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Nuevos cocatalizadores compuestos a base de TiO2 para la purificación de agua impulsada por solar
No full textAccessible clean water is among the highest priorities for sustainable economic growth and societal wellbeing. Water supports life and is a crucial resource for humanity; it is also at the core of natural ecosystems and climate regulation. Water stress is primarily a water quantity issue, but it also occurs as a consequence of a deterioration of water quality and a lack of appropriate water management. Environmental problems that are associated with water pollution have been a persistently important issue over recent decades, correlated negatively with the health and ecosystem. The occurrence of trace amounts of antibiotics in various bodies of water was directly linked to the development of antibiotic resistant pathogens. Over the last two decades, penicillins have been widely prescribed and used across Europe. Recently, Amoxicillin (AMX) was added to the second and third EU “watch list” based on the Decision 2018/840/EU and 2020/1161/EU, respectively. Its presence in wastewater effluents is related to limited removal by common municipal wastewater treatment plants (WWTP's) based on primary (physical) and secondary (biological) treatment. Therefore, the new remediation techniques must be implemented within the water treatment train to remove such recalcitrant substances. Advanced oxidation processes (AOPs) have gained much research attention due to their innate ability to provide effective oxidation of a wide variety of organic pollutants persistent to conventional wastewater treatment methods. AOPs effectiveness rely on highly reactive and non-selective species, primarily hydroxyl radicals (HO•). Among various AOPs, semiconductor photocatalysis greatly attracts attention due to stability of the semiconductor material and potential to use abundant solar energy to degrade organic pollutants. The most widely investigated and employed photocatalyst in water purification is TiO2. However, TiO2 suffers from the fast recombination of photogenerated charges (i.e., electron/hole pairs; e-/h+) and is only active under UV light due its wide band gap (3.0-3.2 eV), thus hindering its potential for solar-driven applications. These deficiencies can be improved by the following strategies: doping with metals and/or non-metals, dye sensitization, incorporation with carbon nanotubes, reduced graphene oxide and coupling with other semiconductors with narrow band gaps. Coupling of TiO2 with narrow band gap semiconductors with visible light response may promote synergistic effects between two semiconducting materials leading to more efficient charge separation and high photocatalytic activity under visible light irradiation. Iron oxide (α-Fe2O3, also known as hematite) is a promising candidate for coupling with TiO2, due to its abundance, low cost, stability and visible light activity due to its narrow band gap (2.0–2.2 eV). Most importantly, suitable band-edge positions of hematite promote photogenerated charge separation in TiO2 via heterojunction transfer. Despite several photocatalytic applications of Fe2O3/TiO2 composites for the removal of contaminants of emerging concern (CECs), all studies investigated their applications in the suspension system (i.e., employing a powdered form of photocatalyst), while the application of immobilized Fe2O3/TiO2 composites are scarcely reported. Moreover, treatment of AMX under solar/visible light using Fe2O3/TiO2, as well as the ecotoxicity of AMX degradation/transformation by-products is rarely explored. In this dissertation, removal of AMX in pure water was investigated using sandwich-type Fe2O3/TiO2 layered films made of commercially available nanomaterials (Part 1) and using synthesized Fe2O3/TiO2 made of pure chemical precursors (Part 2). In part 1, sandwich-type composites made of commercial TiO2-P25 and α-Fe2O3 are obtained in a form of thin films by spin coating, possessing different layer configurations, namely: (i) TiO2 layer over α-Fe2O3 (TiO2@α-Fe2O3), (ii) α-Fe2O3 layer over TiO2 (α- Fe2O3@TiO2), and (iii) physically mixed 50% (w/w) of TiO2/Fe2O3. Photocatalytic activity under simulated solar irradiation of the aforementioned composites and their pure components is investigated for the degradation of AMX in the presence and absence of persulfate (PS). In both cases, TiO2@α-Fe2O3 sandwich-type achieved the highest degradation rates of AMX and a marked effect of PS addition on the AMX degradation rate is noted. The influence of pH and PS concentration on AMX degradation rate is established by means of experimental design and response surface modeling which revealed optimum conditions at [S2O82-] = 0.334 mM and pH = 4.0. The AMX degradation mechanisms and pathways are studied by means of reactive oxygen species scavenging and identification of intermediates by liquid chromatography with tandem mass spectrometry (LC-MS/MS), respectively. Evolution of formed intermediates is directly correlated with an increased toxicity assessed by Daphnia magna and Vibrio fischeri assays. Furthermore, biodegradability changes are correlated with the mineralization profile of AMX solution. The influence of water matrix constituents (Cl-, CO32-, NO3-, PO43- and Suwannee river natural organic matter) on AMX degradation is established as well. In part 2, Fe2O3/TiO2 nanocomposites were fabricated via a facile impregnation/calcination technique employing different amounts of iron (III) nitrate onto commercial TiO2 (P25 Aeroxide). The as-prepared Fe2O3/TiO2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDXS), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis (BET), electron impedance spectroscopy (EIS), photoluminescence spectroscopy (PL), and diffuse reflectance spectroscopy (DRS). The Fe2O3/TiO2 composite possessing 5% (w/w) of Fe2O3 showed the highest photocatalytic activity in the slurry system and was thereafter successfully immobilized on glass support. Photocatalytic activity under visible-light irradiation was assessed by treating AMX in the presence and absence of