[Show abstract][Hide abstract] ABSTRACT: The aim of this paper was the development and optimization of an electrochemical method for the degradation of two triketone herbicides, mesotrione and sulcotrione, in a two-electrode undivided electrochemical cell equipped with commercially available, non-modified, electrode materials. The electrochemical parameters studied included five different electrode systems (Zr/Pt, Pd/Pt, C/Pt, Nb/Pt and Ti/Pt), current densities (27.66, 55.33, …, 110.66 mA·cm-2) and pH values (3, 7 and 9) in 0.05 M sodium sulfate as supporting electrolyte. The electrical energy consumption and chemical oxygen demand were calculated for optimal conditions. The degradation efficiency was determined by high performance liquid chromatography equipped with a diode array detector, while the degradation products for both pesticides were identified and compared by UHPLC-mass spectrometry. The results could lead to an accurate estimate of their effect on the environment. A real water sample was used to study the influence of organic matter on pesticide degradation. Based on the results obtained the electrochemical treatment could be used for the successful removal of triketone herbicides from contaminated water.
CLEAN - Soil Air Water 12/2014; · 1.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper reports the results of a study focused on the presence and bioavailability of arsenic in agricultural soil in the mining and industrial regions of northern Kosovo and southern Serbia, as well as uptake and bioaccumulation of arsenic in two commonly cultivated plant species (Zea mays L. and Solanum tuberosum L.). This area was one of the most important mining districts in Europe. The collected soil samples were subjected to a modified BCR three-step sequential extraction procedure in order to investigate the chemical partitioning of arsenic in the soils. The general distribution of arsenic in various fractions was: exchangeable < reducible < oxidizable fractions. Highest concentrations of total arsenic in soil were found close to industrial facilities and tailing ponds. In addition, fluvisols were significantly more enriched with arsenic than soils at a distance from the river flows. The edible parts of the plant specimen showed different As contents, suggesting that these plant species have different propensities for the uptake and bioaccumulation of arsenic from soil.
Soil and Sediment Contamination 12/2014; · 0.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We studied the effect of liming and P fertilization of extremely acid soil (accidently acidified by sulfidic mining waste) on P availability and the subsequent adaptive responses of wheat roots. The wheat plants were grown in rhizoboxes allowing precise sampling of rhizosphere and bulk soil for sequential extraction of P fractions and determination of exchangeable Al. Root exudates were collected by pieces of paper for electrophoresis and subjected to HPLC analysis. Expression of organic anions and Pi transporter genes was analyzed by a real-time quantitative PCR. The concomitant application of lime with P fertilization increased the concentrations of plant-available P fractions in both rhizosphere and bulk compartments. The applied soil amendments strongly affected plant growth, biomass partitioning and shoot P accumulation. Liming enhanced root exudation of citrate in P unfertilized plants, while the high malate efflux was maintained until both P deficiency and Al toxicity were eliminated by the amendments. We showed the importance of liming for recovering of P acquisition potential of wheat roots, which can be strongly impaired in acid soils. Our results clearly demonstrated that P-deficient roots not subjected to Al stress in the limed soil can maintain high efflux of malate and even increase efflux of citrate along with the enhanced expression of related anion transporters (TaMATE1 and TaALMT1).
Biology and Fertility of Soils 10/2014; · 3.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Elevated concentrations of arsenic in groundwater, which is used as a source for drinking water, is a worldwide problem. Use of TiO2 and iron doped TiO2 synthesized by a microwave-assisted hydrothermal method for As(III) and As(V) removal were examined. Synthesized sorbents were characterized with XRD and nitrogen physisorption. Synthesized sorbents have predominantly anatase structure, and no peaks for iron could be observed. Doping of iron increases the surface area of synthesized sorbents. Sorption experiments show that increase of iron in sorbents increases the sorption capacity for As(III) and As(V). Increase of pH from 3 to 11 has no influence on As(III) sorption but decreases the sorption of As(V). Batch isotherm studies were performed to determine the binding capacities of As(III) and As(V). As(III) followed the Freundlich isotherm model, while for As(V) a better fit was with the Langmuir isotherm. The results of competition of SO42– and PO43– anions on adsorption of As(III) indicated that both anions reduced substantially the efficiency of adsorption on both adsorbents while for As(V) only the presence of PO43– anion interfered with adsorption. Testing 10Fe/TiO2 sorbent with arsenic contaminated natural water showed that this material could be used for removal of arsenic to the level recommended by WHO without pretreatment.
