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Forced degradation of atazanavir and nirmatrelvir
No full textU zadnjih nekoliko desetljeća razvoj farmaceutika i njihova primjena u medicini su znatno poboljšali kvalitetu ljudskog života. No, uslijed njihove proizvodnje i korištenja dospijevaju u okoliš gdje predstavljaju opasnost za organizme u njemu. Farmaceutici, njihovi metaboliti i nusprodukti u okolišu mogu biti vrlo postojani i akumulirati se što može rezultirati visokim koncentracijama koje djeluju toksično na cijeli ekosustav. Zbog toga potrebno je istražiti njihovu stabilnost i postojanost u okolišu te istražiti moguće razgradne produkte koji pri tome nastaju. U ovom radu ispitana je stabilnost i ponašanje dvaju farmaceutika, atazanavira i nirmatrelvira, provođenjem testova prisilne razgradnje. Prisilna razgradnja se provodila na 0,003 mM otopini atazanavira i 0,1 mM otopini nirmatrelvira u uvjetima: lužnate hidrolize s
1,0 M NaOH na sobnoj temperaturi tijekom 24 h, kisele hidrolize s 1,0 M HCl na sobnoj temperaturi tijekom 24 h, oksidacijskom razgradnjom s 30% H2O2 na sobnoj temperaturi tijekom 24 h, termičko razgradnjom pri temperaturama od 30 i 40 °C tijekom 7 dana, neutralne hidrolize na sobnoj temperaturi (25 °C) tijekom 7 dana i fotolitičke razgradnje djelovanjem UV svjetlosti jačine 600 W/m^2 pri 25 °C tijekom 6 sati. Analize svih uzoraka su se provodile na HPLC-u te su u tu svrhu razvijene i validirane HPLC metode. Za razvijene metode utvrđeno je da zadovoljavaju sve kriterije validacije: linearnost s koeficijentom determinacije većim od 0,9900, točnost s analitičkim povratom između 70 i 130% te preciznost s RSD vrijednostima manjim od 10%. Rezultati ispitivanja prisilne razgradnje pokazali su očekivanu stabilnost ispitivanih spojeva pri većini primijenjenih uvjeta.In recent decades, the development of pharmaceuticals and their use in medicine have significantly improved quality of human life. However, as a result of their production and use, they end up in the environment, where they pose a risk to the organisms living in it. Pharmaceuticals, their metabolites and degradation products can be very persistent and accumulate in the environment, which can lead to high concentrations that have a toxic effect on the ecosystem. For this reason, it is necessary to investigate their stability and persistence in the environment as well as the possible degradation products that are formed. In this work, the stability and behavior of two pharmaceuticals, atazanavir and nirmatrelvir, were tested by forced degradation experiments. Forced degradation was performed with a 0.003 mM solution of atazanavir and a 0.1 mM solution of nirmatrelvir under the following conditions: alkaline hydrolysis in the presence of a 1.0 M NaOH solution at room temperature for a period of 24 hours, acid hydrolysis in the presence of a 1.0 M HCl solution at room temperature over a period of 24 hours, oxidation in the presence of a 30% H2O2 solution at room temperature over a period of 5 hours, thermal decomposition at 30 °C and 40 °C over a period of 7 days, neutral hydrolysis at room temperature (25 °C) over a period of 7 days and photolytic decomposition under UV light at 600 W/m^2 at 25 °C over a period of 6 hours. HPLC methods were developed and validated for analysis of atazanavir and nirmatrelvir.
