Goran Roglić

Decolorization of reactive textile dyes using water falling film dielectric barrier discharge

Decolorization of reactive textile dyes Reactive Black 5, Reactive Blue 52, Reactive Yellow 125 and Reactive Green 15 was studied using advanced oxidation processes (AOPs) in a non-thermal plasma reactor, based on coaxial water falling film dielectric barrier discharge (DBD). Used initial dye concentrations in the solution were 40.0 and 80.0mg/L. The effects of different initial pH of dye solutions, and addition of homogeneous catalysts (H(2)O(2), Fe(2+) and Cu(2+)) on the decolorization during subsequent recirculation of dye solution through the DBD reactor, i.e. applied energy density (45-315kJ/L) were studied. Influence of residence time was investigated over a period of 24h. Change of pH values and effect of pH adjustments of dye solution after each recirculation on the decolorization was also tested. It was found that the initial pH of dye solutions and pH adjustments of dye solution after each recirculation did not influence the decolorization. The most effective decolorization of 97% was obtained with addition of 10mM H(2)O(2) in a system of 80.0mg/L Reactive Black 5 with applied energy density of 45kJ/L, after residence time of 24h from plasma treatment. Toxicity was evaluated using the brine shrimp Artemia salina as a test organism.

Degradation of triketone herbicides, mesotrione and sulcotrione, using advanced oxidation processes

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.

New evidence for TiO2 uniform surfaces leading to complete bacterial reduction in the dark: Critical issues

This study presents new evidence for the events leading to Escherichia coli reduction in the absence of light irradiation on TiO2-polyester (from now on TiO2-PES. By transmission electron microscopy (TEM) the diffusion of TiO2 NPs aggregates with the E. coli outer lipo-polyssacharide (LPS) layer is shown to be a prerequisite for the loss of bacterial cultivability. Within 30 min in the dark the TiO2 aggregates interact with E. coli cell wall leading within 120 min to the complete loss of bacterial cultivability on a TiO2-PES 5% TiO2 sample. The bacterial reduction was observed to increase with a higher TiO2 loading on the PES up to 5%. Bacterial disinfection on TiO2-PES in the dark was slower compared to the runs under low intensity simulated sunlight light irradiation. The interaction between the TiO2 aggregates and the E. coli cell wall is discussed in terms of the competition between the TiO2 units collapsing to form TiO2-aggregates at a physiologic pH-value followed by the electrostatic interaction with the bacteria surface. TiO2-PES samples were able to carry repetitive bacterial inactivation. This presents a potential for practical applications. X-ray photoelectron spectroscopy (XPS) evidence was found for the reduction of Ti4+ to Ti3+ contributing to redox interactions between TiO2-PES and the bacterial cell wall. Insight is provided into the mechanism of interaction between the E. coli cell wall and TiO2 NPs. The properties of the TiO2-PES surface like percentage atomic concentration, TiO2-loading, optical absorption, surface charge and crystallographic phases are reported in this study.

Application of non-thermal plasma reactor and Fenton reaction for degradation of ibuprofen.

Pharmaceutical compounds have been detected frequently in surface and ground water. Advanced Oxidation Processes (AOPs) were reported as very efficient for removal of various organic compounds. Nevertheless, due to incomplete degradation, toxic intermediates can induce more severe effects than the parent compound. Therefore, toxicity studies are necessary for the evaluation of possible uses of AOPs. In this study the effectiveness and capacity for environmental application of three different AOPs were estimated. They were applied and evaluated for removal of ibuprofen from water solutions. Therefore, two treatments were performed in a non-thermal plasma reactor with dielectric barrier discharge with and without a homogenous catalyst (Fe(2+)). The third treatment was the Fenton reaction. The degradation rate of ibuprofen was measured by HPLC-DAD and the main degradation products were identified using LC-MS TOF. Twelve degradation products were identified, and there were differences according to the various treatments applied. Toxicity effects were determined with two bioassays: Vibrio fischeri and Artemia salina. The efficiency of AOPs was demonstrated for all treatments, where after 15 min degradation percentage was over 80% accompanied by opening of the aromatic ring. In the treatment with homogenous catalyst degradation reached 99%. V. fischeri toxicity test has shown greater sensitivity to ibuprofen solution after the Fenton treatment in comparison to A. salina.

