Study of TiO2 anatase nano and microstructures with dominant {001} facets for NO oxidation

Introduction

TiO₂ anatase nanoplates and hollow microspheres were fabricated by a solvothermal?Chydrothermal method using titanium isopropoxide as a titanium precursor and hydrofluoric acid as a capping agent in order to enhance the formation of the {001} crystal facets of the anatase nanocrystals.

Methods

These different morphological structures of TiO₂ anatase can be achieved by only changing the solvent, keeping the amount of the precursor and of the capping agent identical during the solvothermal?Chydrothermal process.

Results and discussion

After calcination of the samples, the adsorbed fluoride atoms on the {001} crystal facets of the TiO₂ anatase nanocrystals were completely removed from their surface according to XPS analysis. The calcined TiO₂ anatase structures were higher crystallized and the specific surface area of the catalysts increased, enhancing their photocatalytic activity in comparison to the non-calcined TiO₂ anatase structures. All TiO₂ anatase samples with adsorbed as well as non-adsorbed fluoride atoms on their {001} crystal facets, exhibited a higher photonic efficiency than Degussa P25, which was used as a reference.

Conclusion

The fluoride free TiO₂ anatase nanoplates exhibited the best photocatalytic activity in oxidizing the NO gas to NO₂ and NO₃ ^?.     

In situ photoelectrochemical/photocatalytic study of a dye discoloration in a microreactor system using TiO2 thin films

Introduction

In this work, we report in situ studies of UV photoelectrocatalytic discoloration of a dye (indigo carmine) by a TiO₂ thin film in a microreactor to demonstrate the driving force of the applied electrode potential and the dye flow rate toward dye discoloration kinetics.

Methods

TiO₂ 65-nm-thick thin films were deposited by PVD magnetron sputtering technique on a conducting glass substrate of fluorinated tin oxide. A microreactor to measure the discoloration rate, the electrode potential, and the photocurrent in situ, was developed. The dye solutions, before and after measurements in the microreactor, were analyzed by Raman spectroscopy.

Results

The annealed TiO₂ thin films had anatase structure with preferential orientation (101). The discoloration rate of the dye increased with the applied potential to TiO₂ electrode. Further, acceleration of the photocatalytic reaction was achieved by utilizing dye flow recirculation to the microreactor. In both cases the photoelectrochemical/photocatalytic discoloration kinetics of the dye follows the Langmuir?CHinshelwood model, with first-order kinetics.

Conclusions

The feasibility of dye discoloration on TiO₂ thin film electrodes, prepared by magnetron sputtering using a flow microreactor system, has been clearly demonstrated. The discoloration rate is enhanced by applying a positive potential (E _AP) and/or increasing the flow rate. The fastest discoloration and shortest irradiation time (50?min) produced 80% discoloration with an external anodic potential of 0.931?V and a flow rate of 12.2?mL?min^?1.     

Comparison of methods for evaluation of activity of photocatalytic films

Objective

This work aims to investigate the correlation between the photocatalytic activity determined by methylene blue bleaching (DIN 52980), stearic acid degradation, and degradation of acetone in gas phase.

Method

The photocatalytic TiO₂ coatings included in this investigation ranged from thin commercially available coatings (Activ^TM and BioClean^TM) and ready to use suspensions (Nano-X PK1245) to lab-produced PVD and sol?Cgel coatings. XRD analysis of the photocatalytic coatings showed that all the coatings consisted of nanocrystalline anatase, although the thickness and porosity varied considerably.

Results

The study showed that the reproducibility of the activity measurements was good. However, more importantly, the investigation showed that there is a good correlation between the activities determined by the different methods even though the characteristics of the photocatalytic coatings and the organic probe molecules varied considerably.

Conclusion

The overall findings of this work suggest that there is a good correlation between the investigated methods. These results are promising for the future work concerning standardization of methods for determination of the activity of photocatalytic films.     

