The Preparation Of Pineapple Waste-based Activated Carbons And Their Capture Performance Toward Low Temperature CO₂

Fossil fuel combustion has caused major environmental problems,the most important of which is carbon dioxide?CO2?emissions come from flue gas exhaust.Therefore,low temperature CO₂ capture in the exhaust gas?<200??can effectively improve the atmospheric environment while obtaining carbon resources.At present,the solid adsorption is the most common method to capture CO₂ gas,and the activated carbon is widely used due to its advantages of low cost and good chemical stability.In this paper,pineapple waste was used as carbon source.Pineapple waste-based activated carbons were prepared by using different activators and synthetic routes,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray powder diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,X-ray photoelectron spectroscopy?XPS?,comprehensive thermal analysis and nitrogen adsorption-desorption were used to analyze the physicochemical properties of the samples.The static and dynamic CO₂ adsorption performances of those activated carbons were also tested.In this thesis,the formation process,activation mechanism,low temperature CO₂ adsorption performance and adsorption mechanism of activated carbon were studied.The main results are as follows:1.Using pineapple waste as raw material,the effects of three alkali metal oxalates?lithium oxalate Li₂C₂O₄,sodium oxalate Na₂C₂O₄ and potassium oxalate K₂C₂O₄?on the carbonation and activation of pineapple waste were compared when activated carbons were prepared by hydrothermal and high temperature activation.It was found that compared with the macroporous and mesoporous carbon activated by Li₂C₂O₄ and Na₂C₂O₄,the carbon activated by K₂C₂O₄ is mainly microporous,and the specific surface area of C-K-700 which was activated by K₂C₂O₄ at 700? is up to 1076.3 m²·g^-1.C-K-700 has the best CO₂ adsorption performance,and the CO₂ adsorption capacity are 5.32 mmol·g^-1 and 4.25 mmol·g^-1 at 0? and 25?,1 bar,respectively.The CO₂adsorption capacity after 12 cycles adsorption still reached 3.49 mmol·g^-1.The CO₂/N₂adsorption selectivity of C-K-700 is 18.24 at 25?.The adsorption kinetics study shows that C-K-700 can reach the maximum adsorption capacity in 4 min,and its dynamic CO₂ adsorption capacity is 0.9282 mmol·g^-11 at 25?.2.Based on the preparation of hydrothermal carbon spheres from pineapple waste by ammonium persulfate?APS?assisted hydrothermal treatment,the formation mechanism of activated carbon prepared by three activators?potassium tartrate C₄H₄O₆K₂,potassium oxalate K₂C₂O₄ and potassium hydroxide KOH?and the activation mechanism differences of activators were compared.It was found that compared with K₂C₂O₄ and KOH,the carbon activated by C₄H₄O₆K₂?ACS-C₄H₄O₆K₂?was mainly composed of porous carbon microspheres with particle size of 2⁴?m,with higher micropore distribution rate and specific surface area(1689.5 m²·g^-1).ACS-C4H4O6K2 has the best CO2 adsorption performance,and the CO2 adsorption capacity are 6.45 mmol·g^-1 and 3.80 mmol·g^-1 at 0? and 25?,1 bar,respectively.The CO₂adsorption capacity after 10 cycles adsorption still reached 3.57 mmol·g^-1.The CO₂/N₂adsorption selectivity of ACS-C4H4O6K2 is 8.98 at 25?.The adsorption kinetics study shows that ACS-C₄H₄O₆K₂ can reach the maximum adsorption capacity in 5 min,and its dynamic CO₂ adsorption capacity is 0.74 mmol·g^-11 at 25?.