One-, Two-, and Three-Parameter Isotherms, Kinetics, and Thermodynamic Evaluation of Co(II) Removal from Aqueous Solution Using Dead Neem Leaves

Table 6

One-, two-, and three-isotherm parameters for the adsorption of Co(II) on DNL.

Isotherm/parameters	Tested concentrations
	10 mg/L	100 mg/L	500 mg/L
One-parameter isotherm
Henry’s isotherms
KHE	1.000	1.000	1.000
R^2	1.000	1.000	1.000
Two-parameter isotherms
Freundlich
KF (mg/g)(L/mg)^1/n	9.201	118.203	523.900
n	−5.112	−8.446	−35.088
R^2	0.9993	0.9992	0.9995
Jovanovic
qmax (mg/g)	10.171	100.655	500.196
KJ	0.120	0.011	0.002
R^2	1.000	1.000	1.000
Langmuir-1
qm (mg/g)	6.988	80.000	476.190
b (L/mg)	3.756	0.893	2.625
RL	0.026	0.011	0.001
R^2	0.9971	0.9967	0.9982
Langmuir-2
qm (mg/g)	6.983	80.000	476.190
b (L/mg)	3.739	0.893	2.625
RL	0.026	0.011	0.001
R^2	0.9999	1.000	1.000
Langmuir-3
qm (mg/g)	6.990	79.95	472.700
b (L/mg)	3.757	0.896	2.618
RL	0.026	0.011	0.001
R^2	0.9979	0.9974	0.9983
Langmuir-4
qm (mg/g)	6.987	79.895	472.647
b (L/mg)	3.749	0.894	2.614
RL	0.026	0.011	0.001
R^2	0.9979	0.9974	0.9983
Langmuir-5
qm (mg/g)	6.986	79.927	472.571
b (L/mg)	3.746	0.893	2.614
RL	0.026	0.011	0.001
R^2	0.9971	0.9967	0.9982
Temkin
AT (L/mg)	0.004	2.026E−05	3.978E−17
bT (kJ/mol)	−1.515	−0.234	−0.179
R^2	0.9995	0.9993	0.9996
Two-parameter isotherms
Elovich
qm (mg/g)	1.368	9.470	13.459
KE (L/mg)	0.008	7.072E−05	5.375E−16
R^2	0.9997	0.9995	0.9996
Dubinin–Radushkevich
Xm (mg/g)	7.388	84.041	479.048
K (mol^2 kJ^−2)	−0.0845	−1.1855	−0.4736
E (kJ/mol)	2.433	0.649	1.027
R^2	0.9965	0.9941	0.9964
Fowler–Guggenheim
KFG (L/mg)	6.155E − 05	2.108E − 08	4.759E − 31
W (kJ/mol)	−16.182	−24.254	−90.163
R^2	0.9996	0.9995	0.9996
Kiselev
k1 (L/mg)	25.186	11.652	172.78
kn	1.331	1.191	1.044
R^2	0.9942	0.9933	0.9961
Hill–de Boer
K1 (L/mg)	2.922E − 14	2.015E − 39	0
K2 (kJ/mol)	−111.102	−269.609	−3328.866
R^2	0.9988	0.9978	0.998
Langmuir–Freundlich
KG (mg/L)	0.268	1.139	0.740
Nb	0.995	1.011	1.367
R^2	0.9975	0.9966	0.9972
Harkin–Jura
A	−178.571	−33333.333	−5000000
B	2.07E + 00	2.00E + 00	2.00E + 01
R^2	0.9988	0.9988	0.9995
Halsey
KH	84635.961	3.201E + 17	2.584E + 95
nH	5.11247444	8.44594595	35.0877193
R^2	0.9993	0.9992	0.9995
Flory–Huggins
n	0.216	0.1184	0.0289
KFH (L/mg)	0.057	0.007	0.002
R^2	0.9994	0.9992	0.9995
Three-parameter isotherm
Redlich–Peterson
KR (Lg^−1)	18	33	131
aR (L/mg)	1.104	0.083	0.068
bR	1.674	1.505	1.407
R^2	1.000	1.000	1.000