Novel method for comprehensive utilization of MSWI fly ash through co-reduction with red mud to prepare crude alloy and cleaned slag

Abstract Municipal solid waste incineration fly ash (MSWI-FA) is classified as hazardous waste that requires an effective processing method. This study proposed an innovative technique process, co-reduction of MSWI-FA and red mud followed by magnetic separation, to prepare crude alloy and cleaned slag. In this process, MSWI-FA acted not only as a reductant to reduce metal minerals in MSWI-FA and red mud to form an alloy, but also as a calcium additive to enhance the reduction of metal minerals and alter the melting point of the CaO-SiO2-Al2O3 system. Under optimal conditions, 85.52% Fe, 80.10% Cu, 92.96% Ni, and 66.74% Cr can be recovered in the form of a Fe-Cu-Ni-Cr alloy. The Fe-Cu-Ni-Cr alloy containing 96.47% Fe, 0.81% Cu, 0.65% Ni, and 0.42% Cr can be used for weathering steel production. Other heavy metals, including Cd, Pb, and Zn, were removed via volatilization. The toxicity characteristic leaching procedure test indicated that the leaching toxicity of the cleaned slag was substantially below the standard limits. The characteristics of the cleaned slag were similar to those of ground granulated blast furnace slag, suggesting its potential application in cement production.