“…The adsorption experiments were performed through the batchwise method by suspending a series of 20 mg samples of the solid, in 20.0 cm 3 aqueous solutions of cations at concentrations varying from 1.25 to 2.5 Â 10 À2 mmol dm À3 , under orbital stirring for 24 h at 298 ± 1 K. From profiles of the obtained adsorption isotherms represented by the number of moles adsorbed (N f ) [18][19][20], versus the number of moles at equilibrium per volume of solution (C S ), for a series of isotherms, the data reveal that the adsorption process conforms to the Sips model. Sips combined the Langmuir and Freundlich equations (Eq.…”