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Removal and degradation methods for perfluorinated compounds in water
No full textPerfluorirani spojevi (engl. perfluoroalkyl and polyfluoroalkyl substances - PFAS) antropogeni su organski spojevi koji se koriste kao sredstva za odbijanje vode, prljavština ili masti te kao zaštitni premazi i sprejevi. Zabrinutost oko perfluoriranih spojeva raste zbog njihove postojanosti, trajnosti, toksičnosti i otpornosti. Bioakumuliraju se u okolišu te su poznatiji pod nazivom „vječne kemikalije“. Naizgled korisni spojevi s vremenom pokazuju svoju negativnu stranu i postaju prijetnja za okoliš i organizme koji žive u njemu. Prisutni su u svim sastavnicama u okolišu pa se tako nalaze i u vodama. Pošto je voda ključan segment bez koje život nije moguć, važna je njezina kakvoća. Iz tog razloga potreba za uklanjanjem perfluoriranih spojeva iz voda raste te su uvedene metode obrade otpadnih voda koje se cijelo vrijeme razvijaju kako bi se unaprijedila njihova učinkovitost. Metode obrade otpadnih voda dijele se na konvencionalne, biološke i napredne metode pri čemu se napredne koriste za obradu voda od perfluoriranih spojeva zbog neučinkovitosti konvencionalnih i bioloških metoda. Cilj ovog rada je dati uvid u napredne metode obrade otpadnih voda od PFAS-a. Pritom će detaljnije biti pojašnjeni fotokemijski i fotokatalitički procesi, elektrokemijski oksidacijski procesi i ozonacija. U ovom radu prikazana je učinkovitost konvencionalnih, bioloških i naprednih metoda. Konvencionalne mogu postići djelomično uklanjanje
(67 % - 75 %), biološke postižu razgradnju od najviše 45 %, a napredne su sposobne za vrlo visok stupanj razgradnje (> 99 % fotokatalizom i ozonacijom) te postoji i mogućnost mineralizacije PFAS-a elektrokemijskom oksidacijom.Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are anthropogenic organic compounds that are used as water, dirt or grease repellants and as protective coatings and sprays. Concerns about perfluorinated compounds are growing due to their persistence, durability, toxicity and resistance. They bioaccumulate in the environment and are also known as "forever chemicals". Seemingly useful compounds show their negative side over time and become a threat to the environment and the organisms that live in it. They are present in all components in the environment, they are also found in water. Since water is a key segment without which life is not possible, its quality is important. For this reason, the need to remove perfluorinated compounds from water is growing, and wastewater treatment methods that have been introduced that are constantly being developed in order to improve their efficiency. Wastewater treatment methods are divided into conventional, biological and advanced methods, whereby advanced methods are used to treat water from perfluorinated compounds due to the inefficiency of conventional and biological methods. The aim of this paper is to provide an insight into advanced methods of wastewater treatment from PFAS. Photochemical and photocatalytic processes, electrochemical oxidation processes and ozonation will be explained in more detail. This paper shows the effectiveness of conventional, biological and advanced methods. Conventional ones can achieve partial removal (67 % - 75 %), biological ones achieve a maximum of 45 % decomposition, and advanced ones are capable of a very high degree of decomposition (> 99 % by photocatalysis and ozonation) and there is also the possibility of PFAS mineralization
by electrochemical oxidation
