Turning waste into value: Banana peel biochar particle electrode boost methyl violet 2B dye removal in 3D-electrochemical system

Water-soluble cationic dyes pose significant risks to human health and aquatic ecosystems. However, conventional adsorbents and removal techniques are ineffective in eliminating them from wastewater. To address this challenging issue, we synthesized banana peel biochar (BPB) and unveiled its role as a particle electrode for the removal of carcinogenic methyl violet 2B dye (MV 2B) in a cutting-edge three-dimensional electrochemical system with the use of titanium (Ti) anode and graphite (GP) cathode (BPB–Ti/GP). Catalytic features of the BPB were explored and its electrochemical characteristics were studied through linear sweep voltammetry and cyclic voltammetry revealed a high oxygen evolution potential (OEP) of 1.86 V. High OEP of BPB particle electrode induced the MV 2B dye oxidation by reducing the oxygen evolution side reaction (OER) of the electrochemical system. At optimum operating conditions of the current density (j) of 5.2 mA/cm², pH 9.0, and Na₂SO₄ dose of 0.2 M, nearly 99.50 % of 10 mg/L MV 2B dye removal was attained in 40 min of electrolysis time. Compared to the BPB-Ti/GP system, the system with commercial particle electrodes (GAC, MnO₂, and Fe₃O₄) showed no significant performance. Energy consumption and electrical energy per order of BPB-Ti/GP system was also calculated. Furthermore, hydroxyl radical (^•OH) was identified as the dominant reactive oxygen species. Moreover, liquid chromatography-mass spectroscopy analysis showed that MV 2B underwent degradation through N-demethylation. This unique approach does not only reduce agricultural waste but also induce the sustainability of wastewater treatment processes, paving the way for greener environmental solutions.