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Vapor-liquid equilibria in the two-component system aceton(1) - water(2)
No full textTraženi su znanstveni radovi u kojima su objavljeni eksperimentalni podatci o ravnoteži para-kapljevina u sustavu aceton (1) – voda (2). Pronađeno je 28 skupova podataka od kojih su četiri izmjerena pri izotermnim uvjetima, a ostali pri izobarnim. Pronađeni podatci testirani su integralnim i Van Nessovim testom konzistentnosti, a sedam skupova nije prošlo test konzistentnosti, svi pri višim temperaturama i tlakovima. Zatim su se određivali linearno-temperaturno ovisni parametri za modele koeficijenta aktivnosti: Wilsonov model te modele NRTL i UNIQUAC. Za određivanje parametara modela upotrijebljeni su izotermni podatci Bearea i Ramalha izmjereni pri 25 °C i 75 °C, dok je parametar neslučajnosti u modelu NRTL fiksiran na 0,3. Najmanju vrijednost funkcije cilja dao je model NRTL. Na kraju su se uspoređivali modelni dijagrami vrenja i modelni ravnotežni dijagrami s podatcima Al-Sahhafa radi provjere valjanosti modela. Uočeno je malo odstupanje – modelni dijagrami vrenja većinom daju nešto viša kapljišta i vrelišta od eksperimentalnih što je najuočljivije pri
20 000 Pa, a najmanje uočljivo pri atmosferskom tlaku. Modelni se ravnotežni dijagrami pri atmosferskom tlaku, tlaku od 80 000 Pa i 60 000 Pa dobro slažu s Al-Sahhafovim podatcima, dok pri tlaku od 40 000 Pa i 20 000 Pa postoji malo odstupanje, tj. pri udjelima acetona većim od približno 10 % modelni ravnotežni dijagrami većinom daju nešto viša kapljišta i vrelišta od eksperimentalnih.Research papers with experimental data on the vapor-liquid equilibrium in the
acetone (1) – water (2) system were looked for. 25 data sets were found, four of which were measured under isothermal conditions, and the rest under isobaric conditions. The data found were tested with integral and Van Ness consistency tests, and seven sets did not pass the consistency test, all of them measured at higher temperatures and pressures. The linear temperature-dependent parameters for the Wilson, NRTL and UNIQUAC activity coefficient models were determined. To determine the parameters of the model, the isothermal data of Beare and Ramalho measured at 25 °C and 75 °C, respectively, were used, while the non-randomness parameter in the NRTL model was fixed at 0.3. The lowest value of the objective function was obtained by the NRTL model. Finally, model temperature-composition phase diagrams and model equilibrium diagrams were compared with Al-Sahhaf data to check the validity of the models. Small deviations were observed – the model boiling diagrams mostly gave slightly higher dew and bubble points than the experimental ones; the difference was most noticeable at 20,000 Pa, and least noticeable at atmospheric pressure. The model equilibrium diagrams at atmospheric pressure, pressure of 80,000 Pa and 60,000 Pa agreed well with Al-Sahhaf's data, while there were small deviations noticeable at pressures of 40,000 Pa and 20,000 Pa, i.e. at acetone mole fractions greater than approximately 10% the model equilibrium diagrams mostly gave slightly higher dew points and bubble points than experimental ones
Bioremediation of water polluted with microplastics by bacteria isolated from the environment
No full textMikroplastika (MP) je onečišćujuća tvar koja izaziva zabrinutost znanstvene zajednice zbog svoje sveprisutnosti u okolišu. Izvori MP-a su brojni, a izloženost vodenih organizama sve veća, što dovodi do potrebe procjene rizika. Kako MP ne bi negativno utjecala na vodene organizme, potrebno ju je ukloniti iz okoliša, a jedan od perspektivnih postupaka je bioremedijacija primjenom bakterija, kvasaca, plijesni ili mješovitog konzorcija. U ovoj disertaciji najprije su provedeni testovi ekotoksičnosti za pet vrsta MP-a: polietilen (PE), polipropilen (PP), polistirena (PS), poli(vinil-klorid) (PVC) i poli(etilen-tereftalat) (PET), na mikroalge rodova Chlorella i Scenedesmus, bakteriju Pseudomonas putida te kvasac Saccharomyces cerevisiae. PS i PVC MP pokazali su najveći toksični utjecaj na testne organizme, a najosjetljiviji je bio Saccharomyces cerevisiae. Provedena su i istraživanja bioremedijacije vode onečišćene MP-om primjenom bakterija Bacillus cereus, Bacillus subtilis, Pseudomonas alcaligenes i Delftia acidovorans, izoliranih iz okoliša obogaćenog
MP-om. Pri tome je preliminarno ispitan utjecaj sedam parametara:
