Band 14, Heft 1

Depending on the process type and raw materials involved, various types of wastewater are discharged from food industry. In the present study the feasibility of Fenton-based treatment, as a part of combined treatment schemes, to degrade high organic content, to eliminate suspended solids, and to improve the overall quality of food-processing plant wastewater was assessed. Fenton oxidation step used in treatment schemes improved significantly the quality of the effluent, enabling additional 62-79% and 53-69% reduction of chemical oxygen demand (COD) and dissolved organic carbon (DOC), respectively, when the H 2 O 2 /COD w/w ratio of 2:1 was used. The results show feasibility of the Fenton oxidation to decrease substantially the organic load and improve the biodegradability of the effluent.

The degradaiton of Acid Orange 7 (AO7) using the plasma-catalytic process, has been stdudied by non-thermal gliding arc technique coupled to P25 titanium dioxide (TiO 2 ). Eperiments were carried out to optimise the amount of photo-catalyst. The results showed that maximum decolorization and degradation were attained 0.5 g 1 −1 TiO 2 concentration. At this optimum concentration, the dye (180 μM) was totally decolorized within 75 min plasma/TiO 2 treatment, and 92.5% removal of initial chemical oxygen demand (COD) was attained after a 125 min plasma/TiO 2 treatment. The extent of degradation decreased with initial concentration and the absolute removal amount increased. In all cases, the plasma-treated samples in the presence or absence of catalyst were found to follow pseudo first-order reaction kinetics. The main intermediates of AO7 degradation were benzenesulfonic acid, hydroquinone, 1,4-benzoquinone, 1,2-naphthoquinone, ring cleavage products (oxalic acid, acetic acid, malonic acid and others). Furthermore, possible pathways of AO7 degradation in solution were proposed.

This study compared bromate formation between ozonation and UV with suspended titanium dioxide (TiO 2 ) oxidation in seawater. It also studied the physical and chemical sustainability of TiO 2 nanoparticles following the oxidation process with UV light. The study was carried out using a collimated beam for UV light and an ozone generator that utilized the corona discharge method. Seawater was used for photocatalysis and ozonation experiments to relate bromate formation to aquaculture applications. Artificial brackish water was used to relate bromate formation to drinking water sources that face seawater intrusion. A key finding from the study was that disinfection by UV-TiO 2 produced a lower concentration of DBPs than disinfection by ozone. In particular, this study found that ozonation produced up to 4.5 mgL -1 of bromate, whereas UV-TiO 2 did not produce bromate at detectable concentrations (<5 μgL -1 ). Bromoform after disinfection by ozone was as high as 148 μgL -1 , but was below the detection limit (<5.9 μgL -1 ) after UV-TiO 2 .

The present paper describes photodegradation of non-steroidal anti-inflammatory drug ibuprofen sodium salt (C 13 H 17 O 2 Na) in a new hybrid system coupling photolysis and direct contact membrane distillation (DCMD). Photodegradation was conducted using UV 254 germicidal lamp. The initial concentration of C 13 H 17 O 2 Na was c 0 = 0.05, 0.1, 0.2 or 0.4 mmol/dm 3 . After 5 h of the process the mass of C 13 H 17 O 2 Na in the feed decreased for 99.8-96.7% for c0 of 0.05-0.4 mmol/dm 3 , respectively. The amount of total organic carbon (TOC) in the feed was lowered by ca. 75%, regardless of initial C 13 H 17 O 2 Na concentration. Among the volatile compounds which passed through the membrane low amounts of C 13 H 18 O 2 (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 C 13 H 18 O 2 and 94.8- 98.0% for TOC, dependent on initial concentration of ibuprofen sodium salt.

The role of titanium dioxide photocatalysis in the frame of green chemistry is discussed on the basis of a review of published life cycle assessments. It appears that the environmental impact of photocatalysis when applied to the mineralization of pollutants is generally worse than that of other advanced oxidation processes when lamps are used, but becomes appealing under solar light. The potential of photocatalysis for organic synthesis - that in principle should minimize the generation of pollutants - is likewise discussed. Here again, however, the method is competitive with thermal procedures only when solar light is used.

Experimental results of electrochemical treatment of acid filtrate effluents from the first ClO 2 stage (D 0 ) of kraft cellulose ECF bleaching are presented here. Real industrial effluents from an eucalyptus based cellulose mill, with no additional supporting electrolytes, were used here. Stainless steel cathode, and graphite, and DSA-Ti/ RuO 2 anodes were tested, at current densities in the range 1-50 A/m 2 . In all cases, COD, AOX, and chloride concentrations decreased with electrochemical treatment, reaching 40-50% removal after 20 min treatment. The rate of COD removal significantly increased at greater pH. Significant active chlorine formation from chloride anodic oxidation was also observed, and no further formation of organic-chlorinated by products was detected. Experiments conducted with p-chlorobenzoic acid show that significant hydroxyl free radicals were generated in all tested anodes, with slightly greater effect in the case of graphite anode. Finally, both mutagenic and genotoxic activity was totally removed by electrochemical treatment, although toxic intermediates were detected within the first 2 min, at high current densities.

