Bożena Czech

Photocatalytic treatment of pharmaceutical wastewater using new multiwall-carbon nanotubes/TiO2/SiO2 nanocomposites

For the photocatalytic removal of bisphenol A (BPA) and carbamazepine (CBZ) from water solution a new multiwall-carbon nanotubes and TiO2/SiO2 nanocomposites (MWCNT-TiO2-SiO2) were applied. Nanocomposites with the addition of 0.15-17.8 wt% MWCNT show high potential for the removal of both pollutants. The starting concentration of each contaminant was halved during 20 min of UVA irradiation. The decomposition process of CBZ over investigated nanocomposites proceeded differently than it was observed for the classical photocatalyst P25. The kinetics of the removal followed as a pseudo-first order regime with the k1 in range 0.0827-0.1751 min(-1) for BPA and 0.0131-0.0743 min(-1) for CBZ. Toxicity to Vibrio fischeri and Daphnia magna was significantly reduced indicating formation of non-toxic products of photooxidation of tested contaminants.

Ecotoxicological evaluation of selected pharmaceuticals to Vibrio fischeri and Daphnia magna before and after photooxidation process.

The aim of the research was the determination of the toxicity of photocatalytically treated water contaminated by different pharmaceuticals: chloramphenicol (CPL), diclofenac (DCF) or metoprolol (MT). Daphtoxkit F™ with Dapnia magna and Microtox(®) with Vibrio fischeri were used to evaluate the toxicity of the water before and after treatment. D. magna showed higher sensitivity to the presence of pharmaceuticals than V. fischeri. Generally, both tested organisms revealed the greatest sensitivity to the presence of CPL. The application of photocatalytic oxidation has resulted in decreased toxicity. It may confirm the reduction of high toxic parent compounds to less toxic metabolites. The toxicity was reduced in the range from 30% to 100% depending on pharmaceutical tested. The highest reduction of toxicity to V. fischeri and D. magna was observed to MT and CPL respectively. Depending on bioassay the toxicity decrease as follows: CPL>DCF>MT for D. magna and CPL>MT>DCF for V. fischeri.

Preparation and characterization of C,N-codoped TiO2 photocatalyst for the degradation of diclofenac from wastewater

Application of mesoporous C- and C,N-codoped TiO2 in the removal of diclofenac from water was studied. The sol-gel method was used for the preparation of the photocatalysts. The physicochemical properties of studied materials were characterized by BET (Brunauer, Emmett and Teller), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and X-ray diffraction (XRD) methods. XPS confirmed the incorporation of nitrogen and carbon atoms into TiO2 lattice. The synthesized catalysts were effective in the removal of the studied pollutant from water and enabled reduction of the COD (chemical oxygen demand) value of the wastewater by at least 60%. The process of diclofenac photooxidation over the C,N-codoped and C-doped TiO2 photocatalysts proceeded similarly and was followed by pseudo-first order kinetics. The increase in calcination temperature resulted in the rutile fraction (5%) slightly lowering the effectiveness of treatment. The results over pure anatase structures confirmed that anatase has usually a better photocatalytic activity than rutile. The best changes in the water quality were observed during the first 50 min of treatment, but mineralization of pollutant did not lead to complete.

Advanced oxidation (H2O2 and/or UV) of functionalized carbon nanotubes (CNT-OH and CNT-COOH) and its influence on the stabilization of CNTs in water and tannic acid solution

The properties of carbon nanotubes (CNTs) functionalized with -OH and -COOH groups during simulated water treatment with H2O2 and/or UV were tested. There following properties of CNTs were investigated: specific surface area, elemental composition (CHN), dynamic light scattering, Raman spectroscopy, X-ray photoelectron spectroscopy and changes in the CNTs structure were observed using transmission electron microscopy. Treatment of CNTs with H2O2 and/or UV affected their properties. This effect, however, was different depending on the functionalization of CNTs and also on the factor used (UV and/or H2O2). H2O2 plays a key role as a factor modifying the surface of CNT-OHs, whereas the properties of CNT-COOHs were most affected by UV rays. A shortening of the nanotubes, exfoliation, the opening of their ends, and changes in the surface charge were observed as a result of the action of UV and/or H2O2. The changes in observed parameters may influence the stability of the aqueous suspensions of CNTs.

Sorption of diclofenac and naproxen onto MWCNT in model wastewater treated by H2O2 and/or UV.

