Cerium and europium doped TiO2 thin films deposited by a sol-gel dip-coating process: characterization and photocatalytic activity toward dye degradation.

Cerium (Ce) and europium (Eu)-doped TiO2 thin films were obtained by sol-gel dip-coating technique. SEM micrographs showed that the surfaces are covered by agglomerated particles due to the repeating coating process. XRD patterns showed the presence of TiO2 anatase phase. Raman spectra revealed that the peaks recorded at 146 cm-1(Eg) and 397 cm-1(B1g) were related to the anatase phase. EIS measurements proved that Ce-TiO2 (1wt%) and Eu-TiO2 (0.1wt%) photocatalysts possessed a lower electron transfer resistance than pure TiO2, which can lead to effective separation of electron/ hole pairs during the photoreactions. The photoactivity of Ce and Eu-doped TiO2 was investigated by the degradation of amido black10B dye (AB) under UV excitation and varying the initial pH and concentrations. It was found that Eu-TiO2 (0.1wt%) exhibited higher photocatalytic activity, reaching a first-order reaction rate of kapp (0.036min-1), t1/2 was around 12 min and AB removal was 98.94%, under optimal pH of 3.5 and AB concentration of 10ppm compared to (t1/2= 45 min, t1/2=30 min), (kapp= 0.022 min-1, kapp=0.026min-1) and AB removal (94.78%, 96.44%), respectively for pure TiO2 and Ce-TiO2 (1wt%). Further increase in Eu/Ce amount up to optimal concentration (1wt% Ce and 0.1wt% Eu) led to a decrease in the AB removal. The mineralization of AB using Eu-TiO2 photocatalyst was confirmed by HPLC analysis.

A comparative study on ozone, hydrogen peroxide and UV based advanced oxidation processes for efficient removal of diethyl phthalate in water.

Several Advanced Oxidation Processes (AOPs) including O3/H2O2, O3/TiO2, O3/activated carbon (AC), O3/Al2O3, O3/Fe2+/H2O2 and UV/TiO2 have been investigated and compared for the removal of diethyl phthalate (DEP), an endocrine disrupting compound, in aqueous solutions. Hydroxyl radicals were the main species responsible for DEP degradation and this was supported by computational chemistry calculation, scavenger experiments, and LC/MS/MS analysis. The change of the abundance of reaction products over time was determined. Organic acids as well as anhydride and hydroxylated products were found to accumulate in solution even after long reaction time (2 h). Careful choice of the operating parameters (pH, ozone concentration and catalyst dosage) was crucial to achieve enhanced performance of the combined processes above what each oxidant and catalyst can achieve alone. O3/AC process was found to reduce the oxidation efficiency of O3 at high ozone concentrations. Heterogeneous catalytic ozonation with Al2O3 was the most effective process for DEP removal (∼100% removal in about 15 min) and based on pseudo-first-order kinetics at pH7, the studied oxidation processes followed the order: O3/Al2O3(0.093 min-1)>O3/H2O2/Fe2+(0.076 min-1)>O3/AC(0.069 min-1)>O3/H2O2(0.053 min-1)>O3/TiO2(0.050 min-1)> O3 alone (0.039 min-1)>UV/TiO2(0.009 min-1).

Catalysed ozonation for removal of an endocrine-disrupting compound using the O3/Fenton reagents system.

Aqueous solutions of diethyl phthalate (DEP) were oxidized by using ozone combined with Fenton reagents. The effects of operating parameters such as initial pH; initial concentration of DEP, H2O2 and Fe2+; [H2O2]0/[Fe2+]0 ratio and O3 dosage on the degradation rates of DEP were investigated. The results showed that DEP degradation is strongly dependant on the pH; initial concentrations of the phthalate, H2O2 and Fe2+; [H2O2]0/[Fe2+]0 ratio and O3 dosage. The addition of H2O2 and Fe2+ ions was effective to achieve almost 98% degradation of 200 mg L(-1) of DEP in about 40 min using a dose of O3=45 g m(-3) NTP; [H2O2]0=2.5×10(-2) mol L(-1) and [Fe(II)]0=5×10(-3) mol L(-1), as compared to over 60 min by using O3 and Fenton processes applied separately. DEP degradation followed apparent pseudo-first-order kinetics under ozonation, Fenton's reagents oxidation and the combined ozonation/Fenton reagents oxidation process. The overall reaction rates were significantly enhanced in the O3/Fe2+/H2O2 oxidation system, and allows achieving 100% degradation of DEP (100 mg L(-1)) in 30 min of reaction time. The notable decrease in DEP removal rate observed in the presence of a radical scavenger indicates that there was an obvious synergetic effect in the combined ozonation/Fenton reagent process most likely because ozonation could accelerate Fenton reagents to generate hydroxyl radical HO•. Thus, the reaction between DEP and HO• proceeds mainly in the bulk of the aqueous phase. Under optimal conditions, the O3/Fe2+/H2O2 system oxidation was the most effective in DEP removal in water.