additional oxidants: hydrogen peroxide (H2O2) and PS. The influence of pH and PS concentration on AMX conversion rate was established by means of statistical planning and response surface modeling. Results revealed optimum conditions of [S2O82-] = 1.873 mM and pH = 4.808; these were also utilized in presence of H2O2 instead of PS in long-term tests. The fastest AMX conversion possessing a zero-order rate constant of 1.51 × 10^−7 M·min^-1 was achieved with the photocatalysis + PS system. The AMX conversion pathway was established, and the evolution/conversion of formed intermediates was correlated with the changes in toxicity toward Vibrio fischeri. Reactive oxygen species (ROS) scavenging was also utilized to investigate the AMX conversion mechanism, revealing the major contribution of photogenerated h+ in all processes.Dostupna čista voda jedan je od najvećih prioriteta za održivi gospodarski rast i društvenu dobrobit. Voda podržava život i ključni je resurs za čovječanstvo; također je u srži prirodnih ekosustava i regulacije klime. Vodeni stres prvenstveno je uzrokovan problemom količine vode, ali se javlja i kao posljedica pogoršanja kvalitete vode i nedostatka odgovarajućeg gospodarenja vodom. Problemi okoliša povezani s onečišćenjem vode važno su pitanje tijekom posljednjih desetljeća, te su u negativnoj korelaciji sa zdravljem i ekosustavom. Pojava tragova antibiotika u raznim vodama u okolišu izravno je povezana s razvojem patogena otpornih na antibiotike. Tijekom posljednja dva desetljeća penicilini su naširoko propisivani i korišteni diljem Europe. Nedavno je amoksicilin (AMX) dodan na drugi EU „popis za praćenje” na temelju Odluke Komisije (EU) 2018/840/EU. Njegova prisutnost u otpadnim vodama povezana je s ograničenim uklanjanjem na komunalnim uređajima za pročišćavanje otpadnih voda (UPOV) koji se temelje na primarnom (fizičkom) i sekundarnom (biološkom) pročišćavanju. Stoga se moraju primijeniti nove tehnike remedijacije za uklanjanje takvih tvari. Nedavno su napredni oksidacijski procesi (AOP) privukli veliku pažnju istraživanča jer osiguravaju učinkovitu oksidaciju širokog spektra organskih onečišćivala koja su otporna na konvencionalne metode obrade vode. Učinkovitost AOP-a oslanja se na visoko reaktivne i neselektivne vrste, prvenstveno hidroksilne radikale (HO•). Među raznim AOP-ima, fotokataliza uz korištenje poluvodičkih materijala uvelike privlači pozornost zbog stabilnosti primjenjenih fotokatalizatora i potencijala korištenja sunčeve energije za razgradnju organskih onečišćivala. Najviše istraživan i korišten fotokatalizator u pročišćavanju vode je TiO2. Međutim, nedostatak TiO2 je brza rekombinacija fotogeneriranih naboja (tj. parova elektron/šupljina; e-/h+) te je aktivan samo pod UV svjetlom zbog široke zabranjene zone (3,0-3,2 eV), čime se smanjuje njegov potencijal u primjeni uz sunčevo zračenje. Ovi nedostaci mogu se poboljšati sljedećim strategijama: dopiranjem metalima i/ili nemetalima, senzibilizacijom boje, ugradnjom ugljičnih nanocijevi, reduciranim grafen oksidom i spajanjem s drugim poluvodičima s uskim propusnim pojasima. Spajanje TiO2 s poluvodičima s uskim razmakom i odzivom na vidljivo svjetlo može pospješiti sinergističke učinke između dva poluvodička materijala što dovodi do učinkovitijeg odvajanja naboja i visoke fotokatalitičke aktivnosti pod zračenjem vidljivim svjetlom. Željezni oksid (α-Fe2O3, također poznat kao hematit) obećavajući je kandidat za spajanje s TiO2, zbog svoje zastupljenosti, niske cijene, stabilnosti i aktivnosti pod vidljivom svjetlosti zbog uske zabranjene zone (2,0–2,2 eV). Ono što je najvažnije, prikladni rubni položaji hematita promiču fotogenerirano odvajanje naboja u TiO2 putem prijenosa heterospojnice. Unatoč nekoliko fotokatalitičkih primjena kompozita Fe2O3/TiO2 za uklanjanje postojanih onečišćivala (engl, contaminants of emerging concern, CECs), sve te studije istraživale su njihovu primjenu u suspenziji (tj. upotrebom praškastog oblika fotokatalizatora), dok je primjena imobiliziranih kompozita Fe2O3/TiO2 vrlo rijetka. Štoviše, tretman AMX-a pod sunčevim/vidljivim svjetlom pomoću Fe2O3/TiO2, kao i ekotoksičnost nusproizvoda razgradnje/transformacije AMX-a rijetko se istražuje. U ovoj disertaciji, uklanjanje AMX-a istraženo je korištenjem slojevitih filmova Fe2O3/TiO2 sendvič tipa izrađenih od komercijalno dostupnih nanomaterijala (1. dio) i korištenjem sintetiziranog Fe2O3/TiO2 napravljenog od čistih kemijskih prekursora (2. dio). U dijelu 1, kompoziti sendvič tipa izrađeni od komercijalnog TiO2-P25 i α-Fe2O3 dobiveni su centrifugiranjem tankih filmova s različitim konfiguracijama slojeva: i) sloj TiO2 preko α-Fe2O3 (TiO2@Fe2O3), ii) α-Fe2O3 sloj preko TiO2 (α-Fe2O3@TiO2), i iii) fizički pomiješano 50% (w/w) TiO2/ Fe2O3. Fotokatalitička aktivnost pod simuliranim sunčevim zračenjem gore spomenutih kompozita i njihovih čistih komponenti istražena je kroz praćenje razgradnje amoksicilina (AMX) u prisutnosti i odsutnosti persulfata (PS). U oba slučaja, TiO2@α-Fe2O3 sendvič tip postigao je najviše stope razgradnje AMX-a i primjećuje se značajan učinak dodatka PS na stopu razgradnje AMX-a. Utjecaj pH i koncentracije PS na brzinu razgradnje AMX-a utvrđen je primjenom eksperimentalnog dizajna i modeliranja površine odziva kojima su određeni optimalni ujveti [S2O82-] = 0,334 mM i pH = 4,0. Put razgradnje AMX proučavao je pomoću uklanjanja reaktivnih kisikovih vrsta i identifikacije međuprodukata tekućinskom kromatografijom s tandemskom spektrometrijom mase (LC-MS/MS). Njihovo nastajanje je u izravnoj korelaciji s povećanom toksičnošću procijenjenom testovima Daphnia magna i Vibrio fischeri. Nadalje, promjene biorazgradljivosti povezane su s profilom mineralizacije AMX otopine. Utvrđen je i utjecaj sastojaka vodene matrice (Cl-, CO32-, NO3-, PO43- i prirodne organske tvari rijeke Suwannee) na razgradnju AMX-a. U 2. dijelu, nanokompoziti Fe2O3/TiO2 proizvedeni su jednostavnom tehnikom impregnacije/kalcinacije korištenjem različitih količina željezovog (III) nitrata na komercijalnom TiO2 (P25 aeroksid). Pripremljeni nanokompoziti Fe2O3/TiO2 karakterizirani su difrakcijom X-zraka (XRD), Ramanovom