Desorption of Phosphate From Soils Using Anion Exchange Resins

Abstract

After 1 (H)h reaction with CI-resin and 300h reaction with HCO3-resin (approaching equilibrium). the concentration of anions complementary to phosphate was the critical variable affecting the transfer of P from soil to resin. Solution ccmcentrations of H30+, ca?+ and phosphate indicated that desorption of P by OH-, and dissolution of Ca phosphates, controlled P release from soils. P extracted by HC03-resin was much greater than by CI-resin from an acid soil. due to lower total anion and higher desorbing anion concentrations. but there was little difference between the two resins with a calcareous soil. HCO-resin extracted a constant proportion of isotopically-exchangeable P from different soils whereas CI-resin did not. Anion exchange resins provide a convenient means for producing P desorption curves for soils. introduc lion A N I O N -E X C H A N G E resins are frequently used to extract plant-available phosphate from soils (Amer et al., 1955; Cooke and Hislop, 1963). The resin method gives better correlation with P uptake by plants than other methods using single extractants (Gunary and Sutton, 1967; Bache and Rogers, 1970; Metwally et al., 1975; Kadeba and Boyle, 1978) presumably because it simulates the desorbing effect of plant roots better than the usual chemical extractants. Desorption from soil occurs as a result of the low P concentration that the resin maintains in solution, and Barrow and Shaw (1977) concluded that this concentration governs the P desorbed in a given time. Vaidyanathan and Talibudeen (1970) suggested that the rate of P transfer to the resin was controlled by diffusion within resin particles rather than by chemical reactions between soil and solution, whereas Sibbesen (1978) concluded that P desorption from soil to water was the rate-determining step.We report here P adsorbed by the resin as a function of time, resin concentration, salt concentration and the desorbing anion, and also the pH and concentrations of Ca and P in the soil-resin-solution system. The results provide further information on mechanisms of P release from soil by resins.

Potential and limitations of phosphate retention media in water protection: A process-based review of laboratory and field-scale tests

“…As Figure 1 [adapted from Sigg and Stumm (1981) and Bache and Ireland (1980)] shows, the reaction is considered reversible. If some change in the Al/Fe oxide-water system (e.g.…”

Determination of ‘labile’ phosphate in lake sediments using anion exchange resins: a critical evaluation

“…A direct link between the amount of phosphate transferred to the exchanger resin and the amount ofP taken up by a crop grown on the soils has been found in some studies (Moser et al, 1959;Cooke and Hislop, 1963). Later investigations demonstrated that the analytical result can vary with the experimental parameters used, and this has led some authors (Barrow and Shaw, 1977;Bache and Ireland, 1980) to propose that there is no single value for resin extractable phosphorus.…”

“…Other investigators have shown that the magnitude of the fraction transferred can be strongly influenced by the concentration of complementary salts in the aqueous phase. This parameter can vary with the volume of water present and the amount of exchanger used (Cooke and Hislop, 1963;Bache and Ireland, 1980). In one study (Brewster et al, 1975), the log of the water phase phosphate content (In Ps) was found to be linearly related to the total amount of P desorbed from the soil.…”

“…In soil studies, the recommended interaction times range from 16 hours (Cooke and Hislop, 1963) to 300 hours (Bache and Ireland, 1980), with the time required to achieve a pseudo equilibrium state tending to vary with experimental parameters. It has been noted, for example, that the rate of P desorption decreased on increasing the volume of water used (i.e.…”

“…It has been noted, however, that near quantitative retrieval of the P taken up by the exchanger requires multi-stage back-extraction procedures or resin destruction. For example, the exchanger phase was either washed repeatedly with small volumes of acidified NaCl (Barrow and Shaw, 1977;Bache and Ireland, 1980); or was boiled with small volumes of I M NazS04 (Brewster et al, 1975). Other approaches used include transfer of P-loaded resin into a small column before elution with IM NazS04 (Cooke and Hislop, 1963); and ashing the resin, followed by dissolution of the ash in HCI (Vaidyanathan and Talibadeen, 1970).…”