Medium Pressure Mercury Lamp Research Articles

Comparison of the Effectiveness of UV Radiation Sources for Wastewater Treatment of Terephthalic Acid

The following sources of UV radiation used for photochemical wastewater treatment are considered: medium and low pressure mercury lamps, KrCl and KrBr excimer lamps, and a pulsed xenon lamp. On the example of photolysis of terephthalic acid (TPA), various parameters were calculated that allow quantitative comparison of UV sources: radiation efficiency, quantum output of the process, specific energy and operating costs for the destruction of the target pollutant.

Performance of high-efficiency UV-C LEDs in water disinfection: Experimental, life cycle assessment, and economic analysis of different operational scenarios

The widespread use of low or medium pressure mercury lamps in UV-C water disinfection should consider recent advances in UV-C LED lamps that offer a more sustainable approach and avoid its main drawbacks. The type of water and the mode of operation are critical when deciding on the treatment technology to be used. Therefore, this study investigates the potential application of UV-C LED disinfection technology in terms of kinetics, environmental assessment, and economic analysis for two scenarios: the continuous disinfection of a wastewater treatment plant (WWTP), and disinfection of harvested rainwater (RWH) in a residential household that operates intermittently. Experiments are conducted using both the new UV-C LED system and the conventional mercury lamp to disinfect real wastewater. Removal of total coliforms and Escherichia coli bacteria, with concentrations of approximately 105 and 104 CFU per 100 mL has been followed to assess the performance of both types of UV-C lamps. The experimental study provides kinetic parameters that have been further used in the environmental assessment conducted from a life cycle perspective. Additionally, considering the significant role of electricity consumption, a preliminary economic analysis has been conducted. The results indicate that first-order kinetic constants of pathogens removal with UV-C LEDs achieve 1.4 times higher values than Hg lamp. Regarding the environmental and economic assessment, for disinfection systems operating continuously, LEDs result in environmental impacts 5 times higher than Hg lamp in most categories, indicating that Hg lamps offer a viable option both from economic and environmental point of view. However, for installations with intermittent operation, LEDs emerge as the most competitive alternative, due to their ability to be turned on and off without affecting their lifespan. This study shows that UV-C LED lamps hold promise to replace conventional mercury lamps in a near future.

Synthesis and Photolysis Properties of a New Chloroquine Photoaffinity Probe.

A new chloroquine-derived photoaffinity probe has been prepared by a convergent synthesis from derivative of 4,7-dichloroquinoline and N1,N1-diethyl-N4-methylpentane. The features of this probe are a unique 3-azido photolabel, the pyridine ring of the quinoline, and the presence of a secondary amine at the 4-position of the quinoline. These features, particularly the 4-amino methylation, prevent triazole formation through combination of the 3-azide and the 4-amine. This undergoes facile cleavage with exposure to a medium-pressure mercury lamp with a 254 nm excitation wavelength. Trapping of the nitrene byproduct is accomplished with its reaction with N-phenylmaleimide as its cycloazidation product. The structure of a ring-opened DBU amine has been structurally characterized.

Radiation Curing of Phosphorus Telomer-Based Coatings Using UV LEDs or Medium-Pressure Mercury Lamp

In the presented study, UV LEDs (365 nm) or a medium-pressure mercury lamp (UV-ABC) were verified as UV radiation sources initiating the photocrosslinking process of varnishes based on novel photopolymerizable phosphorus (meth)acrylate oligomers. Coating formulations were composed of (meth)acrylic/styrene telomers with terminal P-atoms (prepared via a UV phototelomerization process) and different photoinitiators (HAPs, APOs, or APO blends). The kinetics of the UV crosslinking process of the coating formulations depending on UV irradiation and the UV range was investigated by the photo-DSC method. Moreover, the hardness of the varnishes and the conversion of double bonds using the FTIR method were tested. The photopolymerization rate and the photoinitiation index, depending on the type of photoinitiator, were as follows: APOs < APO blends < HAPs. However, the highest coating hardness results were obtained using the least reactive photoinitiator from the APO group, i.e., Omnirad TPOL, or a mixture of three different types of acylphosphine (Omnirad BL 750). The greater effectiveness of the above-mentioned APOs over HAP was also demonstrated when using a UV LED lamp at 365 nm with a low UV dose and UV irradiance, thanks to the presence of phosphoric acid diester in the coating composition, acting as both a telogen and an antioxidant.

