Low-pressure Mercury Arc Lamp Research Articles

The Efficiency of Application of UV + VUV Radiation for Preventing Unicellular Invasions Transported with Ballast Waters of Ships

The results of an experiment on modeling the neutralization of ship ballast waters (BWs) contaminated with unicellular halophilic alga Dunaliella terricola using the radiation of a low-pressure mercury arc lamp with wavelengths of 254 and 185 nm are presented. The experiment models the filling of the BW tank with seawater contaminated with D. terricola using a ballast water decontamination unit, followed by the storage of the water in the BW tank for 5 days, thereby simulating ship navigation, and BW discharge at the port of arrival through the unit. Contaminated BW was neutralized according to the technology of advanced oxidative processes (AOPs) using ozone and hydrogen peroxide which were generated in the water by radiation of a 185 nm line. It is experimentally established that the proposed method of treating model ballast water stops the reproduction of a test object. The conducted research shows prospects of application of UV + VUV (ultraviolet + vacuum ultraviolet) radiation for preventing the transfer of alien unicellular organisms by BWs and their invasions into local biocenoses.

UV disinfection of stabilization pond effluent: a feasible alternative for areas with land restriction

The purpose of this research was to determine the feasibility of a UV photoreactor for the disinfection of effluent from a polishing pond following a UASB reactor treating domestic wastewater. For this, a 20 mm diameter photoreactor (20.7 litre volume) equipped with four 30 W submerged low-pressure mercury arc lamps was used. Three tests with contact times and doses ranging from 45 to 90 s and from 16.9 to 31.3 mW s cm(-2) were carried out. Inactivation of total coliforms and Escherichia coli varied from 2.6 to 3.4 log-units, even with the presence of suspended solids in the range of 87 to 102 mg L(-1). These results have shown that UV radiation disinfection of pond effluents can be a feasible alternative in areas with land restriction.

The photochemistry of 1-alkenyl-substituted-1,2,3-benzotriazoles leading to formation of indole and fused indole derivatives

Under photolysis conditions involving irradiation with a 16 W low pressure mercury arc-lamp (254 nm) or sunlight, functionally substituted 1-vinylbenzotriazoles react efficiently to produce 2-acylindoles, 2-benzotriazol-1-yl-4-methylquinolin-3-ol, isatin, indolo[2,1-b]quinazoline-6,12dione (tryptanthrin) and dihydropyrazolo[4,3-b]indole.

Reliable Measurements of UV Lamp Performance Using a Near-Field Technique

Low pressure mercury arc lamps are an effective ultraviolet light source for disinfection of water. Critical lamp operating parameters such as the decrease in UV output with time, effect of water temperature on lamp output, and the effect of lamp dimming should be determined using a lamp in water. The reliable operation of a near-field test apparatus is described that is capable of measuring these quantities. The use of a radiometer with fiber optic light collection and standard reference lamp results in the reproducible measurement of these values using the near-field system. The stability of measurement is obtained using the reference lamp, which compensates for variations in the response of the fiber optic assembly. For sample lamps, a decrease of 11% output over 12,000 hours was observed. For the same lamp type, the relative calibrated output of the lamp increases between 5 and 50°C, with a ±10% change in lamp output relative to the reference temperature of 20°C. The apparatus samples the irradiance at a local point on the lamp, but the UV output of low pressure amalgam lamps as determined by the near-field technique is shown to be uniform over the entire lamp, except for within 1 cm of the lamp filament. This is shown for both new and 12,000 hour aged lamps, so that accurate lamp aging data can be determined. The change in UV output with water temperature change was demonstrated to be similar for both new and aged lamps in this study, except for the expected decrease in peak lamp UV output noted for the aged lamp.

