Preparation And Characterization Of TiO₂/Activited Carbon Composite Materials Obtained Via Sol-Gel Method

In the present work, nano-size TiO₂ photocatalyst, TiO₂/AC composite photocatalyst andadsorption-photocatalysis bi-functional activated carbon materials were prepared by sol-gelmethod using Ti(OBu)₄ as precursor. SEM equipped with EDAX, N₂ (77 K) adsorptionisotherm, FTIR, XRD and DRS were used for materials characterization. The details were asfollows:1,In the present work, nano-size titanium oxide (TiO₂) powder photocatalyst wasprepared by sol-gel route using Ti(OBu)₄ as precursor. The preparation parameters areoptimized by means of phenol degradations. The optimum conditions are obtained as follows:V_Ti(OBu)4=35 mL, V_H2O=32.4 mL, V_EtOH=105 mL(V_A,EtOH=35 mL, V_B,EtOH=70 mL), V_HAc=23 mL (n_Ti(OBu)4:n_H2O:n_EtOH:n_HAc1:18:18:4) and calcined at 450℃for 2 h. Withthe calcination temperature increased, uncrystalline TiO₂ prcursor was completely transformedinto anatase at 400℃, accompanying with the S_BET decreased and particle size increased.Transformation of anatase to rutile occurred at 600℃finished at 700℃and accompanied withthe red-shift of TiO₂ threshold.2, TiO₂/xAC composite photocatalysts were prepared by sol-gel method. Phenol,methyl orange, Cr(â…¥) and nitrobenzene were used as target pollutants to test the activity anddecantability. The results showed that AC can provide high organic concentration for TiO₂,TiO₂/xAC catalysts with optimal AC content 9%(w%) exhibited the most high activity, whichwas higher than TiO₂ and commercial P-25. Also, phenol removal of 93.04% can be achievedeven when TiO₂/9AC was used for 10 run cycles and TiO₁/9AC exhibited good decantability.Synergy coefficient observed for TiO₂/5AC, TiO₂/9AC and TiO₂/15AC was 1.09, 1.53 and 1.29,respectively. Results of XRD and SEM revealed that the addition of AC can improve the dispersion of TiO₂, derease the aggregation size and inhibit the phase transformation formanatase to rutile. UV/DRS revealed that AC has almost no effect on the electronic bandgapchanges of TiO₂. Result of FT-IR suggest a conjugation effect was present between the ACbulk and Ti-O bond.3,Effect of activated carbon kinds (pore structure and surface properties) on thephotocatalytic activity of TiO₂/9ACx composite photocataylyst was invesigated. The resultsshowed that pore structure of AC has great influence on the activity of TiO₂/9ACx compositephotocataylyst. Different composite photocatalysts TiO₂/9ACx with various AC exhibiteddifferent photocatalytic activity for the degradation of phenol, methyl orange, Cr(â…¥) andnitrobenzene. Generally speaking, TiO₂/9AC₁ has higher photocatalytic activity to each targetpollutants, Which may caused by the more macropores.4,Adsorption-photocatalysis bi-functional carbon materials could be obtained withhigh AC content and less titania. The results showed that AC/50TiO₂ not only exhibited hashigher photocatalytic activity for phenol removal, but also large adsorption capacity. After 10runs, 40.76% phenol could be adsorbed without illumination and 81.98% of phenol could bephotocatalytic removed on AC/50TiO₂ within 120 min. In all there 443.36 mg/g phenol couldbe removed on AC/50TiO₂ in ten runs, the quantity was twice and half times than unlouded AC,which only removed 174.04 mg/g phonel in all.5,Commercial activated carbon was treated by HNO₃ oxidation and then subsequentlyheat treated under N₂ atmosphere. Effect of the treatments on the carbon surface chemicalproperties, pore structure characteristics and adsorption of nitrobenzene from aqueous solutionswere investigated. N₂/77K adsorption isotherm and SEM were used to characterize the porestructure and surface morphology. Boehm titration, F-FIR, the point of zero charge (pH_pzc)measurement and elemental analysis were used to characterize the surface properties. The results reveal that HNO₃ oxidation can modify the surface chemical properties and increase thenumber of surface oxygen containing acid groups. Further heat treatment can cause thedecompose of the surface oxygen containing acid groups; increase the external surface area andthe number of mesopores. Adsorption capacity of nitrobenzene on AC_NO-T,AC_raw and AC_NOwas 1011.31, 483.09 and 321.54 mg/g, respectively. Larger external surface area and thenumber of meso-pores, together with the less surface oxygen containing acid groups were themain reason of larger adsorption capacity AC_NO-T.