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Composite photocatalysts for photoreduction of CO2 to useful products
No full textEmisija CO₂ u atmosferu danas je svjetski problem jer je CO₂ jedan od plinova koji pridonose globalnom zatopljenju. Kao rješenje navedenog problema nudi se fotokatalitička redukcija CO₂ do korisnih produkata kao što su metan i metanol, a dan je niz primjera istraživanja različitih fotokatalizatora i metoda u svrhu jednog cilja- dobivanje alternativnog goriva koji će pridonjeti smanjenju količine CO₂. Iako je fotokatalitička redukcija CO₂ obećavajuća tehnika za redukciju do nefosilnih goriva i ostalih vrijednih spojeva, proces je termodinamički nepovoljan i nema tendenciju odvijati se spontano jer je ΔG>0 , a uz to i složenost samog reakcijskog mehanizma pridonosi nemogućnosti primjene ove metode za komercijalne svrhe. Kao najbolji način za redukciju CO₂ nudi se korištenje sunčeve energije jer pruža učinkovit način pohranjivanja energije. U ovome radu opisan je razvoj solarnih fotoreaktora za povećanje prinosa pri proizvodnji goriva. Posebna pozornost dana je općim metodama fotokatalitičke pretvorbe CO₂ koje pokreće sunčeva energija kako bi se onda odabrala prikladna metodologija solarne fotoredukcije CO₂ u metanol.Emission of CO₂ into the atmosphere is a worldwide problem today because CO₂ is one of the gases that contribute to global warming. Photocatalytic reduction of CO₂ to useful products such as methane and methanol is offered as a solution to the mentioned problem, and a series of research examples of different photocatalysts and methods are given for the purpose of one goal - obtaining an alternative fuel that will contribute to the reduction of the amount of CO₂. Although the photocatalytic reduction of CO₂ is a promising technique for reduction to non-fossil fuels and other valuable compounds, it is a process with unfavorable thermodynamics and does not tend to take place spontaneously because ΔG>0 and the complexity of the reaction mechanism itself contributes to the impossibility of applying this method for commercial purposes. The best way to reduce CO₂ is to use solar energy because it provides an efficient mode for storing energy. This paper describes the development of solar photoreactors for increasing the yield of fuel production. Special attention is given to the general methods of photocatalytic conversion of CO₂ driven by solar energy in order to determine the suitable methodology for solar photoreduction of CO₂ to methanol
Nanofluids based on graphene and plant based esters
No full textCilj ovog rada je priprema nanofluida na osnovi repičinog ulja (RU) i metilnog estera masnih kiselina (Fatty acid methyl esters – FAME) in situ polimerizacijom monomera
metil-metakrilata, lauril-metakrilata i stearil-metakrilata uz dodatak nanočestica grafena pri izotermnim uvjetima od 95±1 °C u šaržnom kotlastom reaktoru tijekom 240 minuta. Polimerizacija je provedena uz dodatak peroksidnog inicijatora
tert-butil-peroksi-2-etilheksanoat. Nanofluidi su pripremljeni metodom u dva stupnja disperzijom čestica grafena u baznim uljima FAME i repičinom ulju ultrazvučnom homogenizacijom. Ukupno je pripremljeno 16 nanofluida raznih udjela grafena i polimera. Rezultati iz kojih se zaključuje kako dodatkom grafena nastaje polimer veće molekulske mase dobiveni su GPC analizom te određivanjem krivulja raspodjele molekulskih masa polimera bez dodatka i s dodatkom grafena. Iz 1H NMR spektara dobiveni su rezultati utjecaja grafena na povećanje konverzije polimerizacije. Ispitivanjem toplinske vodljivosti i električne otpornosti dobiveni su rezultati koji navode na povećanje toplinske vodljivosti i smanjenje volumne otpornosti nanofluida dodatkom grafena u odnosu na bazna ulja bez grafena. Nadalje, ispitivanjem reoloških svojstava pokazalo je utjecaj grafena i polimera na povećanje viskoznosti nanofluida i rezultate utjecaja grafena i polimera na koeficijente trenja i otpor maziva trošenju koji ne pokazuju trend rasta odnosno smanjenja. Stabilnost pripremljenih nanofluida ispitivana je vizualnim testom tijekom 42 dana kojim je utvrđena najveća stabilnost kod uzoraka s 10 mas. % udjelom polimera i dodanim česticama grafena. Analiza toplinskih tokova i faznih prijelaza razlikovnom pretražnom kalorimetrijom (DSC) utvrdila je smanjenje kristalizacije i snižavanje temperature početka kristalizacije kod svih uzoraka dodatkom grafena i polimera, a najveća razlika primijećena je kod nanofluida na osnovi FAME-a.The goal of this work is the preparation of nanofluids based on rapeseed oil (RU) and fatty acid methyl esters (FAME) by in situ polymerization of methyl-methacrylate,
lauryl-methacrylate, and stearyl-methacrylate monomers with the addition of graphene nanoparticles under isothermal conditions of 95 ±1 °C in a batch boiler reactor for
