Phosphate sorption by calcium‐bentonite as described by commonly used isotherms

Abstract The one and two Langmuir, the Freundlich, and the Temkin isotherms were fitted to phsophorus (P) sorption data for P sorption by calcium (Ca)‐bentonite at different initial concentration and pH values of 3.8, 4.8, 6.0, 7.0, 8.0, and 9.0. Each was found to describe P sorption by Ca‐bentonite with comparable success. The effect of pH on P adsorption by Ca‐bentonite was studied and Langmuir, Temkin, and Freundlich isotherms were converted to the forms: Langmuir: (Co‐X)X= 1/(0.0275–0.0025pH)(12.323–1.061pH) + (Co‐X)(12.323–1.016pH) Temkin: X = (2.45–0.211pH)In(AC) Freundlich: X = (1.324–0.146pH)C(0.172+0044 P H) where: X = (mmol P/kg) the amount of P sorbed per unit weight of soil, C = (μmol P/L) the P concentration in the equilibrium solution, and Co = ((μmol P/L) initial P concentration. It is noteworthy, that the maximum amount (Xm) of P that can be sorbed in a monolayer decreases by increasing of pH. Finally, the B constant of Temkin isotherms is indepented from pH changes.

[1]  M. Said,et al.  Phosphate adsorption and desorption by calcareous soils of Syria , 1993 .

[2]  G. Sposito.  On the Use of the Langmuir Equation in the Interpretation of ``Adsorption'' Phenomena: II. The ``Two-Surface'' Langmuir Equation1 , 1982 .

[3]  J. Mead.  A comparison of the Langmuir, Freundlich and Temkin equations to describe phosphate adsorption properties of soils , 1981 .

[4]  G. Sposito.  Derivation of the Freundlich equation for ion exchange reactions in soils. , 1980 .

[5]  N. Barrow.  The description of phosphate adsorption curves , 1978 .

[6]  J. Quirk,et al.  Corrigenda - Ionic adsorption on variable charge mineral surfaces. Theoretical charge development and titration curves , 1977 .

[7]  A. Fitter,et al.  THE USE OF THE FREUNDLICH ISOTHERM FOR SOIL PHOSPHATE SORPTION DATA , 1975 .

[8]  R. W. Wedderburn,et al.  A LANGMUIR TWO-SURFACE EQUATION AS A MODEL FOR PHOSPHATE ADSORPTION BY SOILS , 1974 .

[9]  D. Gunary.  A NEW ADSORPTION ISOTHERM FOR PHOSPHATE IN SOIL , 1970 .

[10]  J. Quirk,et al.  THE MECHANISM OF PHOSPHATE ADSORPTION BY KAOLINITE, GIBBSITE, AND PSEUDOBOEHMITE , 1966 .

[11]  P. Hsu.  Adsorption of Phosphate by Aluminum and Iron in Soils1 , 1964 .

[12]  S. R. Olsen,et al.  A Method to Determine a Phosphorus Adsorption Maximum of Soils as Measured by the Langmuir Isotherm1 , 1957 .

[13]  P. F. Low,et al.  Reaction of Phosphate with Kaolinite in Dilute Solution 1 , 1954 .

[14]  P. F. Low,et al.  REACTIONS OF PHOSPHATE WITH KAOLINITE , 1950 .