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Optimiranje reakcijskih uvjeta hidrolize rododendrol glikozida katalizirane enzimima
No full textRhododendrol glycosides are found in birch bark and can serve as a starting substrate for the production of raspberry ketone, via a hydrolysis reaction by the enzyme glucosidase, producing the intermediates (R)- and (S)-rhododendrol, followed by oxidation to the desired product. Natural properties of raspberry ketone include its use in cosmetics and perfumes, its anti-inflammatory and antioxidant abilities, its ability to prevent cancer, and its ability to combat insulin resistance. In this study, β-glucosidase from almonds was used to facilitate the hydrolysis of rhododendrol glycoside (betuloside). Different types of reactors were used to carry out the reaction, including a batch, a repetitive batch and a continuous enzyme membrane reactor (EMR). The kinetics of the hydrolysis was described by single-substrate Michaelis-Menten kinetics. The reaction products, rhododendrol and glucose, were found to inhibit the reaction in a competitive manner. During the implementation of the process, deactivation of the enzyme occurred and was described by the second-order kinetics. A batch reactor and an EMR were used to set up and validate a mathematical model of the process. In batch reactors a conversion of 100% was achieved. The highest productivity and stability of the enzyme was obtained when the reaction was carried out in a continuous EMR.Glikozidi rododendrola nalaze se u kori breze i mogu djelovati kao početni supstrat za proizvodnju ketona maline, reakcijom hidrolize pomoću enzima glukozidaze koja proizvodi međuprodukte (R)- i (S)-rododendrola, nakon čega slijedi oksidacija do željenog produkta. Prirodna svojstva ketona maline uključuju njegovu upotrebu u kozmetici i parfemima, njihove protuupalne i antioksidativne sposobnosti, njihovu sposobnost sprječavanja raka, borbe protiv inzulinske rezistencije. U ovom diplomskom radu, β-glukozidaza iz badema korištena je za kataliziranje reakcije hidrolize rododendrol glikozida (betulozida) pri čemu nastaju dva enantiomera rododendrola. Za provođenje reakcije korišteni su različiti tipovi reaktora, uključujući kotlasti reaktor, ponovljivi kotlasti reaktor i kontinuirani enzimski membranski reaktor (EMR). Kinetika reakcije je opisana jednosupstratnom Michaelis-Menten kinetikom. Utvrđeno je da produkti reakcije, rododendrol i glukoza, inhibiraju reakciju na kompetitivni način. Prilikom provedbe procesa uočena je deaktivacija enzima koja je opisana kinetikom drugog reda. Kotlasti reaktor i EMR korišteni su za postavljanje i validaciju matematičkog modela procesa. U kotlastim reaktorima dobivena je konverzija supstrata od 100%. Najveća produktivnost i stabilnost enzima postignuta je prilikom provođenja reakcije u kontinuiranom EMR
Influence of process conditions on the photodegradation of imidacloprid
No full textNaglim porastom broja stanovništva te razvojem industrije dolazi do sve većeg onečišćenja voda, ali i drugih sastavnica okoliša. Zbog sve većih potreba za hranom potrebno je osigurati sredstva koja će pomoći pri očuvanju kvantitete i kvalitete usjeva u poljoprivredi. Iz tog razloga svjedoci smo sve češćoj upotrebi pesticida. S obzirom da je onečišćenje okoliša poprimilo velike razmjere, pred čovječanstvo je stavljen izazov suzbijanja kako pesticida, tako i ostalih vrsta onečišćenja. U tu svrhu znanost i struka ulažu maksimalne napore u razvoj naprednih oksidacijskih procesa, među kojima se posebno ističe fotokatalitička razgradnja kao inovativno rješenje. Fotokatalitička razgradnja je proces koji se, na temelju iskustva, odlikuje visokom učinkovitošću degradacije raznovrsnih organski spojeva, a isto tako je bitno napomenuti da njome nastaju minimalne količine nusprodukata štetnih za okoliš. U teorijskom dijelu rada bit će nešto više rečeno o samim