Biochar is believed to be a good absorbent for various contaminants. In an isotherm experiment, a series of 20 mL polyethylene centrifuge tubes containing nutrient (NH 4 Cl) solutions (Volume: 12 mL,...

Biochar is believed to be a good absorbent for various contaminants. In an isotherm experiment, a series of 20 mL polyethylene centrifuge tubes containing nutrient (NH₄Cl) solutions (Volume: 12 mL, pH adjusted to 7.0 ± 0.2) with NH₄
⁺-N concentrations of 60, 120, 180, 240, or 480 mg/L and 200 mg of switchgrass biochar samples (sealed with Telflon-line screw caps) were agitated on a wrist action shaker for 24 h (pre-examined to be sufficient) to reach equilibrium. The concentrations of NH₄
⁺-N at equilibrium are summarized in the table below.

Please use the
Freundlich isotherm model
to estimate the adsorption constant values of switchgrass biochar.