ritnms
Not a member yet
1551 research outputs found
Sort by
Limestone from deposit “Maljat”-Danilovgrad-potential raw material for obtaing fillers
No full textThe possibility of using limestone "Maljat"-Danilovgrad as filler was investigated. Micronization, granulo-composition, oil and water absorption and degree of whiteness were investigated, and chemical and thermal analyses (DT/TG) were performed. Physical-chemical properties of this limestone classify it among high quality carbonate raw materials. It can be used in following industry: paints and coatings: paper; rubber and PVC; glass; production of mineral fertilizers; foundring; sugar, metallurgy and in production of cattle feed. Due to content of POs, cannot be used for neutralization of acidic soils
Sugar Profile of Kernels as a Marker of Origin and Ripening Time of Peach (Prunus persicae L.)
No full textLarge amounts of fruit seeds, especially peach, are discarded annually in juice or conserve producing industries which is a potential waste of valuable resource and serious disposal problem. Regarding the fact that peach seeds can be obtained as a byproduct from processing companies their exploitation should be greater and, consequently more information of cultivars' kernels and their composition is required. A total of 25 samples of kernels from various peach germplasm (including commercial cultivars, perspective hybrids and vineyard peach accessions) differing in origin and ripening time were characterized by evaluation of their sugar composition. Twenty characteristic carbohydrates and sugar alcohols were determined and quantified using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC/PAD). Sucrose, glucose and fructose are the most important sugars in peach kernels similar to other representatives of the Rosaceae family. Also, high amounts of sugars in seeds of promising hybrids implies that through conventional breeding programs peach kernels with high sugar content can be obtained. In addition, by the means of several pattern recognition methods the variables that discriminate peach kernels arising from diverse germplasm and different stage of maturity were identified and successful models for further prediction were developed. Sugars such as ribose, trehalose, arabinose, galactitol, fructose, maltose, sorbitol, sucrose, iso-maltotriose were marked as most important for such discrimination
Distribution of fatty acids and alcohols in lignites, from the Smederevsko Pomoravlje field, Kostolac Basin – biogeochemical approach
No full textIn present study, both lipid classes, fatty acids and neutral lipids (e.g. alcohols) were
analysed in lignite samples in order to assess organic matter source and study biogeochemical and
diagenetic alteration processes.
The choice of polar compounds as useful biomarker indicators is based on several
considerations. As lipids, fatty acids are involved in energy storage, mobilization and in
membrane structure in all living organisms, while sterols have roles in membrane function and
hormonal regulation of metabolic processes primarily only in eucaryotes [1].
Pulverised lignites were extracted by an azeotrope mixture of dichloromethane and
methanol (88:12, v:v) using a Soxhlet’s apparatus. Extracts were dissolved in a mixture of nheptane:
dichloromethane (80:1, v:v) and asphaltenes were precipitated. The heptane-soluble
organic compounds (maltenes) were separated into saturated hydrocarbons, aromatic
hydrocarbons and NSO fraction (polar fraction, which contains nitrogen, sulphur, and oxygen
compounds) using column chromatography. Portions of NSO fractions were concentrated after
which the extracts were saponified with a mixture of 6% KOH in CH3OH and distilled water (3:1,
v:v) at 80°C (pH = 14). Fatty acids (FAs) and alcohols were analysed using a method modified
from Wakeham and Beier (1991) [1]. Alcohols and FAs were extracted 3 times with n-hexane at
pH 14 and pH 1, respectively using Na2SO4 for removal of the excess water. Prior to gas
chromatography-mass spectrometry analysis (GC-MS), the FAs and alcohol fractions were
derivatised with BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide, Fluka) for 1 h at 80°C to
form trimethylsilyl esters and ethers.
The obtained results are as follows: the fatty alcohols ranging from n-C12 to n-C28 alkanols
with a high abundance of long-chain fatty alcohols (n-C22 – C28) and only trace levels of shortchain
fatty alcohols (n-C12 – C18) indicating the main terrestrial input into the system. The
monounsaturated n-C18:1 fatty alcohol, which has been found in some species of diatoms,
Skeletonema costatum [2], was also present in samples. Steroidal alcohols, β-sitosterol (5-
cholesten-24β-ethyl-3β-ol), stigmastanol (24α-ethyl-5α-cholestan-3β-ol) and cholesterol, which
are the major sterols found in higher plants, are also found in small quantities. The presence of
kauran-13-ol is in accordance with the premise of terrestrial origin, given that abietane, pimarane,
kaurane and podocarpane skeletons are produced primarily by conifer vascular plants.
