Effects of Two Kinds of Modified Biochar Adsorbing Nitrate-N in Water

Two kinds of FeCl₃ modified biochar, prepared separately out of Typha angustifolia and Phragmites communis, two aquatic plants, were used as adsorbent and potassium nitrate solution was as adsorbate in this study to simulate removal of nitrate-N by biochar, and further to analyze adsorption kinetics and adsorption isotherm characteristics of the two modified biochars and their originals, and explore effects of biochar application rate, adsorption duration, and initial concentration and pH of the adsorbate on nitrate-N adsorption by the two biochars, with the aid of infrared spectroscopy (IR), scanning electron microscopy (SEM) and elemental assay. Results showed that nitrate-N adsorption of the two modified biochars fitted the pseudo-secondary adsorption kinetics. The maximum adsorption capacity q_m of the FeCl₃ modified Typha angustifolia biochar (XP-Fe) and FeCl₃ modified Phragmites communis biochar (LW-Fe) was 15.55 and 10.63 mg·g^-1, respectively. Reduced pH of the adsorbate facilitated nitrate-N adsorption by XP-Fe and LW-Fe. XP-Fe was higher than LW-Fe in nitrate-N adsorption capacity.