The application of oxidation processes such as UV and/or H2O2 will change the physicochemical properties of carbon nanotubes (CNT). It may affect the sorption affinity of CNT to different contaminants and then affect their fate in the environment. In the present study the adsorption of two very common used pharmaceuticals (diclofenac and naproxen) onto CNT treated by UV, H2O2 or UV/H2O2 was investigated. Four different adsorption models (Freundlich, Langmuir, Temkin, Dubinin-Radushkevich) were tested. The best fitting of experimental data was observed for Freundlich or Langmuir model. The significant relationships between Q calculated from Langmuir model with O% and dispersity were observed. Kinetics of diclofenac and naproxen followed mainly pseudo-second order indicating for chemisorption limiting step of adsorption. The data showed that the mechanism of sorption was physical or chemical depending on the type of CNT modification.

Water treatment by H2O2 and/or UV affects carbon nanotube (CNT) properties and fate in water and tannic acid solution

The objective of the study was to estimate how water treatment (stimulation of real conditions) by H2O2 and/or UV affects carbon nanotube (CNT) properties and fate (stability/aggregation) in water and tannic acid solution. The processes studied had only a slight effect on SBET, porosity, and surface composition of CNTs. There was a change in the morphology of CNTs. After H2O2 and/or UV treatment, CNTs underwent shortening, opening up of their ends, and exfoliation. Treatment with H2O2 increased the content of oxygen in CNTs. A decrease was observed in the surface charge and in the mobility of CNTs, which caused an increase in their stability. UV irradiation of CNTs led to an increased incidence of defects that were manifested by both an increase of zeta potential and an increased mobility of CNT, whereas the presence of H2O2 during UV irradiation had only a slight effect on the parameters of the porous structure of nanotubes.

Band reactor for toxic and recalcitrant water contaminants

Band reactor for toxic and recalcitrant water contaminants This paper deals with the problem of the photocatalytic reactor construction. The supported TiO2 on γ- Al2O3 modified with Mo or V addition was used as the photocatalyst, whereas phenol and formaldehyde were chosen as the model pollutants. The counter - current contact of reagents and catalysts is the main advantage of the construction and enables a significant COD reduction of the highly concentrated wastewaters.

The interactions of UV and/or H2O2 treated CNTOH and CNTCOOH with environmental fulvic acids

The fate of carbon nanotubes (CNT) in the environment will be governed by the presence of natural dissolved organic matter (DOM). Many studies indicate that CNT create stabilized suspensions in the presence of DOM. Easier transport in the environment may indicate their greater hazard. However these studies describe the interactions of DOM with as produced CNT. In the present studies the interactions of UV and/or H2O2 treated wastewater containing CNTOH or CNTCOOH with the naturally occurred fulvic acids (FA) were presented. FA sorption, both kinetics and mechanism, were described using batch regime. The sorption of FA followed a pseudo-second order kinetics and was described with the highest accuracy by Langmuir or Dubinin-Radushkevich model for CNTOHs and Langmuir, Temkin or Dubinin-Radushkevich - for CNTCOOHs. The mechanism of FA sorption onto CNTOHs was ascribed to π-π, heterogeneous and electrostatic interactions. The π-π and electrostatic interactions can the mostly defined FA adsorption onto CNTCOOHs. The parameters affecting FA sorption were combination of porosity and dispersity.

Development simple and sensitive voltammetric procedure for ultra-trace determination of U(VI)

A simple and sensitive adsorptive stripping voltammetric procedure for the determination of trace concentration of U(VI) in natural water samples was developed. In order to remove surface active compounds from water sample solutions, a TiO2/Al2O3 photocatalysis system was applied. The linear calibration graph of U(VI) in the simultaneous presence of 2mgL-1 anionic, cationic and nonionic surfactants, in the range from 5×10-10 to 2×10-8molL-1 (180s) was achieved. The detection limit obtained in the solution after the use of UV-irradiation (10min) with TiO2/Al2O3 photocatalyst (0.9g) is equal to 2.3×10-10mol L-1. The presented procedure was successfully applied to uranium determination in SLEW-3 certified reference material, and to river water samples. In addition, a very low detection limit (2.9×10-11molL-1) for accumulation time of 180s was achieved due to application of a reversible deposited mediator (Zn) in the step of lead film electrode preparation.