240 minutes. The polymerization was carried out with the addition of the peroxide initiator, tert-butyl-peroxy-2-ethylhexanoate. Nanofluids were prepared by a two-step method by dispersion of graphene particles in FAME and rapeseed oil base oils by ultrasonic homogenization. A total of 16 nanofluids with various concentrations of graphene and polymers were prepared. The results from which it can be concluded that the addition of graphene creates a polymer with a higher molecular weight were obtained by GPC analysis and by determining the distribution curves of the polymer molecular masses without and with the addition of graphene. From the 1H NMR spectra, the results of the influence of graphene on the increase in polymerization conversion were obtained. By testing thermal conductivity and electrical resistance, results were obtained that indicate an increase in thermal conductivity and a decrease in volume resistance of nanofluids with the addition of graphene compared to base oils without graphene. Furthermore, the examination of rheological properties showed the influence of graphene and polymer on increasing the viscosity of nanofluids and the results of the influence of graphene and polymer on friction coefficients and wear resistance of lubricants, which do not show an increasing or decreasing trend. The stability of the prepared nanofluids was examined by a visual test for 42 days, which determined the highest stability in samples with 10 wt. % by polymer content and added graphene particles. The analysis of heat flows and phase transitions by differential scanning calorimetry (DSC) determined a reduction in the extent of crystallization and a lowering of the temperature of the beginning of crystallization in all samples with the addition of graphene and polymer, and the biggest difference was observed in nanofluids based on FAME
Viscosimetric properties of polymeric additives of vegetable lubricant oils
No full textSuvremeni izazovi vezani uz fosilna goriva i sirovine naglašavaju potrebu za prijelazom prema održivim alternativama, a upravo jedno od ključnih inovativnih rješenja leži u obnovljivim izvorima poput estera masnih kiselina (FAE). Maziva proizvedena iz FAE, uključujući metilne (FAME) i butilne (FABE) estere masnih kiselina, otvaraju vrata za perspektivnu proizvodnju visokoučinkovitih maziva. Navedeni esteri su dobiveni iz prirodnih resursa poput biljnih ulja te pokazuju manji ugljični otisak i štetni utjecaj na okoliš u usporedbi s konvencionalnim mazivima na bazi fosilnih sirovina, a u ovome radu sintetizirani su transesterifikacijom repičinog ulja. Maziva igraju ključnu ulogu u održavanju učinkovitosti strojeva, na način da smanjuju trenje i trošenje i time produžuju njihov vijek trajanja. Međutim, tradicionalna maziva proizvedena iz fosilnih sirovina često su povezana s negativnim utjecajem na okoliš i klimatskim promjenama. Stoga su istraživanja usmjerena na razvoj održivijih alternativa, a biljna maziva ulja iz estera masnih kiselina postaju obećavajuća opcija. Osim zadovoljavajuće mazivosti, prednosti ovih maziva ogledaju se u njihovoj ekološkoj prihvatljivosti, biorazgradivosti i manjoj toksičnosti. FAE se proizvode iz obnovljivih resursa, čime se smanjuje ovisnost o ograničenim zalihama fosilnih sirovina. Dodavanjem polimernih aditiva mazivim uljima možemo postići niz poboljšanja njihovih svojstava kao što su viskoznost, mazivost i niskotemperaturna svojstva. Upravo zbog te činjenice ovaj rad je usmjeren prema ispitivanju potencijalnih poboljšanja svojstava biljnih maziva, sintezom različitih polimernih aditiva u metilnom (FAME) i butilnom (FABE) esteru masnih kiselina. U tu svrhu su korišteni metakrilatni monomeri dodecil-metakrilat (DDMA), oktadecil-metakrilat (ODMA) te metil-metakrilat (MMA) u različitim ukupnim koncentracijama u biljnom esteru uz dodatak peroksidnog inicijatora. Radi ispitivanja primjenskih svojstava i karakterizacije sintetiziranih uzoraka te otkrića mogućih poboljšanja, primijenjen je niz analitičkih metoda. Ove metode uključuju nuklearnu magnetsku rezonancu, diferencijalnu pretražnu kalorimetriju, reološka ispitivanja i kromatografiju na propusnom gelu, čiji su rezultati i usporedbe prikazani u radu.Contemporary challenges related to fossil fuels underscore the need for a transition towards sustainable alternatives, and one of the key innovative solutions lies in renewable energy sources such as fatty acid esters (FAE). Lubricants produced from FAE, including methyl (FAME) and butyl (FABE) fatty acid esters, open the door to prospective high-performance lubricant production. These esters are derived from natural resources such as vegetable oils and exhibit a smaller carbon footprint and less harmful environmental impact compared to conventional lubricants based on fossil resources. In this study, they were synthesized through the transesterification of rapeseed oil. Lubricants play a crucial role in maintaining the efficiency of machinery by reducing friction and wear, thereby extending their lifespan. However, traditional lubricants derived from fossil fuels are often associated with negative environmental impacts and climate change. Hence, research is directed towards developing more sustainable alternatives, and plant-based lubricating oils from fatty acid esters are becoming a promising option. In addition to satisfactory