The developed methods were found to fulfill all validation criteria: linearity with a coefficient of determination above 0.9900, accuracy with recoveries between 70 and 130% and precision with RSD values of less than 10%. The results of the forced degradation tests showed the expected stability of the tested compounds under most of the applied conditions
Porous bioactive glasses obtained by sol-gel process
No full textPorozna bioaktivna stakla su materijali koji imaju sposobnost spajanja s tkivom u ljudskom tijelu te mogu poticati i stvaranje novog tkiva. Koriste se u medicinskoj primjeni, posebice u području regenerativne medicine i medicinske implatacije. Sol gel postupak je jedna od metoda dobivanja poroznih bio materijala koje karakterizira porozna struktura koja im omogućuje vezivanje na površinu koštanog tkiva. Cilj ovog rada je opis i karakterizacija poroznih bioaktivnih stakala i važnost njihove primjene u inženjerstvu koštanih i mekih tkiva te razumijevanje faza sol gel procesa i utjecaj različitih čimbenika na konačni proizvod.Porous bioactive glasses are materials with the abillity to bond with tissue in the human body and stimulate the growth of new tissue. They are used in medical applications, paticulary in the field of regenerative medicine and implantology. The sol-gel process is one of the methods that obtain porous bio materials characterized by a porous structure that enables them to bind to the surface of bone tissue. The purpose of this work is to describe and characterize porous bioactive glasses and the importance of their application in bone and soft tissue engineering, as well as to understand the phases of the sol gel process and the influence of various factors on the final product
Kinetic characterisation of aldolase immobilized on magnetic nanoparticles
No full textCilj ovog rada bio je odrediti kinetiku kovalentno imobiliziranog enzima DERA u reakciji dvostruke aldolne adicije acetaldehida i kloroacetaldehida. Produkt navedene reakcije je laktol – ključni prekursor u sintezi bočnog lanca statina, lijeka za snižavanje koncentracije kolesterola u krvi. Kao nosioc za imobilizaciju, korištene su magnetske nanočestice, sintetizirane hidrotermalnom metodom, funkcionalizirane 3-aminopropiltrietoksisilanom te aktivirane 10 %-tnim anhidridom jantarne kiseline. Kinetika je za oba koraka reakcije opisana Michaelis-Menteničinom jednadžbom, a kinetički su parametri procijenjeni metodom nelinearne regresije programa MicroMath Scientist. Uz to, razvijen je matematički model procesa i validiran u kotlastom reaktoru.The aim of this work was to determine the kinetics of the covalently immobilized DERA enzyme in the double aldol addition reaction of acetaldehyde and chloroacetaldehyde.
The product of the mentioned reaction is lactol – a key precursor in the synthesis of the side chain of statin, a drug used for lowering blood cholesterol level. Magnetic nanoparticles were used as a carrier and were synthesized by the hydrothermal method, functionalized with 3-aminopropyltriethoxysilane and activated with 10 % succinic anhydride. The kinetics for both reaction steps was described by the Michaelis-Menten equation, and the kinetic parameters were estimated using the nonlinear regression method of the MicroMath Scientist software. A mathematical model of the process was also developed and validated in a batch reactor
Synthesis of statins by immobilized enzyme in continuous flow systems
No full textStatini su farmaceutici koji se koriste za snižavanje kolesterola u krvi i u prevenciji kardiovaskularnih bolesti. Enzim 2-deoksiriboza-5-fosfat aldolaza (DERA) je jedini poznati enzim koji sudjeluje u visokoselektivnoj reakciji aldolne adicije pri čemu nastaje laktol, važan prekursor za proizvodnju bočnog lanca statina. DERA katalizira reakciju sinteze
(3R, 5R)-6-kloro-3,5-dihidroksiheksanala (laktola) dvostrukom aldolnom adicijom acetaldehida (AA) i kloroacetaldehida (CAA). Cilj ovog diplomskog rada bio je provesti sintezu statina imobiliziranim enzimom DERA u različitim tipovima kontinuiranih reaktora volumena 300 i 600 μL te serijski spojenim reaktorima (2 x 300 μL), odnosno ispitati utjecaj različitih volumena i protoka na nastanak međuprodukta, 4-kloro-3-hidroksibutanala (4 C-Cl) i produkta, 6-kloro-3,5-dihidroksiheksanala (6 C-Cl) . Reakcija u reaktorima se provodila pri protocima; 2, 5 i 7 μL/min. Usporedbom procesnih pokazatelja u reaktorima, kao najbolji parametri uspješnosti dobiveni su: XCAA,max = 99,98 % i XCAA,max = 96,93 % u eksperimentima E2-1 (V = 600 μL, q = 2 μL/min) i E3-1 (V = 2 x 300 μL, q = 2 μL/min) pri većem vremenu zadržavanja (87,0 min) dok je najveća produktivnost procesa u iznosu
1,99 mM/min postignuta u eksperimentu E1-3 (V = 300 μL, q = 7 μL/min) pri vremenu zadržavanja od 12,4 min.Statins are pharmaceuticals used to lower cholesterol in the blood and to prevent cardiovascular diseases. Enzyme 2-deoxyribose-5-phosphate aldolase (DERA) is the only known enzyme that participates in the highly selective aldol addition reaction in which lactol, an important precursor for statin side chain production, is formed. DERA catalyzes the synthesis reaction of (3R, 5R)-6-chloro-3,5-dihydroxyhexanal (lactol) by double aldol addition of acetaldehyde (AA) and chloroacetaldehyde (CAA). The aim of this work was to carry out the synthesis of statins with an immobilized enzyme DERA in different types of continuous reactors with volumes of 300 and 600 μL and in series connected reactors (2 x 300 μL), i.e. examine the influence of different volumes and flow rates on formation of the intermediate product, 4-chloro-3-hydroxybutanal (4 C-Cl) and the product, 6-chloro-3,5-dihydroxyhexanal (6 C-Cl). The reaction in the reactors was carried out at flow rates; 2, 5 and 7 μL/min.
