Marta Gmurek

Photocatalytic ozonation using doped TiO2 catalysts for the removal of parabens in water

Conventional wastewater treatments are inefficient for the removal of parabens. The aim of this study was finding a suitable solution using ozone and UVA irradiation combined with TiO2 catalysts doped with different noble metals (Ag, Pt, Pd, Au). Photocatalytic ozonation required lower amounts of ozone for higher efficiency on the removal of parabens, chemical oxygen demand (COD) and total organic carbon (TOC). The best catalyst for the initial contaminants degradation was 0.5% Ag-TiO2 leading to total parabens removal using 46mgO3/L. Due to the relative low mineralization achieved, the toxicity of the treated solutions was still compared with the initial one over several species (Vibrio fischeri, Lepidium sativum and Corbicula fluminea). All the treatments applied led to a clear decrease on the toxicity compared with initial mixture of parabens. From an economical point of view, it was concluded that the presence of UVA irradiation increased the energy consumption compared with catalytic ozonation with these catalysts but it can decrease the time of reaction. From the by-products analysis, it was concluded that hydroxylation appears to be the most significant reaction pathway and the main responsible for parabens degradation.

Phototransformation of sulfamethoxazole under simulated sunlight: Transformation products and their antibacterial activity toward Vibrio fischeri

Sulfamethoxazole (SMX) is a bacteriostatic antibiotic ubiquitously found in the aquatic environment. Since conventional biological wastewater treatment is not efficient to remove SMX, photolysis in natural waters can represent an important transformation pathway. It was recently shown that SMX transformation products can retain antibiotic activity. Therefore, it is crucial to better understand photochemical processes occurring in natural water just as the formation of active transformation products (TPs). During long-term SMX photolysis experiments (one week), nine TPs were identified by reference standards. Moreover, five further TPs of photodecomposition of SMX were found. For the first time, a TP with m/z 271 [M+H](+) was observed during photolysis and tentatively confirmed as 4,x-dihydroxylated SMX. The DOC mass balance clearly showed that only around 5 to 10% were mineralized during the experiment emphasizing the need to elucidate the fate of TPs. Bacterial bioassays confirmed that the mixture retains its antibiotic toxicity toward luminescence (24h) and that there is no change over the treatment time on EC50. In contrast, growth inhibition activity was found to slightly decrease over the irradiation time. However, this decrease was not proportional to the transformation of the parent compound SMX.

Influence of dissolved organic matter in natural and simulated water on the photochemical decomposition of butylparaben.

BackgroundIn the last few decades the quality of natural water has often deteriorated as a variety of novel pollutants have contaminated rivers and lakes. Trace amounts of some man-made chemicals can be hazardous to plants, animals as well as human health as carcinogens, mutagens or endocrine disruptors. Light radiation may help in its decomposition, aided by naturally occurring colored organic compounds (humic substances) in the water. The aim of these studies was to check the influence of presence of organic and inorganic matter on the removal of endocrine disrupting compound - butylparaben (BP) from water.MethodsPhotochemical decomposition of BP in aqueous solution using: photolysis by ultraviolet-C (UVC) and visible (VIS) irradiation, advanced oxidation in H2O2/UV system and photosensitized oxidation was examined. The degradation processes were carried out in different type of water matrix: natural water from Sulejow Reservoir, simulated natural water with humic acids and buffered solution.ResultsThe presence of dissolved organic matter in water did not influence much on UVC photolysis and increases only about 8% of BP depletion rate in H2O2/UV system. While during visible light photolysis and photosensitized oxidation the addition of natural water matrix causes the acceleration of reaction rate by 16% and 36%, respectively. Moreover BP degradation proceeds via singlet oxygen generated from humic substances.ConclusionsButylparaben undergoes both direct and indirect photodegradation in aqueous solution under UVC and visible radiation. The efficiency of the H2O2/UV process, photolysis as well as photosensitized oxidation processes is strongly dependent on composition of the water.

Application of Advanced Oxidation Technologies for Decolorization and Mineralization of Textile Wastewaters

Abstract Reactive dyes are the most abundantly used in textile industry due to their high color fastness, wide color spectrum as well as low energy consumption. The presence of these dyes in effluent released into receiving waters has become a serious environmental problem not only related to their color but mainly because of the hazardous byproducts. An environmentally sustainable development policy in textile industry requires development of new technologies to reduce water consumption as well as negative environmental impact of discharged wastewater. Advanced oxidation processes (AOPs) are the most promising technology for decolorization and mineralization of wastewater contamination. This paper presents the results of ozonation, Fenton’s oxidation and H2O2/UV treatment of simulated as well as industrial textile wastewater containing Reactive Black 5. The AOPs were carried out under varied process parameters such as: dye concentration, pH, oxidant and detergent doses and wide range concentration of NaCl. The decolorization was followed by absorbance while oxidation and mineralization progress by COD and TOC measurements respectively. The almost completely inhibition of decolorization in the presence of NaCl in concentration usually used in industry (60 - 80 g/L) was observed for Fenton reagent. The slight inhibition was observed for H2O2/UV system while for ozonation there was no influence of NaCl on the decolorization. The similar relationship of the influence of anionic detergent concentration was observed. The experiments indicated that ozonation is the best method from TOC and COD removal point of view. For the decolorization of real textile effluents two streams were used 1) containing C.I. Reactive Yellow 145, Red 195, Blue 221 and 2) Reactive Black 5. As a result of the treatment, almost complete decolorization of the wastewater was obtained. Considering both the experimental results and technological problems, it can be presumed that advanced oxidation with a application of ozone or hydrogen peroxide/UV are a very promising techniques for potential industrial implementation, however from economic point of view the more reasonable is the ozonation process.

