Preparation of chitosan microspheres as carrier material to controlled release of urea fertilizer

Abstract This study aimed to investigate the effects of volume ratio in the continuous phase and the dispersed phase (CP/DP) and stirring speed on yield, water absorption, particle size, morphology surface, and cumulative release of nitrogen from the chitosan microsphere. The chitosan microsphere preparation method was emulsion cross-linking with glutaraldehyde saturated toluene (GST) as the cross-linking agent. Urea was mixed with chitosan solution and put into the oil. It was then stirred to form an emulsion. Glutaraldehyde saturated toluene (GST) was added slowly, followed by 2 ml glutaraldehyde, stirred continuously for 2 h. The formed chitosan microsphere was eventually washed and dried to be analyzed. The yield obtained was about 87.01%-96.71%, the water absorption was 79.77%–89.25%, and the diameter size of chitosan microspheres was from 153.66 ± 26.35 μm to 179.39 ± 34.95 μm. The chitosan microspheres morphology were good sphericity even though there were irregular size. Cumulative release analysis was obtained from 32.38%–37.69% by release mechanism such as anomalous behavior (non-Fickian kinetics)