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Sorption of copper on NaX and Saccharomyces cerevisiae yeast incorporated in alginate : diploma thesis
No full textU ovom radu ispitivala se ravnoteža sorpcije bakrovih iona na zeolitu NaX čestica srednjeg promjera manjeg od 40 µm te suhom pekarskom kvascu Saccharomyces cerevisiae čestica srednjeg promjera manjeg od 160 µm ugrađenima u alginat. Eksperiment se proveo korištenjem suspenzija zeolita NaX, odnosno suhog pekarskog kvasca Saccharomyces cerevisiae imobiliziranih u alginatu i otopine bakrovog(II) klorida dihidrata različitih početnih koncentracija. Pripremljene suspenzije smještene su u vodenu kupelj s trešnjom pri izotermnim uvjetima (T = 27 °C) i brzini od 200 okr./min. Suspenzije su uzorkovane, filtrirane, a filtrati analizirani UV/Vis spektrofotometrom u određenim vremenskim intervalima tijekom 72 sata kako bi se pratilo uspostavljanje ravnoteže u ispitivanom sustavu. Dobiveni eksperimentalni podatci analizirani su Freundlichovom, Langmuirovom, Redlich-Petersonovom i Sipsovom izotermom. Grafičko slaganje dobivenih eksperimentalnih podataka s adsorpcijskim izotermama te vrijednosti izračunatog RMSE i hi-kvadrat testa pokazali su da Langmuirova izoterma najbolje opisuje proces sorpcije bakrovih iona na zeolitu NaX ugrađenom u alginat i proces sorpcije bakrovih iona na pekarskom kvascu Saccharomyces cerevisiae ugrađenima u alginat. Učinkovitost sorpcije smanjuje se porastom početne koncentracije otopine bakrovog(II) klorida dihidrata, a ravnotežno stanje u svim suspenzijama postignuto je nakon 24 sata. Količina bakrovih iona vezanih u ravnoteži ovisna je o početnim koncentracijama otopina; uočava se kako porast početne koncentracije otopine bakrovih iona uglavnom dovodi do rasta količine bakrovih iona vezanih na zeolitu NaX i pekarskom kvascu Saccharomyces cerevisiae ugrađenima u alginat.In this thesis, the equilibrium of copper ion sorption on zeolite NaX, with a mean particles diameter of less than 40 µm, and on dry baker’s yeast Saccharomyces cerevisiae with a mean particles diameter of less than 160 µm incorporated in alginate was investigated. The experiments were carried out using suspension of zeolite NaX, respectively dry baker's yeast Saccharomyces cerevisiae incorporated in alginate and copper(II) chloride dihydrate solution with different initial concentrations. The prepared suspensions were placed in a water bath shaker under isothermal conditions (T = 27 °C) and at a speed of 200 rpm. The suspensions were sampled, filtered, and filtrates were analysed at specific time intervals over a period of 72 hours using a UV/Vis spectrophotometer to verify the establishment of equilibrium in the system under investigation. The experimental data obtained were analysed using the Freundlich, Langmuir, Redlich-Peterson and Sips isotherms. The graphical fit of the experimental data with the adsorption isotherms and the calculated RMSE and chi-square test parameters showed that the Langmuir isotherm best describes the sorption process of copper ions on NaX zeolite and the sorption process of copper ions on Saccharomyces cerevisiae baker's yeast incorporated in alginate. The sorption efficiency decreases with the increase of the initial concentration of the copper(II) chloride dihydrate solution, the equilibrium state was reached in all suspensions after 24 hours. The amount of copper ions retained at equilibrium depends on the initial concentrations of the solutions. It can be observed that an increase in the initial concentration of the copper ion solution mainly leads to an increase in the amount of copper ions sorbed on zeolite NaX and to the baker's yeast Saccharomyces cerevisiae incorporated in alginate
Impact of SBT impeller diameter on kinetics of copper sorption on zeolite : diploma thesis
