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Search Results: 1 - 10 of 208928 matches for " Lazi? Miodrag L. "
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Gas-holdup in a 16.6 cm I.D. reciprocating plate column
Vasi? Ljubi?a S.,Bankovi?-Ili? Ivana B.,LaziMiodrag L.,Veljkovi? Vlada B.
Hemijska Industrija , 2005, DOI: 10.2298/hemind0510263v
Abstract: The effects of operation conditions (the vibration intensity and gas flow rate) on the gas holdup in a 16.6 cm i.d. two-phase reciprocating plate column (RPC) were studied. Distilled water and aqueous solutions of carboxymethyl-cellulose of different concentration were used as the liquid phase and air as the gas phase in this investigation. The gas holdup was measured after the gas flow and the reciprocating action had been stopped. An empirical correlation which correlates the gas holdup with the specific power consumption and the superficial gas velocity showed that the aeration intensity had a greater influence on the gas holdup than the intensity of agitation. Because the gas holdup was approximately the same in RPC's of different diameters, an equation relating the gas holdup with the specific power consumption and the superficial gas velocity was derived. The correlation could be used in the scaling up of reciprocating plate columns.
Biodiesel production by enzyme-catalyzed transesterification
Stamenkovi? Olivera S.,LaziMiodrag L.,Veljkovi? Vlada B.,Skala Dejan U.
Hemijska Industrija , 2005, DOI: 10.2298/hemind0504049s
Abstract: The principles and kinetics of biodiesel production from vegetable oils using lipase-catalyzed transesterification are reviewed. The most important operating factors affecting the reaction and the yield of alkyl esters, such as: the type and form of lipase, the type of alcohol, the presence of organic solvents, the content of water in the oil, temperature and the presence of glycerol are discussed. In order to estimate the prospects of lipase-catalyzed transesterification for industrial application, the factors which influence the kinetics of chemically-catalysed transesterification are also considered. The advantages of lipase-catalyzed transesterification compared to the chemically-catalysed reaction, are pointed out. The cost of down-processing and ecological problems are significantly reduced by applying lipases. It was also emphasized that lipase-catalysed transesterification should be greatly improved in order to make it commercially applicable. The further optimization of lipase-catalyzed transesterification should include studies on the development of new reactor systems with immobilized biocatalysts and the addition of alcohol in several portions, and the use of extra cellular lipases tolerant to organic solvents, intracellular lipases (i.e. whole microbial cells) and genetically-modified microorganisms ("intelligent" yeasts).
Comparison of antioxidant and antimicrobial activities of extracts obtained from Salvia glutinosa L. and Salvia officinalis L.
Veli?kovi? Dragan T.,Karabegovi? Ivana T.,Stoji?evi? Sa?a S.,LaziMiodrag L.
Hemijska Industrija , 2011, DOI: 10.2298/hemind110412034v
Abstract: Antioxidant and antimicrobial activities as well as total phenols and flavonoids contents of Salvia glutinosa L. (glutinous sage) and Salvia officinalis L. (sage) extracts were studied. Methanol and aqueous ethanol (70% v/v) were used for extraction of bioactive compounds, both in the presence and the absence of ultrasound, from herb and the spent plant material remaining after the essential oil hydrodistillation. The ratio of plant material to extracting solvent was 1:10 g/ml. Antioxidant and antimicrobial activities of the extracts were found to depend on the type of plant material and the extraction conditions. The plant materials from which essential oil had been recovered were proven to be valuable raw materials for making various herbal preparations.
Clarification and filtration of the floculated partuicles suspension from a chemical treatment of waste oil-in-water emulsions from a non-ferrous metalworking plant
Lazarevi? Vesna B.,Krsti? Ivan M.,Taki? Ljiljana M.,LaziMiodrag L.
