Chitosan/Starch Matrices Prepared by Ionotropic Gelation: Rheological Characterization, Swelling Behavior and Potassium
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ORIGINAL PAPER
Chitosan/Starch Matrices Prepared by Ionotropic Gelation: Rheological Characterization, Swelling Behavior and Potassium Nitrate Release Kinetics Jonás J. Perez Bravo1,2,3 · Nora J. François1,2
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A controlled-release fertilizer made of biodegradable beads prepared with neat chitosan or chitosan/starch blends loaded with potassium nitrate was obtained using an ionic cross-linking process. This study looks at the influence of chitosan/starch mass ratio on the dynamic rheological behavior of the polymeric material without cross-linking. Every tested sample showed a viscoelastic behavior corresponding to entanglement networks of concentrated solutions except for the gelatinized starch that presented a gel behavior. Two factors affecting the water absorption and the fertilizer release were investigated: the polymeric composition (chitosan/starch mass ratio) and the cross-linking time. It was found that the equilibrium swelling degree decreased by increasing the beads’ starch content and/or the cross-linking time. When loaded beads were immersed 16 days in water under static conditions, the fertilizer release ratio was greater than 70% of the total loading. The hydrogel composition and the cross-linking time defined the mechanism governing the potassium nitrate release which was matrix relaxation controlled. Experimental results indicated that it is possible to modify the release profile of the loaded fertilizer which it is a very promising characteristic for the development of a compelling controlled-release fertilizer. Keywords Hydrophilic matrices · Dynamic rheology · Controlled release · Swelling degree
Introduction Fertilizer application and water supplies are important factors that limit agricultural production. It is necessary to improve the utilization of water resources and to limit the fertilizers dosage in order to achieve a balance between costs and economic profits. It is a fact that much of the nitrogen, phosphorus, and potassium of the applied conventional fertilizers are lost to the environment and therefore, they cannot * Nora J. François [email protected] 1
Grupo de Aplicaciones de Materiales Biocompatibles, Departamento de Química, Facultad de Ingeniería, Universidad de Buenos Aires (UBA), C1063ACV CABA, Argentina
2
Facultad de Ingeniería, Instituto de Tecnología en Polímeros y Nanotecnología (ITPN), Universidad de Buenos Aires (UBA-CONICET), C1127AAQ CABA, Argentina
3
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1033AAJ CABA, Argentina
be absorbed by crops [1], which causes not only large economical and resources losses but also, a very serious environmental pollution. The excessive application of chemical fertilizers is one of the main sources of pollution of lakes, streams and groundwater supplies [2, 3]. The use of controlled release fertilizers (CRFs) is a new trend in agricultural production that can reduce fertilizer consumption and minimize en
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