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Potentiometric determination of fluorides in real samples of honey from Hvar island : bachelor thesis
No full textFluoridi su spojevi koji se nalaze u malim koncentracijama u medu. Fluor je jedan od biogenih elemenata, ali u velikoj koncentraciji može izazvati zdravstvene probleme. U ovom radu je pomoću ionsko- selektivne elektrode, kao jednog od najpreciznijih alata za određivanje iona u otopinama, određivan udio fluorida u sedam različitih uzoraka meda s otoka Hvara. Dobivene koncentracije su se kretale od 68,67 do 324,40 μg fluorida po kilogramu meda, i nisu prelazile dozvoljene granice dnevnog unosa od 0,05 mg fluorida po kilogramu tjelesne mase kao što je određeno prema standardima Europske agencije za sigurnost hrane.Fluorides are compounds found in low concentrations in honey. Fluorine is one of the biogenic elements, but in high concentration it can cause health problems. In this work, the ion-selective electrode, one of the most precise instruments for the determination of ions in solutions, was used to determine the fluoride content in seven different honey samples from Hvar island. The concentrations determined ranged from 68.67 to 324.40 μg of fluoride per kilogram of honey and did not exceed the acceptable daily intake level of 0.05 mg of fluoride per kilogram of body weight established by the European Food Safety Agency
Influence of process conditions on metal sorption on peanut shell : bachelor thesis
No full textRavnoteža procesa sorpcije bakrovih(II) iona na usitnjenoj ljusci kikirikija veličinske klase čestica promjera od 200 do 250 µm ispitivana je u ovom radu. Eksperimenti su provedeni u šaržnim reaktorima korištenjem suspenzije pripremljene od 1 grama usitnjene ljuske kikirikija i otopina bakrovog(II) klorida različitih početnih koncentracija. Suspenzije su miješane u vodenoj kupelji pri stalnoj temperaturi od 30 °C i brzini od 150 okr./min. Tijekom 72 sata, svaka 24 sata, suspenzije su uzorkovane kako bi se ispitalo je li uspostavljena ravnoteža. Uzorci su filtrirani i analizirani UV/VIS spektrofotometrom. Dobiveni eksperimentalni podatci analizirani su Jovanovićevom, Freundlichovom, Hillovom i Redlich-Petersonovom adsorpcijskom izotermom. Usporedbom eksperimentalnih podataka i odabranih adsorpcijskih izotermi te izračunatih RMSE vrijednosti zaključeno je kako se Hillova izoterma najbolje poklapa s dobivenim eksperimentalnim podatcima. Zaključeno je i da se učinkovitost sorpcije smanjuje kako raste početna koncentracija otopine bakrovih(II) iona. Ravnotežno stanje, u svim ispitivanim sustavima, postignuto je nakon 72 sata. Dobiveno je kako za otopine početnih koncentracija većih od 6,496 mmol/dm 3 ravnotežna količina bakrovih(II) iona sorbiranih na usitnjenoj ljusci kikirikija iznosi oko 0,21 mmol/g i da ista ne ovisi o početnoj koncentraciji otopine.In this work, the equilibrium of the sorption process of copper(II) ions on crushed peanut shell of the size class of particles with a diameter of 200 to 250 µm was investigated. The experiments were carried out in batch reactors, using a suspension prepared from 1 g of crushed peanut shell and copper(II)chloride solutions of different initial concentrations. The suspensions were mixed in a water bath at a constant temperature of 30 °C and a speed of 150 rpm. Samples were taken from the suspensions every 24 hours for 72 hours to determine if equilibrium had been reached. The samples were filtered and analysed with a UV/VIS spectrophotometer. The experimental data obtained were analysed using the Jovanović, Freundlich, Hill and Redlich-Peterson adsorption isotherms. By comparing the experimental data with the selected adsorption isotherms and the calculated RMSE values, it was found that the Hill isotherm best fits the obtained experimental data. It was also found that the sorption efficiency decreases with increasing initial concentration of the copper(II) ion solution. The equilibrium state was reached after 72 hours in all systems tested. It was found that for solutions with initial concentrations greater than 6.496 mmol/dm 3 , the equilibrium amount of copper(II) ions sorbed onto the crushed peanut shell was about 0.21 mmol/g and did not depend on the initial concentration of the solution
