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1.
J Phys Chem A ; 120(1): 118-27, 2016 Jan 14.
Artículo en Inglés | MEDLINE | ID: mdl-26673943

RESUMEN

In the present study, a novel TiO2/Ti film with enhanced {001} facets was synthesized by the hydrothermal technique followed by calcination for studying the removal of bezafibrate (BZF), from an aqueous environment. The synthesized photocatalyst was characterized by FE-SEM, XRD, HR-TEM, and PL-technique. The second-order rate constant of (•)OH with BZF was found to be 5.66 × 10(9) M(-1) s(-1). The steady state [(•)OH] was measured as 1.16 × 10(-11) M, on the basis of oxidation of terephthalic acid. The photocatalytic degradation of BZF followed pseudo-first-order kinetics according to the Langmuir-Hinshelwood model (k1 = 2.617 mg L(-1) min(-1) and k2 = 0.0796 (mg L(-1))(-1)). The effects of concentration and the nature of various additives including inorganic anions (NO3(-), NO2(-), HCO3(-), CO3(2-), Cl(-)) and organic species (fulvic acid) and initial solution pHs (2, 4, 6, 9) on photocatalytic degradation of BZF were investigated. It was found that the nature and concentration of studied additives significantly affected the photocatalytic degradation of BZF. The efficiency of the photocatalytic degradation process in terms of electrical energy per order was estimated. Degradation schemes were proposed on the basis of the identified degradation byproducts by ultraperformance liquid chromatography.

2.
J Phys Chem A ; 120(50): 9916-9931, 2016 Dec 22.
Artículo en Inglés | MEDLINE | ID: mdl-27959545

RESUMEN

In this study, a novel immobilized TiO2/Ti film with exposed {001} facets was prepared via a facile one-pot hydrothermal route for the degradation of norfloxacin from aqueous media. The effects of various hydrothermal conditions (i.e., solution pH, hydrothermal time (HT) and HF concentration) on the growth of {001} faceted TiO2/Ti film were investigated. The maximum photocatalytic performance of {001} faceted TiO2/Ti film was observed when prepared at pH 2.62, HT of 3 h and at HF concentration of 0.02 M. The as-prepared {001} faceted TiO2/Ti films were fully characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), and X-ray photoelectron spectroscopy (XPS). More importantly, the as-prepared {001} faceted TiO2/Ti film exhibited excellent photocatalytic performance toward degradation of norfloxacin in various water matrices (Milli-Q water, tap water, river water and synthetic wastewater). The individual influence of various anions (SO42-, HCO3-, NO3-, Cl-) and cations (K+, Ca2+, Mg2+, Cu2+, Na+, Fe3+) usually present in the real water samples on the photocatalytic performance of as-prepared TiO2/Ti film with exposed {001} facet was investigated. The mechanistic studies revealed that •OH is mainly involved in the photocatalytic degradation of norfloxacin by {001} faceted TiO2/Ti film. In addition, norfloxacin degradation byproducts were investigated, on the basis of which degradation schemes were proposed.


Asunto(s)
Calor , Norfloxacino/química , Titanio/química , Catálisis , Estructura Molecular , Fotoquímica , Agua/química
3.
Heliyon ; 10(13): e33271, 2024 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-39055793

