Abstract
Sorption of metallic cadmium from the pH adjusted aqueous solutions at varying initial concentrations onto an alluvial (clay) soil through batch sorption experiments was studied. The pH of the initial concentrations ranging between 50 mg/L to 250 mg/L was varied from 3.0 to 8.0. The sorption experiments were carried out for different durations and up to 16 hours. The cadmium continued to sorb till the last experimental pH=8. The experimental sorption data fitted very well with both Langmuir and Freundlich isotherm models and Freundlich model gave higher correlation coefficients. The pseudo-second order kinetics model was most agreeable with the experimental sorption data, whereas the pseudo-first order model was found to be insufficient.
Highlights
Heavy metals are defined as metals and metalloids generally considered being of sufficient distribution and abundance as to be in some way environmentally or biologically significant as a toxic substance[1]
Langmuir and Freundlich constants at different sorbate-pH have been given in the Table 2, whereas in Table 3 kinetic parameters for different initial sorbate concentrations have been presented
All the facts suggested that the experimental sorption data approximated the second-order kinetic model very well
Summary
Heavy metals are defined as metals and metalloids generally considered being of sufficient distribution and abundance as to be in some way environmentally or biologically significant as a toxic substance[1]. A number of investigations have shown Cd solubility to be dependent on the cation-exchange capacity (CEC), clay content, organic matter, and other metal ions present[7,8,9,10]. Langmuir and Freundlich constants at different sorbate-pH have been given, whereas in Table 3 kinetic parameters for different initial sorbate concentrations have been presented.
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