pesticidima i njihovim štetnim utjecajima. Nadalje, detaljno će biti predstavljen fotokatalitički proces s primjenom TiO2 kao fotokatalizatora uz posebni naglasak na procesne uvjete koji utječu na sam proces. Cilj ovog rada bio je ispitati kako pojedini parametri utječu na fotorazgradnju neonikotinoida imidakloprida u vodenom mediju. Putem statističko planiranje, odnosno eksperimentalnog plana, sustav je postavljen na način da se mijenjaju tri varijable: pH, izvor zračenja i tip oksidansa. U ovom radu bit će opisan eksperimentalni postupak, uvjeti rada i korištene analitičke metode, kao i dobiveni rezultati potkrijepljeni objašnjenjima, grafičkim prikazima i tablicama. Za kraj bit će dan zaključak koji će predstavljati kratki rezime cijelog rada, kao i koji parametri imaju najveći utjecaj na fotorazgradnju.The sudden increase in population and the development of industry lead to increasing pollution of water and other components of the environment. Because of the growing demand for food, it is necessary to provide means to help maintain the quantity and quality of agricultural crops. For this reason, pesticides are being used with increasing frequency. As environmental pollution has reached great proportions, mankind is faced with the challenge of combating both pesticides and other types of pollution. To this end, science and practice are investing utmost efforts in developing advanced oxidation processes, among which photocatalytic decomposition stands out as an innovative solution. Photocatalytic decomposition is a process that, according to experience, is characterized by a high efficiency of degradation of various organic compounds, producing only small amounts of environmentally harmful by-products. In the theoretical part of the paper, some more is said about the pesticides themselves and their harmful effects. In addition, the photocatalytic process using TiO2 as a photocatalyst is presented in detail, with a special emphasis on the process conditions that influence the process itself. The aim of this work was to investigate how certain parameters affect the photodegradation of the neonicotinoid imidacloprid in an aqueous medium. Through statistical design, i.e., the experimental design, the system is set up to change three variables: pH, radiation source, and type of oxidant. In this paper, the experimental procedure, the working conditions and the analytical methods used, as well as the results obtained, are described and supplemented with explanations, graphical representations and tables. At the end, a conclusion is drawn, which is a brief summary of the whole work, and it is shown which parameters have the greatest influence on photodegradation
Membrane distillation - application in practice
No full textMembranska destilacija (MD) je neizotermna membranska tehnologija koja je sve više dolazi do izražaja u odnosu na klasičnu destilaciju. U radu je prikazan razvoj ove separacijske tehnologije, mehanizam procesa MD, vrste membrana za MD, moduli MD te primjena u praksi. Razlika tlaka glavna je pokretačka sila MD stoga su razvijena četiri glavna modula ove separacijske metode: membranska destilacija direktnog kontakta (DCMD), membranska destilacija s pročišćavajućim plinom (SGMD), membranska destilacija sa zračnim razmakom (AGMD) i vakuumska membranska destilacija (VMD). Za proces MD koriste se hidrofobne mikroporozne membrane najčešće od poli(tetrafluoretilena) (PTFE), polipropilena (PP) i poli(viniliden-fluorida) (PVDF) kako bi se spriječilo vlaženje membrane. U radu su također objašnjeni fenomeni vlaženja membrane, tlaka prodiranja i ravnoteže para - kapljevina kao i fenomeni prijenosa tvari i topline kroz membranu. Primjene MD su najčešće u desalinaciji morske i bočate vode, separaciji molekula poput amonijaka i aromatskih spojeva kao i iona teških metala. Također MD je našla svoju primjenu i u koncentraciji vodenih otopina.
