Abstract
This study presents the development of a novel adsorbent based on hydroxyapatite (CaHAp) grafted with sodium benzoate (SB) at varying proportions (5%, 10%, 15%) via a double decomposition method. Structural and chemical characterizations (XRD, FTIR, SEM, TGA/DTA) confirmed the successful integration of SB, with noticeable improvements in crystallinity (+ 10%), porosity, and thermal stability compared to pristine CaHAp. Adsorption experiments using methylene blue (MB⁺) as a model pollutant showed that the CaHAp-(SB)15 composite achieved an adsorption efficiency of 90%. The adsorption process followed Langmuir isotherm (R² > 0.96) and pseudo-second-order kinetics (R² > 0.99), indicating monolayer chemisorption as the dominant mechanism. Increasing SB content correlated with a significant rise in adsorption capacity from 5.41 to 9.42 mg·g⁻¹, demonstrating the role of –CO2⁻ groups in enhancing electrostatic interactions with cationic MB⁺. DFT simulations supported the experimental findings, showing favorable interactions between SB and CaHAp at both molecular and atomic levels, particularly through non-covalent forces such as van der Waals and electrostatic interactions. This combined theoretical–experimental approach highlights CaHAp-(SB)15 as a promising, low-cost, and eco-friendly adsorbent for dye-contaminated wastewater, offering high efficiency, reproducibility, and environmental compatibility.
Data availability
The data presented in this study are available upon request from the corresponding author.
References
Xie, X. et al. Selective adsorption of cationic dyes for stable metal–organic framework ZJU-48. ACS Omega. 5, 13595–13600. https://doi.org/10.1021/acsomega.0c00385 (2020).
Lan, D. et al. Adsorptive removal of organic dyes via porous materials for wastewater treatment in recent decades: a review on species, mechanisms and perspectives. Chemosphere 293, 133464. https://doi.org/10.1016/j.chemosphere.2021.133464 (2022).
Mutahir, S. et al. MOF-derived ZnO/g-C3N4 nanophotocatalyst for efficient degradation of organic pollutant. J. Saudi Chem. Soc. 28, 101821. https://doi.org/10.1016/j.jscs.2024.101821 (2024).
Mutahir, S. et al. Oxygen doped g-C3N4/LDH composite as highly efficient photocatalyst for wastewater treatment. Z. Fur. Phys. Chem. 238, 2183–2197. https://doi.org/10.1515/zpch-2023-0468 (2024).
Azeez, L. et al. Adsorptive properties of rod-shaped silver nanoparticles-functionalized biogenic hydroxyapatite for remediating methylene blue and congo red. Inorg. Chem. Commun. 142, 109655. https://doi.org/10.1016/j.inoche.2022.109655 (2022).
Xu, T., An, S., Peng, C., Hu, J. & Liu, H. Construction of large-pore crystalline covalent organic framework as high-performance adsorbent for Rhodamine B dye removal. Ind. Eng. Chem. Res. 59, 8315–8322. https://doi.org/10.1021/acs.iecr.0c00304 (2020).
Zhou, Y. et al. Facile Preparation of alveolate biochar derived from seaweed biomass with potential removal performance for cationic dye. J. Mol. Liq. 353, 118623. https://doi.org/10.1016/j.molliq.2022.118623 (2022).
Zheng, Y., Cheng, B., Fan, J., Yu, J. & Ho, W. Review on nickel-based adsorption materials for congo red. J. Hazard. Mater. 403, 123559. https://doi.org/10.1016/j.jhazmat.2020.123559 (2021).
Aaddouz, M. et al. Removal of methylene blue from aqueous solution by adsorption onto hydroxyapatite nanoparticles. J. Mol. Struct. 1288, 135807 (2023).
Saoiabi, S. et al. Lead and zinc removal from aqueous solutions by aminotriphosphonate-modified converted natural phosphates. Chem. Eng. J. 211–212, 233–239. https://doi.org/10.1016/j.molstruc.2023.135807 (2012).
Hamad, H. N. & Idrus, S. Recent developments in the application of bio-waste-derived adsorbents for the removal of methylene blue from wastewater: a review. Polymers 14, 783. https://doi.org/10.3390/polym14040783 (2022).
Sriram, G. et al. Recent trends in the application of metal-organic frameworks (MOFs) for the removal of toxic dyes and their removal mechanism: a review. Sustain. Mater. Technol. 31, e00378. https://doi.org/10.1016/j.susmat.2021.e00378 (2022).