By comparing the process indicators in the reactors, as the best performance parameters were obtained: XCAA,max = 99.98 % and XCAA,max = 96.93 % in experiments
E2-1 (V = 600 μL, q = 2 μL/min) and E3-1 (V = 2 x 300 μL, q = 2 μL/min) at a longer retention time (87.0 min), while the highest productivity of the process in the amount of
1.99 mM/min was achieved in experiment E1-3 (V = 300 μL, q = 7 μL/min) at a retention time of 12.4 min
Development and validation of the HPLC-MS/MS method for the determination of pseudo-persistent pollutants in water
No full textPotrošnja vode zadnjih desetljeća uslijed rastućeg broja stanovništva, nekontrolirane urbanizacije i industrijalizacije znatno se povećala i danas predstavlja visokovrijedno dobro. Održivi razvoj u budućnosti u svom načelu mora kontrolirati i detektirati onečišćivala svih sirovina a poglavito vode. Stoga razvoj i validacija metoda za određivanje pseudopostojanih onečišćivala u vodama, ima veliki značaj u procesu očuvanja životne sredine.
U pseudopostojana onečišćivala ubrajaju se svi spojevi koji se ne bi trebali nalaziti u okolišu, a u njega dospijevaju antropološkim putem. Razvoj i validacija metoda za pseudopostojana onečišćivala je nužna kako bi ih se moglo redovito pratiti u okolišu, ali i u otpadnim i pitkim vodama. Potpuna validacija metoda zahtijeva ispitivanje svih izvedbenih karakteristika metode, a one su: specifičnost/selektivnost, linearnost, točnost, istinitost, preciznost, granica detekcije i kvantifikacije, radno područje i robusnost. Najbolje metode za njihovo praćenje su kromatografske metode vezane na spektrometar masa kojima se omogućuje istovremena detekcija, identifikacija i kvantifikacija ispitivanih analita. Cilj ovog rada je bio validirati metodu za određivanje antibiotika, antiparazita, antireumatika i antivirotika (klozantel, gentamicin, baricitinib i ivermektin) te ispitati karakteristike i na temelju rezultata zaključiti zadovoljava li analitička metoda kriterije prihvatljivosti. Razvoj metode prvo je proveden na HPLC-DAD kromatografskom sustavu pri čemu su određivani sljedeći validacijski parametri: specifičnost/selektivnost, linearnost, osjetljivost, preciznost, iskoristivost, granica detekcije i kvantifikacija. Nakon toga metoda je transverirana na HPLC-MS/MS uređaj.Water consumption has increased significantly in recent decades due to the growing population, uncontrolled urbanization and industrialization, and today it represents a highvalue commodity. In principle, sustainable development in the future must control and detect pollutants in all raw materials, especially water. Therefore, the development and validation of methods for the determination of pseudo-persistent pollutants in water is of great importance in the process of environmental protection. Pseudo-persistent pollutants include all compounds that should not be found in the environment, but which reach it through anthropological means. The development and validation of methods for
pseudo-persistent pollutants is necessary so that they can be regularly monitored in the environment, but also in waste and drinking water. Full method validation requires examination of all performance characteristics of the method, namely: specificity/selectivity, linearity, accuracy, truthfulness, precision, limit of detection and quantification, working area and robustness. The best methods for their monitoring are chromatographic methods connected to a mass spectrometer, which enable simultaneous detection, identification and quantification of the analyzed analytes. The aim of this work was to validate the method for determining antibiotics, antiparasitics, antirheumatics and antivirals (clozantel, gentamicin, baricitinib and ivermectin) and to examine the characteristics and based on the results to conclude whether the analytical method meets the acceptance criteria. The development of the method was first carried out on the HPLC-DAD chromatographic system, where the following validation parameters were determined: specificity/selectivity, linearity, sensitivity, precision, usability, detection limit and quantification. After that, the method was transferred to the HPLC-MS/MS device
