Kinetics of Phosphate Adsorption and Desorption by Lake Sediments

Abstract The objectives of the present investigation were to gain information on the rate and extent of phosphate adsorption and desorption and the energy of phosphate adsorption by lake sediments, and to evaluate the influence of the sediments on the phosphorus status of lake waters. While phosphate adsorption by sediments from Sebasticook Lake, Maine, could be described by the Freundlich equation over a large phosphorus concentration range, the Langmuir equation provided a good fit to the experimental data only at low phosphorus concentrations. The deviation from the Langmuir isotherm at high phosphorus concentrations was explained by an increase in total negative potential of the surface due to phosphorus adsorption and increased interaction between adsorbate molecules. The rate of phosphorus adsorption by the sediments could be described by the equation X = KC 0 t 1/ m . The calculated activation energy was 2.7 kcal/mole. The desorption of phosphorus from minerals and sediments was dependent on the anionic species present in the solution. The replacing power of the anions appeared to be related to their ionic potential and complexing ability. The rate of phosphorus desorption could be described by the proposed kinetic equation.