Enhanced degradation of ibuprofen by heterogeneous electro-Fenton at circumneutral pH

Abstract

Fenton based reactions are effective for pharmaceutical removals, but traditional Fenton processes have drawbacks of pH adjustment and large amount of produced iron sludge. To overcome these challenges, a heterogeneous electro-Fenton process was proposed for effective contaminant degradation at circumneutral pH without iron sludge production. The anti-inflammatory drug ibuprofen (a common pharmaceutical in natural waters) was used as a representative contaminant. Activated carbon fibers (ACFs) supported ferric citrate (Cit-Fe/ACFs) was synthesized and used as the cathode, and RuO₂/Ti was used as the anode. H₂O₂ was electro-generated in situ from O₂ reduction and the production rate of OH per unit area was 6.8 μM W^-1 cm^-2 using Cit-Fe/ACFs cathode. A maximal ibuprofen degradation of 97% was obtained after 120 min at the current density of 7 mA cm^-2. The electrical energy per order (E_EO) varied from 0.24±0.03 to 2.65±0.04 kWh log^-1 m^-3 when the current density ranged from 1 to 7 mA cm^-2. The Cit-Fe/ACFs cathode showed relatively good reusability and ∼85% IBP removal was achieved after 6 cycles of degradation. Our results showed that the prepared Cit-Fe/ACFs cathode was promising for the treatment of pharmaceutical contaminants.

Keywords: Activated carbon fibers; Ferric citrate; Heterogeneous electro-Fenton; Ibuprofen.