n-Alcanoic acids ranging from n-C6 – C30 with a notable predominance of even chainlenghts
are present in samples, having the maximum at hexadecanoic acid (C16:0). Saturated
compounds dominate in distribution but two unsaturated fatty acids were also found, 9-
octadecanoic (C18:1) and 9-hexadecanoic acid (C16:1). Apart from fatty acids, the polar fraction contains 4,8,12,16-tetramethylheptadecan-4-olide (a fragment of chlorophyll molecule with a side
phytol chain).
Typically high concentrations of long-chain (C22 –C30) n-alkanoic acids and n-alkanols (C12
– C28) with a sharp predominance of even homologues, certain hydroxyacids and dicarboxylic
acids, diterpenoid acids, long-chain saturated alkyl (wax) esters are characteristic components of
higher vascular plant cutin and suberin [3]. Biomarker analysis of aliphatic and aromatic fraction
of lignite coal is in concordance with the results obtained in the investigation of polar compounds,
confirming that in the case of Kostolac lignite, conifer terrestrial input was dominant source of
organic matter
Modification of dense TiO2 particles using polyethylene glycol template: Synthesis, characterization, and photocatalytic activity
No full textIn this study, an effort has been made to prepare TiO2 materials by sol–gel technique using polyethylene glycol (PEG) as pore directing agent. Different PEG amounts were used during samples preparation in order to investigate the change in intrinsic material properties. The photocatalytic activity of prepared catalysts was estimated by measuring the decomposition of arylazo pyridone dye. The optimum template amount was determined, resulting in catalyst with enhanced textural properties, optimal anatase/rutile ratio and hence improved photocatalytic properties. Specific surface area and anatase/rutile ratio were found to be the main contributing factors to the catalyst activity. A synergistic effect between anatase and rutile TiO2 has been observed, since the presence of relatively inactive rutile phase enhanced the photoactivity of mixed TiO2
Reactions of calcite in water in the presence of stearic acid
No full textU suspenziji kalcita i vode, čiji je pH 10,14, na granici kalcit/voda formirao se dvojni električni sloj. Njegova struktura, odnosno hidrofilne osobine minerala, su zavisile od koncentracije potencijal određujućih jona, Ca2+ i 2 CO 3 , pH sredine i adsorpcije molekula vode i jona (i molekula) formiranih u suspenziji kalcita usled njegove rastvorljivosti u alkalnoj sredini. Struktura tako formiranog dvojnog električnog sloja je uticala na interakciju minerala sa stearinskom kiselinom kao površinski aktivnom materijom. U prisustvu stearinske kiseline pH vrednost suspenzije je opadala do 8,72 zbog disocijacije stearinske kiseline u alkalnoj sredini i reakcije neutralizacije. Kao posledica disocijacije u suspenziji su se pored nedisosovanih molekula kiseline nalazili u određenoj koncentraciji i stearatni joni CH3(CH2)16COO-, (St-) koji su reagovali sa površinom minerala prevodeći je iz hidrofilne u hidrofobnu.In the suspension of water and calcite, with pH 10.14, on the border of calcite / water was formed a double electric layer. Its structure, or hydrophilic properties of minerals, depended on the concentration of potential determination ions, Ca2+ i 2 CO3 , pH of the environment, and the adsorption of water molecules and ions (and molecules), formed in a suspension of calcite as a result of its solubility in alkaline media. The structure of such a way formed electrical double layer, influenced on interaction of minerals with stearic acid as a surface of active substance. In the presence of stearic acid, the pH value of slurry decreased to 8.72 due to the dissociation of stearic acid in alkaline medium and reaction of neutralization. As the result of dissociation, in the suspension, besides the un-dissociated acid molecules, there were also stearine ions CH3(CH2)16COO-, (St-), which have reacted with the surface of minerals, transforming it from hydrophilic to hydrophobic
Obtaining new range of products from lithotamnium limestone 'Dobrilovići' deposit in the facility of the Department for Agriculture Loznica
