Adsorption-desorption mechanism of phosphate by immobilized nano-sized magnetite layer: Interface and bulk interactions

Adva Zach-Maor, Raphael Semiat, Hilla Shemer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


Phosphate adsorption mechanism by a homogenous porous layer of nano-sized magnetite particles immobilized onto granular activated carbon (nFe-GAC) was studied for both interface and bulk structures. X-ray Photoelectron Spectroscopy (XPS) analysis revealed phosphate bonding to the nFe-GAC predominantly through bidentate surface complexes. It was established that phosphate was adsorbed to the magnetite surface mainly via ligand exchange mechanism. Initially, phosphate was adsorbed by the active sites on the magnetite surface, after which it diffused into the interior of the nano-magnetite layer, as indicated by intraparticle diffusion model. This diffusion process continues regardless of interface interactions, revealing some of the outer magnetite binding sites for further phosphate uptake. Desorption, using NaOH solution, was found to be predominantly a surface reaction, at which hydroxyl ions replace the adsorbed phosphate ions only at the surface outer biding sites. Five successive fix-bed adsorption/regeneration cycles were successfully applied, without significant reduction in the nFe-GAC adsorption capacity and at high regeneration efficiency.

Original languageEnglish
Pages (from-to)608-614
Number of pages7
JournalJournal of Colloid and Interface Science
Issue number2
StatePublished - 15 Nov 2011
Externally publishedYes


  • Composite adsorbent
  • Fixed-bed
  • Iron oxide
  • Saturation
  • XPS

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