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Effects of bentonite binder dosage on the properties of green limestone pellets
No full textThis paper presents the results of tests carried out to determine how the dosage of bentonite added as binder, affects the properties of green pellets made of the limestone fines that originate from Lithothamnium limestone processing. Bentonite was added to limestone in different mass fractions (1, 2.5, 5 and 10%), whereas all the other parameters of the pelletizing process remained constant. The aim of pelletizing was to consolidate limestone fines and form mechanically stable pellets, provided that all the other properties of limestone remain unchanged. The pellets formed in this way were analysed applying DTA/TG analysis and FTIR and SEM analyses. The results showed uniform distribution of bentonite in the pellets, demonstrated that the pellets are compact and there is no formation of new compounds. The pellets were tested for resistance to impact, compressive strength and abrasion resistance. Also disintegration tests were performed to determine the time required for the pellet to disintegrate completely in water. These mechanical properties are essential for transport, handling, storage and general use of pellets. The values of most of the parameters established for pellets with 5% bentonite, meet the standards required for use in agriculture for liming acid soils, however their application is limited because their impact resistance is unsatisfactory and the time required for their complete disintegration in water is extremely short. It should be noted that further increase of bentonite content (over 10%) will not improve the quality of green pellets. In view of the results obtained, it is necessary to introduce drying into the pelletizing process in order to bring the green pellets into solid state
Optimization of hydrothermal carbonization process of grape pomace and application of obtained hydrochar
No full textPredmet ovog rada je razvoj i optimizacija procesa hidrotermalne karbonizacije komine grožđa i ispitivanje mogućnosti upotrebe dobijene hidročađi kao biosorbenta olova iz vodenih rastvora.
U cilju optimizacije procesa, ispitan je uticaj reakcione temperature na transformaciju biomase, primenom različitih fizičko-hemijskih metoda karakterizacije dobijenih proizvoda karbonizacije na 180, 200 i 220 °C. Hidrotermalno indukovane strukturne promene u dobijenim hidročađima su okarakterisane ispitivanjem fizičko-hemijskog sastava, gorivnih karakteristika, kao i primenom termogravimetrijske, morfološke i spektroskopske analize, dok je u procesnim vodama određen sadržaj neorganskih elemenata, urađena spektroskopska analiza, analiza sadržaja pojedinačnih organskih komponenti i ispitan antioksidativni potencijal.
Dobijeni rezultati su pokazali da između dobijenih hidročađi postoje bitne strukturne razlike. Utvrđeno je da hidrotermalna degradacija hemiceluloze i celuloze, uzrokovana povećanjem temperature karbonizacije u najvećoj meri indukuje strukturne promene biomase tokom konverzije. Hidročađ koja poseduje značajan energetski potencijal, povećan sadržaj ugljenika i aromatičnost, kao i mogućnost re-adsorpcije pojedinih neorganskih elemenata dobijena je karbonizacijom na 220 °C. Takođe, povećanje reakcione temperature dovodi do porasta sadržaja fenola, polifenolnih jedinjenja i organskih kiselina u procesnim vodama, dok istovremeno uzrokuje opadanje antioksidativne aktivnosti, ukupnog sadržaja antocijana i organskih kiselina.
Mogućnost upotrebe hidročađi kao biosrbenta ispitana je sa aspekta adsorpcije Pb2+ jona iz vodenih rastvora. Kako bi se izabrao uzorak sa najboljim adsorpcionim kapacitetom izvršena su preliminarna ispitivanja procesa adsorpcije Pb2+ jona primenom hidročađi dobijenih na tri pomenute reakcione temperature. Dobijeni rezultati su ukazali da hidročađ dobijena na 220 °C pokazuje najbolji adsorpcioni kapacitet (27,8 mg/g), pa je stoga ova hidročađ izabrana za detaljna ispitivanja procesa adsorpcije Pb2+ jona. Hemijska modifikacija izabrane hidročađi primenom 2M rastvora kalijum-hidroksida korišćena je u cilju poboljšanja njenog adsorpcionog kapaciteta, pri čemu je postignut vrlo visok nivo uklanjanja od 137,0 mg Pb2+/g hidročađi.