koncentracije (50 – 1000 mg/L) i veličine (100 – 700 μm) MP čestica, broja okretaja rotacijske tresilice (100 – 200 o/min), pH medija (6 – 8), temperature medija (15 – 25 °C), optičke gustoće (0,1 – 0,5) te dodatka glukoze (0 – 100 mg/L). Statističkom analizom za svaki polimer odabrana su tri najznačajnija čimbenika te je na njima provedena optimizacija biorazgradnje. Kod tretmana bakterijom Bacillus cereus utvrđeno je da su tri statistički najznačajnija parametra u biorazgradnji PS MP-a veličina i koncentracija MP-a te broj okretaja rotacijske tresilice (optimalno {413,29 μm; 66,20 mg/L; 100,45 o/min}). Kod tretmana PVC MP-a značajnim su se pokazali veličina i koncentracija MP-a te optička gustoća (optimalno {400,00 μm; 658,40 mg/L; 0,40}). Analiza biorazgradnje MP-a bakterijom Bacillus subtilis ukazala je na značajnost veličine MP-a, broja okretaja tresilice i optičke gustoće kod biorazgradnje PS MP-a (optimalno {440,65 μm; 162,12 o/min; 0,50}), dok su kod PVC MP-a to bili pH medija, broj okretaja tresilice i optička gustoća (optimalno {8,00; 200 o/min; 0,50}). Za biorazgradnju PS MP-a primjenom Pseudomonas alcaligenes značajnim su se pokazali broj okretaja tresilice, veličina MP čestica i optička gustoća (optimalno {161,08 o/min; 334,73 μm; 0,35}), a kod biorazgradnje PVC-a to su bili pH medija, koncentracija MP-a i optička gustoća (optimalno {8,00; 50,00 mg/L; 0,50}). Konačno, kod biorazgradnje bakterijom Delftia acidovorans dobiveni su isti značajni parametri za PS MP i PVC MP. To su pH medija, broj okretaja tresilice i optička gustoća (optimalni uvjeti {7,99; 104,93 o/min; 0,46}, odnosno {8,00; 200,00 o/min; 0,50}). Prema navedenom, primijenjene bakterijske kulture izolirane iz okoliša imaju sposobnost razgradnje MP-a.Microplastics (MP) is a pollutant of concern in the scientific community due to its ubiquity in the environment. The sources of MP are numerous and exposure to aquatic organisms is increasing, so a risk assessment is needed. To ensure that MP does not have adverse effects on aquatic organisms, it must be removed from the environment, and one of the most promising methods is bioremediation with bacteria, yeasts, molds, or a mixed consortium.
In this dissertation, ecotoxicity tests were first conducted for five types of MP: polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(vinyl-chloride) (PVC), and poly(ethylene-terephthalate) (PET) with microalgae of the genera Chlorella and Scenedesmus, the bacterium Pseudomonas putida, and the yeast Saccharomyces cerevisiae. PS and PVC MP showed the highest ecotoxic effects on the test organisms, and Saccharomyces cerevisiae was the most sensitive. Studies on bioremediation of MP contaminated water were also performed with the bacteria Bacillus cereus, Bacillus subtilis, Pseudomonas alcaligenes and Delftia acidovorans isolated from the MP enriched environment. The influence of seven parameters was pre-tested: concentration (50 – 1000 mg/L) and size (100 – 700 μm) of particles of MP, agitation speed of the rotary shaker (100 – 200 rpm), pH of the medium
(6 – 8), temperature of the medium (15 – 25 °C), optical density (0.1 – 0.5) and addition of glucose (0 – 100 mg/L). The three most significant parameters were selected for each polymer by statistical analysis, and biodegradation optimization was performed based on these parameters. For the treatment with the bacterium Bacillus cereus, it was found that the three most statistically significant parameters for the biodegradation of PS MP were the size and concentration of MP and the agitation speed of the rotary shaker (optimum {413.29 μm; 66.20 mg/L; 100.45 rpm}). For the treatment of PVC MP, the size and concentration of MP and the optical density (optimum {400.00 μm; 658.40 mg/L; 0.40}) were found to be significant. Analysis of the degradation of MP by the bacterium Bacillus subtilis showed that the size of MP, the agitation speed of the rotary shaker, and the optical density were significant for the biodegradation of PS MP (optimal {440.65 μm; 162.12 rpm; 0.50}), while for PVC MP it was the pH of the medium, the number of agitation speed of the rotary shaker, and the optical density (optimal {8.00; 200 rpm; 0.50}). For biodegradation of PS MP by Pseudomonas alcaligenes, the nu agitation speed of the rotary shaker, the size of the MP particles, and the optical density (optimal {161.08 rpm; 334.73 μm; 0.35}) were significant, while for biodegradation of PVC, the pH of the medium, the MP concentration, and the optical density (optimal {8.00; 50.00 mg/L; 0.50}) were significant. Finally, in the biodegradation by the bacterium Delftia acidovorans, the same significant parameters were obtained for PS MP and PVC MP. These were the pH of the medium, the agitation speed of the rotary shaker and the optical density (optimal conditions {7.99; 104.93 rpm; 0.46} and {8.00; 200.00 rpm; 0.50}, respectively). Accordingly, the bacterial cultures, isolated from the environment, are capable of degrading MP
