Role of the mixing conditions and composition of galvanic sludges on the inertization process in clay-based ceramics

Abstract

Hydroxide-metal sludges from electroplating industry are a potential source of environmental contamination due to their high content of heavy metals. The incorporation of these residues in a ceramic matrix can be a promising way to suppress the harmful effect of metals normally present in those sludges. This work reports the role of the mixing time between the waste and ceramic materials and of the calcination step on the fixing level of several metal-containing species (Al, Zn, Ni, Fe, Ca, Cu, Cr) after sequential leaching in different media (aqueous, acetate and citrate). A strong and/or long mixing process will promote the deagglomeration of the coarser agglomerates and then will increase the reactivity of remaining grains towards the ceramic material during the calcination. As a consequence, inertization is improved for fired samples. With non-calcined samples leaching increases as a result of increasing dispersability/availability of species.

Effect of experimental variables on the inertization of galvanic sludges in clay-based ceramics

“…6 and 7). As detailed in another work [22], a longer and violent mixing process that might increase the specific surface area, disseminates the sludge-containing metallic species. If combination reactions upon firing are not so extent, their availability during leaching increases.…”

Incorporation of solid wastes in red ceramics: an updated review

“…Inertization of sludges from galvanic processes into clay-based ceramics has also been investigated [134][135][136][137][138]. In particular, Magalhães et al [134] evaluated the effect of several processing parameters such as the mixing time, the calcination temperature and its duration as well as the relative amount of sludge, and the physical aspect of the sample on the fixing level of relevant species (SiO 2 , SO4 2− , Zn, Ni, Ca, Cu, Cr) by leaching in different media (aqueous, acetate, and citrate).…”

High chemical stability of stoneware tiles containing waste metals

“…A large amount of work has been carried out to validate the inertization of galvanic waste in a clay based matrix [16][17][18][19] or to develop a pigment based material by using chromium waste as precursor. [20][21][22] However an effective mechanism has not been developed up to now that allows combining the inertization aspects and a commercial product with aesthetical differences keeping the standard industrial process.…”