[Show abstract][Hide abstract] ABSTRACT: This paper describes the preparation of a new sensor based on Zn-ferrite modified glassy carbon paste electrode and its electrochemical application for the determination of trace Cd(II) ions in waste waters using differential pulse anodic stripping voltammetry (DPASV). Different Zn/Ni ferrite nanoparticles were synthesized and characterized using scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). The prepared ferrite nanoparticles were used for the preparation of Zn-ferrite-modified glassy carbon paste electrode (ZnMGCPE) for determination of Cd(II) at nanomolar levels in waste water at pH 5. The different parameters such as conditions of preparation, Zn2+/Ni2+/Fe2+ ratio and electrochemical parameters, percentage of modifier, accumulation time, pH and accumulation potential were investigated. Besides, interference measurements were also evaluated under optimized parameters. The best voltammetric response was observed for ZnFe2O4 modifier, when the percentage of modifier was 3 %, accumulation time 9 min, pH of supporting electrolyte 5 and accumulation potential −1.05 V. Thus prepared electrode displays excellent response to Cd(II) with a detection limit of 0.38 ppb, and selective detection toward Cd(II) was achieved.
[Show abstract][Hide abstract] ABSTRACT: Microwave-hydrothermal method was used for synthesis of TiO2 and TiO2 doped with zirconium. Method was fast and simple and adsorbents were used for removal of As(III) and As(V) from aqueous solutions. The adsorbents were characterized by BET surface area measurements and powder XRD. Experiments showed that TiO2 doped with 10% of Zr using microwave-hydrothermal method have greater specific surface area and total pore volume in comparison with TiO2 synthetized with the same method. Better removal with doped adsorbent was obtained for both, As(III) and As(V). Further experiments were carried out with Zr doped TiO2 sorbent in order to examine kinetic of adsorption, influence of pH and effect of common anions present in natural waters.
Journal of Saudi Chemical Society 06/2014; · 1.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An electrochemiluminescent (ECL) swimmer driven by bipolar electrochemistry is reported for enzymatic glucose sensing. The chemo-mechanical motion is induced by localized hydrogen bubble generation. The concomitant oxidation of the luminophore and of the enzymatically-produced NADH leads to ECL emission with a direct glucose-dependent light intensity. We demonstrate herein the local sensing and reporting of glucose in a concentration gradient explored by the ECL swimmer. Such a dynamic sensing approach combines in a synergetic way the wireless propulsion with the enzymatic selectivity using ECL as a readout method at the level of moving objects.
Chemical Communications 06/2014; · 6.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study is to investigate the significance of breast milk and infant formula in the prevention of oxidative stress, by electrochemical determination of the total antioxidant potential, demonstrating the relationship between the antioxidant capacity of milk and postnatal age. Human breast milk, commercial UHT milk, and infant formulas supplemented with prebiotics were used. Samples were diluted in phosphate buffer solution, and the total antioxidant activity was potentiometrically measured by the iodine/iodide redox couple with the Pt Fisher electrode as a working electrode and saturated calomel as a reference electrode. Cyclic voltammograms and differential pulse voltammograms were recorded with the glassy carbon electrode as the working electrode, an accessory platinum electrode, and an Ag/AgCl reference electrode. The potentiometric measurement indicates that human breast milk has the highest redox potential, while the commercial UHT milk has very low potential. Infant formulas also have high potential. The main advantage of electrochemical methods used to assess the total antioxidant activity of milk was that they directly monitored the electron-donating ability of the compounds and could be used for the quantitative analysis of the total antioxidants of different types of milk.
[Show abstract][Hide abstract] ABSTRACT: In power plant, coal ash obtained by combustion is mixed with river water and transported to the dump. Sequential extraction was used in order to assess pollution caused by leaching of elements during ash transport through the pipeline and in the storage (cassettes). A total of 80 samples of filter ash as well as the ash from active (currently filled) and passive (previously filled) cassettes were studied. Samples were extracted with distilled water, ammonium acetate, ammonium oxalate/oxalic acid, acidic solution of hydrogen-peroxide, and a hydrochloric acid. Concentrations of the several elements (Al, As, Cd, Co, Cu, Cr, Fe, Ba, Ca, Mg, Ni, Pb, and Zn) in all extracts were determined by inductively coupled plasma atomic emission spectrometry. Pattern recognition method was carried out in order to provide better understanding of the nature of distribution of elements according to their origins. Results indicate possible leaching of As, Ca, Cd, Cu, Zn, and Pb. Among these elements As, Cd, and Pb are toxicologically the most important but they were not present in the first two phases with the exception of As. The leaching could be destructive and cause negative effects on plants, water pollution, and damage to some life forms.
