Adsorption characteristics of ammonium onto biochar from an aqueous solution

Ammonium contamination in water is a major concern worldwide. This study focuses on the removal of ammonium from aqueous solution by batch adsorption experiments using biochar derived from a combination of various wood chips (spruce, pine, and fir). Adsorption characteristics of ammonium onto biochar were evaluated as a function of biochar dosages, initial concentrations of ammonium, contact time and pH. Results demonstrated that ammonium removal increased with the increase of biochar dosage. The percentage of ammonium removal reached a value of 80% at a biochar dosage of 100 g/L. Ammonium removal decreased by 15% with the increase of initial ammonium concentration by 50 mg/L. The optimum pH for ammonium removal was considered in the range from 6 to 8. Ammonium removal reached its stable value within 3 days. The maximum adsorption capacity of ammonium was 0.96 mg/g for 80 mg/L of initial ammonium concentration. The adsorption isotherm followed both the Langmuir and Freundich models for ammonium adsorption onto biochar. Fourier Transform Infrared (FTIR) spectroscopy results indicated the presence of amine, amide and nitrile functional groups on the surface of biochar which could contribute to the adsorption of ammonium onto biochar. Thus, biochar derived from various wood chips showed the potential to remove ammonium from aqueous solution.