lubricity, the advantages of these lubricants include their environmental friendliness, biodegradability, and lower toxicity. FAEs are produced from renewable resources, reducing dependence on finite fossil fuel reserves and emissions of harmful gases, thus promoting energy sustainability and supporting the global transition to cleaner energy sources. The addition of polymeric additives to lubricating oils can yield a range of improvements in their properties. Among other things, these additives can enhance lubricity, low-temperature properties, and further extend the equipment's lifespan. This study is focused on investigating potential property enhancements of plant-based lubricants through the synthesis of various polymeric additives obtained via radical polymerization within fatty acid esters. For this purpose, methacrylic monomers DDMA (dodecyl methacrylate), ODMA (octadecyl methacrylate), and MMA (methyl methacrylate) were used in different ratios with the addition of a peroxide initiator. To assess the performance properties of the synthesized samples, such as viscosity, friction coefficient, pour point, lubricity, and other characteristics, a series of analytical methods were employed. These methods include nuclear magnetic resonance, differential scanning calorimetry, rheological testing, and gel permeation chromatography, the results and comparisons of which will be presented in the following sections of the paper
Ekotoksičnost mikroplastike i prioritetnih onečišćivala u vodi
No full textPlastics is an inevitable part of our daily life, hence its usage will continue to grow. Multiple and prolonged use and abrasion of the plastic surface might result in partial deterioration of plastic to micro-sized particles – microplastic (MP). Recently, it has been observed that MP’s multi-faceted structural and surface properties makes it an adsorbent for numerous aquatic pollutants such as pharmaceuticals and pesticides, defined under the EU water protection legislation as contaminants of emerging concern (CECs). Their hydrophobicity, polarity and low-biodegradability makes them readily adsorbable at polar, hydrophobic, aged and degraded specific surfaces of MP, contributing to the overall toxicity of such binary systems. Besides, in environmental conditions MP might leach additives and constituents that are often found toxic and hazard. The aim of this dissertation was to investigate the influence of thermal- and photo-aging of polyethylene terephthalate (PET) and polypropylene (PP) on the changes in morphology and structure of polymer materials and the overall ecotoxicity of PET and PP MPs in water. The characterization of pristine and aged MPs was performed by Fourier-transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), as well as Water Contact Angle (goniometer) and the Branuer Emmett Teller (BET) specific surface area measurements. In order to investigate the fragmentation of plastic materials into MPs, grinding was performed in a single-drum cryogenic mill, while size distribution of obtained MPs particles was determined by the sieve shaker with five sieves of different mesh sizes to separate the particles according to their size. Adsorption of selected CECs, pharmaceutical diclofenac (DCF) and pesticide atrazine (ATZ), was investigated on both pristine and aged MPs according to the computational/empirical approach employing Full Factorial Design (FFD) as the experimental plan in the combination with Response Surface Modelling (RSM). Furthermore, pristine and aged MPs along with PP waste packaging films, were submitted to leaching tests in order to study possible migration of consituents. The main focus of this dissertation was the evaluation of the aquatic ecotoxicity of the samples after the adsorption and leaching tests and it was tested on the marine bacteria Vibrio fischeri (VF), freshwater crustacean Daphnia magna (DM) and green microalgae Raphidocelis subcapitata (RS), following the procedures disclosed in ISO 11348-3:2007, ISO 6341:2012 and ISO 8692:2012 standards, respectively. Finally, the leachates were tested for their biodegradability, along with glucose as readiliy biodegradable substrate. Based on the obtained results, it is possible to establish a direct relationship between the aging of MP and the increase in its toxicity. Characterization revealed severe degradation of material; thermal-aging affected the structure, while photo-aging caused the surface alterations of PET and PP. Hence, changes in surface morphology such as cracks, fractures, notches and bumps were observed.
The increase in crystallinity of PET and PP resulted in changes of brittleness and accelerated fragmentation to smaller MP’s particles. It was found that hydrophobicity increased, while specific surface decreased; the exception was photo-aged PP. Adsorption of CECs onto MPs is correlated with the changes in the surface morphology enhanced with the photo-aging. Adsorption of CECs was driven by hydrophobicity and specific surface, as well as smaller MP particle sizes as a result of accelerated and prolonged aging period.