No full textIspitivan je utjecaj promjera turbinskog miješala s ravnim lopaticama, tzv. SBT miješala na sorpciju iona bakra na sintetskom zeolitu NaX. Kinetički eksperimenti su provedeni u kotlastom reaktoru nestandardnih dimenzija uz miješanje suspenzije pri konstantnoj temperaturi u trajanju od 30 minuta. Analiza dobivenih kinetičkih podataka provedena je primjenom Blanchardovog i Weber-Morrisovog modela. Dobro slaganje eksperimentalnih kinetičkih podataka s Blanchardovim modelom i neslaganje s Weber-Morrisovim modelom ukazuje na to da ispitivana reakcija prati kinetiku reakcije drugog reda i da difuzijski procesi ne utječu na ukupnu brzinu ispitivanog procesa.The influence of the diameter of the turbine impeller with flat blades, the so-called SBT impeller for the sorption of copper ions on synthetic zeolite NaX was examined. The kinetic experiments were carried out in a batch reactor with non-standard dimensions while stirring of the suspension at a constant temperature for 30 minutes. The kinetic data obtained were analysed using the Blanchard and Weber-Morris models. The good agreement of the experimental kinetic data with the Blanchard model and the disagreement with the Weber-Morris model indicate that the investigated reaction follows second-order reaction kinetics and that diffusion processes do not affect the overall rate of the investigated process
Effect of grinding techniques on the microstructure and powder characterization of purslane (Portulaca oleracea L.) and phenolic content in water extract before and after in vitro simulated digestion : bachelor thesis
No full textTušt (Portulaca oleracea L.) je biljka prepoznata kao vrijedan izvor hranjivih tvari i bioaktivnih spojeva, poput omega-3 masnih kiselina, antioksidansa, vitamina i minerala. Unatoč tradicionalnoj percepciji kao korova, tušt ima visoku nutritivnu vrijednost i široku primjenu u prehrani. Ovaj rad istražuje proizvodnju praha od liofiliziranog tušta koji zadržava hranjive tvari te se koristi kao dodatak prehrani. Fokus je na ispitivanju razlika u mikrostrukturi prahova dobivenih različitim tehnikama mljevenja (mlin s noževima, kuglični mlin, planetarni mlin), analizi raspodjele veličina čestica, nasipne gustoće i parametara boje te udjela i sastava fenola prije i poslije simuliranog procesa probave. Rezultati su pokazali da različite tehnike mljevenja značajno utječu na mikrostrukturu, veličinu čestica i stabilnost bioaktivnih spojeva, s kugličnim mljevenjem kao najpovoljnijim za očuvanje fenola. Granulometrijska analiza otkrila je najveću zastupljenost čestica veličine 200 µm nakon mljevenja mlinom s noževima i kugličnim mlinom, dok su kod planetarnog mlina prevladavale čestice iznad 200 µm. Nasipna gustoća praha bila je najviša kod mljevenja kugličnom mlinom što je ujedno doprinijelo svojstvima tečenja. Analiza boje pokazala je da je prah nakon mljevenja planetarnim mlinom imao najtamniju boju zbog oksidacije materijala, dok je mljevenje kugličnim mlinom najmanje utjecalo na promjenu boje. Nakon simulirane probave, fenolni spojevi su pokazali visoku stabilnost, osobito nakon želučane faze probave, dok je stabilnost opadala nakon crijevne faze. Mljevenje kugličnim mlinom dalo je najbolje rezultate u očuvanju fenola nakon obje faze probave, dok su nesamljeveni uzorci imali najveću biodostupnost fenolnih spojeva. Ovi rezultati ukazuju na značajan potencijal tušta kao funkcionalne hrane i dodatka prehrani, posebice u obliku praha, te na važnost optimizacije tehnika mljevenja i skladištenja kako bi se očuvale hranjive i bioaktivne komponente.Purslane (Portulaca oleracea L.) is a plant recognized as a valuable source of nutrients and bioactive compounds, such as omega-3 fatty acids, antioxidants, vitamins, and minerals. Although traditionally perceived as a weed, purslane has high nutritional value and is widely used in food. This paper investigates the production of powder from lyophilized purslane, which retains its nutrients and is used as a dietary supplement. The focus is on examining the differences in the microstructure of powders obtained using different milling techniques (blade mill, ball mill, planetary mill), analyzing particle size, bulk density, color parameters, and the content and composition of phenols before and after a simulated digestion process. The results showed that different milling techniques significantly affect the microstructure, particle size, and stability of bioactive compounds, with ball milling being the most favorable for phenol preservation. Granulometric analysis revealed the largest representation of 200 µm particles after milling with blade and ball mills, while particles larger than 200 µm dominated after milling with the planetary mill. The bulk density of the powder was highest with ball milling, which also contributed to flow properties. Color analysis showed that powder after planetary milling had the darkest color due to material oxidation, while ball milling had the least impact on color retention. After simulated digestion, phenolic compounds showed high stability, particularly after the gastric digestion phase, while stability decreased after the intestinal phase. Ball milling gave the best results for phenol preservation after both phases of digestion, while unmilled samples had the highest bioavailability of phenolic compounds. These results highlight the significant potential of purslane as a functional food and dietary supplement, especially in powder form, and the importance of optimizing milling and storage techniques to preserve its nutritional and bioactive components