Optimization of intense pulsed light parameters for processing silver nanoparticle films on glass substrates
No full textU ovom radu je provedena usporedba dviju metoda obrade inkjet tiskane nanosrebrne tinte na staklenoj podlozi. U peći za žarenje provedena je klasična toplinska obrada tankih filmova, a pomoću sustava za generiranje intenzivne pulsirajuće svjetlosti fototermalna obrada. Preliminarnim ispitivanjima definirane su granične vrijednosti ulaznih parametara potrebnih za dizajniranje eksperimenta. Korištenjem programa Design-Expert predložen je minimalni broj eksperimenata za određivanje optimalnih uvjeta temperature i vremena obrade za toplinski proces, odnosno energije i broja bljeskova za fototermalni proces obrade. Također su određeni parametari s ključnim utjecajem na kvalitetu i električnu vodljivost nanosrebrnog tankog filma inkjet ispisanog na staklenoj podlozi. Kako bi se utvrdila debljina sloja ispisanog materijala prije i nakon obrade te njegova homogenost korišten je mikroskop atomskih sila. Nakon provedenih eksperimenta optimizirani su parametri te je iz rezultata vidljivo da najbolju poželjnost modela s rezultatima daje obrada pomoću intenzivne pulsirajuće svjetlosti (IPL) pri uvjetima maksimalne energije od 2500 J i jednog bljeska. Pri obradi IPL-om sa pločicama podignutim od podloge dobije se idealna poželjnost od 100% dok se pri obradi bez izolacije od podloge dobije poželjnost od 90,1%. Najbolja poželjnost toplinske metode i modela, od 88,5%, očituje se pri minimalnoj temperaturi od 175 °C i vremenu zadržavanja od
79,61 minuta.In this study, a comparison of two processing methods of inkjet printed nanosilver ink on a glass substrate was performed. Thin films were subjected to the traditional method of heat treatment in the annealing furnace and a technology for creating intense pulsed light (IPL) was used for photothermal treatment. The Design-Expert program was used to propose the minimum number of experiments to establish the optimal temperature and processing time conditions for the thermal process, and energy and number of flashes for the photothermal process. The parameters that impact the quality and electrical conductivity of an
inkjet-printed nanosilver thin film on a glass substrate are also found. An atomic force microscope was used to determine the thickness of the printed material layer before and after processing and its homogeneity. After the experiments, the parameters were optimized, and the results show that the best fit between the model and the experimental results is when IPL is used to process it with 2500 J and one flash. The best result, with 100% fit, is obtained by IPL with 2 mm raised sample, while the best result by sample not raised from base surface is 90.1%. The best desirability of the thermal method and model is 88.5%, which is manifested at a minimum temperature of 175 °C and a duration of 79.61 minutes
Preparation and application of natural balm
No full textPojam balzam izvorno se odnosio na formulacije s ljekovitim učincima, a termin je doživio niz promjena tijekom stoljeća. Korišteni su od davnina za mumificiranje, a u hrvatskoj povijesti balzama ističu se Thierryev balzam i Melem. Balzami se upotrebljavaju u tehnici, medicini, farmaciji, parfumeriji, umjetnosti. U ovom radu opisani su odabrani najstariji balzami (peruanski balzam, jeruzalemski balzam, toluanski balzam, kanadski balzam i kopaiva balzam) te balzami često korišteni u današnje vrijeme (balzam za usne, balzam za bolove, balzam za opekline i rane, balzam protiv starenja, balzam ljekovitog matičnjaka i balzam za mrlje). Najčešće korištena vrsta balzama u svijetu je balzam za usne. U formulaciji balzama kao bazni sastojci često se koriste: ulja, masti i voskovi, a mogu sadržavati i razne dodatne sastojke poput macerata, ekstrakata, vitamina, hijaluronske kiseline, meda itd.