spektroskopijom (RS), skenirajućom elektronskom mikroskopijom/energetsko-disperzijom spektroskopije (SEM/EDXS), fotoelektronskom spektroskopijom X-zraka (XPS), Brunauer– Emmett-Tellerova analiza (BET), spektroskopija elektronske impedancije (EIS), fotoluminiscencijska spektroskopija (PL) i spektroskopija difuzne refleksije (DRS). Kao rezultat toga, 5% (w/w) Fe2O3/ TiO2 postigao je najveću fotokatalitičku aktivnost u suspenzijskom sustavu i uspješno je imobilizirano na staklenoj podlozi. Fotokatalitička aktivnost pod zračenjem vidljivim svjetlom procijenjena je tretiranjem farmaceutskog amoksicilina (AMX) u prisutnosti i odsutnosti dodatnih oksidansa: vodikovog peroksida (H2O2) i persulfatnih soli (PS). Utjecaj pH i koncentracije PS na stopu konverzije AMX utvrđen je pomoću statističkog planiranja i modeliranja površine odziva. Određeni su optimalni uvjeti [S2O82-] = 1,873 mM i pH = 4,808; oni su također korišteni u prisutnosti H2O2 umjesto PS u dugoročnim testovima. Najbrža AMX pretvorba s konstantom brzine nultog reda od 1,51 × 10^-7 M·min^-1 postignuta je sustavom fotokataliza + PS. Utvrđen je put pretvorbe AMX, a evolucija/pretvorba nastalih međuprodukata povezana je s promjenama toksičnosti prema Vibrio fischeri. Uklanjanje reaktivnih kisikovih vrsta (ROS) također je korišteno za istraživanje mehanizma pretvorbe AMX, otkrivajući glavni doprinos fotogeneriranog h+ u svim procesima.El agua limpia accesible es una de las principales prioridades para el crecimiento económico sostenible y el bienestar social. El agua sustenta la vida y es un recurso crucial para la humanidad; también está en el centro de los ecosistemas naturales y la regulación del clima. El estrés hídrico es principalmente un problema de cantidad de agua, pero también ocurre como consecuencia del deterioro de la calidad del agua y la falta de una gestión adecuada del agua. Los problemas ambientales asociados con la contaminación del agua han sido un problema persistentemente importante en las últimas décadas, correlacionados negativamente con la salud y el ecosistema. La aparición de cantidades mínimas de antibióticos en varios cuerpos de agua estuvo directamente relacionada con el desarrollo de patógenos resistentes a los antibióticos. Durante las últimas dos décadas, las penicilinas se han recetado y utilizado ampliamente en toda Europa. Recientemente, la amoxicilina (AMX) se agregó a la segunda "lista de vigilancia" de la UE con base en la Decisión Europea propuesta 2018/840/EU. Su presencia en los efluentes de aguas residuales está relacionada con la eliminación limitada por parte de las plantas de tratamiento de aguas residuales (PTAR) comunes municipales basadas en el tratamiento primario (físico) y secundario (biológico). Por lo tanto, las nuevas técnicas de remediación deben aplicarse para eliminar dichas sustancias recalcitrantes. Recientemente, los procesos de oxidación avanzada (POA) han ganado mucha atención en la investigación debido a su capacidad innata para proporcionar una oxidación eficaz de una amplia variedad de contaminantes orgánicos persistentes en los métodos de tratamiento de aguas residuales convencionales. La eficacia de los AOP se basa en especies altamente reactivas y no selectivas, principalmente basadas en radicales hidroxilo (HO•). Entre varios AOP, la fotocatálisis de semiconductores atrae mucho la atención debido a la estabilidad del material semiconductor y el potencial para usar abundante energía solar para degradar contaminantes orgánicos. El fotocatalizador más ampliamente investigado y empleado en la purificación del agua es el TiO2. Sin embargo, el TiO2 sufre la rápida recombinación de las cargas fotogeneradas (es decir, pares de electrones/huecos; e-/h+) y solo es activo bajo la luz ultravioleta debido a su ancho de banda prohibida (3,0-3,2 eV), lo que dificulta su potencial para aplicaciones impulsadas por energía solar. Estas deficiencias se pueden mejorar mediante las siguientes estrategias: dopaje con metales y/o no metales, sensibilización de colorantes, incorporación con nanotubos de carbono, óxido de grafeno reducido y acoplamiento con otros semiconductores con bandas prohibidas estrechas. El acoplamiento de TiO2 con semiconductores de banda estrecha con respuesta de luz visible puede promover efectos sinérgicos entre dos materiales semiconductores que conducen a una separación de carga más eficiente y una alta actividad fotocatalítica bajo la irradiación de luz visible. El óxido de hierro (α-Fe2O3, también conocido como hematita) es un candidato prometedor para el acoplamiento con TiO2, debido a su abundancia, bajo costo, estabilidad y actividad de luz visible debido a su estrecha banda prohibida (2.0–2.2 eV). Lo que es más importante, las posiciones adecuadas del borde de la banda de hematita promueven la separación de carga fotogenerada en TiO2 a través de la transferencia de heterounión. A pesar de varias aplicaciones fotocatalíticas de los compuestos de Fe2O3/TiO2 para la eliminación de contaminantes emergentes (CEC), todos los estudios investigaron sus aplicaciones en la suspensión (es decir, empleando una forma de fotocatalizador en polvo), mientras que la aplicación de compuestos de Fe2O3/TiO2 inmovilizados es escasamente conocida. Informado. Además, rara vez se explora el tratamiento de AMX bajo luz solar/visible usando Fe2O3/TiO2, así como la ecotoxicidad de los subproductos de degradación/transformación de AMX. En esta disertación, se investigó la eliminación de AMX usando películas en capas tipo sándwich de Fe2O3/TiO2 hechas de nanomateriales disponibles comercialmente (Parte 1) y usando Fe2O3/TiO2 sintetizado hecho de precursores químicos puros (Parte 2). En la parte 1, se obtienen compuestos tipo sándwich hechos de TiO2-P25 y α- Fe2O3 comerciales mediante recubrimiento por rotación de películas delgadas con diferentes configuraciones de capa, a saber: i) capa de TiO2 sobre α- Fe2O3 (TiO2@α-Fe2O3), ii) capa de α-Fe2O3 sobre TiO2 (α-Fe2O3@TiO2), y iii) mezclado físicamente al 50 % (p/p) de TiO2/ Fe2O3. Se investiga la actividad fotocatalítica bajo irradiación solar simulada de los compuestos antes mencionados y sus componentes