# Decolorization of Orange-G Aqueous Solutions over C\({}_{60}\)/Mcm-41 Photocatalysts  
[PERSON]  
1 Department of Chemistry, University of Patras, GR-26504 Patras, Greece; [EMAIL_ADDRESS] (J.K.); [EMAIL_ADDRESS] (C.K. ); [EMAIL_ADDRESS] (A.L.) [PERSON]  
1 Department of Chemistry, University of Patras, GR-26504 Patras, Greece; [EMAIL_ADDRESS] (J.K.); [EMAIL_ADDRESS] (C.K. ); [EMAIL_ADDRESS] (A.L.) [PERSON]  
2 School of Science and Technology, Hellenic Open University, Tsamadou 13-15, GR-26222 Patras, Greece; [EMAIL_ADDRESS] ([PERSON]DDRESS] ([PERSON]DDRESS] ([PERSON]@upatras. inorganic contaminants [15; 16; 17]. The majority of the photocatalysts studied are based on semiconductor materials [18; 19]. Studies reported on non-semiconducting materials are very scarce [20; 21; 22]. UV irradiation produces holes and electrons in the valence and conduction bands of semiconductor materials, respectively. The holes oxidize OH\({}^{+}\) to OH\({}^{\spadesuit}\) free radicals. These are oxidative agents with high oxidative potential and may mineralize the dyes. Hydrogen peroxide also produces hydroxyl radicals and therefore sometimes is added to the reactor for achieving faster photocatalytic oxidation [23]. Photocatalytic degradation of dyes can be also achieved by singlet oxygen which is 1 eV stronger oxidative agent in comparison to the oxygen fundamental state and therefore strongly electrophilic [24]. Fullerenes have attracted special interest as photocatalysts due to their unique structure and properties [25; 26]. In particular, the photoreactivity of C\({}_{60}\) has received considerable attention due to its electron acceptability, intense absorption in near-UV light, and broad absorbance in the visible light region. A number of studies of our group have been reported dealing with C\({}_{60}\) as a photocatalyst [27; 28; 29; 30; 31; 32]. However, there are very few studies on the photocatalytic performance of C\({}_{60}\) in aqueous solutions because it exhibits very low solubility in this solvent. Immobilization of C\({}_{60}\) on high surface area supports is expected not only to inhibit aggregation of C\({}_{60}\) molecules but also allows recycling of the supported photocatalyst and prevents potential environmental release of fullerene as there is an emerging consensus concerning the in vivo toxicity of these carbon nanoparticles [33]. Non-semiconducting materials like \(\gamma\)-Al\({}_{2}\)O\({}_{3}\), SiO\({}_{2}\), and MCM-41 exhibit high surface areas suitable to immobilize highly dispersed C\({}_{60}\) moieties [27; 29; 30; 31; 32; 34]. Recently, the photocatalytic degradation of methyl orange has been achieved even under visible irradiation over C\({}_{60}\)/SiO\({}_{2}\) photo-catalyst in the presence of ascorbic acid [20]. The main advantage of using fullerene for photocatalytic water decontamination lies in its efficiency to activate reactive oxygen species even under visible light. The latter species are able to degrade micropollutants found in water [34]  
A critical question at this point is whether the decolorizing activity of supported C\({}_{60}\) is limited to methyl orange, eventually related to its molecular structure, or can it be applied generally for decolorizing aqueous systems. This is the reason for which the present study deals with decolorization of aqueous solutions containing Orange G. Orange G is an azo-dye with a wide range of applications (coloring wools and silks; pigmentation of paper, leather, and timber; printing ink; pH indicators; etc.) [10]. It is usually present, as a sodium salt, in two tautomeric forms in aqueous solutions. Organic solvents favor the azo form. In contrast, the hydrocarbon form predominates in aqueous solutions. In the present article, we attempt to develop non-semiconducting materials for the decolorization of aqueous media with two main characteristics: very high specific surface area enhancing the adsorption of dyes and quite high photocatalytic activity.