Calculation of heating value of fuel derived from waste
No full textS porastom svjetske populacije dolazi do porasta količine nastalog otpada. Stoga se javlja globalni problem zbrinjavanja otpada. Uz zakone o izdvajanju materijala za recikliranje iz otpada, mnogobrojna reciklažna dvorišta i razne usluge prikupljanja otpada i dalje postoji problem sa odlaganjem i zbrinjavanjem miješanog komunalnog otpada. Jedno od mogućih rješenja je proizvodnja goriva iz otpada, GIO. Prema podacima iz 2018. godine, u svijetu postoji oko 1180 postrojenja za energetsku oporabu otpada. Gorivo iz otpada obuhvaća sav otpad koji se koristi u energetske svrhe, no bez standardizacije i klasifikacije takvo gorivo ne predstavlja pouzdan izvor energije. Stoga je razvijen sustav standarada koji precizno definiraju goriva iz otpada. Tako definirana goriva nazivaju se SRF (engl. Solid Recovered Fuel). Standardizacija zahtjeva poznavanje donje toplinske vrijednosti goriva ( Hd ), te udio opasnih elemenata poput klora i žive. Na temelju tih vrijednosti izrađene su klase goriva. Uspostavom ovakve standardizacije omogućen je razvoj novih tehnologija energetske oporabe otpada, što dovodi do smanjenja volumena otpada na odlagalištima i smanjenju utjecaja na okoliš.As the global population increases, the amount of generated waste also rises, leading to a significant global waste management problem. Despite regulations on the separation of recyclable materials, numerous recycling facilities, and various waste collection services,
the issue of disposing of mixed municipal waste persists. One potential solution is the production of Refuse Derived Fuel (RDF). According to 2018 data, there are approximately 1,180 waste-to-energy facilities worldwide. Refuse Derived Fuel encompasses all waste used for energy purposes; however, without proper standardization and classification, such fuel does not provide a reliable energy source. Consequently, a system of standards has been developed to precisely define waste-derived fuels. These standardized fuels are known as Solid Recovered Fuel (SRF). The standardization process requires knowledge of the lower heating value (LHV) of the fuel, as well as the concentration of hazardous elements such as chlorine and mercury. Based on these parameters, fuel classes have been established.
The implementation of such standardization has enabled the development of new waste-to-energy technologies, leading to a reduction in the volume of waste disposed of in landfills and a decrease in environmental impact
Isolation and purification of hydrogenase from Ralstonia eutropha H16
No full textJedan od ključnih enzima u enzimatskoj proizvodnji biovodika je enzim hidrogenaza.
U organizmima kao što su bakterije, alge i biljke mogu se pronaći različite vrste hidrogenaza, pri čemu su najzastupljenije [FeFe]-hidrogenaze i [NiFe]-hidrogenaze. U stanicama bakterije Ralstonia eutropha H16 prisutne su tri različite [NiFe]-hidrogenaze tolerantne na kisik uključene u transport H2 što ovu bakteriju čini izvrsnim izvorom hidrogenaza.
Cilj ovog istraživanja bio je heterotrofno uzgojiti stanice R. eutropha H16 na četiri različite sintetske podloge. Tijekom uzgoja praćene su promjene koncentracije biomase i supstrata,
a najbolji rast stanica zabilježen je na sintetskoj podlozi koja je sadržavala 4 g/L fruktoze. Nakon uzgoja stanica, provedena je optimizacija ultrazvučnog razbijanja stanica korištenjem Box-Behnken dizajna eksperimenta s tri varijable (amplituda ultrazvuka, koncentracija stanica i vrijeme razbijanja) na tri razine s ciljem oslobađanja što veće koncentracije proteina.
