To remove the low concentration nitrate in water and eliminate eutrophication,the biochar was prepared from three kinds of macrophytes,including Thalia dealbata,Typha orientalis and Phragmites australis,and then were modified by ferric chloride.FTIR and SEM-EDS results of the biochar and equilibrium adsorption tests show that the Fe-O was formed on the surface of the modified biochar which greatly enhanced biochar's adsorption performance to the nitrate-nitrogen.The nitrate was absorbed rapidly in 4 hours and then reached equilibrium slowly in 24 hours.The equilibrium adsorption capacity of the modified Typha orientalis biochar was the highest,which reached up to 1.747 mg · g-1.The adsorption performance of low concentration nitrate onto three kinds of modified macrophytes biochar fitted well to pseudo-secondorder equation and Freundlich equation,indicating that inhomogeneous polymolecular layer chemisorption occurred on the surface of modified biochar.The initial pH of the solution in the range of 3.0-9.0 has little effect on the adsorption performance of nitrate,and the most appropriate pH is neutral.At the initial nitrate-nitrogen concentration of 2 mg · L-1,the most appropriate dosages of the three kinds of modified macrophytes biochar are 1.50,1.14,and 1.22 g · L-1 for iron modified biochar of Thalia dealbata,Typha orientalis and Phragmites australis,respectively.Therefore,the iron modified macrophytes biochar can not only effectively remove the nitrate-nitrogen in water,but also realize resource utilization of the macrophytes,which has a promising application prospect.%为有效去除富营养化水体中硝态氮,以再力花(Thalia dealbata)、香蒲(Typha orientalis)和芦苇(Phragmites australis)3种水生植物为原材料制备生物炭,并采用氯化铁改性后进行吸附试验,探索改性水生植物生物炭对水体中低浓度硝态氮的吸附效果.结果表明:铁改性水生植物生物炭表面负载了大量Fe3+形成Fe-O基团,大幅提升了其对硝态氮的吸附性能,其中铁改性香蒲生物炭平衡吸附量最大,达到1.747 mg·g-1.3种改性水生植物生物炭对低浓度硝态氮的吸附符合准二级动力学和Freundlich模型,吸附主要为生物炭表面非均一多分子层化学吸附.溶液初始pH值在3.0～9.0范围内对铁改性水生植物生物炭吸附硝态氮能力影响较小,吸附最适合pH为中性.因此,铁改性水生植物生物炭能有效去除水体中低浓度硝态氮,同时实现了水生植物资源化,具有良好的应用前景.
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