Effect Of Irradiation Intensity Research Articles

Effect of irradiation intensity on the rate of photocatalysis of TiO2 coatings obtained by detonation spraying

AbstractThe influence of UV irradiation intensity on the rate constant of photocatalytic reaction of TiO2 coatings applied by detonation spraying on the hot‐rolled carbon steel and glass‐cloth‐base laminate (plastic) is studied. The effect of substrate material on the studied phenomenon is pronounced. The kinetic curves at different UV irradiation intensities and the rate constants of the photocatalytic reaction are obtained for different values of energy flux density varied from 3.0 to 8.0 mW/m2. The photocatalytic rate constant of coatings placed on plastic increases with an increase in the energy flux density from.038 to.055 1/h. Samples applied at a spray distance of 50 mm are characterized by a higher the photocatalytic rate constant than those applied at a distance of 40 mm. The value of photocatalytic rate constant does not change starting from a certain flow value for such samples and reaches the saturation value of about.054 1/h. Saturation is achieved quite quickly already at a density flux of about 5.5 mW/m2. Two new phenomenological models based on differential equation, the analytical solutions to which sufficiently describe experimental dependence of the photocatalytic rate constant on the energy flux density, are proposed.

Using high frequency and low-intensity ultrasound to enhance activated sludge characteristics

In this study, high-frequency ultrasound wave (1.8 MHz) at low intensity was applied to improve activated sludge settleability at high MLSS concentration. The effect of irradiation intensity, sonication mode, MLSS concentration and sample volume on the physical characteristics of sludge in a pilot scale settling column were investigated for optimizing the conditions. The obtained results showed that high-frequency ultrasound decreased the height of sludge (44%) and effluent turbidity (82.2%) and increased sludge settling velocity about 3 times at high biomass concentration. Irradiation intensity of 0.4 w/cm2 and sonication mode with interval times of 10 s showed the best results on the performance of the system at MLSS concentration of 8000 mg/L with a sample volume of 3 L.

Degradation of diethyl phthalate (DEP) by vacuum ultraviolet process: influencing factors, oxidation products, and toxicity assessment.

The vacuum ultraviolet (VUV) process, which can directly produce hydroxyl radical from water, is considered to be a promising oxidation process in degrading contaminants of emerging concern, because of no need for extra reagents. In this study, the influencing factors and mechanism for degradation of diethyl phthalate (DEP) by the VUV process were investigated. The effects of irradiation intensity, inorganic anions, natural organic matter (NOM), and H2O2 dosage on the performance of VUV process were evaluated. The results showed that DEP could be more efficiently degraded by the VUV process compared with ultraviolet (UV)-254-nm irradiation. The presence of HCO3-, NO3- and NOM in the aqueous solutions inhibited the degradation of DEP to a different degree, mainly by competing hydroxyl radicals (HO•) with DEP. Degradation rate and removal efficiency of DEP by VUV process significantly enhanced with the addition of H2O2, while excess H2O2 dosage could inhibit the DEP degradation. Moreover, based on the identified seven oxidation byproducts and their time-dependent evolution profiles, a possible pathway for DEP degradation during the VUV process was proposed. Finally, the ecotoxicity of DEP and its oxidation byproducts reduced overall according to the calculated results from Ecological Structure Activity Relationships (ECOSAR) program. The electrical energy per order (EE/O) was also assessed to analysis the energy cost of the DEP degradation in the VUV process. Our work showed the VUV process could be an alternative and environmental friendly technology for removing contaminants in water.

Hyperbranched polypeptides synthesized from phototriggered ROP of a photocaged Nε-[1-(2-nitrophenyl)ethoxycarbonyl]-l-lysine-N-carboxyanhydride: microstructures and effects of irradiation intensity and nitrogen flow rate

A new photocaged amino acid monomer Nε-(1-(2-nitrophenyl)ethoxycarbonyl)-l-lysine-N-carboxyanhydride (NPE-Lys NCA) was designed to directly synthesize hyperbranched polypeptides by phototriggered ROP.

