Electrochemical detection of congo red dye and its complete removal from wastewater by photocatalytic and adsorption methods

For safeguarding water dwelling organisms and public health, it is an environmental and social obligation to detect and remove toxic dyes from polluted water. With this consideration, the current work presents the detection and removal of a representative dye (congo red) of the azo class. The detection objective was achieved by the designing of an electrochemical sensor comprising of multi-walled carbon nanotubes (MWCNTs) loaded over the surface of glassy carbon electrode (GCE). While the removal objective was achieved by using graphene oxide (GO) nanosheets as adsorbent and BaO nanoparticles as photocatalyst. The designed sensing platform was found highly sensitive for congo red detection as authenticated by the LOD value of 0.1 nM. Congo red was photocatalytically removed from wastewater using BaO nanoparticles. The photocatalytic degradation led to 95% removal in 90 minutes under acidic conditions. Adsorption method was also used for wastewater purification from congo red. The adsorption results leading to 100% removal of the dye were modeled to assess the mechanisms and kinetics of adsorption. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize both modified and bare glassy carbon electrodes. The CV results demonstrated that the modified GCE exhibited a larger surface area compared to the unmodified GCE, while the EIS revealed efficient charge transfer through MWCNTs/GCE as compared to the bare GCE. This research presents the first report on a sensing platform that combines adsorptive and photocatalytic methods, for efficient sensing and complete removal of congo red dye from wastewater.