puros para la degradación de amoxicilina (AMX) en presencia y ausencia de persulfato (PS). En ambos casos, el tipo sándwich de TiO2@α-Fe2O3 logró las tasas de degradación más altas de AMX y se observa un marcado efecto de la adición de PS en la tasa de degradación de AMX. La influencia del pH y la concentración de PS en la tasa de degradación de AMX se establece mediante un diseño experimental y un modelo de superficie de respuesta que reveló condiciones óptimas de [S2O82−] = 0,334 mM y pH = 4,0. La ruta de degradación de AMX se estudia mediante la eliminación de especies reactivas de oxígeno y la identificación de intermediarios mediante cromatografía líquida con espectrometría de masas en tándem (LC-MS/MS). Su evolución está directamente relacionada con una mayor toxicidad evaluada por los ensayos de Daphnia magna y Vibrio fischeri. Además, los cambios de biodegradabilidad están correlacionados con el perfil de mineralización de la solución AMX. También se establece la influencia de los componentes de la matriz del agua (Cl−, CO32−, NO3−, PO43− y la materia orgánica natural del río Suwannee) en la degradación de AMX. En la parte 2, se fabricaron nanocompuestos de Fe2O3/TiO2 mediante una sencilla técnica de impregnación/calcinación empleando diferentes cantidades de nitrato de hierro (III) sobre TiO2 comercial (aeróxido P25). Los nanocompuestos de Fe2O3/TiO2 preparados se caracterizaron mediante difracción de rayos X (XRD), espectroscopia Raman (RS), microscopia electrónica de barrido/espectroscopia de dispersión de energía (SEM/EDXS), espectroscopia de fotoelectrones de rayos X (XPS), Brunauer– Análisis de Emmett-Teller (BET), espectroscopia de impedancia de electrones (EIS), espectroscopia de fotoluminiscencia (PL) y espectroscopia de reflectancia difusa (DRS). Como resultado, el 5 % (p/p) de Fe2O3/ TiO2 logró la actividad fotocatalítica más alta en el sistema de suspensión y se inmovilizó con éxito en un soporte de vidrio. La actividad fotocatalítica bajo irradiación de luz visible se evaluó mediante el tratamiento de amoxicilina farmacéutica (AMX) en presencia y ausencia de oxidantes adicionales: peróxido de hidrógeno (H2O2) y sales de persulfato (PS). La influencia de la concentración de pH y PS en la tasa de conversión de AMX se estableció mediante planificación estadística y modelado de superficie de respuesta. Los resultados revelaron condiciones óptimas de [S2O82−] = 1,873 mM y pH = 4,808; estos también se utilizaron en presencia de H2O2 en lugar de PS en pruebas a largo plazo. La conversión AMX más rápida que poseía una constante de velocidad de orden cero de 1,51 × 10^-7 M·min^-1 se logró con el sistema de fotocatálisis + PS. Se estableció la ruta de conversión de AMX y se correlacionó la evolución/conversión de los intermedios formados con los cambios en la toxicidad hacia Vibrio fischeri. También se utilizó la eliminación de especies reactivas de oxígeno (ROS) para investigar el mecanismo de conversión de AMX, lo que reveló la principal contribución del h+ fotogenerado en todos los procesos.L'aigua neta accessible és una de les màximes prioritats per al creixement econòmic sostenible i el benestar social. L'aigua dóna suport a la vida i és un recurs crucial per a la humanitat; també és el nucli dels ecosistemes naturals i la regulació del clima. L'estrès hídric és principalment un problema de quantitat
Analysis of the corrosion mechanism in steel water pipelines with non-insulated inner wall
No full textOvaj diplomski rad istražuje kompleksnu tematiku korozije vodoopskrbnih sustava, ključnog dijela urbane infrastrukture zaduženog za osiguranje sigurne opskrbe pitkom vodom. Očuvanje strukturalnog integriteta vodovodnih cijevi, posebice onih s neizoliranim unutarnjim stijenkama, predstavlja ključnu brigu kako bi se održala pouzdana opskrba vodom i spriječili štetni učinci unutarnje korozije. Važno je naglasiti da svaki sustav opskrbe vodom predstavlja jedinstveno okružje koje oblikuje nijanse procesa korozije. U ovom slučaju, fokus je na čeličnoj cijevi za vodu iz priobalnog područja sjeverne Hrvatske. Izgled cijevi otkriva uočljive znakove propadanja, uključujući vidljive promjene u profilu debljine na određenim mjestima, promjene u boji i prisutnost različitih naslaga. Nadalje, uočava se i ljuštenje heterogenog sloja korozijskih produkata cijevi, pridodajući kompleksnosti proučavanog fenomena. Višeslojno istraživanje opaženog korozijskog fenomena uključilo je niz analitičkih tehnika,
od infracrvene spektroskopije s Fourierovom transformacijom (FTIR), digitalne mikroskopije, skenirajuće elektronske mikroskopije (SEM), do energijski disperzivne rendgenske spektroskopije (EDS). Dodatno, provedeno je i ispitivanje na prisutnost sulfida/karbonata s indikatorskom trakicom od olovnog acetatata i određivanje indeksa kvalitete vode te putem Langelierovog indeksa zasićenja (LSI). Istraživanje svojim rezultatima pridonosi razumijevanju specifičnosti korozijskih oštećenja u vodovodima i parametara okoliša u kojem ta oštećenja nastaju. Razumijevanje uzroka u mehanizama unutrašnje korozije od vitalnog je značaja za pravilno upravljanje vodovodnim sustavima i produženje vijeka trajanja cijevi.This graduate thesis investigates the complex topic of corrosion of water supply systems, which are a key part of urban infrastructure responsible for ensuring a safe supply of drinking water. Preserving the structural integrity of water pipes, especially those with uninsulated inner walls, is a key concern in order to maintain a reliable water supply and prevent the harmful effects of internal corrosion. It is important to emphasize that each water supply system represents a unique environment that shapes the nuances of the corrosion process. In this case, the focus is on a steel water pipe from the coastal area of northern Croatia. The appearance of the pipe reveals noticeable signs of deterioration, including visible changes in the thickness profile in certain places, changes in color and the presence of various deposits. Furthermore, the peeling of a heterogeneous layer of pipe corrosion products is observed, adding to the complexity of the studied phenomenon.
