Adsorption of phosphate by two iron oxides in relation to their porosity

Madrid, L.; Arambarri, Pablo de

doi:10.1111/j.1365-2389.1985.tb00355.x

Cited by 64 publications

(40 citation statements)

References 18 publications

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“…A previous study [17] reported that the pores on goethite surface were 20-30 nm in width and became narrower to 2 nm or less towards the interior of the crystals. Radius for phosphate was 0.22 nm; it was therefore possible for phosphate to diffuse into the pores or to block the pore entrances [20,21], which was confirmed by the decreased average pore volume after phosphate modification through the pore volume analysis in Table 1.…”

Section: Specific Surface Area and Pore Volume Analysismentioning

confidence: 67%

Surface modification of goethite by phosphate for enhancement of Cu and Cd adsorption

Zhang

Shan

2007

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Section: Specific Surface Area and Pore Volume Analysismentioning

confidence: 67%

Surface modification of goethite by phosphate for enhancement of Cu and Cd adsorption

Zhang

Shan

2007

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…The multiple-rate characteristic of phosphate adsorption is possibly related to the heterogeneity of adsorption sites. The different accessibility of surface pores and multiple sorption sites with different binding strengths result in an apparent heterogeneity of the surface (Benjamin and Leckie 1981;Madrid and de Arambarri 1985;Hiemstra et al 1989a,b) and would cause differences in the adsorption rate. The phosphate adsorption may replace the positively charged OH 2 groups through ligand exchange and, thus, tends to lower the positive surface potential and increase negative charge (Parfitt and Atkinson 1976).…”

Section: Rates Of Phosphate Adsorptionmentioning

confidence: 99%

“…The kinetics of phosphate adsorption by pure Fe oxides has been intensively studied over the last two decades (Kuo and Lotse 1973;Parfitt and Atkinson 1976;Anderson et al 1985;Bolan et al 1985;Hansmann and Anderson 1985;Madrid and de Arambarri 1985;Shang et al 1993). However, pure Fe oxides seldom occur in natural environments, since other ions present in the environment can influence their formation (Krishnamurti and Huang 1990;Cornell and Schwertmann 1996).…”

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confidence: 99%

Kinetics of phosphate adsorption on iron oxides formed under the influence of citrate

Liu¹,

Huang²

2000

Can. J. Soil. Sci.

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. 2000. Kinetics of phosphate adsorption on iron oxides formed under the influence of citrate. Can. J. Soil Sci. 80: [445][446][447][448][449][450][451][452][453][454]. The influence of organic acids on the formation of Fe oxyhydroxides and oxides has been intensively studied. However, scant attention has been paid to the subsequent effect on surface chemistry of the Fe oxides formed. The kinetics and mechanisms of phosphate adsorption by the Fe oxides formed in the presence of citrate ligands at initial citrate/Fe(II) molar ratios (MR) of 0, 0.001, 0.01, and 0.1 were investigated using the conventional batch method. The adsorption studies were conducted at the initial phosphate concentration of 0.5 mM and pH 4.0 during the reaction period from 2 min to 56 h at 278, 288, 298, and 313 K. The results show that the phosphate adsorption followed multiple second-order kinetics and had two distinct rates in each reaction system. The amount, rate coefficient, activation energy and pre-exponential factor of phosphate adsorption by the Fe oxides formed greatly varied with their structural and surface properties. These properties, which included crystal structure, specific surface area, surface porosity, surface geometry, and point of zero salt effect (PZSE), differed significantly with the initial citrate/Fe(II) MR at which Fe oxides were formed. The results of this study have cast the light on the role of organic acids such as citric acid in influencing the surface chemistry of naturally occurring Fe oxides through fundamental structural perturbation and the impact on the dynamics of phosphate in terrestrial and aquatic environments.Key words: Kinetics, activation energy, pre-exponential factor, phosphate, iron oxides, citric acid, structural perturbation Liu, C. et Huang, P. M. 2000. Cinétique de l'adsorption des phosphates sur les oxydes de fer formés sous l'influence des citrates. Can. J. Soil Sci. 80: 445-454. Bien que l'influence des acides organiques sur la formation des oxyhydroxydes et des oxydes de fer ait fait l'objet d'études intensives, on s'est peu intéressé à l'effet des oxydes ainsi formés sur la chimie du sol de surface. Nous étudions selon la méthode classique par fractionnement la cinétique et les mécanismes de l'adsorption des phosphates sur les oxydes de Fe formés en présence de ligands de citrate, pour des rapports molaires (RM) citrates/Fe (II) de 0, 001, 0,01 et 0,1. Les études d'adsorption étaient réalisées à la concentration initiale de phosphate de 0,5 mM au pH 4,0 durant des périodes allant de 2 min à 56 h, à 278, 288, 298 et 313 K. Les résultats obtenus montrent que l'adsorption du phosphate suivait une cinétique multiple du second degré comportant deux taux distincts, dans chaque système de réaction. La quantité, le coefficient de taux, l'énergie d'activation et le facteur pré-exponentiel d'adsorption des phosphates sur les oxydes de Fe formés variaient grandement selon les propriétés structurales et les propriétés de surface des oxydes : structure cristalline, surface spécifique, porosité, ...

