氧等离子体对竹炭表面的改性研究

Effect of oxygen plasma modification on the surface properties of bamboo charcoal

采用氧等离子体对竹炭进行了3种不同时间的改性,分析和评价改性前后竹炭的表面性质变化。扫描电镜照片显示改性前后竹炭的表面微观形貌没有发生明显的变化;红外光谱分析表明改性前后的竹炭表面基团种类未发生明显变化,但是在3 440 cm-1处的吸收峰强度明显提高;比表面积和孔径分布结果表明,改性时间为8和16 min的竹炭比表面积、总孔容积、微孔容积和微孔表面积相比未改性竹炭有较大幅度增加,提高幅度分别达到24.95%,19.50%,16.26%和14.92%;X射线光电子能谱分析表明,改性后竹炭的表面氧原子百分比从改性前的19%增加到45%左右,并且氧原子在竹炭表面的基团结合形式随着改性时间的延长而发生变化。Bohem滴定的结果表明,改性后竹炭表面的酸性明显增加,并且主要表现为羧基数量的增加。因此,氧等离子体对竹炭材料表面性质具有明显的改善作用。

In recent years,the surface modification has been proven to be a promising technology to enhance the adsorption capacities of carbonaceous materials to certain adsorbates. Among these surface modification methods,the low temperature plasma has some special advantages. In this paper,the oxygen plasma was introduced to modify the surface properties of commercial bamboo charcoal and the modification effect was intensively evaluated by different methods. The SEM images of modified bamboo charcoals showed no apparent structure destruction compared with that of raw bamboo charcoal. The FTIR spectra of the bamboo charcoals were quite similar before and after modification,but the intensity of peaks at 3 440 cm- 1were substantially increased on the FTIR spectra of modified bamboo charcoals,which indicated the growth of hydroxyl groups on modified bamboo charcoal surface. The specific surface area,total pore volume,micropore volume and micropore surface area of bamboo charcoals modified for 8 and 16 min were enhanced greatly as 24. 95%,19. 50%,16. 26% and 14. 92%,respectively,which showed that the considerable transformation of porosity on modified bamboo charcoal surface. The XPS spectra of the bamboo charcoals suggested that the oxygen content of modified bamboo charcoals increased dramatically from 19% before modification to 45% after modification. However,the species of oxygen-containing groups on three modified bamboo charcoals were quite different,and the subsequent analysis showed these oxygen atoms were mainly fixed in the carboxyl groups. The Bohem titration results showed that the increase of total acidity on modified bamboo charcoals and the growth of carboxyl groups should be responsible for this variation. In conclusion,oxygen plasma has obviously modification effect on bamboo charcoal.