This work investigates the efficiency of the Fenton process in removing natural organic matter (NOM) from groundwater. Previous studies focused mostly on the use of Fenton’s process to remove total organic matter, but this research also studies the conditions leading to the formation of hazardous disinfection by-product precursors, and their removal. Solutions of a commercial humic acid as a model of NOM and natural groundwater as a real matrix rich in NOM (dissolved organic carbon, DOC=9.92±0.87 mg/L) were studied. Under optimum reaction conditions, the respective removal efficiencies (expressed as DOC) were 95% from commercial humic acid solution and 82% from groundwater. The decrease in DOC resulted in 99% decrease of the content of precursors of trihalomethanes (THMs) and 98% of haloacetic acids (HAAs) for the investigated matrixes. Precursors of haloacetonitriles, haloketones and chloropicrin were detected at much lower concentrations than the THMs and HAAs precursors.

The light diffraction technique, which we call the “Optical Wave Microphone (OWM)” technique, is an effective sensing method to detect the sound and is flexible for practical uses as it involves only a simple optical lens system. This technique is also very useful to detect the sound wave without disturbing the sound field. Moreover, OWM can be used for sound field visualization by computerized tomography (CT) because the ultrasmall modulation by the sound field is integrated along the laser beam path. The characteristics of the coplanar DBD (Dielectric Barrier Discharge) operated in air is investigated. Applied voltage, current and the electrical discharge sound of coplanar DBD are measured, and examined the relationship between the micro discharge and the acoustic properties. We expect that understanding of acoustic properties gives more details of electric discharges. These are the first experiments to verify the feasibility of the OWM-CT method for the visualization of the sound field of DBD discharge.

A bimolecular kinetic model is proposed for the liquid phase ozonation of organic components, incorporating direct and indirect ozonation by means of bimolecular reaction steps. One of the advantages of this model is that all radicals, present in the liquid phase, are lumped into one concentration, reducing the number of kinetic parameters. The main objective of this paper is to determine the degradation kinetics of ciprofloxacin (CIP), as model component for the class of fluoroquinolones, in order to validate the proposed kinetic model on available experimental data, obtained in a lab scale bubble column reactor. Additionally, different reactor models such as a continuous stirred tank reactor (CSTR) and a plug flow reactor (PFR) are compared in the description of the experimental data. A realistic mass transfer coefficient for ozone from the gas to the liquid phase of 1.65 10 -3 s -1 is obtained and the estimated bimolecular reaction rate coefficients are within the range, described by literature. The calculated responses are in good agreement with the experimental results. Knowledge of both the reaction kinetics and the corresponding reactor model is a promising tool to simulate and optimize ozonation reactor configurations.

The presence of both synthetic and natural steroids in waters is currently one of the most pressing concerns to water treatment utilities. The use of radical-based advanced oxidation/reduction processes (AO/RPs) to augment standard water treatment methods may be of interest. In support of the application of these AO/RP rate constants have been determined for the reaction of the reducing hydrated electron (e aq - ) with three important estrogenic steroids; ethinylestradiol, estradiol and progesterone. Absolute values of (1.46 ± 0.16) x 10 8 , (2.52 ± 0.11) x 10 8 and (8.65 ± 0.15) x 10 9 M -1 s -1 were directly measured for these three steroids, respectively, using electron pulse radiolysis and absorption spectroscopy. Our value for estradiol is over a factor of 100 slower than the single previously reported rate constant for this compound determined using Co(en) 3 3+ competition kinetics, suggesting that only minimal reduction for this steroid or ethinylestradiol occurs. The faster rate constant for progesterone indicates that the reduction predominantly occurs at its ketone moiety. These rate constants, which are the first direct hydrated electron rate constant measurements reported for estogenic steroids in water, indicate that in comparison to the much faster oxidizing radical reactions reduction will not be a significant destructive pathway in real-world contaminant water treatment.

