Development of surface modification method for functinalization of activated carbon

本文的目的是以吸附物质为探针分子，阐明改性活性炭的表面特性，并在此基础上建立有效的活性炭表面改性方法。选取吸附在活性炭上的一氧化碳和两个单环芳香族分子作为探针分子，对其红外光谱进行了分析。在123K下吸附CO的IR波段可以解旋成两个峰（2137cm^<-1>和2155cm^<-1>），它们分别被分配到石墨片上和表面极性位上的附加物质。红外光谱和XPS分析表明，电场来源为表面氧化基团。室温下吸附苯的红外光谱也表明，苯在低覆盖率下的吸附位点是石墨片，但极性位点在高覆盖率下也与苯分子发生电相互作用。通过氧化处理将表面氧化基团（酸酐酸和内酯）引入活性炭表面，作为CO（或苯）的弱相互作用吸附位点。站点的数量可以使用本研究中的分析来讨论。在室温下，吡啶吸附在活性炭上的红外光谱表明，在活性炭表面存在少量弱路易斯酸位点。H_2O_2处理使表面酸位增加。另一方面，HNO_3处理引入了表面-NO_2基团。部分官能团暴露在活性炭表面，作为有效的吸附位点。研究中所进行的分析使选择性地讨论活性炭上的实际吸附位点成为可能。结果表明，这些分析有助于优化碳表面的处理条件。

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.