Evaluation of the rosemery extract effect on the thermal properties of polyethylene oxide based composite material : diploma thesis
No full textPoli(etilen-oksid) (PEO) je vodotopljiv, netoksičan i biokompatibilan polimer s velikim potencijalnom primjene u mnogim granama industrijama. Kako bi mu se proširila primjena, neka svojstva je potrebno poboljšati dodavanjem aditiva. Dodatak prirodnih aditiva, poput ekstrakta ružmarina (ER), predstavlja strategiju za poboljšanje strukturnih, toplinskih, mehaničkih i biorazgradljivih svojstava. Cilj ovog rada je pripremiti kompozite PEO/ER ekstruzijom, istražiti utjecaj dodatka ER na strukturu PEO primjenom infracrvene spektroskopije sa Fourierovom transformacijom, zaključiti o utjecaju dodatka ER na toplinska svojstva PEO pomoću diferencijalne pretražne kalorimetrije (DSC) i temeljem termogravimetrijske analize (TGA) zaključiti o utjecaju dodatka ER na toplinsku postojanost PEO. Ovakvo istraživanje omogućava dublje razumijevanje utjecaja ER na svojstva PEO, što je ključno za razvoj novih materijala s unaprijeđenim svojstvima.Poly(ethylene-oxide) (PEO) is water-soluble, non-toxic and biocompatible polymer with great potential for various industries. In order to expand its application, some properties needs to be enhanced by adding additives. Adding natural additives such as rosemary extract (ER), represents a strategy for improving structural, thermal, mechanical and biodegradable properties. The aim of this study is to prepare PEO/ER composite by hot-melt extrusion, investigate the influence of ER addition on the structure of PEO using Fourier-transform infrared spectroscopy (FTIR), conclude about the effect of ER addition on thermal properties of PEO using differential scanning spectroscopy (DSC) and based on thermogravimetric analysis (TGA) estimate the effect of ER addition on thermal stability of PEO. This research enables a deeper understanding of the impact of ER on PEO properties, which is crucial for the devolopment of new materials with improved properties
The effect of propolis extract on the corrosion behavior of Ti and Ti-6Al-4V alloy in simulated oral cavity conditions : diploma thesis
No full textTitanij i njegove legure su, zbog biokompatibilnosti i visoke otpornosti na koroziju, standardni materijali za izradu dentalnih implantata. Korozijska otpornost ovih materijala povezana je s prisutnošću zaštitnog oksidnog sloja na površini. Međutim, tijekom upale nastaju različiti reaktivni spojevi kisika koji mogu oštetiti pasivni oksidni sloj što rezultira degradacijom titanijevih implantata. Jedna od često primjenjivanih metoda zaštite metala od korozije je zaštita metala inhibitorima korozije. U ovom radu istraživan utjecaj etanolnog ekstrakta propolisa na korozijsko ponašanje titanijevih biomaterijala (Ti i Ti-6Al-4V) u simuliranim uvjetima usne šupljine bez upale, s blažom ili s težom upalom. Ispitivanja su provedena elektrokemijskim metodama (metoda mjerenja potencijala otvorenog strujnog kruga, metoda linearne polarizacije i potenciodinamička polarizacijska metoda), a površine uzoraka analizirane su optičkim mikroskopom. Dobiveni rezultati pokazuju kako etanolni ekstrakt propolisa inhibira koroziju Ti u simuliranim uvjetima usne šupljine bez upale i s blažom upalom, a u simuliranim uvjetima usne šupljine s težom upalom etanolni ekstrakt propolisa potiče koroziju Ti. Etanolni ekstrakt propolisa inhibira koroziju Ti-6Al-4V legure u simuliranim uvjetima usne šupljine bez upale i s upalom. Inhibitorska djelotvornost etanolnog ekstrakta propolisa je najveća za Ti-6Al-4V leguru u simuliranim uvjetima usne šupljine bez upale, a smanjuje se s povećanjem stupnja upale. Rezultati istraživanja ukazuju na mogućnost primjene ispitivanog etanolnog ekstrakta propolisa kao korozijskog inhibitora za zaštitu od korozije Ti i