Increase In UV Dose Research Articles

Synthesis and optical characterization of Dy3+ doped barium alumino silicate phosphor

The present article reports the photoluminescence, thermoluminescence and mechanoluminescence behavior of Ba2Al2SiO7: xDy3+ (x = 1–4 mol%) phosphor synthesized via solid-state reaction method. X-Ray powder diffraction technique was used to confirm the phase purity and calculate the average crystallite size. Photoluminescence studies show intense peaks in blue and yellow region, which attributes to 4F9/2→6H15/2 and 6H13/2 transition of Dy3+ respectively and optimum intensity in the photoluminescence emission spectra was found to be at 2 mol% concentration of Dy3+. From the TL glow curve trapping parameter; like activation energy and frequency factor were calculated and it is noticed that TL intensity vary linearly with UV dose up to 15 min of exposure time. Mechanoluminescence studies depicts that, ML intensity increases both with increase in UV dose and height of piston. This suggest that the prepared phosphor may act as a potential candidate for low UV dosimetry and damage sensor.

What happens with organic micropollutants during UV disinfection in WWTPs? A global perspective from laboratory to full-scale

The phototransformation of 18 organic micropollutants (OMPs) commonly detected in wastewater treatment plant (WWTP) effluents was examined attempting to explain their fate during UV disinfection in WWTPs. For this purpose, a lab-scale UV reactor (lamp emitting at 254nm) was used to study the influence of the operational conditions (UV dose, temperature and water matrix) on OMPs abatement and disinfection efficiency. Chemical properties of OMPs and the quality of treated effluent were identified as key factors affecting the phototransformation rate of these compounds. Sampling campaigns were carried out at the inlet and outlet of UV systems of three WWTPs, and the results evidenced that only the most photosensitive compounds, such as sulfamethoxazole and diclofenac, are eliminated. Therefore, despite UV treatment is an effective technology to phototransform OMPs, the UV doses typically applied for disinfection (10–50mJ/cm2) are not sufficient to remove them. Consequently, small modifications (increase of UV dose, use of catalysts) should be applied in WWTPs to enhance the abatement of OMPs in UV systems.

Thermally Stimulated Luminescence of $$\hbox {Y}_{2}{\mathrm {Si}}{\mathrm {O}}_{5}{:}~{\mathrm {Ce}}^{3+}$$ Y 2 Si O 5 : Ce 3 + Commercial Phosphor Powder and Thin Films

We report on the thermoluminescence (TL) properties of $$\hbox {Y}_{2}{\mathrm {Si}}{\mathrm {O}}_{5}{:}\,{\mathrm {Ce}}^{3+}$$ phosphor powder and thin films. For the phosphor powder, the TL intensity increases with an increase in UV dose for up to 20 min and then decreases. The TL intensity peak shifts slightly to higher-temperature region at relatively high heating rates, but with reduced peak intensity. Important TL kinetic parameters, such as the activation energy (E) and the frequency factor (s), were calculated from the glow curves using a variable heating rate method, and it was found that the glow peaks obey first-order kinetics. For the films, broad TL emissions over a wide temperature range with reduced intensity relative to that of the powder were observed. The maxima of the TL glow peaks of the films deposited in oxygen ambient and vacuum shift toward higher temperature relative to the TL peak position of the film deposited in an argon environment. Vacuum environment resulted in the formation of a deep trap relative to oxygen and argon environments. Furthermore, the structure of $$\hbox {Y}_{2}{\mathrm {Si}}{\mathrm {O}}_{5}{:}\,{\mathrm {Ce}}^{3+}$$ phosphor powder transformed from $${x}_{2}$$ -monoclinic polycrystalline phase to $${x}_{1}$$ -monoclinic polycrystalline phase, for deposition at low substrate temperature.

Formation of iodinated trihalomethanes during UV/chloramination with iodate as the iodine source

Iodinated trihalomethanes (I-THMs) are a group of emerging disinfection by-products with high toxicity, and iodide (I−) as well as iodinated organic compounds are expected to be their iodine sources. Nevertheless, in this study, iodate (IO3−) was proven to be a new iodine source of I-THM formation during UV/chloramination. In the iodate-containing waters (without any other iodine sources), I-THM formation increased with the increase of UV dose, IO3− and NH2Cl concentrations. With the increase of Br−/IO3− molar ratio, I-THM formation (especially for the brominated species) increased. Besides, NOM species could affect I-THM formation from IO3− during UV/chloramination. Fulvic acid could promote IO3− phototransformation to I− but humic acid impeded the production of I− during UV irradiation. Under realistic drinking water treatment conditions (DOC = 5.0 mg-C/L, IO3− = 12.7 μg-I/L, UV dose = 50 mJ/cm2, NH2Cl = 5 mg-Cl2/L), CHCl2I was detected as 0.17 μg/L using solid-phase microextraction method, and the production rate of I-THMs from IO3− was about 7% of that from I−.

