纳米零价铁改性生物炭对水中氨氮的吸附特性及机制

Adsorption Characteristics and Mechanism of Ammonia Nitrogen in Water by Nano Zero-valent Iron-modified Biochar

传统生物炭材料对水中氨氮(NH_(4)^(+)-N)的吸附效果不佳.以生物炭为载体负载纳米零价铁制得生物炭基纳米零价铁复合吸附剂nZVI@BC,通过吸附实验,考察nZVI@BC对NH_(4)^(+)-N的吸附特性,并采用SEM-EDS、BET、XRD和FTIR分析nZVI@BC的组成和结构特性,探讨nZVI@BC吸附NH_(4)^(+)-N的主要机制.结果表明,在298K下铁/生物炭质量比为1∶30时制备的复合吸附剂(nZVI@BC1/30)对NH_(4)^(+)-N的吸附性能最佳,比负载前生物炭的吸附量提高了45.96%,饱和吸附量可达16.60 mg·g^(-1).伪二级动力学模型和Langmuir模型更符合nZVI@BC1/30对NH_(4)^(+)-N的吸附过程.共存阳离子与NH_(4)^(+)-N之间存在竞争吸附,其对nZVI@BC1/30吸附NH_(4)^(+)-N的影响顺序为:Ca^(2+)>Mg^(2+)>K^(+)>Na^(+).nZVI@BC1/30吸附NH_(4)^(+)-N的主要机制为氢键结合和离子交换.综上所述,采用纳米零价铁对生物炭进行改性能够提高NH_(4)^(+)-N的吸附效果,提升生物炭在水体脱氮领域的应用潜力.

The adsorption performances of ammonia nitrogen(NH_(4)^(+)-N)in water by unmodified biochar are ineffective.In this study,nano zero-valent iron-modified biochar(nZVI@BC)was prepared to remove NH_(4)^(+)-N from water.The NH_(4)^(+)-N adsorption characteristics of nZVI@BC were investigated through adsorption batch experiments.The composition and structure characteristics of nZVI@BC were analyzed using scanning electron microscopy,energy spectrum analysis,BET-N_(2) surface area(SSA),X-ray diffraction,and FTIR spectra to explore the main adsorption mechanism of NH_(4)^(+)-N by nZVI@BC.The results showed that the composite synthesized at the iron to biochar mass ratio of 1:30(nZVI@BC1/30)performed well in NH_(4)^(+)-N adsorption at 298 K.The maximum adsorption amount of nZVI@BC1/30 at 298 K was remarkably increased by 45.96% and reached 16.60 mg·g^(-1).The pseudo-second-order model and Langmuir model fitted well with the adsorption process of NH_(4)^(+)-N by nZVI@BC1/30.There was competitive adsorption between coexisting cations and NH_(4)^(+)-N,and the sequence of coexisting cations to the adsorption of NH_(4)^(+)-N by nZVI@BC1/30 was Ca^(2+)>Mg^(2+)>K^(+)>Na^(+).The adsorption mechanism of NH_(4)^(+)-N by nZVI@BC1/30 could be mainly attributed to ion exchange and hydrogen bonding.In conclusion,nano zero-valent iron-modified biochar can improve the adsorption performance of NH_(4)^(+)-N and enhance the application potential of biochar in the field of nitrogen removal from water.