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. 2024 Jun 28;10(7):431.
doi: 10.3390/gels10070431.

Biodegradable Cassava Starch/Phosphorite/Citric Acid Based Hydrogel for Slow Release of Phosphorus: In Vitro Study

Andrés F Chamorro  1 , Manuel Palencia  2 , Enrique M Combatt  3
Affiliations

Biodegradable Cassava Starch/Phosphorite/Citric Acid Based Hydrogel for Slow Release of Phosphorus: In Vitro Study

Andrés F Chamorro et al. Gels. .

Abstract

Phosphorous (P) is one the most important elements in several biological cycles, and is a fundamental component of soil, plants and living organisms. P has a low mobility and is quickly adsorbed on clayey soils, limiting its availability and absorption by plants. Here, biodegradable hydrogels based on Cassava starch crosslinked with citric acid (CA) were made and loaded with KH2PO4 and phosphorite to promote the slow release of phosphorus, the storing of water, and the reduction in P requirements during fertilization operations. Crosslinking as a function of CA concentrations was investigated by ATR-FTIR and TGA. The water absorption capacity (WAC) and P release, under different humic acid concentration regimens, were studied by in vitro tests. It is concluded that hydrogel formed from 10% w/w of CA showed the lowest WAC because of a high crosslinking degree. Hydrogel containing 10% w/w of phosphorite was shown to be useful to encouraging the slow release of P, its release behavior being fitted to the Higuchi kinetics model. In addition, P release increased as humic acid contents were increased. These findings suggest that these hydrogels could be used for encouraging P slow release during crop production.

Keywords: Cassava starch; P slow release; hydrogels; phosphorite.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1
Figure 1
ATR-FITR spectra of (A) Cassava starch, (B) CA, and (C) SBHG(7%).
Figure 2
Figure 2
Illustration of the crosslinking of starch by Fischer esterification reaction with CA.
Figure 3
Figure 3
ATR-FITR spectra of dry hydrogels of Cassava starch crosslinked with various CA concentrations: 0.5 (A), 1.0 (B), 5.0 (C), 7.0 (D), 10.0 (E), 20.0 (F) and 40.0% w/w (G).
Figure 4
Figure 4
Effect of CA concentration on: (A) fraction gel and (B) WAC of SBHG. In addition, (C) digital photos of SBHG with various CA concentrations before (dry) and after the water-absorbing process (swollen).
Figure 5
Figure 5
WAC of SBHG(10.0%) in different media containing 0.5% w/v of solute (NaCl, KCl, CaCl2, NaOH and HCl).
Figure 6
Figure 6
(A) TGA and (B) weight loss derivate curves of Cassava starch, SBHG(1.0%), SBHG(5.0%), and SBHG(10.0%).
Figure 7
Figure 7
(A) Digital photos of materials containing P, and (B) in vitro release profiles of phosphorus and (C) phosphorus entrapped after 1, 24, and 144 h in the release experiment on SBHG(10.0%)-phosphate, phosphorite (without ground), and SBHG(10%)-phosphorite.
Figure 8
Figure 8
In vitro release profiles of phosphorus from SBHG(10.0%)-phosphorite at different concentrations of HA (A) and different pH values (B). the NaOH 1.0 M solution in deionized water was used as the release medium for HA, and the results are represented as the mean SD of triplicate experiments.
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