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. 2023 Aug 11;13(1):13049.
doi: 10.1038/s41598-023-40064-1.

Cerium(IV) chitosan-based hydrogel composite for efficient adsorptive removal of phosphates(V) from aqueous solutions

Łukasz Wujcicki  1 , Tomasz Mańdok  1 , Wiktoria Budzińska-Lipka  1 , Karolina Pawlusińska  1 , Natalia Szozda  1 , Gabriela Dudek  2 , Krzysztof Piotrowski  3 , Roman Turczyn  2   4 , Maciej Krzywiecki  5 , Alicja Kazek-Kęsik  6 , Joanna Kluczka  7
Affiliations

Cerium(IV) chitosan-based hydrogel composite for efficient adsorptive removal of phosphates(V) from aqueous solutions

Łukasz Wujcicki et al. Sci Rep. .

Abstract

The excess presence of phosphate(V) ions in the biosphere is one of the most serious problems that negatively affect aqueous biocenosis. Thus, phosphates(V) separation is considered to be important for sustainable development. In the presented study, an original cerium(IV)-modified chitosan-based hydrogel (Ce-CTS) was developed using the chemical co-precipitation method and then used as an adsorbent for efficient removal of phosphate(V) ions from their aqueous solutions. From the scientific point of view, it represents a completely new physicochemical system. It was found that the adsorptive removal of phosphate(V) anions by the Ce-CTS adsorbent exceeded 98% efficiency which is ca. 4-times higher compared with the chitosan-based hydrogel without any modification (non-cross-linked CTS). The best result of the adsorption capacity of phosphates(V) on the Ce-CTS adsorbent, equal to 71.6 mg/g, was a result of adsorption from a solution with an initial phosphate(V) concentration 9.76 mg/dm3 and pH 7, an adsorbent dose of 1 g/dm3, temperature 20 °C. The equilibrium interphase distribution data for the Ce-CTS adsorbent and aqueous solution of phosphates(V) agreed with the theoretical Redlich-Peterson and Hill adsorption isotherm models. From the kinetic point of view, the pseudo-second-order model explained the phosphates(V) adsorption rate for Ce-CTS adsorbent the best. The specific effect of porous structure of adsorbent influencing the diffusional mass transfer resistances was identified using Weber-Morris kinetic model. The thermodynamic study showed that the process was exothermic and the adsorption ran spontaneously. Modification of CTS with cerium(IV) resulted in the significant enhancement of the chitosan properties towards both physical adsorption (an increase of the point of zero charge of adsorbent), and chemical adsorption (through the presence of Ce(IV) that demonstrates a chemical affinity for phosphate(V) anions). The elaborated and experimentally verified highly effective adsorbent can be successfully applied to uptake phosphates(V) from aqueous systems. The Ce-CTS adsorbent is stable in the conditions of the adsorption process, no changes in the adsorbent structure or leaching of the inorganic filling were observed.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
FTIR spectra of the chitosan-based adsorbent (CTS), modified with cerium (Ce-CTS), modified with cerium after phosphates(V) adsorption (P-Ce-CTS) (A) and XPS spectra of the chitosan-based adsorbent modified with cerium (Ce-CTS) before (B-bottom panel) and after phosphates(V) adsorption (B-top panel).
Figure 2
Figure 2
The results of high-resolution XPS scans for Ce-CTS (bottom panels) and P-Ce-CTS (top panels) for C 1 s energy region (A), N 1 s energy region (B), Ce 3d energy region (C), O 1 s energy region (D) and P 2p energy region (E).
Figure 3
Figure 3
SEM images of chitosan-based hydrogel (A), hydrogel modified with cerium(IV) (B), hydrogel modified with cerium(IV) after adsorption of phosphates(V) (magnification 5000×) (C) and the exemplary corresponding EDS spectra (D–F).
Figure 4
Figure 4
Effect of pH solution (left panel) and pHPZC diagram (right panel) for the cerium-modified chitosan-based adsorbent – experimental data. Ce-CTS (20% wt. of cerium) hydrogel dose: 20 g/dm3 (0.8 g/dm3 for dry mass); initial concentration of P-PO4: 9.3 ± 0.1 mg/dm3; contact time: 48 h; temperature: 20 ± 1 °C, tested pH range: 4–10. The bars represent the RSD for two repeats.
Figure 5
Figure 5
Dependence of the efficiency of phosphates(V) removal from their aqueous solutions on the mass of cerium(IV) dispersed phase used in the chitosan-based composite hydrogel of 20 g/dm3 dose (left panel) and on the dose of chitosan-based composite hydrogel modified with cerium(IV) ions in the ratio of 1:4 (right panel). Initial concentration of P-PO4: 9.3 ± 0.1 mg/dm3; contact time: 48 h; temperature: 20 ± 1 °C.
Figure 6
Figure 6
Kinetics of the phosphates(V) adsorption process on the cerium-modified chitosan-based hydrogel—raw experimental data (A), the pseudo-first-order model approach (in a linearized form) (B), pseudo-second-order model approach (in a linearized form) (C), experimental dependence of qt = f(t0.5) (D), formal Weber-Morris model (in a linearized form) (E) and Weber-Morris model in intraparticle diffusion range (in a linearized form) (F). Ce-CTS (20% wt. of cerium) hydrogel dose: 20 g/dm3 (0.8 g/dm3 for dry mass); initial concentration of P-PO4: 9.76 ± 0.09 mg/dm3; pH: 7; temperature: 20 ± 1 °C, tested contact time: 5–2880 min.
Figure 7
Figure 7
Adsorption isotherm of phosphates(V) on the cerium-modified chitosan-based hydrogel—raw experimental data and five theoretical or empirical adsorption isotherm models. Ce-CTS (20% wt. of cerium) hydrogel dose: 20 g/dm3 (0.8 g/dm3 for dry mass); pH: 7; contact time: 24 h; temperature: 20 ± 1 °C, tested initial concentration of P-PO4: 0.1—500 mg/dm3.
Figure 8
Figure 8
The possible mechanism of phosphate(V) adsorption on Ce-CTS hydrogel beads surface.
Figure 9
Figure 9
The chitosan-based composite hydrogel – its synthesis scheme.
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References

    1. Pawelec, K. Phosphorus dispersion is a growing environmental hazard (eds. Jędrzej Nyćkowiak, J., Leśny, J.) 29–37 (ISBN online 978-83-66743-41-0 Młodzi naukowcy, 2021).
    1. Fluck, E. The chemistry of phosphine. In: Inorganic Chemistry. Fortschritte der Chemischen Forschung. 35, 1–64 (Springer, 1973).
    1. Morse, G. K., Lester, J. N. & Perry, R. The Economic and Environmental Impact of Phosphorus Removal from Wastewater in the European Community. 14–19 (Selper, 1991).
    1. Young K, et al. The relation between phosphorus and eutrophication in the Thames catchmet. Sci. Total Environ. 1999;228:157–159.
    1. Styka, W. Evaluation of the contribution of denitrification dephosphatation to phosphorus removal in SBR reactors. Gaz, Woda Tech. Sanit.12, 437–439.