Electrodeless Discharge Lamps Research Articles

Br I spectral line measurements in the range 2000–6000 cm−1: Part I

The present study provides data on the spectral line measurements of atomic bromine (Br I) in the 2000–6000 cm−1 range in the infrared spectral region by using a high-resolution Fourier Transform Spectrometer. Electrodeless discharge lamps (EDL) of bromine were prepared and used as light sources while InSb was utilized as the light detector. A total of 210 spectral lines were observed with two different resolutions of 0.004 and 0.006 cm−1, of which 166 lines are reported for the first time. New center of gravity wavenumber values are reported for all the observed lines.

Microwave-assisted UV digestion of starch and skimmed milk powder: Environmentally friendly protocol for essential and toxic elements determination

The present work evaluated a microwave-assisted wet digestion method using diluted HNO3 with in situ UV radiation for the digestion of starch and skimmed milk powder for further metals determination by spectrometric plasma-based techniques. The sample digestion was conducted using an in situ UV lamp (electrodeless discharge lamp), and the digestion efficiency was improved by employing O2 (20 bar) and 2 mL 30 % H2O2 as auxiliary reagents. The accuracy of the proposed digestion method was evaluated by metals determination (Ca, Cd, Cu, Fe, K, Mg, Mo, Mn, Na, Pb, and Zn) in certificated reference material, which agreed with certified values (Student t-test <0,05). With the use of a UV lamp an environmentally friendly protocol was developed for starch and skimmed milk powder digestion using 0.1 mol L−1 HNO3 with auxiliary reagents (H2O2 or O2). The RCC value ranged from 0.9 to 1.2 % (starch and skimmed milk powder, respectively). The simultaneous cooling approach further improved the digestion efficiency (RCC <0,3 % for both samples), allowing to use milder digestion conditions, or even just water, being environmentally friendly, reducing the waste generation and reagents consumption, allowing food quality control through a greener approach.

Oxidative and Photochemical Processes for Soft Drink–Industry Wastewater Treatment

Soft drinks–industry wastewater (SDIW) contains high concentrations of sugar (420–487 mg/L) and sodium (320–397 mg/L), has high pH (∼9), and contains biorefractory pollutants. Therefore, rapid and effective techniques are required for its treatment. In the present study, SDIW was subjected to microwave (MW) photocatalysis (PC) using electrodeless discharge lamps, and the outcomes were compared with other oxidative and photochemical advanced oxidation processes, including oxidation, MW oxidation (MWO), and ultraviolet–titanium dioxide PC, in terms of the removal efficiency of organics based on chemical oxygen demand (COD), total phosphate (TP), and total nitrogen (TN). The mineralization of organics was ∼3.5 times higher in the MWPC and MWO systems compared to the oxidation and PC systems. The COD removal efficiency after 60 min using the oxidation, PC, MWO, and MWPC systems was 22.7%, 25.41%, 79.36%, and 87.3%, respectively. Direct photolysis using UV (using 486 kJ/mole of energy) and photocatalytic degradation using increased hydroxyl radicals in the presence of MWs was the primary degradation mechanism in the MWPC system. The TP removal efficiency in the oxidation, PC, MWO, and MWPC systems was 15%, 40%, 50%, and 60%, respectively. The respective TN removal efficiencies for the four systems were 40%, 58%, 82%, and 85%. The main mechanism for organics, TP, and TN removal in the MWPC system involved the direct disruption of the chemical bonds of the organic molecules, photocatalytic phosphate reduction, and breaking of the primary amine bond in the organic nitrogen using the high-energy plasma and hotspots that formed in the MW-based systems. The electrical energy consumed by the systems [electrical energy per order (EEO)] occurred in the order PC > MWO > MWPC, with respective values of 14,614, 6,919, and 4,526 Rs/kg COD removal.

Hyperfine structure measurements on a forbidden transition of Bi I using fourier transform spectroscopy

Hyperfine structure (hfs) investigations have been performed on a forbidden transition of the Bi I emission spectral line in the visible region at 15,437.49 cm−1, between the levels 6p3 4S3/2 and 6p3 2D5/2, by means of a Fourier Transform spectrometer. Electrodeless discharge lamps (EDL) containing BiI3 were utilized to generate the bismuth plasma. In these observations, all the 6 components of electric quadrupole (ΔF = ±2) transitions have been detected for the first time, in addition to the 12 components of magnetic dipole (ΔF = 0, ±1) transitions. Magnetic dipole constant (A) and electric quadrupole constant (B) have been derived for the combining levels.

