2025 AIChE Annual Meeting

(292b) Thermal and Dissolution Properties of Urea Cocrystals

Authors

Carl R. Wassgren, Purdue University
Kingsly Ambrose, Purdue University
Environmental sustainability challenges have arisen worldwide due to pollution resulting from the excessive application of urea. Slower release rate fertilizers lead to lower ammonia loss, reduced nitrate leaching, increased accumulation of nitrate and ammonium in the soil, enhanced nitrogen uptake, and improved crop quality.
Cocrystallization is a powerful tool for developing desirable urea compounds, making them well-suited for industrial applications. In the pharmaceutical industry, cocrystals allow for the design of more effective and easily administered medications which can enhance drug delivery and absorption. In agriculture, urea cocrystals can control the release of nitrogen from urea fertilizers, improving nutrient uptake by plants, and reduces the negative impact on the environment. Cocrystallization is an emerging technique and an environmentally sustainable method for producing slow-release urea fertilizer, contributing to waste conversion into eco-friendly solutions. This work investigated the effectiveness of gypsum and hydroxybenzoic acid in forming cocrystals with urea. The thermal behavior of URCASU (urea + gypsum) and urea·4HBA (urea + hydroxybenzoic acid) was analyzed using a thermogravimetric analyzer. In the cocrystals, there was no mass loss at 100 °C due to dehydration, suggesting the absence of crystalline water in the crystal lattice. In addition, the dissolution behavior of urea cocrystal compacts were studied. Compacts of 100 MPa were produced using a die-punch set of a mechanical testing machine from a mixture of urea cocrystals and a binder (1:1 mixture of konjac and xanthan gum) in powder form at a fixed binder-solid ratio. The results shows that both urea cocrystals have extended urea dissolution times compared to market urea. These results suggests that cocrystallization along with particle design will help in developing environmentally sustainable smart fertilizers.