Introduction of a methyl group in α- or β-position of 1-heteroarylethyl-4-phenyl-piperazines affects their dopaminergic/serotonergic properties

1‐(2‐Heteroarylalkyl)‐4‐phenylpiperazines containing methyl group in either the α‐ or the β‐position of the side alkyl chain were synthesized as racemic mixtures. They were evaluated for in vitro binding affinity at the D1 and D2 dopamine and 5‐HT1A serotonin receptors using synaptosomal membranes of the bovine caudate nucleus and hippocampus, respectively, as a source of the corresponding receptors. Tritiated SCH 23390 (D1 receptor‐selective), spiperone (D2 receptor‐selective), and 8‐OH‐DPAT (5‐HT1A receptor‐selective) were employed as the radioligands. None of the new compounds expressed significant affinity for the D1 receptor. Introduction of the methyl group into the β‐position of the parent molecules increased the affinity for the D2 receptor (10b—13b), and decreased the affinity for the 5‐HT1A receptor with the exception of imidazole (11b) which was a rather efficient displacer of 8‐OH‐DPAT. Most potent of the newly synthesized compounds in [3H]spiperone assay were compounds (±)6‐[1‐methyl‐2‐(4‐phenylpiperazin‐1‐yl)‐ethyl]‐1,4‐dihydroquinoxaline‐2,3‐dione (10b), Kd = 6.0 nM and (±)5‐[1‐methyl‐2‐(4‐phenylpiperazin‐1‐yl)‐ethyl]‐1,3‐dihydrobenzoimidazol‐2‐thione (13b), Kd = 5.3 nM. However, compounds containing methyl group in α‐position (10a—13a) of the parent molecules expressed a decreased affinity for the D2 receptor, while the affinity for the 5‐HT1A receptor remained in the same range of concentrations as that of closely related achiral parent compounds ((14—17) run in the same binding assays as references.

Microwave-hydrothermal method for the synthesis of composite materials for removal of arsenic from water

Composite material Zr-doped TiO2, suitable for the removal of arsenic from water, was synthetized with fast and simple microwave-hydrothermal method. Obtained material, Zr-TiO2, had uniform size and composition with zirconium ions incorporated into crystal structure of titanium dioxide. Synthetized composite material had large specific surface area and well-developed micropore and mesopore structure that was responsible for fast adsorption of As(III) and As(V) from water. The influence of pH on the adsorption capacity of arsenic was studied. The kinetics and isotherm experiments were also performed. The treatment of natural water sample containing high concentration of arsenic with composite material Zr-TiO2 was efficient. The concentration of arsenic was reduced to the value recommended by WHO.

Comparative Electrochemical Determination of Total Antioxidant Activity in Infant Formula with Breast Milk

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.

Planar chromatography of some 1-arylpiperazines behaving as dopaminergic ligands

The chromatographic behavior of fourteen 1-arylpiperazine derivatives has been studied by thin-layer chromatography on both silica gel and RP-18 silica gel. Unmodified silica gel was used as polar stationary phase in combination with monocomponent and binary non-polar mobile phases. Binary mobile phases comprising mixtures of methanol, acetone, or dioxane (as organic modifiers) and water were used with RP-18 silica for studies of the chromatographic behavior of the compounds under reversed-phase conditions. An approximately linear relationship was obtained between RM values and the amount of organic modifier in the mobile phases employed. The effect of mobile phase composition on the retention of the substances is discussed, as is the selectivity of the chromatographic systems used. Separation mechanisms are proposed on the basis of the results obtained.

Investigation of mechanism and critical parameters for removal of arsenic from water using Zr–TiO2 composite

ABSTRACT Using the microwave-hydrothermal method for the synthesis of composite, high surface density of hydroxyl groups, as an active adsorption sites for arsenic, was obtained. Adsorption mechanisms of As(III) and As(V) onto zirconium-doped titanium dioxide (Zr–TiO2) were investigated and proposed using macroscopic and microscopic methods. Obtained results are suggesting inner-sphere and outer-sphere adsorption mechanisms for As(III) and As(V), respectively. This allowed us to identify parameters that are critical for the successful removal of arsenic from water, which is essential information for further optimization of the removal process. The composite was further applied for the removal of As(III) and As(V) from water in a dynamic flow through the reactor. Column study proved that the removal of both arsenic species below the value recommended by WHO can be achieved. Elution of As(III) and As(V) from the composite can be done by using small amounts of 0.01 M NaOH solution resulting in preconcentration of arsenic species and possible multiple usage of composite.

Synthesis, Biological, and Computational Evaluation of Substituted 1-(2-Methoxyphenyl)-4-(1-phenethylpiperidin-4-yl)piperazines and 1-(2-Methoxyphenyl)-4-[(1-phenethylpiperidin-4-yl)methyl]piperazines as Dopaminergic Ligands.

Sixteen new 1‐(2‐methoxyphenyl)‐4‐(1‐phenethylpiperidin‐4‐yl)piperazines and 1‐(2‐methoxyphenyl)‐4‐[(1‐phenethylpiperidin‐4‐yl)methyl]piperazines were synthesized to be used as probes for mapping the dopamine D2 receptor (D2DAR) arylpiperazine binding site. All compounds were evaluated for their affinity toward D2DAR in an in vitro competitive displacement assay. The most active one was 1‐(2‐methoxyphenyl)‐4‐{[1‐(3‐nitrophenethyl)piperidin‐4‐yl]methyl}piperazine (25) with an affinity of Ki = 54 nM. Docking analysis was conducted on all herein described compounds, whereas molecular dynamic simulation was performed on ligand 25 to establish its mode of interaction with D2DAR. Two possible docking orientations are proposed; the one with a salt bridge between the piperidine moiety and Asp114 of D2DAR is more stable.