Effects of pH-dependent speciation on the photolytic degradation mechanism of phosphonates

Phosphonates, commonly used as strong metal chelating agents in household and industrial products, partially persist through water treatment processes, releasing significant amounts into the environment and raise concerns about potential environmental impacts. This study investigated effects of pH-dependent speciation of phosphonates on their photolysis by a medium-pressure mercury lamp in aqueous solution under ambient air conditions. Different species of aminotrimethylphosphonic acid (ATMP), and its most important transformation products iminodimethylphosphonic acid(IDMP) and aminomethylphosphonic acid(AMPA) were analyzed by liquid chromatography in combination with isotope ratio (CSIA) and high resolution mass spectrometry. UV radiation (<320 nm) was required for the photolytic degradation of ATMP, IDMP, and AMPA, and their photolysis was influenced by pH-dependent speciation. Degradation rate constant of ATMP was affected by pH, but a direct correlation between kobs and pH was not found. In contrast, IDMP and AMPA exhibited a direct correlation between pH and kobs during photolysis. CSIA revealed an inverse carbon kinetic isotope effect (KIE) for ATMP, while a normal carbon KIE was observed for IDMP and AMPA. Quantum chemical calculations supported degradation pathway interpretation and KIE understanding. Energy barrier calculations distinguished N-C vs C-P bond cleavage, favoring N-C cleavage on average, consistent with observed transformation products. Further calculations, considering possible transition states, provide first promising hints for elucidation of present KIEs.

Interconversion and Removal of Inorganic Nitrogen Compounds via UV Irradiation

Dissolved inorganic nitrogen (DIN) species are key components of the nitrogen cycle and are the main nitrogen pollutants in groundwater. This study investigated the interconversion and removal of the principal DIN compounds (NO3−, NO2− and NH4+) via UV light irradiation using a medium-pressure mercury lamp. The experiments were carried out systematically at relatively low nitrogen concentrations (1.5 mM) at varying pHs in the presence and absence of oxygen to compare the reaction rates and suggest the reaction mechanisms. NO3− was fully converted into NO2− at a pH &gt; 3 in both oxic and anoxic conditions, and the reaction was faster when the pH was increased following a first-order kinetic at pH 11 (k = 0.12 min−1, R2 = 0.9995). NO2− was partially converted into NO3− only at pH 3 and in the presence of oxygen and was stable at an alkaline pH. This interconversion of NO3− and NO2− did not yield nitrogen loss in the solution. The addition of formic acid as an electron donor led to the reduction of NO3− to NH4+. Conversely, NH4+ was converted into NO2−, NO3− and to an unidentified subproduct in the presence of O2 at pH 10. Finally, it was demonstrated that NO2− and NH4+ react via UV irradiation with stoichiometry 1:1 at pH 10 with the total loss of nitrogen in the solution. With these results, a strategy to remove DIN compounds via UV irradiation was proposed with the eventual use of solar light.

Effect of Photoinitiator Concentration and Film Thickness on the Properties of UV-Curable Self-Matting Coating for Wood-Based Panels

Matte coatings have found wide-ranging applications across diverse industries. In this study, self-matting films with surface wrinkles were produced by exposing UV-curable polyurethane acrylate (UV-WPUA) resin to 172 nm Xe2* excimer and medium-pressure mercury lamps. The gloss values, micromorphologies, water contact angles (WCAs), roughness values, and friction behaviors of UV-WPUA films with different photoinitiator (PI) concentrations and thickness were investigated for the first time. The results indicate that the gloss values of the films at the same thickness enhance with the increase of PI concentration, while the amplitude of wrinkles, roughness, and WCAs decrease; however, the friction coefficient shows insignificant variations. While the PI concentration is unchanged, an increase in film thickness results in a decrease in gloss value and an increase in roughness and friction coefficient. Nevertheless, the WCA is relatively constant. The PI concentration of 0.5 wt% (lowest gloss value of cured film) was utilized to prepare the UV-WPUA wood coating. The cured coating film exhibited low gloss (4.9 GU at 60° and 5.2 GU at 85°) and outstanding mechanical properties, including 3H pencil hardness, grade 0 adhesion, excellent wear resistance, and tensile property. These findings can be utilized to guide the development of self-matting wood coatings and the production of wood-based panels used in industrial finishing.

