Electrochemical Degradation of Methylene Blue Using Ce(IV) Ionic Mediator in the Presence of Ag(I) Ion Catalyst for Environmental Remediation

Sains Malaysiana 2021 Methylene blue (MB) is often used in textile industries and is actively present in the wastewater runs-off. Recently, mediated electrochemical oxidation (MEO) offers a fast, reliable and promising results for environmental remediation. Thus, we aimed to evaluate the electro-degradation potential of MB by MEO using Ce(IV) ionic mediator. Furthermore, we also observed the influence of addition Ag(I) ion catalyst in MEO for degradation of MB. The electro-degradation of MB was evaluated by cyclic voltammetry technique and was confirmed by UV-Vis spectrophotometry, high performance liquid chromatography (HPLC) analysis and back-titration analysis. The results showed that in the absence of Ag(I) ion catalyst, about 89 % of MB was decolorized within 30 minutes. When 2 mM of Ag(I) ion catalyst was applied, the electro-degradation of MB was increased to maximum value of 100%. The UV-Vis spectrum confirmed the electro-degradation of MB as suggested by decreased maximum absorbance value at {\lambda} 668 nm from 2.125 to 0.059. The HPLC analysis showed the formation of five new peaks at retention time of 1.331, 1.495, 1.757, 1.908 and 2.017 minutes, confirming the electro-degradation of MB. The back-titration analysis showed about 52.9% of CO2 was produced during electro-degradation of MB by MEO. More importantly, more than 97% of Ce(IV) ionic mediator were recovered in our investigation. Our results reveal the potential of MEO using Ce(IV) ionic mediator to improve the wastewater runs-off quality from textile as well as other industries containing methylene blue.