The adsorption isotherm
at 303 and 323 K goes well with the Freundlich isotherm model and isotherm at 313 K follows Langmuir model with maximum adsorption capacity of 17.4 mg/g.
8 shows that the adsorption isotherm
of MB on corallina elongata is the L-type (called Langmuir type), where the shape of the adsorption isotherm
means that there is no strong competition between the solvent and the adsorbate to occupy the adsorption sites .
Thus, adsorption isotherms
were obtained by plotting the amount of copper adsorbed (mmol [g.sup.-1] substrate) against the equilibrium concentration (mmol) and fitted to the linear form of the Langmuir equation [15-17].
The maximum adsorption capacity ([q.sub.m]) obtained for the MB dye in this work was 374.75 mg.[g.sup.-1] and is in accordance to the maximum values presented in the adsorption isotherms
(as show in Figure 4).
where R is the gas constant (8.314 J [K.sup.-1] [mol.sup.-1]), T is the absolute temperature (K), and K[degrees] is the adsorption isotherm
The results are also in good agreement with adsorption isotherm
shown in the above section.
Langmuir adsorption isotherm
is based on monolayer adsorption of metal ions on the surface of agrowastes, and energy of adsorption system is considered constant.
On analysis of the various adsorption isotherms
, the adsorption follows the Langamuir isotherm model, thereby confirming the homogeneous surface of the adsorbent and monolayer formation.
Langmuir and Freundlich adsorption isotherm
and their parameters are presented in Figure 11, Figure 12, and Table 3.
The adsorption isotherms
of the powder samples were determined through the indirect static method (Crapiste & Rotstein, 1982) in BOD (Biochemical Oxygen Demand) chamber regulated at temperatures of 20, 30 and 40 [degrees]C, with measurements of water activity ([a.sub.w]) in hygrometer (Aqualab 3TE, Decagon) in variation range of approximately 0.3-0.9.
relates the adsorbate--adsorbent interaction at equilibrium.
The adsorption amount at the equilibrium state (W) was calculated by (1) based on the adsorption isotherms
. On the basis of the Langmuir adsorption isotherm
formula, the equation of state for the one-component adsorption can be represented as follows: