The phase separation, interaction forces and thermodynamics of sodium alginate and TX-100 mixture in the manifestation of alcohols: UV–visible and cloud point measurement studies

Abstract

Triton X-100 (TX-100 (a nonionic surfactant)) is widely applied to separate proteins from cell membranes while sodium alginate (SA; a biopolymer) has the usages as an ingredient in foods, fertilizers, textiles, pharmaceuticals items, etc. The clouding behaviors of the TX-100 + SA mixture have been investigated in the presence of different alcohols media. For the TX-100 + SA mixture in aq. alcohols environment, the observed cloud point (CP) values were found to enhance with the raising in concentration of alcohols and follow the order: CP2-PrOH > CP1-PrOH. > CPEtOH > CP2-BuOH. The standard free energy (ΔGc0), enthalpy (ΔHc0), and entropy (ΔSc0) of the clouding behavior of the employed TX-100 + SA mixture have been measured. The Gibbs free energy (ΔGc0) values were positive and reduced as the concentration of alcohols increased. Hence, the cloudy development of TX-100 + SA was non-spontaneous in nature. The magnitudes of enthalpy (ΔHc0) along with entropy (ΔSc0) were achieved positive in most of the systems while those were negative at the higher ethanol and butanol concentrations. The relevant transfer energies along with enthalpy–entropy compensation variables of clouding phenomena have been calculated and discussed in detail. The binding of TX-100 with SA in aq. EtOH/1-PrOH media was studied by means of a UV–visible spectroscopic tool while the binding constant (Kb) was determined using Benesi-Hildebrand plot. The Kb values are dependent on the study temperature and composition of the solvents. The hydrophobic, hydrogen bonding, and electrostatic interactions are recommended as the significant binding forces between TX-100 and SA.