Decomposition of p-nonylphenols in water and elimination of their estrogen activities by 60Co γ-ray irradiation

Concentration of p-nonylphenols (NPs) in water at 1 μmol dm⁻³ was decreased exponentially with absorbed dose when NPs were irradiated by ⁶⁰Co γ-rays. Two products having molecular weight of 236, presumably OH adducts of NPs, were detected by LC–MS analyses. The elimination of estrogen activity of aqueous NPs solution including such irradiation products at 5000 Gy (J kg⁻¹) was confirmed by the yeast two-hybrid assay. These results should expand the application of ionizing radiation to the treatment of NPs.     

Decomposition of persistent pharmaceuticals in wastewater by ionizing radiation

Pharmaceuticals in wastewater were treated by the combined method of activated sludge and ionizing radiation in laboratory scale. Oseltamivir, aspirin, and ibuprofen at 5 μmol dm^?3 in wastewater were decomposed by the activated sludge at reaction time for 4 h. Carbamazepine, ketoprofen, mefenamic acid, clofibric acid, and diclofenac were not biodegraded completely, but were eliminated by γ-ray irradiation at 2 kGy. The rate constants of the reactions of these pharmaceuticals with hydroxyl radicals were estimated by the competition reaction method to be 4.0–10×10⁹ mol^?1 dm³ s^?1. Decompositions of the pharmaceuticals in wastewater by ionizing radiation were simulated by use of the rate constants and the amount of total organic carbon as parameters. Simulation curves of concentrations of these pharmaceuticals as a function of dose described the experimental data, and the required dose for the elimination of them in wastewater by ionizing radiation can be estimated by this simulation.     

Treatment of opium alkaloid containing wastewater in sequencing batch reactor (SBR)—Effect of gamma irradiation

Aerobic biological treatment of opium alkaloid containing wastewater as well as the effect of gamma irradiation as pre-treatment was investigated. Biodegradability of raw wastewater was assessed in aerobic batch reactors and was found highly biodegradable (83–90% degradation). The effect of irradiation (40 and 140 kGy) on biodegradability was also evaluated in terms of BOD₅/COD values and results revealed that irradiation imparted no further enhancement in the biodegradability. Despite the highly biodegradable nature of wastewater, further experiments in sequencing batch reactors (SBR) revealed that the treatment operation was not possible due to sludge settleability problem observed beyond an influent COD value of 2000 mg dm^?3. Possible reasons for this problem were investigated, and the high molecular weight, large size and aromatic structure of the organic pollutants present in wastewater was thought to contribute to poor settleability. Initial efforts to solve this problem by modifying the operational conditions, such as SRT reduction, failed. However, further operational modifications including addition of phosphate buffer cured the settleability problem and influent COD was increased up to 5000 mg dm^?3. Significant COD removal efficiencies (>70%) were obtained in both SBRs fed with original and irradiated wastewaters (by 40 kGy). However, pre-irradiated wastewater provided complete thebain removal and a better settling sludge, which was thought due to degradation of complex structure by radiation application. Degradation of the structure was observed by GC/MS analyses and enhancement in filterability tests.     

A simple method of electrochemical lithium intercalation within graphite from a propylene carbonate-based solution

Electrochemical lithium intercalation within graphite from 1 mol dm^− 3 solution of LiClO₄ in propylene carbonate (PC) was investigated at 25 and − 15 °C. Lithium ions were intercalated into and de-intercalated from graphite reversibly at − 15 °C despite the use of pure PC as the solvent. However, ceaseless solvent decomposition and intense exfoliation of graphene layers occurred at 25 °C. The results of the Raman spectroscopic analysis indicated that the interaction between PC molecules and lithium ions became weaker at − 15 °C by chemical exchange effects, which suggested that the thermodynamic stability of the solvated lithium ions was an important factor that determined the formation of a solid electrolyte interface (SEI) in PC-based solutions. Charge–discharge analysis revealed that the nature of the SEI formed at − 15 °C in 1 mol dm^− 3 of LiClO₄ in PC was significantly different from that formed at 25 °C in 1 mol dm^− 3 of LiClO₄ in PC containing vinylene carbonate, 3.27 mol kg^− 1 of LiClO₄ in PC, and 1 mol dm^− 3 of LiClO₄ in ethylene carbonate.     

