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Voltammetric characterization of main polyphenols in wine using modified carbon paste electrodes with TiO2 nanoparticles
No full textCiljevi ovog doktorskog rada su razvoj ugljikove elektrode modificirane s TiO2 nanočesticama (engl. modified carbon paste electrode, MCPE) za definiranje elektrokemijskih karakteristika glavnih polifenolnih spojeva prisutnih u vinima te razvoj algoritma za matematičku obradu podataka kao temelja elektrokemijskog senzora za identifikaciju i kvantifikaciju polifenolnog sastava vina. U prvom dijelu doktorskog rada ispitan je utjecaj vrste i količine veziva i modifikatora na fizičkokemijske i elektrokemijske karakteristike elektrodnog materijala. Elektrodni materijal pripremljen je od grafitnog praha te modificiran nanočesticama TiO2 uz dodatak tekućih ugljikovodika kao vezivnog sredstva. Primjenom fizičko-kemijskih i elektrokemijskih tehnika provedena je karakterizacija MCPE. Rezultati su pokazali da elektrodni materijal s 40 vol.% parafinskog ulja i 6-8 tež.% nanočestica TiO2 pokazuje najizraženije poboljšane karakteristike u odnosu na druge ispitivane elektrodne materijale. U drugom dijelu doktorskog rada ispitane su elektrokemijske karakteristike odabranih modelnih polifenolnih spojeva (galne kiseline, kofeinske kiseline, katehina, kvercetina i resveratrola) primjenom voltametrijskih metoda na MCPE (sastava: 40 vol.% parafinskog ulja i 8 tež.% nanočestica TiO2). Analizom voltametrijskog odziva ispitivanih analita, određeni su kinetički parametri oksidacije analita na elektrodi, linearni raspon detekcije analita, granica detekcije i granica kvantifikacije analita, stabilnost, ponovljivost i selektivnost primijenjene elektrode u odnosu na odabrani analit. U cilju poboljšanja obrade voltamograma, procjena standardnog potencijala oksidacije odabranog analita provedena je matematičkom obradom cikličkih voltamograma. Rezultati su pokazali da primjenom MCPE dobiven je izraženiji strujni odziv, niska vrijednost pozadinske struje, selektivnost i mogućnost detekcije vrlo niskih koncentracija analita uz stabilnost, reproducibilnost mjerenja. U trećem dijelu doktorskog rada provedena je elektrokemijska karakterizacija sedam odabranih prirodnih uzoraka vina (sorte bijelih, roze i crnih) te je predložen algoritam za matematičku obradu podataka. Voltamogrami prirodnih uzoraka vina ukazuju na ireverzibilnost elektrooksidacije polifenolnih spojeva u vinu. Rezultati su pokazali da MCPE pruža poboljšani i ponovljivi voltametrijski odgovor galne kiseline u uzorcima vina i što čini dobru osnovu za daljnji razvoj integriranog sustava senzora/podataka s mogućnošću šire primjene u vinarstvu u smislu određivanja galne kiseline kao važnog parametra za aromu vina.The aims of this doctoral thesis are to develop a modified carbon paste electrode with TiO2 nanoparticles (MCPE) to determine the electrochemical characteristics of the most important polyphenolic compounds in wines and to develop an algorithm for mathematical data processing as the basis for an electrochemical sensor to identify and quantify the polyphenolic composition of wine. In the first part of the doctoral thesis, the influence of the type and content of binders and modifiers on the physico-chemical and electrochemical characteristics of the electrode material was investigated. The electrode material was prepared from graphite powder modified with TiO2 nanoparticles with the addition of liquid hydrocarbons as binder material. The MCPE was characterized using physical, chemical and electrochemical techniques. The results showed that the electrode material with 40 vol.% of paraffin oil and 6-8 wt.% of TiO2 nanoparticles shows the most pronounced improved characteristics compared to other tested electrode materials. In the second part of the doctoral thesis, the electrochemical characteristics of selected model polyphenolic compounds (gallic acid, caffeic acid, catechin, quercetin, resveratrol) were tested on MCPE (composition: 40 vol.% paraffin oil and 8 wt.