Ispitivanjem uticaja radnih parametara (početna pH vrednost, masa adsorbensa, početna koncentracije jona metala, vreme kontakta i temperatura) na proces adsorpcije Pb2+ jona, upotrebom modifikovane i nemodifikovane hidročađi, utvrđene su njihove optimalne vrednosti za najefikasnije uklanjanje (pH 5,0; doza adsorbensa-0,5 g/L; inicijalna koncentracija Pb2+ jona-100 mg/L; reakciono vreme-60 min i sobna temperatura). Na dobijene eksperimentalne rezultate su primenjeni kinetički i izotermni modeli adsorpcije. Pokazano je da kinetički model pseudo-drugog reda najbolje opisuje kinetiku adsopcije Pb2+ jona na tretiranoj i netretiranoj hidročađi. Sipsov izotermni model daje najbolje slaganje sa rezultatima dobijenim za uklanjanje Pb2+ jona na aktiviranoj hidročađi. Dobijeni termodinamički parametri ukazuju da je vezivanje Pb2+ jona na površinu hidročađi spontan, egzoterman i favorizovan proces tokom kog raste neuređenost u sistemu čvrsto/tečno.
Na osnovu rezultata karakterizacije obe hidročađi pre i posle vezivanja Pb2+ jona (SEM-EDX, FTIR), rezultata kinetičke studije i ispitivanja mehanizma jonske izmene, utvrđeno je da se uklanjanje Pb2+ jona na aktiviranoj hidročađi odvija mehanizmima jonske izmene, površinske kompleksacije sa kiseoničnim funkcionalnim grupama (aktivacija povećava njihov sadržaj), i Pb2+-π interakcijom između d-elektrona metala i C=C grupe.
Rezultati dobijeni u ovom radu pokazuju da se karbonizacijom komine grožđa dobijaju hidročađi koje su perspektivni adsorbensi Pb2+ jona iz vodenih rastvora i potencijalni energenti, čiji se adsorpcioni kapacitet višestruko poboljšava alkalnom modifikacijom. Na osnovu svega navedenog se može zaključiti da je hidrotermalna karbonizacija veoma efikasna i ekološki održiva tehnologija za konverziju otpadne biomase, pri čemu se dobijaju proizvodi visoke upotrebne, ekološke i ekonomske vrednosti.The subject of this work was the development and optimization of hydrothermal carbonization of grape pomace and investigation of potential applications of the obtained hydrochar as biosorbent of lead from aqueous solutions.
In order to optimize the process, influence of the reaction temperature on transformation of biomass was investigated using different physico-chemical characterization methods of the products obtained at 180, 200 and 220 °C. Hydrothermal induced structural changes in hydrochars were elucidated by examination of physico-chemical composition, fuel characteristics, using thermogravimetric, morphological and spectroscopic analysis. IR spectroscopy, analysis of inorganic, as well as organic compounds, and antioxidant assays, were used for process waters characterization.
The results showed significant structural differences between the obtained products. It has been found that degradation of hemicellulose and cellulose, caused by temperature increase, governs the most significant structural changes in biomass during carbonization. The formation of hydrochar with significant energy potential, increased carbon content and the best adsorption ability, but decreased H/C ratio was achieved at 220 °C. Also, at higher temperature an increase in total phenolic and organic content in process waters was observed, while total antioxidative capacity, anthocyanin and organic acid content simultaneously decreased.
Application of the obtained hydrochars was tested via adsorption of Pb2+ ions from aqueous solution. In order to select material with the best adsorption ability, preliminary studies of Pb2+ sorption using hydrochars obtained at three aforementioned reaction temperatures were performed. Obtained results indicated that hydrochar produced at 220 °C exhibited the best adsorption potential (27.8 mg/g), and therefore this sample was chosen for further investigations of Pb2+ removal. Modification of selected product using 2M potassium-hydroxide solution was applied in order to improve its adsorption capacity, whereby the resulted capacity increased up to 137.0 mg Pb2+/g hydrochar.
