| The water pollution in urban areas of China is serious,and 40%of the water sources in urban areas are unable to drink normally.60%–70%of the total population water shortage rate is mainly caused by water pollution.Malachite green(MG),as a typical organic component in industrial wastewater,has of high toxicity and long incubation period,which has great harm to human environment.In this index work,the efficient removal of malachite green was taken as the research objective,and pine sawdust was used as raw material to prepare high-performance biomass activated carbon by combining hydrothermal pretreatment with chemical activation.The performance characteristics and mechanism of MG adsorption by biomass activated carbon were studied.The main research results are as follows:(1)With pine sawdust as raw material,carbon yield and adsorption capacity as indexes,high-performance activated carbon was prepared by coupling hydrothermal pretreatment method and high-temperature activation method.The influence of activation temperature,time and carbon-base ratio on the performance of activated carbon and its mechanism were studied.The results showed that when the activation temperature was 800°C,the activation time was 90 min and the ratio of carbon to alkali was 1:2,the specific surface area of the prepared activated carbon was 1999 m~2/g,the pore size was mainly micropores,and the adsorption amount of MG solution was2209.07 mg/g.The adsorption of MG on activated carbon is monolayer adsorption,and the adsorption process can be described by Langmuir isothermal adsorption model.The adsorption is controlled by chemical adsorption,which is mainly caused by the electron sharing between MG molecules and activated carbon surface.From the thermodynamic point of view,the adsorption of MG by activated carbon is an entropy driven endothermic process,and the increase of temperature is beneficial to the adsorption of MG by activated carbon.(2)The activated carbon was modified by sodium dodecyl benzene sulfonate(SDBS),and the influence law and mechanism of SDBS solution concentration on the adsorption performance of modified activated carbon were revealed.The results showed that the activated carbon prepared with the surfactant SDBS concentration of0.25 g/L had the best adsorption performance,and the adsorption capacity was 2772.04mg/g at 35°C.SDBS modification increased the number of active sites and improved the surface hydrophobicity of activated carbon.Therefore,although the specific surface area of modified activated carbon decreased by 21.75%,the adsorption capacity of MG increased by 4.4%.The adsorption of SDBS modified activated carbon on MG was monolayer adsorption and dominated by chemical adsorption.The adsorption process was spontaneous and entropy-driven endothermic process.(3)The results of chemical regeneration of activated carbon showed that ethanol had the best desorption effect on MG among the four desorption agents.The desorption rate of activated carbon was 6.42%,and that of modified carbon was only 4.11%.The regeneration performance of SDBS modified activated carbon was worse than that of unmodified activated carbon because ethanol destroyed the combination of SDBS hydrophilic group and malachite green cationic group.Chemical adsorption plays a major role in the adsorption mechanism of malachite green by activated carbon and modified activated carbon,and the chemical regeneration method cannot achieve the ideal cyclic adsorption amount and regeneration life. |
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