No full textU radu su prikazani rezultati ispitivanja mogućnosti poboljšanja tehnološkog postupka valorizacije litotamnijskog krečnjaka ležišta 'Dobrilovići' - Loznica u cilju dobijanja novih asortimana proizvoda: za odsumporavanje dimnih gasova (ODG), kao dodatak stočnoj hrani i za kalcizaciju kiselih zemljišta. Rezultati su pokazali da se iz krečnjaka ovog lokaliteta mogu dobiti navedeni proizvodi koji po svojim karakteristikama ispunjavaju unapred propisane uslove kvaliteta. Na osnovu rezultata laboratorijskih ispitivanja autori su predložili tehnološku šemu po kojoj je moguća potpuna valorizacija krečnjaka iz ležišta 'Dobrilovići'. Adaptacijom postojeće tehnološke linije u firmi Zavod za poljoprivredu 'Loznica' doo (koja je vlasnik Rudnika krečnjaka 'Dobrilovići') mogu se dobiti još tri nova asortimana proizvoda.In this paper are presented the results of testing the possibilities of improving the technological process evaluation lithothamnium limestone deposits 'Dobrilovići' - Loznica in order to obtain a new range of products including: flue gas desulphurization (ODG), as feed additive and for liming acid soils. The results showed that the limestone from this deposit may be used for ODG as it meets the requirements of the required quality for use in these purposes. In fact, the raw materials meet the requirements for obtaining a powder (bulk) gypsum. Comparing the characteristics of the resulting range to be used as a feed additive ('fodder chalk') and the requirements to be met by this product, we can say: selective excavation and selecting a particular size class can get this range of products. The results of laboratory tests of briquettes obtained from lithothamnium limestone have shown that it is possible to obtain briquettes of a satisfactory quality. Values of parameters of the mechanical properties of briquettes increases with the share of bentonite as a binder in the samples. This increase in samples with mass proportion of binder to 5% is a linear growth, while for the samples containing more than 5% of binder that trend is minimal. Therefore, there is no need to produce briquettes with more than 5% of bentonite. Based on the results of laboratory tests, authors have proposed technological scheme by which is possible complete evaluation of the limestone deposit 'Dobrilovići'. With adaptation of existing technology line in the firm Department for Agriculture 'Loznica' Ltd. (which owns the mine limestone 'Dobrilovići') can be obtained three new product range
Biosorption of selected heavy metals by compost of myriophyllum spicatum
No full textU okviru ove doktorske disertacije ispitana je mogućnost primene invazivne korovske akvatične biljke Myriophyllum spicatum i komposta nastalog mikrobiološkom razgradnjom ove biljke, kao biosorbenata za uklanjanje odabranih teških metala iz vodenog rastvora. Biljka potiče iz Savskog jezera, Beograd, Srbija, a kompost sa deponije na koju se odlaže ova biljka, posle košenja. Za biosorpciju Pb(II) primenjeni su Myriophyllum spicatum i kompost, dok je za simultano uklanjanje odabranih teških metala, Pb(II), Cu(II), Cd(II), Ni(II) i Zn(II), iz vodenog rastvora korišćen kompost. Analiziran je proces biosorpcije u šaržnom sistemu, variran je veći broj parametara koj utiče na proces, izvršena je karakterizacija primenjenih biosorbenata, određeni su model ravnotežne izoterme i kinetički model, kojima se može najbolje opisati proces biosorpcije. Oba primenjena biosorbenta su prvi put okarakterisana u okviru ovih istraživanja, primenom većeg broja instrumentalnih tehnika, skenirajuća elektronska mikroskopija (SEM), energodisperzivni detektor X-zraka (EDS), Infracrvena spektroskopija sa Furijeovom transformacijom (FTIR), rendgenska difrakciona analiza (XRD), Termijska analiza (TGA/DTA). Određivanje koncentracije jona odabranih teških metala u vodenom rastvoru vršeno je primenom atomske apsorpcione spektroskopije (AAS). Najbolje slaganje eksperimentalnih vrednosti dobijenih ispitivanjem biosorpcije Pb(II) sa biljkom Myriophyllum spicatum i njenim kompostom bilo je sa Sipsovim modelom izoterme, a za oba materijala kinetika procesa je pratila model pseudo-drugog reda. Kapacitet biosorpcije Pb(II) bio je 0,287 mmol/g za kompost, a 0,234 mmol/g za biljku. Afinitet primenjenog biosorbenta prema ispitivanim metalima, opadao je u nizu: Pb(II)>Cu(II)>Zn(II)>Cd(II)>Ni(II). Najbolje slaganje eksperimentalno dobijenih vrednosti je bilo sa Sipsovim izotermnim modelom, za koji su vrednosti koeficijenta determinacije bile bliske 1. Kinetika procesa biosorpcije odabranih metala prati model...In this doctoral thesis, a possibility was examined to use the invasive aquatic weed plant Myriophyllum spicatum and its compost, generated from microbial degradation, as biosorbent for the removal of selected heavy metals from aqueous solution. The plant was harvested from the Sava Lake in Belgrade, Serbia, and the compost was collected from the open landfill