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The influence of eutectic solvents as plasticizers on the properties of TPS/cellulose blends
No full textU današnjem svijetu, problem prekomjernog onečišćenja okoliša plastikom potiče istraživače i industriju da traže alternative tradicionalnim plastikama. U tom kontekstu, ovaj rad istražuje utjecaj eutektičkih otapala kao plastifikatora na svojstva termoplastičnih škrobnih (TPS) i celuloznih mješavina. Fokusiranje na biorazgradive polimere poput škroba i celuloze pruža perspektivu održivih rješenja za problem prekomjerne uporabe plastike. U prvom dijelu rada detaljno se razmatraju vrste polimera, s posebnim naglaskom na polimerne mješavine i biorazgradive polimere. Škrob i celuloza, kao predstavnici obnovljivih resursa, analiziraju se zbog svojih ekoloških prednosti i mogućnosti prilagodbe kroz modifikacije poput termoplastičnog škroba. Nadalje, istražene su metode karakterizacije polimernih mješavina, uključujući termogravimetrijsku analizu (TGA), diferencijalnu pretražnu kalorimetriju (DSC), mjerenje propusnosti vodene pare, kontaktni kut i mehanička svojstva mješavina. Eutektička otapala, koja su mješavine dvaju ili više komponenti s nižom točkom taljenja od pojedinačnih komponenti, predstavljaju inovativan pristup u poboljšanju svojstava biorazgradivih polimera. Njihova uloga kao plastifikatora može značajno utjecati na poboljšanje mehaničkih svojstava, povećanje hidrofobnosti te smanjenje propusnosti vodene pare u polimernim mješavinama. Eksperimentalni dio rada obuhvaća pripremu uzoraka, provođenje različitih metoda karakterizacije te analizu dobivenih rezultata. Ovaj rad doprinosi razumijevanju kako upotreba eutektičkih otapala može unaprijediti svojstva biorazgradivih polimernih materijala. Razvijeni materijali s poboljšanim karakteristikama predstavljaju korak naprijed prema smanjenju ekološkog utjecaja plastike, nudeći održiva rješenja za budućnost. Nastavak istraživanja u ovom području mogao bi dodatno optimizirati procese i formulacije, što bi omogućilo širu primjenu biorazgradivih polimera u svakodnevnom životu.In today's world, the problem of excessive environmental pollution caused by plastics is driving researchers and industry to seek alternatives to traditional plastics. In this context, this paper explores the impact of eutectic solvents as plasticizers on the properties of thermoplastic starch (TPS) and cellulose blends. Focusing on biodegradable polymers such as starch and cellulose provides sustainable perspectives to address the issue of plastic overuse. The first part of the paper extensively discusses polymer types, with a special emphasis on polymer blends and biodegradable polymers. Starch and cellulose, as representatives of renewable resources, are analyzed for their ecological advantages and adaptability through modifications such as thermoplastic starch. Additionally, methods for characterizing polymer blends are examined, such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), water vapor permeability, contact angle measurements, and mechanical properties assessment of the blends. Eutectic solvents, which are mixtures of two or more components with a lower melting point than individual components, present an innovative approach to enhancing the properties of biodegradable polymers. Their role as plasticizers can significantly improve mechanical properties, increase hydrophobicity, and reduce water vapor permeability in polymer blends. The experimental section covers sample preparation, various characterization methods, and analysis of the obtained results. This paper contributes to understanding how the use of eutectic solvents can enhance the properties of biodegradable polymer materials. Developed materials with improved characteristics represent a step forward in reducing the ecological impact of plastics, offering sustainable solutions for the future. Further research in this area could optimize processes and formulations, enabling broader application of biodegradable polymers in everyday life
A comparison of seed layer preparing routes for growth of nanostructured ZnO thin films
No full textNanotehnologija ima izuzetno svijetlu budućnost jer nudi precizno oblikovanje materijala na najfinijoj razini. Nanostrukture cinkova oksida (ZnO) su od velike važnosti zbog jedinstvenih kemijskih, električkih i optičkih svojstava. Svoju primjenu pronalaze u brojnim naprednim tehnologijama, a istraživanja nanostruktura cinkova oksida su usmjerena na optimizaciju metoda sinteze kako bi se u potpunosti iskoristio njihov potencijal. Cilj rada bio je usporediti dva pristupa priprave predložaka za rast tankih filmova nanostrukturiranoga ZnO.