Photocatalytic behavior of nanosized TiO2 immobilized on layered double hydroxides by delamination/restacking process

Introduction

Efficient immobilization of TiO₂ nanoparticles on the surface of Mg₂Al-LDH nanosheets was performed by delamination/restacking process.

Experimental part

The structural and textural properties of as-prepared nanocomposite were deeply analyzed using different solid-state characterization techniques such as: X-ray powder diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopies, chemical analysis, X-ray photoelecton spectroscopy, N₂ adsorption?Cdesorption, and electronic microscopy.

Results and discussion

The photocatalytic properties of immobilized TiO₂ nanoparticles on Mg₂Al were investigated using the photodegradation of two model pollutants: Orange II and 4-chlorophenol, and compared with pure colloidal TiO₂ solution.

Conclusion

It appears that Orange II photodegradation was systematically faster and more efficient than 4-chlorophenol photodegradation regardless of the medium pH. Moreover under slightly basic conditions, even if the TiO₂ photocatalytic efficiency decreases, photodegradation performed in presence of easily recovered TiO₂/Mg₂Al_1.5 nanocomposite gives rise to comparable or better results than pure TiO₂.     

Photocatalytic degradation of gaseous toluene by using immobilized titania/silica on aluminum sheets

Purpose

The aim of this study was to prepare a highly active immobilized titania/silica photocatalyst and to test its performance in situ toward degradation of toluene as one of the major toxic indoor contaminants.

Methods

In this work, two different titania layers immobilized on Al sheets were synthesized via low temperature sol?Cgel method employing presynthesized highly active titania powders (Degussa P25 and Millennium PC500, mass ratio 1:1): (a) with a silica/titania binder and a protective layer and (b) without the binder. The photocatalysts were characterized by X-ray diffraction, nitrogen sorption measurements, scanning electron microscopy (SEM), infrared spectroscopy, and UV?Cvis diffuse reflectance spectroscopy (DRS). The in situ photocatalytic degradation of gaseous toluene was selected as a probe reaction to test photocatalytic activity and to verify the potential application of these materials for air remediation.

Results

Results show that nontransparent highly photocatalytically active coatings based on the silica/titania binder and homogeneously dispersed TiO₂ powders were obtained on the Al sheets. The crystalline structure of titania was not altered upon addition of the binder, which also prevented inhomogeneous agglomeration of particles on the photocatalyst surface. The photoactivity results indicate that the adsorption properties and photocatalytic activity of immobilized photocatalysts with the silica/titania binder and an underlying protective layer were very effective and additionally, they exhibited considerably improved adhesion and uniformity.

Conclusion

We present a new highly photocatalytically active immobilized catalyst on a convenient metallic support, which has a potential application in an air cleaning device.     

Superior photodecomposition of pyrene by metal ion-loaded TiO2 catalyst under UV light irradiation

Background

The photocatalytic degradation of pyrene under UV (125?W Hg-Arc, 10.4?mW/cm²) irradiation of TiO₂ aqueous suspension has been found to be highly improved with the dissolved transition metal ions like Cu²⁺, Fe³⁺, Ag⁺, and Au³⁺, etc. As the reduction potential of these metals lies below the conduction band (CB) position (?0.1?eV) of TiO₂, the photoexcited electron transfer occurs more readily and reduces electron?Chole recombination rate. Therefore, it has a beneficial influence on the photocatalytic ability of TiO₂ because of rapid Fermi energy equilibrium between the CB of TiO₂ and its surface adsorbed metal ions.

Results and discussion

The Fermi level is referred to as the electrochemical potential and plays an important role in the band theory of solids. When metal and semiconductor are in contact, electron migration from photoirradiated semiconductor to the deposited metal occurs at the interface until two Fermi levels equilibrate and enhanced the photocatalytic activity of semiconductor photocatalyst. Ni²⁺ having more negative reduction potential (?0.25?eV) than the CB of TiO₂ imparts negligible co-catalytic activity to TiO₂ photoreaction. It also revealed that loading of Au³⁺ ions displayed higher degradation rate of pyrene than Au photodeposition. Furthermore, when the amount of dissolved Fe⁺³ and Au³⁺ ions gradually increases from 0.1 to 2?wt.%, the pyrene photodecomposition rate also become faster.     

