Volume 16, Issue 1

Pseudomonas Aeruginosa, Aeromonas hydrophila, Legionella pneumophila bacteria are waterborne pathogens commonly found in water and linked to infectious diseases. Especially, they can survive and colonize water systems, particularly in worm water system. On-site supplemental disinfection of water systems might be one of the approaches to prevent water born diseases. In this work, the inactivation of these waterborne pathogens using a single compartment electrochemical flow cell equipped with Boron Doped Diamond (BDD) anode and Titanium cathode was investigated. The bactericidal activity of galvanostatic electrolysis using BDD anode was evaluated on synthetic contaminated waters containing P. Aeruginosa, A. hydrophila, L. pneumophila. BDDanodic oxidation at current density of 50 mA cm -2 achieved total death of waterborne bacteria in treated water samples for bacterial cell density in the range 10 7 - 10 8 CFU mL -1 . The effects of certain experimental parameters (current density, NaCl concentration, cell density, and flow rate) on kinetics and efficiency of BDD-anodic oxidation during electrochemical disinfection of bacteria suspensions were also examined. The results have indicated that the bactericidal activity of BDD anodes increases with increasing current density and NaCl concentration. This can be explained by the contribution of mediated oxidation with electrogenerated oxidants including hydroxyl radicals, hydrogen peroxide, ozone and free chlorine in the inactivation mechanism of waterborne bacteria at high current densities. This research work has shown that BDD anode is promising tool for inactivation of waterborne pathogens in water and wastewater disinfection.

The impact of O 2 and H 2 O 2 on the efficiency of TiO 2 photocatalysis has been studied in this work. Tris(hydroxymethyl)aminomethane (Tris) was used to probe the efficiency. Upon hydrogen abstraction by e.g. hydroxyl radicals from Tris, formaldehyde is formed. This product was detected and quantified using a modified version of the Hantzsch method. A significant increase in the formaldehyde production rate was observed upon addition of O 2 or H 2 O 2 . It was also found that O 2 and H 2 O 2 are equally effective in scavenging the photo-excited electron, which is probably a result of their similar adsorption properties. A strong concentration dependence, independent of O 2 or H 2 O 2 content, was found at low Tris concentrations (< 100 mM). Adsorption studies of H 2 O 2 onto the TiO 2 surface were performed in order to explore the rate controlling reactions. The results show that H 2 O 2 , having a stronger adsorption affinity than Tris towards the photocatalytic surface, govern the kinetics, but only until a monolayer is built up.

Low temperature atmospheric pressure plasmas (LTPs) together with advanced oxidation processes (AOPs) are alternative to conventional chemical methods of soil decontamination. The processing of soil itself depends on several factors, like type of soil and pollutants, treatment technique, geological and atmospheric circumstances. In the paper problems of soil, water, buildings, farms, land, and housing contaminations after floods and ecological disasters have been introduced. Plasma aided techniques together with AOPs have been presented from the point of view of decontamination potential as well as their impact on soil properties and fertility. Additionally, nanosize biological phenomena occurring in DNA strands during ozonation were visualized. The reaction of ozone with DNA is essential to understand the sterilization in agricultural soil. The structural images of the DNA samples were taken with the atomic force microscopy (AFM). It was shown that highly concentrated ozone broke hydrogen bonding of nuclei bases of DNA in relatively short time.

The review, based on 92 references, is focused on degradation of organics by ozonation and it comprises various classes of oxygen-containing organic compounds - alcohols, ketones, ethers and hydroxybenzenes. The mechanisms of a multitude of ozone reactions with these compounds in organic solvents are discussed in details, presenting the respective reaction schemes and the corresponding kinetic parameters are given and some thermodynamic parameters are also listed. The dependencies of the kinetics and the mechanism of the ozonation reactions on the structure of the compounds, on the medium and on the reaction conditions are revealed. The various possible applications of ozonolysis are specified and discussed. All these reactions have practical importance for the protection of the environment.

