Direct Observation of Phosphate Precipitation in the Goethite/Phosphate System

Martin, Ronald R.; Tazaki, Kazue; Smart, Roger St. C.

doi:10.2136/sssaj1988.03615995005200050054x

Cited by 66 publications

(42 citation statements)

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“…This slow uptake is thought to be the result of one or more of the following processes: i) diffusion to less accessible sites within pores of solid aggregates (Willet et al, 1988;Cabrera et al, 1981;Parfitt, 1989;Madrid and de Arambarri, 1985;Lookman et al, 1994); ii) penetration into the amorphous Fe and/or Al oxides by solid state diffusion (van Riemsdijk and de Haan, 1981;van Riemsdijk et al, 1984;Barrow, 1983); and iii) pre cipitation with metals derived by dissolution of the soil matrix (Aulenbach and Meisheng, 1988;Lookman et al, 1994;Martin et al, 1988;Nanzyo, 1984Nanzyo, , 1986Pierzynski et al, 1990). Malati et al (1993) reported that phosphate sorption on kaolinite, mica, and anatase at pH Ͻ 5 was endothermic and generally in the range of ϩ10 to ϩ15 kJ mol Ϫ1 .…”

Section: Phosphate Sorptionmentioning

confidence: 99%

Measuring Surface Chemical Properties of Soil Using Flow Calorimetry 1

2002

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Flow calorimetry, which is ideally suited for measuring reactions oc curring at the liquid/solid interface, has been used to study the surface chemistry of many types of solids, but little use of it has been made in the study of surface reactions of soils. The purpose of this study was to demonstrate the application of flow calorimetry to the study of two fun damental soil chemical processes, namely cation exchange and phosphate sorption. Surface horizon samples of a Typic Acrorthox and a Typic Tropohumult from Puerto Rico, a strong acid cation exchange resin (Dowex 50W-8), and an amorphous Al(OH) 3 were used. Heats for K/Ca exchange on the Dowex resin and the Oxisol, and K/Na exchange on the Ultisol, were consistent with literature values that were obtained using conventional batch calorimetry or derived from the temperature depen dence of the exchange constant. Although peak areas associated with a given pair of exchange reactions were equal, peak shapes were generally not equivalent, indicating differences in the rate at which the two reac tions occurred. For example, Ca displacing exchangeable K occurred more rapidly than the reverse reaction on the Dowex resin. The reaction of phosphate with the Ultisol and amorphous Al(OH) 3 was exothermic. Exposure of the soil to several cycles of phosphate was sufficient to sat urate the sorption sites, as evidenced by the loss of a detectable heat sig nal. However, phosphate reactive sites were regenerated by flushing the column with a salt solution at pH 10. Precipitation of Al-phosphate was shown to be endothermic, confirming that precipitation was not the pri mary mechanism for phosphate sorption in this study.

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Section: Phosphate Sorptionmentioning

confidence: 99%

Measuring Surface Chemical Properties of Soil Using Flow Calorimetry 1

2002

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“…However, the images obtained by SIMS have a spatial resolution which did not allow us to test the hypothesis of a potential, subsequent diffusion of phosphate ions into the micro-or mesoporosity of Fe oxyhydroxides (Strauss et al 1997, Torrent et al 1994. Martin et al (1988) showed by SIMS analysis (depth profile) of a naturally occurring goethite sample exposed to 10 −3 M KH 2 PO 4 solution that there was no solid-state diffusion of phosphate into goethite. These authors also showed by TEM and electron diffraction that a metal phosphate mineral (griphite) precipitated on the goethite surface.…”

Section: Location Of Phosphorus On Goethite Particlesmentioning

confidence: 99%

The use of secondary ion mass spectrometry coupled with image analysis to identify and locate chemical elements in soil minerals: The example of phosphorus

