Mercury UV Lamp Research Articles

Comparison of the performance of pulsed and continuous UVC-LED irradiation in the inactivation of bacteria

Ultraviolet light-emitting diode (UV-LED) is a newly emerging UV light source with a potential to replace the conventional chemical methods, mercury UV lamps and xenon lamps in water disinfection. UV-LEDs are characterized by the diversity in wavelengths and can be turned on and off with a high and adjustable frequency, making them an attractive candidate for pulsed light (PL) disinfection apart from the conventional continuous wave (CW) operation. Previous studies on comparison between the PL and CW UV-LED irradiations for the inactivation of bacterium in water disinfection are limited and results conflict. In this work, PL and CW UV-LED in the C-spectral band (UVC-LED) irradiations were compared at equivalent fluence in the inactivation and subsequent photoreactivation of E. coli bacteria. In addition, effect of different driving currents and ambient temperatures on solder temperature of the PL and CW UVC-LED irradiation was also examined. Under the equivalent fluences, the PL and CW UVC-LED irradiations brought comparable inactivation efficiency and similar photoreactivation of the E. coli. Moreover, the PL UVC-LED exhibited a much lower solder temperature than the CW UVC-LED irradiation. On the other hand, CW UVC-LED irradiation, higher ambient temperature and higher driving current increased the solder temperature that resulted to a negative impact on the wavelength, full width at half maximum, optical power and irradiance, which are key factors in the UVC-LED disinfection efficiency. In all, this work reports the comparison between PL and CW in UVC-LED irradiation for inactivating E. coli bacteria and firstly revealed the photoreactivation of the E. coli after the PL UVC-LEDs irradiation.

Oxidation and molecular properties of microcystin-LR, microcystin-RR and anatoxin-a using UV-light-emitting diodes at 255 nm in combination with H2O2

On the use of UV light emitting diodes (UV-LEDs), emitting at 260–290 nm, has attracted attention for treating cyanotoxins, although most previous studies related with UV/H2O2 process have been used conventional mercury UV lamp (λ = 254 nm). Therefore, the aim of the study was to investigate the UV-LEDs, having a wavelength of 255 nm, coupled with H2O2 process for the removal of microcystin-LR (MC-LR), microcystin-RR (MC-RR), and anatoxin-a (ANTX) and to verify the degradation kinetics, mechanism and impact of water quality parameters in relation to their molecular properties. Among three UV-LEDs (λ = 255, 266, and 280 nm), the shortest one was the most effective to remove MC-LR coincided with its decadic molar absorption coefficient. The degradation rate constants of MC-LR, MC-RR, and ANTX were 0.0644, 0.0241, and 0.0076 cm2 mJ−1, respectively, during the UV-LED/H2O2 process. For MC-LR and MC-RR degradation, reaction with OH is a major mechanism along with direct photolysis as a minor factor. ANTX degradation is predominantly attributed to OH. The second-order rate constant for ANTX is one order of magnitude lower than others because ANTX is recalcitrant to oxidation. The MC-LR degradation occurred at the diene and aromatic ring of Adda, Mdha, and amide bond and the main reactive oxidation site of MC-RR was the Adda chain. In contrast, photo-oxidation transformed ANTX to higher molecular weight compounds via polymerization instead of degradation. When MC-LR, MC-RR, and ANTX were co-present, lower concentration of dissolved organic carbon and higher acidity with bicarbonate was favorable to remove MC-LR and MC-RR according to their scavenging factors and reaction with CO−3. However, ANTX is relatively resistant to degradation at pH 3.2.