Zbog lake integracije MD sustava u druge separacijske pogone moguće je ostvariti zadovoljavajuće rezultate poput smanjenja koncentrata.Membrane distillation (MD) is a non-isothermal membrane technology that is increasingly gaining prominence compared to classical distillation. The work presents the development of this separation technology, the mechanism of the MD process, types of MD membranes, MD modules and practical application. The pressure difference is the main driving force of MD, therefore four main modules of this separation method were developed: direct contact membrane distillation (DCMD), sweeping gas membrane distillation (SGMD), air gap membrane distillation (AGMD) and vacuum membrane distillation (VMD). For the MD process itself, hydrophobic microporous membranes are used, usually made of poly(tetrafluoroethylene) (PTFE), polypropylene (PP) and poly(vinylidene-fluoride) (PVDF) in order to prevent wetting of the membrane. The work also explains the phenomena of membrane wetting, penetration pressure and vapor-liquid equilibrium, as well as the phenomena of mass and heat transfer through the membrane. Applications of MD are the most common in desalination of sea and brackish water, separation of molecules such as ammonia and aromatic compounds as well as heavy metal ions. MD also found its application in the concentration of aqueous solutions. Due to the easy integration of the MD system into other separation plants, it is possible to achieve satisfactory results such as the reduction of concentrate
Influence of matrix composition on quantitative chromatographic determination of N-nitrosoamines
No full textDanas je čista voda jedan od najvrjednijih resursa na svijetu. Za osiguravanje zdravstveno ispravne vode provode se različiti postupci obrade vode, a neizostavan korak pri tome je dezinfekcija vode. Postupak dezinfekcije najčešće se provodi upotrebom klora. Primarni cilj dezinfekcije je uništavanje patogena, ali pritom može doći do nastanka dezinfekcijskih nusprodukata koji štetno utječu na ljudsko zdravlje. N-nitrozamini su spojevi koji spadaju u dezinfekcijske nusprodukte, a sve više pažnje privlače zbog svoje toksičnosti i kancerogenog djelovanja pri niskim koncentracijama. U vodi, N-nitrozamini, najviše nastaju prilikom upotrebe kloramina kao dezinfekcijskog sredstva. N-nitrozamini se u okolišu nalaze u vrlo niskim koncentracijama pa je cilj ovog rada ispitati utjecaj matrice uzorka na kvantitativno kromatografsko određivanje N-nitrozamina. U radu su korišteni uzorci sintetske bazenske, sintetske bočate i vodovodne vode. Ispitivanja su provedena sa smjesom sedam
N-nitrozamina: N, N-dibutilnitrozni amid (NDBA), N, N-dietilnitrozni amid (NDEA),
N, N-dimetilnitrozni amid (NDMA), N,N-dipropilnitrozni amid (NDPA), 4-nitrozomorfolin (NMOR), 1-nitrozopiperidin (NPIP) i 1-nitrozopirolidin (NPYR). Svi uzorci analizirani su tekućinskom kromatografijom visoke djelotvornosti s detektorom s nizom dioda (HPLC-DAD), a prije same HPLC analize uzorci su pripremljeni primjenom postupka ekstrakcije čvrstom fazom (SPE).
Za sve matrice određena je učinkovitost ekstrakcije čvrstom fazom, ponovljivost te linearno područje metode.Today, clean water is one of the most valuable resources in the world. Various water treatment processes are implemented to ensure safe drinking water and disinfection is an essential step in this process. The disinfection procedure is most commonly carried out using chlorine. The primary goal of disinfection is to eliminate pathogens, but during this process, disinfection by-products that adversely affect human health may be formed. N-nitrosamines are compounds that fall into the category of disinfection by-products, attracting increasing attention due to their toxicity and carcinogenic effects at low concentrations. In water,
N-nitrosamines primarily form during the use of chloramines as disinfectants. N-nitrosamines are found in the environment in very low concentrations and the aim of this study is to examine the influence of matrix composition on the quantitative chromatographic determination of N-nitrosamines. The work utilized samples of synthetic pool water, synthetic brackish water and tap water. The investigations were conducted on a mixture of seven
N-nitrosamines: N, N-dibutylnitrous amide (NDBA), N, N-diethylnitrous amide (NDEA),
N, N-dimethylnitrous amide (NDMA), N, N-dipropylnitrous amide (NDPA), 4-nitrosomorpholine (NMOR), 1-nitrosopiperidine (NPIP) and 1-nitrosopyrrolidine (NPYR). All samples were analyzed using high-performance liquid chromatography with a diode array detector
