Preparation And CO₂Adsorption Of Sargassum Horneri Based Carbon Materials

The preparation of biomass based carbon materials not only realizes the recycle of waste resources, but also meets the huge demand of functional carbon materials, such as activated carbon etc. Biochars possess a wide application prospect both in energy and environment because of their characteristics of high specific surface area, rich pore structures and easy modification of surface.Compared with corps which need vast areas, the macroalgae has many advantages such as short vegetative cycle, rich resources in the sea and low-cost in pretreatment. It has been chosen for the most suitable energy carrier by the Food and Agriculture Organization of the United Nation. As a kind of macroalgae with excellent marine environmental remediation ability, Sargassum Horneri was employed to prepare porous carbon in this paper. Based on the analysis of chemical compositions, biochars were prepared by hydrothermal carbonization(HTC), orthogonal method was used to determine the optimal preparation conditions. Besides, the activation of Sargassum Horneri based biochar was conducted by potassium hydroxide, the effect of the modifying conditions on the surface structure was studied. The carbon materials were applied in pure CO2adsorption.The results indicated that:(1)The optimal preparation conditions of Sargassum Horneri based hydrochars were reaction time of2h, reaction temperature of180℃and the weight ratio of Sargassum Horneri to deionized water of1/4. Under the conditions, the carbon recovery rate could reach65.0%, with the yield of51.4%.(2)The hydrochar obtained under the optimal preparation conditions with the specific surface area of26.6m2·g-1, pH value of4.8, had high O/C value and low C/N value. Compared with biochars produced by dry pyrolysis, hydrochars were found to have more oxygen-and nitrogen-containing functional groups, stronger hydrophilicity, lower ash content and higher carbon recovery rate.(3)The extra macroporous structure in the hydrochars favored the diffusion of KOH. The distribution of pore size centralized and the micropore mainly existed on the surface of the activated carbon. The optimal preparation conditions of activated carbon evaluated by the equilibrium adsorption quantity of pure CO2were the raw of hydrochar obtained at180℃, the mass ratio KOH/raw=1, the temperature of600℃and the reaction time of2h. Under such conditions, the equilibrium adsorption quantity of pure CO2at30℃and1atm was102mg·g-1. (4)The adsorption of CO2by activated carbon mainly belonged to physical adsorption. The pseudo-first order model matched the CO2adsorption kinetics. The adsorption regenerability of material was powerful.