Za pripravu početnih slojeva upotrijebile su se metoda ablacije iskrom i metoda oblaganja rotiranjem, dok se za daljni rast nanoštapića na svim uzorcima upotrijebila kemijska metoda taloženja iz otopine. Nakon sinteze, uzorci su karakterizirani pomoću rendgenske difrakcijske analize (engl. X-ray diffraction, XRD) i mikroskopije atomskih sila (engl. Atomic force microscopy, AFM).Nanotechnology holds a remarkably bright future, offering the ability to precisely manipulate materials at the finest scale. Zinc oxide (ZnO) nanostructures are of great importance due to their unique chemical, electrical, and optical properties. These nanostructures are utilized in a wide range of advanced technologies, while research on zinc oxide nanostructures aims to optimize synthesis methods to maximize their potential. The aim of the study was to compare two approaches to preparing templates for the growth of thin films of nanostructured ZnO. Seedlayers were prepared using the spark ablation method and the spin coating method, while the chemical bath deposition method was used for the subsequent growth of nanorods on all samples. After synthesis, the samples were characterized using X-ray diffraction (XRD) analysis and atomic force microscopy (AFM)
Study of bronze corrosion protection by nanocoatings on rotating disc electrode
No full textCilj ovog rada bio je ispitati utjecaj hidrodinamike, odnosno brzine vrtnje disk elektrode na korozijsko ponašanje bronce zaštićene nanoprevlakama umrežene i neumrežene behenske kiseline. Behenska ili dokosanoinska kiselina je zasićena masna kiselina strukturne formule HOOC(CH2)20CH3. Uranjanjem metala u otopinu behenske kiseline nastaje samoorganizirajući monosloj visokog stupnja uređenosti koji pruža zaštitu površini metala. Izlaganjem formiranog sloja kiseline ionizirajućem zračenju, dolazi do umrežavanja molekula i nastaje kompaktniji sloj poboljšanih zaštitnih svojstava. Ispitivano je korozijsko ponašanje uzoraka čiste bronce, bronce sa slojem behenske kiseline i bronce s umreženim slojem behenske kiseline u otopini koja simulira kiselu kišu u stacionarnom stanju i pri različitim brzinama vrtnje disk elektrode. Zaštitna svojstva stvorenih nanoprevlaka ispitana su metodama linearne polarizacije i elektrokemijske impedancijske spektroskopije. Dobiveni rezultati pokazuju da neumreženi filmovi behenske kiseline dobiveni samo uranjanjem, kao i oni koji su umreženi ionizirajućim zračenjem, pružaju korozijsku zaštitu bronci izloženoj otopini kisele kiše. Zaštita je postignuta pri svim ispitivanim brzinama rotacije disk elektrode. Najbolja zaštita postignuta je s filmovima behenske kiseline dobivenih samo uranjanjem (bronca s kiselinom), osim u slučaju najveće brzine rotacije gdje bolju zaštitu pokazuju uzorci s umreženim slojem kiseline.The aim of this work was to examine the influence of hydrodinamics, i.e., the speed of rotation of the disk electrode on corrosion behavior of bronze protected by noncrosslinked and crosslinked behenic acid nanocoatings. Behenic or docosanoic acid is a saturated fatty acid with the structural formula HOOC(CH2)20CH3. Protective films of behenic acid can be formed on metal surface by immersion of metal in behenic acid solution. By exposing the formed acid film to ionization radiation, its cross-linking can be induced, resulting in the formation of a more compact protective film. The corrosion behavior of samples of pure bronze, bronze with a layer of behenic acid and bronze with a cross-linked layer of behenic acid in an artificial solution of acid rain in a stationary state and at different speeds of rotation of the disk electrode were tested. The protective properties of the nanocoatings was tested using the linear polarization method and electrochemical impedance spectroscopy. The results obtained show that films of behenic acid obtained only by immersion as well as those that are cross-linked provide corrosion protection to bronze exposed to the acid rain solution. Protection was observed at all tested rotation speeds of the disk electrode.