Influence of particle size and shape on unhindered settling velocity : bachelor thesis
No full textU ovom radu određivana je brzina neometanog taloženja sferičnih čestica različitih veličina, ali i onih nepravilnog oblika, tzv. nesferičnih čestica. Brzine taloženja određivane su eksperimentalno u koloni za određivanje brzine taloženja vlastite izvedbe, kao i korištenjem teorijskih izraza, odnosno primjenom C D – Re dijagrama. Dobiveni rezultati ukazuju da povećanje veličine sferičnih i nesferičnih čestica, kao i povećanje razlike gustoća između čestica i fluida, značajno utječe na brzinu neometanog taloženja. Analizirano taloženje odvijalo se u prijelaznom hidrodinamičkom području optjecanja, zbog čega nije bio primjenjiv Stokesov zakon za određivanje brzina taloženja. Stoga se kao neminovnost nametnula uporaba C D – Re dijagrama. Podaci o brzinama taloženja i veličini čestica dobiveni primjenom C D – Re dijagrama pokazuju vrlo dobro slaganje s eksperimentalno dobivenim rezultatima.In this bachelor thesis, the unhindered settling velocity for spherical particles of different sizes, as well as for those of irregular shapes, the so-called non-spherical particles, was determined. The settling velocities were determined experimentally in the column for determining the settling velocity of our own performance, as well as using theoretical expressions, i.e. using C D - Re diagram. The obtained results indicate that the increase in the size of spherical and non-spherical particles, as well as the increase in the density difference between particles and fluid, significantly affects unhindered settling velocity. The analyzed settling took place in the transient hydrodynamic area of circulation, which is why Stokes' law was not aplicable for settling velocity determination. Therefore, the use of C D - Re diagram was inevitable. Data on the settling velocities and particles size obtained using C D - Re diagram show very good agreement with the experimentally obtained results
The influence of calcium alginate on the structure and thermal properties of poly(ethylene-oxide) : bachelor thesis
No full textModifikacija svojstava poli(etilen-oksida) (PEO) provedena je dodatkom kalcijevog alginata (CaAlg) s ciljem smanjena stupnja kristalnosti PEO-a, a u svrhu primjene mješavine kao krutog polimernog elektrolita. Uspješno su pripravljene mješavine PEO/CaAlg pomoću ekstrudera s dvopužnim kontrarotirajućim vijcima. Primjenom infracrvene spektroskopije s Fourierovom transformacijom (FTIR) nisu potvrđene značajnije interakcije između PEO-a i CaAlg-a. Diferencijalna pretražna kalorimetrija (DSC) je primijenjena u svrhu istraživanja utjecaja CaAlg-a na toplinska svojstva i kristalnost PEO-a. Uočava se djelomična mješljivost mješavine PEO/CaAlg. Udio kristalne faze PEO-a kod svih mješavina nije značajno promijenjen. Toplinska postojanost mješavina istraživana je primjenom neizotermne termogravimetrije (TG). Polimerne mješavine PEO/CaAlg razgrađuju se u tri stupnja razgradnje. Dodatak i povećanje udjela CaAlg-a pogoršava toplinsku postojanost ispitivanih mješavina. Najveći potencijal za pripravu SPE s kalcijevim solima ima mješavina 80PEO/20CaAlg.The modification of properties of poly(ethylene oxide) (PEO) was performed by adding calcium alginate (CaAlg) with the aim of reducing its crystallinity and therefore improving its conductivity. All blends were successfully prepared with a counter rotating twin screw extruder. By applying Fourier-transform infrared spectroscopy (FTIR) there were no significant interactions confirmed between PEO and CaAlg. Differential scanning calorimetry (DSC) has been applied to investigate the influence of CaAlg on thermal properties and crystallinity of PEO. Partial miscibility of PEO/CaAlg blend occurs. The degree of crystallinity of PEO is still very large in every blend. Thermal stability of blends was investigated using non-isothermal thermogravimetry (TG). PEO/CaAlg polymer blends degrade through three degradation degrees. Addition and increase of CaAlg worsens thermal stability of examined blends. The biggest potential for preparation of SPE with calcium salts has the 80PEO/20CaAlg blend