RESUMEN

Sol-gel method was used to prepare Sr1-xCdxZn2Fe4O11 (x = 0.00, 0.02, 0.06, 0.1) R-type hexaferrite. The synthesized materials were sintered at 850oC and desired phase was obtained. X-ray diffraction analysis confirms that R-type hexaferrite exists only as a single phase. Using the Scherer formula, crystallite size for all of the prepared samples was found to be in the range of 10.39-12.62 nm. Crystallite size (D), the lattice parameters (a, c), and the cell volume (Vcell), d-spacing, bulk density, X-ray density, porosity, dislocation density and micro strain were determined in structural analysis. Fourier transform infrared spectroscopy method was used to identify the metal-oxygen vibrations at different locations. FT-IR verifies the presence of the Fe-O stretching vibration band at 743 and 867 cm-1. The typical grain size in surface morphology investigation ranges from 0.56 to 0.82 µm. Dielectric response of ferrite ceramic samples replaced with Cd2+ was investigated in the frequency range of 1 MHz-3 GHz. The AC conductivity rises with an increase in frequency because they are proportional to one another. This increasing tendency is effectively described by the theory of Maxwell-Wagner and Koop. Q-values remain constant as frequency rises and behaves independently of frequency as long as frequency reaches 1.7 GHz. These types of materials are utilized in high-frequency applications including frequency filters and resonant circuits. All of the magnetic properties determined by analyzing the M - H loops, including saturation magnetization (Ms), retentivity (Mr), and coercivity (Hc), exhibit an increasing trend as the substitution of Cd2+ rises. Ms (49.76-56.38 emu/g), Mr (15.82-18.30 emu/g) and Hc range from 203.20 Oe to 215.80 Oe. Grain size decreases cause arise in coercivity, which is caused by an enhancement in magneto-crystalline anisotropy. Overall results suggest that Cd2+ replaced R-type hexagonal ferrites are a great resource for longitudinal recording media; they have the potential to be used in a wide variety of electronic applications, including resonant circuits and high-frequency filters, security, detecting and switching.

4.
RSC Adv ; 13(38): 26755-26765, 2023 Sep 04.
Artículo en Inglés | MEDLINE | ID: mdl-37681046

RESUMEN

Non-enzymatic glucose biosensors show high sensitivity, lower response time, wide linear range and low cost. Copper based composites show excellent electrocatalytic tunability and lead to a better charge transfer in electrochemical non-enzymatic glucose biosensors. In this work, a nanocomposite of polyvinylpyrrolidone (PVP) and copper selenide was synthesized by a facile one pot sol gel method. Synthesized nanomaterials were characterized by XRD, FTIR, UV-visible spectroscopy, SEM, EDS and XPS techniques. Electrochemical behavior was analyzed by cyclic voltammetry (CV), electrochemical impendence (EIS) and chronoamperometry techniques. XRD analysis revealed a hexagonal structure and crystalline nature of CuSe/PVP. FTIR spectra depicted C-N bonding at 1284 cm-1 and C[double bond, length as m-dash]O stretching at 1634 cm-1, which indicated the presence of PVP in the nanocomposite. Stretching at 823 cm-1 was attributed to the presence of copper selenide. UV-visible absorption indicated the bandgap of copper selenide/PVP at 2.7 eV. SEM analysis revealed a flake like morphology of CuSe/PVP. EDS and XPS analysis confirmed the presence of copper and selenium in the prepared nanocomposite. Prior to employing for biosensing applications, it is important to evaluate the antibacterial activity of nanomaterials for long term use in biological in vitro testing. These materials have shown an efficient inhibition zone of 26 mm against Gram negative Pseudomonas at 50 µg ml-1 and MIC value of 10 µg ml-1. Cyclic voltammetry shows that CuSe/PVP is a promising biosensor for monitoring glucose levels in a wide linear range of 0.5 mM to 3 mM at an excellent sensitivity of 13 450 µA mM-1 cm-2 with an LOD of 0.223 µM. Chronoamperometry measurements revealed a selective behavior of CuSe/PVP for glucose biosensing amongst ascorbic acid and dopamine as common interfering molecules. The nanocomposite was stable after 8 repeated cycles with 92% retention for glucose sensing capacity. This is attributed to the stable nature of the CuSe/PVP nanocomposite as well as higher surface area of available active sites. Herein the CuSe/PVP nanocomposite offered reasonable selectivity, high sensitivity wide linear range with very low LOD, as well as being abundant in nature, this Cu based biosensor has promising applications for future point of care tests (POCT).

5.
RSC Adv ; 13(21): 14461-14471, 2023 May 09.
Artículo en Inglés | MEDLINE | ID: mdl-37180010

RESUMEN

Semiconductor materials show a restricted degradation response to organic pollutants due to limited photocatalytic activity under visible light. Therefore, researchers have devoted much attention to novel and effective nanocomposite materials. For the first time, herein, a novel nano-sized semiconductor calcium ferrite modified by carbon quantum dots (CaFe2O4/CQDs) photocatalyst is fabricated via simple hydrothermal treatment for the degradation of aromatic dye using a visible light source. The crystalline nature, structure, morphology, and optical parameters of each of the synthesized materials were investigated using X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and UV-visible spectroscopy. The nanocomposite exhibits excellent photocatalytic performance (90% degradation) against Congo red (CR) dye. In addition, a mechanism for CaFe2O4/CQDs improving photocatalytic performance has been proposed. The CQDs in the CaFe2O4/CQD nanocomposite are considered to act as an electron pool and transporter, as well as a strong energy transfer material, during photocatalysis. CaFe2O4/CQDs appear to be a promising and cost-effective nanocomposite for dye-contaminated water purification, according to the findings of this study.

