热解温度对松树锯末炭吸附硝基苯酚的响应研究

Study on the Response of Adsorption Characteristics of PNP by Pine Sawdust Biochar to Its Pyrolysis Temperature

在300~700℃下制备松树锯末生物炭(PC300、PC400、PC500、PC600和PC700),对其进行表征并考察了其吸附对硝基苯酚(PNP)的特性。结果表明,随着热解温度升高,生物炭表面结构更复杂,芳香性增强,极性减弱。碱性条件下,溶液pH对吸附量影响较大。准2级动力学和Langmuir等温模型能更好描述PNP在低温生物炭(PC300、PC400)上的吸附,高温生物炭(PC500、PC600、PC700)吸附PNP更符合Elovich动力学模型和Freundlich等温模型。生物炭吸附PNP的速率受液膜扩散和颗粒内扩散控制,低温生物炭上的吸附以静电作用为主,高温生物炭上的吸附以氢键和π-π相互作用为主。PNP在PC700上的动态吸附适合用Thomas模型描述,动态吸附量达135.8 mg/g。热解温度对松树锯末生物炭的理化性质及其吸附过程、机理均有一定影响。

Pine sawdust biochars were prepared at 300~700 ℃(PC300, PC400, PC500, PC600 and PC700). These biochar samples were characterized and the p-nitrophenol(PNP)adsorption properties were investigated. The result indicates that the surface structure of biochars becomes more complicated with the increasing pyrolysis temperature, along with the aromaticity increased and the polarity decreased. The solution pH value has a great influence on the adsorption capacity under alkaline conditions. The low-temperature biochars can be well described by the pseudo-second-order kinetics model and Langmuir isotherm model, while the adsorption of the high-temperature biochars agree well with the Elovich kinetics model and Freundlich isotherm model. The adsorption rate of PNP on the biochars is mainly controlled by film diffusion and intra-particle diffusion. The adsorption of PNP on the low-temperature biochar was found through electrostatic interaction, while adsorption on the high-temperature biochar was found through hydrogen bonding and π-π interaction. The dynamic adsorption behavior of PNP on PC700 is suitable to be described by the Thomas model, and the adsorption capacity is 135.8 mg/g. The pyrolysis temperature has certain effects on the physicochemical properties, adsorption process and mechanism of the pine sawdust biochar.