Kada je proces proveden pri optimalnim procesnim uvjetima (amplituda ultrazvuka 40 %, vrijeme razbijanja 25 min i koncentracija stanica 3 mg/mL) dobivena maksimalna koncentracija proteina u uzorku iznosila je 2,483 ± 0,110 mg/mL.One of the key enzymes in the enzymatic production of biohydrogen is the enzyme hydrogenase. Various types of hydrogenases are found in organisms such as bacteria, algae and plants, with [FeFe]-hydrogenases and [NiFe]-hydrogenases being the most abundant. In the cells of the bacterium Ralstonia eutropha H16, there are three different oxygen-tolerant [NiFe]-hydrogenases involved in H2 transport, which makes this bacterium an excellent source of hydrogenases. The aim of this research was to heterotrophically grow R. eutropha H16 cells on four different synthetic substrates. During cultivation, changes in the concentration of biomass and substrate were monitored, and the best cell growth was recorded on a synthetic medium containing 4 g/L fructose. After cell cultivation, optimization of ultrasonic cell disruption (ultrasound amplitude, cell concentration and disruption time) was performed using a three-level experimental Box-Behnken design with three variables with the aim of releasing the highest possible protein concentration. When the process was carried out under optimal process conditions (ultrasound amplitude 40%, disruption time 25 min and cell concentration 3 mg/mL), the maximum protein concentration obtained in the sample was 2.483 ± 0.110 mg/mL
Rheological and thermal properties of PEG/nano-SiO2 composites
No full textPolimerni materijali imaju ključnu ulogu u modernom društvu, s primjenom koja je duboko ukorijenjena u različite grane industrije. Kako se društvo razvija tako raste i potreba za unaprijeđenjem svojstava ovih materijala. U posljednjih nekoliko desetljeća, naglasak je stavljen na primjenu nanočestica kao punila u polimernim matricama, tvoreći tako polimerne nanokompozite. Kod ovakvih materijala, vrlo male količine punila uzrokuju značajna poboljšanja svojstava dok se procesi proizvodnje i obrade održavaju na visokom nivou. Ipak, razvoj polimernih nanokompozita sa sobom nosi i brojne izazove. Međutim, zbog velikog interesa znanstvenika i inženjera u ovom području, zagarantiran je ubrzani napredak u godinama koje slijede. U ovom radu pripravljeni su polimerni nanokompoziti PEG/nano-SiO2 različitog sastava, zamješavanjem PEG400 i PEG12000 s 0,1; 0,3; 0,5 i 1,0% nano-SiO2 na magnetskoj miješalici. Cilj je bio utvrditi utjecaj dodatka nanočestica SiO2 na reološka i toplinska svojstva PEG-a te na međupovršinske interakcije polimerne matrice i nanopunila.
U tu svrhu provedena su reološka ispitivanja pripremljenih nanokompozita, diferencijalna pretražna kalorimetrija (DSC), termogravimetrijska analiza (TGA) te mjerenje kontaktnog kuta. Svojstva međupovršine polimerne matrice i nanopunila određena su preko izračunatih parametara adhezije.Polymeric materials play a vital role in modern society, with applications deeply embedded in various industries. As society evolves, so does the need to enhance the properties of these materials. In recent decades, the focus has shifted towards the use of nanoparticles as fillers in polymer matrices, leading to the development of polymer nanocomposites. In these materials, even small amounts of fillers result in significant improvements in properties, while maintaining high standards of production and processing. However, the development of polymer nanocomposites presents numerous challenges. Nonetheless, the strong interest from scientists and engineers in this field ensures accelerated progress in the years to come. In this study, polymer nanocomposites of PEG/nano-SiO2 with varying compositions were prepared by mixing PEG400 and PEG12000 with 0,1; 0.3; 0,5 and 1,0% nano-SiO2 using a magnetic stirrer. The goal was to examine how adding SiO2 nanoparticles affects the rheological and thermal properties of PEG, and to assess the interfacial interactions between the polymer matrix and the nanoparticles. To achieve this, rheological testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and contact angle measurements were performed. The properties of the interphase between the polymer matrix and the nanoparticles were determined through calculated adhesion parameters
Assisted extraction of biflavonoids from the Ginkgo biloba L. leaves