% TiO2 nanoparticles) using voltammetric methods. By analyzing the voltammetric response of the analytes, the kinetic parameters of the oxidation of the analyte at the electrode, the linear range of analyte detection, the detection limit and the limit of quantification of the analyte were determined and the stability, reproducibility and selectivity of the electrode used in relation to the selected analyte were tested. To improve the processing of the voltammograms, the evaluation of the standard oxidation potential of the selected analyte was carried out by mathematical processing of the cyclic voltammograms. The results showed that MCPE is characterized by a more pronounced current response, stability, reproducibility, low background current, selectivity and the ability to detect very low concentrations of the analytes. In the third part of the thesis, the electrochemical characterization of seven selected commercial wine samples (white, rosé and red wine) was performed and an algorithm for mathematical data processing was proposed. The voltammograms of the commercial wine samples indicate the irreversibility of electrooxidation of polyphenolic compounds in wine. The results showed that MCPE provides an improved and reproducible voltammetric response of gallic acid in wine samples and that constitutes a good basis for the further development of an integrated sensor/data system with the possibility of wider application in winemaking in terms of determining gallic acid as an important parameter for wine aroma
Swelling of epoxy composites in different solvents
No full textU završnom radu istraživano je bubrenje polimernih kompozita na temelju epoksidne matrice i tkanina načinjenih od staklenih ili bazaltnih vlakana, u pet različitih otapala (voda, 2-propanol, n-heksan, tetrahidrofuran, etil acetat), tijekom tri tjedna. Značajno bubrenje uočeno je u tetrahidrofuranu, što je dovelo do djelomičnog raslojavanja kompozita posebice u dijelovima ojačanim staklenim vlaknima. Rezultati bubrenja u skladu su s Hansenovom procjenom interakcija između otapala i polimerne matrice na temelju parametara topljivosti. Uzorci kompozita su prije i nakon bubrenja u tetrahidrofuranu i etil acetatu karakterizirani metodom diferencijalne pretražne kalorimetrije (DSC). Rezultati DSC karakterizacije su ukazali na malu rezidualnu reaktivnost sustava te postojanje fazno odvojenih struktura u epoksidnoj matrici. Apsorpcija otapala rezultirala je sniženjem staklišta epoksidne matrice.In this work, the swelling of polymer composites, based on an epoxy matrix and glass or basalt fibers reinforcements in the form of a fabric, was investigated in five different solvents (water, 2-propanol, n-hexane, tetrahydrofuran, ethyl acetate) for three weeks. Significant swelling was observed in tetrahydrofuran, which led to partial delamination of the composite, especially in the glass fiber reinforced parts. The swelling results are consistent with Hansen's assessment of solvent-polymer matrix interactions based on solubility parameters. The composite samples were characterized before and after swelling in tetrahydrofuran and ethyl acetate by the differential scanning calorimetry (DSC) method. The results of the DSC characterization indicated a low residual reactivity of the system and the existence of phase-separated structures in the epoxy matrix. Solvent absorption resulted in a decrease in the glass transition temperature of the epoxy matrix
Application of immobilized TiO2 materials for the photocatalytic degradation of procaine
No full textProkain, tercijarni aminoester aromatske kiseline, jedan je od često prisutnih farmaceutika u otpadnim vodama. Zbog visoke hidrofilnosti i niske bioraspoloživosti, farmaceutike je veoma teško, konvencionalnim metodama, ukloniti iz otpadnih voda. Iz tog se razloga naglasak stavlja na napredne oksidacijske procese, kojima se generiraju reaktivne vrste koje imaju sposobnost ukloniti, odnosno smanjiti koncentraciju zagađivala. Fotokataliza, kao ekološki prihvatljiva metoda, sve se više primjenjuje te se temelji na iskorištavanju solarnog spektra uz fotokatalitički materijal. Najprimjenjivaniji fotokatalitički materijal je titanijev (IV) oksid (TiO2). Riječ je o oksidu koji se uvelike koristi zbog inertnosti, visoke fotostabilnosti, netoksičnih svojstava te visoke fotoaktivnosti. Takav materijal može biti dopiran višeslojnim ugljikovim nanocijevima (MWCNT), što rezultira poboljšanom fotokatalitičkom aktivnošću. U ovome su radu ispitani mnogi čimbenici poput početne koncentracije reaktanta, koncentracije