微波及碱性溶液改性活性炭对丙酮吸附性能的影响

Effect of microwave and alkaline solution modification activated carbons on adsorption properties of actone acetone

对商业活性炭分别经过600,700和800℃微波辐照加热处理,以及Na OH,Na2CO3和Na HCO3溶液浸渍处理。采用比表面积及孔径分析仪、Boehm滴定、傅里叶转换红外光谱(FTIR)对活性炭的物化性质进行表征,并且在10℃以丙酮为吸附质进行固定床吸附实验。研究结果表明:微波改性后,活性炭的比表面积、总孔容小幅度减小,但微孔比表面积显著增大;随着温度升高,表面酸性基团大量分解,碱性基团逐渐形成;碱性溶液改性后,比表面积和孔容均减小;改性溶液碱性越强,表面碱性基团总量越大,酸性基团完全被去除;丙酮吸附量与活性炭微孔孔容具有良好的线性相关性,吸附量与活性炭表面碱性基团的含量成反比;Langmuir方程和Freundlich方程均能较好地描述丙酮在活性炭上的吸附,Langmuir方程更加适合;吸附能与活性炭表面含氮官能团总量成正比。

The commercial activated carbons were irradiated with microwave at 600, 700 and 800 ℃ and impregnated with sodium hydroxide, sodium carbonate and sodium bicarbonate respectively. Specific surface area and pore size analyzer, Boehm titration and Fourier transformed infrared spectroscopy （FTIR） were used to study the physicochemical properties of the activated carbons. The fixed-bed adsorption experiments were conducted at 10 ℃ using acetone as adsorbate. The results show that after microwave modification, the specific surface area and total pore volume of activated carbons decrease slightly, but the micropore specific surface area increases remarkably. With the increase of temperature, large number of surface acidic functional groups resolve and surface basic functional groups are formed gradually. Both the specific surface area and pore volume decrease when the alkaline solutions are modificated. With the increase of alkaline of solutions, surface basic functional groups increase remarkably and surface acidic functional groups are removed completely. The relationship between the adsorption capacity of acetone and the micropore volume of activated carbons is linear, the adsorption capacity is inversely proportional to the contents of surface basic functional groups of activated carbon. Both the Langmuir equation and Freundlich equation can describe the adsorption of acetone onto activated carbons, and the Langrnuir equation is more suitable. The adsorption energy is proportional to the contents of surface nitrogen groups of activated carbon.