No full textBiljke proizvode strukturno raznovrsne specijalizirane metabolite, koji su se razvili u različitim biljnim vrstama i predstavljaju prilagodbu specifičnim ekološkim situacijama. Flavonoidni dimeri, poznatiji pod nazivom biflavonoidi, sastoje se od dva identična ili različita flavonoidna monomera. U odnosu na monomere, manje su istraženi i pokazuju različitu biološku aktivnost, a u zadnje vrijeme je prepoznat njihov farmakološki potencijal. Kako bi se biflavonoidi mogli koristiti kao antibakterijsko, protuupalno, antialergijsko, antimutageno, antiviralno, ili antikarcenogeno sredstvo, potrebno ih je izolirati iz prirodnih izvora. U ovom radu istražene su različite metode ekstrakcije biflavonoida iz listova ginka, uključujući konvencionalnu ekstrakciju sa 70% etanolom, te ekstrakciju sa 70% etanolom potpomognutu ultrazvukom, mehanički, enzimski (smjesa lignocelulitičkih enzima: celulaza, lakaza, ksilanaza) i kemijski. Morfološka analiza praha prije i nakon ekstrakcije provedena je pomoću skenirajućeg elektronskog mikroskopa (SEM). Ukupan sadržaj polifenola, fenolnih kiselina i flavonoida određen je spektrofotometrijski u ekstraktima, a biflavonoidi su identificirani i kvantificirani HPLC-DAD analizom. Rezultati istraživanja biflavonoida ukazali su kako se unutar prvih 5 minuta ekstrakcija vidi značajna razlika između različitih metoda ekstrakcije. Svaka potpomognuta ekstrakcija rezultirala je povećanjem učinkovitosti ekstrakcije biflavonoida, pri čemu je korištenjem enzimske potpomognute ekstrakcije zabilježeno i 50% povećanje koncentracije biflavonida u ekstraktima u odnosu na ekstrakciju provedenu samo sa 70% etanolom. Kada je ekstrakcija provedena u vremenu od 45 min, najbolji rezultati ekstrakcije biflavonoida dobiveni su korištenjem 70% etanola potpomognutog ultrazvukom i enzimom.Plants produce various specialized metabolites that have evolved in different species due to adaptation to specific ecological conditions. Flavonoid dimers or biflavonoids consist of two identical or different flavonoid monomers. These compounds are less researched than the monomers and have different biological activities, although their pharmacological potential has recently been increasingly recognized. In order for biflavonoids to be used as antibacterial, anti-inflammatory, antiallergic, antimutagenic, antiviral or anticarcinogenic agents, it is necessary to isolate them from natural sources. In this study, different methods for the extraction of biflavonoids from ginkgo leaves were investigated, including conventional extraction in 70% ethanol, ultrasound-assisted (UAE + 70% ethanol), mechanically assisted (MAE + 70% ethanol), chemically assisted (CAE + 70% ethanol) and enzyme-assisted extraction (EAE + 70% ethanol) using a mixture of lignocellulolytic enzymes (cellulase, laccase, xylanase). Morphological analysis of the powder before and after extraction was performed using a scanning electron microscope (SEM). The total content of polyphenols, phenolic acids and flavonoids in the extracts was determined spectrophotometrically, while the biflavonoids were identified and quantified by HPLC-DAD analysis. The study showed significant differences in extraction efficiency within the first 5 minutes between the different methods. Assisted extraction techniques significantly increased the efficiency of biflavonoid extraction, with enzyme-assisted extraction yielding a 50% increase in biflavonoid concentration compared to extraction with 70% ethanol alone. The most effective results were obtained with the UAE + 70% ethanol and EAE + 70% ethanol methods when the extraction was performed for 45 minutes
A review of composites and blends-based on polyhydroxyalkanoates