kisika, pH-vrijednosti, prirode katalizatora i intenziteta svjetlosti na proces fotokatalitičke razgradnje prokaina. Primjenom TiO2 fotokatalizatora, optimalni uvjeti fotorazgradnje postižu se pri koncentraciji prokaina od 5 mg dm^-3 i pH-vrijednosti 7, dok se primjenom TiO2/MWCNT fotokatalizatora optimalni uvjeti postižu pri istoj koncentraciji prokaina i pH-vrijednosti 4. Nadalje, analizom varijance ispitana je značajnost modela te je primjenom modela odzivnih površina zaključeno kako su temperatura i pH-vrijednost otopine značajni parametri modela. Kinetika fotokatalitičke razgradnje ispitana je dodatkom hidrogenkarbonata, nitrata, klorida i huminskih kiselina. Također, ustanovljeno je da je kinetika razgradnje prokaina usporena simultanim utjecajem iona i huminskih kiselina. Korištenjem realne matice vode, vrijeme polurazgradnje je dulje od vremena polurazgradnje u MilliQ vodi, zbog postojanja drugih zagađivala te kompetitivnog vezanja na aktivna mjesta fotokatalizatora. Razgradnjom prokaina, upotrebom TiO2 fotokatalizatora, nastaju tri razgradna produkta, dok upotrebom TiO2/MWCNT fotokatalizatora, nastaju četiri produkta razgradnje, čije su strukture i mehanizmi razgradnje predloženi nakon MS/MS analize. Softverskim alatom T.E.S.T. procijenjena je toksičnost prokaina i njegovih razgradnih produkata.Procaine, a tertiary amino ester of an aromatic acid, is one of the most frequently present pharmaceuticals in wastewater. Due to its high hydrophilicity and low bioavailability, pharmaceuticals are very difficult to remove from wastewater using conventional methods. For this reason, the focus is placed on advanced oxidation processes that generate reactive species capable of removing or reducing the concentration of contaminants. Photocatalysis is increasingly being used as an environmentally friendly method and is based on the use of the solar spectrum with a photocatalytic material. The most commonly used photocatalytic material is titanium dioxide (TiO2). This oxide is widely used due to its inertness, high photostability, non-toxic properties, and high photoactivity. Such a material can be doped with carbon nanotubes (MWCNT), which leads to improved photocatalytic activity. In this study, many factors such as the initial concentration of reactant, oxygen concentration, pH, type of catalyst and light intensity were investigated on the process of photocatalytic degradation of procaine. When using a TiO2 photocatalyst, the optimal conditions for photodegradation are achieved at a procaine concentration of 5 mg dm^-3 and a pH value of 7, while using the TiO2/CNT photocatalyst, the optimal conditions are achieved at the same procaine concentration and a pH value of 4. Furthermore, analysis of variance examined the significance of the model, and using response surface methodology, it was concluded that temperature and pH value of the solution are significant parameters of the model. The kinetics of photocatalytic degradation were investigated by adding bicarbonates, nitrates, chlorides, and humic acids. It was also found that the degradation kinetics of procaine is slowed down by the simultaneous influence of ions and humic acids. When using a real water matrix, the half-life is longer than the half-life in MilliQ water, which is due to the presence of other contaminants and competitive binding to the active sites of the photocatalyst. The degradation of procaine with the TiO2 photocatalyst leads to three degradation products, while four degradation products are formed with the TiO2/MWCNT photocatalyst, whose structures and degradation mechanism were proposed after MS/MS analysis. The software tool T.E.S.T. was used to estimate the toxicity of procaine and its degradation products
Strukturna karakterizacija MXene-a dobivenih različitim metodama sinteze