Effect of multiple mechanical recycling process on properties of high-density polyethylene
No full textPolimerni materijali od iznimne su važnosti zbog svoje velike primjene zbog koje se nalaze svuda oko nas. Upravo radi toga nastaju i velike količine polimernog otpada koji, ukoliko se ne zbrine može imati negativan utjecaj na ljude i okoliš. Jedan od načina zbrinjavanja polimernog otpada je mehaničko recikliranje istog. Mehaničko recikliranje pokazalo se kao učinkovit postupak prerade termoplastičnih polimernih materijala čime im se omogućava ponovno korištenje u iste ili druge svrhe, te se smanjuje količina ukupnog polimernog otpada. Kako je tijekom mehaničkog recikliranja, koje uključuje toplinsku preradu, moguće da dođe do određenog stupnja degradacije materijala u ovom radu ispitano je dolazi li do promjene svojstava polietilena visoke gustoće (HDPE) uslijed više ciklusa recikliranja. Uzorci su nakon provedenog mehaničkog recikliranja analizirani različitim metodama, toplinskim i spektroskopskim, kao i pomoću mehaničke kidalice, kako bi se ustanovilo dolazi li do promjene svojstava (degradacije) navedenog polimernog materijala uslijed mehaničkog recikliranja. Ukupno je provedeno 12 ciklusa mehaničkog recikliranja, a analizirani su uzorci HDPE-a nakon 3., 6., 9. i 12. ciklusa, te svježi HDPE. Pomoću infracrvene spektroskopije s Fourierovom transformacijom (FTIR) snimljeni su spektri uzoraka, pomoću kojih je izračunat karbonilni indeks (C.I.) kako bi odredilo dolazi li do degradacije. Toplinska svojstva su određena diferencijalnom pretražnom kalorimetrijom (DSC) i termogravimetrijskom analizom (TGA). Osim toga određen je i maseni protok taljevine (MFR), te su ispitana mehanička svojstva uzoraka pomoću mehaničke kidalice čime su dobiveni podaci o prekidnoj čvrstoći, prekidnom istezanju, te elastičnosti ispitanih uzoraka. Iz rezultata istraživanja došlo se do zaključka da višetruko mehaničko recikliranje nema značajan negativan utjecaj na kemijsku strukturu i svojstva polietilena visoke gustoće koji bi ograničio primjenu recikliranog HDPE-a odnosno mehaničko recikliranje učinkovita je metoda oporabe HDPE-a.Polymeric materials are extremely important because of their wide range of applications, which is why they can be found all around us. For this very reason, large amounts of polymer waste are generated which, if not disposed of, can have a negative impact on people and the environment. One of the ways to dispose of polymer waste is mechanical recycling. Mechanical recycling has proven to be an effective way of processing thermoplastic polymers, enabling their reuse for the same or other purposes and reducing the total amount of polymer waste. Since mechanical recycling involving thermal processing can potentially cause some degree of material degradation, this study investigated whether the properties of high-density polyethylene (HDPE) change after multiple recycling cycles. Samples were analyzed after mechanical recycling using various methods, including thermal and spectroscopic techniques as well as mechanical testing, to determine whether the properties of this polymer material change (degrade) as a result of mechanical recycling. A total of 12 recycling cycles were performed and the HDPE samples were analyzed after the 3rd, 6th, 9th and 12th cycles as well as fresh HDPE. Fourier transform infrared spectroscopy (FTIR) was used to record the spectra of the samples, from which the carbonyl index (C.I.) was calculated to determine the degree of degradation. The thermal properties were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In addition, the melt flow rate (MFR) was determined and the mechanical properties of the samples were tested using a universal testing machine, which provided data on the tensile strength, elongation at break and elasticity of the tested samples. From the research results, it was concluded that multiple mechanical recycling has no significant negative effects on the chemical structure and properties of high-density polyethylene, which would limit the use of recycled HDPE, i.e. mechanical recycling is an effective method of HDPE recycling