Application of a novel, continuous-feeding ultraviolet light emitting diode (UV-LED) system to disinfect domestic wastewater for discharge or agricultural reuse

In many low-income countries, the poor conditions of sanitation systems have been a significant cause of mortality since they accelerate waterborne disease transmission. Developing sanitation systems in these countries is a pressing concern in both the public and private sectors.This research investigated a decentralized domestic wastewater treatment system using ultraviolet light-emitting diodes (UV-LEDs). Although UV-LED disinfection has become more widespread in recent years, it is a novel approach for domestic wastewater treatment. Domestic wastewater was pretreated by a low-cost pretreatment system with an inclined settler and a sand filter prior to feeding a novel flow-through UV LED reactor. At an inlet flow rate of 30 L/h, the COD, TSS, and turbidity of the effluent were 17.7 mg/L, 3.0 mg/L, and 3.9 NTU, respectively. UV transmittance at 285 nm was enhanced from 29.1% to 70.4%, improving the influent quality for UV LED disinfection.The flow-through UV LED reactor was operated at various flow rates from 10 to 50 mL/min, resulting in applied UV doses of 69.4 to 47.8 mJ/cm2 respectively. These doses are sufficient for inactivating total coliforms in the wastewater to meet the water reuse guidelines for agriculture for both processed food crops and non-food crops.Fouling, which was observed starting at 2 d of operation, decreased the disinfection efficacy to 27% after 25 days of continuous operation. Of the fouling layer, 67% was attributed to organic matter, in contrast to previous fouling studies with mercury UV lamps in which the fouling layer consisted primarily of inorganic compounds. The fouling was reversed by off-line citric acid cleaning for 4 h after every 400 h of continuous operation.

UV‐C treatment on the safety of skim milk: Effect on microbial inactivation and cytotoxicity evaluation

AbstractThe efficacy of UV‐C irradiation as a nonthermal processing method for skim milk (SM) was investigated. SM inoculated with two surrogate viruses (MS2 and T1UV), and three bacteria (Escherichia coli ATCC 25922, Salmonella enterica serovar Typhimurium ATCC 13311, and Listeria monocytogenes ATCC 19115) was treated with Deanflow UV‐C irradiation, a spiral reactor with the fluid pumped around a central low‐pressure mercury UV lamp (40 W) emitting at 254 nm wave‐length. A series of known UV doses (0–168.33 mJ·cm2) were delivered to the samples. The microbial loads of MS2, T1UV, E. coli, Salmonella, and Listeria were reduced by more than 5 log10. The inactivation kinetics of all microorganisms were best described by log linear models with a low RMSE and higher coefficient of determination (R2 > 0.95). This study demonstrated that high levels of inactivation of pathogenic particles can be achieved in SM.Practical applicationsThis scientific study provides evidence based data on the advantages of UV‐C light in achieving microbial reduction in skim milk. The irradiated skim milk did not show any toxicity on mice liver and intestinal cells. UV‐C irradiation is an efficient food preservation technology and offers opportunities for dairy and food processing industries to meet the growing demand from consumers for safer foods. This exploration would provide methodological evidence for commercialization of UV‐C processing of milk and dairy based beverages.

Lateral‐Polarity Structure of AlGaN Quantum Wells: A Promising Approach to Enhancing the Ultraviolet Luminescence

AbstractAluminum‐gallium‐nitride alloys (Al x Ga1– x N, 0 ≤ x ≤ 1) can emit light covering the ultraviolet spectrum from 210 to 360 nm. However, these emitters have not fulfilled their full promise to replace the toxic and fragile mercury UV lamps due to their low efficiencies. This study demonstrates a promising approach to enhancing the luminescence efficiency of AlGaN multiple quantum wells (MQWs) via the introduction of a lateral‐polarity structure (LPS) comprising both III and N‐polar domains. The enhanced luminescence in LPS is attributed to the surface roughening, and compositional inhomogeneities in the N‐polar domain. The space‐resolved internal quantum efficiency (IQE) mapping shows a higher relative IQE in N‐polar domains and near inversion domain boundaries, providing strong evidence of enhanced radiative recombination efficiency in the LPS. These experimental observations are in good agreement with the theoretical calculations, where both lateral and vertical band diagrams are investigated. This work suggests that the introduction of the LPS in AlGaN‐based MQWs can provide unprecedented tunability in achieving higher luminescence performance in the development of solid state light sources.