Investigations of the effects of different adsorption parameters (initial pH value, adsorbent dose, initial metal concentration, contact time and temperature) using modified and unmodified hydrochar, defined their optimum values for the most effective Pb2+ removal (pH 5.0; dose=0.5 g/L; c=100 mg/L; t=60 min at room temperature). The kinetic study implied that the removal of Pb2+ ions on treated and untreated hydrochars follows pseudo-second order model. The Sips isotherm model gave the best fit with the experimental data obtained for Pb2+ sorption using activated hydrochar. Thermodynamic parameters reveled that binding of Pb2+ ions at hydrochar surface is spontaneous, exothermic and favored process during which disorder in the solid/liquid interface increases.
Characterization of hydrochars before and after Pb2+ removal (SEM-EDX, FTIR), kinetic studies and ion exchange experiments indicated that the removal of Pb2+ ions by activated hydrochar can be attributed to ion exchange mechanism, surface complexation with oxygen containing functional groups (KOH activation increases the oxygen functional groups content), Pb2 +-π interaction between the d-electron of metal and C=C in aromatics.
The results obtained in this study, indicated that hydrochars obtained by carbonization of grape pomace are perspective adsorbents of Pb2+ ions and potential fuels, while alkali treatment significantly improves hydrochar’s adsorption capacity. Based on the above it can be concluded that the hydrothermal carbonization is very efficient and environmentally sustainable technology for conversion of waste biomass into highly valuable products
Predicting the copper adsorption capacity on different zeolites
No full textU radu su prikazani rezultati ispitivanja uklanjanja jona bakra primenom tri prirodna zeolita sa različitih lokaliteta (Vranjska banja-VB, Igroš-I i Baia Mare-BM). U cilju karakterizacije zeolita, izvršena su ispitivanja elementarnog sastava, kao i rentgenska (XRDP) i termijska analiza (DTA/TG). Kapaciteti katjonske izmene (CEC) ispitivanih zeolita VB, I i BM iznose 150,1, 169,2 i 176,5 meq/100g. Maksimalni adsorpcioni kapaciteti bakra na VB, I i BM zeolitima iznose 7,75, 8,51, i 11,18 mg/g. Na osnovu ostvarenih rezultata, dobijena je matematička zavisnost koja dobro opisuje vezu između vrednosti CEC i adsorpcionog kapaciteta za bakar. Ova lineralna zavisnost je testirana primenom različitih eksperimentalnih rezultata. Primenom ove zavisnosti moguće je da se predvidi vrednost adsorpcionog kapaciteta bakra na različitim zeolitima poznavanjem njegove CEC vrednosti. .In this paper the ability of three natural zeolites from different localities (Vranjska banja-VB, Igroš-I and Baia Mare-BM deposits) to remove copper has been investigated. These three zeolites were subjected to the elementary analysis as well as XRDP and DTA/TG analysis due to complete characterization. Cation exchange capacity of VB, I and BM zeolites were 150.1, 169.2, and 176.5 meq/100g. The maximum adsorption capacity for the copper adsorption on VB, I and BM-zeolites were 7.75, 8.51, and 11.18 mg/g. Based on the obtained results the mathematical expression that describes correlation between the CEC and copper adsorption capacity has been developed. This linear dependance has been tested with the vast variety of experimental results. According to this expression it is possible to predict the copper adsorption capacity for different zeolites based only on their CEC value
Mechanism of adsorption of Cu2+ and Zn2+ on the corn silk (Zea mays L.)
