Preparation Of Activated Carbon Derived From Sugarcane Bagasse For CO₂ Adsorption

The concentration of CO₂ in the atmosphere due to human activities and industrial production has been risen sharply.The excessive CO₂ in the atmosphere will cause serious ecological safety problems such as global warming,sea level rising and extreme weather.In recent years,CO₂ concentration in the atmosphere are still increased with a rate of 0.1%every year.CO₂ capture is considered as one of the most feasible technologies of suppressing the global warming.Hence,it is urgent to develop a low-cost and highly efficient CO₂ adsorbent.The char was prepared by pyrolysis and hydrothermal method under different temperature,which were called C-t and HC-t respectively.At the same time,the characteristics of the chars were characterized by elemental analysis,FT-IR,N2 and CO2adsorption.It was found that the carbon content of C-600 and HC-240 were the highest,which was 84.07 wt%and 70.88 wt%,respectively.More oxygen-containing functional groups were formed during the hydrothermal process.The CO₂ uptake of C-t was higher than that of HC-t,which was probably attributed to that C-t posed more micropores,and while HC-t had more mesopores.In order to improve CO₂ uptake ability,the C-t was activated via urea-KOH method.Moreover,the influence of the preparing parameters such as urea addition,KOH/carbon ratio and activation temperature on the pore textural properties and CO₂ uptake capacity were investigated.The experimental results indicated that the activated carbon prepared at 600 ^oC activated temperature with 15 wt%urea additions and KOH/carbon ratio of 2.0,had the highest CO₂ uptake of 4.80 mmol/g at 25 ^oC and 1 bar.It was suggested that the synergetic effect of narrow micropores and nitrogen content were responsible for it.Moreover,it was also observed that there were N-6,N-5,N-Q and N-X functional groups at the surface.The ACs had uniform micropores??0.55?nm?and the narrow micro-pore volume?pore width<1 nm?fraction was 80-89%.Hence,the ACs had an excellent CO₂/N₂ selectivity.The CO₂ uptake of the ACs was almost constant even after five runs of CO2 adsorption/desorption,which meant that the stability and regenerability for CO2adsorption were well.HC-240 was activated by KOH to prepare the hydrothermal activated carbon.The influence of KOH/HC-240 ratio and activation temperature on the pore textural properties and CO₂ uptake capacity of adsorbents were also investigated.It was found that the ACs activated at 800 ^oC with KOH/HC-240 ratio of 1.0 had the highest CO₂ uptake,about 4.15mmol/g at 25 ^oC and 1 bar.The concentration of-OH and-COOH functional groups at the surface of the ACs were increased after the CH₃COOH modification,which was benefit to improve the CO₂ adsorption capacity.The CO₂ adsorption capacity of the ACs modified with 5 wt%CH₃COOH was increased by 7.8%,about 4.47 mmol/g at 25 ^oC and1 bar.