不同原料生物炭对水体硝态氮的吸附性能研究

Adsorption of Nitrate Nitrogen by Different Raw Materials of Biochar

探讨不同原料生物炭对水体硝态氮（NO3--N）吸附量的影响及吸附机制，为生物炭的科学应用提供基本理论依据。以花生壳、玉米秸秆、杨木屑和竹屑4种不同物质为原料，在500℃无氧条件下热解制备生物炭，通过吸附平衡试验，结合吸附前后的电镜扫描图（SEM）、傅立叶红外光谱图（FTIR）以及X-射线光电子能谱（XPS）等技术研究不同原料生物炭对NO3--N的吸附特性。结果表明，生物炭吸附NO3--N受pH的影响，随着pH值增大，吸附量显著降低。在溶液pH=2.00条件下，随溶液NO3--N质量浓度的升高，4种生物炭对NO3--N的吸附量显著增加，且在初始质量浓度为800mg·L-1的体系中达到平衡，花生壳生物炭（PBC）的最大吸附量为30mg·g-1，玉米秸秆生物炭（MBC）为44mg·g-1，杨木屑生物炭（ABC）为18mg·g-1，竹屑生物炭（BBC）为22mg·g-1，吸附能力大小为MBC>PBC>BBC>ABC。PBC、MBC和BBC3种生物炭的吸附等温线符合Langmuir模型，ABC符合Freundlich方程，吸附均可在60min内达到平衡；伪一级动力学方程可以较好地描述生物炭对NO3--N的动力学吸附过程。对比吸附前后的FTIR和XPS图谱发现，生物炭表面分布的-OH、-C=O、-C-O-、-O-等官能团参与了其对NO3--N的吸附，且与之相连的C原子结合能发生改变。4种生物炭吸附能力差异显著，其吸附机制均与表面官能团和金属化合物的作用有关，尤其以含氧官能团作用吸附NO3--N，且吸附过程由快速反应所控制。

This study is to reveal the differences among four kinds of biochar made of different raw materials on quantity and mechanism of absorption to NO3--N.It could provide basic theoretical basis for the scientific application of biochar.Peanut shell,maize straw,aspen and bamboo chips were applied to prepare biochar,under the condition of pyrolysis at 500℃.Then,different raw materials of biochars were used to study the adsorption properties of NO3--N via batch equilibrium adsorption test,SEM,FTIR and XPS.The adsorption of NO3--N by biochar was affected by pH,and the adsorption capacity decreased significantly with the increase of pH values.Under the condition of pH=2.00,the adsorption capacity of four kinds of biochar increased with the increasing NO3--N concentration,and reached equilibrium in the initial concentration of 800 mg·L-1.The maximum adsorption capacity of the peanut shell biochar(PBC)was 30 mg·g-1;maize straw biochar(MBC)was 44 mg·g-1;aspen chips biochar(ABC)was 18 mg·g-1;and bamboo chips biochar(BBC)was 22 mg·g-1,so that the adsorption capacity was PBC>MBC>BBC>ABC.Langmuir equation could be better fitted to describe NO3--N isothermal adsorption of PBC,MBC,BBC,and Freundlich equation could be better fitted to describe NO3--N isothermal adsorption of ABC.The adsorption could reach the equilibrium in 60 min.The pseudo-first-order kinetics equation could be more effective to describe NO3--N kinetic adsorption.The FTIR and XPS results of the four types of biochar before and after batch equilibrium adsorption test also demonstrated that the functional groups such as-OH,-C=O,-C-O-,-O-participation in the adsorption of NO3--N and the C atom binding energy changes happened.It could be seen that the adsorption capacities of the four types of biochar were significantly different,biochar could adsorb NO3--N through the action of surface functional groups,especially oxygen-containing functional groups,the adsorption was controlled by fast reaction.