RSM approach revealed that temperature is a more significant parameter than MP dosage for CECs adsorption. It can be concluded that aquatic ecotoxicity generally increases with the prolonged exposure to aging, especially valid for the photo-aged MPs. However, some exceptions were observed depending on the type of MPs, CECs and targeted toxicity test organism. Individual CECs showed high ecotoxicity effects toward DM, while slightly lower effects were recorded toward RS. It was also found that DM was the most sensitive organism to the exposure to MPs, with and without CECs. The aging of MPs resulted with the accelerated leaching of constituents for both PET and PP, resulting with ecotoxic responses in cases of all three tested organisms. However, DM was shown to be the most sensitive to leachates originated from PP-MP, while in the case of PET leachates other two test organisms (VF and RS) were more sensitive in ecotoxicity response than DM.
The biodegradability of glucose was inhibited by the presence of (heavy) metals in leachates originated from both thermal- and photo-aged PET and PP MPs.Plastika je neizbježan dio svakodnevnog života i smatra se kako će njezina uporaba nastaviti rasti. Višestruka i dugotrajna uporaba te abrazija površine plastike može rezultirati djelomičnom fragmentacijom na čestice mikro veličine – mikroplastiku (MP). Nedavno je uočeno kako mikroplastika ima brojna strukturna i površinska svojstva koja je čine adsorbentom za brojna onečišćivala pristutna u vodi kao što su farmaceutici i pesticidi, koji su prema vodnom zakonodavstvu EU-a definirani kao onečišćivala koja izazivaju zabrinutost (eng. Contaminants of Emerging Concern, CEC). Njihova hidrofobnost, polarnost i slaba biorazgradivost čine ih toksičnima, a lako se apsorbiraju na polarnu, hidrofobnu, ostarenu i degradiranu specifičnu površinu MP. U okolišnim uvjetima može doći i do izluživanja (eng. leaching) aditiva te konstituenata koji mogu biti ekotoksični i opasni za organizme.
Cilj ove disertacije bio je istražiti utjecaj termo- i foto- starenja poli(etilen- tereftalata) (PET) i polipropilena (PP) na promjenu morfologije i strukture materijala te ekotoksičnost mikroplastike u vodi. Karakterizacija nestarene i starene MP provedena je pomoću infracrvene spektroskopije s Fourierovom transformacijom (FTIR), diferencijalne pretražne kalorimetrije (DSC), termogravimetrijske analize (TGA), skenirajuće elektronske mikroskopije (SEM), kao i goniometra za određivanje kontaktnog kuta vode te mjerenjem specifične površine na temelju Branuer Emmett Teller (BET) modela. Kako bi se istražila fragmentacija plastike u MP, usitnjavanje je provedeno u kugličnom kriogenom mlinu, dok je raspodjela veličine dobivenih MP čestica određena pomoću vibracijske tresilice s pet sita različitih veličina otvora za izdvajanje čestica prema njihovoj veličini. Adsorpcija CEC-a, farmaceutika diklofenaka (DCF) i pesticida atrazina (ATZ) ispitana je i na nestarenoj i starenoj MP u skladu s računalnim/empirijskim pristupom na temelju punog faktorskog dizajna (eng. Full Factorial Design, FFD) u kombinaciji s metodologijom odzivne površine (eng. Response Surface Methdology, RSM). Nadalje, nestarena i starena MP zajedno s otpadnim ambalažnim PP filmovima, podvrgnuti su testovima izluživanja kako bi se ispitala moguća migracija konstituenata. Glavni fokus ove disertacije bila je procjena ekotoksičnosti uzoraka u vodi nakon provedenog procesa adsorpcije i izluživanja i to na morskim bakterijama Vibrio fischeri (VF), slatkovodnim račićima Daphnia magna (DM) i zelenim mikroalgama Raphidocelis subcapitata (RS), prema standardima ISO 11348-3: 2007, norme ISO 6341:2012 i ISO 8692:2012. Na kraju, ispitana je i biorazgradivost uzoraka nakon testa izluživanja, zajedno s glukozom kao lako biorazgradivim supstratom. Na temelju dobivenih rezultata, moguće je utvrditi izravnu vezu između starenja MP- i povećanja njezine toksičnosti. Karakterizacija je pokazala da su procesi termooksidacije i fotooksidacije uzrokovali degradaciju materijala, gdje je termooksidacija utjecala na strukturu, dok je fotooksidacija uglavnom utjecala na površinske promjene PET- i PP-. Stoga su uočene promjene u morfologiji površine kao što su pukotine, lomovi, zarezi i neravnine. Povećanje kristalnosti PET-a i PP-a rezultiralo je promjenom lomljivosti i ubrzanom fragmentacijom na manje čestice MP-a. Uočeno je je povećanje hidrofobnosti i smanjenje specifične površine, osim u slučaju starenog PP-a. Adsorpcija CEC-ova na površinu MP-a u korelaciji je s promjenama morfologije površine nastalim fotooksidativnim starenjem. Hidrofobnost i specifična površina, zajedno s manjim veličinama čestica starenog MP-a, potaknuli su adsorpciju hidrofobnih CEC-ova. RSM ukazuje na to kako je temperatura značajniji parametar od udjela MP za adsorpciju CEC-ova. Može se zaključiti da vodena ekotoksičnost općenito raste s produljenom izloženošću starenju, posebno za foto-stareni MP. Međutim, primijećene su neke iznimke ovisno o vrsti MP-a, CEC-a i ciljanog organizma za ispitivanje ekotoksičnosti. Pojedinačni CEC-ovi pokazali su visoke ekotoksične učinke prema DM, dok su nešto niži učinci zabilježeni prema RS. Također je utvrđeno da je DM najosjetljiviji organizam na izloženost MP, sa i bez CEC-ova. Posebno je DM pokazala visoku osjetljivost na MP, sa i bez adsorbiranih CEC-ova.