U eksperimentalnom dijelu rada napravljeno je šest balzama za sunčanje te šest balzama za masažu i smanjenje bolova. Razlikuju se prema korištenim sastojcima te njihovim udjelima. Svakom je balzamu određen pH, organoleptička svojstva (boja, miris i izgled) i napravljen test razmaza.The term balm originally referred to a formulations with medicinal effects, and the term has undergone several changes over the centuries. Balms have been used for mummification since ancient times, and in the Croatian history of balsams, Thierry's balsam and Melem stand out. Balms are used in technology, medicine, pharmacy, perfumery and art. This paper describes selected oldest balms (Peruvian balsam, Jerusalem balsam, Toluan balsam, Canadian balsam and Copaiva balsam) and balsams commonly used today (lip balm, pain balm, burn and wound balm, anti-ageing balm, lemon balm and skin blemish balm). The most commonly used type of balm in the world is lip balm. In the formulation of balms, the following ingredients are often used as a base ingredients: Oils, fats and waxes, and they may also contain various additional ingredients such as macerates, extracts, vitamins, hyaluronic acid, honey, etc. In the experimental part, six tanning balms and six balms for massage and pain relief were prepared. They differ in terms of the ingredients used and their proportions.
The pH and organoleptic properties (colour, odour and appearance) of each balm were determined, and a smear test was performed
Modeling of solubility of flavonoids in water and lower alcohols mixtures
No full textU ovom radu opisano je modeliranje topljivosti flavonoida (apigenin, daidzein, krizin, kvercetin, luteolin i naringenin) u smjesama vode i nižih alkohola (etanol i metanol). Izračunati su interakcijski parametri Wilsonova modela koeficijenta aktivnosti i modela NRTL iz eksperimentalnih podataka o topljivosti flavonoida u smjesama vode i nižih alkohola preuzetih iz literature. Grafički su opisana slaganja modela s eksperimentalnim rezultatima u
x-T-dijagramu. Raspravlja se o mogućnosti primjene pojedinog modela za ispitivane sustave.This paper describes modeling of solubility of flavonoids (apigenin, daidzein, chrysin, quercetin, luteolin and naringenin) in mixtures of water and lower alcohols (ethanol and methanol). The interaction parameters of the Wilson and NRTL activity coefficient models were calculated from the experimental data on the solubility of flavonoids in mixtures of water and lower alcohols taken from the literature. The agreement of the model with the experimental results is graphically described in the x-T-diagram. The possibility of applying a particular model for the examined systems is discussed
Litmus-based sensor films for use in microreactors
No full textCilj ovog rada bio je proizvesti senzorske filmove s lakmusom kao indikatorom i ispitati njihovo ponašanje. Korištenjem aditivne tehnologije ispisane su pločice i mikroreaktori različitih geometrija kanala od poli(vinil-butirala), termoplastičnog polimera povoljnih optičkih svojstava. pH-senzorski filmovi dobiveni su sol-gel metodom imobiliziranjem lakmus indikatora u silanskoj matrici. Korišteni prekursori za filmove bili su silicijevi alkoksidi tetraetoksisilan (TEOS) i feniltrimetoksisilan (FTMS). Metoda nanošenja filmova na površinu pločica i na stijenke kanala mikroreaktora bila je „drop coating“ metoda. Pločice i reaktori su zatim stavljeni na sušenje, te su na ovaj način dobiveni su optički kemijski senzori. Ispitivanja filma na pločicama pokazala su da senzorski film mijenja boju ovisno o pH medija u kojem se nalazi te je stabilan unutar vremena ispitivanja, dakle film se može nanositi na površinu kanala mikroreaktora. Promjena boje filma na stijenkama kanala mikroreaktora u otopinama različite pH-vrijednosti bilježi se kao vrijednost crvene, zelene i plave boje (engl. RGB – Red Green Blue). Za sve ispitivane reaktore uočava se porast vrijednosti za plavu boju s porastom pH-vrijednosti otopine. Boja se mijenja od crvene prema ljubičastoj s najvećom promjenom između pH 6 i 9, a promjena je reverzibilna. Dakle, ovakvi filmovi se mogu koristiti kao pH senzori u vodenim otopinama kiselina i lužina.The aim of this work was to produce sensor films using litmus as an indicator and to study their behavior. Using additive technology, plates