Microencapsulation of potassium phosphate in chitosan and the effect of spray drying operating variables on the particle size

The use of biodegradable polymers to encapsulate fertilizers is one of the main tools that help to prevent them to get carried away by the irrigation water, since phosphate based fertilizers are highly soluble. Indeed, this technology might improve productivity and reduce both costs and environmental pollution. In this work potassium phosphate was encapsulated in chitosan, which is one of the most abundant natural and biodegradable polymers widely applied in agriculture for plant defense and yield increase, applying the encapsulation method of spray drying to provide a high encapsulation efficiency rates. A 2(k) factorial design was implemented to evaluate the effect of the different operational parameters of the spray dryer on the particle size, measured by scan electronic microscopy, then it was obtained the average particle sizes to be between 1.08 to 2.04 mu m. The release of KH2PO4 from chitosan spheres of different sizes was performed in Milli-Q water and was measured using the conductometry technique. The experiments revealed that the parameter with the greatest effect was the feed rate, and that the system with the smallest particle size obtained (1.08 mu m) showed a slower release without losing an important amount of encapsulation efficiency.