Stability of zirconia sol in the presence of various inorganic electrolytes

Zirconia sol was prepared from zirconium oxychloride solutions by forced hydrolysis at 102ºC. The prepared sol consisted of almost spherical, monoclinic, hydrated zirconia particles 61 nm in diameter. The stability of zirconia sol in the presence of various inorganic electrolytes (LiCl, NaCl, KCl, CsCl, KBr, KI, KNO3, and K2SO4) was studied by potentiometric titration method. Dependence of the critical concentration of coagulation (CCC) on the dispersion pH was determined for all studied electrolytes. The critical coagulation concentration values, for all investigated electrolytes, are lower at higher pH. These values for all 1:1 electrolytes are equal in the range of experimental error. For a given pH value, CCCs of K2SO4 are 3-4 orders of magnitude lower than the corresponding values for 1:1 electrolytes. [Projekat Ministarstva nauke republike Srbije, br. III 45012

Study of copper adsorption on aminofunctionalized macroporous poly(gma-co-egdma)

Macroporous crosslinked copolymer of glycidyl methacrylate and ethylene glycoldimethacrylate (PGME) was synthesized by suspension copolymerisation and modified by ring-opening reaction of epoxy groups with ethylene diamine, diethylene triamine and triethylene tetramine. The uptake of copper ions by amino-functionalized macroporous PGME from aqueous solutions was investigated in batch experiments. The equilibrium data fitted well with the Langmuir model.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Kinetics of heavy metal sorption on macroporous vinylpyridine based copolymer

Sorption of copper, nickel and cobalt on macroporous crosslinked copolymer of 4- vinylpyridine and ethylene glycol dimethacrylate, PVPE, was studied. The kinetics models (pseudo-first and pseudo-second order equations) were applied to the data obtained from batch sorption experiments at room temperature. The sorption of heavy metals was found to proceed according to pseudo-second order kinetics.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Analysis of hexavalent chromium sorption on macroporous copolymer grafted with hexamethylene diamine

In this study, macroporous glycidyl methacrylate based copolymers with different crosslinking degree and porosity parameters, functionalized with hexamethylene diamine were tested for Cr(VI) sorption.[http://savremenimaterijali.info/sajt/doc/file/SM2013/SM2013_KNJIGA_APSTRAKATA.pdf

Determination of ionization constants (PKA) of β-hydroxy-β-arylalkanoic acids using high-pressure liquid chromatography

pKa values of five β-hydroxy-β-arylalkanoic acids and ibuprofen were determined using the RP-HPLC method. Stationary phase was octadecyl modified (C-18) silica gel, and mobile phase was a mixture of methanol and one of nine different buffers (60:40, v/v). wspH values were measured after mixing methanol with an appropriate buffer. The mean retention time of each compound was plotted against wspH of each mobile phase. The inflection point of each sigmoidal curve represented wspK a of the compound. Using wspK a in already known equations for the specific methanol/buffer mixture, wwpK a values were calculated. Obtained pKa values for synthesized compounds were in a narrow range from 3.34-3.81 and pKa for ibuprofen was 4.45. Predicted pKa values for these compounds in SPARC software showed good correlation with experimental pKa values (R2=0.8048)

Analysis of factors influencing Cu(II) sorption by clinoptiolite

The effects of initial metal concentration and pH, as well as the sorbent mass and particle size, on Cu(II) sorption by natural clinoptilolite were evaluated and compared. Full factorial experimental design at two levels was applied. Statistically significant factors were determined considering residual Cu(II) concentrations as a system response.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Determination of ionization constants (PKA) of β-hydroxy-β-arylalkanoic acids using high-pressure liquid chromatography

pKa values of five β-hydroxy-β-arylalkanoic acids and ibuprofen were determined using the RP-HPLC method. Stationary phase was octadecyl modified (C-18) silica gel, and mobile phase was a mixture of methanol and one of nine different buffers (60:40, v/v). wspH values were measured after mixing methanol with an appropriate buffer. The mean retention time of each compound was plotted against wspH of each mobile phase. The inflection point of each sigmoidal curve represented wspK a of the compound. Using wspK a in already known equations for the specific methanol/buffer mixture, wwpK a values were calculated. Obtained pKa values for synthesized compounds were in a narrow range from 3.34-3.81 and pKa for ibuprofen was 4.45. Predicted pKa values for these compounds in SPARC software showed good correlation with experimental pKa values (R2=0.8048)

Influence of Co2+ ions on photocatalytic properties of MgFe2O4 ferrites

In this work, spinel magnesium cobalt ferrites (CoxMg1-xFe2O4, x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9) were synthesized by a sol-gel combustion method. Magnesium nitrate, cobalt nitrate and iron nitrate were used as oxidizers and citric acid was used as a reducing agent. The effects of cobalt ions on structural and morphological properties were investigated and characterized by X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscope (FESEM) and Fourier transform infrared (FT-IR) spectroscopy. A cubic spinel structure formed with a varied distribution of cobalt and magnesium ions on tetrahedral and octahedral sites that depended on their content. All ferrite powders consisted of multigrain agglomerates. Optical properties were investigated by UV- vis spectrophotometry. The photocatalytic activity of as prepared samples was evaluated by measuring the rate of photodegradation reaction of methylene blue (MB) under visible light irradiation. After 240 min, compared to other samples, the sample labeled as Co0.1Mg0.9Fe2O4 showed the best rate of photodecomposition of MB resulting in reduction of 90% of its initial concentration

Visible light photocatalytic activity of nanocrystalline CoxMg1-xFe2O4 (x = 0-1)

The sol-gel combustion method was applied for synthesis of spinel magnesium cobalt ferrites CoxMg1-xFe2O4, with varying cobalt and magnesium content, x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9. Magnesium nitrate, cobalt nitrate and iron nitrate were used as oxidizers and citric acid was used as a reducing agent. Structural and morphological properties of the obtained ferrite powders were investigated and characterized by X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscope (FESEM) and Fourier transform infrared (FT-IR) spectroscopy. Optical properties were investigated by UV-VIS spectrophotometry. A cubic spinel structure with multigrain agglomerates formed. Visible light photocatalytic activity of the spinel ferrite powder samples was evaluated by measuring the rate of photodegradation reaction of methylene blue (MB). After 240 min Co0.1Mg0.9Fe2O4 showed the best rate of photodecomposition of MB resulting in 90% of its initial concentration in an alkaline environment

STOCK MARKET TREND PREDICTION USING SUPPORT VECTOR MACHINES

The aim of the paper was to outline a trend prediction model for the BELEX15 stock market index of the Belgrade stock exchange based on Support Vector Machines (SVMs). The feature selection was carried out through the analysis of technical and macroeconomics indicators. In addition, the SVM method was compared with a "similar" one, the least squares support vector machines - LS-SVMs to analyze their classification precisions and complexity. The test results indicate that the SVMs outperform benchmarking models and are suitable for short-term stock market trend predictions