Sorption Isotherms, Kinetics, and Thermodynamics of Contaminants in Indian Soils

Abstract

The sorption isotherms, kinetics, and thermodynamics of contaminants, e.g., strontium, lead, and uranium, for four different Indian soils (named S1, S2, S3, and S4) were investigated. Batch testing was performed to determine sorption properties of the soils. It was found that among the four soils, S1 has the maximum sorption at each contaminant metal. The uptake capacity for strontium, lead, and uranium was found to be 55.78, 13.6, and 2.7 g·kg−1, respectively, after 24 h interaction at 45°C. The Langmuir and Freundlich isotherms have shown good fits (R2≥.9) in comparison with other isotherms, revealing the sorption characteristics of the soil–contaminant system (SCS). The experimental data of the SCS followed pseudo-second-order kinetics; however, Soils S1 and S2 exhibited a pseudo-first-order reaction on sorption of uranium. The effect of temperatures from 27°C to 45°C on sorption has revealed higher uptake of contaminant metals onto soils, and sorption of SCS is established to be spontaneous and endothermic. Moreover, the results revealed the physisorption regime in the SCS, and the soils exhibit good binding with the contaminants.