Starenje MP rezultiralo je pojačanim izluživanjem konstituenata iz PET-a i PP-a, što je rezultiralo ekotoksičnim odgovorima u slučajevima sva tri testirana organizma. Međutim, pokazalo se kako je DM najosjetljiviji na izluživanje PP-MP, dok su u slučaju izluživanja
PET-MP osjetljivija druga dva testna organizma (VF i RS). Biorazgradivost glukoze bila je inhibirana prisutnošću (teških) metala u uzorcima nakon izluživanja koje potječu iz termo- i foto-starenih PET-MP i PP-MP
Composite microparticles as drug delivery systems
No full textCilj ovoga rada bila je priprema kompozitnih kitozan-bakar(II)/hidroksiapatit mikročestica te ispitivanje mogućnosti inkapsulacije antitumorskog lijeka u pripremljene materijale u svrhu priprave sustava za ciljanu dostavu lijekova. Kitozan (CHT), kao jedan od najvažnijih poliaminosaharida, izazvao je veliki interes zbog svojih poželjnih svojstava i široke primjene. Kitozan ima sposobnost stvaranja stabilnih kelata s bioaktivnim metalnim ionima, te je u ovom radu pripremljena polimerna matrica na temelju kitozan-Cu2+ kompleksa. S ciljem povećanja efikasnosti ugradnje antitumorskoga lijeka u matricu, pripravljene su kompozitne mikročestice dodatkom anorganskog punila (hidroksiapatit, HAp). Metoda elektroštrcanja je korištena za proizvodnju visoko sferičnih mikronosača na temelju kompozita CHT-Cu/HAp zbog svoje jednostavnosti i visoke efikasnosti. Za identifikaciju dobivenih mikročestica korištene su infracrvena spektroskopija s Fourierovom transformacijom prigušene totalne refleksije
(ATR-FTIR) i rendgenska difrakcijska analiza (XRD). Oblik, veličina i raspodjela veličina mikročestica određeni su pomoću pretražnog fluorescentnog mikroskopa. Stupanj bubrenja mikročestica određen je u otopinama fosfatnog pufera pH vrijednosti 6 (PB-6) i 7,4 (PB-7,4) te u demineraliziranoj vodi (H2O, pH 6,5). Ugradnja antitumorskoga lijeka (doksorubicin, DOX) provedena je u blago kiselom mediju tijekom jednog, odnosno tri sata, pri 37 °C te su svojstva mikročestica s ugrađenim lijekom ispitana primjenom pretražnog fluorescentnog mikroskopa, fluorescentne spektrometrije i gravimetrijske metode. XRD i FTIR analize pokazale su prisutnost hidroksiapatita u pripravljenom CHT-Cu/HAp kompozitu, te su mikročestice dobivene procesom elektroštrcanja bile sferičnoga oblika uz prosječnu veličinu čestica 56,1 ± 5,1 μm za CHT-Cu sustav, odnosno 72,1 ± 17,6 μm za CHT-Cu/HAp sustav. Ispitivanje stupanja bubrenja pokazalo je da mikročestice najviše bubre u kiselom mediju te da se s dodatkom hidroksiapatita povećava stupanj bubrenja. Primjenom fluorescentne mikroskopije utvrđena je uspješna ugradnja doksorubicina u CHT-Cu i CHT-Cu/HAp mikročestice. Rezultati fluorescentne spektrometrije i gravimetrijske metode ukazali su na prisutnosti soli fosfata u mikročesticama. Dobiveni rezultati pokazali su da pripravljene kompozitne mikročestice mogu poslužiti kao potencijalni sustavi za dostavu lijeka.This work aimed to prepare composite chitosan-copper/hydroxyapatite microparticles and investigate the possibility of loading an antitumor drug, forming a targeted drug delivery system. Chitosan (CHT), one of the most important polyaminosaccharides, has drawn attention due to its desirable properties and wide applications. Chitosan can form stable chelates with bioactive metal ions, and in this work, a polymer matrix based on the CHT-Cu2+ complex was prepared. To increase the efficiency of incorporating the antitumor drug into the matrix, composite microparticles were prepared with the addition of an inorganic filler (hydroxyapatite, HAp). The electrospraying method was used to produce highly spherical microcarriers based on CHT-Cu/HAp composite due to its simplicity and high efficiency. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction analysis (XRD) were used to investigate the structure and composition of the obtained microspheres. The shape, size and size distribution of microparticles were determined using a scanning fluorescence microscope. The swelling degree of the microparticles was determined in phosphate buffer solution with pH values of 6 (PB-6) and 7.4 (PB-7.4) and demineralized water (H2O, pH 6.5). Incorporation of the antitumor drug (doxorubicin, DOX) was carried out in a slightly acidic medium for one or three hours at
37 °C, and the properties of the drug loaded-microparticles were examined using a fluorescence microscope, fluorescence spectrometry and gravimetric method. XRD and FTIR analyses showed the presence of hydroxyapatite in the prepared CHT-Cu/HAp composite and the microparticles obtained by the electrospraying process were spherical with an average particle size of 67.5 ± 25.6 μm for the CHT-Cu system and 72.1 ± 17.6 μm for the CHT-Cu/HAp system. The swelling study showed that the microparticles swell the most in an acidic medium, while the swelling degree increases with the addition of hydroxyapatite.