Removal efficiency of anionic surfactants from water during UVC photolysis and advanced oxidation process in H2O2/UVC system

Abstract Surfactants after their use are discharged into aquatic ecosystems. These compounds may be harmful to fauna and flora in surface waters or can be toxic for microorganisms of the activated sludge or biofilm in WWTP. In order to determine effectiveness of different advanced oxidation processes on the degradation of surfactants, in this study the degradation of anionic surfactants in aqueous solution using photolysis by 254 nm irradiation and by advanced oxidation process in a H2O2/UVC system was investigated. Two representatives of anionic surfactants, linear alkyl benzene sulphonate (LAS-R11–14) and ether carboxylic derivate (EC-R12–14E10) were tested. The influence of pH, initial surfactant concentration and dose of hydrogen peroxide on the degradation was also studied. Results show outstanding effectiveness of the H2O2/UVC system in the removal of surfactant from aqueous solutions.

Decomposition of xenobiotics during visible light irradiation in the presence of immobilised photosensitisers: kinetics study

The objective of this work was to study the photosensitised oxidation of the xenobiotics benzylparaben (BeP) and 2,4dichlorophenol (2,4DCP) in aqueous solutions using photosensitisers immobilised into chitosan carrier particles and visible light radiation. Zn(II) phthalocyanine tetrasulfonate tetrasodium salt and Al(III) phthalocyanine chloride tetrasulfonic acid were used as photosensitisers. The major role of the singlet oxygen during photodegradation was proven by using scavengers of reactive oxygen species. The influence of initial xenobiotic concentration and temperature on degradation rate was examined. The investigations were focused on kinetics (Langmuir-Hinshelwood model) as well as activation energy determination. Moreover, the adsorption isotherms of BeP and 2,4DCP into chitosan carrier were determined using the Brunauer-Emmett-Teller model.

Photodegradation of 2,4-Dichlorophenol in Aqueous Systems under Simulated and Natural Sunlight

The work presents results of studies on 2,4-dichlorophenol (2,4-DCP) degradation in aqueous solutions using photochemically initiated processes by simulated and natural sunlight. A number of possible substrate photodegradation routes were investigated, by both direct photolysis and photosensitized oxidation process. The major role of singlet oxygen in 2,4-DCP photodegradation was proved. Rose Bengal and derivatives of porphine and phthalocyanine were used as sensitizers. The influences of various process parameters on the reaction rate were investigated. On the basis of experimental data reaction rate constants of 2,4-DCP photosensitized oxidation were determined. The possibility of using natural sunlight to degrade 2,4-DCP in water in the middle latitudes was stated. The acute toxicity bioassay was conducted with the marine bacterium Vibrio fischeri as a bioluminescent indicator. The obtained results encourage further research on this process.

Toxicity of aqueous mixture of phenol and chlorophenols upon photosensitized oxidation initiated by sunlight or vis-lamp

It is well established that aquatic wildlife in marine and freshwater of the European Union is exposed to natural and synthetic endocrine disruptor compounds (EDCs) which are able to interfere with the hormonal system causing adverse effects on the intact physiology of organisms. The traditional wastewater treatment processes are inefficient on the removal of EDCs in low concentration. Moreover, not only the efficiency of treatment must be considered but also toxicological aspects. Taking into account all these aspects, the main goal of the study was to investigate the photochemical decomposition of hazardous phenolic compounds under simulated as well as natural sunlight from the toxicity point of view. The studies were focused on photodegradation of 2,4-dichlorophenol as well as mixture of phenol, 2-chlorophenol and 2,4-dichlorophenol. Photosensitized oxidation process was carried out in homogeneous and heterogeneous system. V. fischeri luminescence inhibition was used to determine the changes of toxicity in mixture during simulated and natural irradiation. The photodegradation was carried out in three kinds of water matrix; moreover, the influence of presence of inorganic matter on the treatment process was investigated. The experiments with natural sunlight proved applicability of photosensitive chitosan for visible-light water pollutant degradation. The results of toxicity investigation show that using photosensitive chitosan for visible-light, the toxicity of reaction mixture towards V. fischeri has significantly decreased. The EC50 was found to increase over the irradiation time; this increase was not proportional to the transformation of the parent compounds.

Ozone-Based Technologies for Parabens Removal from Water: Toxicity Assessment

ABSTRACT Ozone was tested for the detoxification of a mixture of five parabens. A combined O3/H2O2 process was optimized leading to up to 50% of COD removal in 15 min, while less than 50 min were needed to achieve total degradation. The toxic effect of the raw mixture and after 15 min of treatment by O3/H2O2 was evaluated using V. fischeri and C. fluminea and it was observed a strong detoxification after 15 min of oxidation. Moreover, while the raw effluent promoted the formation of reactive oxygen species in Wistar rat brain slices, no changes were observed after the O3/H2O2 treatment.