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. 2019 Oct 25;12(21):3493.
doi: 10.3390/ma12213493.

Environmentally Friendly Fertilizers Based on Starch Superabsorbents

Orietta León  1 , Diana Soto  1 , Jesús González  1 , Carlos Piña  1 , Alexandra Muñoz-Bonilla  2   3 , Marta Fernandez-García  2   3
Affiliations

Environmentally Friendly Fertilizers Based on Starch Superabsorbents

Orietta León et al. Materials (Basel). .

Abstract

Superabsorbents starches (SASs) were synthesized and characterized starting from native corn starch, bitter cassava and sweet cassava by graft copolymerization with itaconic acid. Additionally, their swelling behavior was studied both in water and in buffer solutions with different pHs and saline solutions. Their applicability was tested as environmentally friendly fertilizers in the absorption and release of urea, potassium nitrate and ammonium nitrate at different concentrations of fertilizers. The values of swelling at the equilibrium (H∞) in water and different media of the graft copolymers demonstrated their superabsorbent capacity, polyelectrolyte behavior, and smart response to environmental stimuli. The percentage of fertilizer absorbed and released from the SASs was a function of the initial concentration of the fertilizer in the medium. The loading and release of SASs were depended on the initial concentration of the fertilizer in the medium as well as the nature, structure, and morphology of the starch used.

Keywords: adsorption; controlled release; graft copolymers; starch; superabsorbent.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Ehrlich reaction.
Figure 1
Figure 1
Apparent viscosity as a function of shear rate for the different samples.
Figure 2
Figure 2
XRD profiles of (A) corn starch (CCS) grafted starch and its corresponding native corn starch (NCS), (B) bitter cassava (CMES) grafted starch and its corresponding native bitter cassava starch(NMES), and (C) sweet cassava (CMUS) grafted starch and its corresponding native sweet cassava starch (NMUS).
Figure 3
Figure 3
Thermograms of the different graft copolymers and their corresponding native starches.
Figure 4
Figure 4
SEM images and the particle size distributions of (a,d) NCS, (b,e) NMES, and (c,f) NMUS, respectively.
Figure 5
Figure 5
SEM images of (a) CCS, (b) CMES, and (c) CMUS at different augmentations.
Figure 6
Figure 6
Swelling at the equilibrium of grafted copolymers as a function of pH.
Figure 7
Figure 7
Fraction of loading in grafted starches: (a) urea, (b) KNO3, and (c) NH4NO3.
Figure 8
Figure 8
(a) Kinetics of urea release, and (b) urea release at different loading concentrations on grafted starches.
Figure 9
Figure 9
Release kinetics of (a) KNO3 with an initial loading concentration of 10 g/Land (b) NH4NO3 at with an initial loading concentration of 0.5 g/L on grafted starches.
Figure 10
Figure 10
Fraction release of (a) KNO3 and (b) NH4NO3 at different loading concentrations.
See this image and copyright information in PMC

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