Development of surface modification method for functinalization of activated carbon

以吸附在活性炭表面的一氧化碳和两种单环芳香族分子为探针分子，分析了活性炭表面的红外光谱，并对活性炭表面的物理吸附物种进行了表征，为活性炭表面改性提供了理论依据。CO在123 K时的红外吸收峰可退卷积为2137 cm ↑ [2]<-1>和2155 cm ↑ [2<-1>]，分别归属于石墨片上和表面极性位上的吸附物种。红外光谱和X射线光电子能谱分析表明，电场的来源是表面的氧化基团。室温下苯吸附的红外光谱也表明，在低覆盖度下，苯的吸附位是石墨片，而在高覆盖度下，极性位也与苯分子发生电性相互作用。通过氧化处理在活性炭表面引入了酸酐、内酯等表面氧化物基团，这些基团对CO（或苯）具有弱吸附作用。吡啶在活性炭上的室温红外光谱表明，活性炭表面存在少量的弱刘易斯酸中心。H_2O_2处理使表面酸中心增加。而HNO_3处理则在表面引入了一个-NO_2基团。部分官能团暴露在活性炭表面，是活性炭的有效吸附位点，本研究的分析结果为选择性地探讨活性炭表面的真实的吸附位点提供了可能。结果表明，这些分析对优化碳表面处理条件是有用的。

The purpose in the present work is to clarify the surface characteristics of modefied activated carbons using physisorbed species as probe molecule and to construct methodology of effective surface modification for activated carbons on the basis of the analyses.Carbon monoxide and two monocyclic aromatic molecules adsorbed on activated carbons were selected as probe molecule, and the IR spectra were analyzed. The IR band of adsorbed CO at 123K can be deconvoluted into two peaks (2137cm^<-1> and 2155cm^<-1>), and they are assigned to adspecies on graphite sheets and on surface polar sites, respectively. The source of electric field was suggested to be surface oxide groups from IR and XPS analyses. IR spectra of benzene adsorbed at room temperature also revealed that the adsorption site for benzene is graphite sheet at low coverage, but polar site also interacts at high coverage with benzene molecule, electrically. Surface oxide groups (anhydride acids and lactones) were introduced onto the activated carbon surface by oxidation treatment, and the sites act as adsorption site for CO (or benzene) with weak interaction. The amount of sites can be discussed using the analyses in this study.IR spectra of pyridine adsorbed on the activated carbons at room temperature showed the presence of small amount of weak Lewis acidic sites on the surfaces. The surface acid sites were increased by H_2O_2 treatment. On the other hand, a surface -NO_2 group was introduced by HNO_3 treatment. A part of functional groups was exposed on the activated carbon surface, and acts as effective adsorption site.The analyses developed in the study make possible to discuss real adsorption sites on the activated carbons selectively. It is found that the analyses are useful to optimize treatment conditions of the carbon surfaces.