Radiolytic degradation of 4-nitrophenol in aqueous solutions: Pulse and steady state radiolysis study

The radiation induced degradation of 4-nitrophenol (4-NP) has been studied by gamma irradiation, while the reactivity and spectral features of the short lived transients formed by reaction with primary transient radicals at different pHs has been investigated by pulse radiolysis technique. In steady state radiolysis a dose of 4.4 k Gy is able to degrade 98% of 1×10⁻⁴ mol dm⁻³ 4-NP. 4-NP has pK_a at 7.1, above which it is present in the anionic form. At pH 5.2, ^•OH and N₃^• radicals were found to react with 4-NP with rate constants of 4.1×10⁹ dm³ mol⁻¹ s⁻¹ and 2.8×10⁸ dm³ mol⁻¹ s⁻¹, respectively. Differences in the absorption spectra of species formed in the reactions of 4-NP with ^•OH and N₃^• radicals suggested that ^•OH radicals add to the aromatic ring of 4-NP along with electron transfer reaction, whereas N₃^• radicals undergo only electron transfer reaction. At pH 9.2, rate constants for the reaction of ^•OH radicals with 4-NP was found to be higher by a factor of 2 compared to that at pH 5.2. This has been assigned to the deprotonation of 4-NP at pH 9.2.     

Exhaustive radiolysis of 11 mM aqueous benzene solutions: effect of added oxygen

The gamma radiolysis of aqueous benzene solutions was studied under various conditions (oxygenated, aerated and anoxic) to ascertain the role that oxygen plays in the destruction of benzene. For the oxygenated and aerated systems, phenol and biphenyl were the major quantified products. For the anoxic system, phenol was the sole quantified product. Benzene was initially consumed with approximately the same yield in each of the three systems; G(–benzene) was 0.49 μmol J^–1. Initial yields of phenol, G(phenol), were found to be 0.12, 0.060 and 0.030 μmol J^–1 for the oxygenated, aerated and anoxic systems, respectively. Biphenyl was initially formed with G=0.028 and 0.019 μmol J^–1 in the oxygenated and aerated systems, respectively. The percent conversion of benzene to CO₂ after an absorbed dose of 2500 kGy was 55.1%, 30.5% and 12.5%, respectively, for the oxygenated, aerated and anoxic systems. The last traces of benzene disappeared by a dose of ca. 60 kGy in all three systems. A mechanism was proposed for each system that depended upon the presence or absence of O₂. The total solution toxicity for each system was calculated by summing the individual toxicities of benzene and each quantified product. For the oxygenated and aerated systems, the total solution toxicity was found to go through a maximum at a dose of 22 kGy and then decrease to a value below that of the original solution. The total solution toxicity of the anoxic system was found to decrease from the onset of irradiation.     

Kinetics of the diazotization and azo coupling reactions of procaine in the micellar media

The kinetics of the diazotization reaction of procaine in the presence of anionic micelles of sodium dodecyl sulfate (SDS) and cationic micelles of cetyltrimethyl ammonium bromide (CTAB), dodecyltrimethyl ammonium bromide (DDTAB) and tetradecyltrimethyl ammonium bromide (TDTAB) were carried out spectrophotometrically at λ_max = 289 nm. The values of the pseudo first order rate constant were found to be linearly dependent upon the [NaNO₂] in the concentration range of 1.0 × 10⁻³ mol dm⁻³ to 12.0 × 10⁻³ mol dm⁻³ in the presence of 2.0 × 10⁻² mol dm⁻³ acetic acid. The concentration of procaine was kept constant at 6.50 × 10⁻⁵ mol dm⁻³. The addition of the cationic surfactants increased the reaction rate and gave plateau like curve. The addition of SDS micelles to the reactants initially increased the rate of reaction and gave maximum like curve. The maximum value of the rate constant was found to be 9.44 × 10⁻³ s⁻¹ at 2.00 × 10⁻³ mol dm⁻³ SDS concentration. The azo coupling of diazonium ion with β-naphthol (at λ_max = 488) nm was found to linearly dependent upon [ProcN₂⁺] in the presence of both the cationic micelles (CTAB, DDTAB and TDTAB) and anionic micelles (SDS). Both the cationic and anionic micelles inhibited the rate of reactions. The kinetic results in the presence of micelles are explained using the Berezin pseudophase model. This model was also used to determine the kinetic parameters e.g. k_m, K_s from the observed results of the variation of rate constant at different [surfactants].     