Ti-6Al-4V legure u ispitivanim uvjetima.Titanium and its alloys are commonly used for dental implants prosthetics owing to their high biocompatibility and corrosion resistance. The corrosion resistance of these materials is related to the presence of the protective oxide film on the surface. However, various reactive oxygen species are present during inflammation, which can alter the passive film, resulting in the degradation of the titanium implants. Using corrosion inhibitors is one of the most common methods to prevent corrosion in metal and alloys. This research examined the effect of ethanolic extract of propolis on the corrosion behavior of titanium biomaterials (Ti and Ti-6Al-4V) in simulated oral cavity conditions without inflammation, with moderate or strong inflammation. This study was carried out by electrochemical techniques (open circuit potential measurement, linear polarisation, and potentiodynamic polarisation measurement), while the specimen’s surface was examined using an optical microscope. The results show that in simulated conditions of the oral cavity without and with moderate inflammation, the ethanolic extract of propolis inhibits Ti corrosion. In contrast, in simulated conditions of the oral cavity with strong inflammation, it promotes Ti corrosion. The ethanolic extract of propolis reduces corrosion of Ti-6Al-4V alloy in simulated oral cavity conditions, both without and with inflammation. The maximal inhibitory efficiency of ethanolic extract of propolis was for the Ti-6Al-4V alloy in simulated conditions of the oral cavity without inflammation, but inhibition efficiency decreased as the degree of inflammation increased. The results show that the tested ethanolic extract of propolis can be used as a corrosion inhibitor for the protection of Ti and Ti-6Al-4V alloy under the tested conditions
Statistical analysis of total water hardness data of the Jadro river : diploma thesis
No full textU diplomskom radu izvršena je statistička analiza podataka o ukupnoj tvrdoći vode koristeći različite statističke metode. Cilj ovog diplomskog rada je primjenom različitih statističkih metoda analizirati podatke o ukupnoj tvrdoći vode na pojedinim lokacijama u gradu Splitu kao i na samom izvorištu rijeke Jadro. Na temelju prikupljenih podataka o ukupnoj tvrdoći vode na različitim lokacijama u području Splita te na izvoru rijeke Jadro, podaci su obrađeni pomoću deskriptivne statistike kako bi se dobio uvid u osnovne karakteristike uzoraka, poput srednje vrijednosti, standardne devijacije, raspona i drugih relevantnih statističkih parametara. Daljnja analiza uključivala je primjenu inferencijalne statistike s ciljem testiranja hipoteza i donošenja zaključaka o populaciji iz koje su uzorci uzeti. Korištene metode uključivale su T - test i F - test radi utvrđivanja značajnosti razlika i povezanosti među različitim skupinama podataka. Ovim istraživanjem istaknuta je važnost statističke obrade podataka u razumijevanju i interpretaciji ne samo mjerenja tvrdoće vode, već i brojnih drugih okolnosti iz svakodnevnog života.In this thesis, a statistical analysis of data on total water hardness was conducted using various statistical methods. The aim of this thesis is to analyze data on total water hardness at specific locations in the city of Split as well as at the Jadro River source using different statistical methods. Based on the collected data on total water hardness at different locations in the Split area and at the Jadro River source, the data were processed using descriptive statistics to gain insight into the basic characteristics of the samples, such as mean, standard deviation, range, and other relevant statistical parameters. Further analysis included the application of inferential statistics to test hypotheses and draw conclusions about the population from which the samples were taken. The methods used included the T - test and F - test to determine the significance of differences and relationships between different data groups. This research highlighted the importance of statistical data processing in understanding and interpreting not only measurements of water hardness but also numerous other circumstances from everyday life
Wastewater treatment using a hybrid process of electrocoagulation, zeolite, and ultrasound : diploma thesis
