不同烧制温度下玉米秸秆生物炭的性质及对萘的吸附性能

Properties of Maize Stalk Biochar Produced Under Different Pyrolysis Temperatures and Its Sorption Capability to Naphthalene

以玉米秸秆为原料,在300、500和700℃这3个温度下烧制生物炭,使用元素分析仪测定其元素组成,扫描电镜观测其表面特性,并采用批量吸附实验研究了生物炭对萘的吸附特性.结果表明,随烧制温度升高,玉米秸秆生物炭的碳元素含量从66.79%上升到76.30%,氢和氧元素从4.92%和19.25%下降到3.18%和9.53%;H/C、O/C和(O+N)/C值降低,芳香性和疏水性增强,极性降低.扫描电镜结果显示玉米秸秆生物炭主要是片状颗粒,孔隙少,生物炭表面粗糙程度随温度升高增加.对萘的动力学吸附曲线符合Lagergren准二级模型,初始吸附速率与平衡吸附量随烧制温度上升而上升;等温吸附曲线可用Freundlich模型进行描述,生物炭的吸附能力随烧制温度升高而增强,非线性先下降后上升.玉米秸秆生物炭表面形态上具有显著特点,且不同烧制温度对其元素组成、表面特征和对萘的吸附行为有显著影响.

Biochar was made from maize stalk under three different temperatures of 300,500 and 700℃. The elemental composition of biochar was measured by elemental analyzer. Scanning electron microscope( SEM) was used to measure the surface morphology. Sorption of naphthalene to biochar was researched by batch sorption experiments. Results showed that, with the increase of temperature,C content increased from 66. 79% to 76. 30%,H and O contents decreased from 4. 92% and 19. 25% to 3. 18% and 9. 53%,respectively; H / C,O / C,( O + N) / C,aromaticity and hydrophobicity increased,and polarity decreased. SEM results showed that maize stalk biochar was platy particles,and its roughness of surface increased with increasing temperature. The sorption of naphthalene on biochar followed the Lagergren pseudo-second order dynamic sorption model. Initial sorption rate and equilibrium sorption capacity increased as preparation temperatures increased at the same initial concentration of naphthalene. The isotherm sorption behavior can be described by the Freundlich model,which indicated that,as pyrolysis temperature increased,the sorption capacity of biochar increased,and nonlinearity increased first and then decreased. Biochar derived from maize stalk had distinct features when compared with other feedstocks,and its elemental composition,surface features and sorption behaviors were significantly influenced by pyrolysis temperature.