High-energy ionising radiation initiated decomposition of acetovanillone

Hydroxyl radical, hydrated electron and hydrogen atom intermediates of water radiolysis react with acetovanillone with rate coefficients of (1.05±0.1)×10¹⁰, (3.5±0.5)×10⁹ and (1.7±0.2)×10¹⁰mol^?1 dm³ s^?1. Hydroxyl radical and hydrogen atom attach to the ring forming cyclohexadienyl type radicals. The hydroxyl–cyclohexadienyl radical formed in hydroxyl radical reaction in dissolved oxygen free solution partly transforms to phenoxyl radical. In the presence of O₂ phenoxyl radical formation and ring destruction are observed. Hydrated electron in O₂ free solution attaches to the carbonyl oxygen and undergoes protonation yielding benzyl type radical. In air saturated 0.5 mmol dm^?3 solution using 15 kGy dose most part of acetovanillone is degraded, for complete mineralisation five times higher dose is required. The experiments clearly show that acetovanillone can be efficiently removed from water by applying irradiation technology.     

Radiation induced degradation of pharmaceutical residues in water: Chloramphenicol

The γ-radiolytic degradation of chloramphenicol (CPL) was investigated in 0.1–1 mmol dm^?3 aqueous solutions at various radiation conditions. The destruction of CPL was monitored by UV–vis spectrophotometric method through the decrease in the intensity of the absorbance band at 276 nm. LC-MS/MS was used to identify the degradation products. Results indicate that ^?OH can add onto the CPL aromatic ring or can abstract H-atom from the side chain. The reductive dechlorination of CPL was also studied based on the reaction of e_aq^? with CPL. In 0.1 mmol dm^?3 solution above 2.5 kGy dose complete CPL degradation was achieved. In the presence of dissolved oxygen at relatively low dose, various oxidation products were observed. In the presence of tertiary butanol radical scavenger tertiary butanol group containing products were also detected. The toxicity increased as a function of dose to 1.0 kGy. At doses higher than 1.0 kGy the toxicity decreased continuously due to further degradation. It was also demonstrated that the O₂^??/HO₂^? pair has low reactivity in CPL solution.     

High energy induced decoloration and mineralization of Reactive Red 120 dye in aqueous solution: A steady state and pulse radiolysis study

Gamma radiation induced decoloration and degradation of aqueous solution of Reactive Red 120 dye (RR-120) have been investigated under different experimental conditions. Rate constants for the reaction of hydrated electron and hydroxyl radical with RR-120 were determined to be 1.2×10¹⁰ and 7.9×10⁹ mol^?1 dm³ s^?1, respectively, by pulse radiolysis technique. The decoloration and degradation efficiency were measured in terms of % decoloration and % TOC, respectively. Decoloration was observed to be most efficient under reducing condition, where the radiolytic yield for the decoloration of dye was determined to be 0.14 μmol/J. The extent of decoloration for both aerated and oxygen saturated solution was almost identical, whereas it decreased in N₂O saturated solution as well as N₂ saturated solution. For a solution having 10.56 μg/ml total organic carbon (TOC) at a dose of 3 kGy, 48% mineralization takes place in oxygen saturated solution whereas under aerated condition same was observed to be lowered to 38%.     

Catalytic effect of CTAB on the interaction of dipeptide glycyl-tyrosine (Gly-Tyr) with ninhydrin

The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the interaction of dipeptide glycyl-tyrosine (Gly-Tyr) with ninhydrin under varying conditions has been studied spectrophotometrically at 70 °C and pH 5.0. The reaction followed first- and fractional-order kinetics with respect to [Gly-Tyr] and [ninhydrin], respectively. Increase in total concentration of CTAB from 0 to 70 × 10⁻³ mol dm⁻³ resulted in an increase in the pseudo-first-order rate constant (k_ψ) by a factor of ca. 3. Quantitative kinetic analysis of k_ψ − [CTAB] data was performed on the basis of pseudo-phase model of the micelles (proposed by Menger and Portnoy and developed by Bunton) and Piszkiewicz model. A possible mechanism has been proposed and the kinetic data have been used to evaluate the micellar binding constants K_S (268 mol⁻¹ dm³ for Gly-Tyr) and K_N (64 mol⁻¹ dm³ for ninhydrin).     

A direct borohydride–peroxide fuel cell using a Pd/Ir alloy coated microfibrous carbon cathode

A direct borohydride fuel cell with a Pd/Ir catalysed microfibrous carbon cathode and a gold-catalysed microporous carbon cloth anode is reported. The fuel and oxidant were NaBH₄ and H₂O₂, at concentrations within the range of 0.1–2.0 mol dm⁻³ and 0.05–0.45 mol dm⁻³, respectively. Different combinations of these reactants were examined at 10, 25 and 42 °C. At constant current density between 0 and 113 mA cm⁻², the Pd/Ir coated microfibrous carbon electrode proved more active for the reduction of peroxide ion than a platinised-carbon one. The maximum power density achieved was 78 mW cm⁻² at a current density of 71 mA cm⁻² and a cell voltage of 1.09 V.     

