UV Light Intensity Research Articles

Treatment of real wastewater from the graphic industry using advanced oxidation technologies: Degradation models and feasibility analysis

Many organic contaminants present in industrial effluents are resistant to conventional treatments. The application of Advanced Oxidation Technologies (AOT's) to a system of great complexity and unknown composition was studied. The proposed AOT's arise from the combination of UV light irradiation (254 nm) in the presence of commercial steel wool (CSW - zerovalent iron) and H2O2 as an oxidant, resulting in degradation processes by UV photolysis, UV/H2O2, Fe°/H2O2 and UV/H2O2/Fe°. The system used was an effluent from a graphic industry. High organic load and low biodegradability are characteristics of these wastewaters. The CSW was characterized by SEM/EDS. The effect of pH, H2O2 concentration, mass of CSW, intensity of UV light and temperature on the reduction of chemical oxygen demand (COD) of the effluent was evaluated employing a screening design. Afterwards, significant factors ([H2O2], light intensity and temperature) were selected to study their effect on COD reduction employing a central composite design. Optimum operating conditions predicted (0.06 mol L−1 of H2O2, UV254 nm of 1.6 × 10−5 E s−1 and 44 °C at pH ca. 6.5.) generated an experimental COD reduction of 98.22% at lab scale. These conditions were also tested at pilot scale. Furthermore, phytotoxicity of treated effluents was analyzed.

Insight into the Degradation of Two Benzophenone-Type UV Filters by the UV/H2O2 Advanced Oxidation Process

Environmental problems caused by UV filters, a group of emerging contaminants, have attracted much attention. The removal of two typical UV filters benzophenone (BP) and 4,4′-dihydroxy-benzophenone (HBP) in water was investigated by the UV/H2O2 process. The response surface methodology (RSM) and central composite design (CCD) were applied to investigate the effects of the process parameters on the degradation rate constants, including the initial contaminant concentration, H2O2 dose, and UV light intensity. BP is more easily degraded by the UV/H2O2 process. Both processes followed pseudo-first-order kinetics. The results obtained with the built RSM model are in accordance with the experimental results (adjusted coefficients R2(adj)= 0.9835 and 0.9778 for BP and HBP, respectively). For both processes, the initial contaminant concentration (exerting a negative effect) were the most important factors controlling the degradation, followed by H2O2 dose and UV intensity (exerting positive effects). A total of 15 BP degradation products and 13 HBP degradation products during the UV/H2O2 process were identified by LC/MS and GC/MS. A series of OH radical irritated reactions, including hydroxylation, carboxylation, and ring cleavage, led to the final degradation of BP and HBP. Degradation pathways of BP and HBP were also proposed. On the whole, this work is a unique contribution to the systematic elucidation of BP and HBP degradation by the UV/H2O2 process.

The structure and luminescence of boron nitride doped with Ce ions

Highly luminescent boron nitride (BN) was synthesized by pyrolysis of molecular adduct prepared by chemical mixing of boric acid and melamine with a small amount of cerium nitrate. After pyrolysis, Ce ions were substitutionally incorporated to B3N3 hexagonal layer of turbostratic BN at a very low doping level which was estimated to be less than 7 × 1018 atoms/cm3. Ordered stacking of hexagonal layers along c-axis of BN or transformation of turbostratic BN to hexagonal BN was induced by addition of Ce ions even though the amount of Ce ions surpassed substitutional doping limits. The intense photoluminescence (PL) spectrum of Ce-doped BN was detected at 390 nm by excitation of UV light (λ = 314 nm) and PL intensity was improved with increasing level of Ce addition following the enhanced crystallinity of turbostratic BN. The origin of UV-emission was ascribed to the transition from the crystal field components of the 5d level to the 4f ground states of the Ce3+ ion.

