Mechanisms of Phosphate Sorption by Soils and Hydrous Ferric Oxide Gel

Ryden, J. C.; McLaughlin, John; Syers, J. K.

doi:10.1111/j.1365-2389.1977.tb02297.x

Cited by 209 publications

(92 citation statements)

References 33 publications

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“…For example, the PO 4 3− removal rate decreased from 100 % at around pH 3.1 to about 32 % at pH 10.9. Similar pH effect on phosphate ions sorption by iron or iron-based oxides has been reported by a number of authors (Ryden and McLaughlin 1977;Zhang et al 2009). Such phenomenon could be explained as follows: negativecharged H 2 PO 4 − and HPO 4 2− are dominant phosphate species in the solution under the tested pH range (3-11).…”

Section: Effect Of Ph and Ionic Strength On Phosphate Uptakesupporting

confidence: 59%

Adsorption of Phosphate from Aqueous Solution Using an Iron–Zirconium Binary Oxide Sorbent

Ren

Shao

Zhang

2012

Water Air Soil Pollut

119

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In this study, an iron-zirconium binary oxide with a molar ratio of 4:1 was synthesized by a simple coprecipitation process for removal of phosphate from water. The effects of contact time, initial concentration of phosphate solution, temperature, pH of solution, and ionic strength on the efficiency of phosphate removal were investigated. The adsorption data fitted well to the Langmuir model with the maximum P adsorption capacity estimated of 24.9 mg P/g at pH 8.5 and 33.4 mg P/g at pH 5.5. The phosphate adsorption was pH dependent, decreasing with an increase in pH value. The presence of Cl − , SO 4 2− , and CO 3 2− had little adverse effect on phosphate removal. A desorbability of approximately 53 % was observed with 0.5 M NaOH, indicating a relatively strong bonding between the adsorbed PO 4 3− and the sorptive sites on the surface of the adsorbent. The phosphate uptake was mainly achieved through the replacement of surface hydroxyl groups by the phosphate species and formation of innersphere surface complexes at the water/oxide interface. Due to its relatively high adsorption capacity, high selectivity and low cost, this Fe-Zr binary oxide is a very promising candidate for the removal of phosphate ions from wastewater.

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Section: Effect Of Ph and Ionic Strength On Phosphate Uptakesupporting

confidence: 59%

Adsorption of Phosphate from Aqueous Solution Using an Iron–Zirconium Binary Oxide Sorbent

Ren

Shao

Zhang

2012

Water Air Soil Pollut

119

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“…As can be seen, the phosphate removal was evidently dependent on pH with the greatest adsorption occurring under acidic conditions and decreased with increase in solution pH. Such pH effect has been observed for the sorption of phosphate onto iron oxides [36,37]. H 2 PO 4 À and HPO 4 2À are dominant phosphate species in the solution under the tested pH range (3-10).…”

Section: Effect Of Ph and Ionic Strengthmentioning

confidence: 55%

Removal of phosphate from water by a Fe–Mn binary oxide adsorbent

Zhang

Liu

et al. 2009

Journal of Colloid and Interface Science

386

155

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a b s t r a c tPhosphate removal is important in the control of eutrophication of water bodies and adsorption is one of the promising approaches for this purpose. A Fe-Mn binary oxide adsorbent with a Fe/Mn molar ratio of 6:1 for phosphate removal was synthesized by a simultaneous oxidation and coprecipitation process. Laboratory experiments were carried out to investigate adsorption kinetics and equilibrium, in batch mode. The effects of different experimental parameters, namely contact time, initial phosphate concentration, solution pH, and ionic strength on the phosphate adsorption were investigated. The adsorption data were analyzed by both Freundlich and Langmuir isotherm models and the data were well fit by the Freundlich isotherm model. Kinetic data correlated well with the pseudo-second-order kinetic model, suggesting that the adsorption process might be chemical sorption. The maximal adsorption capacity was 36 mg/g at pH 5.6. The phosphate adsorption was highly pH dependent. The effects of anions such as Cl À ; SO 4 2À , and CO 3 2À on phosphate removal were also investigated. The results suggest that the presence of these ions had no significant effect on phosphate removal. The phosphate removal was mainly achieved by the replacement of surface hydroxyl groups by the phosphate species and formation of inner-sphere surface complexes at the water/oxide interface. In addition, the adsorbed phosphate ions can be effectively desorbed by dilute NaOH solutions. This adsorbent, with large adsorption capacity and high selectivity, is therefore a very promising adsorbent for the removal of phosphate ions from aqueous solutions.

