ADSORPTION OF NITRATE BY BIOCHAR PREPARED FROM THE FRUIT DRAGON BRANCHES (Hylocereus sp.)

Abstract

The present study evaluated the nitrate removal efficiency in aqueous solution using biochar (BC) produced from the fruit dragon branches. The BC produced through pyrolysis at 450°C for 120 minutes, exhibited a rough, porous and heterogeneous surface morphology, making it suitable for adsorption applications. Optimal adsorption conditions were achieved at a pH of 2, 3.0 g of biochar having particles size of 0.054 - 0.105 mm, a contact time of 60 minutes, 50 mL initial nitrate concentration of 80.0 mg/L and room temperature, yielding an adsorption efficiency and adsorption capacity of 93.4% and 1.25 mg/g, respectively. The strong influence of solution pH on adsorption efficiency was demonstrated by a significant decrease in efficiency as the pH solution increased, highlighting the role of electrostatic attraction between the positively charged biochar surface (below the point of zero charge (PZC) of 7.6) and the nitrate anions. The adsorption process followed the Langmuir isotherm model having q_max of 1.437 mg/g and the pseudo-second-order kinetic, indicating that chemisorption was the dominant mechanism. This research contributes to elucidating the potential for using agricultural by-products in nitrate treatment and proposes using the post-adsorption biochar as a slow-release fertilizer, aligning with the circular agriculture model.