6.
J Food Sci Technol ; 48(6): 718-23, 2011 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-23572810

RESUMEN

Several types of whole pulses (green lentils, red lentils, yellow lentils, chickpeas, green peas, cowpeas and yellow peas) and grams (black grams, red grams and white grams) have been investigated for the identification of radiation treatment using microgel electrophoresis of single cells (DNA comet assay). Pulses and grams were exposed to the radiation doses of 0.5, 1.0 and 5 kGy covering the legalized commercial dose range for protection from insect/pest infestations. All irradiated samples showed comet like stretching of fragmented DNA toward anode, which is expected for irradiated samples. Unirradiated samples showed many intact cells/nuclei in form of round stains or with short faint tails, which is typical for unirradiated food samples. The study shows that DNA comet assay can be used as a rapid, inexpensive and highly effective screening test for the detection of radiation treatment of foods, like pulses and grams.

7.
J Hazard Mater ; 402: 123558, 2021 01 15.
Artículo en Inglés | MEDLINE | ID: mdl-32759000

RESUMEN

Sulfate radical-advanced oxidation processes (SR-AOPs) are emerging technologies for decomposing organic pollutants in water. This study investigated the efficiency of UV/persulfate (UV/S2O82-) process to degrade lindane in water, showing 93.2% lindane removal ([lindane]0 = 3.43 µM, [S2O82-]0 = 100 µM) at a UV fluence of 720 mJ/cm2. The lindane degradation followed first order kinetics and mechanistic studies suggested H-abstraction by SO4•- and Cl removal via C-Cl bond cleavage by UV-C light. Toxicity assessment using ECOSAR program showed toxicity gradually decreased and eventually no significant toxicity remained when all by-products vanished at high UV dose. Removal efficiency of lindane decreased from 93.2% to 38.4, 45.5, 56.0, 84.3 and 88.6%, by adding 1.0 mg/L humic acid or 1.0 mM CO32-, HCO3-, Cl- or SO42-, respectively. Coupling of H2O2 with UV/S2O82- showed a significant synergistic effect with 99.0% lindane removal at a UV fluence of 600 mJ/cm2, using [S2O82-]0 = [H2O2]0 = 50 µM while UV/H2O2 resulted in only 36.6% lindane removal ([lindane]0 = 3.43 µM, [H2O2]0 = 100 µM) at a UV fluence of 720 mJ/cm2. The results indicate that SR-AOP has potential for consideration as a remedial technology to treat persistent chlorinated pesticides such as lindane in contaminated water.

8.
J Hazard Mater ; 357: 506-514, 2018 09 05.
Artículo en Inglés | MEDLINE | ID: mdl-30008383

RESUMEN

The removal of brilliant green (BG), a toxic organic and cationic dye, has been examined by UV/S2O82- (PS), UV/HSO5- (PMS) and UV/H2O2 processes. BG showed insignificant direct photolysis at 254 nm (i.e., 8.6% after 30 min). However, enhanced BG degradation was observed in UV/PS, UV/PMS and UV/H2O2 systems as revealed from 63.1, 47.0 and 34.8% BG degradation, respectively, at 30 min of reaction time, using 0.05 mM BG and 1.0 mM oxidant initial concentration. The bimolecular rate constants of OH and SO4- with BG were determined to be 2.35 × 109 and 2.21 × 109 M-1 s-1, respectively. Electrical energy per order (EE/O) values for UV/PS, UV/PMS and UV/H2O2 processes were calculated to be 5.4, 6.8, and 7.8 KWh/m3/order, respectively. The addition of humic acid (HA) and inorganic anions inhibited the degradation of BG by UV/PS in the order of NO2- > HA > HCO3- > Cl-  > NO3- ≈ SO42-. The results of frontier electron densities (FEDs) showed that C-atom holding the three rings (C7), and C-atoms at para positions to N-alkyl groups of the two rings (C4 and C14) are the predominant sites for radical addition. Furthermore, nine degradation products (DPs) of BG were detected experimentally using LC/MS/MS.

