Comparison of 2D and 3D electrochemical oxidation systems for removal of reactive dyes in water

In this study, the integration of granular activated carbon (GAC) in a traditional electrochemical oxidation (EO) system enhanced the removal efficiency of reactive dyes in wastewater. A two-dimensional (2D) EO model using a 20V-5A DC power supply and a mixed metal oxide (MMO) electrode was employed for the oxidation of SRH-Red and SBH-Blue reactive dyes in water. This 2D EO system was then upgraded to a three-dimensional (3D) EO system by adding a GAC column, which acts as a particle electrode. The effect of environmental factors (e.g., pH, electrolyte, electrolysis time, and GAC) on the dye removal efficiency was investigated for both 2D and 3D EO systems. Results showed that 3D EO was more efficient than 2D EO for removing reactive dyes in terms of removal efficiency, electric energy consumption, and reaction rate constant. The appropriate EO condition for 3D EO system was found at electrolyte concentration of 3 g/L of NaCl and 16 g/L of GAC, where the removal efficiency reached 93.13% at pH = 3 for SRH-Red (100 mg/L) and 94.04% at pH = 4 for SBH-Blue (200 mg/L) after 20 min of reaction. The Fourier-transform infrared spectroscopy results before and after treatment confirmed the functional groups and cyclic structures of the reactive dyes were decomposed and converted into simpler structures. Therefore, 3D EO is an innovative alternative with excellent efficiency of removing reactive dyes from the water matrix.