Liquid-liquid equilibrium in the systems involving biodiesel based on fatty acid propyl ester
No full textPrimarni zadatak rada je proučiti faznu ravnotežu kapljevina-kapljevina u dvokomponentnim, pseudodvokomponentnim i pseudotrokomponentnim sustavima koji, uz biodizel – propilni ester masnih kiselina (eng. fatty acid propyl ester, FAPRE), čine glicerol, propanol i voda; spojevi koji su prisutni u smjesi produkata reakcije transesterifikacije kojom se biodizel sintetizira. Eksperimentalno je određena ravnoteža kapljevina-kapljevina pri 25 °C i atmosferskom tlaku, te su izmjerena fizikalna svojstva biodizela: gustoća, dinamička i kinematička viskoznost, napetost površine, točka kristalizacije, tecište i maglište, svojstva važna za primjenu biodizela kao motornog goriva. Temperaturno ponašanje biodizela istraženo je tehnikama diferencijalne pretražne kalorimetrije, termogravimetrijske analize i polarizirajuće mikroskopije. Čistoća biodizela provjerena je infracrvenom spektroskopijom s Fourierovom transformacijom. Utvrđeno je da su sustavi propanol – FAPRE, propanol – voda, propanol – glicerol i voda – glicerol mješljivi u potpunosti, sustav glicerol – FAPRE potpuno je nemješljiv kao i sustav voda – FAPRE. Voda je pogodno otapalo za uklanjanje glicerola i propanola iz produktne smjese. Fizikalna svojstva biodizela ne zadovoljavaju trenutno važeće norme za dizelska goriva i djelomično zadovoljavaju važeću normu za biodizel.The primary goal of this investigation was determination of liquid-liquid equilibrium in pseudoternary systems consisting of fatty acid propyl esters (FAPRE) – biodiesel, glycerol, propanol and water; compounds present in product mixtures after synthesis of biodiesel by the transesterification reaction. Liquid-liquid equilibrium was experimentally measured at 25 °C and atmospheric pressure. Physical properties of biodiesel, such as dynamic viscosity, kinematic viscosity, density, surface tension, crystallization point, cloud point and pour point were also measured; these properties are important for the application of biodiesel as engine fuels. The temperature behavior of biodiesel was investigated by differential scanning calorimetry, thermogravimetic analysis, and polarized light microscopy methods. The purity of biodiesel was determined using Fourier-transform infrared spectroscopy. Results show that the systems propanol – FAPRE, propanol – water, propanol – glycerol and water – glycerol are completely miscible, The systems water – FAPRE and FAPRE – glycerol are completely immiscible. Water can be used as a solvent for the removal of glycerol and propanol from the product mixture. The physical properties of biodiesel do not satisfy the regulations in force related to diesel fuels and partially satisfy the regulations in force related to biodiesel
Antioxidant activity of essential oils
No full textEterična ulja imaju dugu povijest primjene, datirajući unatrag do samih početaka civilizacije. Različita istraživanja i interes znanstvenika doveli su do razvoja brojnih metoda ekstrakcije eteričnih ulja, koja su danas integralni dio svakodnevnog života. Zbog svojih ljekovitih svojstava eterična ulja nalaze široku primjenu u farmaceutskoj i prehrambenoj industriji, te su ključne komponente u industriji parfema i kozmetike. U ovom radu ispitan je kemijski sastav i antioksidacijska aktivnost uzoraka eteričnih ulja ekstrahiranih hidrodestilacijom po Clevengeru. Eterična ulja ekstrahirana su iz kore limuna (Citrus limon), lovorovog lista (Laurus nobilis), klinčića (Syzygium aromaticum), muškatnog oraščića (Myristica fragrans Houtt – officinalis L.), zvjezdastog anisa (Pimpinella anisum) i origana (Origanum vulgare).