Effect of particle size of titanium dioxide nanoparticle aggregates on the degradation of one azo dye

Introduction

Titanium dioxide (TiO₂) nanoparticle powders have been extensively studied to quickly photodegrade some organic pollutants; however, the effect of the particle size of TiO₂ nanoparticle aggregates on degradation remains unclear because microscale aggregates form once the nanoparticle powders enter into water.

Methods

The degradation of azo dye by different particle sizes of TiO₂ nanoparticle aggregates controlled by NaCl concentrations was investigated to evaluate the particle size effect. Removal reactions of reactive black 5 (RB5) with TiO₂ nanoparticles followed pseudo-first-order kinetics.

Results

The increase of TiO₂ dosage from 40 to 70?mg/L enhanced the degradation. At doses around 100?mg/L TiO₂, degradation rates decreased which could be the result of poor UV light transmittance at high-particle concentrations. At average particle sizes of TiO₂ nanopowders less than around 500?nm, the degradation rates increased with decreasing particle size. As the average particle size exceeded 500?nm, the degradation rates were not significantly changed.

Conclusions

For the complete degradation experiments, the mineralization rates of total organic carbon disappearance are generally following the RB5 decolorization kinetic trend. These findings can facilitate the application of TiO₂ nanoparticles to the design of photodegradation treatments for wastewater.     

Heterogeneous photocatalytic degradation of methyl orange in schwertmannite/oxalate suspension under UV irradiation

Introduction

Schwertmannite was synthesized through an oxidation of FeSO₄ by Acidithiobacillus ferrooxidans LX5 cell suspension at an initial pH?2.5 and 28°C for 3?days and characterized using X-ray diffraction spectroscopy and scanning electron microscope. The schwertmannite photocatalytic degradation of methyl orange (MO) by oxalate was investigated at different initial pH values, concentrations of schwertmannite, oxalate, and MO.

Results

The results demonstrated that photodegradation of MO in the presence of schwertmannite or oxalate alone was very weak. However, the removal of MO was significantly enhanced when schwertmannite and oxalate coexisted in the reaction system. Low pH (4 or less) was beneficial to the degradation of MO. The optimal doses of schwertmannite and oxalate were 0.2?g?L^?1 and 2?mM, respectively. Hydroxyl radicals (·OH) and Fe(II), the intermediate products, were also examined during the reaction to explore their correlation with the degradation of MO.

Conclusion

A possible mechanism for the photocatalytic decomposition of MO in the study was proposed. The formation of Fe(III)-oxalate complexes on the surface of schwertmannite was a precursor of H₂O₂ and Fe(II) production, further leading to the yield of ·OH responsible for the decomposition of MO.     

Photocatalytic degradation of methyl orange by a multi-layer rotating disk reactor

Introduction

Solar wastewater treatment based on photocatalytic reactions is a green process that utilizes renewable energy resources and minimizes secondary pollution. Reactor design plays an important role in promoting treatment efficiency and throughput density (based on unit volume of the reactor).

Experimental

A rotating disk reactor that significantly increases the process efficiency has been designed and evaluated for application to photocatalytic decomposition of dye pollutants in aqueous solutions. In this process, a novel multi-layer rotating disk reactor (MLRDR) was presented. Photocatalyst (TiO₂) particles are immobilized on the surfaces of disks. Within each layer of the reactor, methyl orange aqueous solution is allowed to flow from the center of the disk in a radial direction along the surface of the disk, which is rotating at high speed and is irradiated with UV lamps. The effluent is then directed to the center of another layer that lies underneath. Up to four stacked layers have been tested in this study, and the effects due to the number of the layers and volumetric flow rate on reaction conversion are investigated.

Results and discussion

The efficiency of this photocatalytic reactor exhibits complex dependence on these parameters. With selected operating conditions, conversions greater than 95% can be achieved within seconds of residence time. Design equations of the reactor have been derived based on fluid dynamics and kinetic models, and the simulation results show promising scale-up potential of the reactor.     

