Removal of Reactive Blue 19 using nonionic surfactant in cloud point extraction

• Reactive Blue 19 dye was investigated as a pollutant model in aqueous solutions.
• Nonylphenol polyethoxylate was used in cloud point extraction experiments.
• Influence of temperature and surfactant and dye concentrations were evaluated.
• Equilibrium data were represented by the Langmuir model.
• Coacervate volume and efficiency increases with surfactant concentration.

Textile wastewater represents a serious environmental issue due to the presence of toxic dyes. The cloud point extraction, which involves the application of nonionic surfactants at temperatures above the cloud point, was applied in this research to remove Reactive Blue 19 dye from a synthetic wastewater. Nonylphenol with 9.5 ethoxylation degree was used as nonionic surfactant. Dye removal was evaluated considering the influence of surfactant concentration, temperature, and initial dye concentration. Equilibrium data followed the Langmuir isotherm model. Negative Gibbs energy, enthalpy, and entropy showed that the process was spontaneous and exothermal. Dye removal reached 91% when using 7.5 wt% surfactant, at 65.0 °C. Cloud point extraction can be used as an efficient alternative for treating textile wastewater containing Reactive Blue 19.