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Journal of Chemistry
Volume 2015 (2015), Article ID 237397, 17 pages
Research Article

Encapsulated Urea-Kaolinite Nanocomposite for Controlled Release Fertilizer Formulations

1Department of Materials Science and Engineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania
2Department of Chemical Engineering, Hanyang University, 1271 Sa 3-dong, Sangnok-gu, Ansan-si, Gyeonggi-do 426-791, Republic of Korea
3Chemistry Department, University of Dar es Salaam, P.O. Box 35091, Dar es Salaam, Tanzania
4Department of Chemistry, Mkwawa College of Education, University of Dar es Salaam, P.O. Box 2513, Iringa, Tanzania

Received 17 March 2015; Accepted 20 May 2015

Academic Editor: Manuela Curcio

Copyright © 2015 Siafu Ibahati Sempeho et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Urea controlled release fertilizer (CRF) was prepared via kaolinite intercalation followed by gum arabic encapsulation in an attempt to reduce its severe losses associated with dissolution, hydrolysis, and diffusion. Following the beneficiation, the nonkaolinite fraction decreased from 39.58% to 0.36% whereas the kaolinite fraction increased from 60.42% to 99.64%. The X-ray diffractions showed that kaolinite was a major phase with FCC Bravais crystal lattice with particle sizes ranging between 14.6 nm and 92.5 nm. The particle size varied with intercalation ratios with methanol intercalated kaolinite > DMSO-kaolinite > urea-kaolinite (KPDMU). Following intercalation, SEM analysis revealed a change of order from thick compact overlapping euhedral pseudohexagonal platelets to irregular booklets which later transformed to vermiform morphology and dispersed euhedral pseudohexagonal platelets. Besides, dispersed euhedral pseudohexagonal platelets were seen to coexist with blocky-vermicular booklets. In addition, a unique brain-form agglomeration which transformed into roundish particles mart was observed after encapsulation. The nanocomposites decomposed between 48 and 600°C. Release profiles showed that 100% of urea was released in 97 hours from KPDMU while 87% was released in 150 hours from the encapsulated nanocomposite. The findings established that it is possible to use Pugu kaolinite and gum arabic biopolymer to prepare urea CRF formulations.