Effect of irradiation intensity and initial pollutant concentration on gas phase photocatalytic activity of TiO2 nanotube arrays

Well-organized TiO2 nanotube arrays were fabricated via one-step anodization process. The as-prepared TiO2 nanotubes were characterized by X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM). Photocatalytic activity of obtained photocatalyst was studied in reaction of toluene degradation in the gas phase using low powered and low cost light-emitting diodes (UV LEDs) as an irradiation source. The effect of irradiation intensity and initial pollutant concentration on gas phase photoactivity of TiO2 nanotubes was analyzed. Obtained TiO2 nanotubes were smooth and vertically oriented with a length of about 1.7±0.05μm. The inner diameter and the wall thickness were 65±2nm and 6±0.4 nm, respectively. The results showed that the initial toluene degradation rate increased (from 0.0062 up to 0.0567μmol/min) with raising initial toluene concentration (50–400ppm), while too high dose of irradiation (about 50mW/cm2) reduced photocatalytic toluene degradation rate. The best stability of TiO2 nanotubes in three subsequent irradiation cycles was observed for irradiation intensity of 38mW/cm2. Moreover, it was found that photocatalytic toluene degradation over TiO2 nanotubes showed first order kinetic behavior.

Effect of irradiation intensity on rate and selectivity of photosensitized oxidation of dibutyl sulfide over C70 fullerene

Photoinitiated oxidation of dibutyl sulfide (DBS) with air oxygen in a toluene solution of C70 fullerene during irradiation with visible light at a wavelength of 500–700 nm results in the formation of dibutyl sulfone as a main detected product, dibutyl sulfoxide, and butanal. A change in the intensity of radiation incident on the reaction mixture from 2.2 to 44 mW/cm2 insignificantly increases the quantum efficiency of the DBS consumption from 4.5 to 5.9%. The selectivity for sulfoxide increases during the process, while selectivity for sulfone decreases.

Kinetic study of the poly(vinyl chloride)/titanium dioxide nanocomposites photodegradation under accelerated ultraviolet and visible light exposure

In the present study, poly(vinyl chloride)/titanium dioxide (PVC/TiO2) nanocomposite films containing different amounts of synthesized TiO2 nanoparticles and commercial rutile powder were irradiated for 5112 hr, under exposure of artificial ultraviolet and visible lights in three different intensities. The rate of degradation was determined by using weight loss data and was found to follow a pseudo-first order kinetic model. To determine the overall rate constant of degradation, k, a possible mechanism of the photodegradation was considered. The rate equation demonstrated k as a function of TiO2 concentration and irradiation intensity at each wavelength. The overall rate constant of PVC/TiO2 samples were calculated to be varied in the range of 6–16 × 10−7 hr−1, at all investigated conditions. The kinetic study represented that by adding synthesized TiO2 nanoparticles, even at low content, and with increasing their concentration, the photodegradation rate of nanocomposites decreased considerably compared with the composite samples. Likewise, by adding nanoparticles, a significant increase in the nanocomposites lifetime was achieved. The effect of irradiation intensity was investigated according to the reciprocity law experiments, and it was found that photodegradation occurred in two regimes with respect to irradiation intensity. The calculated overall rate constants were validated by the experimental data. Copyright © 2014 John Wiley & Sons, Ltd.

Effects of Irradiation Intensity and pH on Nutrients Release and Solids Destruction of Waste Activated Sludge Using the Microwave‐Enhanced Advanced Oxidation Process

