Modification of porous structure of Ca- smectit, copolymer of glycidilmethacrylate and their composite

Smektitna glina iz domaćeg ležišta „Bogovina“, je modifikovana sa različitim koncentracijama HCl kiseline (1,5 - 7,5M). Rendgeno-difrakcionom analizom je utvrđeno prisustvo minerala smektita i pratećih minerala kvarca, kalcita, ilita i feldspata. Na osnovu rezultata hemijske analize, infracrvene spektroskopije (IC), termogravimetrijske ( TG) analize utvrđeno je da u ispitivanim uzorcima dolazi do izmene katjona već pri koncentraciji HCl od 1,5 M. Pri modifikaciji smektita sa kiselinom koncentracije 3 M pored katjonske izmene Na+, Ca2+ sa H+dolazi do delimičnog narušavanja oktaedarskih slojeva u strukturi smektita. Uzorci modifikovani kiselinom veće koncentracije pored navedenih promena imaju i povećanu količinu prisutne amorfne faze. Modifikacija strukture uzoraka smektita različitim koncentracijama HCl kiseline utiče na promenu zapremine makro, mezo i mikro pora. Suspenzionom kopolimerizacijom su sintetisani porozni kopolimeri poli(GMA-co-EGDMA) pri različitom odnosu monomera glicidilmetakrilata (GMA) i etilenglikoldimetakrilata (EGDMA) u prisustvu inicijatora radikalne kopolimerizacije azobisizobutironitrila (AIBN) i inertne komponente. Ispitan je uticaj različitih vrsta i udela umreživača kao i udela alifatskih alkohola u inertnoj komponenti na poroznu strukturu kopolimera. Pri sintezi kompozita korišćena je kopolimerna matrica sa odnosom GMA i umreživača EGDMA 60/40 i inertnom komponentom koja predstavlja smešu cikloheksanola i tetradekanola u odnosu 4:1, uz dodatak nemodifikovanog smektita i smektita modifikovanog 3 M HCl. Utvrđeno da je stepen ugradnje nemodifikovanog smektita u kopolimernu matricu znatno manji, dok je ugradnja kiselo modifikovanog smektita skoro 2 puta efikasnija. SEM analizom su ispitana morfološka svojstva kompozita. Pokazano je da se samo u slučaju kompozita sa smektitom modifikovanim kiselinom dobijaju čestice koje su iste veličine kao i kopolimerne, sa razvijenom makroporoznom strukturom. Utvrđeno je da kompozit sa kiselim smektitom znatno poboljšava termičku stabilnost kopolimera. Makroporozna struktura kompozita je određena Hg-porozimetrijom i dobijeni rezultati pokazuju povećanje specifične površine i pomeranje raspodele veličine pora ka manjim prečnicima pora.Local smectite clay from „Bogovina“ was modified with HCl acid having different concentrations (1.5 – 7.5 M). The X-ray diffraction analysis confirmed the presence of smectite and impurities like quartz, calcite, illite and feldspar. According to results of chemical analysis, infrared (IR) spectroscopy and thermogravimetric (TG) analaysis it was confirmed that the cation exchange already occurred at 1.5 M HCl. Smectite modification with 3 M HCl beside cation exchange of Na+, Ca2+ with H+ lead to partial derogation of octahedral layers of smectite structure. Samples modified with higher acid concentrations beside all mention changes also had increased amount of amorphous phase. The modifications in smectite structure with different HCl concentrations caused change in macro, meso i micro pore volume. Porous copolymers poly(GMA-co-EGDMA) with different ratios of GMA and EGDMA monomers were synthesized by suspension copolymerization in a presence of the azobisisobytironitrile (AIBN) as an initiator, and inert component. The influence of type of and amount of cross-linker as well as the ratios of aliphatic alcohols in the inert component on porous structure of copolymer were investigated. The copolymer matrix with monomer GMA and EGDMA ratio 60/40 and inert componet (mixture of cyclohexanol and tetradecanol 4:1) were used for synthesis of the composite together with either unmodified smectite or smectite modified with 3 M HCl. It was established that the degree of incorporation of unmodified smectite into copolymer matrix is rather low, while the incorporation of acid modified smectite is approx. twice more efficient. SEM analysis revealed morphological properties of composite. It was shown that only particles of composite with acid modified smectite were within the same range as the copolymer particles with developed macroporous structure. It was confirmed that composite with acid modified smectite significantly enhanced thermal stability of copolymer. Macroporous structure composite established by Hg-porosimetry and the obtained results indicated increase in specific surface area and shift in the distribution of pore diameter size toward lower pore diameters