Textile Wastewater Treatment Using Photonanocatalytic Process (UV/CuO Nanoparticles): Optimization of Experiments by Response Surface Methodology

: This study examines the efficiency of photodegradation process (color and COD removal) in textile wastewater treatment, using copper oxide nanoparticles (CuO-NPs) as photocatalyst to propose a suitable alternative for the available approaches. The experiments were developed, using a central composite design and response surface methodology (RSM). RSM was applied to evaluate the effects of different variables, including pH, CuO- NPs concentration, reaction time, and UV light intensity, as well as their interactions for achieving optimal conditions. The second-order model consisted of linear and quadratic terms, which seemed appropriate for color and COD removal. All the variables showed significant effects on color and COD degradation. The optimal conditions for maximum color degradation (83%) included pH of 6.9, contact time of 60 min, CuO- NPs concentration of 0.05 g/L, and UV light intensity of 30 W. In addition, the optimal conditions for maximum COD reduction (99%) were pH of 6.8, contact time of 60 min, CuO-NPs concentration of 0.02 g/L, and UV light intensity of 30 W. Based on the results of this study, CuO-NPs can be used for effective treatment of textile wastewater by high COD and color removal.

Modeling of a photocatalytic batch reactor for pollutant removal using photocatalyst nanoparticles: an analytical solution development

Photocatalytic batch reactors (PCBR) have been widely used for photodegradation of organic pollutants due to their simplicity, high efficiency, and flexibility. To improve the performance of these types of reactor, mathematical models can be employed along with the experimental data to study the impacts of involved factors such as UV light intensity, photocatalyst size, and initial concentration of the pollutant. In this study, a PCBR was modeled based on the mass conservation law for pollutant in both solution and catalyst phase. An analytical solution to the obtained partial differential equations is reported for the first time, which enables the calculation of photocatalytic performance versus time for low to moderate pollutant concentrations. The analytical solution was verified with the published experimental data for Pb2+ reduction by WO3/TiO2 nanoparticles. In addition, the analytical solution was used to investigate the effect of photocatalyst size, photocatalyst concentration, and UV intensity on the degradation performance.

Degradation of geosmin and 2-methylisoborneol in water with UV/chlorine: Influencing factors, reactive species, and possible pathways

Geosmin (GSM) and 2-methylisoborneol (2-MIB) are two common odor compounds in drinking water. In this paper, the performance of UV/chlorine was compared with that of chlorine and UV to degrade GSM (100 ng L−1) and 2-MIB (100 ng L−1) in water. UV/chlorine was further exploited, and a steady-state kinetic model was used to conduct a detailed study on efficiency, rate, reactive species and pathway. The results showed that UV/chlorine greatly could improve the removal ratio to 90% within 5 min, from approximately 20% with only UV or dark chlorine in 60 min. The removal ratio and rate depended on UV light intensity, free chlorine dosage, reaction time and water quality parameters (e.g. pH, concentrations of HCO3− and Cl−). Among these factors, the first two obviously could accelerate the rate and increase the ratio. The degradation was also significantly improved in an acidic condition, while alkaline conditions and HCO3− had inhibitory effects, and Cl− created no difference. Contributions of OH and Cl to the degradation of 2-MIB and GSM were further revealed, and OH was found to be the most important reactive species. In the UV/chlorine process, 6 degradation byproducts of 2-MIB, including 1 alcohol, 2 ketones, and 3 olefins, were identified, and 14 degradation byproducts of GSM, including 6 ketones, 1 aldehyde, 2 alcohols, 3 naphthenes, and 2 olefins, were found by using solid-phase microextraction coupled to gas chromatography-mass spectrometry. The possible degradation pathways of GSM and 2-MIB in UV/chlorine thus were proposed.