The best protection was achieved with films of behenic acid obtained only by immersion (bronze with acid), except in the case of the highest rotation speed where better protection is shown by samples with a cross-linked layer of behenic acid
Arsenic removal technologies and future development trends
No full textU ovom radu biti će dan pregled tehnologija uklanjanja arsena i budućih trendova razvoja. Nove održive tehnologije daju naglasak na fitoremedijaciju i nano materijale kako bi se riješilo i smanjilo onečišćenje pitke i otpadne vode u zemljama sa visokim koncentracijama arsena. Fitoremedijacija koristi biljke za čišćenje onečišćenih voda od arsena, dok nano fitoremedijacija uključuje primjenu nanomaterijala poput grafen oksida, ugljikovih nano cjevčica i metalno-organskih okvira za poboljšanje učinkovitosti uklanjanja onečišćivača. Ključni izazovi uključuju visoke troškove proizvodnje, složenost primjene i moguću toksičnost materijala, dok prednosti uključuju visoku učinkovitost uklanjanja i mogućnost primjene u različitim okruženjima. Buduća rješenja uključuju razvoj novih održivih tehnologija kako bi se poboljšala učinkovitost i smanjili troškovi.This paper will provide an overview of arsenic removal technologies and future development trends. New sustainable technologies emphasize phytoremediation and nanomaterials to address and reduce the contamination of drinking and wastewater in countries with high concentrations of arsenic. Phytoremediation uses plants to clean contaminated water from arsenic, while nano-phytoremediation involves the application of nanomaterials such as graphene oxide, carbon nanotubes, and metal-organic frameworks to enhance the efficiency of contaminant removal. Key challenges include high production costs, complexity of application, and potential material toxicity, while advantages include high removal efficiency and the ability to be applied in various environments. Future solutions involve the development of new sustainable technologies to improve efficiency and reduce costs
Determination of droplet size in a Karr column
No full textU ovom radu eksperimentalno je određena veličina kapi u Karrovoj koloni s ciljem da se ispita utjecaj različitih brzina pulzacije plitica i utjecaj različite geometrije rupica na pliticama.
Radi lakše interpretacije dobivenih podataka rezultati su prikazani kumulativnom funkcijom i funkcijom gustoće raspodjele te su izračunate statističke veličine (mod, medijan, širina raspodjele, Sauterov srednji promjer). Također su procijenjeni parametri položaja i parametri raspršenosti iz LN i RRSB funkcija raspodjele. Korištenjem plitice iste raspodjele i veličine rupica te povećanjem intenziteta miješanja ostvareni su najpovoljniji uvjeti za provođenje ekstrakcije u Karrovoj koloni jer osiguravaju najbolji kontakt dviju faza, odnosno najveću specifičnu međufaznu površinu nastankom više kapljica manjih dimenzija.In this work, the determination of the droplet sizes in the Karr column was carried out with the aim of investigating the influence of different pulsation rates of the plates and the influence of different geometries of the holes on the plates. To facilitate the interpretation of the data obtained, the results are represented by the cumulative function and the distribution density function and statistical quantities (mode, median, distribution width, Sauter mean diameter) are calculated. In addition, location parameters and parameters giving the spread of the distribution were estimated from LN and RRSB functions. When using plates with the same distribution and hole size and by increasing the mixing intensity, the most favorable conditions for performing the extraction in a Karr column were achieved, as they ensure the best contact between the two phases, meaning the largest interphase surface due to the formation of more droplets of smaller size
Intensification of photocatalytic processes
