Long-term leaching mechanism of chromium-containing slag after vitrification and heat treatment

Vitrification and heat treatment are economical methods for utilizing Cr-containing slag; however, the prepared products have different Cr solidification abilities. Herein, the effects of the two routes on the long-term leaching behavior of Cr-containing slags were studied. The Mg, Al, and Cr contents and heat treatment were found to influence the type and relative content of the mineral phases, which further promoted the Cr leaching behavior of the samples. Among them, the 5Al-3Cr glass and heat-treated samples exhibited relatively higher Cr leaching accumulation. Compared with the heat-treated samples, the glass samples had a better solidification ability, particularly for the high-Cr-containing group. The Cr leaching accumulation decreased by 70%-90%, indicating that the vitrification of the melt can effectively inhibit the formation of the Cr-leachable phase. During the leaching process, the dissolved Ca/Mg/Al ions influence the pH and redox potential of the liquid environment, resulting in the oxidation of Cr3+ to Cr6+. This research showed that vitrification is a safer and more effective route for the utilization of Cr-containing slag.