Toufik, E., Noukrati, H., Abouricha, S. & Barroug, A. & Ben youcef, H. Novel biocomposite based on functionalized poorly crystalline apatite and chitosan: a physicochemical evaluation. Mater. Today Proc. 51, 1918–1923, (2022). https://doi.org/10.1016/j.matpr.2021.02.649
Verma, R., Mishra, S. R., Gadore, V. & Ahmaruzzaman Md. Hydroxyapatite-based composites: excellent materials for environmental remediation and biomedical applications. Adv. Colloid Interface Sci. 315, 102890. https://doi.org/10.1016/j.cis.2023.102890 (2023).
Haider, A., Haider, S., Han, S. S. & Kang, I. K. Recent advances in the synthesis, functionalization and biomedical applications of hydroxyapatite: a review. RSC Adv. 7, 7442–7458. https://doi.org/10.1039/C6RA26124H (2017).
Pokhrel, S. Hydroxyapatite preparation, properties and its biomedical applications. Adv. Chem. Eng. Sci. 8, 225–240. https://doi.org/10.4236/aces.2018.84016 (2018).
Biedrzycka, A. & Skwarek, E. Composites of hydroxyapatite and their application in adsorption, medicine and as catalysts. Adv. Colloid Interface Sci. 334, 103308. https://doi.org/10.1016/j.cis.2024.103308 (2024).
Balasooriya, I. L., Chen, J., Korale Gedara, S. M., Han, Y. & Wickramaratne, M. N. Applications of nano hydroxyapatite as adsorbents: a review. Nanomaterials 12, 2324, (2022). https://doi.org/10.3390/nano12142324
Amenaghawon, A. N., Anyalewechi, C. L., Darmokoesoemo, H. & Kusuma, H. S. Hydroxyapatite-based adsorbents: applications in sequestering heavy metals and dyes. J. Environ. Manag. 302, 113989. https://doi.org/10.1016/j.jenvman.2021.113989 (2022).
Xiong, B. Application of hydroxyapatite for the adsorption of heavy metals in water treatment. Acad. J. Sci. Technol. 8, 52–53. https://doi.org/10.54097/nj2je113 (2023).
Skwarek, E., Gładysz-Płaska, A., Choromańska, J. B. & Broda, E. Adsorption of uranium ions on nano-hydroxyapatite and modified by Ca and ag ions. Adsorption 25, 639–647. https://doi.org/10.1007/s10450-019-00063-z (2019).
Azzaoui, K. et al. Synthesis of hydroxyapatite/polyethylene glycol 6000 composites by novel dissolution/precipitation method: optimization of the adsorption process using a factorial design: DFT and molecular dynamic. BMC Chem. 17, 150. https://doi.org/10.1186/s13065-023-01061-7 (2023).
Pramanik, S., Agarwal, A. K., Rai, K. N. & Garg, A. Development of high strength hydroxyapatite by solid-state-sintering process. Ceram. Int. 33, 419–426. https://doi.org/10.1016/j.ceramint.2005.10.025 (2007).
Achelhi, K. et al. Role of carboxylate chelating agents on the chemical, structural and textural properties of hydroxyapatite. Dalton Trans. 39, 10644–10651. https://doi.org/10.1039/C0DT00251H (2010).
Saoiabi, S., Gouza, A., Bouyarmane, H., Laghzizil, A. & Saoiabi, A. Organophosphonate-modified hydroxyapatites for Zn(II) and Pb(II) adsorption in relation of their structure and surface properties. J. Environ. Chem. Eng. 4, 428–433. https://doi.org/10.1016/j.jece.2015.11.036 (2016).
Rosskopfová, O., Bugriová, M., Viglašová, E., Hupian, M. & Galamboš, M. 111In-hydroxyapatite nanoparticles: sorption studies. J. Radioanal Nucl. Chem. 334, 1631–1641. https://doi.org/10.1007/s10967-024-09913-9 (2025).
Agougui, H., Sebeia, N., Jabli, M., El-Ghoul, Y. & Boughzala, K. Synthesis of hydroxyapatite-sodium metasilicate via double decomposition method: characterization and application to the removal of methylene blue. Inorg. Chem. Commun. 133, 108986. https://doi.org/10.1016/j.inoche.2021.108986 (2021).
Biedrzycka, A., Skwarek, E., Osypiuk, D. & Cristóvao, B. Synthesis of hydroxyapatite/iron oxide composite and comparison of selected structural, surface, and electrochemical properties. Materials 15, 1139. https://doi.org/10.3390/ma15031139 (2022).
Bouazzi, D. et al. Beneficial effect of in-situ citrate-grafting of hydroxyapatite surface for water treatment. Colloids Surf. A 666, 131366. https://doi.org/10.1016/j.colsurfa.2023.131366 (2023).
