Electrochemical remediation of Reactive Black 5 (RB5) dye: A novel approach with tanks in a series (TIS) model with dimensionally stable anodes (DSA) and boron doped diamond (BDD) anodes

• Eight DSA were prepared indigenously by STD and PPTD methods with a mixture of transition and noble metal oxides • Electrochemical treatment of synthetic wastewater performed using prepared DSA and commercial BDD in three tanks in a series (TIS) • The performance of the anodes was compared in terms of crucial parameters, such as, ICE, EC, MCE, MTC, and kinetic rate constants The three tanks-in-series (TIS) model is a well-established approach and is extensively utilized in industrial process synthesis. Despite its proven applicability the potential of the TIS model remains underexplored in the domain of wastewater treatment, where it could offer valuable insights. The present work focuses on the TIS model as a continuous process for treating wastewater containing Reactive Black 5 (RB5) dye using indigenously prepared mixed metal oxide-coated anodes. Within the electrode development phase, diverse DSAs were fabricated through standard thermal decomposition (STD) and polymeric precursor thermal decomposition (PPTD) techniques. These methods involved coating Ti substrates with a blend of transition and noble metal oxides. They are mainly Ru-Sn-Sb-Ni, Ru-Sn-Sb-Ir, Ru-Sn-Sb-Ta, and Ru-Sn-Sb-Pt. Then, indigenously prepared electrodes were employed for 100 mg/L RB5 dye wastewater for color, Chemical Oxygen Demand (COD), and Total Organic Carbon (TOC) reduction. Additionally, the performance of prepared electrodes was compared with commercially proven Nb/BDD and Si/BDD anodes for instantaneous current efficiency, energy consumption, mineralization current efficiency, mass transfer coefficient, and kinetic rate constants. Out of all the electrodes tested, the one composed of Pt-Ru-Sn-Sb proved to be the most effective for dye removal. It was subsequently assessed at various flow rates in a continuous process. In this comparison, a continuous process with a combined mode of operation using DSA and BDD anodes was found to be efficient for higher dye removal with lower energy requirements. The continuous operation in TIS model is extended for industrial wastewater to reduce color, COD, and TOC.