The kinetics of plasma nitriding of CoCr alloy below temperatures of nitrides formation and mechanisms of nitrogen penetration are analyzed by proposed kinetic modeling in this article. Proposed nitrogen diffusion model is based on the trapping – detrapping (TD) model and developed taking into account the effect of the concentration dependent diffusivity of nitrogen, nitrogen adsorption on the surface of alloy and surface swelling process. The model indicates the influence of chromium atoms to nitrogen atoms diffusivity. The model consists of time and depth dependent diffusion, which is described by a partial differential equation, and it is solved by using Crank – Nicolson finite difference method. By fitting of experimental nitrogen depth profiles, it is shown that nitrogen diffusion coefficient varies with nitrogen concentration according to Einstein-Smoluchowski relation. Nitrogen depth profiles in plasma nitrided medical grade CoCr alloy (ISO 5831 – 12) at T = 400 °C for 1, 4 and 20 hours calculated on the basis of this model are in good agreement with experimental nitrogen profiles. Furthermore, the swelling process is showed and analyzed, derived the dependency of swelling rate on nitriding duration – the swelling rate is inversely proportional to the square root of nitriding duration. The obtained diffusion coefficient value and the swelling process rates satisfy the experimental data form Ref. The derived model explains physical processes during plasma nitriding and allows obtaining nitrogen depth profiles for any requisite nitriding duration.

Glycerol is a versatile substance used in food, beverages, cosmetics, and technical applications. It can be derived from fats and oils through 4 different reactions, including: transesterification, directed hydrogenation, hydrolysis, and saponification. Glycerol derived from fat hydrolysis yields superior quality and quantity when compared to saponification. The resulting glycerol water is purified and concentrated through evaporation to yield crude glycerol with a concentration of 86–88%. Two distinct methods are recognized for further improving quality of glycerol: distillation, and the purification of glycerol water through the ion exchange process followed by evaporation. The goal of this research was to improve the purification process of glycerol, for obtaining premium-quality glycerol without the need for distillation, through the utilization of cations. Several combinations of activated carbon and clay were tested, and it was determined that a combination of 70:30 yielded the optimal results, considering the amount of glycerol and ash content. Technological parameters such as reaction durations, pH, and process temperatures were investigated, and it was discovered that the appropriate combination was a process duration of more than 40 minutes, a pH value of 2, and a temperature of 70 °C. Besides, it was also determined that the concentration and quality of glycerol derived from cottonseed oil can be enhanced through distillation or purification with cationite. Moreover, different concentrations of glycerol on the elaboration of gingerbread were tested, and the conclusion is that adding 5% of the resulting glycerol to the gingerbread recipe could ensure better preservation of its quality during its shelf life.