Khan, M. A. et al. Recent advances over the doped g-C3N4 in photocatalysis: a review. Coord. Chem. Rev. 522, 216227. https://doi.org/10.1016/j.ccr.2024.216227 (2025).
Ait Mansour, A. et al. Comprehensive analysis of a thiazole-substituted corrosion inhibitor’s impact on N80 carbon steel in acidic conditions: integrating computational predictions with experimental verifications. Mater. Chem. Phys. 320, 129405. https://doi.org/10.1016/j.matchemphys.2024.129405 (2024).
Cherriet, S. et al. In silico investigation of aristolochia longa anticancer potential against the epidermal growth factor receptor (EGFR) in the tyrosine kinase domain. Moroccan J. Chem. 11, 1074–1085. https://doi.org/10.48317/IMIST.PRSM/morjchem-v11i04.41725 (2023).
Ren, F., Leng, Y., Xin, R. & Ge, X. Synthesis, characterization and Ab initio simulation of magnesium-substituted hydroxyapatite. Acta Biomater. 6, 2787–2796. https://doi.org/10.1016/j.actbio.2009.12.044 (2010).
El Hassani, A. A. et al. A combined molecular dynamics simulation, DFT calculations, and experimental study of the adsorption of Rhodamine B dye on kaolinite and hydroxyapatite in aqueous solutions. Surf. Interfaces. 36, 102647. https://doi.org/10.1016/j.surfin.2023.102647 (2023).
Alshahateet, S. F. et al. Catalytic green synthesis of Tin(IV) oxide nanoparticles for phenolic compounds removal and molecular docking with EGFR tyrosine kinase. Sci. Rep. 14, 6519. https://doi.org/10.1038/s41598-024-55460-4 (2024).
Du, J. et al. Molecular basis of recognition of human osteopontin by 23C3, a potential therapeutic antibody for treatment of rheumatoid arthritis. J. Mol. Biol. 382, 835–842. https://doi.org/10.1016/j.jmb.2008.07.075 (2008).
Merzouki, M. et al. In silico evaluation of antiviral activity of flavone derivatives and commercial drugs against SARS-CoV-2 main protease (3CLpro). Moroccan J. Chem. 11(1), 129–143. https://doi.org/10.48317/IMIST.PRSM/morjchem-v11i1.35278 (2023).
Filgueiras, M. R. T., Mkhonto, D. & de Leeuw, N. H. Computer simulations of the adsorption of citric acid at hydroxyapatite surfaces. J. Cryst. Growth 294, 60–68. https://doi.org/10.1016/j.jcrysgro.2006.05.077 (2006).
Aissa, A., Agougui, H. & Debbabi, M. Surface modification of calcium fluoro and hydroxyapatite by 1-octylphosphonic dichloride. Appl. Surf. Sci. 257, 9002–9007. https://doi.org/10.1016/j.apsusc.2011.05.087 (2011).
Barandehfard, F. et al. The addition of synthesized hydroxyapatite and fluorapatite nanoparticles to a glass-ionomer cement for dental restoration and its effects on mechanical properties. Ceram. Int. 42, 17866–17875. https://doi.org/10.1016/j.ceramint.2016.08.122 (2016).
Phan, B. T. N. et al. Synthesis and characterization of nano-hydroxyapatite in maltodextrin matrix. Appl. Nanosci. 7, 1–7. https://doi.org/10.1007/s13204-016-0541-z (2017).
Degli Esposti, L., Adamiano, A., Siliqi, D., Giannini, C. & Iafisco, M. The effect of chemical structure of carboxylate molecules on hydroxyapatite nanoparticles. A structural and morphological study. Bioact Mater. 6, 2360–2371. https://doi.org/10.1016/j.bioactmat.2021.01.010 (2021).
Jia, R. et al. Surface modification of hydroxyapatite coating for enhanced antibiotic therapy. Coatings 14 (477). https://doi.org/10.3390/coatings14040477 (2024).
Zhou, S. et al. Hydrogen bonding interaction of poly(D,L-lactide)/hydroxyapatite nanocomposites. Chem. Mater. 19, 247–253. https://doi.org/10.1021/cm0619398 (2007).
Borum, L. & Wilson, O. C. Surface modification of hydroxyapatite. Part II. Silica Biomater. 24, 3681–3688. https://doi.org/10.1016/S0142-9612(03)00240-0 (2003).
Bogya, E. S., Barabás, R., Csavdári, A., Dejeu, V. & Bâldea, I. Hydroxyapatite modified with silica used for sorption of copper(II). Chem. Pap. 63, 568–573. https://doi.org/10.2478/s11696-009-0059-x (2009).