Theoretical and experimental analysis of photovoltaic-electrostatic driving flexible cantilever beam

A model of photovoltaic-electrostatic driving flexible cantilever beam based on PLZT ceramic is proposed in this paper. New equivalent electrical model of PLZT ceramic connected to a parallel plate composed of two copper foils is obtained by modifying the original PLZT equivalent electrical model. After that, the mechanicalmodel of photovoltaic-electrostatic driving cantilever beam is established. Furthermore, the influences of UV light intensity on the deflection of the photovoltaic-electrostatic cantilever beam are analysed via the theoretical and experimental method. The analysis results indicate that the deflection at the end of cantilever beam increases with the increase of light intensity.

Impact of TiO2 and TiO2/g-C3N4 Nanocomposite to Treat Industrial Wastewater

This work aims to implement the environmental application of nanotechnology in terms of semiconductor-based photocatalysis to treat real tannery effluent. In this context, g-C3N4 prepared by melamine pyrolysis was added with TiO2 at different weight percentage to form TiO2/g-C3N4 nanocomposites, these composites were characterized and based on the optical property, 80% TiO2/g-C3N4 nanocomposite with a band gap of 2.88 eV was chosen for the photocatalytic experiment. During the photocatalytic experiments, the performance of TiO2 and TiO2/g-C3N4 nanocomposite was compared and examined in terms of Phenol, Chemical oxygen demand (COD) and color reduction. It was observed that under optimum conditions (UV-irradiance time of 180 min, pH 5, with H2O2 concentration 0.8 g/L, flow rate of 3 l/h (litre per hour), and UV-light intensity 556.13 μE) TiO2/g-C3N4 composite exhibited higher photocatalytic efficiency than that of pure TiO2. These conditions assist 93.06% phenol, 85.62% COD, and 80.23% color reduction using TiO2/g-C3N4 nanocomposite while with TiO2 it was 72.39%, 68.95, and 65.80% respectively.Furthermore, the addition of H2O2 enhanced the photocatalytic degradation efficiency following a Langmuir-Hinshelwood model which authenticates pseudo-first-order reaction kinetics. The apparent rate constant and mass transfer coefficient for TiO2/g-C3N4/H2O2 was found to be 2.09 and 2.11 times higher than that of TiO2/H2O2.

Enoxacin degradation by photo-Fenton process combined with a biological treatment: optimization and improvement of by-products biodegradability

This study evaluates the effectiveness of coupling a photo-Fenton process with a biological treatment on the mineralization of enoxacin, an antibacterial agent belonging to the fluoroquinolones group. The influence of some operating parameters, such as UV light intensity, hydrogen peroxide and Fe(II) concentrations, on 50 mg L−1 enoxacin degradation and by-products mineralization was evaluated. The biodegradability of the target molecule was also investigated, reporting a BOD5 on COD ratio of 0.95 after 60 min of irradiation at 15 mmol L−1 of H2O2, 0.5 mmol L−1 of Fe(II) and 30 W m−2 of UV A light intensity. The monitoring of the advanced oxidation state (AOS) of the irradiated solution during the treatment displayed a maximal oxidation state of 0.25 for 90 min of photo-degradation. A comparison between the photo-Fenton process and other oxidative processes [UV alone, UV/H2O2, H2O2, H2O2/Fe(II)] was carried out showing a marked improvement in enoxacin mineralization while combining UV A light with the Fenton reagent (41% of TOC decay improvement compared to the Fenton process). Finally, activated sludge culture for non-treated and pre-treated enoxacin at optimal conditions was conducted during 10 days. The obtained TOC results reported a mineralization improvement with a maximal mineralization yield of 43% for the biodegradation of irradiated samples. The relevance of coupling the photo-Fenton process with a biological process for the enoxacin treatment was therefore proven.

