Application of Sustainable and Low-Cost Sludge-Based Adsorbents …
75
q e = K F C
1/n
e
(5.6)
The logarithmic form of the equation is represented in Eq. 5.7
log(q e ) = log K F +
1
n
log(C e )
(5.7)
where K F and n are the Freundlich constants of the system. K F and n are the indicators
of the adsorption capacity and adsorption intensity, respectively. The slope and the
intercept of the linear Freundlich equation are equal to 1/n and ln K F , respectively. It
has been shown that n values between 1 and 10 represent good adsorption potential
of the adsorbent. The values of the Freundlich constants at different temperatures are
shown in Tables 21 and 22.
The experimental data showed correlation coefficients (R
2 ) close to unity. But
there was no linear correlation between the Freundlich constants (K F and n) and
the adsorption capacities shown in Tables 21 and 22. Hence, the adsorption of the
solute concentration was not evident. Though the n values were between 0 and 1,
the adsorption process showed the complex nature of the adsorption of reactive dyes
onto the activated carbon adsorbents. The experimental data were well suited to the
Langmuir isotherm than the Freundlich model. Therefore, the adsorptions of the
reactive dyes under consideration are linear in Langmuir isotherm plot.
Table 21 Freundlich isotherm constants and correlation coefficients for adsorption of RR31 on
commercial activated carbon and tannery sludge-developed activated carbons
Temperature (°C) Adsorbents
CAC RR31
SC600 RR31
SC300 RR31
N
K F
R 2
N
K F
R 2
n
K F
R 2
20
1.965 4.549 0.999 2.801
6.671 0.968 0.869
1.119 0.933
30
1.374 4.414 0.996 7.348 15.844 0.894 3.263 12.995 0.989
40
1.960 6.915 0.908 2.899 12.290 0.981 4.529 19.696 0.964
50
2.375 9.138 0.950 4.268 20.271 0.871 5.631 24.047 0.916
Table 22 Freundlich isotherm constants and correlation coefficients for adsorption of RR2 on
commercial activated carbon and tannery sludge-developed activated carbons
Temperature (°C) Adsorbents
CAC RR2
SC600 RR2
SC300 RR2
N
K F
R 2
N
K F
R 2
n
K F
R 2
20
6.485 3.294 26.940 2.649 35.616 0.997 1.520
5.000 0.962
30
2.843 2.773 15.999 2.693 23.755 0.978 2.573
8.496 0.969
40
2.818 2.502 12.203 4.488 27.511 0.962 2.705 11.516 0.987
50
3.062 2.247
9.457 1.816 28.983 1.000 1.835 86.125 0.975
75
q e = K F C
1/n
e
(5.6)
The logarithmic form of the equation is represented in Eq. 5.7
log(q e ) = log K F +
1
n
log(C e )
(5.7)
where K F and n are the Freundlich constants of the system. K F and n are the indicators
of the adsorption capacity and adsorption intensity, respectively. The slope and the
intercept of the linear Freundlich equation are equal to 1/n and ln K F , respectively. It
has been shown that n values between 1 and 10 represent good adsorption potential
of the adsorbent. The values of the Freundlich constants at different temperatures are
shown in Tables 21 and 22.
The experimental data showed correlation coefficients (R
2 ) close to unity. But
there was no linear correlation between the Freundlich constants (K F and n) and
the adsorption capacities shown in Tables 21 and 22. Hence, the adsorption of the
solute concentration was not evident. Though the n values were between 0 and 1,
the adsorption process showed the complex nature of the adsorption of reactive dyes
onto the activated carbon adsorbents. The experimental data were well suited to the
Langmuir isotherm than the Freundlich model. Therefore, the adsorptions of the
reactive dyes under consideration are linear in Langmuir isotherm plot.
Table 21 Freundlich isotherm constants and correlation coefficients for adsorption of RR31 on
commercial activated carbon and tannery sludge-developed activated carbons
Temperature (°C) Adsorbents
CAC RR31
SC600 RR31
SC300 RR31
N
K F
R 2
N
K F
R 2
n
K F
R 2
20
1.965 4.549 0.999 2.801
6.671 0.968 0.869
1.119 0.933
30
1.374 4.414 0.996 7.348 15.844 0.894 3.263 12.995 0.989
40
1.960 6.915 0.908 2.899 12.290 0.981 4.529 19.696 0.964
50
2.375 9.138 0.950 4.268 20.271 0.871 5.631 24.047 0.916
Table 22 Freundlich isotherm constants and correlation coefficients for adsorption of RR2 on
commercial activated carbon and tannery sludge-developed activated carbons
Temperature (°C) Adsorbents
CAC RR2
SC600 RR2
SC300 RR2
N
K F
R 2
N
K F
R 2
n
K F
R 2
20
6.485 3.294 26.940 2.649 35.616 0.997 1.520
5.000 0.962
30
2.843 2.773 15.999 2.693 23.755 0.978 2.573
8.496 0.969
40
2.818 2.502 12.203 4.488 27.511 0.962 2.705 11.516 0.987
50
3.062 2.247
9.457 1.816 28.983 1.000 1.835 86.125 0.975