Photocatalysis using semiconductor catalyst such as TiO 2 , in presence of UV light, is a promising technique for the inactivation of various microorganisms present in water. In the current study, the photocatalytic inactivation of Escherichia coli bacteria was studied with commercial Degussa Aeroxide TiO 2 P25 (Aeroxide) and combustion synthesized TiO 2 (CS TiO 2 ) catalysts immobilized on glass slides in presence of UV irradiation. Thin films of the catalyst and polyelectrolytes, poly(allyl amine hydrochloride) and poly(styrene sulfonate sodium salt), were deposited on glass slides by layer by layer (LbL) deposition method and characterized by SEMand AFMimaging. The effect of various parameters, namely, catalyst concentration, surface area and number of bilayers, on inactivation was studied. Maximum inactivation of 8-log reduction in the viable count was observed with 1.227 mg/cm 2 of catalyst loaded slides. With this loading, complete inactivation was observed within 90 min and 75 min of irradiation, for Aeroxide and CS TiO 2 , respectively. Further increase in the catalyst concentration or increasing number of bilayers had no significant effect on inactivation. The effect of surface area on the inactivation was studied by increasing the number of slides and the inactivation was observed to increase with increasing surface area. It was also observed that the immobilized catalyst slides can be used for several cycles leading to an economic process. The study shows potential application of TiO 2 , for the inactivation of bacteria, in its fixed form by a simple immobilization technique.

This paper describes the solution combustion synthesis, solid-state characterization, photoelectrochemical behavior, and photocatalytic properties of bismuth vanadate (BiVO 4 ). In particular, the influence of combustion precursor was addressed in this study. Bismuth nitrate pentahydrate was used as the bismuth precursor and either vanadium chloride or vanadium oxysulfate was used as the vanadium precursor. Urea, glycine, or citric acid was used as the fuel. Stoichiometric mixtures (1:1) of the fuels and oxidants (with the Bi:V mole ratio also maintained at 1:1) were subjected to solution combustion synthesis. The resultant samples were characterized by X-ray diffraction, highresolution transmission electron microscopy, diffuse reflectance spectrophotometry, thermal analyses, and laser Raman spectroscopy. Methyl orange was used as a probe to test the photocatalytic attributes of the combustionsynthesized (CS) samples, and benchmarked against a commercial bismuth vanadate sample. The CS samples were superior to the commercial benchmark sample, and samples derived from vanadium chloride were superior to vanadium oxysulfate counterparts. The photoelectrochemical properties of the various CS samples were also studied and these samples were shown to be useful both for environmental photocatalytic remediation and water photooxidation applications.

Flumequine is a broad-spectrum antibacterial agent of the quinolone class widely used as veterinary drug in food-producing animals. It is considered as pseudo-persistent compound continuously introduced into the environment and its presence in the environment may contribute to the development of drug resistant bacterial strains. In this study antibacterial activity removal during flumequine degradation by UV/H 2 O 2 was evaluated. The results showed that the advanced oxidation processes (AOPs) using UV/H 2 O 2 was effective in removing the antibacterial activity of flumequine in aqueous solution. The dose-response dropped as the AOP removed flumequine from the solution during the treatment. After 15 minutes, the log dilution rose from -1.0 to -0.18 to achieve the antibacterial veterinary drug EC 50 . Moreover, after 30 minutes it was untraceable, which indicates flumequine degradation through AOP, as confirmed by quantitative HPLC analyses (degradation higher than 99%). It was also shown that the by-products formed during the oxidation did not offer stronger antibacterial activity. These results showed that AOP is technically efficient for the treatment of aqueous solutions containing flumequine.

The objectives of this study were to prepare a high-performance bismuth titanate photocatalyst and to develop a novel photocatalytic reactor with three-phase internal circulating fluidized bed photoreactor (TPICFBP). Bismuth titanate photocatalyst was hydrothermally prepared under optimum operating parameters such as hydrothermal temperature, reaction time and molar ratio of Bi to Ti. The photocatalytic activity of bismuth titanate using TPICFBP was evaluated for the photocatalytic degradation of Acid Red G (ARG). The photodegradation of ARG over Bi 12 TiO 20 (12:1 molar ratio of Bi to Ti) under acidic condition showed the highest removal rate (92%) with wastewater flux and operating time of 10 L/h and 3 h, respectively.

The influence of the technological parameters (temperature (20-100 °C), the molar ratio of allyl alcohol/H 2 O 2 (1:1-5:1), methanol concentration (5-90 wt%), Ti-MWW catalyst concentration (0-5.0 wt%), reaction time (5-300 min) and intensity of stirring (0-500 rpm)) on the epoxidation of allyl alcohol (AA) with 30 wt% hydrogen peroxide over titanium silicalite Ti-MWW catalyst under autogenic pressure and in the presence of methanol as a solvent has been studied. The epoxidation process is the most effective at the following technological parameters: a temperature of 20 °C, the molar ratio of AA/H 2 O 2 = 1:1, the methanol concentration of 90 wt%, the catalyst concentration of 2 wt%, the reaction time 45 min, and the intensity of stirring 350 rpm.

