Efficient Removal of Tartrazine Yellow Azo Dye by Electrocoagulation Using Aluminium Electrodes: An Optimization Study by Response Surface Methodology

This study investigates the efficiency of electrocoagulation (EC) in removing Tartrazine Yellow (TY) azo dye from synthetic wastewater using aluminium electrodes. The effects of current density, <i>i</i> (0.008–0.024 A cm⁻²), initial solution pH (3.0–7.0), and treatment time, <i>t</i> (10–50 min) on key process parameters, including pH, temperature (<i>T</i>), TY dye concentration (<i>c</i>) and removal efficiency (<i>R</i>), anode consumption, and sludge characterisation were studied. The experiments were conducted in a batch reactor according to the experimental plan developed in Design-Expert software, which was also used for the evaluation of the obtained results. As the EC process progresses, the removal efficiency of the TY dye increases, while the removal dynamics and the final value of <i>R</i> (ranging from about 28% to 99%) depend on the experimental conditions (<i>i</i>, initial pH, and <i>t</i>). A high <i>R</i>-value is reached faster with the application of higher current densities and lower initial pH. This is associated with a higher proportion of carbon and sulphur in the sludge (from the TY dye) after the EC process. Additionally, a mathematical model was developed to predict the experimental data. A numerical optimisation method using response surface methodology (RSM) was applied to determine the optimal operating conditions for TY dye removal. This resulted in the following conditions: pH = 3.37, <i>t</i> = 18.74 min, and <i>i</i> = 0.016 A cm⁻², achieving a removal efficiency of ≈70%.