Fig. 3 shows the adsorption results of Spirogyra and Cladophora
algae powder at 25 C for Pb(II) and Cu(II), respectively, as well as
the plots of 1/qe and 1/Ce, based on the Langmuir model (Eq. (2))
described previously and the Freundlich isotherms (Eq. (4)). The
plots of log qe versus log Ce, are shown in Fig. 3. The constants obtained
from Langmuir and Freundlich isotherms had very high correlation
coefficients (R2) (Table 2). Comparisons between
correlation coefficients, with the adsorption correlation values for
Spirogyra and Cladophora, fit the Langmuir model better than the
Freundlich model. These values indicated a strong positive
correlation.
For the fitting results of Langmuir isotherms (see Table 2), the
maximum Qmax and minimum b value of the Langmuir constants
were 90.91and 0.024, respectively, for Spirogyra Pb(II) adsorption.
In comparing the b value of the two biosorbents, each demonstrated
differing adsorption results for different metal ions. Qmax
represents the maximum biosorption capacity of the biosorbent,
while the b value indicates the affinity of a biosorbent towards
an adsorbate.
For the fitting results of the Freundlich model (see Table 2),
higher K values, and n values are 9.22 mgg1 and 2.44, respectively,
in the adsorption results for Spirogyra algae to Pb(II). A high K value
indicated a high adsorption volume. A high 1/n value (n > 1) indicated high adsorption strength. Table 2 shows a comparison of
correlation coefficients for various biosorbents in the adsorption of
Pb(II) and Cu(II) (6.29–9.67). The results indicated that Spirogyra is
a better biosorbent material than Cladophora.
In comparing the adsorption test results of Pb(II) and Cu(II) for
both types of adsorption materials, the adsorption of Pb(II) had a
lower b value, indicating that both types of biosorbents had a higher
affinity for Pb(II).