PREPARATION AND CHARACTERIZATIONS OF STARCH–N-HEPTYLUREA COMPLEXES AS POTENTIAL MATERIAL FOR CONTROLLED RELEASE FERTILIZER

• Main Author: Elsaria Jaya, Elizabeth
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/83051
• Institution: Institut Teknologi Bandung

Urea is a type of fertilizer that contains a high nitrogen content. Nitrogen is required by plants as the main component for the formation of chlorophyll, protein, and amino acids. However, plants are not able to absorb nitrogen from urea optimally, due to the absorption process occurring over 2–3 days, and only about 20–30% (w/w) of the decomposed nitrogen can be absorbed. Moreover, urea is easily decomposed and easily carried away by rainwater. This leads to the inefficient use of urea fertilizer and posible to pollute soil and water. One way to address this issue is to modify urea into an inclusion complex to produce fertilizer with more controlled nitrogen release, also known as controlled release fertilizer (CRF). In this research, starch was used as the host molecule. Starch consists of amylose structures in the form of single helices, having internal cavities. These cavities or channels can be filled with urea based fertilizers. First, hydrophobicity of urea needs to be increased. Unmodified urea that is hydrophilic cannot directly interact with hydrophobic amylose cavities. Urea was reacted with 1-bromoheptane to form an urea derivative with one hydrogen substituted by heptyl (N-hepthylurea). N-heptylurea was characterized using fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Then, N-heptylurea was mixed with starch solution to form starch–N-heptylurea inclusion complexes. Starch–N-heptylurea complexes were characterized using FTIR and XRD, and an iodine test. IR, NMR, and XRD characterization results indicated that N-heptylurea was successfully formed with a yield of 2.5% (w/w). N-heptylurea product was complexed with starch to produce starch–N-heptylurea complexes. The percentage of N-heptylurea as the guest molecule was varied at 5% (w/w) and 7% (w/w) based on the complex mass. The characterization and iodine test results showed that the starch–N-heptylurea inclusion complexes were successfully formed, with complexation percentages of 74% (w/w) for both 5% and 7% guest molecule variation. The study of nitrogen release was conducted for urea, N-heptylurea, and starch–N-heptylurea complexes 5% and 7% guest molecule variation. On 4 days after planting, accumulative nitrogen (in form of NH4+ and NO3–) released from N-heptylurea and starch–N-heptylurea was slower compared to the nitrogen release from urea. This trend also seen on 10 days after planting, but the accumulative nitrogen released was higher than on 4 days after planting. The study of nitrogen release showed that starch–N-heptylurea complexes can indeed slow down the nitrogen release from urea fertilizers.