Recently, many different plasma sources are being investigated for exhaust gases treatment, odor abatement, VOC removal, soil conditioning, surface decontamination or tissue disinfection and sterilization. Among many different plasma reactors investigated in laboratories, gliding arc discharges (GAD), dielectric barrier discharges (DBD), pulsed discharges (PD), atmospheric pressure glow discharges (APGD) and atmospheric pressure plasma jets (APPJ) seem to be the most promising for high pressure low temperature applications. They can be designed as multi-electrodes’ high power system that can be used in environment protection processes, like decontamination of large surfaces and treatment of large volume of polluted gases, as well as small size and low power devices for biomedical applications, like plasma healing, disinfection and sterilization. Paper presents review of power supply systems for cold plasma reactors. Dielectric Barrier Discharge (DBD), Gliding Arc Discharge (GAD) and atmospheric pressure plasma jet (APPJ) reactors with their supply systems have been discussed from the point view of their characteristics, possibility to control power to the discharge and efficiency. Taking into account the plasma reactor characteristics and nature (nonlinear resistive and/or capacitive) different solutions of power suppliers have been presented: transformer type, AC/DC/AC inverter, RF-frequency system and frequency resonant inverter.

The present work describes a suitable method for treatment of water contaminated with nitrate by using a photo-electrochemical method. A Cu/Cu 2 O electrodeposited electrode is used as photocathode with long-term stability under UV irradiation and applied potential of +0.2 V vs Ag/AgCl. In this condition 93% of nitrate is removed after 75 min of photoelectrolysis conducted in NaCl 0.07 mol L -1 and pH = 7. Nitrate reduction on Cu/Cu 2 O photoelectrodes occurs in the cathodic compartment cell via electrons generated under UV irradiation, as expected for a p-type electrode leading to 42% of remaining nitrite and 52% gaseous nitrogen derived, respectively.

The heterogeneous photocatalytic partial oxidation of cyclohexane in gas-phase as an alternative green process for fine chemicals synthesis was successfully achieved on Au/TiO 2 photocatalysts prepared by photodeposition technique. Different gold loadings ranging between 0.5 and 2 wt.% of photodeposited Au on TiO 2 synthesized by sol-gel method were obtained by changing the concentration of gold precursor at fixed illumination intensity and time. The cyclohexane partial photoxidation was conducted in a gas-solid photocatalytic fluidized bed reactor at high illumination efficiency. Main observed reaction products were cyclohexanol, cyclohexanone and CO 2 . The resulting selectivity was dramatically influenced by the gold content. The reaction temperature was a critical parameter to reach the photocatalysts stability, avoiding deactivation phenomena while the tuning of Au content of the photocatalysts, resulted in the promotion of the formation of cyclohexanol or cyclohexanone with high selectivity. In particular, by increasing Au content, the process selectivity is completely reversed, passing from high cyclohexanol selectivity (75%) to high selectivity to cyclohexanone (80%). These promising results evidenced that Au/TiO 2 catalysts in the selected operating conditions, are effective materials for the synthesis of cyclohexanone and cyclohexanol in gas-phase by photocatalysis, at very low reaction temperatures and without the additional step of catalyst recovering needed in the liquid partial oxidation of cyclohexane.

The present study aims to find the mechanism of the better performance of sunlight/Fe 2+ /persulphate oxidation on the bases of degradation of acidic Congo red.The major intermediate product formed from acidic Congo red was 3,4-naphthalene quinonoids imine-1-sulfonate, a kind of Quinonoids imine compound. It was found that the 3,4-naphthalene quinonoids imine-1-sulfonate can be degraded immediately under the irradiation of UV lights or sunlight, and the degradation effect under sunlight was superior to those under UV. It was photosensitive to visible light. Thus it happened in photosensitive reaction process under visible light and could produce singlet oxygen ( 1 O 2 ) and the superoxide radical (O 2 · - ). O 2 · - could promote the generation of hydroxyl radicals ( · OH) and sulfate radicals (SO 4 - ) in acidic environment, and subsequently cause increase of active substances in the system. Therefore, the sunlight/Fe 2+ /persulphate degradation method might be an attractive alternative technology for the treatment of industrial dye.

The degradation of 40 mg/L (0.175 mM) of Bisphenol A in water has been investigated using four different oxidation processes: Fenton reagent, UV, UV/H 2 O 2 and ultrasound. The treatment of Bisphenol A with the Fenton reagent (c (Fe 2+ ) = 0.692 mM, c (H 2 O 2 ) = 1.380 mM) resulted in the complete removal of the targeted compound in less than 1 min. UV/H 2 O 2 (c (H 2 O 2 ) = 0.495 mM) treatment was able to complete degrade the molecule in 40 min. Without H2O2, direct photolysis accounts for 67% of Bisphenol A removal in 1 h. Ultrasonic treatment at 20 kHz and 300 W conducted at initial pH of 3.5, 7.0 and 10.5 has shown to be the least effective process. Regardless of the initial pH, 1 h of the treatment resulted in only 30% degradation. LC/MS of the treated solutions revealed a variety of byproducts some of which have not been yet reported in the studied oxidation processes.

