Freundlich, Langmuir and Temkin isotherm studies of silicon sorption on soils derived from three parent materials in Edo State, Nigeria

The study was conducted to assess Freundlich, Langmuir, and Temkin isotherm studies of silicon sorption of soils derived from three parent materials in Edo State, Nigeria. A completely randomized design was used to collect fifteen soil samples from five depths in three replications at three locations namely, NIFOR, Uhomora, and Ososo which are developed on Coastal Plain Sand, Imo Shale, and Basement complex rock parent materials respectively. Some soil physical and chemical properties were determined according to standard procedure, in the Faculty of Agriculture laboratory, University of Benin. Samples were equilibrated in 50 ml distilled water containing various amounts of Si as Calcium-Magnesium silicate (CaMgSiO2) to give 50, 100, 200, 400, and 800 mg Si L-1 for 30 min., allowed to stand overnight, equilibrated again for 30 minutes, filtered and Si read colorimetrically. Data obtained were fitted to Freundlich, Langmuir, and Temkin adsorption models. Results showed that the Temkin model expressed Si sorption capacity better considering the R2 values of 0.733, 0.296, and 0.288 for coastal plain sand, Imo shale, and Basement complex rock soils, respectively. The soils formed on Basement complex rock adsorbed more Si than soils formed on Coastal plain sand and Imo shale parent materials, considering the mean Temkin BT (retention capacity of adsorbed Si) values. The Temkin model could be relied upon as a suitable model to determine Si sorption in soils of the study area.