Conceptualizing Cavigulation Methodology by Integrating Cavitation and Coagulation and Application to Dye Wastewater Treatment

Abstract

The present work provides a proof of concept for a new hybrid process, cavigulation, by combining cavitation and coagulation and its application to dye wastewater treatment. Both acoustic and hydrodynamic cavitations were evaluated. Removal of a commonly used dyes such as Congo red was investigated by cavigulation in the concentration range of 50 to 500 ppm. A broad spectrum of coagulants including two inorganic coagulants; poly aluminium chloride, iron (III) chloride, and natural biocoagulants derived from Moringa oleifera, Cicer arietinum and Acanthocereus tetragonus were employed to substantiate the concept of cavigulation. A vortex diode device employing vortex flow for cavitation, was used for the hydrodynamic cavitation (HC) -based cavigulation. Cavigulation in the form of acoustic cavitation + coagulation, showed significant improvement over individual processes; acoustic cavitation alone was largely ineffective for dye removal. Increase over conventional coagulation to the extent of 24% and 48% was observed for the two inorganic coagulantsIron (III) chloride and PAC SAB 18, while for Moringa oleifera, Acanthocereus tetragonus, and Cicer arietinum the increase was 27%, 33%, and 29% respectively. The pH has a large impact on the cavigulation process, similar to coagulation and the coagulant dose could be reduced by more than half by adjusting pH to 3. Auramine O dye removal was effective using hydrodynamic cavitation compared to coagulation. The developed cavigulation process, especially using biocoagulants, could be an effective alternative to the conventional chemical coagulation in the form of a green process in dye wastewater treatment