Hemijska Industrija , 2011, DOI: 10.2298/hemind100801054l
Abstract: The effects of the coagulation/floculation conditions on clarification and filtration of the floculated particle suspension obtained by the chemical treatment of the waste oil-in-water emulsion (OWE) from a non-ferrous metalworking plant were studied. The treatment involved the addition of aluminum(III) sulfate and lime to the OWE. The main goal was to define the optimum conditions for clarification and filtration of the floculated particle suspension. The factors involved were amounts lime (i.e. pH) and filter aid added the OWE on clarification and filtration rates. At pH>10, the clarification rate was increased and the final volume of the concentrated suspension (sludge) was reduced, while filter aid affected negatively the clarification rate. The filtration rate was also increased when the coagulation was carried out at pH>10. The floculated particle suspension should be concentrated before filtration in order to decrease the filtration duration. The most efficient filter aid was Celite standard super-cel, its optimum initial concentration being found to be 2 g/dm3.
Pyrite oxidation by Acidithiobacillus ferrooxidans bacteria
Savi? Dragi?a S.,LaziMiodrag L.,Veljkovi? Vlada B.,Vrvi? Miroslav M.
Hemijska Industrija , 2005, DOI: 10.2298/hemind0502015s
Abstract: The kinetic model of pyrite particle dissolution by the action of bacteria Acidithiobacillus ferrooxidans in a shaken Erlenmeyer flask was presented. The model agreed well with the experimental data for the extracted iron and the number of cells in the liquid phase. The specific growth rate of the adsorbed cells was evaluated (μA = 1,6 d-1) by fitting the experimental data to the model curve. Also, the relevance of the two proposed mechanisms for the bacterial dissolution of sulphide (direct and indirect) was discussed, indicating that the indirect one was dominant. The adsorption process of A. ferrooxidans to the pyrite surface was well correlated by a Langmuir type isotherm.
Scaling up the chemical treatment of spent oil-in-water emulsions from a non-ferrous metal-processing plant
Lazarevi? Vesna B.,Krsti? Ivan M.,LaziMiodrag L.,Savi? Dragi?a S.
Hemijska Industrija , 2013, DOI: 10.2298/hemind120317055l
Abstract: The treatment of spent oil-in-water emulsion (SOWE) from a non-ferrous metal-processing plant by using aluminum sulfate and hydrated lime was studied to determine the purification efficiency, to optimize the operating conditions and to scale up the treatment process. The purification efficiency was estimated by comparing the compositions of the SOWE and the processed wastewater. The treatment efficiency does not depend on the type of mineral oil and filter aid. The optimum doses of aluminum sulfate and hydrated lime must be experimentally determined for each batch of SOWEs, but the results obtained at laboratory level are applicable at pilot level. The processed wastewater and the filter cake from the process can be safely disposed into public sewage systems and at municipal waste landfills, respectively. The purification efficiency was higher than 98% with respect to total suspended solids, chemical oxygen demand and oil and grease, and was comparable to the known treatment processes based on coagulation/flocculation followed by sedimentation.
Enzymatic hydrolysis of potato starch and ethanol production
LaziMiodrag L.,Ra?kovi? Suzana,Stankovi? Mihajlo Z.,Veljkovi? Vlada B.
Hemijska Industrija , 2004, DOI: 10.2298/hemind0408322l
Abstract: The hydrolysis of potato starch using one (Termamyl or Fungamyl) and two combined (Termamyl and Supersan) commercial enzyme preparations and ethanol production from the hydrolysates obtained using the yeast Saccharomyces cerevisiae were studied. Potato tubers were previously prepared as mash or flour. The study dealt with the effects of the hydromodulus (1:1 and 1:0.5), particle size (0.1, 0.2 and 0.4 mm) as well as the type and concentration of enzyme on the enzymatic hydrolysis of potato starch. The highest dextrose equivalent (79.3%, DE) was achieved during two-enzyme hydrolysis (combination of two enzyme preparations: Termamyl 14.4 KNU/dm3 and Supersan 28.8 AGU/dm3) of starch from potato flour (particle size: 0.1-0.2 mm) at an inital starch concentration of 75 g/dm3. During the two-enzyme hydrolysis, a lower DE (61%) was achieved when potato mash was used as a starch source. Using Termamyl (14,4 KNU/dm3) and potato mash a higher DE was achieved at the hydromodulus 1:1 (51.2%) than at the hydromodulus 1:0.5 (40.9%). The highest ethanol concentration (5.0 vol%) was obtained when the hydrolyzate of potato flour from the two-enzyme process was used as a substrate for alcoholic fermentation.
