Anodic oxidation of nitrobenzene on BDD electrode: Variable effects and mechanisms of degradation

The electrochemical oxidation of pesticide, nitrobenzene (NB) as one kind of pesticide that is potentially dangerous and biorefractory, was studied by galvanostatic electrolysis using boron-doped diamond (BDD) as anode. The influence of several operating parameters, such as applied current density, supporting electrolyte, and initial pH value, was investigated. The best degradation occurred in the presence of Na2SO4 (0.05 M) as conductive electrolyte. After 8 h, nearly complete degradation of nitrobenzene was achieved (88%) using BDD electrodes at pH = 3 and at current density equals 60 mA cm−2. The decay kinetics of nitrobenzene follows a pseudo-first-order reaction. Aromatic intermediates such as phenol, catechol, resorcinol, 1,2,4-trihydroxybenzene, hydroquinone and benzoquinone and carboxylic acids such as maleic glycolic, malonic, glyoxilic and oxalic, have been identified and followed during the nitrobenzene treatment by chromatographic techniques. From these anodic oxidation by-products, a plausible reaction sequence for NB mineralization on BDD anodes is proposed.

► Anodic oxidation using BDD is an effective method for degrading NB.
► The effect of operating parameters on the degradation was investigated.
► The main intermediate products were determined by HPLC technique.
► A plausible degradation pathway of nitrobenzene was proposed.