Novel Silica-Based Hybrid Adsorbents: Lead(II) Adsorption Isotherms

Table 1

The Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Harkins-Jura, and Halsey isotherm parameters for lead(II) adsorption.

Parameter	Values
	Sample A	Sample B	Sample C	Sample D
Langmuir isotherm model
𝑄𝑚 (mmol/g)	0.898	5.335	4.106	0.935
b	9.358	1.175	1.379	6.303
𝑅^2	0.941	0.722	0.669	0.854
Freundlich isotherm model
𝑘𝐹	3.061	5.380	4.754	2.875
n	1.240	1.030	1.034	1.158
𝑅^2	0.983	0.998	0.998	0.984
Dubinin-Radushkevich (D-R) isotherm model
𝑄DR (mmol g^−1)	0.846	1.124	1.007	0.733
𝐾DR (mol^2/kJ^2)	0.0168	0.020	0.020	0.0181
E (kJ/mol)	5.455	4.990	4.989	5.252
𝑅^2	0.997	0.998	0.998	0.997
Temkin isotherm model
𝑏𝑇 (kJ/mol)	18.154	14.125	15.768	21.385
𝐵𝑇	0.143	0.184	0.165	0.121
𝐾𝑇	175.878	136.724	136.521	158.936
𝑅^2	0.998	0.946	0.953	0.996
Harkins-Jura isotherm model
𝐴HJ	0.00402	0.00280	0.00230	0.00216
𝐵HJ	−1.131	−1.149	−1.144	−1.130
𝑅^2	0.920	0.925	0.924	0.920
Halsey isotherm model
𝐾𝐻	4.005	5.659	5.013	3.399
𝑛𝐻	1.240	1.030	1.034	1.158
𝑅^2	0.983	0.998	0.998	0.984