Kolloidnyj žurnal

An express method of solvent-free mechanochemistry using fine grinding in air for 3 and 6 minutes in a mill (0.94 kW; 26,000 rpm) is employed to targetedly change in the structure of kaolin and increase its sorption capacity. During the same process, kaolin is modified together with hydrolytic lignin to hydrophobize its surface and improve its sorption properties. The influence of mechanical activation on the structure and properties of kaolin, hydrolytic lignin and their composites based with different component ratios is studied using electron microscopy, X-ray diffraction, infrared spectroscopy, low-temperature nitrogen adsorption and UV absorption spectroscopy. The dense structure of kaolinite remains preserved, hydrogen bonds in hydrolytic lignin are ruptured and the number of carbonyl groups increases, and fragments of natural polymer are grafted to kaolinite. It has been found that an aggregation-agglomeration microstructure is formed in the composites. Kaolin, as well as the composite of kaolin and hydrolytic lignin with a mass ratio of 10 : 1, treated with a mechanical energy dose of 0.83 kJ · g⁻¹, exhibited significant changes in structure and demonstrated relatively high sorption characteristics. The Brunauer-Emmett-Teller specific surface area of this sorbents is ~ 16 m² · g⁻¹, the adsorption of bovine serum albumin are 83.63 and 44.10 mg · g⁻¹, respectively. Thus, the dry mechanical activation in air under ‘mild’ conditions makes it possible to increase the sorption of bovine serum albumin of kaolin by 104%.

The samples of magnetic liquid stabilized by a double layer of surfactant in water using non-ionogenic stabilizer TWEEN 20 (Polysorbate 20) as the second layer were synthesized. The rheological properties of the synthesized samples depending on their concentration were investigated. In contrast to liquids with dissociated surfactant, the viscosity of the magnetic liquid decreases faster with temperature increase than the viscosity of the base medium (water). The main advantage of using non-ionogenic surfactant is the possibility of synthesizing low-temperature magnetic liquids based on water-alcohol mixtures and aqueous salt solutions. Fluids stabilized by TWEEN 20 in ethylene glycol and propylene glycol solutions retain mobility up to temperatures –40°C and –50°C. When calcium chloride CaCl₂ solution was used as a base medium, the test sample of the fluid retained performance up to temperature –30°C. Magnetic liquids based on alcohol and salt solutions can be indispensable in the fields of engineering, where strict requirements are made to their fire and environmental safety. Chemical passivity of particles stabilized by TWEEN 20 makes their application in biology and medicine possible.

Tensionetric and dilatational rheological characteristics of solutions of dicationic diimidazolium surfactants mixtures with extremely short spacer fragments and anionic surfactants (sodium dodecyl sulfate, sulfonol, sodium 3-laureth sulfate) at the interface with air were studied using the pendant drop and oscillating drop methods. The nature of interaction between dicationic and anionic surfactants depends on the structure of the anionic surfactant molecules. The possibility of forming strong complexes between a dicationic surfactant with 4 methylene groups in the spacer fragment and sodium dodecyl sulfate with the component ratio close to 1 : 1 was shown. It was found that the resulting complexes are stable in the neutral and slightly acidic pH range.