Study of the colloidal chemical properties of aqueous solutions of polysaccharides

Objectives. The work set out to study the colloidal chemical properties of polysaccharides, representing biodegradable high-molecularweight compounds (HMWCs). Such properties are relevant when attempting to meet the requirements of green chemistry when protecting engineering equipment from fouling with crystals of carbonates and sulphates of alkaline earth metals. Various scale inhibitors used for this purpose include polymers, surfactants, complexing agents, and systems based on organic phosphoric acids. Methods. Capillary viscometry was used to determine the average molecular weights of polysaccharides and the concentration dependencies of the viscosity of solutions of HMWCs. Using the tensiometric (Du Noüy ring) and sessile drop methods, the adsorption properties of polymers at the solution–air interface were assessed to calculate the parameters of the adsorption layer. Rheological properties were investigated via rotational viscometry. Results. For aqueous solutions of unmodified and modified polysaccharides, including arabinogalactan (AG), carboxymethyl cellulose, hydroxymethyl cellulose (HMC), and sodium carboxymethyl inulin (Na CMI), the intrinsic viscosities were determined using the graphical method. The calculated average molecular weights range from M = 80 · 10 3 g/mol (for AG) to M = 16 · 10 5 g/mol (for Na CMI). Surface activity was detected for Na CMI in aqueous solutions, adsorption calculations for the solution–air interface were performed based on the surface tension isotherm using graphical differentiation, and the parameters of the adsorption layer were calculated. These parameters describe the limiting adsorption A ∞ and area S 0 occupied by the macromolecule in the surface layer. According to the results of rheological studies, dispersions and solutions of polysaccharides are characterized by thixotropic properties and irreversible flow. Conclusions. The physicochemical properties of aqueous solutions of polysaccharides were obtained in the concentration range 0.5 · 10 −3 –2 · 10 −3 wt %. According to the viscosity values of AG, HMC, and Na CMI solutions, this concentration range is preferred for use in heat engineering equipment. According to the determined parameters of the adsorption layer at the solution–air interface, Na CMI is shown to exhibit surface activity. The rheological studies revealed structure formation in polysaccharide solutions in the studied concentration range.