Thermodynamic and kinetic parameters of the development of technology for producing complex mineral fertilizers with agrochemical properties using hydrogel

This work is devoted in detail to elucidating the thermodynamic and kinetic considerations for the production of mineral fertilizers with a hydrogel consisting of hydrolyzed polyacrylonitrile (HIPAN) in the presence of a cross-linking agent – the product of the reaction of epichlorohydrin with a 33% aqueous ammonia solution (ECHA). Traditional qualitative analysis of individual factors based on kinetic and thermodynamic parameters does not sufficiently reveal the mechanism underlying the absorption of nutrients by hydrogel during the development of mineral fertilizers and the subsequent transfer of these nutrients and moisture into the soil. This study aimed to determine the influence of temperature, humidity and their interaction on kinetic and thermodynamic parameters, which revealed the key control mechanism underlying hydrogel nutrient uptake in mineral fertilizer development, modified the traditional Arrhenius model, and established a quantitative prediction model for cumulative nutrient uptake substances. Field experiments were carried out at different temperatures (T) (15°C, 20°C, 25°C and 35°C) and moisture content (θ) (60%, 80% and 100% of field capacity). The results showed that the influence of individual factors and their interaction on the values of reaction rate (КN), activation free energy (ΔG) and activation entropy (ΔS) followed the descending order T>θ>T·θ, while the enthalpy of activation (ΔH) and the degree of activation (logN) followed the descending order θ>T>T·θ. Results indicated an endothermic nutrient uptake reaction controlled by enthalpy, with a new model “A” (NH₄NO₃ (T, θ)) proving more accurate than traditional models, improving the accuracy of nutrient uptake prediction.