Swelling and diffusion model of a hydrophilic film coating on controlled-release urea particles--颗粒学报PARTICUOLOGY

Yang, L., An, D., Wang, T.-J., Kan, C., & Jin, Y. (2017). Swelling and diffusion model of a hydrophilic film coating on controlled-release urea particles. Particuology, 30, 73-82. https://doi.org/10.1016/j.partic.2016.03.005

Swelling and diffusion model of a hydrophilic film coating on controlled-release urea particles

Ling Yang, Di An, Ting-Jie Wang ^*, Chengyou Kan, Yong Jin

Department of Chemical Engineering, Tsinghua University, Beijing 100084, China

10.1016/j.partic.2016.03.005

Volume 30, February 2017, Pages 73-82

Received 15 December 2015, Revised 14 March 2016, Accepted 27 March 2016, Available online 20 July 2016, Version of Record 27 January 2017.

E-mail: wangtj@tsinghua.edu.cn

Highlights

• Dense latex films were spray-coated on urea particles in a fluidized bed to control urea release.

• Film swelling in urea solution was found to follow the Lagergren's pseudo-first order kinetics.

• The swollen film structure was studied and a swollen film structure model was proposed.

• Film permeability coefficient has a linear relationship with the swelling ratio.

• Urea release curve was calculated from film swelling ratio and verified with measured result.

Abstract

Controlled-release urea was fabricated by coating urea particles with a polymer latex in a fluidized bed. The latex film coated on the urea particle surface was hydrophilic and swelled in water. The film swelling in water and urea solution and properties of the swollen film were studied. The film swelling in urea solution followed the Lagergren's pseudo-first order kinetics with the swelling coefficient depending on the film material and experimental conditions. The effects of swelling on film structure and permeability were studied. The film permeability coefficient decreased with increasing swelling ratio with an approximately linear relationship. Based on the film formation process and structure of the swollen film, a film structure model consisting of dense and swollen phases was proposed. The permeability coefficient of the spherical film and cumulative release of urea from the coated particles were calculated from the swelling ratio of the spherical film, which was determined from the expansion curve of the coated particle during the release process. The calculated and measured release curves agreed well. This research indicates that the swelling of the hydrophilic film and the controlled-release mechanism are important factors in the development of controlled-release urea.

Graphical abstract

Keywords

Coating; Controlled-release; Particle; Permeability; Swelling; Urea

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