No full textThe thesis aims to characterize new member of the 2D nanomaterials, MXene. The scientific question that’s been addressed throughout this study is addressing the challenges of HF synthesis of MXene such as environmental and safety concerns because of the hazardous nature of fluoride and emphasizing the importance of new synthesis techniques for fluorine-free MXene production. Specifically, the study investigates whether mechanochemical synthesis is a successful alternative. The results demonstrate successful partial etching of MXene on the surface of Ti3AlC2 by mechanochemical method. Surface characterization using Raman spectroscopy confirms the presence of new rovibronic states in the newly formed structure with the appearance of characteristic MXene Raman shift at 120 cm^-1. Scanning electron microscopy (SEM) distinguishes the morphology of MXenes from that of the MAX phase. Energy dispersive X-ray spectroscopy (EDX) affirms the etching of Al, corroborated with the newest Low energy ion scattering spectroscopy (LEIS) technique confirming the changes in aluminium content on the surface. Atomic force microscopy (AFM) implies the formation of a monolayer MXene structure. In conclusion, the study successfully achieved partial delamination of MXene, validating the efficiency of the mechanochemical approach in producing fluorine-free MXenes, applicable in various fields.Cilj ovog rada je karakterizacija novih 2D nanomaterijala, odnosno MXene-a, što uključuje znanstvene i opće aspekte vezane uz ove materijale. Znanstvena problematika koja se obrađuje u ovom istraživanju odnosi se na izazove sinteze MXene-a s HF-a, kao što su ekološki i sigurnosni problemi zbog prirode fluorida. Također, naglašena je važnost novih tehnika sinteze MXene-a koje ne uključuju fluor te se istražuje je li mehanokemijska sinteza uspješna alternativa postojećim metodama sinteze. Rezultati pokazuju uspješno djelomično raslojavanje MAX faze Ti3AlC2. Površinska karakterizacija pomoću Raman spektroskopije potvrđuje prisutnost novih rovibroničkih stanja u novonastaloj strukturi s pojavom karakterističnog MXene Ramanovog pomaka na 120 cm^-1. Skenirajuća elektronska mikroskopija (SEM) razlikuje morfologiju MXene-a od one MAX faze. Energijski disperzivna rendgenska spektroskopija (EDX) potvrđuje uklanjanje aluminija, što je dodatno potvrđeno tehnikom raspršenja niskoenergetskih iona (LEIS) koja potvrđuje promjene u sadržaju aluminija na površini MAX faze. Mikroskopija atomskih sila (AFM) implicira formiranje jednoslojne MXene strukture. Na temelju dobivenih rezultata može se zaključiti da je uspješno provedena djelomična delaminacija MXene-a na površini MAX faze. Na taj način je potvrđena dobra učinkovitost mehanokemijskog pristupa koji ne uključuje upotrebu fluorida u proizvodnji MXene-a
Estimation of the ecotoxicity of cyanide on green microalgae and bacteria
No full textCijanidi su spojevi često korišteni u raznim industrijskim procesima kao što su rudarstvo i koksna industrija. Ispuštanjem otpadnih voda ulaze u okoliš, čime predstavljaju značajnu prijetnju vodenim ekosustavima. Jednom kada dospiju u vodene organizme, cijanidi pokazuju visoku toksičnost za žive organizme, ometajući stanično disanje i dovodeći do ozbiljnih ekoloških i zdravstvenih rizika. Zbog njihovih toksičnih učinaka, ključno je ukloniti cijanide iz onečišćene vode kako bi se zaštitili okoliš i ljudsko zdravlje. Uklanjanje cijanida iz voda može se učinkovito postići raznim kemijskim i fizikalnim metodama obrade voda, uključujući kloriranje i ozonizaciju te raznim biološkim metodama. Biološke metode predstavljaju održiv i ekološki prihvatljiv pristup, koristeći metaboličke sposobnosti mikroorganizama za razgradnju cijanida. Za određivanje potrebe provođenja određene metode, od velike su važnosti testovi ekotoksičnosti. Testovima ekotoksičnosti određuju se minimalne prihvatljive koncentracije tvari u ekosustavima, pri kojima tvari nemaju štetan učinak. Provođeni su ispitivanjima na testnim organizmima u kontroliranim laboratorijskim uvjetima. U ovom radu testovi ekotoksičnosti provedeni su koristeći dva testna organizma – bakteriju Pseudomonas putida i mikroalgu Chlorella sp. Određena je CFU vrijednost, inhibicija rasta te EC20 i EC50 vrijednosti. Dobiveni rezultati ukazuju na visoku osjetljivost oba testna organizma na prisutnost cijanida, potvrđujući njihovu prikladnost za procjenu štetnih učinaka.Cyanides are compounds commonly used in various industrial processes such as mining and coke production. When released into the environment through wastewater discharge, they pose a significant threat to aquatic ecosystems. Once they enter aquatic organisms, cyanides exhibit high toxicity, disrupting cellular respiration and leading to severe ecological and health