No full textU ovom radu provedena su ispitivanja hibridnog procesa obrade kompostne otpadne vode kombinacijom elektrokoagulacije, sintetskog zeolita granulacije < 40 µm i dvije razine intenziteta ultrazvuka snage od 240 W, minimalnoj i maksimalnoj, a koje odgovaraju razinama 1 i 5. Eksperimenti su izvedeni u elektrokemijskoj ćeliji s aluminijevim, željeznim i cinkovim elektrodama, pri konstantnoj gustoći struje od 0,0182 A/cm 2 , udaljenosti elektroda od 3 cm, brzinom vrtnje miješala 250 okr/min, dodatkom elektrolita 0,5 g/L i zeolita 15 g/L. Tijekom eksperimenta pratili su se parametri poput pH vrijednosti, temperature i električne vodljivosti, dok su mutnoća, ukupni isparni ostatak i kemijska potrošnja kisika određivani na početku i kraju procesa. Nakon provedbe hibridnog procesa ispitane su promjene mase elektroda te test taloživosti suspenzija. Rezultati su pokazali da je za obradu kompostne otpadne vode najbolje upotrijebiti elektrokoagulaciju sa zeolitom i željeznim elektrodama uz primjenu intenziteta snage ultrazvuka razine 5. Izračun operativnih troškova pokazao je da istovremena primjena i zeolita i ultrazvuka u svrhu boljeg otapanja elektroda ne pokazuje sinergijski efekt, osim kod hibridnog procesa EKZ sa Fe elektrodama i intenzitetom snage ultrazvuka razine 5. To ukazuje da odabir materijala elektroda je vrlo bitan čimbenik koji određuje hoće li istovremena primjena zeolita i ultrazvuka imati pozitivan efekt.In this study, a hybrid process for the treatment of compost wastewater was investigated using a combination of electrocoagulation, synthetic zeolite granulation <40 μm and two levels of ultrasonic power intensity of 240 W, minimum and maximum, corresponding to levels 1 and 5. The experiments were carried out in an electrochemical cell with aluminium, iron and zinc electrodes, at a constant current density of 0.0182 A/cm², an electrode distance of 3 cm, a stirring speed of 250 rpm, with the addition of 0.5 g/L electrolyte and 15 g/L zeolite. During the experiment, parameters such as pH value, temperature and electrical conductivity were monitored, while turbidity, total solids and chemical oxygen demand were determined at the beginning and end of the process. After a hybrid process the electrode mass changes and the settling test of the suspension were examined. The results showed that electrocoagulation with zeolite and iron electrodes using a level 5 ultrasonic power intensity is the most suitable for the treatment of composting wastewater. The calculation of operating costs showed that the simultaneous use of zeolite and ultrasound to improve electrode dissolution has no synergistic effect, except in the case of the hybrid ECZ process with Fe electrodes and a level 5 ultrasonic power intensity. This indicates that the choice of electrode material is a decisive factor in determining whether the simultaneous use of zeolite and ultrasound has a positive effect
Application of steel electrodes in the treatment of compost wastewater by the combined process of electrocagulation, zeolite and magnet : diploma thesis
No full textU ovom radu je ispitan utjecaj NdFeB magneta na proces elektrokoagulacije u kombinaciji sa zeolitom u cilju pročišćavanja otpadne vode. Korišten je stakleni elektrokemijski reaktor s elektrodama od ugljičnog čelika pri čemu je NdFeB magnet bio smješten ispod reaktora. Ispitivanja su provedena u vremenskom periodu od 10 do 30 minuta, bez i s podešavanjem pH vrijednosti na pH = 3,72, pri čemu su mjereni parametri kao što su promjena pH vrijednosti i temperature otopine s vremenom, promjena mase elektroda, napon i sposobnost taloženja suspenzije. Rezultati su pokazali da postupak elektrokoagulacije s magnetom dovodi do nešto većeg porasta pH otopine i nešto manjeg porasta temperature u usporedbi s elektrokoagulacijskim postupkom. Primijećeno je smanjenje kemijske potrošnje kisika (KPK) za 84.08- 91.00% nakon 30 minuta provedbe eksperimenta, bez vidljivog utjecaja magneta na ove vrijednosti. Nešto veća oštećenja površine elektroda su vidljiva kod upotrebe magneta pri čemu se najveće promjene uočavaju kod mjerenja od 20 minuta. Smanjenje mase anode raste s vremenom provođenja eksperimenta, a uočena je i mala promjena mase katode. Oba hibridna postupka omogućuju 80-100% regeneracije mase zeolita. Manja potrošnja energije (niže vrijednosti napona i snage) su potrebne kod postupaka koji su provedeni korištenjem magneta u odnosu na eksperimente bez magneta. Pozitivan utjecaj magneta na taloženje zamijećen je