No full textPolihidroksialkanoati (PHA) su poliesteri koji privlače veliku pažnju zbog svoje biorazgradivosti i biokompatibilnosti, što ih čini vrlo primjenjivima u različitim industrijama. Kako bi se poboljšala svojstva i smanjili troškovi proizvodnje, intenzivno se razvijaju kompoziti i mješavine na bazi PHA. PHA se mogu kombinirati s raznim polimerima, aditivima i punilima kako bi se postigla šira paleta svojstava i funkcionalnosti. Razvoj ovih materijala proširuje primjenu PHA te promiče održivost i ekološku svijest u društvu. U ovom preglednom radu razmatrane su mješavine PHA s polimerima poput polilaktidne kiseline (PLA), polikaprolaktona (PCL), polibutilen sukcinata (PBS) i poliamida (PA), koje omogućuju prilagodbu mehaničkih i termičkih svojstava prema specifičnim zahtjevima primjene. Pored toga, istraženi su kompoziti PHA s različitim punilima, uključujući škrob, kitozan, celulozu i drvo, kako bi se poboljšala čvrstoća, elastičnost i smanjili troškovi konačnih materijala. Rad naglašava važnost daljnjih istraživanja u razvoju i optimizaciji ovih materijala, kako bi PHA postao široko primjenjiv u industrijama koje zahtijevaju održive i ekološki prihvatljive opcije.Polyhydroxyalkanoates (PHA) are polyesters that have attracted a lot of attention due to their biodegradability and biocompatibility, making them highly applicable in various industries. In order to improve properties and reduce production costs, PHA-based composites and blends are being intensively developed. PHAs can be combined with various polymers, additives and fillers to achieve a wider range of properties and functionalities. The development of these materials expands the application possibilities of PHA and promotes sustainability and environmental awareness in society. In this review, blends of PHA with polymers such as polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS) and polyamide (PA) were considered, which allow tailoring of mechanical and thermal properties to specific application requirements. In addition, PHA composites with various fillers, including starch, chitosan, cellulose and wood, were investigated to improve the strength and elasticity and reduce the cost of the end products. The paper highlights the importance of further research to develop and optimise these materials so that PHA can be widely used in industries that require sustainable and environmentally friendly options
A review on agro-industrial waste (AIW) derived adsorbents for water and wastewater treatment
No full textRazvoj industrije ima ozbiljan utjecaj na okoliš i vodene resurse zbog uporabe raznih anorganskih i organskih onečišćujućih tvari. Boje i toksični metali koriste se u mnogim industrijskim granama te su prisutni u otpadnim vodama. Jedna od najčešće korištenih metoda za pročišćavanje otpadnih voda je adsorpcija koja je jednostavna, ekonomski pouzdana i proizvodi male količine otpada. Visoka cijena adsorbensa veliki je nedostatak ove metode koji se može smanjiti ukoliko se adsorbens priprema od otpadnih materijala poljoprivredne industrije. Agroindustrijski otpad odnosi se na nusproizvode koji nastaju tijekom industrijske prerade poljoprivrednih sirovina, dakle odnosi se na ostatke nakon obrade biljaka i životinja u industrijske proizvode. Sav biljni otpad sastoji se od hemiceluloze, celuloze i lignina te ima širok raspon funkcionalnih skupina koje reagiraju sa onečišćujućim tvarima različitim mehanizmima. Taj se otpad najčešće modificira kako bi se povećala njegova učinkovitost kao adsorbensa. Metodom cijepljenja uvode se dodatne funkcionalne skupine na površinu adsorbensa, a procesom karbonizacije povećava se sadržaj ugljika čime se djeluje na veličinu pora. Najčešće metode aktivacije kojima se modificiraju adsorbensi su modifikacije kiselinama, bazama, ultrazvukom, mikrovalnim zračenjem i magnetom. U ovom će radu biti dan pregled adsorbensa dobivenih od agroindustrijskog otpada, načini na koji su modificirani te na koji se način zbrinjavaju nakon procesa adsorpcije.The development of industry has a significant impact on the environment and water resources due to the use of various inorganic and organic pollutants. Dyes and toxic metals are used in many industrial sectors and are present in wastewater. One of the most commonly used methods for wastewater treatment is adsorption, which is simple, economically reliable, and produces small amounts of waste. The high cost of adsorbents is a major drawback of this method, which can be reduced if the adsorbent is prepared from agricultural industry waste. Agro-industrial waste refers to by-products generated during the industrial processing of agricultural raw materials, including residues from the processing of plants and animals into industrial products. All plant waste consists of hemicellulose, cellulose, and lignin and has a wide range of functional groups that react with pollutants through various mechanisms. This waste is often modified to increase its efficiency as an adsorbent. The grafting method introduces additional functional groups on the adsorbent's surface, while the carbonization process increases the carbon content, affecting pore size. The most common activation methods used to modify adsorbents include modifications with acids, bases, ultrasound, microwave radiation, and magnets. This paper will provide an overview of adsorbents derived from agro-industrial waste, the ways in which they have been modified, and how they are disposed of after the adsorption process
