Research On Preparation And Characterization Of Biomass Bamboo Charcoal And Its Dynamic Adsorption Properties For Toluene Gas

Recently,China's environmental protection status is not relaxed,and the battle for pollution is being carried out nationwide.Among them,the management of volatile pollutants(VOCs)emitted by enterprises is particularly important in improving the quality of ambient air.As a typical technology widely used in the treatment of VOCs,adsorption method has many advantages,such as high processing efficiency,convenient operation and good economic benefits.The existing research shows that the core problem in the adsorption process of VOCs is to find suitable and effective adsorbents.Carbon materials have wide application prospects in pollution treatment because of their high specific surface area,adjustable aperture and convenient preparation.In recent years,high-carbon biomass materials have been prepared into biomass carbon through carbonization and activation processes,and are increasingly used in the field of air pollution control.In this paper,bamboo as a biomass carbon source was used to prepare bamboo-based activated carbon through carbonization and activation process,and its characterization test was carried out by various analytical methods.The toluene gas was selected as a gas pollutant to study the dynamic adsorption characteristics of toluene gas on the bamboo-based activated carbon.conclusion as below:(1)Activated carbon prepared from bamboo-based biomass materials is mainly affected by the type of activator,activation temperature,and KOH/C mass ratio during the activation process.Among them,the bamboo-based activated carbon obtained by KOH activation has the largest specific surface area and pore volume;The activation temperature has a direct effect on the specific surface area and pore diameter of the bamboo-based activated carbon.The activation temperature increases and the graphitized structure is destroyed,resulting in more amorphous carbon structure.At the same time,the internal collision of potassium in the carbon material increases the expansion of the material,and the specific surface area and pore volume increased;The KOH/C mass ratio directly affects the reaction rate between KOH and carbon.When the KOH/C mass ratio is suitable,the more active sites KOH forms at high temperature,the faster reaction rate is,and the more micropores generated and the higher the specific surface area is.Under the optimal preparation conditions,the specific surface area and micropore volume of KBC-2-800 were as high as 1847.92 m2/g and 1.07 ml/g,respectively.(2)The initial concentration and the concentration of the inlet gas greatly affect the dynamic adsorption capacity of toluene on bamboo-based activated carbon.When the initial concentration is high,the energy obtained by the adsorbate molecules is larger,which facilitates the diffusion of the adsorbate onto the surface and interior of the adsorbent,increasing the adsorption rate,but also shortening the time of adsorption saturation;The proper intake flow rate can increase the kinetic energy of the toluene gas molecules,so that the molecules can move into the pores of the material,and are firmly adsorbed on the inner wall of the material channel by van der Waals force and internal diffusion effect,and the adsorption capacity was increased;Studies have shown that at an initial concentration of 2 mg/L,a total flow rate of 50 mL/min,a temperature of 40 ? and a mass of 0.1 g of adsorbent,the dynamic adsorption capacity of toluene reached a maximum of 295.68 mg/g.(3)The Langmuir isotherm equation can better fit the toluene adsorption data,and the fitting correlation coefficient can reach 0.9992,indicating that the adsorption process of toluene on activated carbon belongs to monolayer adsorption;The Yoon-Nelson model can better fit the toluene adsorption breakthrough curves at different initial concentrations and inlet flow rates.The theoretical half-breakthrough time calculated from the model can be consistent with the actual half-breakthrough time obtained.It indicates that the data are highly reliable and can predict the adsorption behavior of toluene.(4)The steam thermal desorption method can efficiently complete the regeneration of bamboo-based activated carbon.The porous structure and surface chemistry of the regenerated bamboo-based activated carbon were well maintained,and the mass transfer rate and tolerance did not change significantly.The adsorption capacity decreased slightly with the number of regenerations,but it basically kept decreasing regularly.The saturated adsorption capacity in the 5 times toluene dynamic adsorption cycle exceeded 200 mg/g.