[Show abstract][Hide abstract] ABSTRACT: Fe-doped TiO 2 photocatalysts with different contents of Fe (0.5, 1.6, 3.4 and 6.4 %) were synthesized by a microwave-hydrothermal method and characterized by X-ray diffraction analysis, N 2 physisorption at 77 K and UV– –Vis spectrometry. The characterization showed that the Fe ions were highly dispersed in the TiO 2 lattice. It was found that all the synthesized catalysts had a mesoporous structure and that Fe-doping increased the BET surface area. The UV–Vis study showed that the absorption spectra were shifted to longer wave-lengths (red shift) with increasing dopant concentration. The photocatalytic activity of the samples was evaluated by the decolorization of the textile dye Reactive Blue 52 (RB) in aqueous solutions under sun-like radiation in the presence of H 2 O 2 (a heterogeneous photo-Fenton process). The photocatalyst with 3.4 % Fe was found to be the most efficient in the presence of H 2 O 2 . The effect of the initial pH of the dye solution was assessed and dissolution of iron ions was studied as a function of pH value. It was concluded that decolori-zation was more favorable in acidic pH, and that at pH values >4, the release of Fe ions into the solution was negligible. Photocatalytic degradation of 4-chlorophenol (4-CP) was investigated under the optimal conditions and it was shown that the catalyst was capable of degrading colorless pollutants.
Journal of the Serbian Chemical Society 11/2013; 79021:977-991. · 0.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Degradation of two triketone herbicides, mesotrione and sulcotrione, was studied using four different advanced oxidation processes (AOPs): ozonization, dielectric barrier discharge (DBD reactor), photocatalysis and Fenton reagent, in order to find differences in mechanism of degradation. Degradation products were identified by high performance liquid chromatography (HPLC-DAD) and UHPLC-Orbitrap-MS analyses. A simple mechanism of degradation for different AOP was proposed. Thirteen products were identified during all degradations for both pesticides. It was assumed that the oxidation mechanisms in the all four technologies were not based only on the production and use of the hydroxyl radical, but they also included other kinds of oxidation mechanisms specific for each technology. Similarity was observed between degradation mechanism of ozonation and DBD. The greatest difference in the products was found in Fenton degradation which included the opening of benzene ring. When degraded with same AOP pesticides gave at the end of treatment the same products. Global toxicity and COD value of samples was determined after all degradations. Real water sample was used to study influence of organic matter on pesticide degradation. These results could lead to accurate estimates of the overall effects of triketone herbicides on environmental ecosystems and also contributed to the development of improved removal processes.
Journal of hazardous materials 07/2013; 260C:1092-1099. · 4.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The concentrations of iron, lead, cadmium, copper, manganese, mercury and arsenic were measured in water, sediment, five macrophytes (Typha angustifolia, Iris pseudacorus, Polygonum amphybium, Myriophyllum spicatum and Lemna gibba) and five fish species (Sander lucioperca, Abramis brama, Carassius gibelio, Silurus glanis and Arystichtys nobilis) in the Gruža Reservoir, used for water supply and recreational fishing. The concentrations of all examined elements were higher in sediment than in water. The values of the ratio between element concentrations in the sediment and those in the water were the highest for Fe and As. Among the five plant species, the highest concentrations of Pb and Mn were observed in T. angustifolia, while the highest concentrations of Fe, Cu and Hg were in L. gibba. I. pseudacorus and P. amphybium had the highest concentrations of Cd and As, respectively. Among the fish species, C. gibelio showed the highest tendency of element accumulation (Fe, Cd, Cu), followed by S. lucioperca (Pb, Hg), A. brama (Mn) and A. nobilis (As). The average concentrations of elements in fish muscle, except for As in A. nobilis (2.635 ± 0.241 mg kg(-1) ww), were below the limits that are considered safe for human consumption in accordance with the European Commission Regulation and Official Gazette of Serbia.
