Ca(OH)2 pre-treated bentonite for phosphorus removal and recovery from synthetic and real wastewater

Giorgos Markou, Dimitris Mitrogiannis, Vassilis Inglezakis, Koenraad Muylaert, Nikolaos Koukouzas, Nikolaos Tsoukalas, Efstratios Kamitsos, Dimitrios Palles, Ioannis Baziotis

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5 Citations (Scopus)


The performance of chemically pre-treated bentonite with Ca(OH)2 toward ortho-phosphate phosphorus (OPP) removal efficiency in synthetic (inorganic) and real (anaerobically digested effluents) wastewater (WW) is evaluated. The Ca(OH)2 pre-treated bentonite displays a significant increase of OPP uptake (qe; mg P g−1 bentonite) of 40 and 15 times, reaching about 14 and 5.5 mg P g−1 for synthetic and real WW, respectively. The optimum pH for OPP sorption is 7, while at higher pH values, although OPP removal is high due to the precipitation in the liquid phase, the OPP removal in solid phase, that is, sorption onto bentonite surface is less compared to pH 7. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis shows that OPP forms various complexes with co-existing ions in WW, such as apatite (with Ca2+) and struvite (with NH+4 and Mg2+). The most influential parameter of the pre-treatment is the dosage of Ca(OH)2. Concentration of 0.5 M Ca(OH)2 or higher is necessary for an efficient pre-treatment. In contrast, the concentration of bentonite does not affect the pre-treatment efficiency, and a mass of 500 g L−1 bentonite is found to be sufficient. The chemical pre-treatment with Ca(OH)2 renders bentonite a promising low-cost sorbent for OPP removal and recovery from WW.

Original languageEnglish
Article number1700378
JournalClean - Soil, Air, Water
Issue number2
Publication statusPublished - 1 Feb 2018


  • bentonite
  • ligand exchange
  • phosphorus removal
  • pre-treatment
  • sorption


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