risks. Due to their toxic effects, it is crucial to remove cyanides from contaminated water to protect the environment and human health. Cyanide removal from water can be effectively achieved through various chemical and physical water treatment methods, including chlorination and ozonation, as well as various biological methods. Biological methods represent a sustainable and environmentally friendly approach, utilizing the metabolic capabilities of microorganisms to degrade cyanides. Ecotoxicity tests are of great importance for determining the necessity of a particular method. Ecotoxicity tests determine the minimum acceptable concentrations of substances in ecosystems at which they do not have harmful effects. These tests are conducted on test organisms under controlled laboratory conditions. In this study, ecotoxicity tests were conducted using two test organisms – the bacterium Pseudomonas putida and the microalga Chlorella sp. The CFU (colony-forming units) value, growth inhibition, and EC20 and EC50 values were measured. The obtained results indicate a high sensitivity of both test organisms to the presence of cyanides, confirming their suitability for assessing harmful effects
Application of Fe3O4/SiO2/TiO2 nanocomposite for magnetic solid-phase extraction of pharmaceuticals from water
No full textNapredak farmaceutske industrije, dostupnost raznih farmaceutika na tržištu, porast broja stanovnika te nedovoljno učinkoviti sustavi za obradu otpadnih voda doveli su do pojave farmaceutika u okolišu, konkretno u vodi i tlu. Farmaceutici su u okolišu prisutni u malim količinama, ali i te male količine dovoljne su za nepovoljan utjecaj farmaceutika na zdravlje ljudi, biljaka i životinja. Zbog svega navedenog, radi se na pronalaženju metode koja će biti prihvatljiva za uklanjanje farmaceutika iz vode. U ovom diplomskom radu ispitivana je ekstrakcija smjese 12 farmaceutika (amoksicilin, atenolol, β-estradiol, deksametazon, diazepam, diklofenak, karbamazepin, ofloksacin, prokain, sulfametazin, sulfametoksazol i torasemid) iz vode pomoću Fe3O4/SiO2/TiO2 nanokompozitnih magnetnih čestica. Ovaj magnetni sorbens novi je tip sorbensa koji se primjenjuje za magnetsku ekstrakciju čvrstom fazom. Ovim radom prvo su određeni optimalni uvjeti sorpcije ispitivane smjese farmaceutika na korištene magnetne čestice nakon čega se pristupilo određivanju otapala za eluiranje kao i potrebnog volumena otapala za eluiranje smjese farmaceutika s magnetnih čestica. U tu svrhu ispitana je kinetika sorpcije, određena je optimalna početna koncentracija smjese farmaceutika te optimalno vrijeme potrebno za sorpciju, optimalan pH, temperatura, ionska jakost te masa magnetnih čestica. Određena optimalna početna koncentracija smjese farmaceutika (pH vrijednosti 6, bez ionske jakosti) je 1 mg/L, vrijeme mućkanja 1 sat pri 25 °C na masi od 20 mg magnetnih čestica. Određeni optimalni uvjeti primijenjeni su na sorpciju iste smjese farmaceutika na magnetne čestice s otiskom sulfametoksazola. Općenito, na magnetnim česticama s otiskom sulfametoksazola postignuta je bolja učinkovitost sorpcije i to posebice molekule sulfametoksazola što je bilo očekivano. Nakon sorpcije ispitana je i desorpcija sorbiranih farmaceutika s površine magnetnih čestica eluiranjem s različitim otapalima (metanol, etanol, acetonitril, izopropanol, aceton, voda, etil-acetat, heksan i diklormetan). Najboljim otapalom za eluiranje pokazao se metanol i to postupkom eluiranja u tri koraka; najprije s 1 mL, zatim s 2x 2 mL. Odabrano otapalo primijenjeno je i za desorpciju smjese farmaceutika s magnetnih čestica s otiskom sulfametoksazola gdje su također postignuta dobra iskorištenja. Kvantitativno određivanje učinkovitosti koraka sorpcije i desorpcije ostvareno je primjenom je tekućinske kromatografije visoke djelotvornosti s DAD detektorom (HPLC-DAD).The progress of the pharmaceutical industry, the availability of various pharmaceuticals in pharmacies, the increase in the population, and insufficiently efficient wastewater treatment systems have led to the presence of pharmaceuticals in the environment, especially in water and soil. Pharmaceuticals are present in the environment only in small quantities, but even these small quantities are enough to affect the health of himans, plants and animals.