Photocatalytic discoloration of Methyl Orange by anatase/schorl composite: optimization using response surface method

The anatase/schorl composites were prepared and employed for the photocatalytic discoloration of an azo dye, Methyl Orange (MO). X-ray diffraction results indicated that TiO₂ existed in the form of anatase phase and no diffraction peaks of schorl could be observed for all the composite samples. Scanning electron micrographs showed that the particles of anatase were well deposited and dispersed on the surface of schorl. Photocatalytic experiments revealed that the anatase/schorl composites exhibited higher photocatalytic activity for MO discoloration than pure TiO₂ and more than 90 % discoloration ratio could be obtained within 60 min UV irradiation when the sample containing 3 wt.% of schorl as TiO₂ support was used. Then, the central composite design (CCD) under the response surface methodology (RSM) was employed for the experiment design and process optimization. The significance of a second-order polynomial model for predicting the optimal values of MO discoloration was evaluated by the analysis of variance (ANOVA) and 3D response surface plots for the interactions between two variables were constructed. Based on the model prediction, the optimum conditions for the photocatalytic discoloration of MO by TiO₂/schorl composite were determined to be 15?×?10^?3 mM MO initial concentration, 2.7 g/l photocatalyst dosage, solution pH 6.6 and 43 min reaction time, with a maximum MO discoloration ratio of 98.6 %. Finally, a discoloration ratio of 94.3 % was achieved for the real sample under the optimum conditions, which was very close to the predicted value, implying that RSM is a powerful and satisfactory strategy for the process optimization.     

TiO2/β-SiC foam-structured photoreactor for continuous wastewater treatment

Introduction

This study of photocatalytic degradation of wastewater was carried out in alveolar cell ??-SiC foam-structured photocatalytic reactors working in a recirculation mode. The immobilization of TiO2 on ??-SiC foams was efficiently obtained through a sol?Cgel technique in acidic conditions.

Discussion

In order to optimize degradation yields obtained by the foam-structured prototype reactor for the photocatalytic water treatment, the operating conditions of the photoreactor have been investigated and the efficiency of the process was evaluated by measuring the photocatalytic degradation of Diuron (3-(3,4-dichlorophenyl)-1,1-dimethyl-urea)) under UV irradiation. Kinetic studies were carried out by investigating the influence of different parameters controlling the reaction (TiO2 loading and ??-SiC foam cell size). The ageing of TiO2/??-SiC foam photocatalytic materials and the mineralization (TOC, Cl?, NO3? and NH4+) of Diuron were investigated.     

碳纳米管/二氧化钛/壳聚糖催化薄膜光催化活性及苯降解机理

通过X-射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)和紫外可见光漫反射谱(UV-vis)对碳纳米管/二氧化钛/壳聚糖复合薄膜的晶体结构和形貌进行表征,以室内空气典型污染物气相苯为模型反应物,研究碳纳米管/二氧化钛/壳聚糖催化薄膜的光催化活性及其对苯的光降解机理。结果表明,制备的碳纳米管/二氧化钛/壳聚糖催化薄膜所具有的良好催化活性归功于碳纳米管、二氧化钛和壳聚糖三者的协调效应;气相苯光降解产生的主要中间产物是乙酸乙酯和十一烷,以及少量的丙烯醛、4-羰基-甲基-苯乙酮、十二烷烃、2,4,-二叔丁基苯酚、二十一烷烃。根据红外光谱分析与GC/MS分析结果,进一步提出了气相苯的降解机理过程。     

Performance evaluation of a continuous flow photocatalytic reactor for wastewater treatment

