Sorption mechanism(s) of orthophosphate onto Ca(OH)2 pretreated bentonite

Giorgos Markou, Vassilis J. Inglezakis, Dimitris Mitrogiannis, Ilias Efthimiopoulos, Maria Psychoyou, Petros Koutsovitis, Koenraad Muylaert, Ioannis Baziotis

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Abstract

Bentonite was chemically pretreated with Ca(OH)2 to enhance orthophosphate phosphorus (OPP) sorption capacity (qe). The pretreatment resulted in an increase of qe from about 0.3 mg P per g to about 8 mg P per g at pH 7 and 25 °C, and of OPP concentration 100 mg P per L. The effects of solution pH, OPP concentration, sorbent dosage, and temperature on OPP sorption onto pretreated bentonite were investigated. The variation of initial pH (4-9) did not affect qe, however, re-adjustment of the final pH showed that the variation of the final pH had a significant positive effect on qe. The sorption kinetics showed a low rate, reaching half of qe in the first 4 h and equilibrium after 96 h. The calculated Langmuir qmax was 11.68 mg P per g. Thermodynamic analysis suggests that the sorption process is spontaneous and endothermic. Desorption of OPP was high in solutions of 0.1 M HCl and 0.01 EDTA-Na2 and reached 83% and 98%, respectively. We conclude that the predominant sorption mechanism for OPP uptake is inner-sphere surface complexation (ligand exchange). Other less important mechanisms such as surface precipitation and replacement of P5+ for Si4+ on the tetrahedral sites of montmorillonite may operate during the OPP uptake process by pretreated bentonite with Ca(OH)2.

Original languageEnglish
Pages (from-to)22295-22305
Number of pages11
JournalRSC Advances
Volume6
Issue number27
DOIs
Publication statusPublished - 2016

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Bentonite
Phosphorus
Sorption
Phosphates
Ethylenediaminetetraacetic acid
Sorbents
Clay minerals
Complexation
Edetic Acid
Desorption
Ion exchange
Ligands
Thermodynamics
Kinetics

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)

Cite this

Markou, G., Inglezakis, V. J., Mitrogiannis, D., Efthimiopoulos, I., Psychoyou, M., Koutsovitis, P., ... Baziotis, I. (2016). Sorption mechanism(s) of orthophosphate onto Ca(OH)2 pretreated bentonite. RSC Advances, 6(27), 22295-22305. https://doi.org/10.1039/c5ra27638a

Sorption mechanism(s) of orthophosphate onto Ca(OH)2 pretreated bentonite. / Markou, Giorgos; Inglezakis, Vassilis J.; Mitrogiannis, Dimitris; Efthimiopoulos, Ilias; Psychoyou, Maria; Koutsovitis, Petros; Muylaert, Koenraad; Baziotis, Ioannis.

In: RSC Advances, Vol. 6, No. 27, 2016, p. 22295-22305.

Research output: Contribution to journalArticle

Markou, G, Inglezakis, VJ, Mitrogiannis, D, Efthimiopoulos, I, Psychoyou, M, Koutsovitis, P, Muylaert, K & Baziotis, I 2016, 'Sorption mechanism(s) of orthophosphate onto Ca(OH)2 pretreated bentonite', RSC Advances, vol. 6, no. 27, pp. 22295-22305. https://doi.org/10.1039/c5ra27638a
Markou G, Inglezakis VJ, Mitrogiannis D, Efthimiopoulos I, Psychoyou M, Koutsovitis P et al. Sorption mechanism(s) of orthophosphate onto Ca(OH)2 pretreated bentonite. RSC Advances. 2016;6(27):22295-22305. https://doi.org/10.1039/c5ra27638a
Markou, Giorgos ; Inglezakis, Vassilis J. ; Mitrogiannis, Dimitris ; Efthimiopoulos, Ilias ; Psychoyou, Maria ; Koutsovitis, Petros ; Muylaert, Koenraad ; Baziotis, Ioannis. / Sorption mechanism(s) of orthophosphate onto Ca(OH)2 pretreated bentonite. In: RSC Advances. 2016 ; Vol. 6, No. 27. pp. 22295-22305.
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