and microreactors with different channel geometries were 3D printed from poly(vinylbutyral), a thermoplastic polymer with good optical properties. pH sensor films were made using the sol-gel method. The silicon alkoxides tetraethoxysilane (TEOS) and phenyltrimethoxysilane (FTMS) were used as precursors for the films. A litmus indicator was immobilized in the silane matrix. The films were applied to the surface of the plates and the channel of the microreactors using the "drop coating" method, and the reactors were then dried. Optical chemical sensors were fabricated in this manner. Tests of the film on the plates showed that the sensor film changes color depending on the pH of the solution and is stable within the test time, making the film suitable for use in microreactors. The color change of films on the wall of the microreactor tube in solutions with different pH values is recorded as red, green and blue color (RGB). For all reactors tested, an increase in the value for the blue color is observed with an increase in the pH of the solution. The color changes from red to purple, with the greatest change occurring between pH 6 and 9, and the change is reversible. Thus, these silane films can be used as pH sensors in aqueous solutions of acids and bases
Supercapacitors prepared from carbon nano-particles as active electrode materials
No full textSvrha ovog rada bila je pripraviti superkondenzatore od dva različita elektrodna materijala i testirati njihova elektrokemijska svojstva. Uspoređivane su dvije vrste aktivnih ugljika: Norit DLC SUPER 30 i NC (OVIA INOVACIJE). Sastavljena su dva superkondenzatora; jedan s elektrodama od Norita i drugi s elektrodama od NC-a. Superkondenzatori su testirani EIS-om, cikličkom voltametrijom i metodom punjenja/pražnjenja. EIS se provodila pri potencijalu 0 V u rasponu frekvencija od 10 mHz do 100 kHz. Ciklička voltametrija provodila se u dvoelektrodnom sustavu kroz tri ciklusa s brzinom promjene potencijala 20 mV s^-1, a raspon potencijala iznosio je od 0 V do 2 V. Galvanostatsko punjenje/pražnjenje provodilo se i u dvoelektrodnom i u troelektrodnom sustavu kroz 30 ciklusa uz stalnu struju od 20 mA. Na kraju su se opet ponovljeni EIS i ciklička voltametrija pod opisanim uvjetima. Materijali aktivnih ugljika okarakterizirani su FTIR analizom, DLS-om i termogravimetrijom. Rezultati dobiveni EIS-om prikazani su grafički Nyquistovim prikazom. Za NC otpori su gotovo jednaki prije i nakon rada superkondenzatora, dok se kod Norita značajno poveća otpor nakon 30 ciklusa punjenja i pražnjenja. Iz rezultata cikličke voltametrije primjećuje se da kod NC superkondenzatora nakon 30 ciklusa punjenja i pražnjenja dobivena struja postiže gotovo konstantnu vrijednost te bolje kapacitivne karakteristike. To znači da je kod NC superkondenzatora došlo do aktiviranja elektrodne površine i/ili porozne strukture materijala pa je i izmjena iona između pora unutar elektrode i otopine olakšana. To nije bio slučaj kod superkondenzatora s Norit ugljikom. Prema kapacitetima superkondenzatora, izračunatim iz krivulja punjenja i pražnjenja u dvoelektrodnom i troelektrodnom sustavu, može se zaključiti da NC ima veći kapacitet.The purpose of this work was to prepare supercapacitors from two different electrode materials and test their electrochemical properties. Two types of activated carbons were compared; Norit DLC SUPER 30 and NC. Two supercapacitors were assembled, one with Norit electrodes and the other with NC electrodes. The supercapacitors were tested by EIS, cyclic voltammetry and the charge/discharge method. EIS was performed at a potential of 0 V in the frequency range from 10 mHz to 100 kHz. Cyclic voltammetry was carried out in a two-electrode system through three cycles with a potential scan rate of 20 mV s^-1, and the potential range was from 0 V to 2 V. Galvanostatic charging/discharging was carried out both in a two-electrode and in a three-electrode system through 30 cycles with a constant current of 20 mA. At the end, EIS and cyclic voltammetry were repeated under the described conditions. Activated carbon materials were characterized by FTIR analysis, DLS and thermogravimetry. The results obtained by EIS are shown graphically using the Nyquist plot. For NC, the resistances are almost the same before and after the