水生植物制生物炭对硝态氮的吸附规律研究

Studies on adsorption of nitrate from modified hydrophyte biochars

为在高纬度地区秋季温度条件下研究一种高效以及低值的技术去移除人工湿地中的硝酸盐氮,在秋季人工湿地中收集水生植物枯落物芦苇以及香蒲制备生物炭,并利用盐酸进行改性.通过序批实验,研究了改性水生植物生物炭对硝酸盐氮的吸附性能及影响因素,探讨了其吸附机理.结果表明,经盐酸改性的芦苇生物炭MRB与香蒲生物炭MCB表面均带正电荷,Zeta电位分别为+5.46mV与+2.31mV.MRB与MCB对硝酸盐氮吸附行为更符合准二级动力学方程(R^2>0.99),等温吸附曲线更好拟合Freundlich方程(R^2>0.98).MRB及MCB对硝酸根的最大吸附量Q_m分别为14.6661mg/g与5.5559mg/g.批量吸附实验也表明,溶液初始pH和共存阴离子会影响改性水生植物生物炭吸附硝酸盐.改性水生植物生物炭可以有效地去除来自于在秋季高纬度地区人工湿地污水中的硝酸盐.

To develop an efficient and economic technology to remove nitrate from constructed wetland in high-latitudeareas under the conditions of autumn temperature,modified hydrophyte biochars were prepared with aquatic plant litterscollected from constructed wetlands.Laboratory experiments were conducted to investigate the removal of nitrate fromaqueous solution and wastewater by modified hydrophyte biochars.The experimental results showed that the modifiedbiochars(MRB and MCB)carried positive charge and that Zeta potentials were respectively+5.46mV and+2.31mV.Thesecond order model fit the nitrate sorption kinetics of modified hydrophyte biochars with a high coefficient ofdetermination(R2>0.99).Freundlich isotherms performed well to fit the nitrate sorption data(R2>0.98)of modifiedhydrophyte biochars when compared to Langmuir isotherms.The maximum adsorption capacity of MRB and MCB tonitrate was14.6661mg/g and5.5559mg/g,respectively.Batch adsorption experiments also showed that both initialsolution pH and coexisting anions could affect the adsorption of nitrate onto modified hydrophyte biochars.Modifiedhydrophyte biochars could efficiently remove nitrate from wastewater in constructed wetland.