Using the microwave-enhanced advanced oxidation process (MW/H2O2-AOP), the pH and irradiation intensity on waste activated sludge samples were investigated to provide insight to the athermal effects on nutrients release, solids destruction, particle size distribution and dewaterability, and to demonstrate their interrelationships. Carbonaceous matters and nutrients released into solution depended on the irradiation intensity and time. Higher irradiation levels tended to be more effective in the solubilization of nutrients and had more pronounced effects in the dewaterability of sludge. In terms of particle size distribution, detectable particles increased in size for treatments in acidic conditions, while the dewaterability of treated sludge was improved. In treatments under neutral and alkaline conditions, the particle size range increased, with more small particles formed, thereby significantly deteriorating the dewaterability of sludge treated in alkaline conditions. The best results for the solubilization of nutrients were in alkaline conditions with high irradiation power, but dewaterability of the sludge was compromised. Sludge treatment with the MW/H2O2-AOP in acidic conditions with high irradiation power yielded the best dewaterable sludge and significant nutrient solubilization; therefore, it is the recommended treatment condition for activated sludge.

The effects of irradiation intensity on the microwave-enhanced advanced oxidation process

The microwave enhanced advanced oxidation process (MW/H2O2-AOP) was adopted in successfully treating a multitude of organic slurries. The factor of ramp rate was incorporated in this study to investigate its correlations with different nutrients release into solution from waste activated sludge. Besides the ramp rate, the amount of time the samples were held at the treatment temperature to a total of 10 minutes aided in the isolation of held temperature from ramp rates, since different ramp rates will yield different reaction times. It was found that with the exception of orthophosphate and chemical oxygen demand release, ammonia and volatile fatty acids depended highly on the ramp rates. All constituents, chemical oxygen demand, orthophosphate, ammonia and volatile fatty acids, solubilized better with longer reaction times coupled with the highest ramp rate. Besides treatment time and ramp rates, treatment temperature and hydrogen peroxide dosage also play important roles in the release of various nutrients into solution by the MW/H2O2-AOP. The results from this study can aid in design parameters for the scaling up of a continuous microwave system for the MW/H2O2-AOP.

Effect of irradiation intensity on cell growth and kalata B1 accumulation in Oldenlandia affinis cultures

Light irradiation had remarkable effects on callus growth of Oldenlandia affinis with an optimum intensity of 35 μmol m−2 s−1. Biosynthesis of kalata B1, the main cyclic peptide in O. affinis, was induced and triggered with rising irradiation intensities. The highest concentration of kalata B1, 0.49 mg g−1 DW characterised by the maximum productivity of 3.88 μg per litre and day was analysed at 120 μmol m−2 s−1, although callus growth was repressed. The light saturation point was established to be 35 μmol m−2 s−1, where kalata B1 productivity was in a similar order (3.41 μg per day) due to the higher growth index. O. affinis suspension cultures were shown to accumulate comparable specific kalata B1 concentrations in a delayed growth associated production pattern. These were dependent on irradiation intensity (0.16 mg g−1 at 2 μmol m−2 s−1; 0.28 mg g−1 at 35 μmol m−2 s−1). The batch cultivation process resulted in a maximum productivity of 27.30 μg per litre and day with culture doubling times of 1.16 d−1. Submers operation represented a 8-fold product enhancement compared to callus cultivation.

Effect of irradiation intensity on the isothermal photopolymerization kinetics of acrylic resins for stereolithography

Three dimensional objects are built without the use of molds with a new technology called stereolithography. The objects are obtained in an additive way polymerizing under a laser beam a low viscosity liquid resin section by section. The kinetic behaviour of the resin represents a key point for a full comprehension of the cure condition occurring in the small zone exposed to laser irradiation. In this work, the isothermal kinetic behaviour of a commercial acrylic resin for stereolithography is analyzed by differential photocalorimetric analysis. A kinetic model, accounting for the effect of autoacceleration, vitrification and light intensity on the reaction kinetics is presented. In particular, the effect of irradiation intensity on the model parameters is studied correlating the kinetic constant and the final chemical conversion with the light intensity and with a characteristic time scale of the reaction.

