Zhihuan Zhao

Solvothermal synthesis of different phase N-TiO2 and their kinetics, isotherm and thermodynamic studies on the adsorption of methyl orange.

The different crystal forms of nitrogen doped-titanium oxide (N-TiO2) with different particle sizes were produced by precipitation-solvothermal method and their adsorption mechanism were also investigated. The adsorption kinetics showed that rutile N-TiO2 displayed higher adsorption capacity than anatase for methyl orange (MO) and its adsorption behavior followed the pseudo-second-order kinetics. The equilibrium adsorption rate of N-TiO2 for MO was well fitted by the Langmuir isotherm model and the adsorption process was monolayer adsorption. The adsorption capacity decreased with increasing temperature. The average correlation coefficient was beyond 97%. The thermodynamic parameters (ΔaGm(ө), ΔaHm(ө), and ΔaSm(ө)) were calculated. It was found that anatase and rutile N-TiO2 had different adsorption enthalpy and entropy. The smaller the particle size, the greater the surface area and surface energy was, then ΔaGm(ө) decreased and the standard equilibrium constant increased at the same time. The adsorption process onto different crystalline phase N-TiO2 was exothermic and non-spontaneous.

Persistent Methyl Orange Degradation Ability of MgAl2O4:(Pr3+,Dy3+)/M-TiO2 Luminescent Photocatalyst

Metal ions (Cr, Ni, Co) doped titania (M-TiO2) coupled with the long after glow phosphor MgAl2O4:(Pr3+, Dy3+) particles were synthesized by the sol-gel method, with the best mass ratio of MgAl2O4:(Pr3+, Dy3+) to M-TiO2 as 4:6. MgAl2O4:(Pr3+, Dy3+)/M-TiO2 had the persistent methyl orange (MO) photocatalytic degradation ability and the photocatalytic degradation went on reacting more than 90 min in dark after turning off the light. MgAl2O4:(Pr3+, Dy3+) emitted the light as a light source in dark which was absorbed by M-TiO2. The differences of MgAl2O4:(Pr3+, Dy3+)/Cr-TiO2, MgAl2O4:(Pr3+, Dy3+)/Ni-TiO2 and MgAl2O4:(Pr3+, Dy3+)/Co-TiO2 might be attributed to the difference in the metal ions doping. The composite MgAl2O4:(Pr3+, Dy3+)/Cr-TiO2 revealed the highest ability of persistent photocatalytic degradation methyl orange. Different metal ions doping made the TiO2 with different band gap.

Synthesis of TiO2/Fly Ash Cenospheres by Sol–Gel Method and Their Photacatalytic Activities Under Visible Light

Fly ash is a solid waste discharged from thermal power plant. Specific surface area of floating fly ash cenospheres (FACs) would increase after it was modified. The photocatalytic composite of TiO2/FACs was successfully synthesized by sol-gel method using the carrier of modified FACs and tetrabutyl titanate as starting materials. The different influence factors on the photocatalytic performance of TiO2/FACs composites were characterized through SEM, EDS, XRD, UV-vis DRS and BET surface measurements. The UV-vis DRS spectra revealed that the absorption edge of TiO2 is 387 nm while that of TiO2/FACs photocatalysts red-shifts to 500 nm. Photocatalytic activity of TiO2/FACs was evaluated by the photocatalytic depigmentation of methyl orange solution (MO, 20 mg L-1, pH = 6.3) under visible light irradiation. It was found that the specific surface area, surface roughness and activity of FACs were increased by NaOH solution activation. The degradation rate of MO reaches 52% in 180 min under the visible light illumination. But too much FACs could decrease its photocatalytic activity and degradation rate. And the recovery test indicated that TiO2/FACs photocatalyst was rather stable, easy to recover from the treated wastewater.