Isolation and quantization of glucosinolates from Nasturtium officnale and Iberis umbellata plants : master thesis
No full textGlukozinolati su sekundarni metaboliti identificirani u preko 16 različitih biljnih porodica, a najznačajnija je porodica Brassicaceae u koju se ubrajaju dobro poznate biljke iz svakodnevne prehrane. Glukozinolati su fiziološki neaktivni i kemijski stabilni i tek njihovom razgradnjom djelovanjem enzima mirozinaze dolazi do oslobađanja raznovrsnih spojeva. Smatraju se fitokemikalijama s potencijalom prevencije različitih bolesti u ljudskom organizmu. U ovom diplomskom radu izolirani su i analizirani glukozinolati iz odabranih dijelova biljaka Nasturtium officinale i Iberis umbellata. Glukozinolati su identificirani UHPLC-DAD-MS/MS analizom desulfatiranih glukozinolata. Isti su kvantificirani u različitim dijelovima biljke prema službenoj ISO 9167-1 metodi koja se zasiva na HPLC analizi desulfoglukozinolata. Izolacija glukozinolata iz navedenih biljnih materijala je napravljena metodom ekstrakcije glukozinolata uz desulfataciju. Kod Nasturtium officinale izolirani su i kvantizirani sljedeći glukozinolati: metilsulfinilalkilni glukozinolati i to glukohesperin, 7-(metilsulfinil)heptil-glukozinolat, glukohirsutin, zatim glukonasturcin koji je aril-alkilni glukozinolat te glukobrasicin i 4-metoksiglukobrasicin koji spadaju u skupinu indolnih glukozinolata. U sjemenu Iberis umbellata kvantizirani su spojevi: glukoiberin, sinigrin, glukonapin, glukoibervirin i glukotropeolin, dok su iz tog sjemena uzgojenoj biljci Iberis umbellata identificirani sljedeći spojevi: glukoiberin, sinigrin, glukoibervirin, glukotropeolin i 4-metoksiglukobrasicin. U uzgojenoj biljci Iberis umbellata nije prisutan glukonapin kojeg nalazimo u sjemenu, ali je identificiran 4-metoksiglukobrasicin koji nije pronađen u sjemenu.Glucosinolates are secondary metabolites identified in over 16 different plant families, among which the most important is Brassicaceae family, which includes well known plants of everyday nutrition. Glucosinolates are physiologically inert and chemically stable upon activation of the enzyme myrosinase leads to the degradation of glucosinolates and formation of various compounds. They are considered as phytochemicals which have potential to protect the human body form various diseases. In this diploma thesis, glucosinolates from selected parts of Nasturtium officinale and Iberis umbellata plants were isolated and analysed. Glucosinolates were identified by UHPLC-DAD-MS/MS analyzing desulfated glucosinolates. The same were quantified in different plant parts according to the official ISO 9167-1 method based on the HPLC analysis of desulphoglucosinolates. Isolation of glucosinolates from used plant material was performed using the method of glucosinolate extraction by desulphation. The following glucosinolates were isolated and quantizated from Nasturtium officinale: methylsulfinylalkyl glucosinolates i.e. glucohesperin, 7-(methylsulfinyl)heptylglucosinolate, glucohirsutin, than gluconasturcin which is arylalkyl glucosinolate, and glucobrasicin and 4-methoxyglucobrasicin which belong indole glucosinolates group. The following compounds were quantizated in Iberis umbellata seeds: glucoiberin, sinigrin, gluconapin, glucoibervirin and glucotropeolin. While from Iberis umbellata plant cultivated using the same seed following compounds were indentified: glucoiberin, sinigrin, glucoibervirin, glucotropeolin and 4-methoxyglucobrasicin. Although present in seeds, gluconapin was not found in cultivated Iberis umbellata plant; on the other hand 4-methoxyglucobrasicin was identified in the plant whie beeing absent in the seeds
Influence of temperature on the value of diffusion coefficient of sodium chloride solution : bachelor thesis
