Page - 150 - in Advanced Chemical Kinetics

3.10, 3.12 and3.18 eV, respectively (Figure 1F). Thus, supported catalysts have suitable band gapenergies for thedegradationofMOunderUV-Airradiation. 3.5.XPSanalysis XPSanalysis is alsoperformed to control the surface structure of the 0.5MZnO-FA-Sep. The survey scan reveals Zn peaks in addition to theAl (75.6 eV), Si (103 eV), Ca (347.07 eV), O (531.47eV)andsomeAugerpeaksof theFA-Sepsupport (Figure1G).Thedoublet inZnpeaks correspondstoZn2p3/2and2p1/2core levels (Figure1H).Znexistsmainly intheformofZn2+ oxidationstateonthecatalyst surfaceowingto thesharpness inZn2p3/2peak[23].Thebroad O 1 s signal of the 0.5 M ZnO-FA-Sep catalyst is deconvoluted by four subspectral parts (Figure 1I). CaOandAl2O3 (531.03 eV, 26.9% spectral area), oxygen in the formof Zn(OH)2 (531.69 eV, 18.5% spectral area), SiO2 (532.59 eV, 22.3% spectral area) and adsorbed water (533.58eV,32.2%spectralarea)are labeledas thecomponentsof thesupportedcatalyst. 4.Adsorptionandphotocatalyticapplications 4.1.Controlexperiments Prior to the evaluation of photoactivities of the supported catalysts in detail, two control experiments are designed. As a first step, photolysis ofMO is tested underUV illumination andanegligibledegradationisfound(Figure2A).Then,FA-Sep,0.25MZnO-FA-Sepand0.5M ZnO-FA-Sep are examinedwithout irradiation. In thepresence of FA-Sep, the remainingMO percentages in the solution are detected as 84% for decolorization and 85% for degradation. However, supported catalysts reveal better adsorption capabilities in comparison to FA-Sep, which furtherenhancedwith theZnOloadingconcentration.Accordingly,0.25MZnO-FA-Sep demonstrates75%(fordecolorization)and73%(fordegradation)MOstayinginsolutionwithin 30min and thereafter no significant change is noticed. Contrarily, 0.5MZnO-FA-Sep shows rapiddecrements inbothdecolorization(7%)anddegradation(5.3%)processeswithin80min. MOexists in the anionic form inwater since its natural pH (5.85) is higher than its pKa (3.4) value [24].ThealkalinecharacterofFA-Sep (pH=10) solution,hence, induces repulsive forces among the MOmolecules and FA-Sep. However, the weak interaction between positively charged species (Fe2O3, TiO2 asminor phases) within the disordered FA-Sep structure and negatively chargedMOmoiety induce decrements inMO percentages. The attraction may proceed through the chromophoric (dN]Nd) group and declines the absorption band at 464 nm. Simultaneously, weakening in the conjugation disrupts the benzenic rings and decreases the 274 nmband. The presence of ZnOnanoparticles in the supportedmatrixes is expected to increase the contact among the supported catalysts andMOmolecules which eventually facilitate thedegradationanddecolorizationprocesses. Inthesecondset, thephotoactivitiesof thesupportedcatalystsarecontrolledunder irradiation (Figure 2B). The lowest MO remaining percentages with slower rates are obtained in the presence of 0.125MZnO-FA-Sepwithin 130min (45% fordecolorization and47% fordegra- dation). The increment in theZnOconcentration improves theperformances of the catalysts. Advanced Chemical Kinetics150