Identification of intermediates, acute toxicity removal, and kinetics investigation to the Ametryn treatment by direct photolysis (UV254), UV254/H2O2, Fenton, and photo-Fenton processes.

This paper reports the degradation of 10mgL-1 Ametryn solution with different advanced oxidation processes and by ultraviolet (UV254) irradiation alone with the main objective of reducing acute toxicity and increase biodegradability. The investigated factors included Fe2+ and H2O2 concentrations. The effectiveness of the UV254 and UV254/H2O2 processes were investigated using a low-pressure mercury UV lamp (254nm). Photo-Fenton process was explored using a blacklight blue lamp (BLB, λ = 365nm). The UV254 irradiation process achieved complete degradation of Ametryn solution after 60min. The degradation time of Ametryn was greatly improved by the addition of H2O2. It is worth pointing out that a high rate of Ametryn removal was attained even at low concentrations of H2O2. The kinetic constant of the reaction between Ametryn and HO● for UV254/H2O2 was 3.53 × 108Lmol-1s-1. The complete Ametryn degradation by the Fenton and photo-Fenton processes was observed following 10min of reaction for various combinations of Fe2+ and H2O2 under investigation. Working with the highest concentration (150mgL-1 H2O2 and 10mgL-1 Fe2+), around 30 and 70% of TOC removal were reached within 120min of treatment by Fenton and photo-Fenton processes, respectively. Although it did not obtain complete mineralization, the intermediates formed in the degradation processes were hydroxylated and did not promote acute toxicity of Vibrio fischeri. Furthermore, a substantial improvement of biodegradability was obtained for all studied processes.

LED-UV grafting of vinylsulfone dyes onto photo-oxidized wool fabrics

Photografting coloration of wool was carried out under UV-LED irradiation at room temperature using aqueous vinylsulfone dye solution containing vinylsulfonic acid as a comonomer. UV-LED irradiation of the 395 nm emission is more energy efficient, less damaging to the dyes, and much safer to human eyes compared with polychromatic mercury UV lamps. However, in case of the UV-LED lamps, the wool needs to be photo-oxidized either by UV/ozone or polychromatic UV irradiation before the dye photografting. The surface treatments increased the sulfur and oxygen contents in the modified wool surfaces. While the optimally photografted wool fabrics under the UV-LED lamp yielded a K/S value of 9.9, the K/S of the grafted wool increased to 25.2 and 13.6 after the UV/Ozone or polychromatic UV preoxidation at UV energies of 10.6 J/cm2 and 25 J/cm2 respectively. The color fastness properties of the photografted fabrics were far better than with those of the conventionally reactive-dyed fabrics, implying that the high-molecular-weight photografted dyes seemed to be more durable than the low-molecular dyes.

Bactericidal effect of 266 to 279 nm wavelength UVC-LEDs for inactivation of Gram positive and Gram negative foodborne pathogenic bacteria and yeasts

Recently, UVC-LED technology has been validated as an alternative to irradiation with conventional mercury UV lamps. In this study, we sought to determine primary factors affecting reduction trends shown in several microorganisms. Four major foodborne pathogens (Escherichia coli O157:H7, Salmonella spp. Listeria monocytogenes, Staphylococcus aureus) and spoilage yeasts (Saccharomyces pastorianus, Pichia membranaefaciens), important to the brewing industry, were inoculated onto selective and non-selective media in order to investigate reduction tendencies at 4 different peak wavelengths (266 to 279nm). As irradiation dose increased, inactivation levels for every microorganism were enhanced, but there were different UV-sensitivities in Gram positive bacteria (GP), Gram negative bacteria (GN), and yeasts (Y). Loss of membrane integrity measured by propidium iodide (PI) increased as peak wavelength increased for every microorganism studied. Similar results were observed in membrane potential measured by DiBAC4(3). However, there were contrasting results which showed that greater DNA damage occurred at a lower peak wavelength as measured by Hoechst 33,258. The level of DNA damage was strongly related to trends of microbial inactivation. This study showed that even though membrane damage was present in every microorganism studied, DNA damage was the primary factor for inactivating microorganisms through UVC-LED treatment.