The future of development rural tourism in the Republic of Serbia

The article analyzes the current character and dynamics of rural tourism development and points to the positive multiplicative impact that it has on rural areas. Also, authors give guidelines how rural tourism could be developing and how it can be developing on successful way. Expectations are that development rural tourism would eliminate current negative trends that burden the lives of local population. Authors highlight the importance and role that rural tourism will have in future global tourism development in Serbia

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

Effect of the genotype: Environmental interaction on phenotype variation of the bunch weight in white wine varieties

The aim of this paper is to establish the interaction of phenotypical variations, components of yield for the widest spread wine varieties and external factors of the Danube region in the central Serbia. The number of fruitful buds per vine for twenty-one varieties was the same, whereas the yield and the components of the yield were different. The growing season, from bud burst to full ripening of the grapevine and the sum of active temperatures for the same period, were of crucial importance. In the factor analysis, three factors have been singled out: the first factor couples the mean air temperature; the second factor delineates the values according to genotype characteristics, sugar content and acids in the must, and the third factor indicates that bunch weight had the major effect on the yield of grapes. By the application of bunch analysis, a hierarchy tree was formed to include the four groups of varieties. The most numerous group, consisting of 18 varieties, is characterized by top quality grapes (21.5% sugar content), medium yield (1.52 kg/m2) and a proportional relation of total acids (7.5 g/l) and this is achieved during the middle of the ripening period

Uticaj termičkog tretmana na mikro-strukturu alumine sa dodatkom PEG-a i La3+ dobijene sol-gel postupkom

Active porous alumina was prepared via a sol-gel method and subjected to thermal treatment in the temperature range 500 - 1200°C. The effect of calcinations temperature, polyethylen glycol combined with La3+, added to the boehmite sol, on activated alumina surface area, pore size, pore distribution and surface fractal dimension was studied. The N2 adsorption/desorption analyses of samples was performed to determine the adsorption isotherms, hysteresis and the textural properties. The adding of La3+ to boehmite sol inhibits the surface area loss of produced aluminas during its calcinations at high temperatures. Thermal treatment of La3+-doped alumina samples at temperature from 500 to 1200°C causes a considerable decrease of its specific surface area from 280 to 65 m2g-1, pore volume from 0,44 to 0,27 cm3g-1, increase of its pore size data from 3 to 6 nm and increase of its surface fractal dimension form 2,068 to 2,192. From behavior of surface fractal dimension of doped alumina samples can be concluded that there is no phase transformation to α-Al2O3 in all temperature range, i.e. addition of lanthanum to boehmite sol in atomic ratio of 0,03 La3+/Al3+ can raise phase transformation temperature to α-Al2O3 above 1200°C. .Aktivni porozni aluminijumoksid, dobijen sol - gel metodom, je termički obrađen na povišenim temperaturama u intervalu od 500 do 1200°C. Ispitivan je uticaj temperature termičke obrade i dodatka polietilen glikola (PEG) i La3+-jona na specifičnu površinu, zapreminu pora i prečnik pora, kao i fraktalnu dimenziju površine aktiviranog aluminijum-oksida. Na osnovu podataka iz adsorpciono-desorpcionih izotermi azota određen je tip pora i izračunate su vrednosti osnovnih parametara teksturalnih svojstava uzoraka. Porast temperature termičke obrade prouzrokovao je smanjenje specifične površine sa 280 na 65 m2g-1, zapremine pora sa 0,45 na 0,27 cm3g-1, porast preovlađujućeg prečnika pora od 3 do 6 nm i porast fraktalne dimenzije površine od 2,068 do 2,192. Na osnovu dobijenih rezultata rendgenostrukturne analize može se zaključiti da u ispitivanom temperaturnom intervalu ne dolazi do fazne transformacije u α-Al2O3 i da dodatak lantana u odnosu 0,03 molLa3+/ molAl3+ pomera faznu transformaciju aktiviranog aluminijum-oksida u α-Al2O3 iznad 1200°C.

