The dissertation is focused on the solving of important scientific and applied problem on the development of chrome-saving leather tanning technology using modified montmorillonite dispersions for qualitative formation of leather structure and properties along with reducing the burden on the environment. In order to develop the chrome-saving leather tanning technology it was suggested to use montmorillonite dispersions, sequentially modified with alkaline peptizers and basic chromium sulfate. The colloid-chemical properties of modified montmorillonite dispersions in terms of kinematic viscosity, pH and adsorption level of the modifier were studied. It is shown that the interaction of montmorillonite with chromium compounds affects the aggregative stability of dispersions. It is also accompanied by charge effects and changes the electrokinetic properties of the mineral surface. It was shown a high level of adsorption of hydroxochrome complexes on the surface of mineral particles at the concentration of 10-15 % Cr2O3 as a result of montmorillonite dispersions modification. The dispersion of montmorillonite, modified with hydroxochrome complexes, shows high stability in the range of pH 3-4, due to chemical interactions between the active centers of the mineral and the functional groups of the chromium tanning agent.
The chemical and physicochemical interaction between the functional groups of collagen and the active centers of modified montmorillonite in the system «collagen–chromium complex–montmorillonite» was proved. The formation of hydrogen bonds O-C-O and CH2-groups of protein with surface hydroxyl groups of montmorillonite type Si-O...H-C and Si-O-H...O-C was established. The formation of hydrogen bonds between the nitrogen atoms of the amino groups of gelatin and the proton of water in the interlayer space of montmorillonite with cations in the exchange complex of the mineral is possible. Combined treatment of gelatin with chromium compounds and modified montmorillonite has a significant change in the redistribution of oscillation intensities of active groups. This helps to form effectively the volume of the dermа, the extraction of chromium salts from the solution and increase the shrinking temperature of the leather. The rational amount for structuring the collagen of the derma is the consumption of montmorillonite 3-4 % by weight of protein, chromium (III) compounds 10 % by weight of the mineral. The adding of modified montmorillonite is appropriate at the stage of chromium tanning due to the formation of additional bonds in the structure of the derma and the interaction of chromium compounds and the modified surface of the mineral with collagen. This provides a qualitative formation of the structure of the dermis, increasing the leather area by 4,2-4,9 %; thicknesses of 0,9-3,5 %; volume yield by 17,0-18,0 %; reaching the shrinking temperature of 103 °C; increase of tensile strength by 4,5 %, decrease of elongation at load of 10 MPa and rupture by 13,1 and 7,0 %, respectively. The combined use of chromium compounds and modified dispersions of montmorillonite for leather tanning can reduce the amount of chromium compounds by 17-20 %; to improve the degree of its absorption by 14 % and to reduce the concentration of chromium compounds in the spent liquids by 30 %. The increase in the absorption efficiency of chromium compounds by the dermis is due to the presence of montmorillonite, which has a highly developed adsorption surface and can create additional active centers in the derma structure for binding to chromium compounds, thereby reduce the burden on the environment. The effectiveness of the use of modified montmorillonite during chromium tanning and greening of the process was confirmed by the study of biological and chemical oxygen consumption. According to calculations of chrome-saving leather tanning technology the optimal consumption of chromium compounds is 1,0 % in terms of Cr2O3 by weight of pelt and 2,5 % of modified montmorillonite in terms of dry mineral. The total consumption of chromium compounds is 1,25 %. The developed chrome-saving leather tanning technology provides effective formation of the dermis structure and leather performance with reduced consumption
of chromium compounds and the combined use of modified montmorillonite. The expected economic effect of the implementation is UAH 1330 per 100 m2 of leather due to savings in raw materials and chemical reagents.
