Goethite phosphate adsorption

The interaction of phosphate with d and Na is shown in Figure 11.11. Upon adsorption of phosphate onto goethite, d adsorption dropped to zero, whereas adsorption of Na increased substantially (Nanzyo and Watanabe, 1981, 1982). It was suggested that adsorption of phosphate is followed by adsorption of additional cations at pH >7. 

Fig. 16.15 Phosphate adsorption curves of three low moor soils with different goethite content as a function of contact time (1 -238 h) (Schwertmann Schieck, 1980 with permission).

Atkinson, R.J. (1976) The formation of iron(III) oxide hydroxides from iron(III) oxalate. Aust. J. Chem. 29 2149-2158 Atkinson, R.J. Parfitt, R.L. Smart, R.S.C. (1974) Infrared study of phosphate adsorption on goethite. J. Chem. Soc. Earaday Trans. I. 70 1472-1479... 

Parfitt, R.L. Atkinson, R.J. (1976) Phosphate adsorption on goethite (a-FeOOH). Nature 264 740-742... 

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. 

Haussmann, D.D. and Anderson, M.A., 1985. Using electrophoresis in modelling sulfate, salinity and phosphate adsorption on to goethite. Environmental Science and Technology, 19 544-551. 

Using the equations and input parameters in Table 5.8 the results of a calculation involving phosphate adsorption on a goethite are shown in Fig. 5.6. 

The content and type of iron oxide affects soil chemistry. Several workers (e.g., Scheinost and Schwertmann 1995) have shown that phosphate adsorption maxima increase from red (hematitic) to yellow (goethite-rich) soils. Consequently, because yellow soils in some regions are closely correlated to soil P sorption, soil color has been used to predict the likely need for phosphate applications. 

Figure 5. Effect of pH and sodium chloride concentration on the adsorption of phosphate from a solution with an initial concentration of 340 (jM of phosphate and a goethite concentration of 3.1 g/1. Insets show the calculated values for the effects of salt concentration on the electric potential in the plane of phosphate adsorption. The concentration of sodium chloride was O.OIM, O.IM, and l.OM [40].

Other publications postulate specific adsorption between the surface and the /3-plane. For example Barrow and Bowden [69] interpreted adsorption of anions on goethite in terms of the mentioned above four layer model. The four layers are (in order of increasing distance from the surface) surface layer (H" and OH ions), the layer of specifically adsorbed anions, the first layer of inert electrolyte counterions (analogous to the /3-layer in TLM). and diffuse layer. This model requires an additional adjustable parameter, namely, the capacitance between the surface and the layer of specifically adsorbed anions. Barrow and Bowden report 2.99 F m for phosphate and 60,000 F m ( ) for silicate. The fit in the four layer model was substantially better than with simpler models for fluoride adsorption, but for other anions equally good fit could be obtained without introducing the additional electrostatic plane. In another paper of this series the capacitance of 3-5 F was used in model calculations of phosphate adsorption on aluminum and iron oxides [92]. Similar approach was used by Venema et al. [93] who applied the 1-pK model to interpret the Cd binding by goethite. The ions were assumed to... 

Rietra, R.P.J.J., Hiemstra, T. and Van Riemsdijk, W.H. (2001) Interaction between calcium and phosphate adsorption on goethite. Environmental Science and Technology 35, 3359-3374. 

Ognalaga, M., Frossard, E. and Thomas, F. (1994) Clucose-1-phosphate and myo-inositol hexa-phosphate adsorption mechanisms on goethite. Soil Science Society of America Journal 58, 332-337. 

R. L. Parfitt, J. D. Russell, and V. C. Farmer, Confirmation of the surface structures of goethite (a-FeOOH) and phosphated goethite by infrared spectroscopy, J.C.S. Faraday I 72 1082 (1976). R. L. Parfitt, Phosphate adsorption on an oxisol. Soil Sci. Soc. Am. J. 41 1065 (1977). R. L. Parfitt, R. J. Atkinson, and R. St. C. Smart, The mechanism of phosphate fixation on iron oxides. Soil Sci. Soc. Am. J. 39 837 (1975). R. L. Parfitt, The nature of the phosphate-goethite (a-FeOOH) complex formed with Ca(H2P04)2 at different surface coverage. Soil Sci. Soc. Am. J. 43 623 (1979). J. B. Harrison and V. E. Berkheiser, Anion interactions with freshly prepared hydrous iron oxides. Clays and Clay Minerals 30 97 (1982). 

Previous experience indicates that the long-term (over a period of several weeks) kinetics of phosphate adsorption and desorption on goethite is rather complex. Some of the variations in measured properties, both pH and mobility, may be attribiited to the complicated kinetic behavior of these systems. 

A possible driving force for phosphate desorption could be adsorption of phosphate on the walls of the container. Although the surface area of the goethite is ca 1000 times larger than the area of the walls of the container, any microporosity, imperfections in the wall structure or leaching into the container could affect the system. One possible approach to minimize the effects of the container is to expose them to a phosphate solution before using those containers in phosphate adsorption studies. 

As in the other surface complexation models, the chemical part consists in several adsorption reactions. In the application of the CD-MUSIC model, the choice of these reactions has been carefully based on spectroscopic evidence of course, that can be done also in other models such as TLM, BSM, and so on, but here it is rather essential for proper elucidation of the charge distribution. The original paper (Hiemstra and Van Riemsdijk 1996) applied the model to phosphate adsorption on goethite. Based on spectroscopic studies, they proposed the existence of monodentate-bound species (Reaction 12.44), an unprotonated bidentate-bound species (Reaction 12.45), and a protonated bidentate species, following ... 

Kanematsu, M., T. M. Young, K. Eukushi, P. G. Green, and J. L. Darby. 2010. Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent. Environmental Science Technology AA, no. 9 3388-3394. doi 10.1021/es903658h. 

Strauss [139] extensively studied the influence of temperature on the adsorption of phosphate on different goethite preparations between 5°C and 40°C. The influence of temperature was rather small for long equilibration times (> 1 week). At shorter times, phosphate adsorption increased with temperature. This is not in agreement with the expected trend. 

Arsenate is readily adsorbed to Fe, Mn and Al hydrous oxides similarly to phosphorus. Arsenate adsorption is primarily chemisorption onto positively charged oxides. Sorption decreases with increasing pH. Phosphate competes with arsenate sorption, while Cl, N03 and S04 do not significantly suppress arsenate sorption. Hydroxide is the most effective extractant for desorption of As species (arsenate) from oxide (goethite and amorphous Fe oxide) surfaces, while 0.5 M P04 is an extractant for arsenite desorption at low pH (Jackson and Miller, 2000). 

Liu F, De Cristofaro A, Violante A (2001) Effect of pH phosphate and oxalate on the adsorption/desorption of arsenate on/from goethite. Soil Sci 166 197-208 Livesey NT, Huang PM (1981) Adsorption of arsenate by soils and its relation to selected properties and anions. Soil Sci 131 88-94 Manceau A (1995) The mechanism of anion adsorption on iron oxides Evidence for the bonding of arsenate tetrahedra on free Fe(0, OH)6 edges. Geochim Cosmochim Acta 59 3647-3653. 

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