UV-LEDs Efficiently Inactivate DNA and RNA Coliphages

UV-LEDs are a new method of disinfecting drinking water. Some viruses are very resistant to UV and the efficiency of UV-LEDs to disinfect them needs to be studied. Drinking water was disinfected with UV-LEDs after spiking the water with MS2 and four UV- and/or Cl-resistant coliphages belonging to RNA or DNA coliphages isolated from municipal wastewater. UV-LEDs operating at a wavelength of 270 nm for 2 min with 120 mW of irradiation caused 0.93–2.73 Log10-reductions of coliphages tested in a reactor of a 5.2 L volume. Irradiation time of 10 min in the same system increased the Log10-reductions to 4.30–5.16. Traditional mercury UV (Hg-UV) lamp at a 254 nm wavelength caused 0.67–4.08 Log10-reductions in 2 min and 4.56–7.21 Log10-reductions in 10 min in 10 mL of water. All coliphages tested except MS2 achieved 4 Log10-reductions with UV-LEDs at a dose that corresponded to 70 mWs/cm2 using Hg-UV. Thus, UV-LEDs are a promising method of disinfecting UV- and/or Cl-resistant viruses.

Characterization of curing behavior of UV-curable LSR for LED embedded injection mold

For many applications, liquid silicone rubber (LSR) injection molding is widely used for their great design flexibility and high productivity. In particular, a sealing part for a mobile device such as smartphone and watch has been produced by injection molding. While thermally curable LSR causes deformation problem due to a high mold temperature, UV-curable LSR can be molded at room temperature, which has advantages for over-molding with inserts of temperature-sensitive materials. Ultraviolet light-emitting diodes (UV LEDs) have advantages such as a longer service life, a lower heat dissipation, and smaller size to equip into the mold than conventional halogen or mercury UV lamps. In this work, rheological behavior of UV-curable LSR during curing process was analyzed by UV LEDs available in the market. UV-LEDs of various wave lengths and intensities were tested. The steady shear test was applied to find the starting time of curing and the SAOS was applied to find the ending time of curing to estimate processing time. In addition, the hardness change with irradiation energy was compared with the rheological data to confirm the reliability of the rheological test.

Impact of natural organic matter on bromate removal in the sulfite/UV-L advanced reduction process

Advanced reduction processes (ARPs) are treatment processes that involve combining reducing reagents and activating tools to produce highly reactive reducing free radicals. The process has proven effective for treating oxidized contaminants, and the effects of process variables on the degradation kinetics of various target contaminants have been investigated in our previous studies. In natural environments, natural organic matter (NOM) is found in surface or ground water. NOM absorbs UV light and can react with photochemically produced radicals, thus affecting target contaminant photochemical reactions and further influencing the efficiency of ARP. This study examines the impact of humic acid (HA) and Suwanee River NOM on bromate reduction rates with UV irradiation using a low-pressure mercury UV lamp. The effects of the sulfite dose, solution pH, and light intensity are studied and the pseudo-first-order rate constants in the presence of HA (kobs,HA) are compared to those observed in the absence of HA (kobs). At low HA concentrations of 1 mg L−1, kobs,HA was larger than kobs; however, kobs,HA was less than kobs at higher HA concentrations. Furthermore, kobs,HA did not increase with increasing sulfite doses in the presence of HA, which is unlike the behavior of kobs.