Spherical crystallization scale-up
No full textSferična kristalizacija metoda je kristalizacije koja rezultira izravnim nastankom sferičnih kristala poboljšanih fizikalno – kemijskih svojstava čime se olakšava proces proizvodnje lijekova. U ovome radu provedena je sferična kristalizacija djelatne tvari ceritiniba. Kristalizacija je provedena kombinacijom metoda sferične aglomeracije i kvazi – emulzijske difuzije otapala za sustav otapala u kojemu je kao dobro otapalo korišten tetrahidrofuran, kao kapljevina za premoštenje heptan te kao loše otapalo voda uz dodatak
poli(vinil – pirolidon) – a (1 % w/w). Proces kristalizacije proveden je i optimiziran u manjem kristalizatoru te su usporedbom oblika i veličina dobivenih kristala odabrani omjeri otapala za uvećanje procesa. Kao kriterij uvećanja primijenjena je kritična brzina miješanja. Minimalna brzina miješanja za postizanje stanja potpune disperzije određena je vizualno u sustavu heptan – voda, dok je minimalna brzina vrtnje miješala potrebna za postizanje stanja potpune suspenzije određena pomoću Zwieteringovog izraza. Granulometrijska svojstva kristala karakterizirana su svjetlosnim mikroskopom i čestičnim analizatorom. Usporedbom dobivenih kristala zaključuje se kako udio kapljevine za premoštenje i brzina miješanja imaju značajan utjecaj na veličinu kristala. Bolji rezultati dobiveni su pri vizualno određenoj kritičnoj brzini miješanja. Rendgenskom difrakcijskom analizom utvrđeno je kako prisutnost dodatka i kapljevine za premoštenje ne utječe na unutarnju strukturu ceritiniba.Spherical crystallization is a method of crystallization that results in the direct formation of spherical crystals with improved physical and chemical properties, thus facilitating the process of drug production. In this paper, spherical crystallization of the active pharmaceutical ingredient ceritinib was carried out. Crystallization was carried out by a combination of spherical agglomeration and quasi – emulsion solvent diffusion methods for a solvent system in which tetrahydrofuran was used as a good solvent, heptane as a bridging liquid, and water as a poor solvent with the addition of poly – (vinyl – pyrrolidone) (1 % w/w). The crystallization process was carried out and optimized in a smaller crystallizer, and by comparing the shapes and sizes of the obtained crystals, solvent ratios were selected to scale – up the process. The critical impeller speed was applied as the scale – up criteria. The minimum impeller speed to achieve the complete dispersion was determined visually in the heptane – water system, while the minimum impeller speed required to achieve the complete suspension was determined using the Zwietering correlation. The granulometric properties of the crystals were characterized by a light microscope and a particle analyzer. By comparing the obtained crystals, it is concluded that the proportion of bridging liquid and the impeller speed have a significant influence on the size of crystals. Better results were obtained at the visually determined impeller speed. X – ray diffraction analysis determined that the presence of additives and bridging liquid does not affect the structure of ceritinib
Voltammetric determination of azithromycin on printed electrodes