For these reasons, we are working to find an acceptable method of removing pharmaceuticals from water. In this work, the extraction of a mixture of 12 pharmaceuticals (amoxicillin, atenolol, β- estradiol, dexamethasone, diazepam, diclofenac, carbamazepine, ofloxacin, procaine, sulfamethazine, sulfamethoxazole and torasemide) from water was studied using Fe3O4/SiO2/TiO2 nanocomposite magnetic particles. This magnetic sorbent is a new type of sorbent used for magnetic solid-phase extraction. Firstly, the optimal conditions for the sorption on the investigated pharmaceutical mixture on the used magnetic particles were determined. Subsequently, the solvent for the elution of the pharmaceutical mixture from the magnetic particles and the required volume of the elution solvent were determined. For this purpose, the kinetics of sorption were investigated, the optimal initial concentration of the pharmaceutical mixture and the optimal time required for sorption, the optimal pH, the temperature, the ionic strength and the mass of the magnetic particles were determined.
The determined optimal initial concentration of the pharmaceutical mixture (pH 6, without ionic strength) is 1 mg/L, shaking time 1 hour at 25 °C with mass of 20 mg magnetic particles. Certain optimal conditions were applied to the sorption of the same pharmaceutical mixture on magnetic particles with sulfamethoxazole imprinted polymer. In general, better sorption efficiency was obtained on magnetic particles with sulfamethoxazole imprinted polymer, especially for sulfamehoxazole, which was expected. After sorption, the desorption of the sorbed pharmaceuticals from the surface of the magnetic particles was tested by elution with different solvents (methanol, ethanol, acetonitrile, isopropanol, acetone, water, ethyl acetate, hexane and dichloromethane). Methanol proved to be the best eluent, with a three-step elution process; first with 1 mL, then 2x 2 mL. The selected solvent was also used for the desorption of a mixture of pharmaceuticals with magnetic particles imprinted with sulfamethoxazole, where good yields were also obtained. The quantitatively determination of the efficiency of the sorption and desorption steps was carried out using high-performance liquid chromatography with DAD detector (HPLC-DAD)
Testing the biodegradability of biopolymers in soil
No full textRazvojem industrije dolazi do stvaranja velikih količina otpada kojeg ponekad nije moguće sanirati, te velik dio otpada završi u prirodi, gdje predstavlja ekološki problem. Taj problem se može riješiti recikliranjem i pravilnim saniranjem otpada, te uporabom biorazgradljivih materijala. Biorazgradljivi materijali se mogu razgrađivati u okolišu primjenom različitih mikroorganizama, te imaju pozitivan utjecaj na okoliš. Neki od biorazgradljivih materijala su polimerni materijali, koji imaju široku primjenu te se koriste u mnogobrojnim sektorima, najviše u ambalažnoj industriji i poljoprivredi. U ovom istraživanju ispitana je biorazgradljivost polimera, odnosno termoplastičnog škroba (TPS), polilaktida (PLA), polihidroksialkanoata (PHA), polikaprolaktona (PCL), te njihovih mješavina. Uzorci su promatrani prije i poslije procesa biorazgradnje polarizacijskim mikroskopom, te je izračunata promjena mase tijekom 56 dana procesa biorazgradnje. Uzorci su također analizirani FTIR-ATR spektroskopijom. Dobiveni rezultati pokazuje da je tijekom 56 dana procesa došlo do biorazgradnje svih polimernih materijala i njihovih mješavina. Zbog svojih svojstava, neki polimeri su bolje razgradivi, poput TPS-a koji je bolje razgradiv od PLA.With the development of industry, large amounts of waste are created, which sometimes cannot be remediated, and a large part of the waste ends up in nature, where it is an environmental problem. This problem can be solved by recycling and proper remediation of waste, and the use of biodegradable materials. Biodegradable materials can be degraded in the environment using various microorganisms and have a positive impact on the environment. Some of the biodegradable materials are