Ben Seddik, N. et al. Computational, theoretical and experimental studies of four amino acids as corrosion inhibitors for brass in 3% NaCl medium. J. Mol. Liq. 397, 124113. https://doi.org/10.1016/j.molliq.2024.124113 (2024).
Ling, Y. et al. Influence mechanism of Fe(II/III) doping on the adsorption of methylamine salts on kaolinite surfaces elucidated through DFT calculations. J. Mol. Liq. 390, 123082. https://doi.org/10.1016/j.molliq.2023.123082 (2023).
Danisman, M., Berisha, A., Dagdag, O. & Oral, A. Surface modification of hydroxyapatite with enzyme-catalyzed reaction: computation-supported experimental studies. Mater. Chem. Phys. 289, 126448. https://doi.org/10.1016/j.molliq.2023.123082 (2022).
Fajriyah, N. N. et al. Indonesia herbal medicine and its active compounds for anti-diabetic treatment: a systematic mini review. Moroccan J. Chem. 11(4), 948–964. https://doi.org/10.48317/IMIST.PRSM/morjchem-v11i04.40481 (2023).
Li, Y. H. et al. Seignette salt induced defects in Zr-MOFs for boosted Pb(Ⅱ) adsorption: universal strategy and mechanism insight. Chem. Eng. J. 442, 136276. https://doi.org/10.1016/j.cej.2022.136276 (2022).
Bassam, A. et al. Synthesis of geopolymer powder and beads based on red clay waste for the adsorption of methyl orange dye from aqueous solutions: characterization, application of response surface methodology, and cost analysis. Sustain. Chem. Pharm. 39, 101575. https://doi.org/10.1016/j.scp.2024.101575 (2024).
Xu, H. et al. Preparation of hierarchically floral ZIF-8 derived carbon@polyaniline@Ni/Al layered double hydroxides composite with outstanding removal phenomenon for saccharin. Chem. Eng. J. 450, 138127. https://doi.org/10.1016/j.cej.2022.138127 (2022).
Xu, H., Zhu, S., Xia, M., Wang, F. & Ju, X. Three-dimension hierarchical composite via in-situ growth of Zn/Al layered double hydroxide plates onto polyaniline-wrapped carbon sphere for efficient Naproxen removal. J. Hazard. Mater. 423, 127192. https://doi.org/10.1016/j.jhazmat.2021.127192 (2022).
Radi, S. et al. A novel environment-friendly hybrid material based on a modified silica gel with a bispyrazole derivative for the removal of ZnII, PbII, CdII and CuII traces from aqueous solutions. Inorg. Chem. Front. 4, 1821–1831. https://doi.org/10.1039/C7QI00322F (2017).
Tran, T. V. et al. Effective mitigation of single-component and mixed textile dyes from aqueous media using recyclable graphene-based nanocomposite. Environ. Sci. Pollut Res. 29, 32120–32141. https://doi.org/10.1007/s11356-022-18570-y (2022).
Bouyarmane, H. et al. Pyridine and phenol removal using natural and synthetic apatites as low cost sorbents: influence of porosity and surface interactions. J. Hazard. Mater. 181, 736–741. https://doi.org/10.1016/j.jhazmat.2010.05.074 (2010).
Khan, M. A. et al. Facile one-step economical methodology of metal free g-C3N4 synthesis with remarkable photocatalytic performance under visible light to degrade trans-resveratrol. J. Hazard. Mater. 367, 293–303. https://doi.org/10.1016/j.jhazmat.2018.12.095 (2019).
Acknowledgements
The authors extend their appreciation to the Ongoing Research Funding Program (ORF-2026-566), King Saud University, Riyadh, Saudi Arabia.
Funding
Not applicable.
Author information
Authors and Affiliations
Contributions
Conceptualization, A.B.; methodology, K.A., and O.B; software, S.L; validation, S.O, and K.A.; formal analysis, M.M.; investigation, M.EK.; resources, B.H .; data curation, S.J. and S.S; writing—original draft preparation, S.F.A, and A.B.; writing—review and editing, L.R, and, H.A.A; visualization, S.S, and B.H, All authors have read and agreed to the published version of the manuscript.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
About this article
Cite this article
Boukra, A., Boukra, O., Latifi, S. et al. Innovative sodium benzoate-modified hydroxyapatite for enhanced dye removal using a combined experimental and DFT approach. Sci Rep (2026). https://doi.org/10.1038/s41598-026-39075-5
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41598-026-39075-5