9.
Environ Technol ; 37(5): 590-602, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-26208491

RESUMEN

Gamma-radiation-induced degradation of ciprofloxacin (CIP) in aqueous solution and the factors affecting the degradation process have been investigated. The results showed that CIP (4.6 mg/L) was almost completely degraded at an absorbed dose of 870 Gy. The kinetic studies of aqueous solutions containing 4.6, 10, 15 and 17.9 mg/L indicated that the decomposition of CIP by gamma irradiation followed pseudo-first-order kinetics and the decay constant (k) decreased from 5.9 × 10(-3) to 1.6 × 10(-3) Gy(-1) with an increase in CIP initial concentration from 4.6 to 17.9 mg/L. The effect of saturation of CIP solution with N2, N2O or air on radiation-induced degradation of CIP was also investigated. The effects of radical scavengers, such as t-BuOH and i-PrOH, showed the role of reactive radicals towards degradation of CIP in the order of OH > e(aq)- . H. The apparent second-order rate constant of [Formula: see text] with CIP was calculated to be 2.64 × 10(9) M(-1) s(-1). The effects of solution pH as well as natural water contaminants, such as [HCO3-, CO3(2-), and NO2-, on CIP degradation by gamma-irradiation were also investigated. Major degradation products, including organic acids, were identified using UPLC-MS/MS and IC, and degradation pathways have been proposed.


Asunto(s)
Antibacterianos/química , Ciprofloxacina/química , Contaminantes Químicos del Agua/química , Antibacterianos/efectos de la radiación , Ciprofloxacina/efectos de la radiación , Rayos gamma , Oxidación-Reducción , Contaminantes Químicos del Agua/efectos de la radiación
10.
Environ Sci Pollut Res Int ; 23(12): 12362-71, 2016 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-26979317

RESUMEN

The present study elaborates the removal of endosulfan, an emerging water pollutant and potential carcinogenic, in aerated solution. The influence of Cl(-), NO3 (-), NO2 (-), CO3 (2-), HCO3 (-), SO3 (2-), and humic acid was assessed on the radiolytic degradation of endosulfan. A strong inhibition on the radiolytic degradation of endosulfan was observed in the presence of NO3 (-), NO2 (-), and SO3 (2-). Instead, a slight increase in the removal efficiency of endosulfan was observed at high concentrations of CO3 (2-) and HCO3 (-). The formation of CO3 (•-) in radiolytic degradation of endosulfan in the presence of CO3 (2-) and HCO3 (-) was demonstrated by adding SO3 (2-) that rapidly react with CO3 (•-). The results indicate that CO3 (•-) formed from the reactions of CO3 (2-) and HCO3 (-) and commonly found in natural water can play an important role in the degradation of endosulfan and other sulfur containing electron-rich compounds. The study showed faster degradation of endosulfan at lower concentration compared to high concentration and removal was found to follow pseudo-first-order kinetic. Endosulfan ether was found as the main degradation product and degradation pathway was found to be initiated at the S=O bond of endosulfan. The efficiency of gamma irradiation in the removal of endosulfan was examined in terms of formation of short chain organic acids and chloride ion accumulation.


Asunto(s)
Carbonatos/química , Endosulfano/análisis , Endosulfano/análogos & derivados , Endosulfano/química , Rayos gamma , Cinética , Soluciones , Agua/química , Contaminantes Químicos del Agua/análisis
11.
Environ Sci Pollut Res Int ; 23(13): 13155-68, 2016 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-27020780