polymeric materials, which have a wide range of applications and are used in many sectors, mostly in the packaging industry and agriculture. In this study, the biodegradability of polymers, i.e. thermoplastic starch (TPS), polylactide (PLA), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), and their mixtures were examined. Samples were observed before and after the biodegradation process with a polarization microscope, and the change in mass was monitored during 56 days of the biodegradation process. Also, the samples were analyzed by FTIR-ATR spectroscopy. The results obtained show that during the 56 days of the process, biodegradation of all polymeric materials and their mixtures occurred. Due to their properties, some polymers are more degradable, such as TPS, which is better degradable than PLA
Preparation of thermoplastic starch blends from solution and by melt mixing
No full textZbog neprikladnog odlaganja polimernog otpada, dolazi do sve većeg zagađenja Zemlje i nastajanja ekoloških problema. Nerazgradivi polimeri se zadržavaju u okolišu, te ispuštanjem toksičnih tvari ugrožavaju živa bića prisutna u njemu. Zbog toga se zaziva sve veća primjera biorazgradivih polimernih materijala, koji se u okolišu razgrađuju pomoću mikroorganizama ili atmosferilija. Nerijetko određeni biorazgradivi polimer, unatoč sposobnosti razgradnje, nije primjenjiv zbog loših toplinskih i mehaničkih svojstava. Materijal traženih svojstava dobiva se pripravom polimernih mješavina dvaju ili više polimera. Konkretno u ovom radu, pripravljane su mješavine termoplastičnog škroba (TPS), dobivenog plastifikacijom običnog krumpirovog škroba, i sintetskog biorazgradivog polimera polikaprolaktona (PCL). Na uzorcima dobivenih polimernih mješavina provedena je mehanička analiza na kidalici, te toplinske metode diferencijalne pretražne kalorimetrije (DSC) i termogravimetrije (TGA). Obradom rezultata, pokazano je da se mješavine s udjelom škroba do 20% mogu koristiti kao zamjene za čisti polikaprolakton, čime se snižavaju troškovi proizvodnje a povećava biorazgradivost materijala.Improper polymer waste disposal contributes to pollution and causes environmental problems. Non-biodegradable polymers accumulate in the environment and release toxic substances which can harm living organisms. Therefore, biodegradable polymeric materials are preferred as they can be degraded naturally by the action of microorganisms or environmental conditions. However, a biodegradable polymer often has poor mechanical or thermal properties and may not be the most suitable. For this reason, two or more polymers are mixed to make a new material with improved properties. This paper presents preparation of blends of thermoplastic starch (TPS) produced by plasticization of normal potato starch and a synthetic biodegradable polymer, polycaprolactone (PCL). Samples of these polymer blends were subjected to mechanical analysis on the universal testing machine, and differential scanning calorimetry (DSC) and thermal-gravimetric analysis (TGA). The results showed that the blend with up to 20% starch content may be used as a substitute for pure polycaprolactone, which can reduce production costs and enhance biodegradability of the material
Green synthesis of 2-substituted benzoxazole derivatives with antitumoral potential
No full textU ovom radu opisana je konvencionalna i zelena sinteza te strukturna karakterizacija 2-supstituiranih derivata benzoksazola s potencijalnim antitumorskim djelovanjem. O-alkilirani benzaldehidi (1-4) dobiveni su reakcijom 4-hidroksibenzaldehida i 4-hidroksi-3-
metoksibenzaldehida s odgovarajućim alkilirajućim reagensom. Zatim su reakcijom O-alkiliranih benzaldehida (1-4) i o-aminofenola pripravljeni derivati Schiffovih baza (5-7). Reakcijom oksidativne ciklizacije Schiffovih baza (5-7) dobiveni su 2-supstituirani derivati benzoksazola (8-9). Sinteze svih pripravljenih spojeva su provedene konvencionalno i primjenom zelenih metoda (mikrovalovima i ultrazvukom potpomognuta sinteza, mehanokemijska sinteza i sinteza u niskotemperaturnom eutektičkom otapalu).