The multi-layered investigation of the observed corrosion damage included a number of analytical techniques, from Fourier-transform-infrared spectroscopy (FTIR), digital microscopy, and scanning electron microscopy (SEM), to energy-dispersive X-ray spectroscopy (EDS). In addition, a test for the presence of sulphides/carbonates was carried out with lead acetate indicator paper and the determination of the water quality index using the Langelier saturation index (LSI). With its results, the research contributes to the understanding of the specifics of corrosion damages in water pipes and the parameters of the environment in which these damages occur. Understanding the causes of internal corrosion mechanisms is vital to properly manage and extend the life of water-transporting pipeline systems
Application of electron microscopy in cosmetics
No full textU ovom završnom radu opisuje se osnovni princip rada elektronskog mikroskopa, razlike između skenirajućeg i transmisijskog elektronskog mikroskopa. Dan je pregled u koje svrhe se danas koriste elektronski mikroskopi, s naglaskom na upotrebu u pripremi i analizi kozmetičkih preparata. Primjena elektronske mikroskopije u kozmetici ima značajnu ulogu u razvoju, analizi i kontroli kvalitete kozmetičkih proizvoda. Elektronski mikroskopi, uključujući skenirajući elektronski mikroskop (SEM) i transmisijski elektronski mikroskop (TEM), omogućuju detaljno proučavanje mikrostrukture i površinskih karakteristika kozmetičkih preparata. SEM se koristi za analizu površinske topografije i sastava kozmetičkih uzoraka, omogućujući istraživačima da identificiraju i optimiziraju sastojke koji doprinose željenim svojstvima proizvoda, kao što su tekstura i izgled. TEM, s druge strane, omogućuje proučavanje unutarnje strukture kozmetičkih sastojaka na molekularnoj razini, što je ključno za razumijevanje kako različiti sastojci djeluju na kožu i kosu. Primjenom elektronske mikroskopije, znanstvenici mogu identificirati mikroskopske čestice i nečistoće, poboljšati formulacije, te osigurati konzistentnu kvalitetu i sigurnost kozmetičkih proizvoda. Ova tehnologija također pomaže u istraživanju novih sastojaka i njihovih učinaka, te doprinosi razvoju inovativnih kozmetičkih rješenja koja zadovoljavaju visoke standarde učinkovitosti i sigurnosti.In this thesis, the basic principles of electron microscopy, the differences between scanning electron microscopy (SEM) and transmission electron microscopy (TEM), are described. An overview of the current applications of electron microscopes is provided, with a focus on their use in the preparation and analysis of cosmetic products. The application of electron microscopy in cosmetics plays a significant role in the development, analysis, and quality control of cosmetic products. Electron microscopes, including SEM and TEM, enable detailed examination of the microstructure and surface characteristics of cosmetic preparations. SEM is used for analyzing the surface topography and composition of cosmetic samples, allowing researchers to identify and optimize ingredients that contribute to the desired properties of products, such as texture and appearance. TEM, on the other hand, enables the study of the internal structure of cosmetic ingredients at the molecular level, which is crucial for understanding how different ingredients interact with the skin and hair. Through the application of electron microscopy, scientists can identify microscopic particles and impurities, improve formulations, and ensure consistent quality and safety of cosmetic products. This technology also aids in the research of new ingredients and their effects, contributing to the development of innovative cosmetic solutions that meet high standards of effectiveness and safety
Photochemical synthesis and molecular modeling of new chlorine derivatives of naphthotriazole
No full textU svrhu proučavanja biološke aktivnosti, specifično inhibicije acetilkolinesteraze (AChE) i butirilkolinesteraze (BChE), sintetizirani su novi derivati naftotriazola 11-15. Sinteza se sastojala od tri koraka. Prvi korak je činila nukleofilna supstitucija, čime su nastali aldehidi 1-5. Nastali aldehidi su u drugom koraku podvrgnuti Wittigovoj reakciji, gdje su kao produkti nastali cis- i trans- izomeri heterostilbena 6-10. U posljednjem koraku, heterostilbeni su podvrgnuti fotokemijskoj ciklizaciji pri čemu su nastali naftotriazoli 11-15, koji literaturno nisu poznati. Naftotriazoli 11-14 uspješno su sintetizirani, dok se naftotriazol 15 pokazao zahtjevnijim za sintezu te nije pronađen uspjeh pri njegovoj sintezi. Novi sintetizirani i izolirani spojevi okarakterizirani su 1D NMR tehnikama. Biološka ispitivanja pokazala su kako naftotriazoli 11-13 posjeduju inhibicijski potencijal prema BChE, dok 12 jedini pokazuje isti i prema AChE te ujedno pokazuje najbolje rezultate pri inhibiciji oba enzima. Elektronska struktura i termodinamička stabilnost sintetiziranih naftotriazola istraživana je računalnim modeliranjem, a s obzirom na rezultate bioloških ispitivanja, naftotriazol 12 računalno je ispitan kao potencijalni inhibitor enzima AChE i BChE.In order to study the biological activity, specifically inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), new naphthotriazole derivatives 11-15 were synthesized. The synthesis consists of three steps. The first step was the nucleophilic substitution, resulting in aldehydes 1-5. The aldehydes were subjected to the Wittig reaction in the second step, where cis- and trans-isomers of heterostilbenes 6-10 were formed as products. In the last step, heterostilbenes were subjected to photochemical cyclization, whereby naphthotriazoles 11-15 were formed, which are not known in the literature. Naphtotriazoles 11-14 were successfully synthesized, while naphthotriazole 15 proved to be more demanding for synthesis and no success was found in its synthesis. New synthesized and isolated compounds were characterized by 1D NMR techniques. Biological tests showed that naphthotriazoles 11-13 possess inhibitory potential towards BChE, while 12 is the only one showing the same activity also towards AChE and at the same time showed the best results in inhibiting both enzymes. The electronic structure and thermodynamic stability of synthesized naphthotriazoles were investigated by computer modeling, and considering the results of biological tests, naphthotriazole 12 was computationally tested as a potential inhibitor of AChE and BChE enzymes