Comparison of bismuth atomic lamps for a non-dispersive atomic fluorescence spectrometry

The performance of two types of radiation sources – an electrodeless discharge lamp (EDL) and a boosted discharge hollow cathode lamp (Superlamp) – for atomic fluorescence spectrometry (AFS) was studied and compared using bismuth as a model analyte at 222.8 and 223.1 nm fluorescence lines. Hydride generation was used for analyte introduction to a miniature diffusion flame where the generated bismuthane was atomized. An in-house assembled non-dispersive atomic fluorescence spectrometer was adjusted so that either of the sources could be employed. The optimization of the radiation sources at chosen 40 Hz modulation rate included a duty cycle and applied currents (primary and boost), in addition to proper focusing on the flame atomizer. With optimum operation parameters the sensitivity achieved with the EDL was around an order of magnitude higher than that with the Superlamp, in agreement with the higher radiation intensity measured by an optical power meter and resulting limits of detection of 1.5 pg and 11 pg, for the EDL and the Superlamp, respectively.

Magnetic NiFe2O4 3D nanosphere photocatalyst: Glycerol-assisted microwave solvothermal synthesis and photocatalytic activity under microwave electrodeless discharge lamp

In this study, NiFe2O4 (NFO) nanocrystalline powder was synthesized using a glycerol-assisted microwave solvothermal process followed by annealing. In comparison with the traditional preparation method, this method does not require addition of any precipitate-controlling agents. The structural properties of NFO were characterized via different techniques, such as X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and ultraviolet–visible diffuse reflection spectra. The results suggested that the NFO crystal was a three-dimensional (3D) porous nanosphere with a diameter of approximately 400 nm, and the glycerol added during the preparation process played a crucial role in the formation of 3D nanospheres. The photocatalytic activity of NFO was evaluated by the degradation of methylene blue (MB) in a microwave electrodeless discharge lamp (MEDL) system. Additionally, the mechanism of MB photocatalytic degradation was studied. The results suggest that 88.6% of the MB degraded within 10 min under MEDL irradiation, and the mineralization rate reached 55%. The main active species of MB degradation were e-, h+, and •O2−. In addition, the cycle catalysis experiment confirmed the reusability of NFO 3D nanospheres. We believe that the NFO 3D nanospheres can serve as efficient photocatalysts suitable for MEDL systems.

Controlled synthesis and photocatalytic performance of biocompatible uniform carbon quantum dots with microwave absorption capacity

Carbon quantum dots (CQDs) were successfully prepared via a facile microwave-assisted method combined with a controlled drainage time using glucose as the carbon source. XRD analysis, FT-IR spectroscopy, UV spectroscopy, XPS, and PL spectroscopy were performed to characterize the structures and properties of the samples. The results showed that the average particle size of the prepared CQDs was about 2 nm, and there were two UV absorption at the wavelengths of 228 nm and 280 nm, respectively, corresponding to the π-π* transition of CC (atomic group) and the n-π* transition of the oxygen containing group (CO) on the surface of the carbon core. According to the unique optical and microwave absorption properties of the CQDs, a suitable photocatalytic system, namely, a microwave electrodeless discharge lamp (MEDL) system was used. In the MEDL system, the degradation rate of rhodamine B (RhB, 50 mL, 30 mg L−1) by 0.02 g CQDs-2 in 10 min could reach 85.79%. The photocatalytic activity of CQDs-2 was about twice that of P25. In addition, the biocompatibility of the CQDs was investigated, which revealed that the CQDs could be absorbed by microorganisms as a carbon source. The prepared CQDs are a promising environmentally friendly photocatalyst.

Hyperfine structure measurements of neutral atomic iodine (127I) in the infrared region (1800-6000 cm−1)

Experimental measurements of high resolution emission spectra of neutral atomic iodine (I I) have been extended to cover the mid-infrared spectral regions (1800–6000 cm−1) using Fourier transform spectroscopy. A total of 354 spectral lines are reported here in the above spectral range. While the region between 3000 and 6000 cm−1 were recorded using a conventional quartz Electrodeless Discharge lamps (EDL), spectra in the region 1800–3000 cm−1 were detected using specially prepared EDLs with a CaF2 window. Hyperfine structure analysis has been carried out on 224 spectral lines, of which 176 are reported for the first time. The magnetic dipole constant (A) and electric quadrupole constant (B) have been derived for 97 energy levels.

A Loss-Free Resistor-Based Versatile Ballast for Discharge Lamps

This paper presents a versatile ballast for discharge lamps, whose operation is based on the notion of a loss-free resistor (LFR). The ballast consists of two stages: (1) a boost converter operating in continuous conduction mode (CCM) and exhibiting an LFR behavior imposed by sliding-mode control; and (2) a resonant inverter supplying the discharge lamp at high frequencies. Thanks to this mode of operation, the power transferred to the lamp is regulated by the LFR input resistance, allowing successful ignition, warm-up, nominal, and dimming operation of a range of discharge lamps, with no need for complex regulation schemes based on lamp models. The versatility of the ballast has been experimentally proven for both conventional and electrodeless discharge lamps. Tests include induction electrodeless fluorescent (IEFL), high-pressure sodium (HPS) vapor, and metal-halide lamps.

Hyperfine structure measurements on singly ionized atomic iodine (I II) using fourier transform spectroscopy

Hyperfine structure (hfs) investigations were performed on singly ionized atomic iodine (I II) in the spectral region 12,000 - 24,000 cm−1, utilizing microwave discharge method in combination with high resolution Fourier Transform Spectroscopy (FTS). Electrodeless discharge lamps (EDL) were used to generate the iodine plasma. In the present work, 141 hyperfine spectral transitions are reported. Hfs measurements were carried out on 73 well resolved spectral lines and derived the magnetic dipole constant (A) and electric quadrupole constant (B) for 61 energy levels (29 even parity and 32 odd parity). Further, a magnetic dipole transition (14,366 cm−1) and a blended line (20,611 cm−1) have been observed.

Hyperfine structure measurements of neutral atomic iodine (127I) in near infrared and visible regions

Hyperfine structure (hfs) investigations were performed on neutral atomic iodine (II) in the near-infrared and visible spectral regions. Fourier transform spectroscopy to investigate the emission spectrum of a microwave driven electrodeless discharge lamp operated in a mixture of iodine vapor and Ne gas. In the present investigations, the observation of 240 hyperfine resolved spectral lines were reported. Hfs analysis was carried out on 128 spectral lines for the first time and repeated on 49 spectral lines. The magnetic dipole constant (A) and electric quadrupole constant (B) were derived for 100 energy levels. Among the 100 energy levels, A and B constants for 18 levels were presented for the first time.

Soft drink industry wastewater treatment in microwave photocatalytic system – Exploration of removal efficiency and degradation mechanism

The present study investigated the photolytic and photocatalytic treatment of soft drink industry wastewater (SDIW) in presence of microwave (MW) irradiation. The treatment efficiency was investigated in terms of removal rate of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphate (TP) in microwave photolysis (MWP) system, MW photocatalytic system with one and two electrodeless discharge lamp (EDL), denoted as MWPC-1 and MWPC-2 respectively. The MWPC-2 system showed highest efficiency with a COD, TKN and TP removal rate of 7.48, 82.5 and 0.63 mg/L/min respectively. The COD removal was achieved by direct interaction MW and UV with organics. The photocatalytic oxidation of NH3 to nitrite and nitrate at catalyst surface cause TKN removal from SDIW. On the other hand, major route of TP removal was phosphate reduction occurred in the aqueous phase. On the other hand, the desorption study performed with the catalyst used in the MWPC experiments indicated a TP concentration <2 mg/L and COD and TKN concentrations <5 mg/L indicating the complete removal of organic matter, TKN and TP from aqueous and solid phase during the MWPC process.

Combined microwave-induced and photocatalytic oxidation using zinc ferrite catalyst for efficient degradation of tetracycline hydrochloride in aqueous solution

In this research, ZnFe2O4 was employed as heterogeneous catalyst for the degradation of tetracycline hydrochloride (TCH) by a novel combined microwave-induced (MW-induced) and photocatalytic oxidation. The ZnFe2O4 catalyst was synthesized using co-precipitation method, and characterized by XRD, TEM, BET and UV–Vis DRS. A microwave electrodeless discharge lamp (MEDL) was introduced to this process as a light source. 91.6% of TCH degradation was obtained in MW/MEDL/ZnFe2O4 system in 4 min. ZnFe2O4 catalyst had both microwave-catalytic and visible-light photocatalytic activities. The operation parameters, such as microwave output, catalyst dosage, initial pH and recycle runs, showed different influence on TCH degradation. The analysis of degradation mechanism indicated that h+ was the main active species for TCH degradation and little O2−• active species generated in MW/MEDL/ZnFe2O4 system. The decomposition intermediates of TCH were identified by LC-MS.

Investigation of reactive oxygen species produced by microwave electrodeless discharge lamp on oxidation of dimethyl sulfide

Microwave electrodeless discharge lamp (MEDL) has been regarded as a powerful light source of photoreaction. Four kinds of chemicals, nitrogen (N2), oxygen (O2), water (H2O) and dimethyl sulfide (DMS), were used as molecular probes to explore the generation process of reactive oxygen species (ROS) and their photo-oxidation performances on the photodegradation of organic pollutants with application of an exterior MEDL system. ROS such as O (3P), O3, O (1D) and 1O2 were generated via irradiation of O2 and H2O except dry N2 by MEDL. They were transformed to other ROS including ·OH and H2O2 with increase of relative humidity. The ROS productivity was inhibited evidently by humidity and ·OH became the major active species at high humidity. An optimal mineralization rate of 23.6% for DMS photodegradation was reached in dry air compared with 8.74% at high humidity, which indicated that O (1D) and 1O2 were more powerful oxidants than O3 and OH. The results showed that the higher mineralization rate of organic pollutants was obtained by increasing the generation efficiency of ROS of O (1D) and 1O2. Furthermore, the results provided an alternative to develop intensification technology on photodegadation of organic pollutants with MEDL system and an optimal operation process including photocatalyst and humidity.

Hyperfine structure measurements of neutral iodine atom (127I) using Fourier Transform Spectrometry

We report the hyperfine Structure (hfs) splitting observations of neutral iodine atom (II) in the 6000 – 10,000 cm−1 near infrared spectral region. The measurements were carried out using a high-resolution Fourier Transform Spectrometer (FTS), where an electrodeless discharge lamp (EDL), excited using microwaves, was employed as the light source and InGaAs as the light detector. A specially designed setup was used to lower the plasma temperature of the medium so as to reduce the Doppler width and consequently to increase the spectral resolution of hfs components. A total of 183 lines with hfs splitting have been observed, out of which hfs in 53 spectral lines are reported for the first time. On the basis of hfs analysis, we derived the magnetic dipole and electric quadrupole coupling constants, A and B respectively for 30 even and 30 odd energy levels and are compared with the values available in the literature. New hfs values for 5 even and 4 odd levels are also reported here for the first time.

The process of atrazine degradation, its mechanism, and the formation of metabolites using UV and UV/MW photolysis

Abstract The photolytic degradationmechanism of atrazine using a UV reactor andUV/MW (electrodeless discharge lamp (Hg-EDL)) was investigated. After 120 s of UV photolysis partial degradation of atrazine had been observed and a subsequent formation of degradation products of atrazine-2-hydroxy, therefore, defining the path of atrazine degradation through UV photolysis. This system after 1200 s of exposure to UV radiation had not reached full degradation of atrazine, and its metabolite (atrazine-2-hydroxy), was the main by-product obtained for the process. When performing photolysis through the UV/Microwave combined methodcomplete atrazine degradation was obtained within a 5 s interval, besides the formation of five (5) degradation products, which are HAT, DEAT, DIAT, DEHAT and DIHAT. Therefore, defining the path of the photolytic degradation process through the UV/Microwave combined method. The total degradation of its metabolite (HAT) was observed for the period of 120 s of exposure to UV/MW radiation, and after that time there had been no signcorresponding to the respective compounds. The tests with the isolated microwave radiation were not efficient in the degradation of the atrazine and, therefore, the respective isolated energy is not applicable.The control of atrazine degradation and consequent formation of metabolites were accompanied by a high-performance liquid chromatography with a UV/Vis detector.

