龙凤檀磷酸法活性炭的孔径分布与吸附性能的构效关系

The Relationship Between Pore Size Distribution and Adsorption Properties of Cumaru Activated Carbon Prepared by Phosphoric Acid Method

以硬杂木龙凤檀的加工剩余物为原料,研究了磷酸活化法的活化温度、磷酸质量分数和浸渍比对龙凤檀活性炭吸附性能的影响,通过N_(2)吸附-脱附等温线对活性炭的结构进行分析,并根据吸附理论和DFT孔径分布图,拟合计算出活性炭有效孔道所占的孔容积与液相吸附性能(碘吸附值、亚甲基蓝吸附值和焦糖脱色率)的构效关系。研究结果表明:在磷酸质量分数60%、磷酸溶液与龙凤檀浸渍比3∶1(mL∶g)、活化温度500℃、活化时间120 min的条件下,磷酸活化法制备的龙凤檀活性炭具有最佳的吸附性能和优异的孔隙结构,碘吸附值为841 mg/g,亚甲基蓝吸附值为270 mg/g,焦糖脱色率为120%,比表面积为1516 m^(2)/g,总孔容为1.145 cm^(3)/g,均优于软杂木杉木制备得到的活性炭。应用密度泛函理论(DFT),计算出龙凤檀活性炭不同孔径区间对应的孔容积,经过理论分析和拟合计算,发现碘吸附值与孔径在1.0~2.7 nm之间的孔容积、亚甲基蓝吸附值与孔径在1.7~5.0 nm之间的孔容积、焦糖脱色率与孔径在2.7~6.3 nm之间的孔容积有着很好的线性关系(R2>0.95),表明活性炭的孔隙结构分布与其液相特征吸附性能之间具有很好的关联度。

The influences of phosphoric acid method activation temperature,phosphoric acid concentration and impregnation ratio on adsorption performance of cumaru activated carbon were investigated by using the processing the residue of hardwood cumaru as a raw material.Structural analysis of activated carbon was analyzed by N_(2)adsorption-desorption isotherm,and the structure-activity relationship between the effective pore volume and the liquid phase adsorption results(iodine adsorption value,methylene blue adsorption value and caramel decolorization rate)were calculated according to the adsorption theory and DFT pore size distribution map.The results showed that the synthesized activated carbon exhibited excellent adsorption properties and pore structure under the conditions of 60%phosphoric acid solution,the impregnation ratio of phosphoric acid to cumaru 3∶1(mL∶g),the activation temperature of 500℃and the activation time of 120 min.Its iodine value,methylene blue value,caramel decolorization,specific surface area,and total pore volume were 841 mg/g,270 mg/g,120%,1516 m^(2)/g and 1.145 cm^(3)/g,respectively.These properties were comprehensively superior to those of the activated carbon prepared from the residues of soft wood fir.The corresponding pore volume of different pore size distributions was calculated for cumaru activated carbon using the Density Functional Theory(DFT).After theoretical analysis and fitting calculation,it was found that there was a good linear relationship between iodine adsorption value and pore volume with pore diameter of 1.0-2.7 nm,between methylene blue adsorption value and pore volume with pore diameter of 1.7-5.0 nm,and between caramel decolorization rate and pore volume with pore diameter of 2.7-6.3 nm.These results indicated a good degree of association(R~2>0.95)between the pore structure distribution of activated carbon and its liquid phase adsorbing performance.