Ceramization of heavy metals in (Ba1−X Mx)Al2Si2O8 celsian solidsolutions and recycling as pigments

Abstract

Ceramization of several heavy metals (M = Cr, Fe, Co and Ni) in celsian lattice has been studied by sinter-ing up to 1500 °C of its oxides with BaCO3,Al(OH)3and SiO2in order to obtain (Ba1XMx)Al2Si2O8solidsolutions. Cr3+enters in solid solution forming cationic vacancies up to x = 0.5 (both celsian and hexac-elsian coexist), Fe3+and Co2+only up to x = 0.1 (both celsian and hexacelsian coexist), melting at higherx values, while Ni only forms solid solution at low x (0.02), coexisting hexacelsian and celsian, and athigher x NiAl2O4spinel crystallizes. However, the use of glass-forming mineralizers such as boratesincreases reactivity and monophasic celsian is obtained in the case of Co-celsian solid solution (adding10 wt% of glass-forming agent) at only 1000 °C/3h of sintering temperature. These powders have beenreused as ceramic pigments and leaching test is performed in order to classify the resulting solid solu-tions for its landfill disposal (Council Directive 1999/31/EC on the waste landfill).