operation of the supercapacitor, while for Norit, the resistance increases significantly after 30 charging and discharging cycles. From the results of cyclic voltammetry, it can be observed that with NC supercapacitors, after 30 cycles of charging and discharging, the obtained current reaches an almost constant value and better capacitance characteristics. This means that with the NC supercapacitor, the electrode surface and/or the porous structure of the material has been activated, so the exchange of ions between the pores inside the electrode and the solution is facilitated. This was not the case with the Norit carbon supercapacitor. According to the supercapacitor capacitance, calculated from the charge and discharge curves in the two-electrode and three-electrode systems, it can be concluded that the NC has a higher capacitance
UV-VIS spectrophotometric analysis of a multicomponent mixture
No full textSpektrofotometrija u ultraljubičastom i vidljivom području jedna je od analitičkih tehnika koja ima široku primjenu u analitičkim laboratorijima za određivanje koncentracije analita u otopini uzorka. Metoda je jednostavna, jeftina, brza i ne zahtijeva dugotrajnu obuku analitičara. U ovom radu ispitana je mogućnost primjene UV-VIS spektrofotometrije za određivanje koncentracije metalnih iona (mangana, nikla, bakra i kobalta) u višekomponentnim smjesama. Pripremljene su pojedinačne otopine različitih koncentracija metalnih iona, kako i njihove smjese. Dobiveni rezultati mjerenja uspoređeni su s teorijskim koncentracijama pojedinih metalnih iona u višekomponentnim smjesama i izračunata je pogreška određivanja.Ultraviolet-visible spectrophotometry is widely used in analytical laboratories to determine the concentration of analytes in solution samples. The method is simple, cheap, fast and does not require long-term training of the analyst. In this work, the possibility of using UV-VIS spectrophotometry to determine the concentration of metal ions (manganese, nickel, copper and cobalt) in multicomponent mixtures was examined. Individual solutions of different concentrations of metal ions, as well as their mixtures, were prepared. The obtained measurement results were compared with the theoretical concentrations of individual metal ions in multicomponent mixtures and the determination error was calculated
Application of rGO/BiVO4 electrode for the photoelectrochemical degradation of amoxicillin
No full textCilj ovog rada bio je ispitati fotoelektrokemijski proces degradacije amoksicilina čija je koncentracija 0,1 mmol dm^-3. Mjerenja su se odvijala na elektrodi sa nanokompozitom koji se sastoji od fotokatalizatora BiVO4 čiji su slojevi naneseni na sloj reduciranog grafenovog oksida (rGO). Mjerenja su provedena za osvijetljene i neosvijetljene elektrode, za što nam je kao izvor služila LED lampa. Za karakterizacije pojedinih elektroda korištena je metoda linearne polarizacije prije i nakon fotoelektrokemijskog procesa, dok se za praćenje samog fotoelektrokemijskog procesa koristila metoda kronoamperometrije. Rezultati su pokazali kako u prisutnosti svjetla dolazi do pojave fotostruja što govori da je došlo do uspješnog stvaranja parova elektron-šupljina. Dobivena mjerenja su također pokazala da radikali nastali u fotoelektrokemijskom procesu oksidiraju rGO. Mjerenja provedena metodom kronoamperometrije ukazuju kako je fotostruja stabilnija pri pH = 6 nego pri pH = 4 iz čega se može zaključiti da se aktivnost elektrode značajnije smanjuje pri nižim pH vrijednostima. Praćenje koncentracije amoksicilina HPLC metodom pokazalo je kako s vremenom dolazi do degradacije amoksicilina. Iako su tijekom ispitivanja metodom linearne polarizacije dobivene veće fotostruje uz deblji sloj BiVO4 tijekom razgradnje farmaceutika nisu zabilježene značajne razlike u brzini razgradnje kod različitih BiVO4 slojeva.The goal of this work was to examine the photoelectrochemical degradation of amoxicillin, whose concentration is 0.1 mmol dm^-3. The measurements were carried out with an electron containing a BiVO4 photocatalyst. The layers of BiVO4 were applied over the reduced graphene oxide (rGO). Measurements were performed for illuminated and non-illuminated electrodes. LED lamp has been used as source of light. The linear polarisation method was used to characterize the