Study of Ammonium and Nitrate Adsorption Kinetics and Isotherm by Common reed (Phragmites australis) Biochar from Aqueous Solution

Nitrate and ammonium are the major contaminants of aquatic ecosystem causing eutrophication in water resources. Application of natural, inexpensive and ecofriendly adsorbents can be a useful approach for ammonium and nitrate removal from aqueous solutions. The aim of this study was to investigate the ability of common reed biochar to absorb nitrate and ammonium from aqueous solution. For this purpose, the common reed biochar was prepared at 500°C and its characteristics were measured. The effect of initial concentration, contact time, pH and biochar dosage on nitrate and ammonium adsorption was studied using batch experiment. Adsorption of nitrate and ammonium by biochar reached to equilibrium after 480 and 240 minutes, respectively. The optimal pH for removal of nitrate and ammonium was 3 and 9, respectively. The efficiency of nitrate and ammonium removal increased with increasing contact time and dose of biochar. The pseudo second order kinetic model provides a good description for the adsorption process of ammonium (r2=0.994)  and nitrate (r2 =0.970). Langmuir and Freundlich isotherms showed the best fit for ammonium and nitrate experimental data, respectively. Generally, the common reed biochar showed a high capacity for adsorption of nitrate (73.52 mg g-1) and ammonium (42.55 mg g-1). Therefore, the exhausted adsorbents containing ammonium and nitrate has a good potential as a soil conditioner that can supply part of plant''s need to nitrogen.