No full textIn this study the novel biosorbent - raw corn silk (CS) was investigated for Cu2+ and Zn2+ removal from aqueous solutions. The physical and chemical properties of CS were determined by SEM - EDX and ATR - FTIR techniques. The SEM micrographs revealed that surface morphology of CS is suitable for metal adsorption, while FTIR analysis confirmed presence of various active groups (O-H, C-O, C-O C, C=C and amide II) which could interact with metal ions. The adsorption experiments were performed in batch system. Experimental data were fitted by pseudo - first order and pseudo - second order kinetic models as well as Langmuir and Freundlich isotherm models. Biosorption of the both metals follow pseudo second order kinetic model. The best fitting adsorption model is Langmuir model and the maximum biosorption capacities (q(max)) for Cu2+ and Zn2+ at 313 K and pH 5.0 were 15.35 mg g(-1) and 13.98 mg g(-1), respectively. The thermodynamic parameters such as Gibbs free energy change (Delta G), enthalpy change (Delta H) and entropy change (Delta S) were studied at different metal concentration and three temperatures. According to thermodynamic study, the biosorption process for both metals is feasible, endothermic and spontaneous. According to thermodynamic study, the biosorption process for both metals is feasible, endothermic and spontaneous. Ion - exchange is the dominant mechanism in adsorption of Cu2+ and Zn2+ on the CS with a certain degree of complexation. Desorption study was performed in three adsorption/desorption cycles with diluted nitric acid. Results show that after metal adsorption CS can be efficiently recovered and reused for new adsorption process. Obtained results indicated that corn silk could be used as efficient novel biosorbent for Cu2+ and Zn2+ removal from water samples
Removal of Lead and Cadmium Ions from Aqueous Solutions by Using Natural and Modified Zeolite
No full textIn this paper, immobilization of the natural (NZ) and Fe(III)-modified zeolite (FeZ) by Na-alginate was performed in order to improve their properties. Obtained results showed that alginate could be used for encapsulation of the natural and Fe(III)-modified zeolite in order to solve problem with water turbidity. Heavy metal cations (lead and cadmium) removal from water solutions by the natural and Fe(III)-modified zeolite with particle size: LT 0.043 mm (NZ and FeZ) and -0.8 + 0.6 mm (NZ1 and FeZ1) and NZ or FeZ after encapsulation with alginate (NZA and FeA) was preliminarily tested. Obtained results showed that adsorbed amounts of lead as well as cadmium increased after modification of the natural zeolite with Fe(III) ions but decreased with increasing of the particle size. Adsorbed amounts for lead were: 63, 57, 133 and 101 mg/g, while for cadmium: 11, 6, 19 and 14 for NZ, NZ1, FeZ and FeZ1, respectively. After immobilization of the NZ and FeZ with alginate, adsorbed amounts of lead were 101 and 134 mg/g and for cadmium 20 and 28 mg/g for NZA and FeA, respectively indicating that modification had no negative influence on adsorption. Besides positive effect on adsorption of heavy metal cations, easy modification with alginate could solve problems with water turbidity and separation, thus these materials may be suitable for column experiments. These results suggest that encapsulated samples could find practical application in purification of water contaminated with lead and cadmium
Investigation in order to defined the technological process of obtaining fillers for use in various industries on the basis of limestone 'Gigovići'-Ulcinj
No full textU ovom radu su predstavljeni rezultati ispitivanja mogućnosti korišćenja krečnjaka iz mesta Gigovići kod Ulcinja (Republika Crna Gora) kao punioca u različitim granama industrije. Ispitivani su metodi mikronizacije, granulometrijski sastav, stepen apsorpcije ulja i vode i stepen beline, a izvršena je i hemijska i termalna analiza (DT/TG). Fizičko-hemijske osobine ovog krečnjaka svrstavaju ga u karbonatne sirovine visokog kvaliteta sa relativno visokim sadržajem CaCO3, 98,16 %, i niskim sadržajem MgCO3, 1,53 %, i silikata (0,30 % SiO2). Njegov kvalitet zadovoljava standarde za korišćenje kalcijum-karbonata kao punioca u industriji boja i premaza, u papirnoj industriji, u proizvodnji gume i PVC-a, u industriji stakla, u proizvodnji veštačkog đubriva, u