No full textS obzirom na hidrodinamičke uvjete u nekom sustavu prijenos tvari se može odvijati molekularnim ili vrtložnim mehanizmom. U ovom radu izvršena je analiza molekularnog mehanizma prijenosa tvari tj. sagledao se utjecaj temperature na vrijednosti koeficijenta difuzije otopine natrijeva klorida koja difundira u demineraliziranoj vodi. Vrijednosti koeficijenta difuzije određene su eksperimentalno uporabom aparature vlastite izvedbe te analitički koristeći Wilke-Changov izraz. Dobiveni rezultati ukazuju da porastom temperature sustava vrijednosti koeficijenta difuzije rastu. Identičan trend je dobiven eksperimentalnim mjerenjima, ali i primjenom navedenog analitičkog izraza. Uspoređujući dobivene numeričke vrijednosti koeficijenata difuzije određene pri identičnim temperaturama uočavaju se određena odstupanja. Razlozi tih odstupanja mogu biti eksperimentalne prirode, ali i u odabiru neodgovarajućeg analitičkog izraza. Kao glavni uzroci eksperimentalnih pogrešaka mogu se navesti temperaturne varijacije sustava tijekom provedbe eksperimenta, neodgovarajuća izmiješanost otopine u posudi, pojava zračnih mjehurića u difuzijskoj ćeliji, način provedbe konduktometrijskih mjerenja te eventualne pogreške pri samoj pripravi otopina. Navedene eksperimentalne pogreške potrebno je u daljnjem radu svesti na najmanju moguću mjeru, dok kod teorijskog određivanja koeficijenta difuzije je potrebno iznaći izraz koji detaljnije uzima u obzir fizikalno-kemijska svojstva analiziranog sustava.Depending on the hydrodynamic conditions within the system, the mass transfer can occur by a molecular or convection mechanism. In this work focus has been on the analysis of the molecular diffusion mechanism. The impact of temperature on the value of the diffusion coefficient of sodium chloride solution which diffuses in demineralized water was studied in detail. The values of the diffusion coefficient were determined experimentally using an experimental set up of own design and analytically using the Wilke- Chang equation. The obtained results show that the diffusion coefficient increases with increasing system temperature. An identical trend was obtained by experimental measurements and the application of the above analytical expression. Experimentally and theoretically determined numerical values of the diffusion coefficient do not display an adequate agreement. The reasons for these deviations could be of experimental nature, but also in the choice of an inappropriate analytical expression. The main causes of experimental errors could be temperature variations of the system during the experimental procedure, poor mixing of the solution in the vessel, the appearance of air bubbles in the diffusion cell, inadequate conductometric measurements and possible errors in the preparation of solutions. These experimental errors should be reduced to a minimum in further work, while in the theoretical determination of the diffusion coefficient it is necessary to find an expression that takes into account in more detail the physicochemical properties of the analyzed solutions
Thermal properties of poly(ethylene oxide)/sodium alginate films after treatment with Ca2+ ions : diploma thesis
No full textSažetak: Referentni film poli(etilen oksid)/natrijev alginat mješavine s 80 mas.% poli(etilen oksida) i 20 mas.% natrijevog alginata (80%PEO/20%NaAlg) pripremljen je metodom lijevanja filma iz otopine. Umrežavanje natrijevog alginata u filmu mješavine s Ca 2+ ionima provedeno je s 1, 2,5, 5, 7,5 i 10% w/v metanolne otopine CaCl 2 tijekom 10, 30, 60 i 180 minuta izlaganja, nakon čega su filmovi isprani dva puta. Strukturna promjena NaAlg istražena je primjenom infracrvene spektroskopije s Fourierovom transformacijom (FT-IR) prema kojoj je umrežavanje s Ca 2+ ionima uspješno provedeno. Diferencijalna pretražna kalorimetrija (DSC) primijenjena je za ispitivanje utjecaja umrežavanja na toplinska svojstva i kristalnost PEO u filmovima mješavina. Umrežavanje s Ca 2+ ionima ima značajan utjecaj na kristalizaciju PEO i kod određenih uvjeta se smanjuje količina kristalne faze PEO u tretiranim filmovima mješavina. Toplinska stabilnost tretiranih filmova mješavina ispitivana je uporabom neizotermne termogravimetrije (TG). Određeni uvjeti umrežavanja doveli su do poboljšanja toplinske stabilnosti alginata u filmu mješavine i usporavanja razgradnje PEO. Sve provedene analize potvrdile su uspješno umrežavanje s Ca 2+ ionima. U budućim istraživanjima umrežavanje NaAlg s Ca 2+ ionima u filmu 80%PEO/20%NaAlg mješavine