TiO₂-SiO₂/GAC particles for enhanced electrocatalytic removal of acid orange 7 (AO7) dyeing wastewater in a three-dimensional electrochemical reactor

In this work, granular activated carbon (GAC) supported TiO₂-SiO₂ oxide (TiO₂-SiO₂/GAC) was prepared and packed in a three-dimensional electrochemical reactor (3DER) for the removal of acid orange 7 (AO7) dyeing wastewater. The characteristics and the electrocatalytic performance of the prepared TiO₂-SiO₂/GAC were investigated to verify the feasibility of TiO₂-SiO₂/GAC application as particle electrodes. Results show that the TiO₂-SiO₂/GAC could significantly improve the AO7 removal efficiency, extend service life of particle electrodes, and enhance the stability of 3DER system. Orthogonal array was designed to optimize the operation parameters of 3DER, which was determined as electric field intensity 1 V/cm, filling amount of TiO₂-SiO₂/GAC particles 200 g/L, electrolytic concentration (Na₂SO₄) 0.07 mol/L, pH 3, treatment time 120 min. Under the optimal condition, the AO7 decolorization rate and COD removal efficiency are 83.20% and 48.95% respectively. The possible intermediates generated in 3DER during AO7 decomposition were identified and the biodegradability of the effluent was also estimated. Results suggest that the 3DER with TiO₂-SiO₂/GAC particle electrodes could be an alternative for the pretreatment of dyeing wastewater before biological treatment.