livarstvu i metalurgiji. Zbog niskog stepena beline krečnjak 'Gigovići' ne može da se koristi u farmaciji i kozmetičkoj industriji. Zbog visokog sadržaja MgO (0.73 %) i Fe (340 ppm), kao i visokog sadržaja teških metala, Cu (18 ppm), Ni (24 ppm) i Cd (9 ppm), krečnjak 'Gigovići' ne može da se koristi u proizvodnji stočne hrane i za neutralizaciju kiselih zemljišta.This paper presents results of investigations of the possibility of using 'Gigovići'-Ulcinj limestone (Republic Montenegro) as filler in various industry branches. Micronization methods, granulometric composition, oil and water absorption and degree of whiteness were investigated, and chemical and thermal analyses (DT/TG) were performed. Physico-chemical properties of this limestone classify it among high quality carbonate raw materials with relatively high CaCO3 content of 98.16 %, as well as low MgCO3 content of 1.53 % and low silicate content (SiO2 0.30 %). Its quality satisfies requirements of standards on using of calcium carbonate as filler in industry of paints and coatings; paper industry, rubber and PVC industry; glass industry; production of mineral fertilizers; foundry industry; sugar industry and metallurgy. Due to the low degree of whiteness (85.25 %) 'Gigovići' limestone cannot be used in pharmaceutical and cosmetics industry. Due to relatively high content of MgO (0.73 %) and Fe (340 ppm), as well as high content of heavy metals, Cu (18 ppm), Ni (24 ppm) and Cd (9 ppm), 'Gigovići' limestone cannot be used, in production of cattle feed and for neutralization of acidic soils
Allelic discrimination as a method for the estimation of social interaction
No full textAllelic discrimination gives the possibility to indicate a single nucleotide polymorphism (SNP) that may shed a clearer light on the correlation between genetic variation and its effect on the observed phenotype. Current method was used for identifying the oxytocin receptor gene polymorphism, which determines the degree of sociality.
Keywords: allelic discrimination, single nucleotide polymorphism, sociality, social interaction, polymerase chain reaction, genotyping, population genetics.
In the last few years, the method of allelic discrimination has been developed in molecular genetics. The assay detects variants of a single nucleic acid sequence. Single nucleotide polymorphisms (SNP) are one of the most common forms of human genetic variation [1]. SNPs are biallelic and occur about every 1,000 base pairs throughout the human genome. SNP are powerful markers for mapping genes that cause disease. Oxytocin is a hormone of the hypothalamus, which is closely related to human social behavior. Intranasal administration of oxytocin improves the ability to differentiate the mental state of others and increases attention to the eye region of the other human and improves the ability to understand their mental state [2]. Genetic variations in the gene of the oxytocin receptor (OXTR) are related to individual differences in responses to social cues. The SNPs are located in the non-coding regions of the oxytocin receptor gene. Most of the OXTR gene is the same for all people, but for different nucleotides, different versions of the gene may be present. The gene of this receptor exists in two versions: in a certain section of the DNA sequence there can exist either adenine (A-version) or guanine (G-version). It is believed that the presence of one or another variant of the gene corresponds to the psychological profile of a person: how resistant it is to stress and whether it is easy to be depressed. Allelic analysis of discrimination classifies unknown samples as homozygotes (samples having only allele 1 or allele 2) and heterozygotes (samples having both allele 1 and allele 2). Analysis of AD measures the change in fluorescence of dyes associated with probes. We analyzed the rs53576 single nucleotide polymorphism in the samples of buccal epithelium obtained from 20 people (age range 20–25 years). Their DNA was isolated using a standard protocol. Polymerase chain reaction (PCR) master mix was prepared by mixing PCR buffer, ddH2O, nucleotides (dNTPs), TaqMan probe (which contains two fluorescent dyes: ROX dye-specific for allele G and FAM dye-specific for allele A), two primers, enzyme Taq polymerase and DNA. Each DNA sample was analyzed in 3 repetitions together and the 4th