Joanna Kapica-Kozar

Antibacterial properties of TiO2 modified with reduced graphene oxide

In this paper, the antibacterial activity of titanium dioxide modified with reduced graphene oxide (rGO) was presented. TiO2/rGO photocatalysts were prepared by the hydrothermal method under elevated pressure at 180°C and heated at 100°C in Ar flow. The obtained photocatalysts were characterized by means of XRD, FTIR/DRS, UV-vis/DR, Raman spectroscopy and scanning electron microscopy (SEM). The carbon content was also examined. FTIR/DRS and Raman analysis confirmed the presence of rGO in the TiO2 structure, suggesting a successful modification. The antimicrobial photoactivity of photocatalysts was conducted against E. coli under an artificial solar light. The results show that all TiO2/rGO photocatalysts exhibited an antibacterial activity higher than unmodified TiO2. The best result was found for sample with 1.5wt% additive of reduced graphene oxide. In this case, total inactivation of E. coli was noticed after 75min of irradiation. It was found that the presence of rGO in sample improves the antimicrobial activity.

Titanium dioxide modified with various amines used as sorbents of carbon dioxide

In this study, titanium dioxide was modified with various amines through hydrothermal treatment for adsorption of CO2. The carbon dioxide adsorption performance of the prepared samples was measured using an STA 449 C thermobalance (Netzsch Company, Germany). The morphological structures, functional groups and elemental compositions of the unmodified and amine-modified titanium dioxide sorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR/DR) and scanning electron microscopy (SEM), respectively. The results showed that modification of TiO2 with amines through hydrothermal treatment is a simple method to prepare CO2 sorbents with high adsorption capacities. Moreover, the results revealed that TEPA-modified titanium dioxide shoved the highest adsorption capacity, enabling an increase in CO2 uptake from 0.45 mmol CO2 g−1 in the case of raw TiO2 to 1.63 mmol CO2 g−1. This result could be indirectly related to the fact that TEPA has the highest amino group content among the three amines used in our research. Additionally, durability tests performed by cyclic adsorption–desorption revealed that TEPA modified titanium dioxide also possesses excellent stability, despite a slight decrease in adsorption capacity over time.

Preparation and characterisation of TiO2 thermally modified with cyclohexane vapours

In this study a simple method of preparation of UV-vis light-active TiO2 photocatalysts is presented. The new photocatalysts were obtained by thermal modification of the anatase TiO2 powder (Police, Poland) with cyclohexane. The obtained materials were investigated by means of UV-vis/DR, FTIR/DRS, XRD. BET specific surface area and carbon content was also measured. Furthermore, photocatalytic activity of the new photocatalysts were investigated under UV-vis irradiation with high UV light intensity during of phenol degradation. TiO2/C photocatalysts show higher photocatalytic activity in comparison with TiO2-starting and commercial KRONOClean 7000, regardless of calcination temperature. It was found that the smaller amount of carbon in TiO2/C photocatalyst sample the better photocatalytic activity of tested nanomaterials.

The Photocatalytic Performance of Benzene- Modified TiO2 Photocatalysts under UV-vis Light Irradiation

Abstract In this study a photocatalytic performance of new carbon-modified titanium dioxide photocatalysts was discussed. Benzene was used as carbon precursor. It was found that the photocatalytic activity of obtained samples increases with the increase of modification temperature and decrease of carbon concentration present in TiO2/C samples. This could be related to the kind of interactions between TiO2 surface and carbon from thermal decomposition of benzene. The higher calcination temperature the less carbon deposits on the surface of modified samples and the higher probability of the Ti and C interaction confirmed by means of UV-vis/DR studies. It was proved that the photocatalytic activity of carbon modified titania nanomaterials strongly depends on carbon content in TiO2/C photocatalysts. Modification of starting TiO2 with benzene is a promising method especially by taking into account the mineralization of phenol and the co-products of its degradation.

Modification of Titanium Dioxide with Graphitic Carbon from Anthracene Thermal Decomposition as a Promising Method for Visible- Active Photocatalysts Preparation

Abstract This work investigated the photocatalytic performance of TiO2 photocatalysts modified with graphitic carbon under visible light with a very small component of UV. The graphitic carbon modification was conducted at 200-500 °C using thermal anthracene decomposition. The increase of calcination temperature leads to typical increase of crystallites size, decrease of the specific surface area and carbon content in modified samples. The characteristic peak for a skeletal in-plane vibrations of the anthracene ring located at 1522 cm-1 as well as the band at 1410 cm-1 assigned to C=C aromatic stretching vibrations mode were possible to observe. The analysis of the morphology using SEM confirmed the presence on new multi-layer carbonaceous flakes decorated with TiO2 nanoparticles. TEM analysis and Raman studies proved the presence of graphitic structures covering the surface of the prepared TiO2/C photocatalysts. The highest photocatalytic activity, calculated on the basis of phenol photodegradation under visible light, was found for the photocatalyst modified with graphitic carbon at 400 °C (TiO2/C-400).