Preparation of TiO2/C/Fe3O4 Magnetic Composite Catalyst and Research of its Photocatalytic Performance

TiO2/C/Fe3O4 magnetic composite catalyst was prepared by using glucose as carbon source to attach an intermediate isolation layer and then wrapping TiO2 directly on Fe3O4 magnetic support. The catalytic performance of the catalyst was studied by photodegradating RhB simulated wastewater under the changed external conditions such as light resource, temperature, pH and ion intensity of the solution. It was found that the photocatalytic performance under uv light was better than that of the catalyst under the visible light. The photocatalytic performance increased with the increase of temperature and acidity of the wastewater, and the decrease of the ion intensity of the wastewater. The optimum photocatalytic reaction condition was under uv light, the temperature was 75°C, pH was 1 and ion intensity was 1mmol/L. The magnetic effect was applied to the reutilization of the catalyst, and the fourth recycled catalyst still had catalytic activity, but with the increase of reusing time, the photocatalytic performance of the catalyst decreased gradually. The photodegradation rate of the recycled catalyst 90 min later was reduced from 76.20% to 57.08%, 41.80%, 28.44%, respectively, while 4 times of repeated use under uv light, 25°C, pH 1, and ion intensity 1 mmol/L.

Understanding the effect of ultraviolet light intensity on disinfection performance through the use of ultraviolet measurements and simulation.

We measured the disinfection of MRSA and Clostridium difficile spores using an ultraviolet C (UV-C) device, and we correlated those results to measurements and computer simulations of UV-C surface intensity. The results demonstrate both large differences in UV light intensity across various surfaces and how this leads to significant differences in disinfection.

Photocatalytic Growth of Hierarchical Au Needle Clusters on Highly Active TiO2 Thin Film

AbstractHierarchical gold (Au) structures with sharp edges garner a strong interest for nanoelectronics, nanoenergy harvesting devices, and nano‐biomedical applications due the exceptional strong electric field (hot spot) enhancement at their tips. Herein, a facile method to synthesize hierarchical Au needle clusters (HAuNCs) on highly active titanium oxide (TiO2) thin film is reported. Different from surfactant‐directed photochemical‐assisted synthesis methods, a photocatalytic deposition approach is demonstrated, which allows positioning and patterning of HAuNCs on TiO2 target without using any surfactant or stabilizer. This green synthesis approach enables to control the size and the geometry of deposited HAuNCs by simply altering the photocatalytic activity of TiO2 target, UV light intensity, and irradiation time.

UV-LEDs floating-bed photoreactor for the removal of caffeine and paracetamol using ZnO supported on polystyrene pellets

In this paper a UV-LEDs floating photocatalytic reactor was developed in order to remove caffeine and paracetamol from water using ZnO immobilized on low density macroscopic polystyrene pellets as floating photocatalyst. Different amounts of ZnO were immobilized on polystyrene pellets surface by solvent casting method and characterized from chemical-physical point of view using N2 adsorption at -196 °C, SEM analysis and XRD technique. Photocatalytic activity results evidenced that, during the irradiation time, the photocatalytic performances with the floating-bed reactor were strongly enhanced with respect to the fixed-bed reactor. The influence of process parameters, such as ZnO amount immobilized on polystyrene pellets, air flow rate and UV light intensity, has been investigated. The results showed that the complete caffeine degradation with a mineralization degree of about 86% was achieved after 240 min of UV irradiation at ZnO loading on polystyrene pellets of 1.1 wt%, air flow rate of 144 Ncc·min−1 and UV light intensity of 13 W·m−2. Furthermore, the optimized photocatalyst can be reused for several cycles without any substantial decrease of photocatalytic performances. Finally, the floating photocatalyst was able to remove simultaneously paracetamol and caffeine from drinking water with a very good efficiency.