A novel photocatalytic reactor for wastewater treatment was designed and constructed. The main part of the reactor was an aluminum tube in which 12 stainless steel circular baffles and four quartz tube were placed inside of the reactor like shell and tube heat exchangers. Four UV–C lamps were housed within the space of the quartz tubes. Surface of the baffles was coated with TiO₂. A simple method was employed for TiO₂ immobilization, while the characterization of the supported photocatalyst was based on the results obtained through performing some common analytical methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), and BET. Phenol was selected as a model pollutant. A solution of a known initial concentration (20, 60, and 100 ppmv) was introduced to the reactor. The reactor also has a recycle flow to make turbulent flow inside of the reactor. The selected recycle flow rate was 7?×?10^?5 m³.s^?1, while the flow rate of feed was 2.53?×?10^?7, 7.56?×?10^?7, and 1.26?×?10^?6 m³.s^?1, respectively. To evaluate performance of the reactor, response surface methodology was employed. A four-factor three-level Box–Behnken design was developed to evaluate the reactor performance for degradation of phenol. Effects of phenol inlet concentration (20–100 ppmv), pH (3–9), liquid flow rate (2.53?×?10^?7?1.26?×?10^?6 m³.s^?1), and TiO₂ loading (8.8–17.6 g.m^?2) were analyzed with this method. The adjusted R ² value (0.9936) was in close agreement with that of corresponding R ² value (0.9961). The maximum predicted degradation of phenol was 75.50 % at the optimum processing conditions (initial phenol concentration of 20 ppmv, pH?～?6.41, and flow rate of 2.53?×?10^?7 m³.s^?1 and catalyst loading of 17.6 g.m^?2). Experimental degradation of phenol determined at the optimum conditions was 73.7 %. XRD patterns and SEM images at the optimum conditions revealed that crystal size is approximately 25 nm and TiO₂ nanoparticles with visible agglomerates distribute densely and uniformly over the surface of stainless steel substrate. BET specific surface area of immobilized TiO₂ was 47.2 and 45.8 m² g^?1 before and after the experiments, respectively. Reduction in TOC content, after steady state condition, showed that maximum phenol decomposition occurred at neutral condition (pH?～?6). Figure

The schematic view of the experimental set-up     

Photocatalytic degradation of Orange G dye under solar light using nanocrystalline semiconductor metal oxide

Introduction

The photocatalytic degradation of Orange G (OG) dye has been investigated using synthesised nanocrystalline ZnO as a photocatalyst and sunlight as the irradiation source. The formation of ZnO prepared from its precursor was confirmed through FT-IR and powder X-ray diffraction analyses.

Materials and methods

Surface morphology was characterised by scanning electron microscope and transmission electron microscope analysis. Band gap energy of synthesised nanocrystalline ZnO was calculated using diffuse reflectance spectroscopy (DRS). Different experimental parameters such as effects of pH, dye concentrations and mass of catalyst were standardised in order to achieve complete degradation of the dye molecules under solar light irradiation.

Results

The kinetics of oxidation of OG was also studied. The complete degradation of OG was evident after 90 min of irradiation at an initial pH of 6.86. The degradation of OG was confirmed by UV?CVisible spectrophotometer, high-pressure liquid chromatography, ESI-Mass and chemical oxygen demand analyses.

Conclusion

The adsorption of dye onto catalytic surface was analysed employing model equations such as Langmuir and Freundlich isotherms, and it was found that the Langmuir isotherm model best fitted the adsorption data. The solar photodegradation of OG followed pseudo-first-order kinetics. HPLC and ESI-Mass analyses of the degraded samples suggested that the dye molecules were readily degraded under solar irradiation with nanocrystalline ZnO.     

