Ternary micro-electrolysis filter media for efficient PFOA removal in water: synthesis, characterization, and performance study

This study reports the preparation of granular ternary micro-electrolysis materials and their effectiveness in removing the emerging contaminant PFOA. Al/nZVI/C@F granules were synthesized using a liquid-phase reduction method combined with high-temperature calcination. By comparing the removal of methylene blue dye by granules, the optimum preparation conditions were determined as follows: Fe:C = 5:1, fly ash = 50%, calcination temperature = 800 °C, and holding time = 1 h. Static batch experiments revealed that under optimal conditions (PFOA concentration = 25 mg/L, solid-liquid ratio = 30 g/L, pH = 3, reaction temperature = 15 °C), Al/nZVI/C@F achieved a PFOA removal rate of 97.83%. The removal efficiency of Al/nZVI/C@F (93.90%) was significantly higher than that of commercial iron-carbon (12.75%). After 45 days of dynamic column experiments, the removal efficiency of nZVI/C@F and Al/nZVI/C@F for PFOA (50 mg/L) remained above 60%, demonstrating strong practical application potential. Further adsorption-desorption experiments revealed that nZVI/C@F and Al/nZVI/C@F primarily removed 50 mg/L PFOA through adsorption. For a lower PFOA concentration of 0.5 mg/L, the defluorination rates were 53.2% for nZVI/C@F and 68.9% for Al/nZVI/C@F. High-performance liquid chromatography-tandem mass spectrometry was used to analyze the intermediates formed during PFOA removal, leading to a proposed degradation pathway.