MODEL-BASED ISOTHERM STUDIES OF SILICON ADSORPTION ON LITHOLOGICALLY CONTRASTING SOILS IN DELTA STATE, NIGERIA

The study examined model-based silicon adsorption on lithologically contrasting soils developed from different parent materials—sombreiro deltaic plain sand, mangrove swamp formation and coastal alluvium—in Delta State, Nigeria. Using stratified random sampling, soil samples were collected from three depth intervals (0–15, 15–30 and 30–60 cm) across three locations: Orogun, Ewu-Urhobo, and Koko who’s soils are developed from sombreiro deltaic plain sand, mangrove swamp formation and coastal alluvium parent materials respectively. Soil samples were treated with 50 ml of varying (50, 100, 200, 400, and 800 mg L-1) Si concentrations prepared from calcium-magnesium silicate (CaMgSiO2), and data obtained were fitted to Freundlich, Langmuir and Temkin adsorption models. Among these, Temkin model described Si sorption behavior better, showing highest average R² values of 0.290, 0.558 and 0.614 for sombreiro deltaic plain sand, mangrove swamp formation and coastal alluvium soil parent materials respectively, better R² values (0.614) was particularly observed for coastal alluvium soils. Soils from sombreiro deltaic plain sand exhibited the highest Si retention capacity with a mean value of 1932.033 compared to 1364.453 and 1727.733 obtained for mangrove swamp formation and coastal alluvium parent materials respectively. The study concludes that Temkin model is a reliable tool for predicting Si sorption in these lithologically contrasting soils in the study area.