Characterisation and purification of crude glycerol after transesterification
No full textTransesterifikacija ili reakcija nastajanja biodizela je proces u kojem trigliceridi iz ulja ili masti reagiraju s metanolom ili etanolom uz dodatak katalizatora i tvore biodizel kao glavni produkt. Kao nusprodukt transesterifikacije dobiva se sirovi glicerol koji se sastoji od mnogih nečistoća te se tretira kao otpad. Iz navedenog razloga ekonomska konkurentnost biodizela, kao i glicerola opada. Kako bi biodizel dobio prednost nad tradicionalnim dizelom potrebno je povisiti globalnu vrijednost biodizela. Cilj ovog rada je ispitati može li se ekstrakcijom pomoću niskotemperaturnih eutektičkih otapala pročistiti glicerol na jednostavan i povoljan način. Pripremljeni su uzorci sirovog glicerola transesterifikacijom otpadnog ulja kave i suncokretovog ulja. Provedena je fizikalna karakterizacija te ispitivanje mješljivosti sirovog glicerola s različitim eutektičkim otapalima i pokazalo se kako su eutektička otapala neprikladna za proces ekstrakcije nečistoća iz sirovog glicerola jer dolazi do potpunog miješanja otapala i sirovog glicerola. Glicerol je u konačnici uspješno pročišćen komercijalnom metodom koja uključuje neutralizaciju, acidifikaciju, isparavanje, ekstrakciju te mikrofiltraciju.Transesterification or the biodiesel formation reaction is a process in which triglycerides form vegetable oils or fats react with methanol or ethanol in the presence of a catalyst, resulting in biodiesel as the main product. As a byproduct of transesterification, crude glycerol is obtained, which contains many impurities and is treated as waste. Due to these reasons, the economic competitiveness of biodiesel, as well as glycerol, decreases.To give biodiesel an advantage over traditional diesel, it is necessary to increase the global value of biodiesel. The aim of this study is to investigate whether extraction using deep eutectic solvents can purify glycerol in a simple and affordable way. Samples of crude glycerol were prepared by transesterification of waste coffee oil and sunflower oil. Physical characterization and miscibility testing of crude glycerol with different eutectic solvents was carried out and it was shown that eutectic solvents are unsuitable for the process of extraction of impurities from crude glycerol because a complete mixing of solvents and crude glycerol occurs. Glycerol was ultimately successfully purified by a commercial method that includes neutralization, acidification, evaporation, extraction and microfiltration
Design of a pressure swing adsorption process for CO2 capture
No full textU ovom radu provodi se istraživanje i simulacija procesa adsorpcije promjenom tlaka (eng. Pressure Swing Adsorption, PSA) za uklanjanje ugljikova (IV) oksida iz dimnih plinova energetskih postrojenja. PSA je separacijska tehnologija koja se temelji na različitim afinitetima pojedinih komponenata u plinskoj fazi prema čvrstom adsorbensu, uz korištenje cikličke promjene tlaka kako bi se omogućila regeneracija adsorbensa. Atraktivnost ove tehnologije nalazi se u njenom jednostavnom postavljanju i provedbi uz prihvatljivu energetsku učinkovitost te mogućnost selektivnog odvajanja CO2. U radu je provedena simulacija PSA procesa koristeći dvije kolone koje rade paralelno s vremenskom razlikom u koracima procesa kako bi se postigla kontinuiranost uklanjanja CO2. Cilj istraživanja bio je postizanje čistoće CO2 na izlazu procesa veće od 99,0 mol %, uz što veći iscrpak CO2 iz dimnih plinova koristeći NOTT-300 adsorbens. Rezultati simulacije pokazuju mogućnost optimizacije PSA procesa u smislu osiguranja čistoće i učinkovitosti uklanjanja CO2, što ovaj proces čini pogodnim za primjenu u industriji s ciljem smanjenja emisija stakleničkih plinova.This paper presents research and simulation of the Pressure Swing Adsorption (PSA) process for the removal of carbon dioxide (CO2) from the flue gases of energy generation plants. PSA is a separation technology based on the different affinities of individual components in the gas phase towards a solid adsorbent, utilizing cyclic pressure changes to enable the regeneration of the adsorbent. The attractiveness of this technology lies in its relatively simple setup and implementation, combined with acceptable energy efficiency and the ability to selectively separate CO2. In the study, a simulation of the PSA process was conducted using two columns operating in parallel with a time offset in process steps to achieve continuous CO2 removal. The goal of the research was to achieve a CO2 purity of over 99,0 mol % at the process outlet while maximizing the CO2 recovery from the flue gases. The simulation results demonstrate the potential for optimizing the PSA process in terms achieving the required purity and recovery of CO2 removal process, making it suitable for industrial applications aimed at reducing greenhouse gas emissions
The study of electrochemical reactions on the Ca/acetonitrile interface
