A comparison study of Fenton-like and Fenton reactions in dichloromethane removal

Dichloromethane (DCM), as a low-chlorinated organic compound, is hardly to be degraded through the reductive dechlorination pathway. In this study, the removal of DCM in Fenton-like system, using activated carbon fibres-supported zero-valence Fe/Ni nanoparticles (ACF-Fe/Ni) as catalysts, was investigated and compared with that of a traditional Fenton system (Fe²⁺/H₂O₂). The influence of vital parameters, including initial solution pH, DCM concentration, catalyst and H₂O₂ dosages, temperature and cosolute on the removal of DCM, was systematically studied. The results showed that 94.2% of DCM with an initial concentration of 5 mg/L could be removed in the Fenton-like reaction under the optimum condition: initial pH of 2.0, 0.4 g/L of ACF-Fe/Ni, 10 mM of H₂O₂ and a temperature of 30°C. In comparison, the removal of DCM in the Fenton-like system was faster than that of the Fenton system and the corresponding activation energies were 39.69 and 33.82 kJ/mol, respectively. The coexistence of solute was adverse to the removal of DCM in both Fenton-like and Fenton systems. Moreover, the active species for DCM removal in the Fenton-like system was confirmed as hydroxyl radical (·OH) via the quenching experiment and electron paramagnetic resonance measurement. The incomplete mineralisation (41.7%) of DCM after reaction indicated that the Fenton-like technology had the potential to realise DCM's non-toxic and harmless conversion and organic intermediates formed needed to take longer time to be decomposed.