Effect of irradiation intensity on luminescence quenching kinetics in micellar systems

A stochastic model for luminescence quenching in monodisperse micellar systems is treated without any restriction on the intensity of irradiation. Both time-resolved and steady-state observables are calculated. It is found that the luminescence intensity is given by the convolution product of the sample response function of the system corresponding to the δ-pulse excitation and the instrument response function only in the limit of low excitation efficiency. It is shown that one of the basic assumptions of the original stochastic model that a micelle should contain at most one excited probe is not necessary provided intramicellar quenching follows pseudo-first-order kinetics.

Photopolymerization of methyl methacrylate and 2-(dimethylamino) ethyl methacrylate induced by diacetoxyiodobenzene in the presence of radical inhibitors

Summary Polyvalent iodine compounds such as diacetoxyiodobenzene, (CH3COO) 2IC6H 5 (DAI), and bis(trifluoroacetoxy) iodobenzene, (CF3COO)2IC6H 5 (BTI), are efficient initiators of cationic and radical polymerizations. To confirm the radical mechanism of DAI-induced polymerization of methyl methacrylate (MMA) and 2(dimethylamino)ethyl methacrylate (DMAEMA), a study has been performed in the presence of the radical inhibitor 2,3,5,6tetrachloro-p-benzoquinone (TCQ) and its complex with triethylamine (TEA). The polymerization kinetics and the effect of irradiation intensity have been studied.

The radiation damage process in MgF2

F centre production by ionizing radiation in MgF2 has a character which changes markedly with temperature; below approximately 50K and above approximately 200K essentially unsaturating defect production occurs while between approximately 50K and approximately 200K the concentration of F centres quickly saturates. Detailed measurements of the effect of irradiation intensity at 5K, 80K, and 300K have been made, together with measurements at constant intensity as a function of temperature. These results are interpreted in terms of a model in which the radiation creates close pairs of F centres and H centres which are stable at low temperatures, recombine at intermediate temperatures and dissociate at higher temperatures. Other evidence is presented for this model, including the fact that the observed F band is rather wider for F centres created at 5K than for centres created at 300K and measured at 5K.

On the effect of irradiation intensity on defect production in pure and iodine‐doped KCl at room temperature

AbstractA study was made of the room temperature coloration of pure and iodine‐doped KCl. Various intensity‐dependent effects were observed. These include the nature of the V bands as well as the shape of the F growth curve.

Effect of X-Ray Intensity on the Production of Color Centers in NaCl and KCl

The results of a study of the effect of irradiation intensity on the coloration of NaCl and KCl are reported. Three observations stand out: (1) The equilibrium established between F and complex certers shifts to favor F centers with increasing intensity of irradiation. Cycling of the irradiation intensity between low and high values complex centers. (2) The density of F centers produced by uv irradiation of a crystal following optical bleaching of a prior x irradiation, increases with the intensity of the prior x irradiation. The density of uv-produced F centers could also be shifted in a reversible manner on cycling the intensity of x irradiation. (3) The intensity dependence of the F- center growth curves is present only at irradiation temperatures above 200 deg K. It is proposed that the intensity dependence of the F-center coloration arises from the establishment of a balance between two competing processes. It is proposed that the primary effect of x-ray photons is to disperse single vacancies in the crystal. Competing with this dispersal is the tendency of the anion vacancies to reaggregate by the diffusion of mobile vacancy units. (auth)

EyeIrritationfrom IrradiatedAutomobile Exhaust (Effect of Irradiation Intensity; Half-Life Studies)

Two series of experiments were carried out on automobile exhaust. The first measured effects of varied irradiation intensities on eye irritation and on the extent of the photochemical reaction of the oxidant and nitrogen dioxide content of an exhaust-air mixture. The second series determined the half life of th eye irritant, as indicated by the averaged, weighted reports of eye irritation in human experiment subjects. Both the reported degree of eye irritation the values of oxidant and nitrogen dioxide in the exhaust-air mixtures were found to vary directly with irradiation intensity. The half life of the eye irritant was found to be about 24 hours, as measured by a panel of 10 human subjects. The decay rates of the oxidant and nitrogen dioxide under static state conditions were shown to be direct functions of time. 7 references, 8 figures, 2 tables.