活性炭纤维孔结构和表面含氧官能团对甲醛吸附性能的影响

Effect of Pore Structure and Surface Oxygen-Containing Groups of Activated Carbon Fiber on Formaldehyde Adsorption Performance

通过对活性炭纤维(ACF)进行热处理和氧化改性得到具有不同比表面积、孔结构以及含氧官能团的ACF样品,并对这一系列样品进行甲醛吸附研究。实验结果表明,沥青基活性炭纤维(P-ACF)OG-5A具有最小的比表面积和孔容,具有最大的甲醛穿透容量。通过回归分析表明,ACF样品的甲醛穿透容量主要由孔径为0.9~1.8nm的孔的比表面积和孔容来决定,而不是取决于总比表面积和总孔容。P-ACFOG-7A的氧化改性显著提高了样品的甲醛吸附能力,其中浓HNO3改性后提升效果最为明显,改性后穿透容量为58.21mg/g,是未改性样品穿透容量的2.5倍。氧化改性ACF表面含氧量的增加使得甲醛吸附能力增强,进一步通过Boehm滴定实验和回归分析表明酸性含氧官能团(酚羟基、内酯基、羧基等)数量的增加是ACF样品甲醛吸附能力提升的主要原因。酸性含氧官能团富含C=O、C—OH等亲水基团,对甲醛的吸附十分有利。

With the increasing pollution of indoor air of formaldehyde,a simple and convenient adsorption technology is desired.Activated carbon fibers (ACF) is an excellent formaldehyde adsorbent material.Pitchactivated carbon fibers with different surface areas,pore size distribution and surface oxygen-containing groups were obtained by heat treatment and oxidative modification,and were applied to study the adsorption capacity of formaldehyde.The results indicated that P-ACF OG-5A with the smallest BET surface area and pore volume showed the highest adsorption capacity with a breakthrough capacity of 38.73 mg/g.Regression analysis showed that the formaldehyde breakthrough capacity was determined by the surface area and pore volume of ACF with pore size from 0.9 nm to 1.8 nm,instead of BET surface area and total pore volume.Secondly,the formaldehyde adsorption capacity of P-ACF OG-7A was greatly improved after the oxidative treatments by air,hydrogen peroxide and nitric acid.The oxidative treatment by nitric acid (65%) gave rise to the highest adsorption capacity with the breakthrough capacity of 58.21 mg/g,which is 2.5 times higher than that of the sample without treatment.The increased oxygen content in ACF enhanced the formaldehyde adsorption capacity.To further study the mechanism by which the formaldehyde adsorption capacity was increased,Boehm titration and regression analysis were used.The results showed that the numbers of acidic oxygen-containing groups (phenolic hydroxyl groups,lactone groups,carboxyl groups,etc.) in ACF were the main reason that led to the increase in formaldehyde adsorption capacity.The acidic oxygen-containing groups were mainly composed of hydrophilic groups like C= O,C-OH which could react with formaldehyde and enhance the formaldehyde adsorption capacity.