An integrated on-line method for the preconcentration and simultaneous determination of metsulfuron methyl and chlorsulfuron using oxidized carbon nanotubes and second order fluorescent data

Trace amounts of two sulfonylurea herbicides widely used for crops protection, metsulfuron methyl (MSM) and chlorsulfuron (CSF) were simultaneously determined taking into account the different kinetic photodegradation behavior of their photoproducts in alkaline medium. As the analytes are present at trace concentration levels, a preconcentration by sorption on a mini-column packed with oxidized multiwall carbon nanotubes (ox-MWCNTs) at pH3.0 was performed. The retained analytes were removed from the ox-MWCNTs mini-column with a mixture of ACN contained 10% (v/v) of NaOH pH12.5. A total enrichment factor of 26-fold for a 14.50mL sample volume was obtained. The eluate was photodegraded by UV radiation during 126s and the fluorescent spectra corresponding to the analytes photoproducts were registered overtime between 300 and 500nm. The kinetic second order data were analyzed by unfolded-partial least squares-residual bilinearization (U-PLS/RBL) and multidimensional-partial least squares-residual bilinearization (N-PLS/RBL) algorithms. The relative error of prediction (REP %) for N-PLS/RBL was 7.73% for MSM and 6.37% for CSF. In the case of U-PLS/RBL, this statistical parameter was 7.75% for MSM and 7.23% for CSF, respectively. The limits of detection (LOD) were 0.19μgL−1 for MSM and 1.14μgL−1 for CSF using N-PLS/RBL and 0.21μgL−1 for MSM and 1.03μgL−1 for CSF when U-PLS/RBL was applied.The entire procedure was performed in an on-line integrated fully automated flow system coupled to a low mercury UV lamp (15W, 254nm) and a spectrofluorometer. In this manner, the preconcentration, photodegradation and detection steps were performed in a reproducible way.After optimization, the method was successfully applied to the analysis of real water samples obtained in the south part of Buenos Aires province and used for irrigation and consumption.

Simultaneous Removal of MTBE and Benzene from Contaminated Groundwater Using Ultraviolet-Based Ozone and Hydrogen Peroxide

Efficiency of ultraviolet-ozone (UV/O3) and ultraviolet-hydrogen peroxide (UV/H2O2) processes was investigated for simultaneous removal of methyl tertiary butyl ether (MTBE) and benzene from contaminated ground water. The photoreactor employed housed 15-watt low pressure (LP) and 150-watt medium pressure (MP) mercury UV lamps. Oxidation of contaminants was studied at two different levels of ozone and hydrogen peroxide. Brackish groundwater samples were spiked with MTBE and benzene up to a concentration of 500 μg L−1. Removal potential was evaluated at different parameters such as UV type and intensity and peroxide and ozone dosages, as well as contact time. Results indicated that no removal of the contaminants was attained when treated with hydrogen peroxide or ozone alone. However, about 50% and 30% removal of MTBE were achieved in 30 minutes when irradiated with MP-UV and LP-UV lamps, respectively. On the other hand, UV/H2O2process was found to be superior in removal of MTBE (90% in 10 min.) and benzene (95% in 5 min.) compared to UV/O3process. Furthermore, removal of benzene was comparatively easier than MTBE in both approaches. It is hence concluded that higher UV intensities and elevated doses of H2O2accelerate simultaneous removal of MTBE and benzene from water.

PREPARATION, CHARACTERIZATION AND APPLICATION OF SONOCHEMICALLY DOPED FE3+ INTO ZNO NANOPARTICLES

In this present study, mechanistic investigation of ultrasound ‐assisted dye decolorization/degradation was investi gated using sonochemically prepared Fe 3+ doped ZnO. Fe 3+ doped ZnO nanoparticle was prepared under ultrasou nd (20 kHz) irradiation using a doping concentration of 2 wt% of Fe(III). To invest igate the catalytic activity of Fe 3+ doped ZnO, Acid Red 14 (azo dye) was chosen for decolorization/degradation using sonolysis, pho tocatalysis and sono‐photocatalysis processes. To sthe influence of dopant onto structure, crystallinity, and optical properties, different analytical analyses were performed su ch as X‐ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTI R), Zeta potential, Delsa Nano Particle Size Analyz er (PSA), Vibrating Sample Magnetometer analysis (VSM) and Field Emission Scan ning Electron Microscopy (FE ‐SEM) etc. For photocatalytic experiments, a blended high pressure mercury UV lamp with maximum peak emission at 365 nm was used. The decolorizatio n/degradation of dye with modified photocatalyst showed faster reaction kinetics under sono‐photocatalytic process. Ultraso und showed an additive effect for degradation/decolorization process. The maximum decolorization of AR14 was achieved (~ 82%) under sono‐photocatlytic process with an initial dye concentration of 20 ppm . The sono ‐photocatalysis process showed 1.4 ‐ 1.6 higher reac tion rates with Fe‐ doped ZnO than pure ZnO. Index Terms: ZnO, Fe‐ZnO, Fe-doped ZnO, Sonocatalytic, Photocat alytic, Advanced Oxidation Process, AOP