Uticaj termičkog tretmana na mikro-strukturu alumine sa dodatkom PEG-a i La3+ dobijene sol-gel postupkom

Active porous alumina was prepared via a sol-gel method and subjected to thermal treatment in the temperature range 500 - 1200°C. The effect of calcinations temperature, polyethylen glycol combined with La3+, added to the boehmite sol, on activated alumina surface area, pore size, pore distribution and surface fractal dimension was studied. The N2 adsorption/desorption analyses of samples was performed to determine the adsorption isotherms, hysteresis and the textural properties. The adding of La3+ to boehmite sol inhibits the surface area loss of produced aluminas during its calcinations at high temperatures. Thermal treatment of La3+-doped alumina samples at temperature from 500 to 1200°C causes a considerable decrease of its specific surface area from 280 to 65 m2g-1, pore volume from 0,44 to 0,27 cm3g-1, increase of its pore size data from 3 to 6 nm and increase of its surface fractal dimension form 2,068 to 2,192. From behavior of surface fractal dimension of doped alumina samples can be concluded that there is no phase transformation to α-Al2O3 in all temperature range, i.e. addition of lanthanum to boehmite sol in atomic ratio of 0,03 La3+/Al3+ can raise phase transformation temperature to α-Al2O3 above 1200°C. .Aktivni porozni aluminijumoksid, dobijen sol - gel metodom, je termički obrađen na povišenim temperaturama u intervalu od 500 do 1200°C. Ispitivan je uticaj temperature termičke obrade i dodatka polietilen glikola (PEG) i La3+-jona na specifičnu površinu, zapreminu pora i prečnik pora, kao i fraktalnu dimenziju površine aktiviranog aluminijum-oksida. Na osnovu podataka iz adsorpciono-desorpcionih izotermi azota određen je tip pora i izračunate su vrednosti osnovnih parametara teksturalnih svojstava uzoraka. Porast temperature termičke obrade prouzrokovao je smanjenje specifične površine sa 280 na 65 m2g-1, zapremine pora sa 0,45 na 0,27 cm3g-1, porast preovlađujućeg prečnika pora od 3 do 6 nm i porast fraktalne dimenzije površine od 2,068 do 2,192. Na osnovu dobijenih rezultata rendgenostrukturne analize može se zaključiti da u ispitivanom temperaturnom intervalu ne dolazi do fazne transformacije u α-Al2O3 i da dodatak lantana u odnosu 0,03 molLa3+/ molAl3+ pomera faznu transformaciju aktiviranog aluminijum-oksida u α-Al2O3 iznad 1200°C.

Hybrid macroporous polymer/clay nanocomposites

Hybrid polymer/nanocomposites are a new class of materials that consist of polymer matrix and clay nanoparticles as the dispersed phase. The aim of this work was to obtain macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)/clay nanocomposites p(GEM-NC) with different porosity and morphology. Macroporous p(GEM) copolymer and two nanocomposite p(GEM-NC) samples with different clay content (2 and 5 wt.%) were synthesized by in situ suspension copolymerization. Nanocomposite samples were reinforced with organomodified montmorillonite clay Cloisite 30B (C30B). Structure, porosity and surface chemistry of the p(GEM) and p(GEM-NC) samples were evaluated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM/EDS) and mercury porosity. The results show the synthesized p(GEM-NC) have improved textural, structural and morphological properties in comparison with pure macroporous p(GEM) copolymer. The incorporation of C30B in p(GEM) was confirmed by FTIR and SEM/EDS analysis. Also, it was shown that the higher clay content significantly influences the p(GEM-NC) porosity parameters (i.e. specific surface area, specific volume and pore diameter).[http://www.serbianceramicsociety.rs/doc/ACA-VI-Program-and-Book-of-Abstracts.pdf

Development and Validation of Chronopotentiometric Method for Imidacloprid Determination in Pesticide Formulations and River Water Samples