Bulletin of Environmental Contamination and Toxicology 02/2013; · 1.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ellagic acid is a biologically active polyphenol found in numerous fruits and vegetables. However, not many papers dealing with the electrochemical properties and protolytic equilibria of ellagic acid have been published so far. The electro-oxidation mechanism of ellagic acid was studied in methanol aqueous media (1:1, v/v) within the pH range of 1.5–9.0, t = 25 ± 1 °C, using cyclic voltammetry on a glassy carbon electrode, and by semiempirical calculations. Results show that oxidation of ellagic acid is a pH-dependent, two-step quasireversible process. The slope of peak 1 indicates the exchange of the same number of electrons and protons within the whole studied pH range; the slope of peak 2 changes with the increase of pH, and three different regions are visible. As protolytic equilibria studies revealed that ellagic acid acts as a diprotic acid in the studied conditions (acidity constants were potentiometrically determined as pK a1 = 5.42 ± 0.01 and pK a2 = 6.76 ± 0.01), it is obvious that the electro-oxidation occurs at the hydroxyl group subjected to dissociation. The three different regions are therefore recognized as regions with different dominating species: unionized molecule (H4A), monoanion (H3A−), and dianion (H2A2−). UV/Vis spectral changes confirmed the proposed equilibria. Heat of formation and electron densities calculated at semiempirical level were used to propose the hydrogen and electron abstraction sites. According to the obtained results, a new mechanism of ellagic acid electro-oxidation is proposed.
[Show abstract][Hide abstract] ABSTRACT: The complexation reactions between octaazamacrocyclic ligand N,N′,N″,N′″-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc) and Co2+, Ni2+, Zn2+ and Cu2+ metal cations have been studied conductometrically in acetonitrile and aqueous solutions. The conductance data exhibit different stoichiometry of the complexes in two studied solutions. In most cases 1:1 (ML) complexes were formed while in some cases 2:1 (M2L) complexes are evident. The stability constants of the resulting 1:1 complexes were determined by computer fitting of the conductance/mole ratio data. Theoretical DFT calculations were used to explain metal binding capability of tpmc ligand and the binding sequences were found to follow the order: Cu2+ ≫ Ni2+ > Co2+ > Zn2+. The combination of results obtained by this theoretical approach and conductometric study successfully explains sensitivity and selectivity of recently developed tpmc based ISE and could play a guiding role in planning experiments with large macrocyclic ligands.
[Show abstract][Hide abstract] ABSTRACT: Efficiency of Fe2O3 and mixture of Fe2O3 and MnO2 nanoparticles synthesised by mechanical–chemical reaction for inorganic As(III) and As(V) sorption was examined. Sorbents (Fe2O3 and mixture Fe2O3:MnO2 = 3:1) synthesised by mechanical–chemical treatment in planetary ball mile with different milling times were tested by batch experiments. Experimental data were fitted both to Freundlich and Langmuir adsorption models. Efficiency of sorption was in good correlation with the time of milling in case of pure oxide. There were small differences in sorption between As(III) and As(V). In the case of mixture of oxides results were different. The best results were obtained by 30 min of milling. With prolonged milling, the sorption decreased to 3 h and after that increased again. These results were explained by phase transition. Sorption kinetics, influence of pH and the presence of other anions were examined for mixture of oxides with highest sorption capacity. The bioavailability of sorbed arsen was tested using modified Tessier procedure.
[Show abstract][Hide abstract] ABSTRACT: Textile industries are widespread in developing countries. Among the various processes in the textile industry, the dyeing process uses large volumes of water for dyeing, fixing and washing. Textile industry wastewater is characterized by intensive color and high chemical oxygen demand (COD) concentrations that discarding of these toxic wastewaters to the environment will cause a major problem. In this study electrochemical oxidation of reactive textile dyes: Reactive Blue 52, Reactive Black 5, Reactive Green 15, and Reactive Yellow 125, using platinum anode was examined. Electrolysis is carried out in electrochemical cell containing membrane which is standard membrane in industry. Membrane separated anodic and cathodic area. Supporting electrolyte was 0.1M sodium sulfate which is also present in real textile effluents. Applied voltage of 6, 12 and 24V, and influence of membrane on electrolysis were examined on model dye (Reactive Blue 52). Highest degradation degree for model dye was achieved at 12V, so electrolysis of other dyes was done on this voltage. COD value of all dyes dropped after 60 minutes of electrolysis below a measurable level (<30mg/L O 2), except Reactive Black 5 whose COD reduction was 57.95% with membrane and 35.28% without membrane applied. Complete decolorization was achieved after 10 to 60 minutes for all dyes. Degradation products of model dye Reactive Blue 52 were monitored with HPLC, and influence of pH on decolorization was also examined on model dye.
International journal of electrochemical science 01/2013; 8(1):168-183. · 1.96 Impact Factor