No full textAzitromicin je antibiotik koji se svrstava u podskupinu azalida te je vrlo zastupljen u medicini pri tretiranju brojnih infekcija. Njegovo određivanje predstavlja važnu ulogu kod određivanja kakvoće otpadnih voda te voda za piće. U brojnim metodama detekcije se posebno ističu elektrokemijske metode i to ciklička voltametrija (CV), diferencijalna pulsna voltametrija (DPV) te kronoamperometrija. Modificiranjem senzora koji se koriste kod ovih metoda dolazi se do poboljšanja karakteristika kao što su specifična površina, brzina prijenosa elektrona te selektivnost što za posljedicu ima uspješnije određivanje azitromicina u uzorcima. U novije vrijeme se često koriste tiskani elektrokemijski senzori, a kao metode obrade termalna i obrada intenzivnom pulsirajućom svjetlosti (IPL). U radu je provedena elektrokemijska i analitička karakterizacija komercijalnih sitotiskanih grafenskih i ugljičnih te inkjet ispisanih grafenskih senzora koji su obrađeni termalno i IPL-om. Analizom cikličkih voltamograma određeni su kinetički parametri, dok su pomoću DPV-ova određeni baždarni pravci za pojedine elektrode te je za inkjet ispisani senzor obrađen IPL-om provedeno i kronoamperometrijsko mjerenje. DPV-om je ispitana i selektivnost IPL obrađenog senzora. Rezultati su pokazali kako grafenski SPE ima najveću konstantu brzine izmjene elektron (0,1261 cm/s), a nakon njega slijedi IPL IPE (0,0377 cm/s). Najveću akivnu površinu je imao termalno obrađeni IPE te ona iznosi 0,088 cm². Dobru osjetljivost su pokazali ugljični SPE (analiza DPV-om) i IPL IPE (analiza DPV-om i kronoamperometrijski u protoku). Ispitivanje specifičnosti koristeći DPV za IPL IPE pokazalo je kako mokraćna i askorbinska kiselina utječu na promjenu odziva.Azithromycin is an antibiotic that belongs to the subclass of azalides and is widely used in medicine to treat numerous infections. Its determination plays a very important role in assessing the quality of wastewater and drinking water. Electrochemical methods, particularly cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry, are highlighted in many detection methods. By modifying the sensors used in these methods, improvements in characteristics such as specific surface area, electron transfer rate, and selectivity are achieved, resulting in more successful determination of azithromycin in samples. Recently, printed electrochemical sensors have been commonly used, along with thermal and intense pulsed light (IPL) processing methods. In this study, electrochemical and analytical characterization of commercial screen-printed graphene and carbon sensors, as well as inkjet-printed graphene sensors that were thermally and IPL treated, was carried out. Kinetic parameters were determined by analyzing cyclic voltammograms, while calibration curves for individual electrodes were determined using DPV, and chronoamperometric measurement was performed for the IPL-treated inkjet-printed sensor. DPV was also used to test the selectivity of the IPL-treated sensor. The results showed that the graphene SPE had the highest electron exchange rate constant (0.1261 cm/s), followed by IPL IPE
(0.0377 cm/s). The largest active surface area was observed in the thermally treated IPE, totalling to 0.088 cm². Good sensitivity was demonstrated by carbon SPE (DPV analysis) and IPL IPE (DPV analysis and chronoamperometric flow analysis). The specificity testing using DPV for IPL IPE showed that uric and ascorbic acid influenced the sensor's response
Discrete random variables and applications
No full textOvaj završni rad bavi se tematikom diskretnih slučajnih varijabli te njihovom primjenom u statistici i inženjerstvu. U prvom dijelu završnog rada definiramo diskretne slučajne varijable i njihove osnovne karakteristike kao što su funkcija gustoće vjerojatnosti, funkcija distribucije vjerojatnosti, očekivana vrijednost, varijanca i standardna devijacija. U drugom dijelu rada analiziramo nekoliko važnih distribucija, uključujući Bernoullijevu, binomnu, Poissonovu, negativnu binomnu, geometrijsku te hipergeometrijsku distribuciju. Svaka distribucija prikazana je različitim primjerima i grafičkim prikazima.
Rad omogućuje bolje shvaćanje i razumijevanje diskretnih slučajnih varijabli, te njihovo korištenje.This final thesis deals with the topic of discrete random variables and their application in statistics and engineering. In the first part of the thesis, we define discrete random variables and their fundamental characteristics such as probability density function, probability distribution function, expected value, variance and standard deviation. In the second part of the thesis, we analyze several important distributions, including Bernoulli, binomial, Poisson, negative binomial, geometric and hypergeometric distribution. Each distribution is illustrated with various examples and graphical representations.
The thesis aims to provide a better understanding of discrete random variables, and their use