Comparative investigation of electrocoagulation performance using zinc and aluminium electrodes for food azo dye water treatment

Abstract This study was performed to evaluate the efectiveness of electrocoagulation (EC) process with both zinc (Zn) and aluminum (Al) electrodes for the elimination of decolorization efficiency (DE) and chemical oxygen demand (COD) from Cochineal Red A (E124) azo dye removal. Each electrode had a total surface area of 40 cm 2 , with a submerged area of 30 cm 2 . At current density and reaction time of 30 mA/cm 2 and 90 min for Zn, and 40 mA/cm 2 and 60 min for Al with a reel pH solution 7.10, and an ambient temperature (20 °C), an initial E124 dye concentration of 50 mg/L, using Zn electrodes, removal rates of 72 % for DE and 55 % for COD were achieved, while Al electrodes yielded higher efficiencies of 97 % and 90 %, respectively. The DE and COD removal results obtained using the Al electrode were best fitted by the Freundlich isotherms and follows the first-order reaction kinetics. Thermodynamic parameters indicated that adsorption occurred spontaneously, exhibiting endothermic behaviour. Operating cost for treating E124 dye solution at 40 mA/cm 2 and 60 min with Al electrode materials was estimated 0.979 $/m 3 . Analysis by HPLC-MS revealed that E124 progressively degrades during electrocoagulation with an Al electrode, leading to the formation of transformation products. The sludge formed after EC treatment with Al electrode was characterized by SEM coupled to EDS, XRD and FTIR exhibited surface irregularities. These findings demonstrate the high efficiency of the EC process for DE and COD removal and provide preliminary insights into the potential reuse of the generated sludge, which requires confirmation through leaching and toxicity tests.