Figure 2.

Effect of the solution’s pH on p-nitrophenol adsorption by biochar. (a) Adsorption amount of p-nitrophenol at different pH values. Notably, the adsorption reaction was conducted at a 100 mg/L concentration of p-nitrophenol, 0.1 g/0.02 L adsorbent dosage, and 35 °C temperature. The solution’s pH was adjusted to 3–11 by adding 0.1 mol/L NaOH or 0.1 mol/L HCl, and the pH value was basically kept constant during the adsorption process. Data comprise the average of duplicate experiments, and error bars indicate the standard error. (b) Species distribution of p-nitrophenol at different pH values.