Application of Response Surface Methodology for the Optimization of Basic Red 46 Dye Degradation in an Electrocoagulation-Ozonation Hybrid System

Abstract

The release of synthetic dyes like Basic Red 46 (BR46) from industrial wastewater has raised growing concerns due to their toxicity, long-term persistence, and resistance to standard biological treatment methods. In this work, we developed and tested a pilot-scale electrocoagulation-ozonation (EC-O) hybrid system aimed at removing BR46 from aqueous solutions. The system integrates electrocoagulation, using iron electrodes, with ozone-based advanced oxidation processes, facilitating a combination of coagulation, adsorption, and oxidative breakdown of dye molecules. The response surface methodology (RSM) with a central composite design (CCD) was applied to optimize the treatment process, focusing on five variables: current density, flow rate, ozone dosage, ozonation time, and initial dye concentration. The quadratic model exhibited strong predictive power, with an adjusted R² of 0.9897 and a predicted R² of 0.9812. The optimal conditions identified included a current density of 70 A/m², flow rate of 1.6 L/min, ozone dose of 2.0 g/h, and an ozonation time of 20 min, achieving a predicted removal efficiency of 91.67% for a solution with BR46 at an initial concentration of 300 mg/L. Experiments conducted under these conditions confirmed the model's reliability, with observed removal rates exceeding 90% and deviations under 2%. The EC-O system had a treatment capability of 26.19 L/h and an energy consumption of 3.04 kWh/m³. These findings suggest that the EC-O system is an effective and scalable option for treating dye-contaminated wastewater, offering faster and more efficient results than conventional techniques.

Keywords: Basic Red 46; azo dye removal; electrocoagulation–ozonation; pilot-scale study; response surface methodology.

Figure 1

Normal plot of residuals (A), Box-Cox plot for power transform (B), residual versus predicted plot (C), and plot of predicted versus actual values of BR6 removal efficiency (D).

Figure 2

Three-dimensional response surface plots illustrating the effects of operational parameters on BR46 removal efficiency: (A) interaction between current density and flow rate; (B) interaction between current density and ozone dose; (C) interaction between current density and ozonation time; (D) interaction between current density and initial BR46 concentration.

Figure 3

Three-dimensional response surface plots showing the interactive effects of operational variables on BR46 removal efficiency: (A) flow rate and ozone dose; (B) flow rate and ozonation time; (C) flow rate and initial BR46 concentration; (D) ozone dose and ozonation; (E) ozone dose and initial BR46 concentration; (F) ozonation time and initial BR46 concentration.

Figure 4

Schematic of pilot-scale EC–O system used for BR46 removal.