provodit će se samo s najvećom koncentracijom metanolne otopine CaCl 2 (10% w/v) i uz najduže vrijeme izlaganja otopini (180 min). Navedeni uvjeti polučili su najbolje rezultate te dobiveni film pri tim uvjetima ima najveći potencijal kao čvrsti polimerni elektrolit.The referent film of poly(ethylene oxide)/sodium alginate blend with 80 wt% of poly(ethylene oxide) and 20 wt% of sodium alginate (80%PEO/20%NaAlg) was prepared by solution casting method. The cross-linkage of sodium alginate in the blend film with Ca 2+ ions was conducted with 1, 2.5, 5, 7.5 and 10% w/v CaCl 2 methanol solution during 10, 30, 60 and 180 minutes exposure time after which the films were rinse twice. The structural change of NaAlg was investigated by Fourier transform infrared spectroscopy (FT-IR) according to which the cross-linkage with Ca 2+ ions was successful. Differential scanning calorimetry (DSC) has been applied to investigate the influence of cross-linkage treatment to the thermal properties and crystallinity of PEO in the films. The cross-linkage with Ca 2+ ions has significant effect on the crystallization process of PEO and under the specific conditions it lowers the amount of crystalline phase of PEO in the treated films. Thermal stability of the treated films was investigated using non-isothermal thermogravimetry (TG). The specific conditions make the degradation of alginate in the treated films more stable while at the same time they decrease the rate of the degradation of PEO. All analysis confirmed the successful cross-linkage with Ca 2+ ions. In the future investigations cross-linkage of NaAlg with Ca 2+ ions in 80%PEO/20%NaAlg film will be carried out only at the highest concentration of CaCl 2 methanol solution (10% w/v) and the highest exposure time to the solution (180 min). These conditions showed the best results and obtained film under these conditions has the greatest potential to be a solid polymer electrolyte
Computer-based simulation of corrosion of mild steel : diploma thesis
No full textU ovom radu simuliran je korozijski proces niskougljičnog čelika u cjevovodnom sustavu za transport nafte pri različitim procesnim parametrima. Za simulaciju je korištena programska podrška za predviđanje korozije FREECORP TM 2.0. Glavne značajke modela su: predviđanje brzine korozije uzrokovane CO 2 , H 2 S, organskim kiselinama, tj. CH 3 COOH, i/ili O 2 , simulacija rasta sloja željezova(II) karbonata i željezova(II) sulfida te kvantitativno određivanje doprinosa različitih korozijskih vrsta korozijskom procesu i identifikacija dominantne korozijske vrste. Glavni parametri ispitivanog sustava su temperatura, vrijeme, tlak, promjer cijevi i brzina strujanja vodene otopine. Parametri vodene otopine su pH-vrijednost, koncentracija korozivnih vrsta kao što su ugljikov dioksid, sumporovodik, octena kiselina, kisik i koncentracija Fe 2+ iona. Na temelju određenih ulaznih parametara, izračunata je brzina opće korozije i određen doprinos korozivnih vrsta ukupnoj brzini.This paper aims to study the corrosion process of mild steel in a pipeline system for oil transport as different process parameters are simulated. FREECORP TM 2.0 corrosion prediction software was used for the simulation. The main features of this model include: prediction of corrosion rate caused by CO 2 , H 2 S, organic acids, i.e. CH 3 COOH, and/or O 2 , simulation of iron carbonate film and iron sulphide film growth and identification of major corrosive species by quantifying respective contributions from various species. The main parameters are temperature, time, pressure, pipe diameter and liquid velocity. The parameters of the aqueous solution are pH and concentration of corrosive species such as carbon dioxide, hydrogen sulphide, acetic acid, oxygen and concentration of Fe 2+ ions. Based on specific input parameters, the uniform corrosion rate was calculated and the contribution of corrosive species to overall corrosion rate was determined
Methods of synthesis and characterization of ZnO nanostructures for biomedical application : bachelor thesis
