Determination of the point of zero charge of alumina by batch equilibration method

In this work we present the points of zero charge, pHpzc, of five commercial alumina samples, of an alumina/solution ratio of 0.100g/25 ml, obtained by batch equilibration method. As an inert electrolyte, KNO3 of 0.001 - 0.1 moldm-3 concentration was used. The obtained points of zero charge values are about 7 and they are independent of KNO3 concentration, except the sample labeled as ICN (Alumina B). In this case, the increase in electrolyte concentration (from 0.001 to 0.1 moldm-3) leads to a decrease in pHpzc (from 7.5 to 6.7) indicating specific sorption of K+ ions on the sample.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Determination of intrinsic equilibrium constants at an alumina/electrolyte interface

Intrinsic ionization and complexation constants at an alumina/electrolyte interface were studied by the site binding model, while the sorption of alkali cations from aqueous solutions was interpreted by the triple-layer model. The surface properties of alumina were investigated by the potentiometric acid-base titration method. The point of zero charge (pH(pzc)) of alumina obtained by this method was found to be 7.2. The obtained mean values of the intrinsic protonation and ionization constants of the surface hydroxyl groups and the intrinsic surface complexation constant, in different electrolytes, are pK(a1)(int) = 4.4, pK(a2)(int) = 9.6 and pK(M+)(int) = 9.5, respectively

Neural network prediction of the gas chromatographic separation of polycyclic aromatic hydrocarbons

This paper describes the application of artificial neural networks (ANNs) method to the modeling of 13 polycyclic aromatic hydrocarbons (PAHs)retentionsin temperature - programmed gas chromatography.The ANN method used resulted in relatively good agreement (RMStesting = 0.018) between the measured and the predicted retention times for 13 PAHs. Somewhat higher discrepancy in prediction was observed for the late – eluted PAHs at lower temperature ramps.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Seasonal variations of concentrations of inorganic anions in atmospheric aerosols

8. Simpozijum "Hemija i zaštita životne sredine" sa međunarodnim učešćem : Knjiga izvoda ; 30. maj - 1. jun 2018; Kruševac, Srbija8th Symposium Chemistry and Environmental Protection with international participation : Book of Abstracts ; 30th May - 1st June 2018 ; Kruševac, Serbi

Analytical methods for arsenic speciation analysis

Arsenic exists in the form of various chemical species differing in their physicochemical behaviour, toxicity, bioavailability and biotransformation. The determination of arsenic species is an important issue for environmental, clinical and food chemistry. However, differentiation of these species is a quite complex analytical task. Numerous speciation procedures have been studied that include electrochemical, chromatographic, spectrometric and hyphenated techniques. This review presents the relevant research in the field of arsenic speciation analysis with novel applications and significant advances. Stability of arsenic species and each of the analytical steps (sample collection, storage, preservation, extraction) of the arsenic speciation methods is particularly evaluated. Analytical validation and performance of these Methods are also reviewed

Ambient air particles: The use of ion chromatography and multivariate techniques in the analysis of water-soluble substances

Seventeen water-soluble substances (of sodium, ammonium, potassium, magnesium, calcium, formate, methanesulfonate, glyoxylate, chloride, nitrite, nitrate, glutarate, succinate, malate, malonate, sulfate and oxalate) in 94 samples of particle matter in the ambient air, collected over ten months, in a suburb of Belgrade (Serbia), were determined by ion chromatography. To apportion the sources of the air pollution, the log-transformed data were processed by applying multivariate techniques. Principal component and factor analysis identified three main factors controlling the data variability: stationary combustion processes with the highest loadings of oxalate, malonate and malate; landfill emission and secondary inorganic aerosol characterized by high levels of ammonium, nitrate and sulfate; a contribution of mineral dust composed of magnesium, calcium and chloride. The hierarchical cluster analysis pointed out a differentiation of the samples into five groups belonging to different variables inputs. For the classification of ambient air samples using nine selected ions, the recognition ability of linear discriminant analysis, k-nearest neighbors, and soft independent modeling of class analogy were 87.0, 94.6, and 97.8 %, respectively. Time-series analysis showed that the traffic emission is more pronounced in winter in contrast to the mineral dust influence, while the effect of waste combustion exhibits no trend

Production of fragments with Z GT = 8 in interaction of 12.7 GeV He-4+U, Pb, Au and Ag: track detector study

The processes of production of fragments with Z greater than or equal to 8 in the interaction of 12.7 GeV He-4 with U, Pb, Au and Ag have been analyzed using the polycarbonate track detector Makrofol. The sandwich technique was used which enables direct observation of multiply charged fragment emission by a single nucleus. The decay channels ending with one, two, or more (three, four) fragments were detected. A classification scheme based on the multiplicity of heavy fragments with Z GT 20 was used in order to identify the events belonging to the different reaction channels. The cross sections, excitation energies and multiplicities of intermediate-mass fragments 8 less than or equal to Z less than or equal to 20 have been determined for the various reaction mechanisms, and their variation as a function of the target mass has been investigated

Seasonal variations of concentrations of low-molecular weigth organic acids in atmospheric aerosols

In addition to inorganic ions, low-molecular weight organic acids (LMWOA) form one of the major components of atmospheric aerosols (Djordjević et al, 2012; Joksić et al, 2009). LMWOAs contribute significantly to the presence of organic matter in the aerosol. LMWOA concentrations as well as inorganic anions concentrations vary significantly depending on location and season (Todorović at al, 2018). In this paper, samples of atmospheric aerosols sampled in Belgrade are analyzed for LMWOA content and its seasonal variation