Thermodynamic modeling of density, viscosity and critical micelle concentration of aqueous Tween and Span solutions via Cubic plus association equation of state

• The CMCs of Span 60, Span 80, Tween 60, and Tween 80 were modeled via CPA EoS. • Tweens and Spans were modeled for the first time considering 3 × 2B association scheme. • Liquid mixture viscosity and density were predicted marvelously at different temperatures. • Liquid mixture viscosity was compared using FT, FVT, LBC, and Assael models via the CPA predicted density. The Cubic Plus Association (CPA) equation of state (EoS) has been offered to separately compute different thermodynamic properties of the aqueous non-ionic surfactant solutions, including Tween 80, Tween 60, Span 80, and Span 60. These surfactants have been modeled for the first time, and 5 pure components parameters of the CPA EoS have been fitted to the Critical Micelle Concentration (CMC) data at various temperatures. Tweens and Spans surfactant molecules have been modeled as associating constituents via considering 3 × 2B association scheme. Furthermore, applying the adjusted parameters, the liquid mixture density of the noted aqueous solutions has been predicted marvelously at various temperatures. Moreover, the liquid mixture viscosity has been compared reasonably using four different theories at ambient conditions. Besides, the effects of temperature have been investigated in the case of liquid mixture viscosity. Additionally, several new correlated equations have been introduced considering the optimized parameters of non-ionic surfactants.