Bioethanol: State and perspectives
Tasi? Marija B.,Bankovi?-Ili? Ivana B.,LaziMiodrag L.,Veljkovi? Vlada B.
Hemijska Industrija , 2006, DOI: 10.2298/hemind0602001t
Abstract: Processes of bioethanol production currently applied all over the world are reviewed in this paper. Attention is focused on potentially cheap biomass sources, as well as the most important operating factors controlling the progress and result of saccharification and fermentation reactions and affecting the yield of fermentable sugars and ethanol, respectively, such as: the type and concentration of acid, the type of enzyme, the type of working microorganism, operating temperature, duration time and pH. The hydrolysis conditions, namely duration time, temperature and sulfuric acid concentration, were combined in a single parameter, known as the "combined severity" (CS), in order to estimate the efficiency of bioethanol production from biomass. When the CS increases, the yield of fermentable sugars also increases. The decrease in the yield of monosaccharides coincides with the maximum concentrations of by-products, such as furfural and 5-hydroxymethylfurfural, which are well-known as yeast inhibitors. The highest ethanol yields has been obtained using the yeast Saccharomyces cerevisiae. With low oil prices and political reluctance to implement carbon taxes, fuel-ethanol production will remain uncompetitive unless some other form of cost reduction can be made, such as feedstock preparation costs.
Gas holdup in a reciprocating plate bioreactor: Non-Newtonian - liquid phase
Naseva Olivera S.,Stamenkovi? Ivica S.,Bankovi?-Ili? Ivana B.,LaziMiodrag L.
Hemijska Industrija , 2002, DOI: 10.2298/hemind0205198n
Abstract: The gas holdup was studied in non-newtonian liquids in a gas-liquid and gas-liquid-solid reciprocating plate bioreactor. Aqueous solutions of carboxy methyl cellulose (CMC; Lucel, Lu ane, Yugoslavia) of different degrees of polymerization (PP 200 and PP 1000) and concentration (0,5 and 1%), polypropylene spheres (diameter 8.3 mm; fraction of spheres: 3.8 and 6.6% by volume) and air were used as the liquid, solid and gas phase. The gas holdup was found to be dependent on the vibration rate, the superficial gas velocity, volume fraction of solid particles and Theological properties of the liquid ohase. Both in the gas-liquid and gas-liquid-solid systems studied, the gas holdup increased with increasing vibration rate and gas flow rate. The gas holdup was higher in three-phase systems than in two-phase ones under otter operating conditions being the same. Generally the gas holdup increased with increasing the volume fraction of solid particles, due to the dispersion action of the solid particles, and decreased with increasing non-Newtonian behaviour (decreasing flow index) i.e. with increasing degree of polymerization and solution concentration of CMC applied, as a result of gas bubble coalescence.
A study on the kinetics of ozone decomposition in waters of different quality
Taki? Ljiljana M.,LaziMiodrag L.,Veljkovi? Vlada B.,Pejanovi? Sr?an M.
Hemijska Industrija , 2004, DOI: 10.2298/hemind0403118t
Abstract: The kinetics of ozone decomposition in waters of different quality, namely distilled water, tap water previously treated with ozone, tap water not treated with ozone and raw water from an accumulation lake, were studied in a batch stirred reactor at different temperatures (18-28°C). The dissolved ozone concentration was measured by the iodometric titration method. It was determined that an empirical kinetic equation of the form: dc(O3)/dt= k0 + k1c(O3) fitted the experimental data better than a first-order reaction rate equation. The apparent reaction rate constants in the case of ozone decomposition in distilled water were shown to be a function of temperature in accordance with the Arrhenius equation.
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