Ferrihydrite, phosphate adsorption

Arai,Y. Sparks, D.L. (2001) ATR-ETIR spectroscopic investigation on phosphate adsorption mechanisms at the ferrihydrite-water interface. J. Coll. Int. Sd. 241 317—326 Araki, S. Hirai, H. Kyuma, K. (1986) Phosphate absorption of red and/or yellow colored soil materials in relation to the characteristics of free oxides. Soil Sd. Plant Nutr. 32 609-616... 

Phosphate adsorption and desorption by goethites differing in crystal morphology. Soil Sd. Soc. Am. J. 54 1007-1012 Torrent, J. Guzman, R. Parra, M.A. (1982) Influence of relative humidity on the crystallization of Fe(III) oxides from ferrihydrite. Clays Clay Min. 30 337-340 Torrent, J. Schwertmann, U. Barron,V. 

Rhoton, F.E. and Bigham, J.M. (2005) Phosphate adsorption by ferrihydrite-amended soils. Journal of Environmental Quality, 34(3), 890-96. 

Aral, Y., and Sparks, D. L. (2001). ATR-FTIR spectroscopic investigation on phosphate adsorption mechanisms at the ferrihydrite-water interface. J. Colloid Interface Sci. 241, 317-326. 

Pigna M, Colombo C, Violante A (2003) Competitive sorption of arsenate and phosphate on synthetic hematites (in Italian). Proceedings XXI Congress of Societa Italiana Chimica Agraria SICA (Ancona), pp 70-76 Quirk JP (1955) Significance of surface area calculated from water vapour sorption isotherms by use of the B. E. T. equation. Soil Sci 80 423-430 Rancourt DG, Fortin D, Pichler T, Lamarche G (2001) Mineralogical characterization of a natural As-rich hydrous ferric oxide coprecipitate formed by mining hydrothermal fluids and seawater. Am Mineral 86 834-851 Raven K, Jain A, Loeppert, RH (1998) Arsenite and arsenate adsorption on ferrihydrite kinetics, equilibrium, and adsorption envelopes. Environ Sci Technol 32 344-349... 

The four layer model (Bowden et ah, 1980 Bousse and Meindle, 1986) also locates different adsorbing ions in different planes. It has been used to model adsorption of phosphate, citrate and selenite (Bowden et ah, 1980) and borate (Bloesch et al., 1987) on goethite and competitive adsorption of Ca and Cd on ferrihydrite (Cowan et al., 1991). 

Acta Cryst. B39 165-170 Pauling, L. Hendricks, S.B. (1925) The crystal structures of hematite and corundum. J. Am. Chem. Soc. 47 781-790 Pauling, L. (1929) The principles of determining the structure of complex ionic crystals. J. Amer. Chem. Soc. 51 289-296 Payne, J.E. Davis, J.A. Waite,T.D. (1996) Uranium adsorption on ferrihydrite — effect of phosphate und humic add. Radiochemica Acta 74 239-243... 

Figure 5. Effect of phosphate on adsorption of As(V) and As(lII) by ferrihydrite. Ionic strength, 0.1 M concentration of ferrihydrite, 2 g/L (Modified from Jain and Loeppert, 2000).

Adsorption of myo-inositoi hexakisphosphate on another metal oxide, ferrihydrite, is believed to occur through two of the six phosphate groups (Celi et al., 2003). 

Adsorption of As on selected sorbents (ferrihydrite, noncrystalline Al-hydroxide, and Andisol) was determined at pH values ranging from 4.0 to 8.0. Suitable amounts of As were added to an Andisol sample at pH 4.5 as a mixture with LMMOAs (OX, MAL, or citrate) or phosphate in order to have a maximum surface coverage of As (as determined by adsorption isotherms) and an initial orgaitic ligand or phosphate/As molar ratios ranging from 0 to 5. 

Arsenate adsorption on ferrihydrite consisted of a period of rapid uptake followed by slow adsorption for at least 8 days 43). The rate of the slow adsorption reaction is considered to be limited by diffusion into the ferrihydrite aggregates. Slow adsorption kinetics similar to those for phosphate are expected for arsenate because of the similar chemistry of these two anions. Arsenate adsorption data adhere to the Elovich kinetic model indicating a diffusion limited reaction. Arsenate desorption rates were much slower than arsenate adsorption rates, also consistent with a diffusion limited process. A model was developed that assumes that 63% of adsorbing sites are located at the exteriors of aggregates and reach arsenate equilibrium rapidly, while 37% of adsorbing sites are located in the interiors of aggregates with access being diffusion limited. 

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