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“…Therefore, a-and c-Fe oxide-associated P present in NaOH-Na 2 EDTA extracts was probably attached to the surface of Fe oxides. Alkaline extraction could remove P held to Fe and Al components of soil surface by chemisorption (Hedley et al, 1982;McLaughlin et al, 1977;Ryden et al, 1977). It is worth noting that there was unavoidable P release from P-goethite complexes after oxalate treatment by ligand exchange; the amount of released P was negligible at low initial P level (Johnson and Loeppert, 2006), as was the case in our soil samples.…”

Section: Naoh-na 2 Edta-extractable P Associated With Fe and Al Oxidementioning

confidence: 77%

“…This is in contrast to the a-and c-Fe oxide-associated P present in NaOHNa 2 EDTA extracts which were absorbed on the surface of Fe oxides. The P associated with Fe oxides in residual fractions was probably held at the internal surfaces of Fe oxides by chemisorption at protonated surface sites or by the replacement of surface hydroxyls in soil aggregates (Hedley et al, 1982;Ryden et al, 1977) or diffused into the bulk of Fe oxides or into pores and defects . This means that, with the changes in soil conditions (e.g., soil anoxic condition, acidic condition, high concentrations of organic acid or siderophores; Forsmann and Kjaergaard, 2014;Kraemer, 2004) when Fe oxides become dissolved, P associated with the Fe oxides may become available to plants or the microbial population.…”

Section: Residual P In Soil Aggregate-sized Fractionsmentioning

confidence: 99%

Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil

Jiang¹,

Bol²,

Willbold³

et al. 2015

Biogeosciences

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Abstract. To maximize crop productivity fertilizer P is generally applied to arable soils, a significant proportion of which becomes stabilized by mineral components and in part subsequently becomes unavailable to plants. However, little is known about the relative contributions of the different organic and inorganic P bound to Fe/Al oxides in the smaller soil particles. Alkaline (NaOH-Na 2 EDTA) extraction with solution 31 P-nuclear magnetic resonance ( 31 P-NMR) spectroscopy is considered a reliable method for extracting and quantifying organic P and (some) inorganic P. However, any so-called residual P after the alkaline extraction has remained unidentified. Therefore, in the present study, the amorphous (a) and crystalline (c) Fe/Al oxide minerals and related P in soil aggregate-sized fractions (> 20, 2-20, 0.45-2 and < 0.45 µm) were specifically extracted by oxalate (a-Fe/Al oxides) and dithionite-citrate-bicarbonate (DCB, both a-and c-Fe/Al oxides). These soil aggregate-sized fractions with and without the oxalate and DCB pre-treatments were then sequentially extracted by alkaline extraction prior to solution 31 P-NMR spectroscopy. This was done to quantify the P associated with a-and c-Fe/Al oxides in both alkaline extraction and the residual P of different soil aggregate-sized fractions.The results showed that overall P contents increased with decreasing size of the soil aggregate-sized fractions. However, the relative distribution and speciation of varying P forms were found to be independent of soil aggregate-size. The majority of alkaline-extractable P was in the a-Fe/Al oxide fraction (42-47 % of total P), most of which was orthophosphate (36-41 % of total P). Furthermore, still significant amounts of particularly monoester P were bound to these oxides. Intriguingly, however, Fe/Al oxides were not the main bonding sites for pyrophosphate. Residual P contained similar amounts of total P associated with both a-(11-15 % of total P) and c-Fe oxides (7-13 % of total P) in various aggregate-sized fractions, suggesting that it was likely occluded within the a-and c-Fe oxides in soil. This implies that, with the dissolution of Fe oxides, this P may be released and thus available for plants and microbial communities.

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Mechanisms of Phosphate Sorption by Soils and Hydrous Ferric Oxide Gel

Cited by 209 publications

References 33 publications

Adsorption of Phosphate from Aqueous Solution Using an Iron–Zirconium Binary Oxide Sorbent

Adsorption of Phosphate from Aqueous Solution Using an Iron–Zirconium Binary Oxide Sorbent

Removal of phosphate from water by a Fe–Mn binary oxide adsorbent

Speciation and distribution of P associated with Fe and Al oxides in aggregate-sized fraction of an arable soil

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