Solar cells with a superstrate structure of <carbon/CuInS 2 /In 2 S 3 /ZnO/fluorine-doped SnO 2 glass> were fabricated with CuInS 2 absorber, In 2 S 3 buffer, and ZnO, deposited by spray pyrolysis. The ZnO films fabricated from zinc chloride and zinc acetylacetonate precursors had a rougher surface than film fabricated from the zinc acetate dihydrateprecursor. The band gap of the ZnO film on the FTO substrate was approximately 3.17 eV. The effects of annealing temperature and time on cell performance were analyzed. The cells with the ZnO layer annealed at 650 °C for 30 min showed the best photovoltaic properties. The parameters of the best cells were a short-circuit photocurrent density of 9.72 mA cm -2 , open-circuit voltage of 0.55 V, fill factor of 0.45, and efficiency of 2.50%.

Efficiency of ozonation process for simultaneous degradation of two antibiotics, ciprofloxacin (CIP) and oxytetracycline (OTC), at high and low concentrations of them was investigated in artificially contaminated waste activated sludge (WAS). The desorption of the antibiotics, which was provided either by Mg 2+ pretreatment or alkaline addition to the sludge prior to ozonation had a crucial role on their efficient oxidation. Almost complete destruction of OTC spiked at high concentration was achieved by combined application of ozonation with Mg 2+ pretreatment at pH 8, which provided selective desorption of the antibiotics by probable formation of soluble metal antibiotic complexes. Alkaline addition to the WAS in order to elevate the pH to 11.5 resulted in both antibiotic desorption and organic matter solubilization, which exerted a competitive demand for oxidants. This competition was more pronounced at low spiking concentration of the antibiotics. Nevertheless, >95% degradation of CIP spiked at both high and low concentrations was achieved by ozonation at alkaline pH due to substantial desorption of the antibiotic. At acidic pH, the effect of metal solubilization on reactive radical formation during the ozonation process was also demonstrated in this study.

The β-lactam antibiotics are some of the most persistent anthropogenic pharmaceutical contaminants, and consequently are currently being detected in many aquatic environments. The presence of any level of antibiotics in water may contribute to the emergence of antibiotic-resistant bacterial strains, and therefore the active removal of these pharmaceuticals by additional water treatments such as advanced oxidation and reduction processes may be required. In this study, we report on our efficiency measurements for the hydroxylradical- based degradation of three β-lactam antibiotics obtained using steady-state 60 Co gamma radiolysis and bacterial growth inhibition measurements to determine the average number of oxidations required to completely remove all antibiotic activity. These values ranged from four hydroxyl radical oxidations per antibiotic molecule for Penicillin-G to nine for Amoxicillin. The large variation in this oxidative efficiency shows that most of radical oxidation occurs at peripheral moieties in these molecules, consistent with the conclusions of previous kinetic rate constant data.

TiO 2 nanotubes with controlled tube lengths were prepared by the anodization method and were utilized to investigate the photocatalytic and photoelectrocatalytic activities on Acid Red 4 decomposition in aqueous solution. Effects of annealing temperature and ramping rate on the surface dimension and crystal phase composition of prepared TiO 2 nanotubes were studied. For Acid Red 4 decomposition by photoelectrocatalytic process, experiments using TiO 2 nanotube exhibited up to 90% enhancement than those using granular TiO 2 - coated film due to the better charge transport ability of nanotube structure. Decomposition of Acid Red 4 by photocatalytic and photoelectrocatalytic processes for experiments using TiO 2 nanotube was enhanced with increasing nanotube length in the length range of 500-1,000 nm. For experiments using TiO 2 nanotube longer than 1,000 nm, photocatalytic and photoelectrocatalytic decomposition of Acid Red 4 were retarded.

