Combination of air-dispersion cathode with sacrificial iron anode generating Fe ²⁺ Fe ³⁺ ₂ O ₄ nanostructures to degrade paracetamol under ultrasonic irradiation

In the present study, ultrasound (US) was coupled with an electrochemical process (ECP) consisting of a novel cathode of carbon cloth (CC)-carbon black (CB) as the nano-composite air-dispersion cathode (NADC) for the degradation of paracetamol (APAP) in an aquatic medium. The NADC favored in situ production of H ₂ O ₂ by the cathodic reduction. The implementation of iron sacrificial anode instead of dimensionally stable anodes resulted in the generation of Fe ²⁺ Fe ³⁺ ₂ O ₄ nanostructures in the solution. The Fe ²⁺ Fe ³⁺ ₂ O ₄ nanostructures were activated by means of both US and H ₂ O ₂ to produce more [rad]OH in the aqueous solution. In addition, the utilization of US caused the conversion of H ₂ O ₂ to [rad]OH irrespective of free oxidizing radicals generated through cavitation phenomenon. The hybrid method based on coupling US and NADC-ECP in the presence of Fe ²⁺ Fe ³⁺ ₂ O ₄ nanostructures proved synergism (39.8%) allowing to effective decomposition of APAP. The pulse mode of US enhanced the degradation efficiency of APAP as compared to the sweep and normal modes. The intermediates of the degradation route were identified using GC–MS analysis as well as mineralization efficiency. The toxicity assay was also performed based on the inhibition test using activated sludge of a biological wastewater treatment plant.