Biomimetic high water adhesion superhydrophobic surface via UV nanoimprint lithography

Imitating nature and comprehending its workings is a means for human beings to advance the development of functional materials. In this study, UV nanoimprint lithography technology was utilized to successfully replicate the micro-nano hierarchical structure (micro-papillae and nano-wax tube crystals) present on the surface of the natural fresh lotus leaf. A series of UV-curable waterborne polyurethane acrylate (UV-WPUA) surfaces with special wetting and superhydrophobic properties were obtained. The polydimethylsiloxane negative stamp with lotus leaf’s structure was obtained through a stamp replica molding method, and then the UV-WPUA resin covered with the negative stamp was exposed to 172 nm Xe2* excimer and medium-pressure mercury lamps to mimic the micro-nano hierarchical structure of the lotus leaf. The UV-WPUA surfaces displayed high water adhesion superhydrophobic properties, with a water contact angle reaching 160.8° and water adhesive force of 140.0 μN, and exhibiting excellent self-cleaning performance. The results indicate that higher the UV intensity, the more accurately the surface replicates the micro-nano hierarchical structure of the lotus leaf, resulting in larger water contact angle and higher adhesive force. This study paves the way for the advancement of functional surfaces through the simulation of natural materials.

Mechanistic investigation of phosphonate photolysis in aqueous solution by simultaneous LC-IRMS and HRMS analysis

The mechanism of photolytic degradation of aminotrimethylphosphonic acid (ATMP) in an aqueous solution is not completely elucidated with respect to the transformation products formed during technical photodegradation. For the first time, the degradation of ATMP was investigated with simultaneous analysis by isotope ratio and high-resolution mass spectrometry (LC-IRMS+HRMS). This instrumental coupling combines quantitative data on degradation with compound-specific stable carbon isotope analysis (CSIA) in terms of kinetic isotope effects while identifying transformation products. Additionally, in combination with wet chemical analysis of ortho-phosphate (o-PO4), phosphorus balances were established to elucidate and interpret the degradation mechanism of ATMP under photolysis. Various experimental conditions during photolysis (temperature, dissolved oxygen concentration, and wavelength range) were investigated.ATMP was transformed to iminodimethylphosphonic acid (IDMP), aminomethylphosphonic acid (AMPA), and o-PO4 as main products during photolysis with a medium pressure mercury lamp. UV radiation < 310 nm was found to be required for ATMP degradation. The degradation of ATMP and its transformation products is slightly affected by temperature and dissolved oxygen concentration. Considering possible reactive oxygen species, such as hydroxyl radicals, it is assumed that the degradation of ATMP occurs to a small extent via a parallel degradation pathway in addition to photolysis. Complementary CSIA revealed an inverse carbon isotopic effect of ATMP due to direct photolysis, unaffected by the experimental conditions considered, while no isotopic effect was associated with the hydroxyl radical (H2O2) oxidation of ATMP. In UV/H2O2 oxidation of ATMP, four of five additional unknown transformation products, which have not yet been described in literature, could be assigned to postulated structures based on HRMS data. The findings achieved in this study demonstrate the advantages of simultaneous analysis by LC-IRMS+HRMS as a tool to elucidate reaction mechanisms for the first time.

Flow photolysis of aryldiazoacetates leading to dihydrobenzofurans via intramolecular C-H insertion.

