Sylwia Mozia

Decomposition of 3-chlorophenol on nitrogen modified TiO2 photocatalysts.

Photocatalytic activity of nitrogen modified TiO(2) calcined at temperatures of 100-350°C toward 3-chlorophenol (3-CP) degradation was studied. In the experiments the fluorescent UV lamp and the incandescent lamp emitting mainly Vis light were applied. The degradation efficiency was evaluated on a basis of changes of 3-CP, total organic carbon and Cl(-) concentration. A significant improvement of the photoactivity of the N-modified photocatalysts compared to the reference sample was observed. The rate of 3-CP degradation increased with the calcination temperature, and the highest efficiency was achieved for TiO(2) annealed at 350°C. After 5h of UV irradiation in the presence of TiO(2)/N-350 and reference TiO(2) the 3-CP concentration decreased for 77% and 36%, respectively. The 3-CP removal after 24h of Vis irradiation was 30% and 12% for the N-modified and reference samples, respectively. The 3-CP decomposition and mineralization were greatly influenced by pH of the solution, achieving the highest rate at pH 7 for the modified photocatalysts. An increase of the calcination temperature resulted in an increase of the rate of OH formation. The photocatalytic activity of the N-modified TiO(2) remained unchanged during repeated photocatalytic degradation cycles.

Immobilized TiO 2 for phenol degradation in a pilot-scale photocatalytic reactor

Phenol degradation was carried out in a photocatalytic pilot plant reactor equipped with a UV/vis mercury lamp. The total volume of treated water was equal to 1.35m3. TiO2 P25 was used as a photocatalyst and it was immobilized on two different supports: (i) a steel mesh and (ii) a fiberglass cloth. Moreover, the performance of commercially available Photospheres-40 was examined. In addition, an experiment in the absence of a photocatalyst was conducted. The commercially available Photospheres-40 were found to be inadequate for the presented application due to their fragility, which in connection with vigorousmixing and pumping led to their mechanical destruction and loss of floating abilities. The highest effectiveness of phenol decomposition and mineralization was observed in the presence of TiO2 supported on the fiberglass cloth. After 15 h of the process, phenol and total organic carbon concentrations decreased by ca. 80% and 50%, respectively.

Evaluation of Performance of Hybrid Photolysis-DCMD and Photocatalysis-DCMD Systems Utilizing UV-C Radiation for Removal of Diclofenac Sodium Salt From Water

The removal of a non-steroidal anti-inflammatory drug (NSAID) diclofenac sodium salt (DCF, C14H10Cl2NNaO2) from water in two hybrid systems coupling photolysis or photocatalysis with direct contact membrane distillation (DCMD) is presented. A UV-C germicidal lamp was used as a source of irradiation. The initial concentration of DCF was in the range of 0.005-0.15 mmol/dm3 and the TiO2 Aeroxide® P25 loading (hybrid photocatalysis-DCMD) ranged from 0.05 to 0.4 g/dm3. Regardless of the applied hybrid system and the initial concentration of DCF, the model drug was completely decomposed within 4h of irradiation or less. Mineralization was less efficient than photodecomposition. In case of the hybrid photolysis-DCMD process the efficiency of TOC degradation after 5h of irradiation ranged from 27.3-48.7% depending on the DCF initial concentration. The addition of TiO2 allowed to improve the efficiency of TOC removal. The highest degradation rate was obtained at 0.3 gTiO2/dm3. During the process conducted with the lowest DCF initial concentrations (0.005-0.025 mmol/dm3) a complete mineralization was obtained. However, when higher initial amounts of DCF were used (0.05-0.15 mmol/dm3), the efficiency of TOC degradation was in the range of 82.5-85%. The quality of distillate was high regardless of the system: DCF was not detected, TOC concentration did not exceeded 0.7 mg/dm3 (1.9 mg/dm3 in permeate) and conductivity was lower than 1.6 μS/cm.

Integration of Photocatalysis with Ultrafiltration or Membrane Distillation for Removal of Azo Dye Direct Green 99 from Water

Abstract An application of hybrid processes photocatalysis - ultrafiltration (UF) and photocatalysis - direct contact membrane distillation (DCMD, MD) for removal of azo-dye Direct Green 99 from water is presented. Titanium dioxide Aeroxide® P25 (Degussa, Germany) was used as a photocatalyst. It was found that both membrane processes were effective in separation of TiO2 particles from the reaction solution. However, during UF a significant flux decline (from 5.2 m3/m2d to about 3.7 m3/m2d at 0.5 gTiO2/dm3) due to the membrane fouling caused by TiO2 particles was observed. Moreover, the products and by-products of photodegradation of model azo-dye passed completely through the UF membrane. The results obtained during hybrid photocatalysis - MD processes were much more promising. The permeate flux remained constant (0.35 m3/m2d) during the experiments and was equal to the flux measured for distilled water applied as a feed. After 5 h of the processes performance the model dye was removed completely, whereas TOC concentration in permeate did not exceed the value of 1.5 gC/dm3.

