The electrochemical degradation of malachite green with lead dioxide electrodes by pulse current oxidation methods

Abstract

The pulse current oxidation methods were used to degrade the malachite green (MG) using lead dioxide as anodes. The influences of operating parameters, including pulse frequency, pulse current density and pulse duty cycle, on the MG removal efficiency were investigated. The results indicate that MG removal efficiency can reach 99.6% after 90 min with the pulse frequency at 10 Hz, pulse current density at 30 mA cm−2 and pulse duty cycle at 0.6. The pulse degradation processes follow the pseudo-first-order kinetics. Comparison with direct current oxidisation methods, pulse oxidisation methods can enhance MG and COD removal efficiency and reduce the energy consumption. Moreover, pulse oxidisation methods can increase the amount of hydroxyl radicals generation and reduce side reactions (such as oxygen evolution) in the degradation process of MG. Finally, a possible degradation pathway of MG in pulse current modes was proposed based on the intermediate products identified by GC/MS.