Enhanced mass transfer during solid–liquid extraction of gamma-irradiated red beetroot

The exposure to gamma-irradiation pretreatment increases cell wall permeabilization, resulting in loss of turgor pressure, which led to the increase of extractability of betanin from red beetroot. The degree of extraction of betanin was investigated using gamma irradiation as a pretreatment prior to the solid–liquid extraction process and compared with control beetroot samples. The beetroot subjected to different doses of gamma irradiation (2.5, 5.0, 7.5, 10.0 kGy) and control was dipped in an acetic acid medium (1% v/v) to extract the betanin. The diffusion coefficients for betanin as well as ionic component were estimated considering Fickian diffusion. The results indicated an increase in the diffusion coefficient of betanin (0.302×10⁻⁹–0.463×10⁻⁹ m²/s) and ionic component (0.248×10⁻⁹–0.453×10⁻⁹ m²/s) as the dose rate increased (from 2.5 to 10.0 kGy). The degradation constant was found to increase (0.050–0.079 min⁻¹) with an increase gamma-irradiation doses (2.5–10.0 kGy), indicating lower stability of the betanin as compared to control sample at 65 °C.     

Analysis and identification of irradiated Spirulina powder by a three-step infrared macro-fingerprint spectroscopy

A three-step infrared (IR) macro-fingerprint method combining conventional IR spectra, and the secondary derivative spectra with two-dimensional infrared correlation spectroscopy (2D-IR), was developed to analyze Spirulina powder before and after gamma irradiation. In the IR spectra, most of the absorption peaks of samples irradiated at 1, 2.7, 6, and 10.4 kGy had lower intensities than the non-irradiated ones, whereas peaks at 1152, 1078, and 1051 cm⁻¹ were slightly enhanced with irradiation at 2.7, 6, and 10.4 kGy. Their second derivative spectra amplified the differences and revealed that irradiation affected the C=O band of carboxylic acid and esters, and the N–H band of proteins. The peaks at 1746 and 1741 cm⁻¹, and those at 1730 and 1725  cm⁻¹ became two broad peaks. Meanwhile, the three sharp peaks at 1548 cm⁻¹, 1544 cm⁻¹ and 1536 cm⁻¹ changed to two broad peaks at around 1547 and 1534 cm⁻¹ after irradiation at doses higher than 1 kGy. The characteristic IR bands from 1700 cm⁻¹ to 1600 cm⁻¹, which represent the C=O band in proteins, also have different shapes and intensities after irradiation. The finding indicated that irradiation affected the secondary structures of protein which was confirmed by curve fitting results. During the process of increasing the temperature from 50 to 210 °C, the ratio of amide I to II in absorption intensities in the 2D-IR spectra of the irradiated samples varied with different response for different samples. Saccharides in Spirulina powder had a higher thermostability than proteins, but the autopeaks of irradiated samples did show differences from the non-irradiated sample. The intensity of autopeaks at 1012 cm⁻¹ increased dramatically in the irradiated samples while that of peaks at 1053, 1071, and 1083 cm⁻¹ decreased after irradiation. Based on the three-step IR macro-fingerprint method, irradiated Spirulina powder samples were successfully and fast identified and discriminated.     

Synthesis of silver nanoparticles supported on silica aerogel using gamma radiolysis

Silver clusters on SiO₂ support have been synthesized using ⁶⁰Co gamma radiation. The irradiation of Ag⁺ in aqueous suspension of SiO₂ in the presence of 0.2 mol dm⁻³ isopropanol resulted in the formation of yellow suspension. The absorption spectrum showed a band at 408 nm corresponding to typical characteristic surface plasmon resonance of Ag nanoparticles. The effect of Ag⁺ concentration on the formation of Ag cluster indicated that the size of Ag clusters vary with Ag⁺ concentration, which was varied from 4×10⁻⁴ to 5×10⁻³ mol dm⁻³. The results showed that Ag clusters are stable in the pH range of 2–9 and start agglomerating in the alkaline region at pH above 9. The effect of radiation dose rate and ratio of Ag⁺/SiO₂ on the formation of Ag clusters have also been investigated. The prepared clusters have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), which showed the particle size of Ag clusters to be in the range of 10–20 nm.     

