Abstract
Abstract The main objective of the present work is to produce and characterize urea granules coated with polymers prepared with aqueous solutions of acrylic acid and glycerol. Both coating and drying of urea granules were performed in a fluidized bed reactor. Fourier transform infrared spectroscopy analyses indicated the presence of poly(acrylic acid) and acrylic acid / glycerol copolymers on the granule coating and the formation of chemical bonds between urea and the polymer coating. Scanning electron microscopy images showed that the original and coated urea granules presented different characteristics, reinforcing the idea that coating occurs in the fluidized bed. Finally, rates of urea release showed that the coated granules presented slightly slower rates of urea dissolution in water due to the presence of the coating layer. Therefore, it is shown that it is possible to produce coated urea granules through in-situ polymerization onto the granule surface using a fluidized bed.
Highlights
Urea is the fertilizer used most often in agriculture; for this reason, the worldwide production and consumption of urea has steadily increased in recent years
The coated and uncoated urea granules were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM)
Coated urea granules were produced in a fluidized bed reactor through in-situ copolymerization of acrylic acid and glycerol and addition of acrylic acid / glycerol copolymers in water
Summary
Urea is the fertilizer used most often in agriculture; for this reason, the worldwide production and consumption of urea has steadily increased in recent years. Urea is characterized by its high nitrogen content (46 wt%), low production cost and high water solubility. Losses can reach 50 wt% of the applied urea fertilizer, depending on the climate, soil conditions and application technologies, causing environmental pollution and increasing the costs of crop production[6,7,8,9,10]. A possible alternative to reduce nutrient losses is the development of slow-release fertilizers by coating urea granules with materials that feature lower water solubility[5,9,10] or by using materials that allow for the slow release of urea[8,11,12,13,14]. The production of slow-release urea products with help of polymer coatings constitutes a promising technological solution for many applications[7,9,15]
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