Integrating dual-stage gas permeable membranes and humic acid recovery to optimize fenton oxidation of landfill leachate: Insights into full-process performance and DOM molecular-level transformation

This research introduces an innovative full-process treatment technology that integrates dual-stage gas permeable membranes (GPM) and humic acid (HA) recovery to enhance Fenton oxidation of landfill leachate (LFL). In terms of full-process performance, this integrated approach (LFL-GPM-HA (Fenton)) synergistically combines LFL concentration, ammonia recovery, HA recovery, purified water reclamation, and efficient Fenton oxidation, thereby achieving holistic minimization, detoxification, and resource recovery of LFL. Specifically, under the conditions of low-intensity aeration and a temperature gradient of 65–55–25 °C, the GPM achieved an ammonia recovery rate exceeding 96 %, while the LFL was concentrated by a factor of 4.72 within 12 h. During HA recovery at pH 2, the HA yield from the concentrated LFL reached 3.68 g/L, representing an 88.72 % increase compared to the raw LFL. Due to the significant consumption of bicarbonate alkalinity during the GPM process, the required dosage of H₂SO₄ per gram of HA recovered was reduced by 86.72 %. Under different dimensionless oxidant dosages, the LFL-GPM-HA (Fenton) demonstrated a significant improvement in COD removal efficiency compared to standalone Fenton oxidation. In terms of dissolved organic matter (DOM) molecular-level transformation, ESI FT-ICR-MS analysis showed a significant enhancement in the removal of CHOS and CHONS in LFL-GPM-HA (Fenton), with a concurrent reduction in the produced sulfurous byproducts. Additionally, the LFL-GPM-HA (Fenton) notably increased the frequency of decarboxylation, desulfurization, and dealkylation reactions. In terms of operational stability and economic feasibility, this integrated system demonstrates excellent long-term stability and robust membrane fouling-cleaning recovery properties, achieving LFL treatment at a cost of approximately 12.142 $/m³, which is significantly more cost-effective than conventional full-process advanced treatment technologies (20–30 $/m³). In conclusion, the findings offer a pathway for developing more efficient and cost-effective strategies for LFL management.