OPTIMIZATION OF PROCESS FOR PRODUCTION OF NANOCRYSTALLINE CELLULOSE AND ITS COMPOSITES

In this work, optimal and waste-free technologies were proposed for the production of nanocrystalline cellulose (NCC) and its composites with inorganic pigment, as well as semi-finished products containing aggregates of nanoparticles. The following optimal hydrolysis conditions were found: concentration of sulfuric acid 40 wt%, temperature 80°C, duration 1 h, acid/cellulose ratio 7. After hydrolysis stage, the hydrolyzed cellulose was washed, diluted with water and disintegrated to isolate individual nanoparticles. Then, the diluted NCC dispersion was evaporated to obtain a commercial product - concentrated NCC paste. In order to obtain a composite, the acid in the unwashed hydrolyzed cellulose was neutralized with calcium hydroxide to precipitate a white pigment, calcium sulfate. In addition, the spent acid and acidic washings were collected and treated with hydroxylapatite (HAP) to produce a valuable by-product, superphosphate (SUP), the sale of which significantly reduces the cost of the primary product, NCC. Contaminated water collected after washing, neutralization and evaporation was purified and returned to the technological cycle. To reduce the cost of production, such expensive process steps as disintegration and evaporation of diluted dispersion were eliminated, which made it possible to obtain cheap semi-finished products containing NCC aggregates or composite of NCC with inorganic calcium sulfate particles.

COMPOSITE ION-EXCHANGES FOR THE RECYCLING OF LIQUID WASTE OF DAIRY INDUSTRY

The method of directed formation of particles of hydrated zirconium and titanium oxides into anion exchange resins has been developed. The approach based on the Ostwald-Freundlich thermodynamic equation is applied. Such approach, in particular, connects the size of particles with the solubility of the compound, volume and concentration of reagents. Less soluble zirconium dioxide is deposited as non-aggregated nanoparticles, the size of which does not exceed 10 nm. The composition of such composites is the most reproducible. In the case of more soluble titanium dioxide, aggregates of nanoparticles (up to 70 nm) are formed. When the concentration of the solution of metal salts in the polymer increases, the particles of micron size are deposited, the composition of this type of material is less reproduced. Non-aggregated nanoparticles increase the exchange capacity of the polymer. This leads to an increase in its electrical conductivity in 1.4-1.8 times. This is due to an increase in the concentration of mobile charge carriers in the polymer matrix that is caused by reducing its swelling. Other reason is a contribution of the counter-ions of the functional groups of inorganic component to ion transport. On the contrary, the aggregates of nanoparticles amplify the polymer swelling, resulting in a reduction of exchange capacity and electrical conductivity. Ion-exchangers were used for the ion exchange processing of nanofiltration permeate of milky whey, and for electromembrane desalination of protein concentrate.