Langmuir and Freundlich Isotherm Models’ Description of P. Adsorption Capacity of Wetland and Upland Soil in Rivers State (Published)
Soil samples from pedons of selected wetland and upland soils of Rivers State Nigeria were collected to investigate the appropriate P-Adsorption models, under different parameters namely, soil physicochemical properties and Phosphorus Sorption Isotherm models. The phosphorus sorption data were obtained by equilibrating 3g of soil samples in 30ml, 0.01M CaCl2 containing various amount of KH2P04 (0, 5, 10, 15, 20 and 25ppm). Linear and Non-linear regression methods were used to determine the best fit of equilibrium data. The two-parameter models: Freundlich and Langmuir were employed for fitting the equilibrium data. The study revealed that both Langmuir and Freundlich Isotherm were suitable to describe adsorption of Phosphorus for the six pedons. However, Freudlich Isotherm model explained P-adsorption better than Langmuir Isotherm model. The highest phosphorus sorption capacity of 333.33mg/kg was found in Obor 1, Obor 2 and RSU followed by Isu (0.00mg/kg), Eagle-Island (-333.33mg/kg) and Ozuzu (-125mg/kg). The value of the separation factor of the Langmuir Isotherm RL lying in between O and < 1 for Obor1, Obor 2 and RSU indicating that isotherm processes are favourable and < 0 which indicate desorption for Eagle Island and Ozuzu. While 1 suggesting Linear adsorption for Isu. Similarly, the Freundlich Isotherm intensity parameter 1/n fell in between O and < 1, and > 1 indicating favourable for Obor1, Obor 2, RSU, Isu and Unfavourable for Eagle–Island and Ozuzu respectively. The optimum time for phosphate adsorption onto soil was found to be 120 minutes for Obor 1, Obor 2, RSU, Ozuzu, Isu and Eagle Island for both models. The amount P-sorbed increased with increase in time.
Keywords: Adsorption, Freundlich, Isotherm, Langmuir, Models, Soil, Upland, Wetland, phosphate