A series of nitrogen-doped TiO 2 nanostructured photocatalysts were synthesized by oxidizing titanium nitride at different temperatures under ambient condition. The as-prepared samples were systematically characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-Vis) absorption spectra. The photocatalytic activity for hydrogen evolution of the as-prepared samples was evaluated under UV-Vis light irradiation. XPS investigations confirmed the presence of nitrogen in TiO 2 lattice in the chemical environment of O−Ti−N. The UV-Vis absorption spectra results showed that the absorption edge was extended into visible light region. Higher photocatalytic activity than that of commercial titanium dioxide - P25 was observed over the as-prepared nitrogen-doped TiO 2 under UV-Vis light illumination.

Disinfection byproduct (DBP) formation during the treatment of raw Colorado River Water (CRW) using aqueous chlorine and ultraviolet (UV) light advanced oxidation processes (AOPs) was investigated. Here, CRW was combined with aqueous chlorine from two distinct sources (electrochemically-generated Mixed Oxidant Solution (MOS) and commercial sodium hypochlorite) and then exposed to ultraviolet C (UV-C) and ultraviolet A (UV-A) light. The impact of the treatment process on the structure of (NOM) in the CRW was examined, as well as the resulting production of various halogenated organic Disinfection By-Products (DBPs). Both AOP conditions tested resulted in destruction of chromophoric components of the NOM, while formation of total amounts of haloacetic acids and trihalomethanes was far below the US EPA regulated maximum contaminant level values for these contaminants, even though the UV and chlorine doses used in these studies were much higher than the typical doses used in an actual treatment process.

Four different photocatalytic paints supplied by PIGMENT company (Poland) were tested for their self-cleaning properties. Benzo[a]pyrene (BaP) as a representative of hazardous PAHs (Polycyclic Aromatic Hydrocarbons) was selected as a model pollutant. The photocatalytic tests were performed in a solar simulator Suntest CPS+/XLS+. The photocatalytic paint was coated on the porcelain cuvette. BaP was loaded on the surface of the photocatalytic paint after its dissolution in acetone. The concentration of BaP was measured by UV-Vis spectroscopy. The results showed that indoor paints (latex and acrylic) were more photoactive than silicate ones, 0.05 mg of loaded BaP was almost completely decomposed on their surface after 60 min of irradiation whereas for silicate paints this time was much longer. It appeared that hydrophobic nature of indoor paints was more favorable for BaP decomposition. At the beginning the rate of BaP decomposition was going fast, but then slowed down because of formation of the decomposition products, such as 1,2 - benzendicarboxylic acid and hexadecanoic acid 2-hydroxy-1 (hydroxymethyl) ethyl ester, which also followed decomposition. Additionally it was observed that some paint constituents were decomposed after exposure to solar irradiation.

The decolouration effect of ozone on the reactive dye Reactive Red 198 in a CSTR was the subject of a series of experiments. The results showed that ozonation is capable of reducing the colour remaining in the water after using reactive dyes rapidly and effectively of around 15 minutes. The effect of the frit was analysed to check that it was not a factor limiting oxidation. The effect of flow rate and of the initial concentration of dye on the dye concentration as a function of time and at steady state were measured, and the rate of decolouration was calculated under both steady and unsteady state conditions. The flow rate was adjusted for various initial dye concentrations as well as at various flow rates of dye solutions. The apparent first order rate constant is about 0.10 min -1 . Though first-order kinetics in dye concentration fitted the individual sets of results, the rate constants were significantly different from those expected, suggesting that any model that aims to predict the results in general would need to be more complex, and probably include modelling the effective ozone concentration.

Bi 2 O 3 and Rh-doped Bi 2 O 3 photocatalysts with different molar ratio of Rh/Bi (1%, 2% and 3%) were prepared by a sol-gel method. The photocatalysts prepared were studied by BET surface area, X-ray diffraction (XRD), UV/Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopic (XPS) techniques and surface photovoltage spectroscopy (SPS), respectively. The results show that 2% sample prepared has the highest BET surface area, pore volume, the smallest pore size. The XRD spectra of the Rh-doped Bi 2 O 3 catalysts calcined at 773 K is composed of monoclinic and tetragonal phases. Rh-doped Bi 2 O 3 absorbs much more light than Bi 2 O 3 in the visible light region. XPS results reveal the binding energy of Bi 4f 7/2 and O 1s of 2% and 3% samples shifts to a lower value. Doping Rh into the lattice of Bi 2 O 3 influences the photoinduced charge separation rate of Bi 2 O 3 . Rh-doped Bi 2 O 3 with 2% Rh possesses the best photocatalytic activity and the underlying reason was discussed.