RESUMEN

This study reports the efficiency of gamma-ray irradiation to degrade quinolone antibiotic, norfloxacin, in aqueous solution. Laboratory batch experiments were conducted to determine the "pseudo-first" order degradation kinetics of norfloxacin in the concentration ranges of 3.4-16.1 mg L(-1) by gamma-ray irradiation. The dose constant was found to be dependent on the initial concentration of norfloxacin and gamma-ray irradiation dose rate (D r). The saturation of norfloxacin sample solutions with N2, air or N2O, and the presence of tert-butanol and 2-propanol showed that (•)OH played more crucial role in the degradation of norfloxacin. The second order rate constants of (•)OH, eaq (-), and (•)H with norfloxacin were calculated to be 8.81 × 10(9), 9.54 × 10(8), and 1.10 × 10(9) M(-1) s(-1), respectively. The effects of various additives including CO3 (2-), HCO3 (-), NO3 (-), NO2 (-), and thiourea and the pH of the medium on the degradation of norfloxacin were also investigated. Norfloxacin degradation was lower in surface water and wastewater than in ultrapure water. Several degradation byproducts of norfloxacin were identified from which the possible degradation pathway was proposed.


Asunto(s)
Norfloxacino/efectos de la radiación , Contaminantes Químicos del Agua/efectos de la radiación , 2-Propanol , Antibacterianos , Rayos gamma , Cinética , Oxidación-Reducción , Aguas Residuales , Agua , Purificación del Agua , Calidad del Agua
12.
Water Res ; 39(10): 2085-95, 2005 May.
Artículo en Inglés | MEDLINE | ID: mdl-15949529

RESUMEN

The destruction of methyl tert-butylether (MTBE) in water in the presence of chloroform has been studied using 60Co gamma irradiation. Distilled water solutions at three different concentrations of the individual solutes MTBE and CHCl3 were irradiated for various times to provide dose destruction information. Then, the irradiation of a mixture of MTBE (at two different concentrations) and CHCl3 (at one concentration) was conducted. A kinetic model was used incorporating recently determined bimolecular rate constants to describe the destruction of the MTBE and CHCl3 individually and in mixtures. These studies were conducted in distilled water simplifying the radiation chemistry significantly. With the improvements in the modelling capability, we are closer to being able to use the model to study "real-world" mixtures in natural waters.


Asunto(s)
Cloroformo/química , Rayos gamma , Éteres Metílicos/metabolismo , Contaminantes Químicos del Agua/metabolismo , Purificación del Agua/métodos , Radioisótopos de Cobalto , Relación Dosis-Respuesta en la Radiación , Cinética , Modelos Químicos
13.
J Hazard Mater ; 288: 147-57, 2015 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-25725267

RESUMEN

The degradation of atrazine was investigated in aqueous solution by gamma-ray irradiation. 8.11 µM initial atrazine concentration could be completely removed in N2 saturated solution by applying 3500 Gy radiation dose at a dose rate of 296 Gy h(-1). Significant removal of atrazine (i.e., 39.4%) was observed at an absorbed dose of 1184 Gy in air saturated solution and the removal efficiency was promoted to 50.5 and 65.4% in the presence of N2O and N2 gases, respectively. The relative contributions of hydrated electron, hydroxyl radical and hydrogen radical toward atrazine degradation were determined as ratio of observed dose constant (kobs) and found to be 5: 3: 1 for keaq(-): k·OH: kH·, respectively. The degradation efficiency of atrazine was 69.5, 55.6 and 37.3% at pH 12.1, 1.7 and 5.7, respectively. A degradation mechanism was proposed based on the identified degradation by-products by gas chromatography-mass spectrometry. Taking the relative contributions of oxidative and reductive species to atrazine degradation into account, reductive pathway proved to be a better approach for the radiolytic treatment of atrazine contaminated water.


Asunto(s)
Atrazina/química , Atrazina/efectos de la radiación , Herbicidas/química , Herbicidas/efectos de la radiación , Radical Hidroxilo/química , Protones , Cromatografía de Gases y Espectrometría de Masas , Concentración de Iones de Hidrógeno , Cinética , Eliminación de Residuos Líquidos , Contaminantes Químicos del Agua , Purificación del Agua , Rayos X
14.
Chemosphere ; 121: 18-25, 2015 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-25466821