Na temelju provedene ekstrakcije dani su podaci o prinosu svake vrste eteričnog ulja. Karakterizacija uzoraka provedena je tankoslojnom kromatografijom, sustavom plinske kromatografije, infracrvenom spektroskopijom s Fourierovom transformacijom. Za svaki uzorak ekstrahiranog eteričnog ulja identificirana je najzastupljenija komponenta. Ispitanim uzorcima određen je udio ukupnih prisutnih fenola metodom s Folin – Ciocalteu reagensom, a zatim je DPPH i ABTS metodama određena antioksidacijska aktivnost.Essential oils have a long history of use, dating back to the beginnings of civilization. Various research efforts and scientific interest have led to the development of numerous extraction methods for essential oils, which are now an integral part of everyday life. Due to their medicinal properties, essential oils are widely used in the pharmaceutical and food industries and are also important ingredients in the perfume and cosmetics industries. In this study, the chemical composition and antioxidant activity of essential oil samples extracted by Clevenger hydrodistillation are investigated. Essential oils were extracted from lemon peel (Citrus limon), laurel (Laurus nobilis), clove (Syzygium aromaticum), nutmeg (Myristica fragrans Houtt – officinalis L.), star anise (Pimpinella anisum) and oregano (Origanum vulgare).
The data on the yield of the individual types of essential oils originate from the extraction carried out. The samples were characterised using thin-layer chromatography, gas chromatography and Fourier transform infrared spectroscopy. For each extracted essential oil sample, the most abundant component was identified. The total phenolic content of the analysed samples was determined using the Folin-Ciocalteu reagent method, followed by the determination of the antioxidant activity using the DPPH and ABTS methods
Preparation optimization and characterization of porous PLA
No full textPoli(laktidna kiselina) ili polilaktid (PLA) je polimerni materijal koji je moguće pripremiti iz obnovljivih izvora poput kukuruznog škroba ili šećerne trske zbog čega se sve više primjenjuje kao prikladna zamjena konvencionalnoj plastici na petrokemijskoj osnovi. Najčešća primjena PLA je u medicinske i farmaceutske svrhe te u industriji ambalaže, no brojna istraživanja pokušavaju proširiti njegovu moguću primjenu u drugim industrijskim granama poput automobilske, poljoprivredne, industrije električnih sklopova te industrije pročišćavanja otpadnih voda. PLA se često obrađuje i oblikuje na različite načine kao što su 3D ispis, elektroispredanje, ekspandiranje, fazna separacija i druge kako bi se izradio PLA određenog profila za navedene primjene. Jedan od često zahtijevanih profila PLA za primjene u industriji pročišćavanja otpadnih voda jest izrada poroznog materijala, što je bila ishodišna točka istraživanja ovog rada. Priprema poroznog materijala iz komercijalnog PLA granulata provedena je procesom fazne separacije pomoću dva sustava otapalo/neotapalo: i) kloroform/smjesa n-butanola i etanola i ii) diklormetan/smjesa n-butanola i butil acetata. Prilikom izrade poroznog materijala faznom separacijom mijenjali su se način i uvjeti sušenja, miješanja te količine dodanog neotapala. Praćenje porozne strukture materijala provedeno je pomoću pretražnog elektronskog mikroskopa (SEM), a ispitivala su se i mehanička svojstva uzoraka. Određivale su se vrijednosti toplinske vodljivosti, električne otpornosti te kontaktnog kuta. Primjenjivale su se i diferencijalna pretražna kalorimetrija te dinamičko-mehanička analiza. Rezultati pokazuju da je sustav otapalo/neotapalo i dodatak neotapala utjecao na poroznu strukturu materijala. Mehaničko ispitivanje pokazalo je da se sušenjem u običnom sušioniku dobivaju čvršći PLA filmovi, dok se sušenjem u vakuum sušioniku dobivaju žilavi filmovi. Uzorci sustava kloroform/smjesa n-butanola i etanola pokazali su manje vrijednosti toplinske vodljivosti dok su uzorci sustava diklormetan/smjesa n-butanola i butil acetata pokazali hidrofobno ponašanje.Poly(lactic acid) or polylactide (PLA) is a polymer material that can be prepared from renewable sources such as corn starch or sugar cane, which is why it is increasingly used as a suitable replacement for conventional petrochemical-based plastics. The most common application of PLA is for medical and pharmaceutical purposes and in the packaging industry. Still, numerous researchers are trying to expand its application to other industry branches such as automotive, agricultural, electrical, and wastewater treatment. With this, PLA is often processed in various ways, such as 3D printing, electrospinning, foaming, phase separation and others, to produce a specific profile for the specified applications. One of the frequently requested profiles of PLA for use in wastewater treatment is the production of porous carrier material, which was the starting point of this work. Preparation of porous material from commercial PLA pellets was carried out by phase separation using two solvent/non-solvent systems: i) chloroform/mixture of n-butanol and ethanol and ii) dichloromethane/mixture of
