Swelling mechanism of urea cross-linked starch–lignin films in water. Issue 12 (18th June 2018)

• Record Type: Journal Article
• Authors: Sarwono, Ariyanti; Man, Zakaria; Bustam, M. Azmi; Subbarao, Duvvuri; Idris, Alamin; Muhammad, Nawshad; Khan, Amir Sada; Ullah, Zahoor
• Is Part Of: Environmental technology. Volume 39:Issue 12(2018)
• Page Start: 1522
• Page End: 1532
• Publication Date: 2018-06-18
• Subjects: Starch -- slow release fertilizer -- cross-linking -- lignin -- swelling; Environmental engineering -- Periodicals; Environmental protection -- Periodicals; 628.05
• DOI: 10.1080/09593330.2017.1332108
• Languages: English
• ISSNs: 0959-3330

Abstract

ABSTRACT: Coating fertilizer particles with thin films is a possibility to control fertilizer release rates. It is observed that novel urea cross-linked starch–lignin composite thin films, prepared by solution casting, swell on coming into contact with water due to the increase in volume by water uptake by diffusion. The effect of lignin content, varied from 0% to 20% in steps of 5% at three different temperatures (25°C, 35°C and 45°C), on swelling of the film was investigated. By gravimetric analysis, the equilibrium water uptake and diffusion coefficient decrease with lignin content, indicating that the addition of lignin increases the hydrophobicity of the films. When temperature increases, the diffusion coefficient and the amount of water absorbed tend to increase. Assuming that swelling of the thin film is by water uptake by diffusion, the diffusion coefficient is estimated. The estimated diffusion coefficient decreases from 4.3 to 2.1 × 10 −7 cm 2 /s at 25°C, from 5.3 to 2.9 × 10 −7 cm 2 /s at 35°C and from 6.2 to 3.8 × 10 −7 cm 2 /s at 45°C depending on the lignin content. Activation energy for the increase in diffusion coefficient with temperature is observed to be 16.55 kJ/mol. An empirical model of water uptake as a function of percentage of lignin and temperature was also developed based on Fick's law.