where it is disposed. Myriophyllum spicatum and its compost were applied for Pb (II) biosorption, whereas for the simultaneous removal of, Pb(II), Cu(II), Cd(II), Ni(II) and Zn(II) from aqueous solution only compost was used. Biosorption proces in a batch system was analyzed by applying various batch processing parameters, which affect biosorption. Besides, the applied biosorbents were characterized and the equilibrium isotherms and kinetic models, which best describe the process of biosorption, were determined. In these investigations both applied biosorbents were characterized for the first time, with different instrumental techniques: Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction techniques (XRD), and thermal analysis. The analytical measurements of selected heavy metal ions concentration in aqueous solution were made by using Atomic absorption spectroscopy (AAS). The best fit of experimental data, obtained from the study of Pb(II) bosorption with Myriophyllum spicatum and its compost, was achieved when Sips isotherm model was used, whereby the process kinetics of both biosorbents followed a pseudo-secondorder kinetic model. Lead binding capacity of the compost was 0.287 mmol/g and of the plant 0.234 mmol/g. The affinity of the tested metals to the applied biosorbent was in descending order: Pb(II)>Cu(II)>Zn(II)>Cd(II)>Ni(II). The best fit of the experimentally obtained data was when Sips isotherm model was applied for which correlation coefficients were close to 1 (one). The kinetic studies indicated that the biosorption process of the metal ions followed well pseudo-second-order model, for which experimentally obtained..
Investigation of copper(i) sulphide leaching in oxidative hydrochloric acid solution
No full textPresent work is focused on the copper (I) sulphide leaching with sodium chloride in hydrochloric acid solution and with introduction of gaseous oxygen. Chemical reactions of leaching and their thermodynamic probabilities are predicted based on the literature data and products which were formed during the process and the overall leaching reaction was defined. The influence of temperature and time on the leaching degree of copper was experimentally determined. The quantity of dissolved copper increases with the increase of both investigated parameters. Elemental sulphur was formed as the main leaching product, precipitated at the particle surfaces and chloride ions have a role to disrupt the creation of this passive layer
Sustainable conversion of waste biomass using hydrothermal carbonization method
No full textHidrotermalna karbonizacija predstavlja postupak prevođenja vlažnog organskog materijala primenom povišene temperature i pritiska u hidročađ, proizvod sličan uglju. Dobijena hidročađ, u zavisnosti od prirode biomase, može biti upotrebljena kao zamena za fosilni ugalj, adsorbent različitih polutanata, dodatak za poboljšanje plodnosti zemljišta i dr. Ovaj rad pruža uvid u osnovne reakcione mehanizme, kao i uticaj procesnih parametara na dobijanje hidročađi. Takođe, istaknut je značaj i prednost postupka hidrotermalne karbonizacije otpadne biomase u odnosu na tradicionalne metode konverzije, kao i aktuelne primene dobijenih proizvoda.Hydrothermal carbonization represents a process for converting a wet organic material at elevated temperature and pressure in hydro char, coal-like product. The resulting hydro char, depending on the nature of biomass, can be used as a substitute for fossil coal, adsorbent of various pollutants, soil fertility supplement and others. This paper provides insight into the reaction mechanisms, as well as the influence of process parameters. It also highlighted the importance and advantage of the process of hydrothermal carbonization of biomass compared to traditional methods of conversion, as well as the actual implementation of the product
The impact of the production and use of polyvinyl chloride on the environment
No full textThe paper presents the most important characteristics of polyvinyl chloride (PVC), the types of
additives that are added to it to improve its properties (primarily mechanical) and its field of application. Particular
emphasis is placed to how the process of production of PVC and its application affect to the environment as well
as protection measures. Bearing in mind that the environment is more hazardous, is now a serious attention is paid
to recycling which can be used plastic waste and thereby also reduce environmental pollution.
Key words: polyvinyl chloride, environmental protection, recycling