载氧化镁水生植物生物炭的特性表征及对水中磷的吸附

Characterization of MgO-loaded aquatic plants biochar and its adsorption capacity of phosphorus in aqueous solution

为去除富营养化水体中的磷并实现水生植物的资源化利用,以水生植物芦苇和互花米草为原材料,通过MgCl_2改性制备了不同Mg^(2+)和植物配比的共12种生物炭,考察对水体中磷的吸附能力及镁改性前后生物炭特性的差异.结果表明,当Mg^(2+)与芦苇、Mg^(2+)与互花米草的质量比为0.48、0.36时,制得的两种生物炭对20 mg·L^(-1)磷的吸附能力最强,分别为8.52 mg·g^(-1)和9.21 mg·g^(-1),是未改性时的79倍和66倍;对溶液中20mg·L^(-1)磷的去除率分别达到85.2%和92.1%.改性后芦苇和互花米草生物炭C、H、N含量减少,Mg含量分别增加到22.77%和23.46%.芦苇生物炭改性后比表面积减小了118.71 m^2·g^(-1),互花米草生物炭增加了22.59 m2·g^(-1);二者孔容和平均孔径均有所增加.改性前后生物炭的表面官能团种类相同.XRD测试指出MgO为改性生物炭的复合纳米颗粒中最主要的晶相;SEM展现了布满MgO的改性生物炭表面及孔道.机理分析表明,MgO是生物炭吸附磷的关键.

In order to remove phosphorus in eutrophic water and realize the resource utilization of aquatic plants,12 kinds of biochars were prepared by using Phragmites communis Trin,Spartina alterniflora Lois and Mg^（2＋） in different ratios.MgCl2 played a role as modifier.Thus,phosphorus adsorption capacity and different characteristics of biochars before and after modification were discovered.The results showed that when the ratios of Mg^（2＋） to Phragmites communis Trin and Mg^（2＋） to Spartina alterniflora Lois were 0.48 and 0.36,biochars had the highest adsorption capacity as 8.52 mg·g-1 and 9.21 mg·g-1 respectively,which were 79-fold and 66-fold higher than unmodified biochars and the phosphorus removal rate reached 85.2% and 92.1% respectively,for 20 mg·L-1phosphorus solution.Compared to unmodified biochars,C,H and N content of modified biochars decreased while Mg increased to 22.77% and 23.46%.Specific surface area of Phragmites communis Trin biochar decreased by 118.71 m^2·g-1,but that of Spartina alterniflora Lois biochar increased by 22.59 m^2·g-1.Pore volume and average pore width of these two biochars both increased.Surface functional groups of modified biochars were the same as unmodified ones.XRD patterns demonstrate that MgO was the most important phase in the composite nanoparticles of modified biochars;SEM images revealed surface and pores of modified biochars were filled with MgO.MgO was key component for phosphorus adsorption in biochar.