Photocatalytic reduction of carbon dioxide over Cu/TiO<Subscript>2</Subscript> photocatalysts

The photocatalytic reduction of CO₂ with H₂O was investigated using Cu/TiO₂ photocatalysts in aqueous solution. For this purpose, Cu/TiO₂ photocatalysts (with 0.2, 0.9, 2, 4, and 6 wt.% of Cu) have been synthesized via sol-gel method. The photocatalysts were extensively characterized by means of inductively coupled plasma optical emission spectrometry (ICP-OES), N₂ physisorption (BET), XRD, UV-vis DRS, FT-IR, Raman spectroscopy, TEM-EDX, and photoelectrochemical measurements. The as-prepared photocatalysts contain anatase as a major crystalline phase with a crystallite size around 13 nm. By increasing the amount of Cu, specific surface area and band gap energy decreased in addition to the formation of large agglomeration of CuO. Results revealed that the photocatalytic reduction of CO₂ decreased in the presence of Cu/TiO₂ in comparison to pure TiO₂, which might be associated to the formation of CuO phase acting as a recombination center of generated electron-hole pair. Decreasing of photoactivity can also be connected with a very low position of conduction band of photocatalysts with high Cu content, which makes H₂ production necessary for CO₂ reduction more difficult.     

Cu/La共掺杂TiO2光催化氧化水中的氨氮

采用水解-沉淀法制备了Cu/La共掺杂纳米TiO2催化剂,利用XRD、XPS和BET技术对其进行表征,并考察了在紫外灯下,共掺杂TiO2对氨氮的光催化氧化工艺条件。物相结构和比表面积测试结果表明,共掺杂催化剂具有较好的锐钛矿晶型,孔径分布为4～8 nm,Cu/La共掺杂TiO2La以La3+,Cu是以Cu2+、Cu+的形式掺杂进入TiO2的晶格。光催化实验表明:所得改性光催化剂对氨氮的去除及焦化废水的处理均具有较高的催化活性。     

Characterization of PM10 atmospheric aerosol at urban and urban background sites in Fuzhou city, China

Background

PM₁₀ aerosol samples were simultaneously collected at two urban and one urban background sites in Fuzhou city during two sampling campaigns in summer and winter. PM₁₀ mass concentrations and chemical compositions were determined.

Methods

Water-soluble inorganic ions (Cl^?, NO ₃ ^? , SO ₄ ^2? , NH ₄ ⁺ , K⁺, Na⁺, Ca²⁺, and Mg²⁺), carbonaceous species (elemental carbon and organic carbon), and elements (Al, Si, Mg, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, and Pb) were detected using ion chromatography, thermal/optical reflectance, and proton-induced X-ray emission methods, respectively.

Results

PM₁₀ mass concentrations, as well as most of the chemical components, were significantly increased from urban background to urban sites, which were due to enhanced anthropogenic activities in urban areas. Elements, carbonaceous species, and most of the ions were more uniformly distributed at different types of sites in winter, whereas secondary ion SO ₄ ^2? , NO ₃ ^? , and NH ₄ ⁺ showed more evident urban-background contrast in this season. The chemical mass closure indicated that mineral dust, organic matters, and sulfate were the most abundant components in PM₁₀. The sum of individually measured components accounted for 86.9?C97.7% of the total measured PM₁₀ concentration, and the discrepancy was larger in urban area than in urban background area.

Conclusion

According to the principal component analysis?Cmultivariate linear regression model, mineral dust, secondary inorganic ions, sea salt, and motor vehicle were mainly responsible for the PM₁₀ particles in Fuzhou atmosphere, and contributed 19.9%, 53.3%, 21.3%, and 5.5% of PM₁₀, respectively.     

Diphenyl diselenide attenuates hepatic and hematologic toxicity induced by chlorpyrifos acute exposure in rats

Purpose

In this study, we investigated the effect of diphenyl diselenide [(PhSe)₂] on chlorpyrifos (CPF)-induced hepatic and hematologic toxicity in rats.

Methods

Rats were pre-treated with (PhSe)₂ (5?mg/kg) via the oral route (oral gavage) once a day for 7?days. On the eighth and ninth days, rats were treated with (PhSe)₂ (5?mg/kg) 30?min prior to CPF (50?mg/kg, by subcutaneous route). The aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase activities were determined in plasma of rats. Lipid peroxidation, protein carbonyl, and non-protein thiol levels as well as catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, and gluthatione S-transferase activities were determined in livers of rats. Hematological parameters were also determined.