Flow photolysis of aryldiazoacetates 3-5 leads to C-H insertion to form dihydrobenzofurans 6-8 in a metal-free process, using either a medium pressure mercury lamp (250-390 nm) or LEDs (365 nm or 450 nm) with comparable synthetic outcomes. Significantly, addition of 4,4'-dimethoxybenzophenone 9 results in an increased yield and also alters the stereochemical outcome leading to preferential isolation of the trans dihydrobenzofurans 6a-8a (up to 50% yield), while the cis and trans diastereomers of 6-8 are recovered in essentially equimolar amounts in the absence of a photosensitiser (up to 26% yield).

UV-LEDs combined with persulfate salts as a method to inactivate microalgae in ballast water

The Ballast Water Management Convention (BWMC) establishes limits for viable organisms in discharged ballast water. UV-based ballast water management systems (BMWS) are among the most common, especially those with low pressure (LP) and medium pressure (MP) mercury lamps. An interesting alternative to mercury lamps could be UV LEDs that have been developing over recent years. UVA, UVB, and UVC LEDs have been tested as a method to inactivate microalgae in ballast water. For this study, the diatom Phaeodactylum tricornutum was selected as a target organism. Comparing the D2 (dose required to achieve two log reductions) for P. tricornutum from different UV treatments, it was observed that UVC LEDs were 74.2 % more efficient than UVB LEDs and, compared with previous studies, 48.1 % more efficient than UVC LP mercury lamps. If a five day dark post-treatment was combined with the UV irradiation to avoid photoreactivation, UVC LEDs were 90 % more efficient than UVB LEDs and, compared with previous studies, 36.8 % more efficient than UVC LP mercury lamps. No damage with or without photoreactivation was caused by UVA irradiation with doses up to 4·104 mJ cm−2. The combination of peroxymonosulfate (PMS) with UVA, UVB and UVC LEDs did not significantly increase the inactivation, and the combination of the peroxydisulfate (PDS) with UVC LEDs slightly decreases the inactivation compared with UVC irradiation alone. In conclusion, UVC LEDs were the most efficient for inactivating P. tricornutum, and the combination of PMS and PDS with UV LEDs did not notably improve it.

Porphyrin@Lignin nanoparticles: Reusable photocatalysts for effective aqueous degradation of antibiotics

The aqueous photocatalyzed degradation of trimethoprim (TMP) and sulfamethoxazole (SMX), highly prescribed antibiotics, often found in hospital wastewaters and/or surface/ground waters in high concentrations, is described, using a 400 W medium pressure mercury lamp as irradiation source, air as oxidant and a porphyrin based photocatalyst. The new photocatalyst was prepared by encapsulation of stable meso-tetra(2,6-dichlorophenyl)porphyrin photosensitizer into acetylated lignin nanoparticles, which are derived from a bio-based cellulose industry byproduct. This is a reusable stable catalyst (after at least 7 cycles, no loss of activity or degradation/leaching, was observed) capable of promoting the nearly complete degradation of TMP and SMX antibiotics, with unprecedented total organic carbon (TOC) removal, namely 75 % and 85 %, respectively. Mechanistic studies of these reactions, using singlet oxygen and radical scavengers, followed by HPLC-MS analysis allowed the identification of only two residual TMP photoproducts.

Reductive and Oxidative UV Degradation of PFAS—Status, Needs and Future Perspectives

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) consist of a group of environmentally persistent, toxic and bio-accumulative organic compounds of industrial origin that are widely present in water and wastewater. Despite restricted use due to current regulations on their use, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) remain the most commonly detected long-chain PFAS. This article reviews UV-based oxidative and reductive studies for the degradation of PFAS. Most of the UV-based processes studied at lab-scale include low pressure mercury lamps (emitting at 254 and 185 nm) with some studies using medium pressure mercury lamps (200–400 nm). A critical evaluation of the findings is made considering the degradation of PFAS, the impact of water quality conditions (pH, background ions, organics), types of oxidizing/reducing species, and source of irradiation with emphasis given to mechanisms of degradation and reaction by-products. Research gaps related to understanding of the factors influencing oxidative and reductive defluorination, impact of co-existing ions from the perspective of complexation with PFAS, and post-treatment toxicity are highlighted. The review also provides an overview of future perspectives regarding the challenges in relation to the current knowledge gaps, and future needs.

