Transforming waste to purity: 3D electro-Fenton process boosted with pistachio shell-derived iron-biochar electrode for methyl violet 2B dye catalytic removal

Traditional degradation methods with typical catalysts which have limited negatively charged surfaces are not effectively degrade cationic dyes. A multi-functional iron-biochar was prepared from waste pistachio shells (Fe@PSB) that offers enhanced dye removal due to abundance of negatively charged sites for the degradation of the carcinogenic dye known as methyl violet 2B (MV 2B) in a cutting-edge three-dimensional electrochemical Fenton system (3DEF) with graphite (GP) cathode and Titanium (Ti) anode (3DEF-Ti/GP). Catalytic properties of Fe@PSB were explored for MV 2B dye degradation at broad acidic pH range. At optimum operating conditions of the current of 2.0 A, pH 5.0, and Na2SO4 dose of 0.2 M, nearly 98.8% of 10 mg/L MV 2B dye removal was attained in 60 min of electrolysis time. Commercial particle electrodes did not perform as well for the MV 2B dye degradation. The catalytic mechanism of 3DEF-Ti/GP system was investigated by quenching experiments which revealed that the hydroxyl radical ( • OH) was responsible for the oxidation of dye molecules. Fe@PSB significantly performed up to four successful cycles. Liquid chromatography-mass spectrometry analysis revealed that de-methylation was the primary degradation pathway. This unique approach not only valorizes agricultural waste but also paving the way for greener environmental solutions. • It is the first instance that electro-catalytic MV 2B dye removal was studied in the 3DEF-Ti/GP system. • Iron addition in PSB raised the removal efficiency of MV 2B dye from 90.46% to 98.8%. • Fe@PSB particle electrodes contained multifunctional groups over PSB particle electrode. • 3DEF-Fe@PSB particle electrode performed up to four successful cycles than the PSB particle electrode.