Solidification/stabilization of municipal solid waste incineration (MSWI) fly ash during fired brick manufacturing by pelleting confinement and phase transformation

The primary challenge in incorporating municipal solid waste incineration (MSWI) fly ash into the production of fired brick lies in enhancing the solidification and stabilization of chlorides and heavy metals. This study proposed a novel method to suppress the evaporation and leaching of Cl salts and heavy metals by confining MSWI fly ash in pellets and incorporating Cl salts into stable Cl-containing phase. The palletization process of MSWI fly ash before mixing clay to mold raw brick could effectively reduce the volatilization and leaching of Cl salts and improve the mechanical strength of the brick. Moreover, the addition of glass powder during pelleting MSWI fly ash further enhanced the physical-mechanical properties of bricks and substantially reduced the leaching risks of Cl salts and heavy metals. Specifically, Cl volatilization and leaching ratios were reduced by 31.09–48.11 % and 18.13–30.99 %, Cl solidification efficiency was increased over 93 %. The improvement in solidification/stabilization of Cl salts and heavy metals relies primarily on physical confinement into pellets and chemical transformation of into stable Cl-containing mineral phases (Ca10Si6O21Cl2 and Ca3SiO4Cl2). Anyway, pelleting mixtures of fly ash and glass powder is proved to enhance both the property performance and environmental safety of the bricks, which could be regarded as an efficient solution with the practical and theoretical significance for the utilization of fly ash in construction materials.