UV direct photolysis of amisulbrom in buffer solutions: Kinetics, quantum yield, products identification, DFT, mechanism and predict toxicity

Direct photolysis is one of the most important abiotic transformations for pesticides in the aquatic environment. In this study, direct photolysis of amisulbrom was studied under low and medium pressure mercury lamps at pH 4.0, 7.0 and 9.0. The result shows that the direct photolysis rates of amisulbrom in the basic solution are 2.5–2.8 times faster than in the acidic (pH 4.0) or neutral (pH 7.0) solutions under low pressure mercury lamp, while the direct photolysis rate of amisulbrom is similar in different buffer solutions under medium pressure mercury lamp. The quantum yield of amisulbrom is determined in the wavelength range of 190–400 nm. Eight main photolysis products were identified using ultra-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS). Based on the identified photolysis products, the density functional theory (DFT) analysis, photolysis profiles and the possible photolysis pathway of amisulbrom are proposed. The energy gap of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) for amisulbrom is 4.76 eV and it corresponds to a photon energy of 260.5 nm. The quantitative structure–activity relationship (QSAR) model is used to predict the toxicity of amisulbrom and its TPs. The Results show that TP-I (3-((6-fluoro-2-methyl-1H-indol-1-yl)sulfonyl)-1H-1,2,4-triazol-1-ium), TP-II (3-bromo- 6-fluoro-2-methyl-1H-indole), TP-III (1-((1H-1,2,4-triazol-3-yl)sulfonyl)-3-bromo-6-fluoro- 2-methyl-1H-indole) and TP-V (6-fluoro-2-methyl-1H-indole) are more toxic than their parent.

Inactivation of Aspergillus species in real water matrices using medium pressure mercury lamps.

The aim of this work is to understand the inactivation efficiency of medium pressure mercury lamps, measured in terms of growth inhibition as well as cell death, damage and response, using three strains from three different Aspergillus species (A. fumigatus, A. niger and, A. terreus) spiked in filtered surface water. A complete characterization of the effect of the treatment on each strain of the fungal species was assessed considering spores' morphology, cell wall integrity and enzymatic activity, the formation of pyrimidine dimers in the DNA and proteome analysis. Results showed that, when subjected to medium pressure mercury lamps, A. niger is the most resistant to inactivation, that both A. fumigatus and A. niger suffer more morphological changes and present a higher number of damaged spores and A. terreus presented more dead spores. DNA damages detected in A. niger were able to be repaired to some extent, under both light and dark conditions. Finally, proteome analysis showed that the UV radiation treatment triggered different types of stress response, including cell wall reorganization and DNA repair in A. fumigatus and A. terreus, and oxidative stress responses like the increase in production of citric acid and itaconic acid in A. niger and A. terreus, respectively.

Characterization of eukaryotic microbiome and associated bacteria communities in a drinking water treatment plant

The effectiveness of drinking water treatment is critical to achieve an optimal and safe drinking water. Disinfection is one of the most important steps to eliminate the health concern caused by the microbial population in this type of water. However, no study has evaluated the changes in its microbiome, specially the eukaryotic microbiome, and the fates of opportunistic pathogens generated by UV disinfection with medium–pressure mercury lamps in drinking water treatment plants (DWTPs). In this work, the eukaryotic community composition of a DWTP with UV disinfection was evaluated before and after a UV disinfection treatment by means of Illumina 18S rRNA amplicon-based sequencing. Among the physicochemical parameters analysed, flow and nitrate appeared to be related with the changes in the eukaryotic microbiome shape.Public health concern eukaryotic organisms such as Blastocystis, Entamoeba, Acanthamoeba, Hartmannella, Naegleria, Microsporidium or Caenorhabditis were identified.Additionally, the relation between the occurrence of some human bacterial pathogens and the presence of some eukaryotic organisms has been studied. The presence of some human bacterial pathogens such as Arcobacter, Mycobacterium, Pseudomonas and Parachlamydia were statistically correlated with the presence of some eukaryotic carriers showing the public health risk due to the bacterial pathogens they could shelter.