Bertrand

Grignon

Hinsinger³

et al. 2001

Scanning

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Summary:The mobility and bioavailability of elements in soils and sediments largely depends on their distribution on the diverse inorganic and organic constituents. This work addresses the example of phosphorus (P) associated to goethite and calcite, that is, to the major minerals involved in the retention of P in soils and sediments in calcareous environments. Synthetic goethite (FeOOH) and calcite (CaCO 3 ) were reacted with P prior to being analysed by dynamic secondary ion mass spectrometry (SIMS). Powdery samples were embedded in resin, cut in thin sections, and imaged with a CAMECA IMS 4F ion microscope used in scanning mode with a primary ion beam of caesium that produced negatively charged secondary ions ( − ) (Cameca, Cedex, France). Carbon, O, P, and calcium (Ca) were directly imaged at m/z 12, 16, 31, and 40, respectively, while Fe was imaged via the polyatomic ion FeO − ion at m/z 72. The SIMS data were treated by image analysis procedures. The visual comparison of images and the scatterplot method showed that P strongly interacted with goethite, probably following an adsorption process, and was thus evenly distributed at its surface. Conversely, P was not evenly distributed at the surface of calcite which rather suggests a precipitation process, and the scatterplot method confirmed a poor relationship between P and Ca. For the goethite-calcite mixture, visual examination suggested that P occurred as clusters which were largely associated with calcite, whereas a statistical analysis of the various images showed that the distribution of P was largely related to that of goethite particles. This work confirms the potential contribution of iron oxides in the retention of P in calcareous environments and shows that coupling image analysis to sensitive analytical techniques such as SIMS is a powerful approach for providing quantitative information on the location of elements at low bulk concentrations.

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“…Fe oxides seem to sorb phosphate by ligand exchange with surface OH groups monocoordinated with Fe atoms (Parfitt, 1978). However, other mechanisms, such as precipitation, cannot be excluded (Jonasson et al, 1988;Martin et aL, 1988). Synthetic goethites frequently have a phosphate sorption capacity of about 2.5/zmol P/m 2 at moderately acid to neutral pH values (Hingston, 1981;Cabrera et al, 1981;Borggaard, 1983a;Anderson et al, 1985;Torrent et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

Fast and Slow Phosphate Sorption by Goethite-Rich Natural Materials

Torrent

Schwertmann

Barrón

1992

Clays and clay miner.

170

100

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Abstract--Although phosphate sorption by goethite and other less-abundant Fe oxides strongly influences the concentration of this anion in the soil solution and aquatic environments, relatively little is known on the P-sorption characteristics of natural goethites. For this reason, we examined the P-sorption capacity and time course ofP sorption of 10 goethite-rich soil, ferricrete and lake ore samples, in which the content and nature of mineral impurities were unlikely to affect P sorption significantly. Phosphate sorption could be adequately described by a modified Freundlich equation including a time term. The amount of P sorbed after i day of equilibration at a concentration of 1 mg P/liter ranged widely (0.36-2.04 #mol P/m2). The total P sorbed after 75 days of equilibration varied less, in relative terms (1.62-3.18 #tool p/m2), i.e., a higher slow sorption tended to compensate for a lower initial (fast) sorption. Total sorbed P (X = 2.62, SD = 0.52 ~mol P/m 2) was similar to the sorption capacity of synthetic goethites, suggesting a common sorption mechanism and the predominance of one type of crystal face, which, according to previous transmission electron microscope observations, might be the (110).The extent of the slow reaction correlated to the ratio between micropore surface area and total surface area, as well as to oxalate-extractable Fe, which is an estimation of the ferrihydrite content. Ferrihydrite impurities might affect the slow reaction by contributing to the microporosity of some samples. Silicate adsorbed on the surface of the goethites was readily desorbed during phosphate sorption and did not significantly affect the extent of the slow sorption process.

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Direct Observation of Phosphate Precipitation in the Goethite/Phosphate System

Cited by 66 publications

References 0 publications

Measuring Surface Chemical Properties of Soil Using Flow Calorimetry 1

Measuring Surface Chemical Properties of Soil Using Flow Calorimetry 1

The use of secondary ion mass spectrometry coupled with image analysis to identify and locate chemical elements in soil minerals: The example of phosphorus

Fast and Slow Phosphate Sorption by Goethite-Rich Natural Materials

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