u eksperimentu s vremenom kontakta od 20 minuta.In this work, the influence of the NdFeB magnet on the electrocoagulation process in combination with zeolite for wastewater treatment is investigated. An electrochemical glass reactor with carbon steel electrodes was used, under which a NdFeB magnet was attached. The tests were carried out over a period of 10 to 30 minutes, without and with the pH adjusted to pH = 3.72, measuring parameters such as the change in pH and temperature of the solution over time, the change in the mass of the electrode, the voltage and the ability to settle the suspension. The results showed that the electrocoagulation method with a magnet led to a slightly higher increase in the pH of the solution and a slightly lower increase in temperature compared to the electrocoagulation method. After 30 minutes of the experiment, a decrease in chemical oxygen demand (COD) of 84.08-91.00% was observed without the magnet having a visible effect on these values. When a magnet is used, slightly greater damage to the electrode surface is visible, with the most significant changes observed in measurements from 20 minutes onwards. The decrease in the anode's mass increases with the experiment's duration, but a small change can also be observed in the mass of the cathode. Both hybrid processes enable 80-100% regeneration of the zeolite. Procedures carried out with a magnet require less energy consumption (lower voltage and power values) than experiments without a magnet. The positive influence of the magnet on the deposition was observed in the experiment with a contact time of 20 minutes
Impeller type impact on wastewater treatment using the hybrid process of electrocoagulation and zeolite : diploma thesis
No full textU ovom radu provedena su ispitivanja hibridnog procesa obrade otpadne vode elektrokoagulacijom uz dodatak sintetskog zeolita granulacije < 40 µm uz primjenu operacije miješanja korištenjem različitog tipa miješala, odnosno turbinskog tipa miješala s ravnim lopaticama SBT (engl. straight blade turbine) i turbinskog tipa miješala s lopaticama pod nagibom PBT (engl. pitched blade turbine) miješala pri različitim vremenima kontakta od 30, 20 i 10 minuta. Eksperimenti su izvedeni u elektrokemijskoj ćeliji s Al i Fe elektrodama, pri konstantnoj gustoći struje od 0,0182 A/cm 2 , udaljenosti elektroda od 3 cm, dodatkom elektrolita (0,5 g/L) i zeolita (15 g/L). Tijekom eksperimenta pratila se pH vrijednosti, temperatura i električna vodljivost, dok su kemijska potrošnja kisika, mutnoća i ukupni isparni ostatak određeni na početku i na kraju procesa. Nakon provedbe hibridnog procesa ispitane su promjene mase elektroda te je proveden test taloženja suspenzija. Rezultati su pokazali da je za obradu otpadne vode najbolje upotrijebiti elektrokoagulaciju bez dodatka zeolita uz primjenu Fe elektroda te uz primjenu PBT miješala. Izračun operativnih troškova pokazao je da dodatak zeolita i duže vrijeme provedbe procesa pridonosi boljem otapanju elektroda, neovisno o tipu miješala.This study examined a hybrid wastewater treatment process through electrocoagulation using synthetic zeolite with a particle size of < 40 µm by applying mixing operations using different impeller types: SBT (straight blade turbine) and PBT (pitched blade turbine). The experiments involved varying contact times of 30, 20, and 10 minutes. They were conducted in an electrochemical cell with aluminum and iron electrodes, at a constant current density of 0,0182 A/cm², an electrode spacing of 3 cm, and the addition of electrolyte (0,5 g/L) and zeolite (15 g/L). During the experiments pH values, temperature, as well as electrical conductivity were monitored. Chemical oxygen demand, turbidity, and total solids were determined at the beginning and at the end of the process. After the hybrid process was completed, changes in electrode mass and the sedimentation of suspensions were examined. The results indicated that the most effective wastewater treatment was achieved through electrocoagulation without the addition of zeolite, using iron electrodes and PBT impeller. The operational cost calculations showed that the addition of zeolite and longer processing time enhances electrode dissolution, regardless of the impeller type
Testing the stability of fluoride solutions of different concentrations in glass packaging : diploma thesis