Using fluorescence microscopy, successful incorporation of doxorubicin into CHT-Cu and
CHT-Cu/HAp microparticles was observed. The results of fluorescence spectrometry and gravimetric method indicated the presence of phosphate salts in the microparticles.
The obtained results showed that the prepared composite microparticles can serve as potential drug delivery systems
Application of magnetochemistry in polymerization
No full textU završnom radu razmatra se primjena magnetokemije u procesu polimerizacije, utjecaj magnetnog polja na polimerni proces i magnetske polimerne nanomaterijale. Opisane su osnove magnetizma, objašnjeni osnovni pojmovi poput magnetizacije, magnetske susceptibilnosti i različite vrste magnetizma (feromagnetizam, paramagnetizam, dijamagnetizam). Osvrnuta je pažnja na različite vrste procesa polimerizacije, kao što su adicijska i kondenzacijska polimerizacija, te dvije vrste adicijske polimerizacije – radikalna i ionska polimerizacija. Određena pažnja posvećena je magnetnim polimernim kompozitima, koji mogu poboljšati kontrolu nad polimerima i polimernim procesima i imaju široku primjenu u industrijama biomedicine, elektronike, zaštite okoliša i mnogim drugima. Primjena magnetokemije u polimerizaciji je sve više istraživana zbog svojih prednosti u poboljšanju svojstava krajnjih proizvoda procesa polimerizacije, optimizaciji reakcijskih uvjeta i smanjenju vremena reakcije.This paper discusses the application of magnetochemistry in the polymerization process, influence of magnetic fields on the polymer process and magnetic polymer nanomaterials. The basics of magnetism are described, basic concepts such as magnetization, magnetic susceptibility and different types of magnetism (ferromagnetism, paramagnetism, diamagnetism) are explained. Attention is paid to different types of polymerization processes, such as addition and condensation polymerization, and two types of addition polymerization – radical and ionic polymerization. Some attention is paid to magnetic polymer composites, which can improve control over polymers and polymer processes and have wide applications in the biomedical, electronic, environmental protection and many other industries. The application of magnetochemistry in polymerization has been increasingly investigated due to its advantages in improving the properties of the end products of the polymerization process, optimizing reaction conditions and reducing reaction time
Effect of temperature on surface and interfacial tension
No full textPovršinska napetost je fenomen uzrokovan kohezivnim silama na granici između kapljevite i plinovite faze. Zbog razlike u međumolekularnim silama između površine i unutrašnjosti, kapljice nastoje smanjiti svoju površinu zauzimajući idealan sferični oblik. (1) Međupovršinska napetost je sličan fenomen koji se javlja na granici dviju nemiješljivih kapljevitih faza, gdje prevladavaju adhezijske sile koje doprinose njihovom razdvajanju, a od posebnog je značaja u procesima ekstrakcije. (2) U ovom radu, istražen je utjecaj temperature na površinsku napetost odabranih otapala: vode, suncokretovog ulja, hidrofobnog i hidrofilnog DES-a. Dodatno, proučavan je utjecaj temperature na međupovršinsku napetost tri dvofazna sustava: voda-suncokretovo ulje, voda-hidrofobni DES i suncokretovo ulje-hidrofilni DES. Mjerenja površinske i međupovršinske napetosti provedena su tenziometrom, koristeći metodu Wilhelmove pločice i Du Noüyevog prstena, pri definiranim temperaturama. Eksperimentalni pristup temelji se na principu da promjena temperature izravno utječe na kinetičku energiju molekula i čvrstoću njihovih veza, čime se posljedično mijenja i vrijednost površinske te međupovršinske napetosti.Surface tension is a phenomenon caused by cohesive forces at the boundary between the liquid and gaseous phases. Due to the difference in intermolecular forces between the surface and the interior, droplets tend to minimize their surface area by assuming an ideal spherical shape. (1) Interfacial tension is a similar phenomenon that occurs at the boundary between two immiscible liquid phases, where adhesion forces dominate and contribute to their separation, and it is of particular importance in extraction processes. (2) In this work, the influence of temperature on the surface tension of selected solvents was investigated: water, sunflower oil, hydrophobic and hydrophilic DES (Deep Eutectic Solvents). In addition, the effect of temperature on the interfacial tension of three two-phase systems was investigated: water–sunflower oil, water–hydrophobic DES, and sunflower oil–hydrophilic DES. Measurements of surface and interfacial tension were carried out with a tensiometer, using the Wilhelmy plate and Du Noüy ring methods at defined temperatures. The experimental approach is based on the principle that a change in temperature has a dirrect effect on the kinetic energy of the molecules and the strength of their bonds, thereby changing the values of the surface and interfacial tension
