Investigation of Photo-Electrocoagulation Process Using an Optimized Cathode for Azo Dye Removal; Case Study on Direct Red 80

Background Anionic direct dyes, extensively used across various industries, are among the major sources of colored wastewater discharged into the environment annually. Such azo dyes are non-biodegradable and highly resistant to environmental factors. Due to their complex molecular structures, azo dyes are non-biodegradable and exhibit high resistance to conventional environmental treatments. This study aims to evaluate the efficiency of the photo-electrocoagulation (PEC) process using an optimized cathode for the removal of Direct Red 80 (DR80), a representative azo dye, from aqueous solutions. Materials and Methods The study was conducted in the laboratory setting, using a Photo-Electrocoagulation reactor with a volume of 500 ml, to analyze the effects of current density, electrolysis treatment time, and electrolyte concentration variables on the removal efficiency variable. This was conducted using the design of experiments (DOE) methodology and the Design-Expert software. In a later stage, the impacts of dye density and pH on removal efficiency were also investigated. Findings: The results demonstrated that increased current density, electrolysis time, and electrolyte concentration significantly enhanced dye removal efficiency. Under optimal conditions including current density of 296 mA/cm², electrolysis time of 10 minutes, and electrolyte concentration of 720 mg/L, a maximum removal efficiency of 98.21% was achieved. Conclusion An increase in dye density leads to a decrease in removal efficiency. Meanwhile, the removal efficiency increases upon a decrease in the level of pH. The highest amount of removal is achievable at a pH value of less than 4, indicating an acidic solution. Thus, the photo-electrocoagulation process is an effective method for the treatment of colored wastewater.