Benzothienobenzothiophene/polyimide blend-based organic phototransistors with double-layer gate dielectric

Abstract Herein, we report on the double-layer gate dielectric effects on organic phototransistors (OPTs) based on 2,7-dipentyl[1]benzothieno[3,2-b][1]benzothiophene (C5-BTBT)/polyimide (PI) blends as channel materials. The content of C5-BTBT in a blend was varied from 90 to 10 wt.%. We fabricated OPTs with double-layer gate dielectric composed of PVP/pMSSQ (denoted as XD) and SiO2 dielectrics. The introduction of the XD layer enabled shifting of the threshold voltage to more positive values of the gate voltage, eliminated hysteresis in the dark, and suppressed the hysteresis under UV light illumination. In addition to effects of the double-layer gate dielectric, it was found that the best performance of OPTs was achieved with a very low content of C5-BTBT in the blend (20 wt.%). Under UV light intensity of 3 mW cm−2, 20:80 C5-BTBT:PI OPTs exhibited the highest photosensitivity (107) and photoresponsivity (67 A W−1) with negligible hysteresis. Evaluation of the photoresponsivity as a function of light intensity revealed that OPTs maintained the high photosensitivity of 107 even under the weak UV light intensity of 0.11 mW cm−2. The dynamic characteristics of OPTs were affected by the XD dielectric layer, the content of PI and the source-drain voltage. The decay times of the persistent photocurrent (the photo memory) were longer for OPTs with the double-layer gate dielectric, higher content of the PI, and at the low source-drain voltage of −0.1 V. The OPTs have potential application as photo memory elements with low operating source-drain voltage and multilevel programming/controlling of their performance.

Investigation of photocatalytic degradation of BTEX in produced water using γ-Fe2O3 nanoparticle

Among different methods for produced water treatment, photocatalytic process is an alternative and innovative technology that is more used in water treatment. In this work BTEX was used as an indicator of produced water. γ-Fe2O3 nanoparticles have been synthesized via co-precipitation methods. XRD, DRS, FTIR and SEM techniques have been employed for detecting the particle size, morphology, different functional groups, the optical absorption characteristics and the crystal structure of the synthesized nanoparticle. Experimental tests were designed by the OFAT method. The effective ranges of the main factors on the photocatalytic degradation of BTEX including pH (3–7), catalyst concentration (0–250 mg L−1), UV light intensity (0–100 W) and visible light intensity (0–225 W) were obtained. When maghemite nanoparticles are under visible light and UV light, the best removal efficiency achieved 95% in 5 days and 97% in 90 min, respectively. In addition the photocatalytic process, adsorption and photolysis process of maghemite nanoparticles were studied.

EVALUATION OF PHOTO-FENTON DEGRADATION OF REACTIVE BLACK 5 USING RESPONSE SURFACE METHOD

Photo-Fenton degradation of a reactive dyestuff, Reactive Black 5, was investigated in this study. The effects of UV light on Fenton Reagent process and the influence of reagents dosage, UV light intensity and initial dissolved oxygen concentration on photo-Fenton were explored. The experiments were conducted in a 3-L batch-mode reactor and were designed using Response Surface Method. The performance of the systems was assessed based on TOC removal. UV light was found to increase the efficiency of Fenton Reagent process by about 100%, reduce the reaction time by half and lessen the iron requirement by about 85%. Within the range used in the experiments, UV light intensity, and iron and hydrogen peroxide dosages were found to have significant positive influence on the efficiency of the photo-Fenton process. Iron dosage was significant in the early stage, peroxide dosage was significant at the later stage while UV light intensity was significant throughout the reaction period. The initial dissolved oxygen concentration was not a significant factor for photo-Fenton. Depending on the conditions of the reaction, TOC removal of 41.3% to 88.2% was obtained by photo-Fenton oxidation after 30 minutes.

Nanoparticle for degradation of BTEX in produced water; an experimental procedure

BTEX are the most aromatic hydrocarbons in produced water. Due to hazardous effects of BTEX on environment and to human health, different methods were applied for produced water treatment. One of these methods is nanophotocatalytic process. In this paper for the first time, maghemite nanoparticles were used to remove the pollutants. Maghmite was synthesized by wet chemical method as semiconductor photocatalysis. The synthesized nanoparticles were characterized by Diffuse Reflectance Spectroscopy (DRS), X-ray diffraction analysis technique and scanning electron microscope (SEM). The impact of the main factors including pH (3–7), catalyst concentration (0–250 mg/l) and UV light intensity (0–100 W) were studied. Response surface methodology was utilized to apply and optimize the experiments and results. From the analysis of the results the equation of quadratic polynomial model was obtained. R2 and R2adj for the model were 0.94 and 0.88 respectively, which indicate the model matches the experimental data. Outputs reveal that the best removal efficiency of BTEX (82%) was observed in 90 min at pH = 3, nanoparticle concentration = 170 mg/l, and UV light intensity = 100 W.

