Ammonia nitrogen adsorption characteristics in aqueous solution by modified vermiculite and woody peat

【Objective】 This experiments were performed to explore the ammonia nitrogen（NH₄⁺-N） aqueous adsorption characteristics and mechanism by modified vermiculite and woody peat,identify suitable materials for the removal of ammonia nitrogen from aqueous adsorption,which could provide scientific basis for the efficient and rapid treatment of ammonia nitrogen contaminated wastewater. 【Method】 Natural vermiculite,5 and 7 mol/L sulfuric acid-modified vermiculite and woody peat were selected as research materials. The characteristics and mechanisms of ammonia nitrogen aqueous adsorption were analyzed according to results from adsorption experiment by common soil conditioners,scanning electron microscope and the Fourier infrared spectrogram.【Result】The adsorption process of NH₄⁺-N in aqueous solution by different vermiculite materials was characterized by fast adsorption and slow equilibrium. Microcellular structure of natural vermiculite was partially destroyed during the acid modification process,and the specific surface area and average pore diameter were increased. The specific surface area and total pore volume for 7 mol/L sulfuric acid-modified vermiculite were much lower than those under 5 mol/L sulfuric acid-modified vermiculite. Compared with natural vermiculite,adsorption rate constants（k₁） from quasi-primary kinetic model for 5 and 7 mol/L sulfuric acid-modified vermiculite were increased by 2.09 and 1.45 times,the equilibrium adsorption amounts（q_e） were increased by 3.39 and 1.86 times,and liquid-film diffusion rate constants（k_a） were increased by 1.27 and 1.00 times respectively. The equilibrium time of adsorption of NH₄⁺-N by woody peat was longer,k₁ was lower than that of 2 acid-modified vermiculites,but qe was second only to 5mol/L sulfuric acid-modified vermiculite. The adsorption processes of 4 materials were primarily monolayer adsorption,the fitting efficiency of Langmuir model was better than Freundlich model in isothermal adsorption process. The physical adsorption process for vermiculite materials was mainly relied on the surface properties and pore structure of the solid material,k1 and the maximum adsorption capacity（q_m） both had significant positive correlation with the specific surface area（P＜0.05）,whereas woody peat relied on chemical reactions between active functional groups and NH₄⁺-N.【Conclusion】 Based on the comparison of multiple adsorption indicators and the availability of material sources,sulfuric acid-modified vermiculite and woody peat are recommended as the preferred adsorption attachments for ammonia nitrogen reduction in wastewater.