Photooxidation of a reactive azo-dye from the textile industry using UV/H2O2 technology: process optimization and kinetics

The homogeneous advanced oxidation process of UV/H2O2 was utilized to decolourize CI Reactive Red 195A (RR195A) as one of the most used dyes in the textile industry in Queensland. The UV radiation source was a low-pressure mercury arc lamp (60W emitting at 253.7nm). In this study, the effects of initial hydrogen peroxide (H2O2) dosage, dye concentration, pH and temperature were examined to find out the optimum operating conditions of the treatment process. Complete decolourization was achieved in the relatively short time of 20-30 minutes irradiation. Faster decolourization was achieved at low pH and high temperature. The removal rate increased with increasing initial concentration of H2O2 up to an optimum value. The decolourization reaction was found to follow at least initially first order kinetics with respect to the dye concentration. However, even after near complete removal of the active dye from the solution, approximately 60% of the COD was still remaining, indicating only partial breakdown of the dye molecule. In general, the result indicates that the UV/H2O2 technology proved to have good potential for removing dyestuff from wastewater but further treatment might be necessary to achieve complete mineralization of the organic intermediates.

Ultrasonic disinfection of wastewater effluents for high-quality reuse

Cavitation, induced by ultrasound at low frequencies, is an effective means for the disintegration of bacterial cells. Two effects can be observed: at low ultrasound doses bacteria flocs can be declumped by mechanical shear stresses, and at increased doses ultrasound cavitation has an impact on the cell walls such that they are broken. In lab scale experiments a horn sonotrode operated at 20 kHz was run in combination with a low-pressure mercury arc lamp to treat wastewater samples taken from the effluent of a municipal treatment plant. At low ultrasound intensities a drastic change in samples' particle size distribution was observed. Consequently, subsequent UV irradiation was far more efficient as the number of large particles which impede disinfection processes was minimised by the sonication. Hence, applied UV doses could be reduced notably to obtain the same or even better disinfection effects.

Photochemical bis-silylation of C 60: synthesis of a novel C 60 main chain polysilane

The photoreaction of polysilanes and cyclic oligosilanes with C 60 has been investigated. Photoirradiation of a solution of C 60 and polysilanes in benzene in a degassed quartz tube at 20°C with a low-pressure mercury-arc lamp has afforded the C 60–polysilane adduct in moderate yield, in which C 60 is incorporated into the polysilane chain. A unique electronic property of the C 60 main chain polysilane has also been elucidated.

Numerical modelling of UV intensity: Application to collimated-beam reactors and continuous-flow systems

When properly designed, collimators can be used to develop a source of electromagnetic radiation which is uniform and easily quantified. A collimator design is presented which minimizes reflection and promotes the development of a well-behaved, quantifiable radiation source. The design of the collimator is optimized by use of a numerical model, line source integration (LSI), a continuous version of the widely used point-source summation technique. The LSI model is used to quantify the radiation intensity field from a collimator which incorporated a standard low-pressure mercury arc lamp as its source of radiation. A method of measuring lamp output power is also demonstrated which employs experimental measurements of intensity through a collimator and the LSI model. The physical meaning of this measurement, its limitations and potential applications are discussed.

Laboratory-scale photodegradation of phenol in aqueous solution by photocatalytic membranes immobilizing titanium dioxides

The TiO 2-mediated photodegradation of phenol was studied at 298 ± 2 or 308 ± 2 K (with the ratio between the hydrogen peroxide added and the stoichiometric amount ( N) in the range 0–10), using PHOTOPERM® CPPI313 membranes containing immobilized 30 ± 3 wt.% TiO 2, with high or low pressure mercury arc lamps (radiant power in the absorption range, 145 and 8 W respectively). The initial rate of photodegradation was studied as a function of the initial concentration of substrate (1.0x10 −5−0.12 M) using the linearized form of the Langmuir-Hinshelwood equation, from which the rate constants k and apparent equilibrium adsorption constants K were evaluated. The rationalization of k and K values on the basis of their dependency on N, the apparent reaction order, the advantages of the membrane process with respect to the use of colloidal suspensions of TiO 2, also tested in comparable conditions, and the kinetic significance of K, on the basis of no measurable dark adsorption onto the photocatalytic membranes, are discussed.

