Distribution behavior of inorganic constituents in chemical recycling processes of a municipal waste slag

A chemical recycling process of inorganic wastes has been developed, where after vitrifying wastes, the glasses were heat-treated and soaked in an acid, obtaining colorless and transparent SiO₂-abundant glasses. In the present study, distribution behavior of the constituents such as Si, P, Ti, Al and so on present in a municipal waste slag was examined. According to compositional analyses, the recovered solids after acid treatment consisted of SiO₂, P₂O₅ and TiO₂, suggesting the preferential distribution of P and Ti atoms into SiO₂-rich phase during phase separation. In high resolution microscopic analyses, however, it was observed that P and Ti atoms were distributed separately from Si atoms, and they were present in the different particles insoluble in the acid. It was finally concluded that the insoluble solids were produced by a dissolution-reprecipitation process, that is, once all the constituents of the vitrified slag were dissolved in the acid, P₂O₅ and TiO₂ coprecipitated as particles, and TiO₂ was indispensable for the precipitation of P₂O₅. SiO₂ also precipitated as particles separately from P- and Ti-containing particles.