A new electrochemical method for determination of imidacloprid using chronopotentiometry on thin film mercury and glassy carbon electrode was presented. The most important experimental parameters of chronopotentiometry were examined and optimized with respect to imidacloprid analytical signal. Imidacloprid provided well-defined reduction peak in Britton-Robinson buffer on thin film mercury electrode at -1.0V (versus Ag/AgCl (KCl, 3.5 mol/L)) and on glassy carbon electrode at -1.2V (versus Ag/AgCl (KCl, 3.5mol/L)). The reduction time was linearly proportional to concentrations from 0.8 to 30.0 mg/L on thin film mercury electrode and from 7.0 to 70.0mg/L on glassy carbon electrode. The detection limits were 0.17mg/L and 0.93mg/L for thin film mercury and glassy carbon electrode, respectively. The estimation of method precision as a function of repeatability and reproducibility showed relative standard deviations values lower than 3.73%. Recovery values from 97.3 to 98.1% confirmed the accuracy of the proposed method, while the constancy of the transition time with deliberated small changes in the experimental parameters indicated a very good robustness. A minor influence of possible interfering compounds proved good selectivity of the method. Developed method was applied for imidacloprid determination in commercial pesticide formulations and river water samples

Influence of bentonite filler on the thermal stability of glycidyl methacrylate based composite

Macroporous crosslinked copolymer of glycidyl methacrylate, GMA, and ethylene glycol dimethacrylate, EGDMA, poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) and its composites were synthesized by suspension copolymerization. Composites were obtained by introducing 10 mass % of either raw bentonite (S0) or acid modified bentonite (SA) into reaction system. The composite synthesized with SA as filer showed superior thermal stability comparing to starting copolymer and composite with S0 embedded in copolymer matrix

Optimalno faktorno planiranje procesa kiselinske aktivacije bentonita u mikrotalasnom polju

In this study, the statistical design of the experimental method was applied on the process of acid activation of bentonite with microwave irradiation. The influence of activation parameters (time, acid normality and microwave heating power) on the selected process response of the activated bentonite samples was studied. The specific surface area was chosen for the process response, because the chemical, surface and structural properties of the activated clay determine and limit its potential applications. The relationship of various process parameters with the specific surface area of bentonite was examined. A mathematical model was developed using a second-order response surface model (RSM) with a central composite design incorporating the above mentioned process parameters. The developed mathematical model helped to predict the variation in specific surface area of activated bentonite with time (5-21 min), acid normality (2-7 N) and microwave heating power (63?172 W). The calculated regression models were found to be statistically significant at the required range and presented little variability. Furthermore, high values of R2 (0.957) and R2 (adjusted) (0.914) indicate a high dependence and correlation between the observed and the predicted values of the response. These high values also indicate that about 96% of the result of the total variation can be explained by this model. In addition, the model shows that increasing the time and acid normality improves the textural properties of bentonites, resulting in increased specific surface area. This model also can be useful for setting an optimum value of the activation parameters for achieving the maximum specific surface area. An optimum specific surface area of 142 m2g-1 was achieved with an acid normality of 5.2 N, activation time of 7.38 min and microwave power of 117 W. Acid activation of bentonite was found to occur faster with microwave irradiation than with conventional heating. Microwave-assisted processes have the potential to develop into a cost efficient route for acid activation of bentonite.Radi dobijanja efikasnog adsorbensa štetnih i opasnih materija izvršena je optimizacija parametara procesa sinteze kiselinski aktiviranog bentonita u mikrotalasnom polju na bazi statističkih planova eksperimenta. Tokom planiranja eksperimenata razmatran je uticaj snage mikrotalasnog polja, vremena aktivacije i koncentracije kiseline na poroznu strukturu aktiviranog materijala. Utvrđeno je da specifična površina zavisno od uslova procesa, ima minimalnu vrednost od 114,0 m2 g-1 za adsorbens sintetisan pri uslovima definisanim u eksperimentu 11 (4,5 N HCl, 21 min i 117 W), a maksimalnu vrednost od 153,5 m2 g-1 za adsorbens dobijen u eksperimentu 8 (3 N HCl, 17 min i 85 W). Ustanovljeno je da tokom procesa kiselinske aktivacije bentonita u mikrotalasnom polju najveći uticaj na formiranje specifične površine ima faktor vreme. Rezultati optimizacije procesa zasnovane na funkciji poželjnosti uz uslov minimalnog vremena aktivacije, vrednosti koncentracije kiseline i snage mikrotalasnog zračenja u zadatom opsegu, pokazali su da je optimalno vreme aktivacije bentonita u mikrotalasnom polju 7,38 min dok kod hidrotermalne aktivacije sa kiselinom iste koncentracije potrebno vreme iznosi 2,8 h