Application of boron-doped diamond electrodes for the anodic oxidation of pesticide micropollutants in a water treatment process: a critical review

Boron-doped diamond (BDD) electrodes have the greatest known oxygen overpotential range; a characteristic that has allowed the material to be well suited for electro-oxidation processes in aqueous media. When operating in a potential range of water decomposition, strongly oxidising hydroxyl radicals are formed while oxygen evolution is minimised. The majority of research studies undertaken to-date have focused on the application of BDDs for the remediation of wastewater contaminants, however there is an increasing need for a suitable technology to address recalcitrant micropollutants in a drinking water context. Pesticide micropollutants are widely detected in surface- and ground-waters and are of increasing concern. In this paper, the treatment of pesticides by BDD electro-oxidation is reviewed. Their degradation and mineralisation, as well as the effect of operating conditions, formation of intermediate by-products, reaction pathways and kinetics are summarized. In general, BDD electro-oxidation was found to be effective for the degradation of pesticides with the degradation performance proportional to the electrolytic current, due principally to the increased generation of (OH)-O-center dot radicals. Most contaminants followed pseudo first-order reaction kinetics under mass transport limitations. Generally, the same aromatic and aliphatic by-products were formed through similar oxidation pathways. Finally, research gaps and potential future research topics are discussed.