The effect of treatment of Spartium junceum L. fibers on the properties of polycarbonate (PC)/ Spartium junceum L composites
No full textU današnje vrijeme, automobilska industrija, kao i mnoge druge, suočava se s dvostrukim izazovom – zadovoljiti izrazito stroge ekološke regulative, a istovremeno odgovoriti na zahtjeve tržišta za kvalitetnim i energetski efikasnijim vozilima. Kao jedan od najvećih zagađivača, industrijski sektor usmjeren je prema kružnom gospodarstvu i smanjenju negativnog utjecaja na okoliš. U tom kontekstu, biorazgradljivi kompozitni materijali postaju sve važnija alternativa već postojećim, konvencionalnim materijalima jer nude mogućnost smanjenja emisije CO2, uštede energije, lakše reciklaže i zbrinjavanja. U prvom dijelu rada dan je kratak uvod u tematiku, objašnjeno je što su polimeri i polimerni materijali, zatim su navedene osnovne informacije o materijalima korištenim za izradu PC/brnistra kompozita, njihovim svojstvima i primjeni, kao i opis tehnika koje su korištene za karakterizaciju. Također, objašnjen je i pojam biorazgradnje i njezina važnost u kontekstu održivog razvoja i smanjenja zagađenja okoliša. Drugi dio rada obuhvaća pripremu PC/brnistra kompozita, uključujući odabir polazišnih sirovina i detaljan postupak pripreme kompozita. Prikazani su rezultati ispitivanja pripremljenih PC/brnistra kompozita s neobrađenim i obrađenim vlaknima brnistre, pri čemu su korištene diferencijalna pretražna kalorimetrija (DSC), termogravimetrijska analiza (TGA) i FTIR spektroskopija za karakterizaciju faznih prijelaza i toplinske stabilnosti te kemijskog sastava kompozita. Kao zaključak, vlakna brnistre modificirana su alkalnom obradom s ciljem poboljšanja adhezije između vlakana i matrice u PC/brnistra kompozitima. Kompoziti PC/brnistra s obrađenim vlaknima pokazuju poboljšanu toplinska svojstva, što se pripisuje boljoj disperziji vlakana te snažnijoj interakciji s matricom u usporedbi s kompozitima koji sadrže neobrađena vlakna.Nowadays, the automotive industry, like many others, faces a dual challenge – meeting increasingly strict environmental regulations while simultaneously responding to market demands for high-quality and energy-efficient vehicles. As one of the largest polluters, the industrial sector plays a key role in shifting focus toward a circular economy and reducing its negative impact on the environment. In this context, biodegradable composite materials are becoming an increasingly important alternative to conventional materials, as they offer the potential to reduce CO2 emissions, save energy, and facilitate easier recycling and disposal. The first part of the work provides a brief introduction to the topic, explaining what polymers and polymeric materials are, followed by basic information about the materials used in the preparation of the PC/ Spartium junceum composites, their properties and applications, as well as a description of the techniques employed for material characterization. Additionally, the concept of biodegradation is explained, along with its importance in the context of sustainable development and environmental pollution reduction. The second part of the work focuses on the preparation of PC/ Spartium junceum composites, including the selection of raw materials and the composite preparation procedure. The results of characterization of the prepared composites are presented, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and FTIR spectroscopy were used to characterize phase transitions, thermal stability, and the chemical composition of the composites with untreated and treated Spartium junceum fibres. In conclusion, Spartium junceum fibres were modified through alkyl treatment to improve the adhesion between the fibres and the matrix in PC/Spartium junceum composites. PC/Spartium junceum composites containing treated fibres exhibit enhanced thermal properties, which is attributed to improved fibre dispersion and stronger interactions with the matrix compared to composites containing untreated fibres
Radiation effects on ceramics and its use in fusion reactors