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“…Rapid P adsorption presumably results from the reaction of P with surface sites on Fe oxides (Parfitt 1978). Slow P adsorption has been attributed to slow diffusion into Fe-oxide crystals (Barrow 1983;Parfitt 1989) or aggregates of crystals (Madrid and Arambarri 1985;Willett et al 1988;Torrent et al 1992), as well as slow formation of P-containing precipitates (Van Riemsdijk et al 1984). Slow adsorption is usually found to be more pronounced for poorly ordered Fe oxides (e.g.…”

mentioning

confidence: 99%

The role of adsorption in sediment-water exchange of phosphate in North Sea continental margin sediments

Slomp¹,

Malschaert²,

Raaphorst³

1998

Limnol. Oceanogr.

159

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The effect of adsorption on the sediment-water exchange of PO, was investj gated in sediments from four different types of sedimentary environments in the southern and eastern North Sea in August 1991 and February 1992. Nonlinear adsorption isotherms for oxidized sediment from eight stations indicate that North Sea sediments differ widely in their capacity to adsorb PO,. A good correlation between the value of the adsorption coefficient and NH,-oxalate-extractable Fe was observed. A combination of the adsorption data with Porewater PO, profiles, solid phase results, and measured and calculated rates of sediment-water exchange of PO, for 15 stations in both August and February indicates that adsorption plays an important role in controlling sediment-water exchange of PO, during at least a part of the year in three of the four North Sea environments. At most stations, PO, adsorption constrains the flux of PO, to the overlying water. At one station in the depositional environment of the Skagcrrak, however, desorption is responsible for the maintenance of a flux of PO, to the overlying water. A one-dimensional reactiondiffusion model, describing Porewater PO, and solid phase P profiles, was de*deloped and applied to results for two stations. The model results show that both enhanced retention and enhanced release of PO, can be adequately described when simultaneous equilibrium and first-order kinetic reversible adsorptive reactions are assumed.A substantial proportion (lo-50%) of pelagic primary production reaches the sea floor in continental margin environments (Jorgensen 1983). When this organic material is mineralized in the sediment, a release of dissolved PO, to the pore water results. This PO, can be retained in the sediment, but it may also escape to the overlying water, where it once again can become available for uptake by phytoplankton (e.g. Howarth et al. 1995).Phosphorus (P) retention and release in marine sediments on short time-scales are usually considered to be redox-dependent. When an oxidized surface layer is present, substantial amounts of PO, can be retained in the sediment through adsorption to Fe oxides (e.g. Krom and Berner 1980b, 198 1;Sundby et al. 1992;Jensen et al. 1995). This adsorption process generally results in a buffering of Porewater PO, concentrations to low values in the oxidized sediment zone (Froelich 1988;Sundby et al. 1992), thus allowing only limited diffusive transport of PO, to the overlying water. When, in contrast, the oxidized surface layer is thin or absent, the PO, released from organic matter and from Fe oxides upon their reduction can escape to the overlying water. This was first described for lake sediments by Einsele (1936) and Mortimer (1941Mortimer ( , 1942. Redox-dependent sediment PO, re-I Present address: Department of Geochemistry, Institute of Earth Sciences, Utrecht University, Budapcstlaan 4, 3584 CD Utrecht, The Netherlands. AcknowledgmentsWe thank the crew of RV Pehgia for their help during the cruises and A. J. J. Sandcc for the grain size analy...

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Adsorption of phosphate by two iron oxides in relation to their porosity

Cited by 64 publications

References 18 publications

Surface modification of goethite by phosphate for enhancement of Cu and Cd adsorption

Surface modification of goethite by phosphate for enhancement of Cu and Cd adsorption

Kinetics of phosphate adsorption on iron oxides formed under the influence of citrate

The role of adsorption in sediment-water exchange of phosphate in North Sea continental margin sediments

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