RESUMEN

The gamma irradiation was investigated for potential removal of endosulfan sulfate, an emerging water pollutant and central nervous system disruptor. A removal efficiency of 99.5% of initially 1.30 µM endosulfan sulfate was observed at an absorbed dose of 1020 Gy. Aqueous electron (eaq(-)) was found to play primary role in the removal of endosulfan sulfate which was possibly due to greater reactivity of eaq(-) with endosulfan sulfate, considering the second-order rate constant of 8.1×10(9) and 3.4×10(10) M(-1) s(-1) for hydroxyl radical (·OH) and eaq(-), respectively, with endosulfan sulfate. The removal efficiency of endosulfan sulfate was affected by the pH of aqueous solution, with observed removal efficiency of 99.5%, 98.3% and 31.3% at pH 6.2, pH 10.0, and pH 2.6, respectively. The efficiency was also influenced by inorganic anions and humic acid in the order of nitrate>nitrite>bicarbonate>carbonate ≃ humic acid. The initial degradation rate increased while degradation constant decreased with increasing initial concentrations of endosulfan sulfate. The degradation pathways showed that oxidative pathway was initiated at the SO2 bond while reductive pathways at the chlorine attached to the ring of endosulfan sulfate. The mass balance showed removal of 98% chloride and 72% sulfate ions from endosulfan sulfate at an absorbed dose of 1020 Gy. The removal of endosulfan sulfate followed by subsequent loss of by-products under extended treatment showed that gamma irradiation is potential technique for the remediation of organic pollutants from a water environment.


Asunto(s)
Endosulfano/análogos & derivados , Rayos gamma , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Aniones , Endosulfano/análisis , Endosulfano/efectos de la radiación , Sustancias Húmicas/análisis , Radical Hidroxilo/química , Cinética , Oxidación-Reducción , Contaminantes Químicos del Agua/efectos de la radiación
15.
J Hazard Mater ; 278: 40-8, 2014 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-24952221

RESUMEN

The removal of endosulfan, an emerging water pollutant, from water was investigated using gamma irradiation based advanced oxidation and reduction processes (AORPs). A significant removal, 97% of initially 1.0 µM endosulfan was achieved at an absorbed dose of 1020 Gy. The removal of endosulfan by gamma-rays irradiation was influenced by an absorbed dose and significantly increased in the presence of aqueous electron (eaq(-)). However, efficiency of the process was inhibited in the presence of eaq(-) scavengers, such as N2O, NO3(-), acid, and Fe(3+). The observed dose constant decreased while radiation yield (G-value) increased with increasing initial concentrations of the target contaminant and decreasing dose-rate. The removal efficiency of endosulfan II was lower than endosulfan I. The degradation mechanism of endosulfan by the AORPs was proposed showing that reductive pathways involving eaq(-) started at the chlorine attached to the ring while oxidative pathway was initiated due to attack of hydroxyl radical at the SO bond. The mass balance showed 95% loss of chloride from endosulfan at an absorbed dose of 1020 Gy. The formation of chloride and acetate suggest that gamma irradiation based AORPs are potential methods for the removal of endosulfan and its by-products from contaminated water.


Asunto(s)
Endosulfano/efectos de la radiación , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/efectos de la radiación , Acetatos/química , Cloruros/química , Electrones , Endosulfano/química , Rayos gamma , Radical Hidroxilo/química , Oxidación-Reducción , Soluciones , Contaminantes Químicos del Agua/química
16.
Chemosphere ; 93(4): 645-51, 2013 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-23886443

RESUMEN

Chlorpyrifos is an organophosphate pesticide and is significant because of its extensive use, persistence in the environment, wide distribution, and its toxicity may lead to lung and central nervous system damage, developmental and autoimmune disorders and vomiting. In the present study, the irradiation of chlorpyrifos in aqueous solution by (60)Co γ-rays was conducted on a laboratory scale and the removal efficiency of chlorpyrifos was investigated. The SPME-GC-ECD method was used for analysis of chlorpyrifos. Aqueous solutions of different concentrations of target compound (200-1000 µg L(-1)) were irradiated through 30-575 Gy. Gamma irradiation showed 100% degradation for a 500 µg L(-1) solution at an absorbed dose of 575 Gy (the dose rate was 300 Gy h(-1)). The radiolysis of chlorpyrifos was pseudo-first order (decay) with respect to dose. The dose constants determined in this study ranged from 8.2×10(-3) to 2.6×10(-2) Gy(-1), and decreased with an increase in the initial concentration of chlorpyrifos, while the radiation chemical yield (G-value) for the loss of chlorpyrifos was found to decrease with increasing absorbed dose. The effect of saturated solutions of N2 and N2O, and radical scavengers tert-butanol, iso-propanol, H2O2, NaNO3 and NaNO2 on the degradation of chlorpyrifos were also studied. The results showed that the oxidative OH was the most important in the degradation of chlorpyrifos, while the reductive radicals, aqueous electron and H, were of less importance for the degradation of chlorpyrifos. The inorganic by-products Cl(-), SO4(2-) and PO4(3-) were quantitatively determined by IC.