electrodes before and after the photoelectrochemical process, while the chronoamperometry method has been used to follow the photoelectrochemical process. The results showed that photocurrent appears in the presence of light, which indicates that there was a successful formation of electron-hole pairs. Additionally, it is evident that radicals formed in the photoelectrochemical process oxidize rGO.The chronoamperometry method shows that the photocurrent is more stable at pH = 6 than at pH = 4 indicating that the activity of electrode decreases with pH decrease. Amoxycilline degradation in photoelectrochemical process was proved by HPLC method. Although linear polarisation shows that higher photocurrents were obtained for thicker layer of BiVO4, photoelectrochemical degradation does not show sigificant differences of pharmaceuticals degradation with different electrodes
Development and validation of a chromatographic method for the determination of residual solvents in production sludge
No full textOporaba je termin koji se često veže uz model kružnog gospodarstva pa tako tvrtka Premifab d.o.o. oporabljuje otpadna organska otapala različitih industrija s ciljem produljenja vrijednosti proizvoda. Oporaba se vrši šaržnom destilacijom nakon čega u destilatoru zaostaje mulj raznovrsnog kemijskog sastava koji ostaje neiskorišten i zbrinjava se o vlastitom trošku. S ciljem davanja vrijednosti proizvodnom mulju, potrebno je odrediti njegov kemijski sastav. Cilj ovog rada bio je razviti i validirati kromatografsku metodu za određivanje ostatnih organskih otapala u proizvodnom mulju koji nastaje šaržnom destilacijom otpadnih organskih otapala. Metoda je razvijana na plinskom kromatografu s FID detektorom i headspace uzorkovanjem. Nakon razvoja metode provedena je validacija kako bi se potvrdila prikladnost metode za njezinu namjenu. Rezultati validacije pokazali su da je metoda prikladna za određivanje metanola, etanola, acetona, izopropanola, metil-etil-ketona, etil-acetata, cikloheksana, izooktana i toluena u proizvodnom mulju. Za određivanje ostalih organskih otapala - metoksi-2-propanola, butanola, metil-izobutil-ketona, etoksi-2-propanola, butil-acetata, etilbenzena i izomera ksilena - potrebna je daljnja optimizacija metode. Nakon validacije, analiziran je realni uzorak proizvodnog mulja koji je dobiven destilacijom smjese otpadnih otapala metil-etil-ketona i etil-ace-tata porijeklom iz industrije proizvodnje fleksibilne ambalaže. Primjenom metode unutarnjeg standarda i relativnog faktora odgovora, kvantifikacija ispitivanog uzorka proizvodnog mulja uspješno je provedena.Recovery is a term that is often associated with the circular economy model. It is implemented in the company Premifab Ltd. that recovers waste organic solvents from various industries with the aim of prolonging product value. Recovery is carried out by batch distillation, after which distillation sludge of various chemical composition remains unused what leads to its disposal at company’s own expense. To give value to distillation sludge, it is necessary to determine its chemical composition. The aim of this work was to develop and validate a chromatographic method for the determination of residual organic solvents in distillation sludge obtained by batch distillation of waste organic solvents. The method was developed on a gas chromatograph with an FID detector and headspace sampling. After the method was developed, validation was performed to confirm the suitability of the method for its purpose. The validation results showed that the method is suitable for the determination of methanol, ethanol, acetone, isopropanol, methyl-ethyl-ketone, ethyl-acetate, cyclohexane, isooctane, and toluene in distillation sludge. For the determination of other organic solvents, methoxy-2-propanol, butanol, methyl-isobutyl-ketone, ethoxy-2-propanol, butyl-acetate, ethylbenzene and xylene isomers, further optimization of the method is required. After validation, a real sample of distillation sludge obtained by distilling a mixture of waste solvents methyl-ethyl-ketone and ethyl-acetate originating from the flexible packaging industry was analyzed. By applying the method of internal standard and relative response factor, quantification of the examined sample of production sludge was successfully performed