Preparation Of Algal Porous Carbon And Its Adsorption Performance Of Volatile Organic Compounds

The management and control process of volatile organic compounds(VOCs)are the emphasis of air pollution prevention in the 14th Five-Year Plan.Porous carbon materials are usually used for adsorption and removal of VOCs due to their high efficiency,economical application,and environmental friendliness.However,common commercial carbon materials still have many shortcomings,such as low adsorption capacity,short use time,few cycles,and so on.Therefore,the development of reasonable porous carbon preparation technology,and the porous carbon materials optimization of the pore structure,while increasing the number of surface functional groups to improve the polarity of carbon materials,is an effective strategy to improve the adsorption capacity of porous carbon materials on VOCs.In this research,for regulating the structure and properties of carbon materials,heteroatomic doping and activation were used to modify and prepare two kinds of ultra-high specific surface area and O/N co-doped algal porous carbon,which significantly improved the adsorption characteristics and cyclic application performance of polar and non-polar VOCs.The adsorption mechanism between modified porous carbon and polar and non-polar VOCs was determined by characterization analysis and theoretical simulation.The main research contents and conclusions are as follows:For polar VOCs,O/N co-doped Enteromorpha porous carbon(EONCs)with rich functional groups on the surface was prepared by means of surface polar modification of carbon materials,using abandoned biomass Enteromorpha as raw material,pre-carbonization and urea doping calcination.The dynamic adsorption capacity of EONCs600 for polar VOC acetone is up to 461.7 mg/g,which is significantly higher than that of commercial activated carbon.The oxygen-nitrogen functional groups on the surface of EONCs changed the electronic structure of the carbon surface and enhanced the electronic interaction between acetone and the carbon layer,thereby increasing the adsorption capacity for acetone.The adsorption mechanism of EONCs for acetone is mainly attributed to the polar interaction forces of acetone by abundant oxygen-nitrogen groups on the surface,such as hydrogen bonds and van der Waals forces,while the ultra-high specific surface area brought about by the abundant three-dimensional pore structure for acetone.Adsorption is also very important.Density functional theory simulation results show that the oxygen and nitrogen groups on the surface of EONCs are beneficial to their adsorption of acetone,and the order of enhancing the adsorption capacity is carbon-oxygen single bond<carboxyl group<hydroxyl group<carbonyl group,graphitic nitrogen<nitrogen oxides<pyridine nitrogen<pyrrole nitrogen.Aiming at non-polar VOCs,a kind of kelp porous carbon(KPCs)material with ultra-high specific surface area was prepared by optimizing pore structure of porous carbon,using kelp waste as raw material and potassium hydroxide as alkali activator.Among them,the specific surface area of KPC-2 porous carbon is as high as 3235 m~2/g,and the pore volume is as high as 2.0 cm~3/g.At the same time,KPC-2 exhibits excellent adsorption capacity for non-polar VOC toluene:the adsorption capacity is as high as 691.1 mg/g,which is 12 times that of ordinary commercial activated carbon,and it can still maintain95.5%of the initial toluene after 10 cycles of use adsorption capacity.The adsorption mechanism of toluene by KPCs is mainly due to the pore filling effect brought by the abundant three-dimensional pore structure,in which the micropore filling plays a leading role,and the mesopore and macropore structure mainly play the role of pores in the process of gaseous molecular diffusion.Nitrogen and oxygen doping had little effect on the adsorption process of non-polar VOCs,and the presence of graphitic nitrogen and pyridine nitrogen would promote the adsorption of toluene on KPCs by electrostatic force orπ-πinteraction mechanism.In summary,the modified porous carbon materials prepared in this study have excellent physical and chemical properties and VOCs adsorption performance,which provides a theoretical basis for efficient purification of organic waste gas,and is of great significance for the reuse of waste biomass materials and the prevention and control of air pollution.