No full textKalcijeve baterije se smatraju jednom od privlačnih zamjena za Li-ion baterije, zbog obilja kalcija u Zemljinoj kori i standarnog redukcijskog potencijala koji je usporediv s tim od litija. No, za realizaciju kalcijeve baterije koja u potpunosti radi potrebno je identificirati i razviti prikladne elektrode i elektrolit. Najveći izazov predstavlja uspostavljanje reverzibilne depozicije i otapanje metalne anode od kalcija. Dodatno, u velikom broju elektrolita dolazi do inhibicije kalcija zbog čega je od izrazito važno odabrati formulaciju elektrolita koja neće dovesti do inhibicije kalcija. U okviru ovog rada provedena su elektrokemijska ispitivanja kalcijeve elektrode u Ca(TFSI)2/ACN elektrolitu kako bi se istražio utjecaj Ca(TFSI)2/ACN elektrolita na elektrokemijsko ponašanje kalcijeve elektrode i na reverzibilnost reakcija otapanja i depozicije. Ispitivanje kalcijeve anode u Ca(TFSI)2/ACN elektrolitu provedeno je sljedećim tehnikama: naponom otvorenog kruga, cikličkom voltametrijom te elektrokemijskom impedancijskom spektroskopijom. Mjerenjem napona otvorenog kruga utvrđeno je da je kalcij u Ca(TFSI)2/ACN elektrolitu podložan koroziji pri čemu se elektroda prekriva inhibirajućim slojem. Inhibirajući sloj usporava katodnu depoziciju kalcija zbog male permeabilosti kalcijev iona kroz njega. Katodna depozicija kalcija je vidljiva na cikličkim voltamogramima u prvom ciklusu promjene potencijala, ali se kod sljedećih ciklusa elektroda potpuno inhibira. Anodno otapanje kalcija iz otopine Ca(TFSI)2/ACN ide neometano unatoč nastalom inhibirajućim sloj. Moguće je da otapanje kalcija razgrađuje nastali sloj i na taj način omogućuje daljnje otapanje.An attractive substitute for Li-ion batteries are calcium batteries due to the abundance of calcium in the Earth's crust and the standard reduction potential of calcium that is comparable to that of lithium. However, to fully realize a working secondary calcium battery, identification and development of suitable electrodes and electrolyte is needed. The biggest challenge is how to establish reversible plating and stripping of calcium at the metal-anodeinterface. Calcium inhibition occurs in a large number of electrolytes, therefore, it is extremely important to choose an electrolyte formulation that will not lead to calcium inhibition. Within this work, electrochemical tests of calcium electrode in Ca(TFSI)2/ACN electrolyte were carried out in order to investigate the influence of Ca(TFSI)2/ACN electrolyte on the electrochemical behavior of the calcium electrode and on the reversibility of plating and stripping reactions. Testing of the calcium anode in Ca(TFSI)2/ACN electrolyte was performed using the following techniques: open circuit voltage, cyclic voltammetry and electrochemical impedance spectroscopy. By measuring the open circuit voltage, it was determined that calcium in the Ca(TFSI)2/ACN electrolyte is subject to corrosion, where the electrode is covered with an inhibiting layer. The inhibiting layer slows down the cathodic deposition of calcium due to the low permeability of calcium ions through it. Cathodic deposition of calcium is visible on cyclic voltammograms in the first cycle of potential change, but the electrode is completely inhibited in subsequent cycles. The anodic dissolution of calcium from the Ca(TFSI)2/ACN solution proceeds unhindered despite the formation of an inhibiting layer. It is possible that the dissolution of calcium breaks down the resulting layer and thus enables further dissolution
The influence of titanium dioxide on the thermal, mechanical and barrier properties of poly(3- hydroxybutyrate-co-3-hydroxyvalerate)
No full textRastuća zabrinutost za očuvanje okoliša i smanjenje onečišćenja dovela je do sve većih izazova u razvoju i istraživanju prihvatljivih materijala. U ovom radu pripremljeni su nanokompoziti na bazi poli(3-hidroksibutirat-ko-3-hidroksivalerata) (PHBV) kao polimerne matrice i nanočestica titanova dioksida (TiO2) kao punila. PHBV je netoksičan polimer s visokim stupnjem kristalnosti, otporan je na ultraljubičasto zračenje, biokompatibilan je i biorazgradiv. S druge strane karakteriziraju ga slabija mehanička svojstva, izrazito je krut i krt. Iz tog razloga se PHBV-u dodaju nanočestice TiO2, koje doprinose poboljšanju mehaničkih svojstava, poput čvrstoće i elastičnosti te utječu na povećanje toplinske stabilnosti. Da bi se odredila svojstva nanokompozita kao potencijalnih materijala za industriju pakiranja hrane, provedena su ispitivanja na PHBV/TiO2 nanokompozitima s različitim udjelima TiO2 (1, 3, 5, 7 i 10 mas. %) te na čistoj PHBV matrici. Nanokompoziti su pripravljeni miješanjem u Brabender gnjetalici i prešanjem na hidrauličkoj preši. Toplinska svojstva ispitana su diferencijalnom pretražnom kalorimetrijom (DSC) i termogravimetrijskom analizom (TGA). Morfologija uzoraka određena je pretražnim elektronskim mikroskopom s disperzivnom rendgenskom spektroskopijom (SEM-EDX). Infracrvena spektroskopija s Fourierovim transformacijama i prigušenom totalnom refleksijom (FTIR-ATR) korištena je za određivanje vibracija funkcionalnih skupina. Mjerenjem kontaktnog kuta dobivene su informacije o slobodnoj površinskoj energiji, dok su mehanička svojstva ispitana mehaničkom kidalicom. Propusnost vodene pare određena je aparaturom po Herfeldu. Rezultati istraživanja su pokazali da TiO2 nanočestice utječu na fazne prijelaze PHBV matrice, smanjujući temperaturu taljenja i temperaturu kristalizacije, te povećavaju toplinsku stabilnost. Morfologija površina nanokompozita pokazuje ravnomjernu raspodjelu nanočestica. FTIR spektri pokazuju vibracije karakteristične za PHBV matricu i Ti-O-Ti veze. Izmjerene vrijednosti kontaktnih kutova pokazuju povećanje hidrofilnosti nanokompozita pri udjelu TiO2 većim od 5 mas. %. Povećanjem udjela TiO2 smanjuje se propusnost vodene pare te prekidna čvrstoća, prekidno istezanje i Youngov modul, ukazujući na lošija mehanička svojstva nanokompozita u odnosu na čistu PHBV matricu.The increasing concern for environmental preservation and pollution reduction has led togrowing challenges in the development and research of sustainable materials. In this study, nanocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as the polymer matrix and titanium dioxide (TiO2) nanoparticles as the filler were prepared. PHBV is a non-toxic polymer with a high degree of crystallinity, resistant to ultraviolet radiation, and is both biocompatible and biodegradable. However, it is characterized by weaker mechanical properties and is extremely rigid and brittle. Therefore, TiO2 nanoparticles are added to PHBV to improve its mechanical properties, such as strength and elasticity, and to enhance its thermal stability. To determine the properties of nanocomposites as potential materials for the food packaging industry, tests were conducted on PHBV/TiO2 nanocomposites with different TiO2 contents (1, 3, 5, 7, and 10 wt. %) as well as on pure PHBV matrix.