No full textNuklearna fuzija, proces kojim zvijezde proizvode energiju, već je desetljećima cilj znanstvenih istraživanja u području energetike. Kako bi se ostvarila učinkovita i sigurna primjena fuzije na Zemlji, potrebno je razviti materijale koji će izdržati iznimne uvjete rada. Keramika se, zbog svojih kemijskih, mehaničkih i fizikalnih svojstava, izdvaja kao jedan od najvažnijih materijala u konstrukciji budućih fuzijskih reaktora. Glavni izvori zračenja u fuzijskom reaktoru su visokoenergetski neutroni i gama-zrake nastali tijekom fuzijske reakcije, a njihovo dugotrajno djelovanje može dovesti do promjena unutar strukture materijala, što posljedično mijenja njegova svojstva. Razumijevanje i precizna kontrola promjena u mikrostrukturi materijala ključni su za osiguranje dugotrajnosti i sigurnosti fuzijskih sustava. Veliki međunarodni projekt ITER (eng. International Thermonuclear Experimental Reactor) ima ključnu ulogu u razvoju budućih fuzijskih reaktora. Bavi se testiranjem materijala i tehnologija koje bi mogle biti korištene u budućim komercijalnim fuzijskim elektranama. Cilj ITER-a je ostvariti samoodrživu plazmu tako da oponaša proces proizvodnje energije kao u Suncu.Nuclear fusion, the process by which stars generate their energy, has been the focus of scientific research in the field of energy for decades. In order to achieve the efficient and safe application of fusion on Earth, it is necessary to develop materials capable of withstanding extreme operating conditions. Due to their chemical, mechanical, and physical properties, ceramics stand out as one of the most important materials for the construction of future fusion reactors. The main sources of radiation in a fusion reactor are high-energy neutrons and gamma rays produced during the fusion reaction. The prolonged exposure to this radiation can lead to changes within the material's structure, consequently altering its properties. Understanding and accurately controlling changes in the microstructure of materials is essential for ensuring the longevity and safety of fusion systems. The large international project ITER (eng. International Thermonuclear Experimental Reactor) plays a key role in the development of future fusion reactors. It is focused on testing materials and technologies that could be used in future commercial fusion power plants. ITER's objective is to achieve a self-sustaining plasma by replicating the energy production process that occurs in the Sun
Modeling of the solubility of vitamine D3 in different solvents
No full textU ovom radu opisano je modeliranje topljivosti vitamina D3, poznatog i pod nazivom kolekalciferol, u sljedećim otapalima: voda, etanol, 2-propanol, etilen-glikol, propilen-glikol, PEG-400, dietilen-glikol-monoetil-eter, 1-butanol, 2-butanol, etil-acetat, dimetilsulfoksid, metanol, acetonitril, aceton te 1-propanol. Ravnoteža kapljevina-krutina opisana je teorijskim modelima koeficijenta aktiviteta NRTL i Wilson, na temelju eksperimentalnih podataka o topljivosti kolekalciferola iz literature. Podaci su također opisani dvama empirijskim modelima; Apelblatovim i van´t Hoffovim. Rezultati su prikazani grafički u obliku T-x2, x2-T i lnγ-x2 dijagrama za teorijske modele, a za empirijske modele u T-x2 dijagramu. Na temelju grafičkih prikaza raspravljena je mogućnost primjene modela za sustave vitamin D3-otapalo u zadanom temperaturnom području. Nađeno je da model NRTL nije primjenjiv u zadanom obliku, za razliku od Wilsonova modela koji dobro korelira eksperimentalne podatke te načelno omogućuje procjenu topljivosti pri višim temperaturama od istraženih. Empirijski modeli dobro koreliraju podatke, no zbog empirijske prirode nije moguća ekstrapolacija u šire područje temperatura.This paper describes the modeling of the solubility of vitamin D3, also known as cholecalciferol, in the following solvents: water, ethanol, isopropanol, ethylene glycol, propylene glycol, PEG-400, 1-butanol, 2-butanol, ethyl acetate, DMSO, methanol, acetonitrile, acetone, and 1-propanol. The solid-liquid equilibria are described by the theoretically based Wilson and NRTL activity coefficient models, based on the experimental data on the solubility of cholecalciferol from the literature. The data were also described by two empirical models; Apelblat and van´t Hoff. The results are presented graphically in the form of T-x2, x2-T and lnγ-x2 diagrams for the theoretical models, and in T-x2 diagrams for the empirical models. On the basis of graphical representations, the possibility of applying each model for vitamin D3-solvent systems in the given temperature range is discussed. The application of experimental and empirical models in general and in a wider range of data for the given system is considered. It has been found that the NRTL model is not applicable in its given form, unlike the Wilson model which correlates experimental data well and theoretically allows for the estimation of solubility at higher temperatures than those investigated. Empirical models correlate data well, but due to their empirical nature, extrapolation to a wider temperature range is not possible