Aniline degradation in aqueous solution by UV-aeration and UV-microO3 processes: Efficiency, contribution of radicals and byproducts

The use of combination of air and UV irradiation for organic matters removal has drawn attention since degradation efficiency would be significantly enhanced in the presence of oxygen. Considering the fact that a low-pressure mercury UV lamp (emitting at 254nm and 185nm) could dissociate oxygen in gas phase and generate ozone, UV irradiation with addition of ozone enriched air, generated by the same UV lamp, was introduced. This technology was called UV-microO3 because the concentration of ozone generated by UV irradiation was relatively low (lower than 1mgL−1). The degradation of aniline by UV-aeration and UV-microO3 processes was comparatively analyzed. It was shown that aniline underwent much faster and more complete degradation in UV-microO3 process than in UV-aeration system. Hydroxyl radical (OH) exposure in UV-microO3 process was 2.46times of that in UV-aeration system. Furthermore, increasing inlet air flow rate would be of benefit to maintaining high dissolved oxygen (DO) level in UV-aeration system, thus the aniline removal was improved. While concentration of ozone generated by UV irradiation increased at first and then declined as the air flow rate increased from 1.8Lmin−1 to 4.8Lmin−1 in UV-microO3 process, and similar trend for aniline removal rate was observed. The contributions of radicals on aniline removal in UV-aeration and UV-microO3 processes were calculated to be 23.1% and 67.7%. The formation of 4-aminophenol, 4-Hydroxydiphenylamine, azobenzene and 4-Phenylazophenol was observed as the major intermediates in UV-aeration and UV-microO3 processes, mechanism of aniline degradation was proposed based on experimental evidence.

Effects of wavelength and water quality on photodegradation of N-Nitrosodimethylamine (NDMA)

N-Nitrosodimethylamine (NDMA) is a potent carcinogen that yields a cancer risk of 10−6 at concentrations as low as 0.7ngL−1. Tentative guideline values are set at 3ngL−1 in California, USA; 9ngL−1 in Ontario, Canada; 40ngL−1 nationwide in Canada; and 100ngL−1 by the World Health Organization. NDMA is a great concern in treating reclaimed water as well as drinking water. UV degradation can be considered effective degradation method. A 1-log reduction of NDMA is achieved by 1000mJcm−2 of a 254-nm low pressure (LP) mercury UV lamp. However, a higher degradation efficiency than that provided by LP lamps is desired in practical treatment. In this study, the effects of wavelength and water quality were investigated to achieve higher degradation efficiency. The effects of wavelength were examined by comparing three UV lamps: a 222-nm Kr Cl Excimer UV lamp, a 254-nm LP mercury UV lamp, and a 230- to 270-nm filtered medium pressure (FMP) mercury UV lamp. The 222-nm lamp and FMP lamp achieved 4 times and 2.8 times higher degradation efficiency, respectively, than the conventional 254-nm LP lamp. Effects on water quality were also simulated by using absorption spectrum data of nitrate solutions and process water from a drinking-water treatment plant. In the simulation, the 222-nm lamp was affected by UV-absorbing compounds in the water, whereas the FMP lamp showed more stable degradation efficiency. Appropriate use of these three types of lamps could enhance the efficiency of degradation of NDMA.

