Sustainable synthesis of artificial humic substances from bamboo powder by FeCl3-catalyzed low-temperature pyrolysis for cadmium contaminated soil remediation and carbon sequestration.

In this study, a green method for synthesizing artificial humus (A-HS) from bamboo powder (BP) by FeCl3-catalyzed low-temperature pyrolysis (200-300 °C) under alkaline conditions was proposed. Under optimal conditions (250 °C, 1.0 wt% Fe), the yields of artificial humic acid (A-HA) and fulvic acid (A-FA) reached 18.80 ± 1.61 wt% and 25.96 ± 1.24 wt%, respectively. Py-GC/MS and 13C NMR analyses confirmed that FeCl3 and KOH synergistically promoted deoxygenation, decarbonylation, hydroxylation/ketonization, and the Maillard reaction. The synthesized A-HA demonstrated highly oxidized aromatic structures with abundant carbonyl (‒COOH, 6.29 %) and phenolic (‒OH, 4.88 %) functional groups. The present study showed that the remediation of cadmium-contaminated soil by A-HS synthesized through the synergistic catalysis of FeCl3 and KOH was significantly better than that of the single catalytic system. Cadmium (Cd) fixation by HS-BP&Fe&KOH restorer reached 51 % and Cd accumulation in bok choy was reduced by 64 %. Furthermore, the soil microbial community structure was significantly restructured, with increased relative abundances of Cd-immobilizing Pseudomonas and Bacillus, accompanied by enhanced functional activities in nitrogen and phosphorus cycling. Simultaneously, the synthesis and soil application of HS-BP&Fe&KOH achieved >60 % carbon sequestration efficiency, establishing a sustainable pathway toward synergistic soil remediation and carbon neutrality objectives.