Adsorption of carbon dioxide on TEPA-modified TiO2/titanate composite nanorods

A titanate–TiO2 composite was obtained through hydrothermal treatment of TiO2 in KOH solution. The presence of a titanate phase was confirmed by X-ray diffraction (XRD), whereas scanning electron microscopy (SEM) measurements showed the porous nanorod structure of the material. The obtained nanorods were treated with tetraethylenepentamine (TEPA). Such synthesized sorbents were applied for CO2 removal. The CO2 capacity under a pressure of 1 bar and at 80 °C was 0.47, 0.34, and 3.11 mmol g−1 for the starting TiO2, the titanate–TiO2 composite and the TEPA–titanate–TiO2 composite (27.4 wt% of TEPA), respectively. The experimental isotherms of CO2 were analysed using the Langmuir, Freundlich, Sips, Toth, Unilan, Redlich–Peterson, Radke–Prausnitz, Dubinin–Radushkevich, Temkin and Pyzhev, and Jovanovich models. The error sums of squares (SSR) function was used to test the fit of the models. The analysis revealed that the Sips isotherm is the best-fitting model for the CO2 adsorption on the starting TiO2, whereas the Freundlich equation should be used to describe the CO2 adsorption isotherm on the titanate–TiO2 composite. The CO2 adsorption on the TEPA-modified sorbents was proposed to be described using the Sips isotherm for physical sorption and the modified Sips model for chemical sorption. The calculated isosteric heat of adsorption was found to be ≈46 kJ mol−1, which is about two times higher than the heat of CO2 absorption in liquid TEPA reported in the literature (i.e. ≈85 kJ mol−1). Therefore, it was concluded that the TEPA–titanate–TiO2 composite is an attractive alternative for liquid amines due to the lower energy of regeneration in the sorption–desorption process. The material was proved to be stable during multiple sorption–desorption cycles. Moreover, its thermal stability up to 150 °C was confirmed by thermogravimetric analysis (TGA). All these features make it a promising alternative for sorbents based on liquid amines.

Impact on CO2 Uptake of MWCNT after Acid Treatment Study

Greenhouse effect is responsible for keeping average temperature of Earth’s atmosphere at level of about 288 K. Its intensification leads to warming of our planet and may contribute to adverse changes in the environment. The most important pollution intensifying greenhouse effect is anthropogenic carbon dioxide. This particular gas absorbs secondary infrared radiation, which in the end leads to an increase of average temperature of Earth’s atmosphere. Main source of CO2 is burning of fossil fuels, like oil, natural gas, and coal. Therefore, to reduce its emission, a special CO2 capture and storage technology is required. Carbonaceous materials are promising materials for CO2 sorbents. Thus multiwalled carbon nanotubes, due to the lack of impurities like ash in activated carbons, were chosen as a model material for investigation of acid treatment impact on CO2 uptake. Remarkable 43% enhancement of CO2 sorption capacity was achieved at 273 K and relative pressure of 0.95. Samples were also thoroughly characterized in terms of texture (specific surface area measurement, transmission electron microscope) and chemical composition (X-ray photoelectron spectroscopy).

Assessment of the Suitability of the One-Step Hydrothermal Method for Preparation of Non-Covalently/Covalently-Bonded TiO2/Graphene-Based Hybrids

A hybrid nanocomposites containing nanocrystalline TiO2 and graphene-related materials (graphene oxide or reduced graphene oxide) were successfully prepared by mechanical mixing and the hydrothermal method in the high-pressure atmosphere. The presented X-ray photoelectron spectroscopy (XPS) study and quantitative elemental analysis confirm similar content of carbon in graphene oxide GO (52 wt% and 46 wt%, respectively) and reduced graphene oxide rGO (92 wt% and 98 wt%, respectively). No chemical interactions between TiO2 and GO/rGO was found. TiO2 nanoparticles were loaded on GO or rGO flakes. However, Fourier transform infrared-diffuse reflection spectroscopy (FTIR/DRS) allowed finding peaks characteristic of GO and rGO. XPS study shows that since the concentration of TiO2 in the samples was no less than 95 wt%, it was assumed that the interactions between TiO2 and graphene should not influence the lower layers of titanium atoms in the TiO2 and they occurred as Ti4+ ions. Hydrothermal treatment at 200 °C did not cause the reduction of GO to rGO in TiO2-GO nanocomposites. In general, the one-step hydrothermal method must be considered to be inefficient for preparation of chemically-bonded composites synthesized from commercially available TiO2 and unfunctionalized graphene sheets obtained from graphite powder.