Organic Pollutants Removal from Petroleum Refinery Wastewater with Nanotitania Photocatalyst and UV Light Emission

A real petroleum refinery wastewater, containing a range of aliphatic and aromatic organic compounds, was treated using nanotitania particles, as the photocatalyst in UV/TiO2process. Samples were collected from the inlet point of the biological treatment unit. A conic-shape, circulating, and upward mixing reactor, without dead zone, was employed. The light source was an immersed mercury UV lamp (400 W, 200–550 nm). Optimal suspended catalyst concentration, fluid pH, and temperature were obtained at amounts of near 100 mg·L−1, 3 and 45°C, respectively. A maximum reduction in chemical oxygen demand (COD) of more than 78% was achieved after about 120 min and, hence, 72% after only 90 min. Significant pollutant degradation was also relevant under other conditions. The identification analysis of the organic pollutants, provided by means of a GC/MS, equipped with headspace injection technique, showed that different petroleum compounds were degraded with high efficiencies.

An experimental and modelling investigation of the effect of the flow regime on the photocatalytic degradation of methylene blue on a thin film coated ultraviolet irradiated spinning disc reactor

AbstractIn this work, the impact of wave regime and operational parameters on the photocatalytic degradation of methylene blue was investigated on a thin film coated ultra-violet spinning disc. In the employed experimental setup, the wave regimes of spiral, unstructured and crisscross waves as well as smooth film could be observed at disc rotational speeds of 50–200rpm and flow rates of 5–20mL/s with a calculated average thickness of 160–450μm. The glass discs were coated with anatase TiO2 by a sol–gel procedure followed by heat treatment at 500° C for 1h. The reactor was irradiated by a low pressure mercury UV lamp producing an irradiance of 12–23W/m2 on the disc surface. The reactant was saturated with oxygen and the effect of spinning speed, flow rate and the resulting wave regime on the degradation rate and kinetics of methylene blue and its reaction intermediates determined. Reactions followed pseudo-second-order kinetics, suggesting dimerisation and/or mass transfer limitations given that the two reactions with the highest conversion observed at 15mL/s and 100 and 200rpm, were pseudo-first-order. The spinning disc reactor was, however, not photon transfer limited. The wave regimes showed no impact on the reaction rate, since the flow was mainly laminar with no interfacial mass transfer of oxidant required.

Preparation of Novel Series of UV Dual Curable Polyurethane-Modified Epoxy Monoacrylates and their Films Properties

A new series of radical-cationic UV dual curable polyurethane-modified epoxy monoacrylates (PMEMA) was prepared. Radical-cationic UV dual curable were prepared with photosensitive resin (epoxy monoacrylates (EMA) or PMEMA), reactive diluents, radical and cationic photoinitiators. UV dual cured films of those liquid compositions were obtained by using a high pressure mercury UV lamp. FTIR spectra identified the change of C=C and epoxy groups absorption peaks during the UV-curing process. The effect of different modified oligomers on the gel content, water absorption, mechanical and thermal properties of radical-cationic UV dual cured films was investigated. The characteristic C=C (1635cm-1, 810cm-1) and epoxide (910cm-1, 772cm-1) absorption speaks were no longer detectable after UV dual cured. The gel contents of all samples using PMEMA as oligomers were beyond 97.0% and their water absorption values were about 0.80%. With the length of flexible polyurethane chain segments increased, the Young’s modulus and breaking strength of UV dual cured films decreased gradually, except for the relative elongation. The volume shrinkage test indicated that the UV dual cured films exhibited lower internal stress and higher cohesive force than single radical UV cured films. The results of thermogravimetric analysis (TGA) for the UV dual cured films indicated good thermal stability with no appreciable weight loss until well above 250°C.

Aqueous Photodegradation of Selected Antibiotics under Different Conditions

Different aqueous photodegradation behaviors of sulfamethoxazole, trimethoprim and sulfapyridine were investigated under different conditions in this study. Comparison of degradation rates of selected pharmaceuticals among different aqueous media under high pressure mercury lamp, natural light and UV lamp were shown. Results showed that light source, pH, temperature, time and different aqueous solutions were important factors for photodegradation of these antibiotics and also demonstrated photodegradation was an important environmental fate of these antibiotics.