No full textStaklo je jedan od najvažnijih materijala u svakodnevnom životu, u kojem se pojavljuje posvuda, a razlog zbog kojeg se tako često koristi je njegova kemijska stabilnost. Kemijski je stabilno zbog svoje amorfne strukture odnosno izostanka pravilnog rasporeda atoma. Iako je staklo otporno na mnoge kemikalije, ono nije univerzalno inertno. Zadatak ovog diplomskog rada je bio u određenom vremenskog periodu, u nekoliko staklenih boca pohraniti različite koncentracije standardne otopine natrijevog fluorida, utvrditi utječe li pohrana tih otopina u staklu na promjenu koncentracije fluorida, odnosno događa li se interakcija otopine (fluorida) sa staklom. U eksperimentu su pripravljene otopine natrijevog fluorida u rasponu koncentracija 1,0×10 --6 do 1,0×10 -2 mol L -1 . Radnim otopinama u svakom mjerenju izmjeren je potencijal, konstruiran je graf ovisnosti potencijala o pF-vrijednosti koncentracija i metodom dodatka standarda matematičkim modelom određena koncentracija. Na temelju eksperimentalnih podataka doneseni su određeni zaključci. Najmanje odstupanje od očekivane koncentracije ispitivanih otopina zabilježeno je u otopini koncentracije 1,0×10 -2 mol L -1 , dok je najveće odstupanje zabilježeno u otopini koncentracije 1,0×10 -3 mol L -1 . Koncentracija otopine 1×10 -5 mol L - 1 je bila nešto malo viša u odnosu na očekivanu vrijednost kroz sva mjerenja. U nastavku eksperimenta uočeno je kako se prvotno izmjerene koncentracije previše ne mijenjaju, pri tome blago rastu ili padaju ali variraju oko početno izmjerenih vrijednosti. Iz grafičkog prikaza ovisnosti pF vrijednosti o danima mjerenja, kao i iz ovisnosti nagiba o danima mjerenja zaključeno je kako se koncentracije, iako u pojedinačnim mjerenjima blago rastu ili padaju, u konačnici ipak ne mijenjaju drastično što ukazuju i navedeni grafički prikazi iz kojih se vidi da su rezultati smješteni uglavnom linearno. Obzirom na to da se ni pri jednoj koncentraciji ne uočava kontinuirani pad vrijednosti kroz cijeli period mjerenja, zaključuje se da u ovom eksperimentu staklo ne utječe na koncentraciju fluorida.Glass is one of the most important materials in everyday life, in which it appears everywhere, and the reason it is used so often is its chemical stability. It is chemically stable due to its amorphous structure, i.e. the absence of a regular arrangement of atoms. Although glass is resistant to many chemicals, it is not universally inert. The task of this thesis was to store different concentrations of a standard solution of sodium fluoride in several glass bottles for a certain period of time, to determine whether the storage of these solutions in glass affects the change in fluoride concentration, or whether the solution (fluoride) interacts with the glass. In the experiment, sodium fluoride solutions were prepared in the concentration range of 1,0×10 -6 to 1,0×10 -2 mol L -1 . The potential was measured with the working solutions in each measurement, a graph of the dependence of the potential on the pF-value of the concentrations was constructed, and the concentration was determined using the standard addition method using a mathematical model. Based on the experimental data, certain conclusions were drawn. The smallest deviation from the expected concentration of the tested solutions was recorded in a solution with a concentration of 1,0×10 -2 mol L -1 , while the largest deviation was recorded in a solution with a concentration of 1,0×10 -3 mol L -1 . The concentration of the solution 1,0×10 -5 mol L -1 was slightly higher compared to the expected value throughout all measurements. In the continuation of the experiment, it was observed that the initially measured concentrations do not change too much, while they rise or fall slightly, but vary around the initially measured values. From the graphical presentation of the dependence of the pF value on the days of measurement, as well as from the dependence of the slope on the days of measurement, it was concluded that the concentrations, although they slightly increase or decrease in individual measurements, ultimately do not change drastically, as indicated by the above graphical representations, which show that the results are arranged mostly linearly. Given that no continuous decrease in values is observed at any concentration throughout the entire measurement period, it is concluded that in this experiment the glass does not affect the fluoride concentration