(HPLC-DAD). Prior to the HPLC analysis, samples were prepared using the solid-phase extraction (SPE) method. The efficiency of solid-phase extraction was determined for all matrices, and the repeatability and linearity of the method were determined
Mikrosfere na temelju kitozana kao sustavi za dostavu lijeka
No full textOsteosarcomas, the most common type of primary bone tumor affecting children, adolescents, and young people, usually occur in long bones and are treated with surgery, which is preceded by biopsy and chemotherapy. Chemotherapy is often continued after surgery. Since antitumor drugs are administered intravenously, very high concentrations are required to inhibit tumor cell growth, exposing the entire body to the effects of the drug. Additionally, conventional chemotherapeutic drugs often have drawbacks, including reduced solubility, nonselective distribution, and adverse effects after oral or intravenous administration, which limit their clinical use. To reduce these negative effects, chitosan (CHT)-based drug delivery systems for local delivery have been proposed. In this study, microspheres based on chitosan physically crosslinked with copper(II) ions (CHT-Cu complex) were successfully prepared by emulsion and electrohydrodynamic atomization (electrospraying) process. Additionally, composite microspheres with calcium phosphate (CaP) ceramics in varying amounts (0, 5, and 10 wt.% of CaPs) were prepared. The emulsion-prepared CHT-Cu/CaP0 microspheres (microspheres without the addition of CaP) were spherical (circularity factor ~1) with a smooth surface and an average size of 30.1 ± 9.1 μm. The size of the electrosprayed microspheres ranged from 50 to 110 μm, depending on the CaP content. FTIR spectroscopy and X-ray diffraction analysis indicated interactions between the CHT-Cu matrix and the precipitated CaP filler, likely in the form of hydroxyapatite. An in vitro Cu2+ release study performed under conditions simulating an in vivo-like physiological environment indicated a significantly higher metal release from the microspheres in a complete cell culture medium compared to phosphate buffer at pH 7.4. Doxorubicin (DOX), used as a model antitumor drug, was incorporated into the CHT-Cu/CaP microspheres utilizing the pH-sensitivity of the CHT matrix. Successful drug loading was confirmed by fluorescence microscopy. DOX release was shown to depend on the pH value and chemical composition of the incubation medium, as well as the chemical composition of the drug-loaded microcarrier, indicating the ability of the DOX-loaded microcarriers to locally release DOX in a pH-triggered manner. It can be assumed that modification of CHT-based microspheres by adding CaPs increased the DOX loading efficiency. Biological evaluation of the as-prepared and drug-loaded microcarriers indicated synergistic effect of the drug and Cu2+ ions, and material selectivity towards MG-63 tumor cells. The optimal DOX-loaded material concentration for inhibiting osteosarcoma cell growth without having a harmful effect on normal cells was 0.5 mg mL^–1. Overall, the physicochemical and biological characterization of the prepared CHT-Cu/CaP microspheres and DOX-loaded microcarriers indicated the successful preparation of smart drug delivery systems for bone tumor treatment.Osteosarkomi, najčešća vrsta primarnog tumora (dugih) kostiju koji se javlja kod djece, adolescenata i mladih ljudi, obično se liječe kirurškim zahvatom, kojem prethode biopsija i kemoterapija. Kemoterapija se često nastavlja i nakon operacije. Budući da se antitumorski lijekovi administriraju intravenozno, potrebne su vrlo visoke koncentracije za inhibiciju rasta tumorskih stanica, a čime se cijelo tijelo izlaže djelovanju lijeka. Nadalje, konvencionalni kemoterapijski lijekovi često imaju štetne učinke, kao što su smanjena topljivost i neselektivna distribucija, što ograničava njihovu kliničku primjenu. Kako bi se smanjili ovi negativni učinci, predloženi su sustavi za lokalnu dostavu lijeka koji se temelje na kitozanu (CHT). U ovom radu, mikrosfere na temelju kitozana fizikalno umreženoga s bakrovim(II) ionima (CHT-Cu kompleks) uspješno su dobivene postupkom iz emulzije i primjenom elektrohidrodinamičke atomizacije (EHDA proces, elektroštrcanje). Dodatno su pripremljene i kompozitne mikrosfere s kalcij-fosfatnom (CaP) keramikom u različitim masenim udjelima (0, 5 i 10 mas.%).