The nanocomposites were prepared by mixing in a Brabender kneader and pressing on a hydraulic press. Thermal properties were examined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The morphology of the samples was determined using a scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX). Fourier transform infrared spectroscopy with attenuated total reflectance
(FTIR-ATR) analyzed the vibrations of functional groups. Contact angle measurements provided information about the free surface energy, while mechanical properties were tested using a mechanical tester. Water vapor permeability was determined using Herfeld equipment. The results showed that TiO2 nanoparticles influence the phase transitions of the PHBV matrix, reducing the melting temperature and the crystallization temperature, as well as enhancing thermal stability. The morphology of the nanocomposite surfaces shows a uniform distribution of nanoparticles. FTIR spectra reveal vibrations characteristic of the PHBV matrix and Ti-O-Ti bonds. The measured contact angle values indicate an increase in nanocomposite hydrophilicity with TiO2 content greater than 5 wt. %. Increasing TiO2 content decreases water vapor permeability, tensile strenght, elongation at break and Young's modulus, indicating poorer mechanical properties of the nanocomposites compared to the pure PHBV matrix
Drug incorporation into polymeric microparticles
No full textKitozan je jedini prirodni polimer polikationske prirode kojeg svojstva poput biokompatibilnosti, biorazgradljivosti i netoksičnosti čine idealnim za upotrebu u poljoprivredi, prehrambenoj i kozmetičkoj industriji, pročišćavanju otpadnih voda, tkivnom inženjerstvu te kao sustav za dostavu lijekova. Ovisno o primjeni, moguće je pripremiti materijale na temelju kitozana u obliku emulzija, filmova te mikro- i nano-čestica koje su se pokazale kao idealni dostavljači lijekova. Kako bi se postigla željena kinetika otpuštanja lijeka, a time i uspješno liječenje, potrebno je pripremiti mikro- i nanočestice kontrolirane raspodjele veličina, morfologije i strukture. Neke od metoda koje se koriste za pripremu kitozanskih mikročestica su elektroštrcanje, sušenje raspršivanjem, dobivanje iz emulzije i precipitacija. U ovom radu, proces elektroštrcanja je odabran za pripravu mikročestica. Pripremljene su kompozitne mikročestice na temelju kompleksa kitozana i bakrovih(II) iona koje kao punilo sadrže hidroksiapatit (CHT-Cu/HAp), te je istražen utjecaj dodatka hidroksiapatita na svojstva mikročestica i efikasnost ugradnje antitumorskog lijeka (doksorubicin, DOX). Suhe mikročestice analizirane su primjenom infracrvene spektroskopije s Fourierovom transformacijom prigušene totalne refleksije (ATR-FTIR) i rendgenskom difrakcijskom analizom (XRD) te rezultati ukazuju na prisutnost interakcija između polimerne matrice i punila. Veličina i oblik mikrosfera istraženi su invertnim svjetlosnim mikroskopom. Uočena je sferičnost pripremljenih mikročestica, dok su najmanje mikročestice s najužom raspodjelom dobivene za sustav s 5 mas.% HAp-a (CHT-Cu/HAp5). Dodatakom većeg udjela hidroksiapatita (10 mas.%) dobivene su veće mikročestice s širom raspodjelom veličina zbog nestabilnsti procesa elektroštrcanja. Stupanj bubrenja CHT-Cu/HAp mikročestica raste smanjenjem pH vrijednosti inkubacijskog medija i povećanjem udjela hidroksiapatita. Fluorescentna spektrometrija i gravimetrijska metoda korištene pri određivanju ugradnje DOX-a u pripremljene CHT-Cu/HAp mikročestice dale su neočekivane rezultate te su potrebna daljnja istraživanja kako bi se procjenila efikasnost ugradnje lijeka.Chitosan is the only natural polycationic polymer whose properties such as biocompatibility, biodegradability and non-toxicity make it ideal for use in agriculture, food and cosmetics industry, wastewater treatment, tissue and bone engineering and as a drug delivery system. Depending on the application, it is possible to prepare chitosan-based materials in the form of emulsions, films, and micro- and nanoparticles, which have proven to be ideal drug carriers. In order to achieve the desired drug release kinetics, and thus successful tumor treatment, it is necessary to prepare micro- and nanoparticles with a controlled size distribution, morphology and structure. Some of the methods used to prepare chitosan microparticles are electrospraying, spray drying, emulsion and precipitation methods. In this work, the electrospraying process was used for the preparation of microparticles. Composite microparticles based on chitosan‒copper(II) ions complex and hydroxyapatite (CHT-Cu/HAp) were prepared, while the influence of the addition of hydroxyapatite on the properties and drug loading efficiency of the antitumor drug (doxorubicin, DOX) was investigated. Dry microspheres were analyzed using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction analysis (XRD), and the results indicated the presence of interactions between the polymer matrix and the filler. The size and shape of the microspheres were determined using an inverted light microscope. The sphericity of the prepared microparticles was observed, while the smallest microparticles with the narrowest size distribution were obtained for the system with 5 wt.% HAp (CHT-Cu/HAp5). At a higher content of hydroxyapatite (10 wt.%), larger microparticles with a wider size distribution were obtained due to the instability of the electrospraying process. The swelling degree of CHT-Cu/HAp microparticles increased at lower pH value of the incubation medium and at higher content of hydroxyapatite. Fluorescence spectrometry and the gravimetric method used to analyze the drug loading into the prepared CHT-Cu/HAp microparticles indicated unexpected results; therefore, further investigation is needed to assess the effectiveness of DOX