Sorption of Ammonium Ions onto Natural and Modified Egyptian Kaolinites: Kinetic and Equilibrium Studies

Table 5

Langmuir, Freundlich, and D-R isotherm parameters for sorption of NH₄⁺ ions onto natural and modified kaolinites.

Isotherm parameters	K	AHK	HK	HAK
Langmuir isotherm
𝑞𝑚 (mg·g^−1)	10.87	45.45	38.46	43.48
𝐾𝐿 (L·g^−1)	0.7022	0.3107	0.2962	0.2949
𝑅𝐿	0.1246	0.2435	0.2524	0.2532
ΔG (kJ·mol^−1)	−24.7	−22.7	−22.5	−22.5
𝑅^2	0.9749	0.9750	0.9595	0.9622
Freundlich isotherm
𝐾𝐹 (mg/g)·(L/mg)^−1/𝑛	1.851	8.367	3.823	6.005
1/𝑛	0.5959	0.5982	0.5550	0.8171
𝑅^2	0.9367	0.9548	0.9499	0.9595
D-R isotherm
𝑞DR (mg·g^−1)	7.81	18.05	16.85	17.61
𝛽×10^−3 (mol^2·kJ^−2)	−2.266	−1.723	−1.064	−1.817
𝐸𝑎 (kJ·mol^−1)	1.183	1.357	1.221	1.321
𝑅^2	0.9353	0.8909	0.7178	0.7878