Preparation of Foamed Ceramic from Cr Slag and MSWI Fly Ash and Its Cr Leaching Inhibition

The sustainable utilization of solid waste is crucial for environmental protection. This work investigates the fabrication of foamed ceramics from Cr slag and municipal solid waste incineration (MSWI) fly ash, focusing on the effects of three inhibitors-NH2SO3H, ZnO·TiO2, and (NH4)2HPO4-on material properties and Cr leaching behavior. Experimental analysis, chemical thermodynamic calculations, and material characterization were all employed. Results show that the prepared foamed ceramics meet the JG/T 511-2017 standard for building materials, exhibiting excellent physical properties but significant Cr leaching. Among the inhibitors, (NH4)2HPO4 with a molar ratio of n(P)/n(Cr) = 1 shows the best performance, achieving a bulk density of 205 kg/m3, compressive strength of 0.850 MPa, Cr leaching concentration of 188 μg/L, and a 70.0% of Cr leaching inhibition rate. The improvement is attributed to the AlPO4 formation that enhancing the strength, and Ca2P2O7 that stabilizing Cr during sintering. This work provides a feasible method for the safe resource utilization of Cr-containing waste.