A Universal Dimensionless Phosphate Adsorption Isotherm for Soil

Shayan, A.; Davey, B. G.

doi:10.2136/sssaj1978.03615995004200060007x

Cited by 30 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This observation further substantiates the importance of M-OH groups in the sorption of P by a wide range of soil types. Shayan and Davey (1978) have also shown that P sorption by soils, short-range order Al (OH),, and kaolinite may be described by a single dimensionless isotherm. The fact that the generalised isotherm for P sorption by soils follows the isotherms for P sorption by aluminous and short-range order Fe sorbents suggests the importance of soil components of this type in the sorption of P by soils.…”

Section: Resultsmentioning

confidence: 98%

Sorption of Inorganic Phosphate by Iron‐ and Aluminium‐ Containing Components

McLaughlin

Ryden

Syers

1981

Journal of Soil Science

161

View full text Add to dashboard Cite

The amounts of inorganic P sorbed by a range of Fe-and Al-containing components varied appreciably and decreased in the order allophane > fresh A1 gel > Fe gel pseudoboehmite > aged AI gel > dried Fe gel > Fe-coated kaolinite > hacmatite > goethite > akaganeite > gibbsite = ground kaolinite > dispersed kaolinite. A1 gel sorbed 30 to 70 times more P than gibbsite. and Fe gel sorbed approximately 1 0 times more P than its crystalline analogues (haematite. goethite. and akaganeite). Despite large differences in the extent of P sorption. the form o f the isotherm was essentially the same for each sorbent. The ability of freshly-prepared A1 gel suspensions to sorb P decreased with ageing, a property not shown by Fe gel. Drying of Fe gel at 80 "C. however, caused an approximately 4-fold decrease in P sorption. Precipitation of Fe gel (2% Fe) on the surface of kaolinite increased P sorption by a factor of 10. The occurrence of Fe gel as a coating apparently presents more sorption sites to solution per unit weight of Fe gel than Fe gel alone. A linear relationship ( r = 0.98) was obtained between the amount O H -sorbed per unit increase in pH value ('hydroxyl buffering') and the overall P sorption maximum for each sorbent. Hydroxyl buffering provided a better index of P sorption potential than specific surface area. Except for the crystalline Fe sorbents, isotherms obtained by plotting fractional sorption saturation against final solution P concentration for the sorbents were essentially coincident with those for several contrasting soils. For crystalline Fe components a lower relative amount of weaker sorption, as opposed to chemisorption, of the overall sorption maximum was obtained. Differences in the extent of P sorption. however. appear t o be primarily related to the number of functional M-OH groups presented at the solid-solution interface. IntroductionTHE RESULTS of several studies (Williams et af., 1958; Broomfield, 1965; Saunders, 1965;Syers et al., 1971) indicate that the sorption of inorganic phosphate (P) by soils of pH less than 7 is closely related to the amounts of reactive Fe and Al components. It is well established in the literature, however, that the Fe and Al components which occur in soils vary appreciably in their ability to sorb P. In general, short-range order (amorphous) hydrous metal oxides of Fe and Al sorb considerably greater amounts of P than do their crystalline counterparts (Gastuche et al.. 1963; Bache, 1964) and hydrous metal oxides usually sorb more P than layer silicates (Muljadi et al., 1966). Allophanic materials also sorb appreciable amounts of P (Cloos et al.. 1968).

show abstract

Section: Resultsmentioning

confidence: 98%

Sorption of Inorganic Phosphate by Iron‐ and Aluminium‐ Containing Components

McLaughlin

Ryden

Syers

1981

Journal of Soil Science

161

View full text Add to dashboard Cite

show abstract

Section: The Observations To Be Describedmentioning

confidence: 99%

A mechanistic model for describing the sorption and desorption of phosphate by soil

Barrow

2015

European J Soil Science

105

View full text Add to dashboard Cite

Summary A model of phosphate reaction is constructed and its output compared with observations for the sorption and desorption of phosphate by soil. The model has three components: first, the reaction between divalent phosphate ions and a variable‐charge surface; second, the assumption that there is a range of values of surface properties and that these are normally distributed; third, the assumption that the initial adsorption induces a diffusion gradient towards the interior of the particle which begins a solid‐state diffusion process. The model closely describes the effects on sorption of phosphate of: concentration of phosphate, pH, temperature, and time of contact. It also reproduces the effects on desorption of phosphate of: period of prior contact, period and temperature of desorption, and soil: solution ratio. The model is general and should apply to other specifically adsorbed anions and cations. It suggests that phosphate that has reacted with soil for a long period is not ‘fixed’ but has mostly penetrated into the soil particles. The phosphorus can be recovered slowly if a low enough surface activity is induced.

show abstract

“…Although the Langmuir equation has been used to describe the relation, it seldom gives a realistic description. The relation is often closely described over limited ranges by the Freundlich equation (Barrow, 1978) but over larger ranges, modifications to the Freundlich equation give a better fit (Shayan & Davey, 1978;Sibbesen, 1981). It is often found that sorption of phosphate is decreased if the pH is increased (reviewed by Sanchez & Uehara, 1980), but the effects only become large if high pH values are used.…”

Section: The Observations To Be Describedmentioning

confidence: 99%

A mechanistic model for describing the sorption and desorption of phosphate by soil

Barrow¹

1983

Journal of Soil Science

332

171

View full text Add to dashboard Cite

A model of phosphate reaction is constructed and its output compared with observations for the sorption and desorption of phosphate by soil. The model has three components: first, the reaction between divalent phosphate ions and a variable-charge surface; second, the assumption that there is a range of values of surface properties and that these are normally distributed; third, the assumption that the initial adsorption induces a diffusion gradient towards the interior of the particle which begins a solid-state diffusion process.The model closely describes the effects on sorption of phosphate of: concentration of phosphate, pH, temperature, and time of contact. It also reproduces the effects on desorption of phosphate of: period of prior contact, period and temperature of desorption, and soil : solution ratio. The model is general and should apply to other specifically adsorbed anions and cations. It suggests that phosphate that has reacted with soil for a long period is not 'fixed' but has mostly penetrated into the soil particles. The phosphorus can be recovered slowly if a low enough surface activity is induced.

show abstract

A Universal Dimensionless Phosphate Adsorption Isotherm for Soil

Cited by 30 publications

References 0 publications

Sorption of Inorganic Phosphate by Iron‐ and Aluminium‐ Containing Components

Sorption of Inorganic Phosphate by Iron‐ and Aluminium‐ Containing Components

A mechanistic model for describing the sorption and desorption of phosphate by soil

A mechanistic model for describing the sorption and desorption of phosphate by soil

Contact Info

Product

Resources

About