The present study reports the photocatalytic degradation of phenol in aqueous solution by titanium dioxide coupled with magnetic field. The photocatalyst TiO 2 is prepared by the microwave-assisted hydrothermal method and characterized by XRD and BET. The effect of catalyst calcination temperature and the operational parameters on phenol degradation is discussed and optimized. The optimal conditions are magnetic field intensity 0.082 T, TiO 2 dosage 1.0 g L -1 and air flow rate 1000 mL min -1 . Under optimal conditions, after 240 min irradiation, the degradation of phenol can reach up to 80.6%. With 0.082 T magnetic field applied to the reaction system, 30.1% degradation rate constant enhancement was achieved compared to that without magnetic field. The results show that the photocatalytic degradation of phenol by titanium dioxide can be enhanced by coupling with magnetic field.

In this study the photonic efficiency of different UV activated AOP methods are compared in regard to the oxidation of the dye p-nitrosodimethylaniline (RNO). The UV activated methods include heterogeneous photocatalysis (TiO 2 /UV), UV activated persulfate (UV/S 2 O 8 2- ) and hydrogen peroxide (UV/H 2 O 2 ), vacuum UV irradiation (VUV) and combination of these. The photonic efficiencies were determined both by measuring the bleaching of RNO by UV/VIS and by measuring the decomposition by TOC. The results of this investigation showed that the highest photonic efficiency was observed for the system consisting of VUV/H 2 O 2 (3.06%). Similar photonic efficiencies were observed for the UV/H 2 O 2 , UV /TiO 2 (suspension), and UV/S 2 O 8 2- process. These numbers suggest that only around 3% of the emitted photons are used in the bleaching of RNO. The photonic efficiency for the mineralization of RNO for the UV/H 2 O 2 process was determined to around 20%. No synergistic effect was observed when combining photocatalysis with H 2 O 2 , S 2 O 8 2- or VUV irradiation. In all the latter cases it was found that the bleaching rates for these techniques alone were higher than those observed combined with photocatalysis. The only process showing synergistic effects was the system consisting of VUV/H 2 O 2 .

Dithizone is an extracting agent largely used for metallurgical processes and has been found in waste waters. Its degradation is studied by exposing basic solutions to a gliding arc discharge burning in various gases (i.e., humid and dry air, humid air and tert-butanol) to underline the role of the formed °OH radicals and H 2 O 2 . The acidity (pH) of the treated target solution depends on the feed gas: the pH remains constant for dry air discharges and increases in the presence of NaOH pellets. The degradation of dithizone to give CO 2 , CO, and sulfate is optimized with water saturated air with a resulting abatement by 91.97% within 30 min. The kinetic study suggests a pseudo zero order process followed by a 1 st order step. Post-discharge 1st-order reactions are also observed over 3 days and may be attributed to the additional reactivity of H 2 O 2 and NO derivatives such as peroxynitrite.

HZSM-5 zeolite was modified by phosphoric acid treating and a sol-gel method was used to prepare the TiO 2 loading on HZSM-5. The composite photocatalysts were characterized by XRD, SEM, BET and XPS measurements. The composite 50%TiO 2 /0.5HZSM-5 had as similar particle shape as HZSM-5 in the size around 2-5 μm. The XRD patterns indicated the existence of anatase TiO 2 and HZSM-5 in the supported photocatalyst. High temperature calcination was beneficial to crystal formation of TiO 2 , and the TiO 2 crystalline size was less than 23.9 nm for the samples that was calcinated at 600 °C. XPS results indicated that titanium was in the full oxidation state of Ti 4+ in the 50%TiO 2 /0.5HZSM-5, in which titanium oxide existed as TiO 2 . Using Reactive Brilliant Red X-3B as a test substance, photocatalytic experiments under UV light irradiation demonstrated that the 50%TiO 2 /0.5HZSM-5 prepared at 400 °C for 2 h had the maximum degradation activity. When TiO 2 concentration was 100 mg/L and the initial RBR X-3B concentration was 40 mg/L, 93.4% of the dye was degraded on the composite photocatalyst after 2 h of reaction.