Results

The results showed that CPF caused hepatic oxidative damage, as demonstrated by an increase in lipid peroxidation and protein carbonyl levels which was associated with a decrease in antioxidant defenses. CPF exposure caused a reduction in the leukocyte, indicating hematologic toxicity. (PhSe)₂ was effective in attenuating these toxic effects caused by CPF exposure in rats.

Conclusions

The results indicated that (PhSe)₂ was effective in protecting the hepatic and hematologic toxicity induced by acute CPF exposure in rats.     

Removal of faecal indicator pathogens from waters and wastewaters by photoelectrocatalytic oxidation on TiO2/Ti films under simulated solar radiation

Purpose

The disinfection efficiency of water and secondary treated wastewater by means of photoelectrocatalytic oxidation (PEC) using reference strains of Enterococcus faecalis and Escherichia coli as faecal indicators was evaluated. Operating parameters such as applied potential (2?C10?V), initial bacterial concentration (10³?C10⁷?CFU/mL), treatment time (up to 90?min) and aqueous matrix (pure water and treated effluent) were assessed concerning their impact on disinfection.

Methods

PEC experiments were carried out using a TiO₂/Ti film anode and a zirconium cathode in the presence of simulated solar radiation. Bacterial inactivation was monitored by the culture method and real-time SYBR green PCR.

Results

A 6.2 log reduction in E. faecalis population was achieved after 15?min of PEC treatment in water at 10?V of applied potential and an initial concentration of 10⁷?CFU/mL; pure photocatalysis (PC) led to only about 4.3 log reduction, whilst negligible inactivation was recorded when the respective electrochemical oxidation process was applied (i.e. without radiation). PEC efficiency was generally improved increasing the applied potential and decreasing initial bacterial concentration. Regarding real wastewater, E. coli was more susceptible than E. faecalis during treatment at a potential of 5?V. Wastewater disinfection was affected by its complex composition and the contained mixed bacterial populations, yielding lower inactivation rates compared to water treatment. Screening the results obtained from both applied techniques (culture method and real-time PCR), there was a discrepancy regarding the recorded time periods of total bacterial inactivation, with qPCR revealing longer periods for complete bacterial reduction.

Conclusions

PEC is superior to PC in terms of E. faecalis inactivation presumably due to a more efficient separation and utilization of the photogenerated charge carriers, and it is mainly affected by the applied potential, initial bacterial concentration and the aqueous matrix.     

Lead concentration increase in the hepatic and gill soluble fractions of European chub (Squalius cephalus)—an indicator of increased Pb exposure from the river water

Purpose

To examine if chronic exposure of feral fish to elevated Pb concentrations in the river water (up to 1???g?L^?1), which are still lower than European recommendations for dissolved Pb in surface waters (7.2???g?L^?1; EPCEU (Official J L 348:84, 2008)), would result in Pb accumulation in selected fish tissues.

Methods

Lead concentrations were determined by use of HR ICP-MS in the gill and hepatic soluble fractions of European chub (Squalius cephalus) caught in the Sutla River (Croatia?CSlovenia).

Results

At the site with increased dissolved Pb in the river water, soluble gill Pb levels (17.3???g?L^?1) were approximately 20 times higher compared to uncontaminated sites (0.85???g?L^?1), whereas the ratio between contaminated (18.1???g?L^?1) and uncontaminated sites (1.17???g?L^?1) was lower for liver (15.5). Physiological variability of basal Pb concentrations in soluble gill and hepatic fractions associated to fish size, condition, sex, or age was not observed, excluding the possibility that Pb increase in chub tissues at contaminated site could be the consequence of studied biotic parameters. However, in both tissues of Pb-exposed specimens, females accumulated somewhat more Pb than males, making female chubs potentially more susceptible to possible toxic effects.

Conclusions

The fact that Pb increase in gill and hepatic soluble fractions of the European chub was not caused by biotic factors and was spatially restricted to one site with increased dissolved Pb concentration in the river water points to the applicability of this parameter as early indicator of Pb exposure in monitoring of natural waters.