Effect of Chitosan Gelatinization Temperature on Water Absorption and Water Retention of Chitosan-Based Urea Fertilizer

Abstract

Chitosan has a high potential to be blended together in urea fertilizer for slow release properties due to its unique polymeric cationic character and gel-forming properties. In agriculture, the slow release properties are normally indicated by the ability of urea fertilizer to absorb and retain water, since nitrogen is released to the environment once urea is in contact with water or enzyme. This paper investigates the effect of the chitosan content and gelatinization temperature on the physical properties of chitosanbased urea  fertilizer. The chitosan content was varied from 0, 3, 5, 7 and 10 pph. Chitosan-based urea fertilizer was prepared through a direct wet mixing using a laboratory setup consisting of a beaker, magnetic stirrer and hotplate. The properties of chitosan-based urea fertilizer were compared at two different mixing temperatures which are 60oC and room temperature of 25 ± 3oC. The mixture was then dried in an oven at 60oC for 8 hours before being fabricated into pellets using a hydraulic hand presser. Water absorption and water retention analysis were carried out to measure the amount of water intake and the amount of water retained in the fertilizer. It was observed that mixing temperature has a negligible effect on the water retention of the fertilizers. However, gelatinization at room temperature resulted in fertilizers with better water absorption and water retention properties than the one gelatinized at 60C. These results were supported by X-ray diffraction (XRD) analysis conducted on the fertilizers. As a conclusion, the gelatinization temperature plays an important role in improving the water retention and water absorption capability of chitosan-based urea fertilizers.  Furthermore, the presence of chitosan improved the crystallinity of the urea fertilizers, as indicated by XRD analysis.