Strukturna analiza priređenih spojeva provedena je 1H- i 13C-NMR spektroskopijom.This work describes the conventional and green synthesis as well as structural characterization of 2-substituted benzoxazole derivatives with potential antitumor activity. O-alkylated benzaldehydes (1-4) were obtained by the reaction of 4-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde with the appropriate alkylating reagent. Derivatives of Schiff's bases (5-7) were prepared by reaction of O-alkylated benzaldehydes (1-4) with o-aminophenols. By oxidative cyclization reaction of Schiff bases (5-7), 2-substituted benzoxazole derivatives (8-9) were obtained. The syntheses of all prepared compounds were carried out conventional and by using green methods (microwave- and ultrasound-assisted synthesis, mechanochemical synthesis and synthesis in deep eutectic solvent).
The structural analysis of prepared compounds were performed by 1H- and 13C-NMR spectroscopy
Membrane preparation with 3D technology
No full textU današnje vrijeme sve češće se susrećemo s pojmom klimatskih promjena u naslovima članaka, na televiziji i na društvenim mrežama. Pojam klimatske promjene sa sobom veže i problem nedostatka pitke vode. Potencijal dobivanja pitke vode iz morske vode procesom desalinacije najperspektivnije je rješenje problematike nedostatka pitke vode, pogotovo u sušnim područjima. U ovom radu naglasak je na novoj metodi priprave membrana za desalinaciju putem 3D tehnologije, metodama aditivne tehnologije i vrstama membrana za desalinaciju. Metode aditivne tehnologije na kojima će se bazirati novi primjeri membrana su selektivno lasersko sinteriranje (SLS) na bazi praha, digitalna obrada svjetlom (DLP) temeljena na fotopolimerizaciji (fotoočvršćivanje) te tiskanje elektrosprejom. 3D tehnologija trenutno je u razvoju pa se još uvijek koriste konvencionalne metode priprave membrana jer su povoljnije od neistraženih i skupocjenih istraživanja novih metoda izrade membrana. Kroz rad su naglašene prednosti koje nosi 3D ispis membrana te važnost u pogledu čim boljih karakteristika membrana poput zadržavanja soli i propusnosti vode. Neke od prednosti 3D ispisa su brzina izrade, automatizacija i veća ekološka prihvatljivost.Nowadays, we encounter the term climate change more and more often in the titles of articles, on television and in social networks. The concept of climate change brings with it the problem of lack of drinking water. The potential of obtaining potable water from seawater through the desalination process is the mostpromising solution to the problem of the lack of potable water, especially in arid areas. In this paper, the emphasis is on a new method of preparing membranes for desalination using 3D technology, methods of additive technology and types of membranes for desalination. Additive technology methods on which the new examples of membranes will be based are powder-based selective laser sintering (SLS), digital light processing (DLP) based on photopolymerization (photocuring), and electrospray printing. 3D technology is currently under development, therefore membranes made by conventional methods are mostly used because they are more favorable than the unexplored and expensive research of new methods of making membranes. The work will emphasize the advantages of 3D printing of membranes and the importance of better membrane characteristics such as salt rejection and water permeability. Some of the advantages of 3D printing are production speed, automation and greater environmental acceptability