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Surface complexes of monomethyl phosphate stabilized by hydrogen bonding on goethite (alpha-FeOOH) nanoparticles

Author:
  • Per Persson
  • Tove Andersson
  • Hanna Nelson
  • Staffan Sjoberg
  • Reiner Giesler
  • Lars Lovgren
Publishing year: 2012
Language: English
Pages: 350-358
Publication/Series: Journal of Colloid and Interface Science
Volume: 386
Document type: Journal article
Publisher: Elsevier

Abstract english

Typically, a significant fraction of phosphorus in soils is composed of organic phosphates, and this fraction thus plays an important role in the global phosphorus cycle. Here we have studied adsorption of monomethyl phosphate (MMP) to goethite (alpha-FeOOH) as a model system in order to better understand the mechanisms behind adsorption of organic phosphates to soil minerals, and how adsorption affects the stability of these molecules. The adsorption reactions and stability of MMP on goethite were studied at room temperature as a function of pH, time and total concentration of MMP by means of quantitative batch experiments, potentiometry and infrared spectroscopy. MMP was found to be stable at the watergoethite interface within the pH region 3-9 and over extended periods of time, as well as in solution. The infrared spectra indicated that MMP formed three predominating pH-dependent surface complexes on goethite, and that these interacted monodentately with surface Fe. The complexes differed in hydrogen bonding interactions via the auxiliary oxygens of the phosphate group. The presented surface complexation model was based on the collective spectroscopic and macroscopic results, using the Basic Stern approach to describe the interfacial region. The model consisted of three monodentate inner sphere surface complexes where the MMP complexes were stabilized by hydrogen bonding to a neighboring surface site. The three complexes, which had equal proton content and thus could be defined as surface isomers, were distinguished by the distribution of charge over the O-plane and beta-plane. In the high pH-range, MMP acted as a hydrogen bond acceptor whereas it was a hydrogen bond donor at low pH. (C) 2012 Elsevier Inc. All rights reserved.

Keywords

  • Earth and Related Environmental Sciences

Other

Published
  • ISSN: 1095-7103
Per Persson
E-mail: per [dot] persson [at] biol [dot] lu [dot] se

Professor

MEMEG

+46 46 222 17 96

+46 70 266 38 79

E-C350

50

Professor

Centre for Environmental and Climate Research (CEC)

+46 46 222 17 96

+46 70 266 38 79

D350

Ekologihuset, Sölvegatan 37, Lund

50