CHT-Cu/CaP0 mikrosfere (mikrosfere bez dodatka CaP) dobivene iz emulzije bile su sferične (faktor sferičnosti ~1) s glatkom površinom i prosječnom veličinom od 30,1 ± 9,1 μm. Prosječna veličina CHT-Cu/CaP mikrosfera dobivenih EHDA procesom bila je između
50 i 110 μm, ovisno o količini CaP punila. FTIR spektroskopija i XRD analiza ukazale su na prisutnost interakcija između CHT-Cu matrice i istaloženoga CaP punila, vjerojatno u obliku hidroksiapatita. Otpuštanje Cu2+ iona iz CHT-Cu/CaP0 mikrosfera istraženo je pri simuliranim fiziološkim uvjetima, te rezultati ukazuju na znatno veće otpuštanje metalnih iona u mediju za staničnu kulturu u odnosu na fosfatni pufer pH vrijednosti 7,4. Doksorubicin (DOX), korišten kao modelni antitumorski lijek, uklopljen je u CHT-Cu/CaP mikrosfere koristeći svojstvo
pH-osjetljivosti CHT matrice. Uspješno uklapanje lijeka u mikronosače potvrđeno je primjenom fluorescentne mikroskopije. Otpuštanje DOX-a iz mikronosača ovisi o pH-vrijednosti i sastavu medija za inkubaciju, te o kemijskom sastavu mikronosača, što ukazuje na to da su
DOX-mikronosači pH-osjetljivi. Također, može se pretpostaviti da je modifikacija CHT-Cu mikrosfera dodatkom CaP-a povećala učinkovitost uklapanja DOX-a. Biološka ispitivanja pripremljenih CHT-Cu/CaP mikrosfera i mikronosača s uklopljenim lijekom pokazala su sinergijski učinak lijeka i Cu2+ iona te selektivnost materijala prema tumorskim stanicama. Kao optimalna koncentracija materijala s DOX-om za inhibiciju rasta stanica osteosarkoma bez štetnog učinka na zdrave stanice pokazala se 0,5 mg mL^–1. Zaključno, fizikalno-kemijska i biološka karakterizacija pripremljenih CHT-Cu/CaP mikrosfera i mikronosača s uklopljenim DOX-om ukazala je na uspješnu pripremu pametnih sustava za isporuku lijekova za liječenje tumora kostiju
Geothermal sources and their influence on the environment
No full textGeotermalna energija ubraja se u obnovljive izvore energije čija je količina neograničena. Njena nalazišta su u brojnim zemljama diljem svijeta i koristi se za dobivanje električne energije ili direktno korištenje toplinske energije. Geotermalna energija ne može se prenositi na veće udaljenosti nego se grade geotermalne elektrane kako bi njenu energiju pretvorili u koristan oblik energije. Postoje različiti načini iskorištavanja geotermalnih izvora energija, te njihove prednosti i nedostatci. Iako je ima u neograničenim količinama, njeno korištenje zahtjeva veliku investiciju, ali je zato ekonomičnija od korištenja fosilnih goriva kao energenata. Iskorištena geotermalna energija može se koristiti za različita područja kao što su rehabilitacijske svrhe, industrija, poljoprivredno sušenje, geotermalne dizalice topline, zagrijavanje individualnih objekata i u centralnom toplinskom sustavu koji zagrijava neko veće okruženje koje je blizu geotermalne elektrane. Republika Hrvatska je država u kojoj se nalazi u Europi najveća geotermalna elektrana imena „Velika 1”. Glavni nedostatak geotermalnih izvora energije je taj što se geotermalna elektrana mora izgraditi na mjestu gdje se nalazi geotermalni izvor što ujedno može utjecati i na izgradnju geotermalne elektrane ako je sam izvor na zemljišno nepravilnoj površini.Geothermal energy belongs to the renewable energy sources whose quantity is unlimited. Its deposits are in numerous countries worldwide and it is used to produce electricity or for direct use from thermal energy. Geothermal energy cannot be transmitted over long distances so the geothermal power plants must be built near the geothermal source of energy whose function will be to use that energy to convert it to useful form of energy. There are different ways of exploiting geothermal energy and they also have their advantages and disadvantages. Although it is available in unlimited quantities, its use requires a large investment, but it is therefore more economical than the use of fossil fuels as energy sources. Exploited geothermal energy is used for various area as such as rehabilitation purposes, industry, agricultural drying, geothermal heat pumps, space heating and in central heating system which is used for district heating. The Republic of Croatia is the country where Europe’s largest geothermal power plant „Velika 1” is located. Main disadvantage of geothermal energy sources is that geothermal power plants must be built where those sources are located which can also affect the construction of the geothermal power plant if the source itself is on an irregular surface
