 1043 to 1165 ° C) and the type of furnace (laboratory/industrial) were analysed on the sample's characteristics. A dark grey stoneware product was obtained through the incorporation of 10 wt.% of MS and leaching tests conducted at pilot scale with cups confirmed its immobilization in the ceramic matrix. Furthermore, it was proved that the firing temperature can be reduced by about 100 ° C without affecting the specimen's characteristics. This reduction leads to a considerable decrease in the energy consumption upon firing, inducing economic and environmental advantages. Therefore, this work provides a new added-value application for MS and contributes to the reduction of virgin raw materials consumption and development of more sustainable stoneware products. [ABSTRACT FROM AUTHOR]

The use of wastes, some of them hazards, as raw materials of ceramic pigments has been a way to diminish their environmental impact, to economically valorize them, and to face the depletion of virgin raw materials. In this work were prepared pigments having in their composition only industrial wastes: Cr/Ni electroplating (ES), and sludges from the cutting of natural stones—marble (MS) and granite (GS). The prepared mixtures were calcined at three temperatures (1100, 1200, and 1300 °C) and the obtained powders were characterized by XRD and UV-vis. Their coloring strength and thermal stability were assessed by adding them to different ceramic substrates: glazes (transparent bright and opaque matte) and a stoneware paste. The CIEL*a*b* coordinates of the fired materials were measured. The developed pigments are thermally stable and exhibit good tinting power, originating nicely colored and defect-free ceramic materials. [ABSTRACT FROM AUTHOR]

Abstract: This work reports the development of extruded porcelain stoneware tiles that show antimicrobial (to act as a barrier to the bacteria's growth during a long period of time), and anti-stain (easy to clean) actions, and possess high chemical resistance. The antimicrobial action was proven through the reduction of Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. Staining and chemical resistance were tested according to ISO 10545-14 and 10545-13 standards, respectively. The tiles promote a population reduction of over 77% and 81% for the S. aureus and the E. coli bacteria, respectively. The optimized product was obtained by adding 2.5wt% of a black ceramic pigment to the industrially-prepared paste, followed by the application of a small quantity of glaze (by jet spraying). Chemical (solution of 98wt% NaNO3 and 2wt% AgNO3) and thermal (2h at 430°C) treatments were finally applied to get the active surface. In terms of anti-staining characteristics the tiles belong to class 5, while their chemical resistance is excellent (UA, ULA and UHA) against almost all aggressive agents, except for chloridric acid, 18% (v/v), for which a small surface attack (UHB) was observed. Furthermore, the treatments used (chemical and thermal) do not change the surface aspect of the product, and thus fulfil the industrial/commercial requirements. [Copyright &y& Elsevier]