2.4. Kinetics experiments
Kinetic studies were carried out in order to determine the contact
time required to reach the equilibrium. 200 mL samples of 100 mg/L
metal ion solutions were adjusted to desired pH and then mixed with
0.1 g of each sorbent . Sorption processes were carried out in flasks
placed in a thermostatic water-bath shaker at fixed temperature, until
the equilibrium was reached. 3 mL samples were collected at specified
intervals for the analysis of metal concentrations.
2.5. Modeling
2.5.1. Isotherm models
Sorption equilibrium can be described by a number of models
available in the literature. In this work, four different models: two
two-parameter models and two three-parameter models, fall within a
wide range.
The Langmuir model assumes a monolayer adsorption of solutes
onto a surface comprised of a finite number of identical sites with
homogeneous adsorption energy. This model [30] is expressed as
follows: