Irradiation Of Aqueous Solutions Research Articles

Light-modulated aggregation behavior of some unsubstituted cinnamate-based ionic liquids in aqueous solutions

The aggregation behavior of a new class light-responsive ionic liquids was modulated efficiently by UV light irradiation in aqueous solutions.

Transformation of Phenylphenol Isomers by UVC Irradiation in Aqueous Solution

AbstractThe objective of this work was to study the photochemical behavior of ortho-phenylphenol (o-PP), metaphenylphenol (m-PP) and para-phenylphenol (p-PP) aqueous solutions exposed to 254 nm radiation. The influence of various reaction parameters on degradation rate was examined. Moreover, degradation products and toxicity of the reaction solutions were studied. It was observed that photolysis of phenylphenols was dependent on oxygen concentration in the reaction solution. The presence of radical and singlet oxygen scavengers in the reaction solution did not affect the photolytic degradation of the studied compounds. The values of apparent quantum yields of o-PP, m-PP and p-PP photolysis at pH 7 were equal to 0.019±0.00043, 0.023±0.00038 and 0.014±0.00083, respectively. The main intermediates of phenylphenols phototransformation were isomers of dihydroxybiphenyl. The degradation of phenylphenols during photolysis by 254 nm radiation ran quite fast. However, for the total mineralization of these compounds in water several times higher UV doses than those usually applied during UV disinfection process were required.

Singlet oxygen generation from Li⁺@C⁺₆₀ nano-aggregates dispersed by laser irradiation in aqueous solution.

Laser pulse irradiation of a deaerated aqueous solution containing the solid state lithium ion-encapsulated fullerene resulted in the formation of highly dispersed nano-aggregates (Li(+)@C60)n. Photoirradiation of an O2-saturated D2O solution containing (Li(+)@C60)n gave singlet oxygen with 55% quantum yield, leading to efficient double-stranded DNA cleavage.

Valence Stabilization of Polyvalent Uranium Ions in Presence of Some Organic Additives during Extended Gamma Irradiation of Their Aqueous Acidic Solutions

In gamma irradiated aqueous acidic uranium solutions, tetravalent uranium ions are easily oxidized while U(VI) ions remain unchanged. In general, valence change of polyvalent metallic ions during chemical reprocessing of spent nuclear fuel solutions can lead to undesirable effects under the influence of the existing gamma radiations. Consequently, studies on valence stabilization of Uranium ions during chemical treatment in strong gamma irradiation fields seem to be highly interesting. It has been reported before that some organic compounds proved to be effective in stabilizing the valence of Fe(II) ions during extended gamma irradiation of their acidic solutions. In the present work, valence stabilization of Uranium ions in acidic solutions in presence of different classes of organic compounds has been studied. The results showed that in case of U(IV), methanol or formic acid are capable of providing about 80% protection while ethanol or acetaldehyde can provide about 70% protection. Propanol has the least protective effect i.e. about 54%. On using U(VI) instead of U(IV) in the irradiated solutions, the uranium ions were reduced and the formed U(IV) was protected as follows: formic acid or methanol can provide 69% or 63% protection respectively while ethanol, acetaldehyde or propanol can provide 50%, 35% and 24% respectively. In any case, protection exists as long as the organic additives were not completely consumed.

Efficient size control of copper nanoparticles generated in irradiated aqueous solutions of star-shaped polyelectrolyte containers.

The formation of copper nanoparticles (Cu-NPs) in irradiated aqueous solutions of star-shaped poly(acrylic acid) (PAA) were studied at two pH values. Transmission electron microscopy (TEM) demonstrates that the star-shaped macromolecules loaded with Cu(2+) ions can act as individual nanosized containers providing a perfect control over the size and size distribution of Cu-NPs. Electron paramagnetic resonance (EPR) and optical spectroscopy show a transformation of mechanisms controlling the reduction of Cu(2+) ions and the further formation of Cu-NPs. At pH 2.9, Cu-NPs are formed from the aquacomplexes of Cu(2+) ions through homogeneous nucleation. At pH 4.3, the formation of Cu-NPs occurs inside macromolecular containers loaded with Cu(2+) ions, which are bound to carboxylic groups of the polyelectrolyte. In the latter case, Cu-NPs apparently ripen from preformed hydrated Cu2O seeds, which are thought to result from the ultrasmall (Cu(2+))m(OH(-))k(COO(-))n species, thus implying a heterogeneous nucleation.

Characterization of stable and transient cavitation in megasonically irradiated aqueous solutions

Megasonic cleaning is routinely used for removal of particulate contaminants from various surfaces in integrated circuit industry. One of the drawbacks of megasonic cleaning is that although it can achieve good particle removal efficiencies at high power densities, it also causes feature damage. The current paradigm is that damage is primarily caused by transient cavitation whereas cleaning is affected by streaming and stable cavitation. In order to develop a damage-free and effective megasonic cleaning process, it is essential to understand the acoustic bubble behavior and identify conditions that generate significant stable cavitation without any transient cavitation. In the current work, microelectrode based chronoamperometry, pressure measurements using a hydrophone and fluorescence spectroscopy studies were conducted under different acoustic frequencies (1–3MHz) and power densities (2–8W/cm2) to fundamentally investigate the type of cavitation produced under these conditions and also establish a correlation to the generation of hydroxyl radicals for characterization of transient cavitation.

Heterogeneous radiolysis of urea. Implications in astrobiology and prebiotic chemistry

Abstract Urea is an organic molecule present in most living organisms. Historically, it was the first organic molecule synthesized in the laboratory. In prebiotic chemistry, urea readily forms in different laboratory simulations using different energy sources. Furthermore, the role of solid surfaces, particularly minerals, might have been crucial to increase the complexity of the organic matter which may have led to the subsequent emergence of life on Earth. In this work, the radiolysis of urea in presence of a clay is studied to determine to what extent the mineral surfaces influence the decomposition of organics. The results indicate that urea is relatively stable to ionizing radiation in aqueous solutions and up to 20 kGy no decomposition is observed. Moreover, the presence of sodium montmorillonite, by a mechanism until now unknown, affects the radiolytic behavior and urea remains in the heterogeneous solution without a change in concentration even at very high doses (140 kGy). These results indicate that solids could have protected some organics, like urea, from degradation enabling them to remain in the environment on the primitive Earth.

Methylene blue photocatalytic degradation under visible irradiation on TiO2 thin films sensitized with Cu and Zn tetracarboxy-phthalocyanines

Abstract We studied the effect of sensitization on photocatalytic properties of TiO2 thin films. We synthesized tetracarboxy-phthalocyanines of Cu (PcTcCu) and Zn (PcTcZn) for using Achar method; TiO2 thin films were deposited by doctor blade method, after that, thin films were sensitized through chemisorption method. Properties of TiO2 and sensitized-TiO2 thin films were studied by measurements of X-ray diffraction (XRD), infrared spectroscopy (IR) and absorption diffuse reflectance. The XRD patterns indicated that sensitization did not affect the crystalline phases radio of the TiO2 films; furthermore, the optical analysis showed that after sensitization process TiO2 photophysical properties improved greatly in visible regions. Photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution and, the pseudo-first order model was used to obtain kinetic information of the photocatalytic degradation. Results indicated that photocatalytic activities of PcTcZn–TiO2 and PcTcCu–TiO2 were 2.8 times and 3.6 times better than TiO2 thin films, these results also indicated that magnetic properties of metal complex in the phthalocyanines determines the efficiency of sensitizer in photocatalytic process. Finally the efficiency in photocatalytic process improved greatly when methylene blue photo-degradation were assisted with slight amount of H2O2.

Photo and radiation induced synthesis of (Ni, Zn)O or mixed NiO–ZnO oxides

A set of mixed oxide samples containing crystalline NiO–ZnO with variable composition was prepared by irradiation of aqueous solutions containing nickel and/or zinc nitrate hexahydrate, with subsequent heat treatment. Due to irradiation, either by accelerated electrons or UV light, weakly crystalline solid precursor was formed. After heat treatment at temperatures of 300 °C or higher, nanocrystalline NiO, ZnO and mixture of ZnO and solid solution (Ni, Zn)O were formed, with different amounts of nickel or zinc. Photo or radiation induced synthesis yielded material with quality nanocrystals (from one to twenty nm) and very high specific surface area.

Mineralization of paracetamol in aqueous solution with advanced oxidation processes

Paracetamol is a common analgesic drug widely used in all regions of the world more than hundred tonnes per year and it poses a great problem for the aquatic environment. Its phenolic intermediates are classified as persistent organic pollutants and toxic for the environment as well as human beings. In the present study, the irradiation of aqueous solutions of paracetamol with 60Co gamma-rays was examined on a laboratory scale and its degradation path was suggested with detected radiolysis products. The synergic effect of ozone on gamma-irradiation was investigated by preliminary ozonation before irradiation which reduced the irradiation dose from 5 to 3 kGy to completely remove paracetamol and its toxic intermediate hydroquinone from 6 to 4 kGy as well as increasing the radiation chemical yield (Gi values 1.36 and 1.66 in the absence and presence of ozone, respectively). The observed amount of formed hydroquinone was also decreased in the presence of ozone. There is a decrease in pH from 6.4 to 5.2 and dissolved oxygen consumed, which is up to 0.8 mg l−1, to form some peroxyl radicals used for oxidation. Analytical measurements were carried out with gas chromatography/mass spectrometry and ion chromatography (IC) both qualitatively and quantitatively. Amounts of paracetamol and hydroquinone were measured with gas chromatography after trimethylsilane derivatization. Small aliphatic acids, such as acetic acid, formic acid and oxalic acid, were measured quantitatively with IC as well as inorganic ions (nitrite and nitrate) in which their yields increase with irradiation.

Highly efficient conductivity modulation of cinnamate-based light-responsive ionic liquids in aqueous solutions.

A new class of cinnamate-based light-responsive ionic liquids was synthesized and characterized, and these ionic liquids with longer alkyl chains showed a remarkable increase in ionic conductivity under UV light irradiation in aqueous solutions.

TiO2/graphene-like photocatalysts for selective oxidation of 3-pyridine-methanol to vitamin B3 under UV/solar simulated radiation in aqueous solution at room conditions: The effect of morphology on catalyst performances

Graphene-like layers, synthesized through a two-step oxidation/reduction wet treatment of a high surface carbon black, have been used to prepare composites with TiO2 nanoparticles by liquid phase deposition, followed by calcination at 200°C. The photocatalytic activity of the TiO2/graphene-like composites has been tested for the selective conversion of 3-pyridine methanol to 3-pyridine carboxyaldehyde and nicotinic acid (vitamin B3), under de-aerated and UV/solar simulated conditions, in the presence of cupric ions. Two different composite morphologies have been explored and a dependence of the photocatalytic activity has been assessed. An enhanced photocatalytic activity, with respect to the neat TiO2, has been observed and attributed to the broader variety of stable free-radical species generated, at a given photo-catalyst morphology, within the delocalized π-electron systems.

Radiation-assisted synthesis of iridium and rhodium nanoparticles supported on polyvinylpyrrolidone

The controlled synthesis of rhodium (Rh) and iridium (Ir) nanoparticles was carried out by gamma irradiation of aqueous solutions containing the metal precursor salt and polyvinylpyrrolidone (PVP). The nanoparticles were synthesized at various PVP and precursor concentrations with absorbed doses between 20 and 60 kGy. Nanoparticles with average sizes of 2.4 and 2.6 nm and narrow particle size distributions were obtained at metal precursor/PVP concentrations of 6/0.3 and 6/3 mM for Ir and Rh when irradiated at 60 kGy. The interaction of the nanoparticles surfaces with the PVP was studied.

A new mechanism for hydroxyl radical production in irradiated nanoparticle solutions.

The absolute yield of hydroxyl radicals per unit of deposited X-ray energy is determined for the first time for irradiated aqueous solutions containing metal nanoparticles based on a "reference" protocol. Measurements are made as a function of dose rate and nanoparticle concentration. Possible mechanisms for hydroxyl radical production are considered in turn: energy deposition in the nanoparticles followed by its transport into the surrounding environment is unable to account for observed yield whereas energy deposition in the water followed by a catalytic-like reaction at the water-nanoparticle interface can account for the total yield and its dependence on dose rate and nanoparticle concentration. This finding is important because current models used to account for nanoparticle enhancement to radiobiological damage only consider the primary interaction with the nanoparticle, not with the surrounding media. Nothing about the new mechanism appears to be specific to gold, the main requirements being the formation of a structured water layer in the vicinity of the nanoparticle possibly through the interaction of its charge and the water dipoles. The massive hydroxyl radical production is relevant to a number of application fields, particularly nanomedicine since the hydroxyl radical is responsible for the majority of radiation-induced DNA damage.

Controlled Cavitation at Nano/Microparticle Surfaces

Here we proposed a model that describes the nucleation of cavitation bubbles on nano/microparticle surfaces, which is of significance for the yet unsolved problem of particle-cavitation interaction. The model was verified through rational experimental design varying parameters including particle size, their shapes and additives. The surface morphology evolution of particles under high intensity ultrasonic irradiation in aqueous solution can be tailored by changing the nucleation energy barrier of cavitation bubbles on particle surfaces. Cavitation-induced breakage of particles under sonication has also been addressed, which predicts the critical effect of the initial size of solid particles in affecting ultrasound-driven intraparticle fracture. These results shed light on the effect of commonly used sonication treatments on nanostructured materials and sonochemical surface modification in particle science and technology.

Visible light induced degradation of chlorophenols in the presence of H2O2 and iron substituted polyoxotungstate

Abstract A water-soluble and pale-yellow Keggin-type iron (III) substituted polyoxotungstate (PW 11 Fe) has been examined as a photocatalyst for chlorophenol degradation in water under visible light at wavelengths longer than 420 nm. In an aerated aqueous solution, PW 11 Fe was not active for the photodegradation of phenol, 4-chlorphenol (4-CP), 2,4-dichlophenol and 2,4,6-trichlorophenol, except that H 2 O 2 was also added. However, all the observed reactions of organic degradation were slow in the beginning, followed by a fast, first-order process. As the initial concentration of PW 11 Fe or H 2 O 2 increased, this induction period for 4-CP degradation declined, together with increase in the overall reaction rate. During 4-CP degradation, chloride ions were produced, the amount of which was about 94% of the 4-CP degraded, while 1,4-benzoquinone, 2-hydroxy-BQ, catechol, and 4-chlorocatechol were identified as the main intermediates, all of which were degradable in situ. Moreover, 4-CP could degrade at initial pH 2.2−7.2, whereas PW 11 Fe was stable. Through a spin-trapping electron paramagnetic resonance spectroscopy, hydroxyl radicals were found in the irradiated aqueous solution of PW 11 Fe and H 2 O 2 . Finally, a plausible mechanism responsible for the observed slow and fast phases of 4-CP degradation is proposed, involving photolysis of a PW 11 Fe complex with H 2 O 2 , the Fenton-type production of hydroxyl radicals, and BQ photolysis.

Additive-Free Gold Nanoparticles Synthesized by Gamma-Ray Irradiation: Applications in Electrocatalysis and Surface-Enhanced Raman Scattering

Additive-free gold nanoparticles (AuNPs) were successfully synthesized by gamma ray irradiation in aqueous solution using HAuCl4 as precursor. The size was optimized by regulating the concentration of HAuCl4 and the dose of irradiation. The electrocatalytic performance of AuNPs for the oxidation of glucose was demonstrated. The obtained AuNPs displayed superior electrocatalysis for the oxidation of glucose with a linear response range from 50 μM to 16 mM, and the limit of detection was estimated to be 14.2 μM. The surface-enhanced Raman scattering (SERS) activity of the synthesized AuNPs was also investigated, which showed excellent SERS enhancement in the low concentration detection (1 × 10−7 M) of Rhodamine 6G solution with an enhancement factor of 1.4 × 106.

The Photocatalytic Conversion of (Biodiesel Derived) Glycerol to Hydrogen - A Short Review and Preliminary Experimental Results Part 2: Photocatalytic Conversion of Glycerol to Hydrogen in Batch and Semi-batch Laboratory Reactors

AbstractThe paper presents a short review of published results about different methods of waste glycerol conversion to the various chemicals and energy carriers as well the preliminary experimental results of the photocatalytic glycerol conversion into hydrogen. The first part of the paper presents literature data pertaining to the glycerol utilization, including thermal methods (incineration, pyrolysis, gasification and reforming), catalytic oxidation, chemical and biochemical conversion and photoconversion into hydrogen, are presented. The mechanism of selected processes and reaction conditions are also discussed. The second part of the paper presents the results of the hydrogen production over irradiated aqueous glycerol solution containing TiO

The Photocatalytic Conversion of (Biodiesel Derived) Glycerol to Hydrogen - A Short Review and Preliminary Experimental Results Part 1: A Review

AbstractThe paper presents a short review of published results about different methods of waste glycerol conversion to the various chemicals and energy carriers as well the preliminary experimental results of the photocatalytic glycerol conversion into hydrogen. The first part of the paper presents literature data pertaining to the glycerol utilization, including thermal methods (incineration, pyrolysis, gasification and reforming), catalytic oxidation, chemical and biochemical conversion and photoconversion into hydrogen, are presented. The mechanism of selected processes and reaction conditions are also discussed. The second part of the paper presents the results of the hydrogen production over irradiated aqueous glycerol solution containing TiO

The effect of dichlorophen binding to silica nanoparticles on its photosensitized degradation in water

The production of dichlorophen (2,2′-methylenebis(4-chlorophenol), DCP) and its use as an anthelmintic and in pesticide products result in its direct release to the environment. To the purpose of modelling the possible photodegradation routes of DCP sorbed on sediments or suspended particles, the synthesis and characterization of silica nanoparticles modified with DCP (NP–DCP) is reported.The reactivity of NP–DCP with the excited states of riboflavin, a sensitizer usually present in natural waters, and with singlet oxygen were investigated. Comparison of the kinetic results obtained here to those previously reported for irradiated aqueous solutions of DCP allowed the discussion of the effect of adsorption of the pesticide on its photodegradation.We show with the aid of computer simulations that in natural waters the relevance of the different photodegradation routes dichlorophen is very much affected by attachment to sediments.