Ionic liquid/TiO(2) nanoparticles doped with non-expensive metals: new active catalyst for phenol photodegradation

TiO(2) nanoparticles were synthesized using 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI·BF(4)) ionic liquid and doped with non-expensive metals Cu(2+) and Fe(3+) by the sol–gel method. The new generated photocatalysts had their morphological, textural and structural characteristics analysed by scanning electron microscopy and dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller analysis (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS). The results showed two phases by XRD analysis, anatase (majority) and rutile (minority). The SEM micrographs exposed spherical TiO(2) NPs/BMI·BF(4) IL and compact layers for Cu(2+) and Fe(3+)-doped TiO(2) NPs in BMI·BF(4) IL, the EDX confirmed only the presence of Ti, O, Fe and Cu. The BET and BJH analyses exhibited high porous TiO(2) NPs/BMI·BF(4) IL. The BET and BJH analyses confirmed that the pore diameter of mesoporous materials was between 12 and 16 nm with similar values for surface area (55–63 m(2) g(−1)). The TEM images exhibited spherical shape nanoparticles with mean diameter of 20–22 nm. The DRS analysis and Tauc equation were applied to estimate the optical energy band gap of the photocatalysts. The energy band gap values of 3.1 eV, 3.32 eV, and 2.78 eV were obtained for TiO(2) NPs/BMI·BF(4) IL, 1% Fe(3+)-doped TiO(2) NPs/BMI·BF(4) IL and 1% Cu(2+)-doped TiO(2) NPs/BMI·BF(4) IL, respectively. Phenol photodegradation was realized using Cu(2+) and Fe(3+)-doped TiO(2) NPs/BMI·BF(4) IL under UV/visible irradiation and quantified by HPLC-FLD. The phenol photodegradation was investigated by different concentrations of metal-doped TiO(2) NPs/BMI·BF(4) IL. The new active photocatalysts 1% Cu(2+)-doped TiO(2) NPs and 1% Fe(3+)-doped TiO(2) NPs/BMI·BF(4) IL exhibited high catalytic activity (99.9% and 96.8%, respectively). The photocatalysts 1% Cu(2+) and 1% Fe(3+)-doped TiO(2) NPs/BMI·BF(4) IL were also evaluated using industrial wastewater from the tobacco industry. The results showed 56.7% phenol photodegradation, due to the complexity of the tobacco matrix wastewater.