化学老化对Zn改性生物炭性质及吸附Pb^(2+)的影响

Effects of chemical aging on the properties of Zn-modified biochars and the adsorption properties of Pb^(2+)

本文采用60及90℃非生物化学老化方法,对ZnSO_(4)浸渍改性生物炭(PRZn)进行了为期6个月的老化试验.通过元素分析仪,比表面积分析仪,X射线光电子能谱法和傅里叶红外光谱等手段明确老化后生物炭性质的变化特点,并利用等温吸附实验比较老化对Zn改性生物炭Pb^(2+)吸附性能的差异.结果表明,化学老化过程会生成活性自由基,显著增加生物炭表面含氧官能团的数量,导致500℃制备的PRZn老化后比表面积显著提高(从24.67m^(2)/g提升到85.51m^(2)/g),改性引入的Zn氧化物从晶型结构转化为有机结合态,因此,PRZn经60℃老化后,其对Pb^(2+)的吸附量从31.18mg/g提高至47.70mg/g.但经90℃老化后,700℃制备的PRZn吸附量变化不大,这主要是老化过程中产生的活性氧化物质在90℃下发生自猝灭过程,且700℃制备的PRZn碳结构相对稳定,导致老化后含氧官能团的量没有显著升高而比表面积下降.本研究结果将为改性后老化生物炭在铅污染土壤中的长期利用提供具体理论依据.

In this paper,ZnSO4-impregnated biochar(PRZn)was subjected to high temperature(60℃ and 90℃)abiotic aging for six months.The characteristics of biochar properties after aging were determined by elemental analyzer,specific surface area analyzer,X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.The effect of aging on the adsorption performance of Pb^(2+)was comparatively studied with aged biochars and pristine biochars.The results indicated the free radicals(methyl radicals)generated by high temperature aging process led to the increasing of oxygen-containing functional groups content on the surface of biochars.The specific surface area of biochars pyrolyzed under 500℃ was greatly increased after aging(from 24.67m^(2)/g to 85.51m^(2)/g),while Zn oxides introduced from modification process were transformed from crystal structures to organic bound forms.The adsorption capacity of Pb^(2+)was increased from 31.18mg/g to 47.70mg/g because of aging processes.However,a slight decrease of oxygen functional groups and Pb^(2+)adsorption capacity(36.05mg/g decreased to 31.92mg/g)was observed for biochars pyrolyzed under 700℃ after ageing at high temperature(90℃),mainly because a self-quenching effect of reactive substances at high ageing temperature and a stable structure for biochar pyrolyzed at 700℃.Findings of this study can provide new insights to the long-term utilization of modified biochar in lead-contaminated soil.