Abstract
Biochar has been extensively studied as a soil amendment to reduce nutrients losses. However, the comparative effectiveness of biochar adsorption capacity for ammonium (NH4-N), nitrate (NO3-N), and phosphate (PO4-P) remains unknown. In the present study, the effects of feedstock (banana stem and coconut shell) and temperature (300, 500, and 700°C) on biochar adsorption ability for NH
4-N, NO
3-N, and PO
4-P were investigated and fitted by three adsorption models, viz Freundlich, Langmuir, and linear. Freundlich (R
2 = 0.95–0.99) and Langmuir (R
2 = 0.91–0.95) models were found suitable for adsorption of NH
4-N. The maximum adsorption capacity (Q
m) for coconut shell biochar increased with pyrolysis temperature (Q
m
= 12.8–15.5 mg g-1) and decreased for banana stem biochar (Q
m = 12.9–9.7 mg g-1). In the case of NO
3-N adsorption, Freundlich (R
2 = 0.82–0.99) and linear model (R
2 = 1.00) were found suitable while Langmuir model showed much less contribution, similarly adsorption of PO
4-P, was not supported by these three models. The minimum concentrations required for adsorption of phosphate were recorded as 36, 8, and 3 mg L
-1 using pyrolyzed biochar at the temperatures of 300, 500, and 700°C, respectively. These results indicate that the feedstock and pyrolysis temperature, as well as aquatic nutrient concentration, were important factors for the adsorption of inorganic nitrogen and phosphorus.
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