Assessing the impact of dye characteristics on electrocoagulation efficiency in synthetic textile wastewater: An RSM-based study

Abstract

   This new study investigates the effect that dye type cationic Methylene Blue (MB) and anionic Congo red (CR) that has on the Electro-coagulation (EC) treatment performance of synthetic wastewater by employing Response Surface Methodology-Central composite design (RSM- CCD) optimization technique. Twenty-seven experiments were performed to analyze and optimize the effects of 4 factors: Current Density (mA/cm²) = 6.67 - 13.33; Initial pH = 2 – 10; Reaction Time (h) = 0.07 – 1.5; and Chemical Oxygen Demand (COD mg /L) = 840 – 4236.67 mg/L. The efficiency of EC treatment is evaluated in terms of COD reduction as primary response variable. The RSM model accomplish an excellent predictive power (R2=98.84%; adjusted R2=97.48%); the experimental results illustrated a significant relationship between the estimated and measured values. The ANOVA analysis indicated that both current density and reaction time were primarily responsible for the most considerable effects on COD reduction. Furthermore, the study found that the initial pH had a critical role in forming and maintaining coagulating species. A maximum COD reduction efficiency of 98.14% was obtained under the best operating conditions as follows; current density of 11.11 mA/cm²(optimal), pH = 6 (initial) and reaction time = 1.5h and initial COD concentration of 2510 mg/L which also utilized only 8.89Wh / kg COD of the applied electrical energy. Many responses also had been tracked in this study to reflect the complex interaction between the operational variables and the final solution properties and its characteristics. The investigated properties changes were the final temperature, conductivity, voltage of the solution, in addition to the theoretical consumption of anode and specific energy consumption. A complex synergistic effect had been reported during the track of the solution characteristic, and this can be relied on the effect of dyes negative and positive charges that reflect some unusual behavior in comparison to the removal of single dyes, or dyes mixture of the same type.