Forced degradation of sofosbuvir and oseltamivir
No full textKroz posljednjih nekoliko desetljeća u području istraživanja i zaštite okoliša sve više pozornosti se pridaje takozvanim "novim onečišćujućim tvarima". Pojam "nove onečišćujuće tvari" obuhvaća sve one spojeve i tvari kojima se do nedavno nije pridavalo značenje kao ksenobioticima, a danas se sve više ispuštaju u okoliš u značajnijim količinama koje predstavljaju opasnost za okoliš. Jednu od najvažnijih skupina predstavljaju farmaceutici i sredstva za osobnu higijenu i njegu zbog toga što sadrže veliki broj različitih kemijskih spojeva koji imaju različit utjecaj na okoliš u koji se ispuštaju. U ovom radu ispitano je ponašanje i stabilnost dvaju farmaceutika, 0,1 mM otopina sofosbuvira i oseltamivira provođenjem testova prisilne razgradnje: a) lužnate hidrolize u prisutnosti 1,0 M otopine NaOH na sobnoj temperaturi tijekom 24 sata, b) kisele hidrolize u prisutnosti 1,0 M otopine HCl na sobnoj temperaturi tijekom 24 sata, c) oksidacije u prisutnosti 30%-tne otopine H2O2 pri sobnoj temperaturi tijekom 24 sata, d) termičke razgradnje (neutralne hidrolize) pri sobnoj temperaturi, 30 i 40 °C tijekom 168 sati (7 dana) i e) fotolitičke razgradnje djelovanjem UV svjetlosti jačine 600 W/m^2 pri 25 °C tijekom 6 sati. Analize svih izuzetih uzoraka provodile su se na HPLC-u gdje su za oba farmaceutika prethodno razvijene i validirane metode određivanja. Na temelju dobivenih rezultata validacije, obje metode zadovoljavaju zahtjeve prema svim parametrima: linearnost s koeficijentom determinacije većim od 0,99, točnost s vrijednostima analitičkog povrata između 70 i 130% te preciznost s RSD vrijednostima manjima od 10%. S obzirom na ispitivanja prisilne razgradnje može se zaključiti da su sofosbuvir i oseltamivir zadovoljavajuće i očekivane stabilnosti pri svim ispitanim uvjetima.In recent decades, the so-called "new pollutants" have received increasing attention in the field of research and environmental protection. The term "new pollutants" includes all those compounds and substances that until recently were not considered xenobiotics and are now increasingly entering the environment in significant quantities and therefore posing a threat to the environment. One of the most important groups is pharmaceuticals and personal care products, as they contain a large number of different chemical compounds that have different effects on the environment into which they are released. In this work, the behavior and stability of two drugs, 0.1 mM solutions of sofosbuvir and oseltamivir, were tested by forced degradation tests: a) alkaline hydrolysis in the presence of a 1.0 M NaOH solution at room temperature for a period of 24 h, b) acid hydrolysis in the presence of a 1.0 M HCl solution at room temperature over a 24-hour period, c) oxidation in the presence of a 30% H2O2 solution at room temperature over a 24-hour period, d) thermal decomposition (neutral hydrolysis) at room temperature, 30 °C, and 40 °C over 168 hours (7 days), and e) photolytic decomposition exposed to UV light at 600 W/m^2 at 25°C over a 6-hour period. Analyses of all excluded samples were performed by HPLC, and the determination methods for both drugs were previously developed and validated. Based on the validation results obtained, both methods met the requirements for all parameters: Linearity with coefficient of determination higher than 0.99, Accuracy with analytical recoveries between 70 and 130%, and Precision with RSD values lower than 10%. Regarding the forced degradation tests, it can be concluded that sofosbuvir and oseltamivir showed satisfactory and expected stability under all tested conditions
