Jacek Przepiórski

Cellulose-TiO2 nanocomposite with enhanced UV–Vis light absorption

TiO2/N-cellulose nanocomposite was successfully prepared in the (cyclohexyl)hexyl-dimethylammonium acetate–dimethyl sulfoxide solution. The obtained composite was characterized with various techniques like UV–Vis/DR, FTIR/DRS, X-ray diffraction, thermogravimetric analysis, DLS method and BET SSA measurements. TiO2/N-cellulose nanocomposite exhibited high UV–Vis light absorption with energy gap shifted to the visible region. Additive of TiO2/N photocatalyst to cellulose-IL-DMSO solution leads to obtaining the material with higher thermostability and limited photoactivity.

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.

Porous carbon material containing CaO for acidic gas capture: Preparation and properties

A one-step process for the preparation of CaO-containing porous carbons is described. Mixtures of poly(ethylene terephthalate) with natural limestone were pyrolyzed and thus hybrid sorbents could be easily obtained. The polymeric material and the mineral served as a carbon precursor and CaO delivering agent, respectively. We discuss effects of the preparation conditions and the relative amounts of the raw materials used for the preparations on the porosity of the hybrid products. The micropore areas and volumes of the obtained products tended to decrease with increasing CaO contents. Increase in the preparation temperature entailed a decrease in the micropore volume, whereas the mesopore volume increased. The pore creation mechanism is proposed on the basis of thermogravimetric and temperature-programmed desorption measurements. The prepared CaO-containing porous carbons efficiently captured SO2 and CO2 from air. Washing out of CaO from the hybrid materials was confirmed as a suitable method to obtain highly porous carbon materials.

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.

The effect of chemical activation method on properties of activated carbons obtained from pine cones

A method for obtaining carbonaceous adsorbents from pine cones by chemical activation with NaOH is described. Activated carbons were obtained by two methods of activation (physical mixing and impregnation) and two variants of thermal treatment. It has been shown that pine cones can be successfully used as cheap precursor of carbonaceous adsorbents of well-developed surface area, large pore volume and good sorption properties. All activated carbon samples obtained show strongly microporous structure and surface of acidic character. The best physicochemical properties and greatest sorption capacity towards iodine were found for the carbon samples obtained by physical mixing of the precursor with the activating agent and then subjected to thermal activation at 600°C.

Preparation and properties of porous carbon material containing magnesium oxide

Preparation and properties of porous carbon material containing magnesium oxide Porous carbons loaded with magnesium oxide were prepared through one-step process. Poly(ethylene terephthalate) and natural magnesite were used as carbon source and MgO precursor, respectively. An impact of a temperature and relative amounts of raw components used for preparations on the textural parameters of resulting hybrid materials is presented and discussed. As found, pore structure parameters tend to decrease along with MgO loading and temperature used during preparation process. Micropore area is the parameter being reduced primarily.

Eco-Friendly Catalytic Systems Based on Carbon-Supported Magnesium Oxide Materials for the Friedländer Condensation

Carbon‐supported MgO materials are excellent and sustainable catalysts for the synthesis of N‐containing heterocyclic compounds by the Friedländer condensation under mild, solvent‐free conditions. The results reported herein indicate that MgO is the most active catalytic species that accelerates the reaction compared with the catalytic behavior observed for the carbon material Norit RX3. On the basis of DFT calculations, a reaction mechanism that involves dual activation of the reacting structures by the catalyst is proposed.

TiO2 Supported on Quartz Wool for Photocatalytic Oxidation of Hydrogen Sulphide

A spacial system consisting of TiO2 on a fibrous support was prepared by hydrolysis of titanium isopropoxide in the presence of quartz wool, followed by calcination. The material was characterized by X-ray diffraction, nitrogen adsorption–desorption at 77 K, X-ray photoelectron spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The TiO2/support system was examined as a photocatalyst for UV-assisted oxidation of H2S in air. The results obtained confirmed a superior performance of the TiO2/support system over TiO2 powder. H2S underwent oxidation to elemental sulphur and/or S6+. The relative amounts of these species were influenced by humidity.

Preparation and characterization of titania powders obtained via hydrolysis of titanium tetraisopropoxide

TiO2 powders were prepared through the hydrolysis of titanium isopropoxide followed by calcination at temperatures of 200 °C to 600 °C. The obtained powders were characterized by N2 adsorption-desorption and X-ray powder diffraction. The results confirmed strong dependence between specific surface area of the TiO2 powders and both the conditions of the hydrolysis process and the calcination temperature. While calcination temperature strongly affected crystallinity of the product, no significant influence of the hydrolysis conditions on this parameter was observed. TiO2 powders prepared at various conditions were examined as catalysts for photodegradation of Acid Red 18 in water. Photoactivities of the prepared powders were influenced by both the amount of water used to hydrolyze the TiO2 precursor and the temperature of calcination process. TiO2 samples calcined at 500 °C appeared to be the most active and the photocatalytic activities of the prepared materials increased along with the amount of water used for the hydrolysis process.