Asunto(s)
Cloropirifos/química , Insecticidas/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Rayos gamma , Oxidación-Reducción , Eliminación de Residuos Líquidos/métodos
17.
J Hazard Mater ; 263 Pt 2: 584-92, 2013 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-24231332

RESUMEN

This study explored the efficiency of UV-C-based advanced oxidation processes (AOPs), i.e., UV/S2O8(2-), UV/HSO5(-), and UV/H2O2 for the degradation of endosulfan, an organochlorine insecticide and an emerging water pollutant. A significant removal, 91%, 86%, and 64%, of endosulfan, at an initial concentration of 2.45 µM and UV fluence of 480 mJ/cm(2), was achieved by UV/S2O8(2-), UV/HSO5(-), and UV/H2O2 processes, respectively, at a [peroxide]0/[endosulfan]0 molar ratio of 20. The efficiency of these processes was, however, inhibited in the presence of radical scavengers, such as alcohols (e.g., tertiary butyl alcohol and isopropyl alcohol) and natural organic matter (NOM). The inhibition was also influenced by common inorganic anions in the order of nitrite > bicarbonate > chloride > nitrate ≈ sulfate. The observed pseudo-first-order rate constant decreased while the degradation rate increased with increasing initial concentration of the target contaminant. The degradation mechanism of endosulfan by the AOPs was evaluated revealing the main by-product as endosulfan ether. Results of this study suggest that UV-C-based AOPs are potential methods for the removal of pesticides, such as endosulfan and its by-products, from contaminated water.


Asunto(s)
Endosulfano/análisis , Peróxido de Hidrógeno/química , Peróxidos/química , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodos , Alcoholes/química , Aniones , Relación Dosis-Respuesta a Droga , Relación Dosis-Respuesta en la Radiación , Endosulfano/análogos & derivados , Endosulfano/química , Depuradores de Radicales Libres , Cromatografía de Gases y Espectrometría de Masas , Radical Hidroxilo , Cinética , Modelos Químicos , Compuestos Orgánicos , Oxígeno/química , Plaguicidas/química , Fotólisis , Sulfatos/química , Rayos Ultravioleta
18.
Isotopes Environ Health Stud ; 48(2): 295-301, 2012 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-22397699

RESUMEN

The analysis of gamma-emitting radionuclides in nature, i.e. (226)Ra, (232)Th, (40)K and (137)Cs, has been carried out in soil samples collected from Peshawar University Campus and surrounding areas using a high purity germanium detector coupled with a computer-based high-resolution multichannel analyser. The activity concentrations in soil ranged from 30.20±0.65 to 61.90±0.95, 50.10±0.54 to 102.80±1.04, 373.60±4.56 to 1082±11.38 and 9.50±0.11 to 46.60±0.42 Bq kg(-1) for (226)Ra, (232)Th, (40)K and (137)Cs, with a mean value of 45±7.70, 67±12.50, 878±180 and 19±9.20 Bq kg(-1), respectively. The radium equivalent activity, internal and external hazard indices have mean values of 203.40±29.40 Bq kg(-1), 0.56 and 0.68, respectively. The mean values of outdoor and indoor absorbed dose rates in air and the annual effective dose equivalents were found to be 106.50 and 128 nGy h(-1) and 0.19 and 0.54 mSv y(-1), respectively. In the present study, (40)K was the major radionuclide present in soil samples. The presence of (137)Cs indicates that this area also received some fallout from the nuclear accident of the Chernobyl power plant in 1986. The activity concentrations of radionuclides found in soil samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the public.


Asunto(s)
Radiación de Fondo , Monitoreo de Radiación/métodos , Radioisótopos/análisis , Contaminantes Radiactivos del Suelo/análisis , Pakistán , Dosis de Radiación , Radiactividad , Espectrometría gamma
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