Emission of carbon(IV) oxide in the combustion of fossil fuels
No full textFosilna goriva, ugljen, nafta i prirodni plin u svakidašnjoj su upotrebi kao osnovni izvori energije u kućanstvu, industriji, prometu. Fosilna su goriva veliki zagađivači okoliša zbog štetnih plinova koji nastaju njihovim izgaranjem, s naglaskom na ugljikov(IV) oksid. Emitiranjem Sunčeve energije, dio se energije reflektira od Zemljine površine, a zbog učinka staklenika dolazi do zadržavanja te energije u atmosferi. Zadržavanjem energije dolazi do zatopljenja planeta. Ugljikov(IV) oksid vodeći je staklenički plin čije se količine emisija eksponencijalno povećavaju. Zbog njegovih povećanih emisija dolazi do pretjeranog zagrijavanja planeta, što je glavni uzrok globalnog zatopljenja. Katalitički konverteri uređaji su kojima je cilj smanjiti emisije štetnih ispušnih plinova iz motora automobila. Pretvorbom tih plinova nastaje ugljikov(IV) oksid, koji, iako manje štetan, i dalje loše utječe na okoliš. Postoje različite metode kojima se pokušavaju pratiti trendovi emisija ugljikova(IV) oksida, kao što je modeliranje jednadžbi. Cilj korištenja tih metoda jest pretpostaviti emisije u budućnosti kako bi se mogao smanjiti njihov štetan utjecaj.Fossil fuels, coal, oil and natural gas are used in everyday life as the main sources of energy in households, industry and transport. Fossil fuels are major environmental pollutans due to the harmful gases produces by their combustion, with an emphasis on carbon(IV) oxide. By emitting solar energy, some of the energy is reflected from the Earth's surface, and due to the greenhouse effect, this energy is retained in the atmosphere. Retaining energy leads to warming of the planet. Carbon(IV) oxide is the leading greenhouse gas whose emissions are increasing exponentally. Due to its grincreased emissions, the planet is overheating, which is the main cause of global warning. Catalytic converters are devices that aim to reduce harmful exhaust emissions from car engines. The conversion of these gases produces carbon(IV) oxide, which, although less harmful, still has a bad effect on the environment. There are various methods that try to monitor trends in carbon(IV) oxide emissions, such as equation modeling. The goal of using these methods is to predict emissions in the future in order to reduce their harmful impact
Protective properties of organic coatings containing graphene oxide
No full textCilj ovog diplomskog rada je ispitati mogućnost primjene grafenova oksida (GO) i reduciranog grafenova oksida (rGO) kao punila u zaštitnom akrilatnom premazu za očuvanje brončane kulturne baštine. Eksperimentalni dio rada uključivao je pripremu kompozitnih premaza uz dodatak GO ili rGO. Svojstva premazom zaštićenih brončanih površina ispitana su izlaganjem uzoraka otopini kisele kiše, jer je ona jedan od najvećih čimbenika degradacije metala u industrijskim i urbanim sredinama. Izlaganje uzoraka umjetnoj otopini kisele kiše se provodila kroz dva tjedna. Ispitivanja korozijske zaštite premaza su se provodila elektrokemijskim korozijskim ispitivanjima, uključujući linearnu polarizaciju i elektrokemijsku impedancijsku spektroskopiju (EIS). Uz to, provedena su i ispitivanja metodama karakterizacije površine uzoraka uključujući Fourierovu transformacijsku infracrvenom spektroskopiju (FTIR) i optičku mikroskopiju. Dobiveni rezultati pokazuju da GO nije poboljšao zaštitna svojstva ispitivanog premaza Paraloid B72, dok premaz sa rGO dobivenim elektrokemijskom redukcijom GO, pokazuje bolju stabilnost u vremenu u odnosu na nemodificirani premaz.The aim of this work is to