KINETIKA REAKSI POLIMERISASI UREA-ASETALDEHID DALAM PROSES ENKAPSULASI UREA

• المؤلفون الرئيسيون: , INDAH PURNAMASARI, , Prof. Ir. Rochmadi, SU, Ph.D
• التنسيق: Theses and Dissertations NonPeerReviewed
• منشور في: [Yogyakarta] : Universitas Gadjah Mada 2012
• الموضوعات: ETD
• الوصول للمادة أونلاين: https://repository.ugm.ac.id/97893/; http://etd.ugm.ac.id/index.php?mod=penelitian_detail&sub=PenelitianDetail&act=view&typ=html&buku_id=53827
• المؤسسة: Universitas Gadjah Mada

One method to increase the effectiveness of urea utilization and thus reduce environmental pollution caused by urea is encapsulation of urea. With urea encapsulation, its releases in water can be controlled. Microcapsule shell is formed directly on surface of urea particles called in situ polymerization. This research aimed to study the kinetics of the polymerization reaction of urea and acetaldehyde in the urea encapsulation process. The proposed model considers the diffusion of acetaldehyde and reaction in solid phase. Urea and acetaldehyde in 1:1.2 ratio mol/mol were charged into erlenmeyer equipped with a thermometer and cooler. The reaction was run for 2 hours and sample was taken every 20 minutes. The amount of remaining acetaldehyde was determined by sodium sulfite method and grain size was measured by optical microscope and image pro software. Variables investigated were reaction temperatures (5 - 15°C), particle sizes (14, 18, and 25 mesh), and pH (2 - 4). Reaction rate constants and diffusivity constants were determined by minimizing SSE. The results show that the higher temperature and grain size, the higher conversion is. Lower pH (more acid) provides higher conversion. Urea particle was seen slightly swelling during the reaction, and also slightly sticky The proposed reaction kinetics model fits well to the experimental data and the value of reaction rate constants vary around : k1 (addition) 6.975 - 242.7 mL/mmol/min, k2 (condensation) 2.81 x 10-3 � 0.133 and k3 4.70 x 10-5 � 1.17 x 10-2 ml/mmol/min. The value of diffusion constants are DA = 9.06 x 10-7- 1.75 x 10-5cm2/min and DH+= 3.18 x 10-6� 7.06 x 10-5cm2/min. The process is bestconducted at 15oC, 14 mesh, pH 4 and 120 minutes time of reaction which result in 63.38% conversion. This can be seen from appearance of polymer product of urea-acetaldehyde that is slightly tougher than that of in other condition.