Effects And Mechanisms Of The Adsorption Of Ammonium Nitrogen From Water By Reed Biochar

Ammonium nitrogen is one of the main factors causing water eutrophication,removing ammonium nitrogen in water plays an important role in controlling eutrophication.Among the common ammonium nitrogen control methods,constructed wetlands have the advantages of stable effluent water quality,strong ability to remove nutrients such as nitrogen and phosphorus,and low infrastructure and operating costs.However,due to plant death and low microbial activity in low temperature environments in autumn and winter.The ammonium nitrogen removal effect is poor.Therefore,we need to find an effective way to make up for this defect and solve the problem of environmental safety.This paper proposes to use reeds harvested from wetlands in autumn and winter as raw materials to prepare biochar adsorbents for removal of ammonium nitrogen.It can not only solve the problem of reed waste disposal,but also achieve the problem of improving the efficiency of ammonium nitrogen removal in constructed wetlands in winter.In this paper,appearing in wetlands reed straw as the raw materials,preparation of reed biochar at different temperatures,and through the preparation of sulfonated modified sulfonated reed biochar,reed was studied and its modified biochar adsorption performance of ammonium nitrogen in water,influence factors,and its effect on ammonium nitrogen release in the sediment by SEM,BET,elemental analysis,FTIR,XPS such as characterization of the physical and chemical properties of biochar,adsorption mechanism was discussed.The main conclusions are as follows:（1）Reed biochar can effectively adsorb ammonium nitrogen in water.The results show that the addition of reed biochar can effectively adsorb ammonium nitrogen in water,and the adsorption performance of sulfonated reed biochar is better than that of reed biochar.The adsorption kinetics process can be fitted with a quasi-second-order kinetic model,and the adsorption isotherm is more consistent with the Langmuir isothermal adsorption model.The maximum adsorption capacity of sulfonated reed biochar for ammonium nitrogen in water is 5.19 mg/g,which is2.7 times that of reed biochar（1.92 mg/g）.Biochar can effectively fix ammonium nitrogen in sediment,and the effect of sulfonated reed biochar is better than that of reed biochar.（2）The properties of biochar and environmental conditions can significantly affect the adsorption efficiency of ammonium nitrogen.The results showed that the adsorption performance of reed biochar prepared at 300°C to ammonium nitrogen was better than that prepared at 500°C and 700°C;the particle size and environmental temperature of biochar did not significantly affect the adsorption effect,indicating that the biochar prepared in this study can be used for adsorption and removal of ammonium nitrogen in low temperature environment.However,the increase in the concentration of coexisting ions in the solution will reduce the adsorption capacity of biochar to ammonium nitrogen.（3）Initially explored the mechanism of reed biochar adsorption ammonium nitrogen.Combined with elemental analysis,FTIR,XPS and other characterization methods,it was found that the rich functional groups on the surface of the biochar material are the main sites for ammonium nitrogen adsorption,and the sulfonic acid groups loaded on the surface of the sulfonated reed biochar can combine with NH₄⁺improve the effect of ammonium nitrogen adsorption and removal.