No full textNanomaterijali se sve više primjenjuju u biomedicini, a među njima se posebno ističe cinkov oksid, zbog svojih kemijskih, fizikalnih i mehaničkih svojstava, kao i zbog zanimljivih struktura na mikro- i nanoskali različite funkcionalnosti. One pokazuju terapeutsko djelovanje kod liječenja raka, dijabetesa, mikrobnih infekcija i rana, a primjenjive su i u dijagnostici oslikavanjem te kao senzori. Morfologije i svojstva tih struktura, a time i njihova funkcionalnost, ovise o tehnikama sinteze. Za kontrolu funkcionalnosti nadalje je potrebna mogućnost precizne morfološke karakterizacije. U radu je dan pregled metoda sinteze i morfološke karakterizacije ZnO, s naglaskom na opisu trodimenzionalnih poroznih hijerarhijskih ZnO struktura. Dan je primjer pripreme i karakterizacije takve strukture, putem elektronske mikroskopije i simultanih GIXRD/GISAXS mjerenja.Nanomaterials are increasingly used in biomedicine, and zinc oxide stands out among them, due to its chemical, physical and mechanical properties, as well as due to interesting structures on micro- and nanoscales of different functionalities. They show a therapeutic effect in the treatment of cancer, diabetes, microbial infections and wounds and are applicable in diagnostics by imaging and as sensors. The morphologies and properties of these structures, and thus their functionality, depend on the synthesis techniques. The possibility of precise morphological characterization is further required to control functionality. The paper gives an overview of the methods of synthesis and morphological characterization of ZnO, with an emphasis on the description of three - dimensional porous hierarchical ZnO structures. An example is given of the preparation and characterization of such a structure, by electron microscopy and simultaneous GIXRD / GISAXS measurements
Volumetric properties of solutions of 1-methylimidazolium acetate ionic liquid in water, dimethyl sulfoxide, N,N-dimethylacetamide and N,N-dimethylformamide at different temperatures : master thesis
No full textU ovom radu sintetizirana je ionska tekućina 1-metilimidazolijev acetat, MimAc, reakcijom 1- metilimidazoliuma i octene kiseline. Potom su mjerene gustoće otopina MimAc u vodi, DMSO, DMA i DMF pri različitim molalitetima i temperaturama. Iz dobivenih gustoća, izračunata su razna volumetrijska svojstva: prividni molarni volumen, parcijalni molarni volumen otapala, parcijalni molarni volumen MimAc, granični prividni molarni volumen, granična prividna molarna ekspanzibilnost i Hepplerov koeficijent. Valjanost Massonove jednadžbe je provjerena te je utvrđena linerana ovisnost prividnog molarnog volumena o koncentraciji pri svim radnim temperaturama. Iz te su ovisnosti određeni veoma važni volumetrijski parametri: granični prividni molarni volumen i Massonov interakcijski koeficijent. Konačno, raspravljena su svojstva promoviranja strukture s pozitivnim koeficijentom (eng. „structure-maker“) ili rušenja strukture s negativnim koeficijentom (eng. „structure-breaker“) ispitivane ionske tekućine u raznim otapalima. Prema vrijednostima Hepplerovog koeficijenta, MimAc u DMF, DMA i DMSO se može opisati kao „structure-breaker“, a u vodi kao granični s koeficijentom blizu nule (eng. „borderline“).Ionic liquid, MimAc was obtained in our laboratory from 1-methylimidazole and acetic acid. The densities of the solutions of MimAc in water, DMSO, DMA and DMF were measured at different molalities and temperatures. The obtained density data calculates volumetric properties (apparent molar volume, standard partial molar volumes, apparent molar volume at infinite dilution, limiting apparent molar expansibilities and Heppler's coefficient). The validity of Masson's equation was checked and applied to describe the evident molar volume dependence on molarity. The apparent molar volume at infinite dilution and interaction coefficient were obtained from this dependence at each temperature. Finally, structure-maker or structure-breaker properties of investigated IL in various solvents are discussed. According to the values of Heppler’s coefficients, MimAc IL, in DMF, DMA, and DMSO could be described as structure-breakers. Values of the Heppler’s coefficient for MimAc in water medium is around zero, so this investigated IL is classified as the borderline