The synthesis of azocine derivatives by the photocycloaddition of phenols to 1-naphthonitrile and 4-methoxy-1-naphthonitrile

On irradiation of 1-naphthonitrile ( 1a) and 4-methoxy-1-naphthonitrile ( 1b) with a low pressure mercury arc lamp, photocycloaddition occurs to phenol ( 2a), 4-methylphenol ( 2b) and 4-methoxyphenol ( 2c) to give the substituted azocin-2(1H)-ones ( 4), formed from the initial 1,2-addition of the cyano group to the aromatic ring of the phenols.

Holographic Optical Element for Visual Display Applications

Off-axis and off-bisector reflection-type holographic visual display elements have been recorded in dichromated gelatin deposited on planar or spherical shell substrates of glass or Plexiglas. A procedure for bonding gelatin to Plexiglas is given. Holographic elements are recorded at the argon wavelength of 514.5 nm and reconstructed with spectral lines from a low pressure mercury arc lamp. Measured image characteristics for a flat substrate hologram agree with ray-tracing calculations. A swelling of the gelatin by approximately 6.6% after processing does not perceptibly affect the dispersion, astigmatism, or distortion in the image, that is, the grating equation depends on the spacing between the fringes on the surface of the gelatin and is not affected by the swelling or shrinking. However, the Bragg equation depends on the distance normal to the fringe planes and is affected by thickness changes of the gelatin. Therefore, this thickness change is taken as an independent parameter and used to adjust the wavelength for maximum diffraction efficiency, without affecting the image angle. Data reveal a near linear relationship between the dichromate concentration of 0.5-10% used to photosensitive the gelatin and the display wavelength of maximum diffraction efficiency. Lateral dispersion is 0.12 +/- 0.01 degrees / nanometer for both planar and spherical shell substrate elements recorded in quite similar geometry, but their astigmatisms are not alike.

Raman Spectroscopy Experiment for the Senior Laboratory

A description is given of the design, construction, and performance of a Raman source which could be used in a senior laboratory accompanying optics and spectroscopy courses. The apparatus utilizes a single low-pressure mercury arc lamp at one focus of an elliptical housing. Light scattered axially from the Raman sample at the other focus is condensed onto the spectrograph slit via a lens system which also eliminates non-scattered radiation. When used with a Hilger and Watts model D-186 constant deviation spectrograph, a spectrum for CCl4 was obtained after an exposure of about two minutes on general purpose spectrographic plates. The classical spring constant is calculated for CS2.

Ignition of Low Pressure Mercury Arc Lamps with Auxiliary Condensor Battery

In Raman spectroscopy discontinuous radiation with low continuous background can be obtained from low pressure mercury arc lamps, preferably operated with direct current (1). As the ignition voltage of the arc is well above the normal operating voltage, the excess voltage must be suppressed by means of a series resistor, which has to carry large current (approximately 20 amp). The power, dissipated by this resistor, may well be about a kilowatt. The heat generated in this way is not only wasted but is highly undesirable as it is necessary to keep the temperature constant in the spectrograph room.

Production, Concentration, and Decomposition of Ozone by Ultraviolet Lamps

With the increasing use of bactericidal ultraviolet lamps it has become very desirable to have more information about the accompanying production of ozone which is the only feasible agent for protecting surfaces not exposed to direct or scattered radiation. Very little published information is available and practically all the data given in this article are new. A low pressure mercury arc lamp of the type of the Westinghouse Sterilamp gives an amount of ozone of the order of 1/100th gram per hour, corresponding to a rate of emission of energy of at least 1/100th of a watt. A gentle air motion increases the yield. All the ozone is produced within a few feet of the lamp. The rate of decomposition of the ozone after the lamps are turned off is faster the greater the surfaces compared with the volume, the higher the temperature, the higher the humidity, and the more 2537 radiation present. The most important factor, the equilibrium ozone concentration, in an enclosure of several cubic meters is proportional to the ozone produced, inversely proportional to the volume, and is reduced to about one-third when the relative humidity changes from a few percent to near saturation and to about one-half when the temperature is raised from 7° to 32°C. It is very roughly 25 percent lower if the 2537 radiation of the present Sterilamp, accompanying the short wave-length ozone radiation, is doubled.