The effect of pH and ionic strength on the adsorption of glyphosate onto ferrihydrite

Table 2 Parameters of non-linear Langmuir, Freundlich and Langmuir–Freundlich for samples of glyphosate adsorbed onto ferrihydrite

[NaCl] mol L⁻¹	Model	K	1/n	b	R²
0.10	nl-Lang	0.023	–	54.88	0.903
	nl-Freu	11.25	0.245	–	0.881
	nl-Lang-Freu	0.015	0.657	64.83	0.928
0.01	nl-Lang	0.049	–	32.83	0.857
	nl-Freu	11.75	0.160	–	0.780
	nl-Lang-Freu	0.046	0.785	34.40	0.864

Each result was mean of four experiments. The solutions were stirred for 24 h at room temperature, at pH 5.0 with 60 mg of ferrihydrite. nl-Lang: non-linear Langmuir; nl-Freu: non-linear Freundlich; nl-Lang-Freu: non-linear Langmuir–Freundlich single site. K (Langmuir) (L mg⁻¹) and K (Freundlich) (mg g⁻¹) (L g⁻¹): adsorbate–adsorbent affinities; b: maximum adsorption capacity (mg g⁻¹); 1/n: empiric Freundlich constant

ISSN: 1467-4866