Synchronous pollution reduction and high-value valorization of humus-like soil from aged refuse: Impurity separation, heavy metal removal, and rare earth element recovery.

Landfill mining offers a sustainable solution for aged waste, but resource utilization of its main landfill-mined soil-like fractions (LMSF) fraction remains constrained by complex impurities and heavy metal contamination. Current treatment methods fail to simultaneously achieve deep purification, detoxification, and recovery of key resources. Herein, a novel cascade process was developed, integrating water-medium selective separation, chelation-based leaching, and a synchronous enrichment mechanism for rare earth elements and humic acid. Results indicated that under optimal conditions (solid-liquid ratio of 1:5, 4 circulation cycles, stirring speed of 600 rpm), the physical separation removed over 80% of inorganic inert impurities. The subsequent leaching using 0.04 mol/L EDTA achieved high elution efficiencies for Cd (95.7%), Cu (88.8%), Zn (77.4%), and Pb (71.0%), effectively mitigating ecological risks. Furthermore, the pH 4.8 NaAc-HAc buffer system recovered 81.88% of rare earth elements (344.35 mg/kg) while synergistically increasing humic acid purity by 1.6 times (to 26.71 g/kg) via the ash-reducing effect. This study provides a viable and environmentally sound technical pathway for converting contaminated aged waste into valuable resources.