Adsorption thermodynamics of phosphate on sediments of tropical backwater system

Abstract

The effect of phosphate concentrations, contact time, pH, diverse ions and temperature on adsorption of phosphate by sediments from retting and non-retting zones have been studied. The percent phosphate adsorbed increased with decrease in initial concentration of phosphate and increase in temperature. The adsorption capacity increased with decrease in pH, being the highest at an initial pH of 3.5. The adsorption isotherms of phosphate follow the Freundlich model and yield 'L' class for retting zone sediments and 'S' class for non-retting sediments. The thermodynamic equilibrium constant (K-0), standard free energy (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees) changes were also being evaluated to predict the nature of adsorption.