n-butanol and butyl acetate. During the preparation of porous material by phase separation, the method and conditions of drying, mixing and the amount of non-solvent added were changed. The porous structure of the material was monitored by scanning electron microscopy (SEM). Mechanical properties of materials were tested and differential scanning calorimetry and dynamic-mechanical analysis were carried out. Also, thermal conductivity, contact angle and electrical resistance of materials were measured. The results show that the solvent/non-solvent system and the addition of non-solvent strongly affect the porous structure of the material. Mechanical testing showed that drying in an oven produces stronger PLA films, while drying in a vacuum oven produces tougher films. The samples of the system chloroform/mixture of n-butanol and ethanol showed lower thermal conductivity values, while the samples of the system dichloromethane/mixture of n-butanol and butyl acetate showed hydrophobic behaviour
Development of composite anode reduced graphene oxide/zinc
No full textCilj ovog diplomskog rada bio je razviti kompozitnu anodu na bazi reduciranog grafenovog oksida (rGO) i metalnog cinka (Zn) te ju okarakterizirati kao sastavnicu cink-ionskih baterija, koje se izdvajaju kao alternativa litij-ionskim sustavima. U okviru istraživanja, analizirana su svojstva reduciranog grafenovog oksida u funkciji elektrodnog materijala, s posebnim naglaskom na njegovu iznimnu električnu vodljivost i veliku specifičnu površinu s velikim brojem aktivnih mjesta, što pogoduje depoziciji većih količina cinka. Također, priređeni su i kompoziti reduciranog grafenovog oksida s ugljikovim nanocijevima (CNT) te titanovim (IV) oksidom (TiO2) u svrhu dodatnog poboljšanja primarnih svojstava rGO te povoljnijeg rada sastavljenih cink-ionskih baterija. Analiza je provedena elektrokemijskim mjernim tehnikama cikličkom voltametrijom i kronoamperometrijom u otopinama 0,1 M KCl i 2 M ZnSO4, a priređene simetrične cinkove ćelije ispitane su metodom kronopotenciometrije. Površina elektrodnih materijala tijekom procesa depozicije cinka karakterizirana je upotrebom optičkog mikroskopa. Uspješno su priređeni rGO-CNT i rGO-CNT-TiO2 slojevi te je na njih uspješno deponiran Zn. Uvođenje TiO2 u sustav poboljšava proces depozicije cinka, čineći ga učinkovitijim i bržim. Primjena (rGO-CNT)-Zn i (rGO-CNT-TiO2)-Zn elektroda u simetričnim cink-ionskim baterijama doprinosi njihovom stabilnom radu uz niže prenapone pri različitim strujnim opterećenjima, bez formiranja dendrita.The aim of this thesis was to develop a composite anode based on reduced graphene oxide (rGO) and metallic zinc (Zn), and to characterize it as a component of zinc-ion batteries, which are emerging as an alternative to lithium-ion systems. As part of the research, the properties of reduced graphene oxide were analyzed as a function of electrode material, with a particular emphasis on its exceptional electrical conductivity and large specific surface area with numerous active sites, which facilitate the deposition of greater amounts of zinc. Furthermore, composites of reduced graphene oxide with carbon nanotubes (CNT) and titanium (IV) oxide (TiO2) were prepared to further improve the primary properties of rGO and enhance the performance of the assembled zinc-ion batteries. The analysis was conducted using electrochemical measurement techniques, including cyclic voltammetry and chronoamperometry in 0,1 M KCl and 2 M ZnSO4 solutions, while the prepared symmetric zinc cells were tested using the chronopotentiometry method. The surface of the electrode materials during the zinc deposition process was characterized using an optical microscope. Successfully prepared rGO-CNT and rGO-CNT-TiO2 layers showed successful zinc deposition. The incorporation of TiO2 into the system improves the zinc deposition process, making it more efficient and faster. The application of (rGO-CNT)-Zn and (rGO-CNT-TiO2)-Zn electrodes in symmetric zinc-ion batteries contributes to their stable operation with lower overpotentials under different current load conditions, without dendrite formation