Ionic Dye Removal Using Solvent-Assisted Ionic Micellar Flocculation

The environmental impacts caused by dyes in industrial wastewater are incalculable, due to their adverse effects on the ecosystem and human life, especially when discarded at illegal levels. The ionic micellar flocculation process to remove metals and organic compounds has proven to be an innovative and efficient alternative in the removal of pollutants from aqueous solutions. In this respect, an anionic surfactant, composed of a mixture of surfactants derived from coconut oil and animal fat, was used to remove the ionic dyes methylene blue (MB) and Acid Red 57 (AR57) from an aqueous medium. During extraction trials, the use of a soap base anionic surfactant at concentrations below the critical micelle concentration (CMC) promotes the formation of an insoluble surfactant (cationic dye-anionic monomer), acting as an ionic flocculant by monomers. On the other hand, at concentrations above the CMC, adding calcium ions to an aqueous solution allowed the formation of micellar flocs capable of removing dye, reaching maximum extraction percentages of 60% of MB and 90% of AR57. The influence of initial dye concentration, surfactant concentration, pH and the presence of electrolytes demonstrated that the interaction mechanisms between the dyes and micelles are based on electrostatic interactions and/or micellar solubilization, confirmed by determining the diameter of micellar aggregates. Solvent-assisted ionic micellar flocculation was applied to increase MB removal efficiency from 26 to 91%.