The pulsed light inactivation of veterinary relevant microbial biofilms and the use of a RTPCR assay to detect parasite species within biofilm structures.

The presence of pathogenic organisms namely parasite species and bacteria in biofilms in veterinary settings, is a public health concern in relation to human and animal exposure. Veterinary clinics represent a significant risk factor for the transfer of pathogens from housed animals to humans, especially in cases of wound infection and the shedding of faecal matter. This study aims to provide a means of detecting veterinary relevant parasite species in bacterial biofilms, and to provide a means of disinfecting these biofilms. A real time PCR assay was utilized to detect parasite DNA in Bacillus cereus biofilms on stainless steel and PVC surfaces. Results show that both Cryptosporidium and Giardia attach to biofilms in large numbers (100-1000 oo/cysts) in as little as 72 hours. Pulsed light successfully inactivated all test species (Listeria, Salmonella, Bacillus, Escherichia) in planktonic and biofilm form with an increase in inactivation for every increase in UV dose.

Research on Influencing Factors of Photoreactivation in Urban Sewage Treatment by UV Disinfection

Test using CS-type UV sterilizer to do experimental study on the urban sewage , mainly research the influence of the placement time under natural light and the UV dose on photoreactivation. The results show that when disinfection ultraviolet dose is equal, bacteria photoreactivation phenomenon is more obvious with the increase of the placement time of water samples under natural light . When the placement time reaches at 3h, bacteria photoreactivation phenomenon is the most obvious. Under the same placement time, the ratio of bacteria photoreactivation decreases gradually with the increase of UV dose. When UV dose reaches at 80mJ /cm2 or the higher doses, the bacteria does not basically happen photoreactivation phenomenon. Photoreactivation phenomenon in E. coli is more obvious than that in bacteria under the same conditions.

UV- and thermal-curing behaviors of dual-curable adhesives based on epoxy acrylate oligomers

Dual-curable adhesives were prepared using various epoxy acrylate oligomers, a reactive diluent, photoinitiators, a thermal-curing agent and a filler. The UV- and thermal-curing behaviors of the dual-curable adhesives were investigated using photo-differential scanning calorimetry (photo-DSC), Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, and the determination of the gel fraction, pendulum hardness and adhesion strength. The reaction rate and extent of UV curing were found to be strongly dependent on the concentration of C C bonds in the epoxy acrylate oligomers. The FTIR-ATR absorption peak areas representing the relative concentration of C C bonds in the epoxy acrylate oligomers and trifunctional monomer decreased with increase in UV dose because of photopolymerization. When the dual-curable adhesives were irradiated with UV light, the gel fraction increased with increase in C C bond contents in the epoxy acrylate oligomers. Also, after thermal curing, the gel fraction was highly enhanced due to the cross-linking reaction of the unreacted glycidyl groups in epoxy acrylate oligomers induced by the thermal-curing agent. This cross-linked structure of the dual-curable adhesives affects the pendulum hardness and adhesion strength.

Intrinsic thermoluminescence of nacl:Tl in uv dosimetry

Abstract NaCl:Tl(T) phosphor is found to have high intrinsic thermoluminescence (TL) sensitivity to 253.7 nm UV-radiation. The dosimetric glow peak II grows sublinearly with increase in UV dose in the range 103-106 JM−2. The other requirements of an efficient dosimeter material such as high storage stability, matching of the spectral response of detector tube and TL-emission from phosphor, reproducibility, desirable size and shape, easy availability in powder, pellet and crystal forms at cheaper rates, and repeated re-usability of the same phosphor without much difficulty, etc., are additional factors which strengthen the claim of NaCl:Tl(T) phosphor as UV dosimetric material. It is proposed that present NaCl:Tl(T) material is suitable TL-phosphor for UV dosimetry in the range 103-106 JM−2.