Enhanced transformation of aquatic organic compounds by long-lived photooxidants (LLPO) produced from dissolved organic matter

Dissolved organic matter (DOM) plays a crucial role in the photochemical transformation of organic contaminants in natural aquatic systems. The present study focuses on the characterization of a specific effect previously observed for electron-rich phenols, consisting in an acceleration of the DOM-photosensitized transformation of target compounds at low concentrations (< 1 µM). This effect was hypothesized to be caused by DOM-derived "long-lived" photooxidants (LLPO). Pseudo-first-order rate constants for the transformation of several phenols, anilines, sulfonamide antibiotics and phenylureas photosensitized by Suwannee River fulvic acid were determined under steady−state irradiation using the UVA and visible wavelengths from a medium-pressure mercury lamp. A significant enhancement (by a factor of 2.4 − 16) of the first-order transformation rate constant of various electron-rich target compounds was observed for an initial concentration of 0.1 μM compared to 5 μM . This effect points to a relevant reactivity of these compounds with LLPO. For phenols and anilines the enhancement effect occurred only above certain standard one-electron oxidation potentials. From these data series the standard one-electron reduction potential of LLPO was estimated to be in the range of 1.0 − 1.3 V versus the standard hydrogen electrode. LLPO are proposed to mainly consist of phenoxyl radicals formed by photooxidation of electron-poor phenolic moieties of the DOM. The plausibility of this hypothesis was successfully tested by studying the photosensitized transformation kinetics of 3,4-dimethoxyphenol in aqueous solutions containing a model photosensitizer (2-acetonaphthone) and a model electron-poor phenol (4-cyanophenol) as DOM surrogates.

Effect of Cationic Photoinitiator on the Polymerization Kinetics of Vinyl Ether Monomers

In this study, the performance of a new triarylsulfonium photoinitiators in the initiation of cationic polymerization of vinyl monomers was investigated by infrared spectroscopy (IR). The photoinitiator exhibit absorption characteristics compatible with the emission characteristics of medium pressure mercury lamps, which are the main sources of UV light in the industry. The experimental results indicate that the photoinitiator is most effective at a concentration of 1%. At the investigated conditions, the maximal conversion degree is 77.8% and the polymerization rate is 0.56 s-1. The curing process is even faster than the corresponding free-radical photopolymerization of acrylic monomers

Advanced Oxidation Process treatment for azo dyes pollutants using ultra-violet irradiation

The research included studying the photocatalytic efficiency of zinc oxide onto photo reaction of Alizarin yellow (A.Y) in the presence of ultraviolet radiation. Several parameters affect the photolysis rate of dye were studied such as: effect of acidic function, different oxidants and supporting of zinc oxide surface. The solution of dye was irradiated using medium pressure mercury lamp 400 W. The results showed that the maximum percentage of dye photolysis was at a natural acidic function using hydrogen peroxide as oxidant and activated charcoal as support. The kinetics of reaction were also studied and the results proved that the reaction from pseudo first order.

Photochemical microfluidic synthesis of vitamin D3 by improved light sources with photoluminescent substrates

This study presents a novel technique for the controllable preparation of photoluminescent substrates to enhance the photochemical microfluidic synthesis of vitamin D3. The dip-coating method to prepare the substrates was experimentally optimized, and the corresponding emission behaviors were systematically investigated. The substrates were successfully used to enhance the ultraviolet B (UVB) emission of a low-power light source (e.g., an 8 W lamp), whose UVB emission intensity was increased by approximately 11 times. By virtue of the novel light source, the productivity of a single set of photochemical microreactor with a 12-meter-long channel (0.6 mm i.d.) was increased to 1.83 kg·a−1, which was 42% higher than that of a 100 W lamp, and no cooling devices were used. The method is simple and has great potential to replace traditional medium-pressure mercury lamps for UVB-irradiated photochemical reactions.