Complete solidification of landfill concentrated leachate using a minimal dosage of mayenite and its reutilization for carbonyl sulfide degradation

Abstract

Landfill concentrated leachate (CL) contains high concentrations of organic pollutants, salts, and heavy metal ions. Treatment methods for CL include recharge, evaporation, and incineration; however, these processes are challenged by high load demands, treatment complexity, and limited potential for resource recovery. Herein, the mayenite-enriched calcium-aluminum oxide (Ca_xAl_yO_z) was used to solidify CL. With an optimal dosage of 30%, the solidified product, marked as CL-CAOSP, was obtained, which not only mitigates the challenges associated with leachate discharge but also enhances the efficiency of water evaporation due to the lower binding energy at the Ca₂Al₄O₆Cl₂•10H₂O/Al₂O₃-water interface compared to that of the water-water interface. To dispose of CL-CAOSP, its organic pollutants underwent a high-temperature pyrolysis carbonization process to form porous carbon, which was tightly combined with the alkali and alkaline earth metals-doped Ca₁₂Al₁₄O₃₂Cl₂ to create an efficient hydrolysis catalyst for the toxic gas carbonyl sulfide (COS). The calcined CL-CAOSP is also capable of cyclically solidifying CL up to five times, significantly reducing the required dosage of Ca_xAl_yO_z and the generation of the terminal solidified product. These results provide novel treatment and resource utilization technologies for CL, serving as valuable guides for the implementation of CL treatment practices.