Effects of ultrasounds and microwaves on the morphology and adsorption capacity of calcium alginate

Claudia-Maria Simonescu, Petre Chipurici, Ioan Călinescu, Mircea Vînătoru, Elişoara Narcissa Toma, Daniela Cristina Culiţă, Vladimir-Lucian Ene, Timothy J. Mason

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1 Citation (Scopus)


Three non-conventional strategies have been used to prepare calcium alginate (CaAlg) from sodium alginate (NaAlg) by a batch process: ultrasound (US); microwave (MW) and combined US-MW. The calcium alginates obtained were used to remove Pb(II) and Cd(II) from single and binary aqueous solutions. The resulting adsorption capacities were compared to those obtained by conventional synthesis of calcium alginate. Scanning electron microscopy (SEM) revealed that the use of microwave and ultrasound produced CaAlg beads with roughened surfaces and consequently with increased specific surface area. The optimum parameters for the removal of Pb(II) and Cd(II) ions from single and binary solutions were determined in terms of pH, contact time, adsorbent dose and initial heavy metal concentration. A significant increase of the maximum adsorption capacity of Cd(II) and Pb(II) ions determined from Langmuir isotherm model was recorded in the case of CaAlg particles prepared in the combined microwave and ultrasound system. These values are 1.7389 ± 0.0585mmol/g for Cd(II) and 1.5872 ± 0.0657mmol/g for Pb(II) compared to 0.9305 ± 0.0926mmol/g and 0.9735 ± 0.0572mmol/g, respectively recorded for CaAlg particles prepared and matured using the conventional method. The differences between the values of the adsorption capacity of CaAlg-C-C for Pb(II) compared to Cd(II) ions is due to the Pb(II) ions characteristics (ion radius, hydrated ion radius, electronegativity). Thus, it can be stated that use of a combination of microwave and ultrasound improved the adsorption capacity of CaAlg for the removal of heavy metal ions from polluted effluents.
Original languageEnglish
Article number132906
Number of pages13
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Early online date12 Dec 2023
Publication statusPublished - 5 Feb 2024

Bibliographical note

© 2023 Elsevier B.V. All rights reserved.


This work was supported by a grant of the Ministry of Research, Innovation and Digitization, CNCS/CCCDI – UEFISCDI, project number PCE 12/2021, within PNCDI III.


  • Ultrasound and microwave-assisted synthesis
  • Heavy metal ions removal
  • Calcium alginate beads


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