Non-thermal plasma has been widely used for various applications. The observation of discharge plasmas is an essential aspect for understanding the plasma physics of this growing field. Generally, a pulsed discharge having time duration of 100s nanoseconds consists of streamer head propagation, glow-like discharge and arc discharge phases. It is well known that the propagation phenomenon of the streamer head between electrodes is strongly influenced by the polarity of the applied voltage. Typically, both of the positive and negative streamer heads propagate with the acceleration, and the propagation velocity of the positive streamer head is faster than that of the negative one. In the present study, a nano-seconds pulsed power generator which can generate a pulsed voltage with 5 ns of duration and 2.5 ns of rise and fall times was developed, and the propagation of the positive and negative streamer heads were observed using this generator. The results show that the discharge phenomena are totally different from the general pulsed discharge. The average propagation velocity of the nano-seconds streamer heads was 6.1 mm/ns for 67 kV applied voltage, which is five times faster than that of the general one (100 ns of pulse duration). Furthermore, no significant difference of the propagation velocities was observed between the positive and negative applied voltages. The reason for the faster propagation velocity resulted in the nano-seconds pulsed discharge is the faster voltage rise time in comparison with the general pulsed discharge. Furthermore, the application using nano-seconds pulsed discharge for ozone generation showed highest energy efficiency than other discharge methods.

The major part of the regulated priority substances and family of compounds defined in the European Water Framework Directive and some other organic micropollutants were tracked in a municipal biotreated secondary effluent. Micropollutants detected in the effluent were subjected to different ozone doses related to different oxidation extents. Ozone confirmed its efficiency in terms of micropollutant reduction when applied to a municipal biotreated effluent. Accordingly, it achieved reductions exceeding 70% for 91% of the pollutants detected at high ozone dose. Organic matter transformation was also investigated by both controlling evolution of surrogates - including chemical oxygen demand, dissolved organic carbon, UV 254 absorbance, etc. - and the fate dissolved organic fractions by means of size exclusion chromatography followed by organic carbon detection. At ozone dose lower than the initial ozone demand of the effluent, ozone first attacked the hydrophobic aromatic compounds. At ozone dose higher than 50 mg/L, ozone probably solubilized suspended particles and principally oxidized high molecular weight molecules (> 1,000 Da) to convert them into more hydrophilic compounds. Therefore, most reactions of ozone with the micropollutants take place in competition with fast reactions of ozone with the hydrophobic fraction of the dissolved organic matter.

Heterogeneous photocatalysis has been reported to be effective for the degradation of a wide range of organic pollutants and the inactivation of pathogens in water. The use of nanostructured materials is one approach to improving photocatalytic efficiency. Titanate nanotubes were prepared by a hydrothermal synthesis and annealing yielded titania nanotubes, nanorods and crystals. These materials were characterized using XRD, XPS, BET and TEM. The photocatalytic activities were studied using phenol and formic acid as model pollutants. The as-prepared titanate nanotubes had a very high specific surface area (401 m 2 g -1 ). Annealing at 400°C gave anatase TiO 2 , however, the tubular structure collapsed to rods leaving only 30% nanotubes. The sample containing 30% nanotubes was found to be 3.4 times more active than Degussa P25 for the photocatalytic oxidation of formic acid. Annealing at temperatures higher than 400°C caused a reduction in photocatalytic activity for the oxidation of formic acid. This correlated to a decrease in the specific surface area of the samples. In the case of phenol, the rate of photocatalytic oxidation increased with increasing annealing temperature, with the nanocrystals obtained at 700°C showing the highest rate, yet still lower than that observed for P25.

Crystalline TiO 2 films were prepared at 80 °C using a combination of electrochemical and electrophoretical deposition. After optimization of the pre-treatment, the stirring rate and the nanoparticle content of the deposition suspension the solar conversion efficiency of the films could be increased by a factor of five compared to films electrodeposited under otherwise identical conditions without addition of nanoparticles.

The aim of this paper is to give a review of the research on the decomposition of trichloroethylene (TCE), a common industrial solvent, with combined use of non-thermal plasma and heterogeneous catalysis, i.e. plasma-catalysis. This air purification technique has been investigated over the last decade in an effort to overcome the disadvantages of non-thermal plasma treatment of waste air containing volatile organic compounds (VOCs). Some examples of different plasma technologies used for plasma-catalysis are given. These include the dielectric barrier discharge, the pulsed corona discharge and the atmospheric pressure glow discharge. In a plasma-catalytic hybrid system the catalyst can either be located in the discharge region or downstream of the plasma reactor. The mechanisms that drive both configurations are briefly discussed, followed by an extended literature overview of the removal of TCE with plasma-catalysis.