Lead Oxide Modified Graphite Electrodes for Electrochemical Degradation of Congo Red Dye in Aqueous Solution

Abstract

Congo red (CR) dye in aqueous solution was decolorized by an electrolysis process using graphite (G) and lead dioxide modified graphite (G/PbO₂) as anode materials in a two-electrode batch reactor. The electrodeposited lead dioxide film was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and atomic force microscopy (AFM). Comparative performance assessment of the anode materials under different process parameters reveals that the lead dioxide film improved the electrocatalytic effect of the modified electrode. The adjustment of the deposition bath pH from 1.5 to 3 resulted in the formation of uniform agglomeration and disappearance of particulates, while addition of sodium dodecyl sulphate (SDS) gave better adhesion of film to substrate. The degradation rate (DR) observed for the G/PbO₂ (1.0 × 10⁻² cm²) was higher than that of the unmodified electrode (0.87 × 10⁻² cm²). Increase in applied voltage from 25 to 30 V at 23 mA/mm² improved the degradation efficiency (DE) from 84.7% to 91.32% for graphite and from 96.09% to 99.98% for G/PbO₂, with 0.5 M KCl. The prime degradation time of 45 min was recorded for graphite anode which reduced to 30 min for G/PbO₂ anode. CR degraded to compounds with smaller molecular weight and better stability as observed from GC-MS analysis and computational total energy study, respectively. The modification of the graphite electrode surface by electrodepositing PbO₂ film improved the DE and the prime reaction time. These findings present significant suggestions for the design of advanced electrodeposition and electrocatalytic systems for wastewater treatment applications.