one, without DNA, was the negative control. The results had shown that from 20 people, 9 of them are GG homozygotes, 1 is AA homozygote, and 10 people are G/A heterozygotes. The results obtained from RT-PCR were confirmed by incubating samples with the restriction enzyme (BamHI) and the number of fragments was determined using electrophoresis. In the case of GG homozygote – we had one fragment at 118 bp, AA homozygote – two fragments at 43bp and 75bp, and in the case of heterozygotes – 3 fragments at 43, 75 and 118bp. Our results lead to an important insight about the great efficiency of the designed system of genotyping SNP. Selected primers, probes, fluorophores and quenchers matched to the probes work well, allowing to definitely distinguish both homozygotes and heterozygotes from each other. As a result, this method is capable to detect associations between the genetic variation and its effect on the observed phenotype (in our case, the correlation between OXTR gene rs53576 polymorphism and the degree of social interaction).Thus, the method of allelic discrimination can be used both for population analysis and for the estimation of SNP in individuals
Ion conductive glass-ceramics in the system Li2O·Al2O3·GeO2·P2O5
No full textLithium based solid electrolytes are mainly useful for utilization in high energy density batteries, supercapacitors, sensors, displays and electrochemical devices. They generally crystallize in rhombohedral R3-c(167) space group related to open structures and the monovalent Li+ cation can easily migrate in lattice with low activation energy. These materials are usually obtained by powder sintering route and the crystallization of these glasses. The studies of crystallization of Li2O–Al2O3–GeO2–P2O5 glasses showed that one of dominant crystal phase precipitated in glass matrix is NASICON - type LiGe2(PO4)3 crystals. It was detected that this glass crystallizes by the volume crystallization mechanism. The enthalpy of crystallization ΔHcryst= -48.36 kJmol-1 was determined. The density of the crystalline phase was ρ=3.52 gcm-3 and molar volume Vm = 121.09 ·10-6 m3. The ionic conductivity of the test phase which be-longs to the solid solutions is about 6.2· 10−6 Scm-1 at room temperature.
It may be considered that the structure of this glass consists of GeO6 octahedra and PO4 tetrahedra. The basic unit of this glass consists of two GeO6 octahedra and PO4 tetrahedra corresponding to [Ge2(PO4)]. Each GeO6 octahedron is connected to three PO4 tetrahedra, each of which is linked to four GeO6 octahedra.
These units in turn are connected to form `ribbons` along the c-axis and the ribbons are joined together along the a-and b-axis by PO4 tetrahedra. This structure results in cavities where lithium ions reside and in bottlenecks in which they pass through
Aggregates Extraction In Serbia-Multiple Structural Breaks Analysis
No full textThis short letter investigates the dynamics of aggregates extraction in Serbia between 1973 and 2015. The change point analysis identifies 5 structural breaks in the intercept and linear time trend of aggregates extraction: 1980, 1989, 1995, 2003 and 2009. The estimated break dates correspond to the major business cycle turning points of the Serbian economy in the last 40 years. These findings suggest how aggregates extraction industry in Serbia was largely affected by the overall economic activity between 1973 and 2015
Magnetska separacija kao postupak za dobijanje različitih asortimana kvarcnog peska
No full textU radu su prikazani osnovni principi na kojima se zasniva magnetska separacija, njena primena, kao i podela minerala prema magnetskim svojstvima. Takođe, date su osnovne karakteristike kvarcnog peska, kao i parametri koji definišu njegov kvalitet za dalju upotrebu. Posebno su prikazani konkretni rezultati primene magnetske separacije u postupku čišćenja kvarcnog peska od magnetičnih nečistoća tipa Fe2O3. Magnetska separacija je urađena na uzorcima kvarcnog peska iz ležišta: „Rgotina“-Zaječar, „Bela Reka“-Bor, „Bijela Stijena“-Skočić i „Avala“-Kopovi Ub. Rezultati su pokazali da je moguće smanjiti sadržaj Fe2O3 u nemagnetičnoj frakciji u odnosu na sadržaj u ulazu. Tako je, na primer, sadržaj Fe2O3 u kvarcnom pesku iz ležišta „Rgotina“-Zaječar smanjen sa 0,086 % koliko iznosi u polaznom uzorku na 0,036 % koliko iznosi posle magnetske separacije