Decomposition of 14C containing organic molecules released from radioactive waste by gamma-radiolysis under repository conditions

Decomposition of ¹⁴C containing organic molecules into an inorganic compound has been investigated by γ-ray irradiation experiments under simulated repository conditions for radioactive waste. Lower molecular weight organic acids, alcohols, and aldehydes leached from metallic waste are reacted with OH radicals to give carbonic acid. A decomposition efficiency that expresses consumption of OH radicals by decomposition reaction of organic molecules is proposed. Decomposition efficiency increases with increasing concentration of organic molecules (1×10⁻⁶–1×10⁻³ mol dm⁻³) and is not dependent on dose rate (10–1000 Gy h⁻¹). Observed dependence indicates that decomposition efficiency is determined by reaction probability of OH radicals with organic molecules.     

Reactivity of H atoms and hydrated electrons with chlorobenzoic acids

H radicals react with chlorobenzoic acids and chlorobenzene (k(H+substrates)=(0.7–1.5)×10⁹ dm³ mol⁻¹ s⁻¹) by addition to the benzene ring forming H adducts with characteristic absorption bands in the range of 310–360 nm. The rate constants for their second-order decay are 2k=(3.5–6)×10⁸ dm³ mol⁻¹ s⁻¹. By reduction with e_aq⁻ fragmentation and chloride release was established for 2- and 4-chlorobenzoic acid, for 3-chlorobenzoic acid the addition of electrons to the carboxylate group was observed by pulse radiolysis. By gamma radiolysis could be proved that these radical anions undergo intramolecular electron transfer and quantitave dechlorination. The efficiency in degradation was 4-chlorobenzoic acid>3-chlorobenzoic acid>2-chlorobenzoic acid. Benzoic acid was found as final product for all substrates.     

Photocatalysis of 4-nitrophenol using zinc phthalocyanine complexes

Photodegradation of 4-nitrophenol (4-Np) in the presence of zinc tetrasulfophthalocyanine (ZnPcS₄), zinc octacarboxyphthalocyanine (ZnPc(COOH)₈) and a sulfonated ZnPc containing a mixture of differently sulfonated derivatives (ZnPcS_mix), as photocatalysts is reported. ZnPcS_mix is the most effective catalyst in terms of a high quantum yield for 4-Np degradation and the stability of the catalyst. However ZnPc(COOH)₈ degrades readily during the catalysis, but it has a higher quantum yield (Φ_4-Np) for 4-Np degradation than the rest of the complexes. The Φ_4-Np values were closely related to the singlet oxygen quantum yields Φ_Δ and hence aggregation. The rate constants for the reaction with 4-Np were k_r = 0.67 × 10⁶ mol⁻¹ dm³ s⁻¹ for ZnPcS_mix and 2.8 × 10⁸ mol⁻¹ dm³ s⁻¹ for ZnPc(COOH)₈.     

Gold nanoparticles/tetraaminophenyl porphyrin functionalized multiwalled carbon nanotubes nanocomposites modified glassy carbon electrode for the simultaneous determination of p-acetaminophen and p-aminophenol

A novel electrochemical platform was designed and prepared for simultaneous determination of p-acetaminophen (AMP) and p-aminophenol (AP) by combining the excellent conductivity and electrocatalytic activities of tetraaminophenyl porphyrin functionalized multi-walled carbon nanotubes (CNTs-CONH-TAPP) and gold nanoparticles (AuNPs). The as-synthesized CNTs-CONH-TAPP composites were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscope. The incisive oxidation current responses of AMP and AP at the modified electrode promised a sensitive and selective simultaneous determination of AMP and AP. Under optimized conditions, the peak currents were directly proportional to the concentrations of AMP and AP over the ranges of 4.5–500 μmol L⁻¹ and 0.08–60 μmol L⁻¹, respectively, and the limits of detection were 0.44 μmol L⁻¹ for AMP and 0.025 μmol L⁻¹ for AP(S/N = 3) respectively. The proposed modified electrode showed excellent selectivity, reproducibility and long-term stability and could be applied in simultaneous determination of p-acetaminophen and p-aminophenol in real samples.     

Degradation of chlorophenols in aqueous solution by γ-radiation

Degradation of chlorophenols (CPs) in aqueous solutions by γ-radiation was studied. The effect of absorbed dose on degradation, dechlorination and mineralization of CPs were investigated. The results indicated that the degradation of CPs, Cl⁻ release and mineralization increased with increase in absorbed dose. When the initial concentration was 100 mg L⁻¹ and the dosage was 6 kGy, the removal efficiencies of CPs were 44.54% for 2-CP, 91.46% for 3-CP, 82.72% for 4-CP and 93.25% for 2,4-DCP, respectively. The combination of irradiation and H₂O₂ leads to a synergistic effect, which remarkably increased the degradation efficiency of CPs and TOC removal. The kinetics of CPs during irradiation are also mentioned.