Bacteriophage cocktail for biocontrol of Escherichia coli O157:H7: Stability and potential allergenicity study.

Escherichia coli O157:H7 has become a global public health and a food safety problem. Despite the implementation of control strategies that guarantee the safety in various products, outbreaks persist and new alternatives are necessary to reduce this pathogen along the food chain. Recently, our group isolated and characterised lytic bacteriophages against E. coli O157:H7 with potential to be used as biocontrol agents in food. To this end, phages need certain requirements to allow their manufacture and application. The aim of this study was to determine the physical stability and allergenic potential of free and microencapsulated (ME) bacteriophage cocktails against E. coli O157:H7. In vitro and in vivo studies were performed to determine phage survival under different pH, gastrointestinal conditions, temperature and UV light intensities. Results showed that the stability of ME phages was significantly (P<0.05) higher than free phages after ultraviolet irradiation, pH conditions between 3 to 7, and exposure to temperatures between at -80°C and 70°C. Both formulations were highly sensitive to very low pH in simulated gastric fluid, but stable in bile salts. In vivo studies in mice confirmed these phages passed through the gastrointestinal tract and were excreted in faeces. In silico, full-length alignment analysis showed that all phage proteins were negative for allergenic potential, but different predicting criteria classified seven phage proteins with a very low probability to be an allergen. In conclusion, these data demonstrated that microencapsulation provided a greater stability to phage formulation under stress conditions and assure a more suitable commercial formulation for the biological control of E. coli O157:H7.

Application of the Real-Time Time-Dependent Density Functional Theory to Excited-State Dynamics of Molecules and 2D Materials

We review our recent developments in the ab initio simulation of excited-state dynamics within the framework of time-dependent density functional theory (TDDFT). Our targets range from molecules to 2D materials, although the methods are general and can be applied to any other finite and periodic systems. We discuss examples of excited-state dynamics obtained by real-time TDDFT coupled with molecular dynamics (MD) and the Ehrenfest approximation, including photoisomerization in molecules, photoenhancement of the weak interatomic attraction of noble gas atoms, photoenhancement of the weak interlayer interaction of 2D materials, pulse-laser-induced local bond breaking of adsorbed atoms on 2D sheets, modulation of UV light intensity by graphene nanoribbons at terahertz frequencies, and collision of high-speed ions with the 2D material to simulate the images taken by He ion microscopy. We illustrate how the real-time TDDFT approach is useful for predicting and understanding non-equilibrium dynamics in condense...

An estimation methode for measurement of ultraviolet radiation during nondestructive testing

Dye penetrant testing and magnetic particle testing are among conventional NDT methods. For increased sensitivity, fluorescence dyes and particles can be used with ultraviolet (black) lights. UV flaw detection lights have different spectra. With the help of photo-filters, the output lights are transferred to UV-A and visible zones. UV-A light can be harmful to human eyes in some conditions. In this research, UV intensity and spectrum were obtained by a Radio-spectrometer for two different UV flaw detector lighting systems. According to the standards such as ASTM E709, UV intensity must be at least 10 W/m2 at a distance of 30 cm. Based on our measurements; these features not achieved in some lamps. On the other hand, intensity and effective intensity of UV lights must be below the some limits for prevention of unprotected eye damage. NDT centers are usually using some type of UV measuring devices. A method for the estimation of effective intensity of UV light has been proposed in this research.