Central composite experimental design for Indigo Carmine dye removal from solutions by applying electrocoagulation and electrooxidation processes

Indigo Carmine dye is a textile and food coloring dye reporting as toxic and harmfull for living creatures in the case of entrance to food chain above toxic levels. Sometimes textile and food industries produce toxic and harmfull dye-containing wastewaters that should be treated for safely discharge. The electrocoagulation (EC) and the electrooxidation (EO) methods for removal of dyes from wastewaters are being investigated for the last two decades. In this study, the Indigo Carmine dye removal was investigated by applying the EC and the EO methods. For this purpose, aluminum electrodes for EC and graphite plates for EO were used. The central composite experimental design was applied as the optimization method for the EC and the EO processes. The optimization parameters were selected as time (10-30 minutes), current density (0.4-2 Ampere/500 mL) and concentration (50-250 mg/L), natural pH (5.78-6.90) and room temperature (20-26.2 °C). The EO process was determined to be effective than the EC process. Statistically important parameters were concentration and time-current density interaction for the EC, but all the parameters were statistically unimportant for the EO. Dye removal percentages by the EC were calculated between 82.75% and 98.38%, and dye removal percentages by the EO were calculated between 46.88% and 100% for the experimental matrix. Electrical consumptions were a bit high for the EO than the EC. A column ion exchange process (Selion SBA 2000 resin) was applied to the dye residue after the EO treatment. From the oxidation reduction measurements, the treated solutions were determined as dischargeable.