Visibility enhancement in two-dimensional lensless ghost imaging with true thermal light**Project supported by the National Natural Science Foundation of China (Grant Nos. 11204117, 11304007, and 60907031), the China Postdoctoral Science Foundation (Grant No. 2013M540146), the Fund from the Education Department of Liaoning Province, China (Grant No. L2012001), and the National Hi-Tech Research and Development Program of China (Grant No. 2013AA122902).

We report an experimental demonstration of two-dimensional (2D) lensless ghost imaging with true thermal light. An electrodeless discharge lamp with a higher light intensity than the hollow cathode lamp used before is employed as a light source. The main problem encountered by the 2D lensless ghost imaging with true thermal light is that its coherence time is much shorter than the resolution time of the detection system. To overcome this difficulty we derive a method based on the relationship between the true and measured values of the second-order optical intensity correlation, by which means the visibility of the ghost image can be dramatically enhanced. This method would also be suitable for ghost imaging with natural sunlight.

Comparison of Nitric Oxide Concentrations in μs- and ns-Atmospheric Pressure Plasmas by UV Absorption Spectroscopy

In this paper, an absorption spectroscopy measurement method was applied on two atmospheric pressure plasma sources to determine their production of nitric oxide. The concentrations are essential for evaluating the plasma sources based on the principle of the Dielectric Barrier Discharge (DBD) for applications in plasma medicine. The described method is based on a setup with an electrodeless discharge lamp filled with a mixture of oxygen and nitrogen. One of the emitted wavelengths is an important resonance wavelength of nitric oxide (λ = 226.2 nm). By comparing the absorption behaviour at the minimum and maximum of the spectral absorption cross section of nitric oxide around that wavelength, and measuring the change in intensity by the absorbing plasma, the concentration of nitric oxide inside the plasma can be calculated. The produced nitric oxide concentrations depend on the pulse duration and are in the range of 180 ppm to 1400 ppm, so that a distance of about 10cm to the respiratory tract is enough to conform to the VDI Guideline 2310.

Microwave-assisted ultraviolet digestion of petroleum coke for the simultaneous determination of nickel, vanadium and sulfur by ICP-OES

A method for the simultaneous determination of Ni, V and S in petroleum coke by inductively coupled plasma optical emission spectrometry (ICP-OES) after microwave-assisted ultraviolet digestion (MW-UV) in closed vessels was proposed. Digestion was performed using electrodeless discharge lamps positioned inside quartz vessels and turned on by microwave radiation. The following parameters were evaluated: HNO3 concentration (15mL of 1, 4, 7, 10 or 14.4molL−1), volume of H2O2 (30%, 1 or 3mL), sample mass (100, 250 or 500mg) and heating time (40 or 60min) with or without the use of UV lamps. Digestion efficiency was evaluated by the determination of the residual carbon content (RCC) in digests. Using UV lamps lower RCC was obtained and the combination of 4molL−1 HNO3 with 3mL of H2O2 and 60min of heating allowed a suitable digestion of up to 500mg of petroleum coke (RCC< 21%). The agreement with the reference values for Ni, V and S (obtained by digestion of petroleum coke by microwave-induced combustion) and with a certified reference material of petroleum coke was between 96 and 101%. The proposed method was considered as advantageous when compared to American Society for Testing and Materials method because it allowed the simultaneous determination of Ni, V and S with lower limit of detection (0.22, 0.12 and 8.7µgg−1 for Ni, V and S, respectively) avoiding the use of concentrated nitric acid and providing digests suitable for routine analysis by ICP-OES.

Population Distribution of Excited States in Cs Electrodeless Discharge Lamp**Supported by the National Natural Science Foundation of China under Grant Nos 11074011 and 91436210.

We measure the intensity of fluorescence spectral lines of Cs atoms in an electrodeless discharge lamp from visible light to the near-infrared region of 400–1000 nm. To build an excited state Faraday anomalous dispersion optical filter, the population ratios between the excited states are calculated by rate equations and the spontaneous transition probabilities. The electrodeless discharge lamp with populations in the excited states can be used to realize the frequency stabilization reference for lasers at multiwavelength and the excited state Faraday anomalous dispersion optical filter for submarine communication applications in blue—green wavelengths to simplify the system.