Potential of Green Nanoemulsions in Removal of Congo Red from Aqueous Solution

Abstract

In the present study, potential of green nanoemulsions in the removal of Congo red (CR) from aqueous solution was investigated. Nanoemulsions were prepared by low energy emulsification technique using ethyl acetate (EA), Triton-X100, ethylene glycol (EG), and water. Nanoemulsions were characterized for thermodynamic stability, self-nanoemulsification efficiency, droplet size, polydispersity, viscosity, refractive index, and transmittance. Adsorption studies were carried out for contact time of 10, 15, and 20 min. The influence of contact time and EA & Triton-X100/EG concentrations on droplet size, viscosity, and % CR removal was also investigated. It was observed that droplet size, viscosity, and % CR removal were significantly influenced by EA and Triton-X100/EG concentrations. However, contact time had negligible/little impact on % CR removal. Based on the lowest droplet size (14.3 nm), lowest viscosity (11.4 cp), and highest % CR removal efficiency (91.6%), the nanoemulsion F7 containing 5% w/w of EA, 33.3% w/w of Triton-X100, 16.7% w/w of EG, and 45% w/w of water was optimized as the best formulation for the removal of CR from its bulk aqueous solution. These results indicated the potential of green nanoemulsions in the removal of toxic dyes such as CR from its aqueous solution via liquid-liquid adsorption.