Formation of Combustible Hydrocarbons and H2 during Photocatalytic Decomposition of Various Organic Compounds under Aerated and Deaerated Conditions

A possibility of photocatalytic production of useful aliphatic hydrocarbons and H2 from various organic compounds, including acetic acid, methanol, ethanol and glucose, over Fe-modified TiO2 is discussed. In particular, the influence of the reaction atmosphere (N2, air) was investigated. Different gases were identified in the headspace volume of the reactor depending on the substrate. In general, the evolution of the gases was more effective in air compared to a N2 atmosphere. In the presence of air, the gaseous phase contained CO2, CH4 and H2, regardless of the substrate used. Moreover, formation of C2H6 and C3H8 in the case of acetic acid and C2H6 in the case of ethanol was observed. In case of acetic acid and methanol an increase in H2 evolution under aerated conditions was observed. It was concluded that the photocatalytic decomposition of organic compounds with simultaneous generation of combustible hydrocarbons and hydrogen could be a promising method of “green energy” production.

Adsorption of humic acid on mesoporous carbons prepared from poly- (ethylene terephthalate) templated with magnesium compounds

Abstract Porous carbons obtained from poly(ethylene terephtalate) contained in a mixture with either MgCO3 or Mg(OH)2 were examined as adsorbents for removal of humic acid from water. Adsorption of the model contaminants is discussed in relation to the textural parameters of the obtained carbon materials. Pore structure parameters of the carbonaceous materials were strongly influenced by preparation conditions including temperature and relative amounts of the inorganics used during preparations as template. Porous carbons prepared revealed a potential to purify water from the model contaminant of high molecular weight. The results presented confirmed a key role of mesoporosity in the adsorption of humic acid. Fluorescence spectroscopy was confirmed to be an useful method to evaluate concentration of humic acid in water.

Degradation of Ibuprofen Sodium Salt in a Hybrid Photolysis – Membrane Distillation System Utilizing Germicidal UVC Lamp

Abstract The present paper describes photodegradation of non-steroidal anti-inflammatory drug ibuprofen sodium salt (C13H17O2Na) in a new hybrid system coupling photolysis and direct contact membrane distillation (DCMD). Photodegradation was conducted using UV254 germicidal lamp. The initial concentration of C13H17O2Na was c0= 0.05, 0.1, 0.2 or 0.4 mmol/dm3. After 5 h of the process the mass of C13H17O2Na in the feed decreased for 99.8-96.7% for c0 of 0.05-0.4 mmol/dm3, respectively. The amount of total organic carbon (TOC) in the feed was lowered by ca. 75%, regardless of initial C13H17O2Na concentration. Among the volatile compounds which passed through the membrane low amounts of C13H18O2 (0.04-0.16 μmol) and some other organic compounds measured as TOC (1.2-3.7 mg) were present. The conductivity of distillate did not exceed the value of 2.6 μS/cm and pH was about 5.7. The total effectiveness of organics removal was 99.97-99.99% for C13H18O2 and 94.8- 98.0% for TOC, dependent on initial concentration of ibuprofen sodium salt.

Magnetic resonance study of co-modified (Co,N)-TiO2 nanocomposites

Abstract Three nCo,N-TiO2 nanocomposites (where cobalt concentration index n = 1, 5 and 10 wt %) were prepared and investigated by magnetic resonance spectroscopy at room temperature. Ferromagnetic resonance (FMR) lines of magnetic cobalt agglomerated nanoparticle were dominant in all registered spectra. The relaxation processes and magnetic anisotropy of the investigated spin system essentially depended on the concentration of cobalt ions. It is suggested that the samples contained two magnetic types of sublattices forming a strongly correlated spin system. It is suggested that the existence of strongly correlated magnetic system has an essential influence of the photocatalytic properties of the studied nanocomposites.

Magnetic Resonance Study of Nickel and Nitrogen Co-modified Titanium Dioxide Nanocomposites

Nickel and nitrogen co-modified TiO2, nNi,N-TiO2 (n = 1, 5 and 10 wt% of Ni) nanocomposites were prepared by impregnation of amorphous titanium dioxide with Ni(NO\(_{3})_{2}\cdot \) 5H2O followed by high temperature calcination at 800 ∘C in ammonia atmosphere. Temperature dependence of the FMR/EPR spectra of nNi,N-TiO2 samples in 4–290 K range has been investigated. The FMR spectra of nickel nanoparticle agglomerates were studied by decomposition into three components. Temperature dependence of FMR parameters (resonance field, two types of linewidth, integrated intensity) of components were analyzed to determine their origin. In addition, the EPR spectra of trivalent titanium ions were recorded in the low temperature range. The connection between photocatalytic activity of the investigated nanocomposites and their magnetic properties was discussed.

Magnetic properties of co-modified Fe,N-TiO 2 nanocomposites

Abstract Iron and nitrogen co-modified titanium dioxide nanocomposites, nFe,N-TiO2 (where n = 1, 5 and 10 wt% of Fe), were investigated by detailed dc susceptibility and magnetization measurements. Different kinds of magnetic interactions were evidenced depending essentially on iron loading of TiO2. The coexistence of superparamagnetic, paramagnetic and ferromagnetic phases was identified at high temperatures. Strong antiferromagnetic interactions were observed below 50 K, where some part of the nanocomposite entered into a long range antiferromagnetic ordering. Antiferromagnetic interactions were attributed to the magnetic agglomerates of iron-based and trivalent iron ions in FeTiO3 phase,whereas ferromagnetic interactions stemmed from the F-center mediated bound magnetic polarons.