investigate the potential application of graphene oxide (GO) and reduced graphene oxide (rGO) as fillers in a protective acrylic coating for the preservation of bronze cultural heritage. The experimental part of the work included the preparation of composite coatings with the addition of GO or rGO. The properties of the coated bronze surfaces were examined by exposing the samples to an acid rain solution, as acid rain is one of the major factors contributing to metal degradation in industrial and urban environments. The samples were exposed to the artificial acid rain solution for a period of two weeks. Corrosion protection properties of studied coatings were evaluated using electrochemical corrosion tests, including linear polarization and electrochemical impedance spectroscopy (EIS). In addition, surface characterization techniques were employed, including Fourier-transform infrared spectroscopy (FTIR) and optical microscopy. The obtained results show that GO did not improve the protective properties of the tested Paraloid B72 coating, while the coating containing rGO obtained by electrochemical reduction of GO demonstrated better long-term stability compared to the unmodified coating
The modeling of oxygen isotope separation by cryogenic air distillation
No full textVoda obogaćena izotopom kisika-18 ključna je sirovina za proizvodnju 18F-obilježenih spojeva koji se koriste u pozitronskoj emisijskoj tomografiji (PET), gdje je potrebna visoka izotopska obogaćenost (>98 at.%). Budući da je kisik-18 u prirodi vrlo rijedak i pokazuje minimalne fizikalne razlike u odnosu na ostale izotope kisika, njegova industrijska separacija predstavlja značajne tehničke i ekonomske izazove. Konvencionalne metode, poput destilacije vode ili dušikovih oksida, često su energetski zahtjevne ili sigurnosno upitne. U ovom radu modeliran je i simuliran proces separacije izotopa 18O iz zraka pomoću kriogene destilacije kisika, upotrebom programskih paketa ChemCAD i Aspen HYSYS. Simulirani proces uključuje kaskadu od deset detaljno modeliranih destilacijskih kolona koje predstavljaju tri glavne faze separacije s ukupno 6570 teorijskih stupnjeva. Uvođenjem unutarnjih povratnih tokova, postignuta je čistoća produkta od 98 mol% kisika-18 te ukupni iscrpak od 55%. Rezultati simulacije pokazali su uspješnu separaciju izotopa te dodatno smanjenje energetske potrošnje za 8% segmentacijom prve kolone. Ipak, proces ostaje izrazito energetski zahtjevan i kapitalno intenzivan zbog kompleksnosti i potrebe za održavanjem kriogenih uvjeta (98 at.%) is required. As oxgen-18 is naturally scarce and exhibits minimal physical separation factors from other isotopes, its industrial-scale enrichment presents significant technical and economic challenges. Conventional separation methods include water or nitric oxide distillation, both of which suffer from high energy consumption or safety limitations. This work presents the modeling and simulation of oxygen-18 isotope separation from air via cryogenic oxygen distillation using ChemCAD and Aspen HYSYS. The simulated process employs a cascade of ten rigorously modeled distillation columns representing three main separation stages, with a total of 6570 theoretical stages. With the implementation of internal reflux loops, the simulated process achieved a product purity of 98 mol% oxygen-18 and an overal yield of 55%. Simulation results demonstrated not only effective isotopic separation but also an 8% reduction in energy consumption through column segmentation strategies. Nevertheless, the process remains energetically intensive and economically demanding due to its complexity and the need to maintain cryogenic conditions below –180 °C. This study confirms that cryogenic oxygen distillation, despite its high capital and operational costs, remains the most viable route for large-scale oxygen-18 enrichment required in medical applications such as PET diagnostics