Comparison of electrocoagulation and physicochemical coagulation/ flocculation in the treatment of synthetic textile wastewater

Abstract

This study aimed to compare the efficiency of coagulation/flocculation and electrocoagulation treatments applied to synthetic textile wastewater containing navy blue dye (AM-16). For the coagulation/flocculation process, polyaluminum chloride (PAC 18%) and aluminum sulfate (Al2(SO4)3) were used as coagulants, and cationic polymer (CP) as a coagulation aid. Coagulation/flocculation treatments were assessed at the concentrations of 150–350 mg L-1 for dye, 10–50 mg L-1 for PAC 18%, and 0.1–0.5 mg L-1 for CP, with initial pH ranging from 5 to 9. The same ranges were applied for the Al2(SO4)3 tests, except for initial pH, which ranged between 4 and 8. Aluminum electrodes were used for electrocoagulation, as well as the same dye concentration range (150–350 mg L-1) and applied current of 0.3–0.9 A. The response variables were contaminant (AM-16) removal, color removal, chemical oxygen demand, total organic carbon, and reduced toxicity using the microcrustacean Artemia salina as bioindicator. The aim was to compare the performance of different treatment methods (coagulation/flocculation and electrocoagulation) and assess how all independent variables and their interactions affected process efficiency. The results obtained through statistical analysis demonstrated that the most influential factor in coagulation/flocculation in removing AM-16 dye concentration was the initial pH, for both PAC 18% and Al2(SO4)3. However, for aluminum sulfate, dye concentration also had an influence, indicating that an increase in pH and dye concentration favored the removal of contaminant. With respect to wastewater toxicity after treatments, there was a maximum average reduction of approximately 11% for treatment with Al2(SO4)3. Electrocoagulation showed no significant variables at the levels studied but good average performance in removing dye (83.68%) and color (95.1%) from the wastewater. Both treatments (coagulation/flocculation and electrocoagulation) demonstrated efficiency for the variables studied and their levels. However, coagulation/flocculation performed better considering the removals obtained in the set of response variables assessed.