No full textFotokataliza je jedna od ekološki prihvatljivih tehnologija koja ima važnu ulogu u rješavanju globalnih ekoloških problema oslanjajući se na razvoj novih tehnologija. Danas sve više svjedočimo važnim dostignućima koji nadilaze “tradicionalno” kemijsko inženjerstvo, a obično se temelje na intenzifikaciji procesa. Intenzifikacija je pristup koji se pojavio kao posebna grana kemijskog inženjerstva, a može dovesti do uštede energije i smanjenja kapitalnih izdataka, te u konačnici ekološkim i sigurnosnim poboljšanjima postojećih procesa. Ovaj rad daje pregled pojedinih metoda koje se koriste za intenzifikaciju fotokatalitičkih procesa u svrhu njihova poboljšanja.Photocatalysis is one of the eco-friendly technologies that plays an important role in solving global environmental problems by relying on the development of new technologies. Today, we are witnessing important new developments that go beyond “traditional” chemical engineering and are usually based on process intensification. Intensification is an approach that has emerged as a special discipline of chemical engineering and can lead to savings in energy and a reduction in capital expenditure, resulting in environmental and safety benefits as well. This study provides an overview of certain methods used for the intensification of photocatalytic processes in order to improve them
Production of imidazolidinone solvents from cellulose
No full textU radu su opisane ključne reakcijske i separacijske veličine pri proizvodnji polarnih aprotičnih otapala 1,3-dimetil-2-imidazolidinona (DMI) i 1,3,4-trimetil-2-imidazolidinona (TMI) iz početnih sirovina celuloze i N,N’-dimetiluree (DMU) na temelju u literaturi pronađenog eksperimentalnog rada. Opisana su svojstva tih otapala, industrijski važni načini sinteze DMI, iz dostupne literature prikupljena su eksperimentalno određena fizikalna i termodinamička svojstva reakcijskih komponenti te su u brojnim slučajevima procijenjena metodama strukturno-grupnih doprinosa. Priređena je i bilanca tvari predloženog reakcijskog ciklusa te su njezine ključne veličine procijenjene mješovitim oblikom jednadžbe fazne ravnoteže
para-kapljevina. Parna faza modelirana je Peng-Robinsonovom kubnom jednadžbom stanja, a kapljevita modelom COSMO–RS (eng. COnductor like Screening MOdel for Real Solvents) čije su ovisnosti koeficijenta aktiviteta o sastavu dalje modelirani modelom NRTL
(eng. Non-Random Two Liquid). Priređena je i bilanca reakcijske entalpije te su ukratko komentirani ključni problemi i razmatranja vezana za proizvodnju u većem mjerilu.The paper describes the key reaction and separation parameters in the production of polar aprotic solvents 1,3-dimethyl-2-imidazolidinone (DMI) and 1,3,4-trimethyl-2-imidazolidinone (TMI) from the starting raw materials cellulose and N,N'-dimethylurea (DMU), based on experimental work found in the literature. The properties of these solvents are described, as well as industrially important methods of synthesizing DMI. Experimentally determined physical and thermodynamic properties of the reaction components were collected from the available literature, and in many cases, they were estimated via group contribution methods. Mass balance of the proposed reaction cycle was made, and key parameters were estimated using a mixed form of vapor-liquid equilibrium equation. The vapor phase was modeled using the Peng-Robinson cubic equation of state, and the liquid phase using the COSMO-RS (COnductor-like Screening MOdel for Real Solvents), where the dependence of the activity coefficient on composition was further modeled using the NRTL (Non-Random Two Liquid) model. Reaction enthalpy calculation was also made, and key issues and considerations concerning large-scale production were briefly discussed
Thermal transformations of new aromatic stilbene derivatives and quantum-chemical study of the reaction mechanism
No full textCilj ovog rada bio je prirediti nove heterocikličke stilbenske sustave koji će se podvrgnuti termičkim ispitivanjima u kiselom mediju u pokušaju sinteze indanskih i indenskih (metilnih, piridinskih, fenilnih i tiofenskih) derivata stilbena. Upotrebom kvantno-kemijskih računalnih metoda predviđen je ishod razmatranih kemijskih reakcija.The aim of this was to prepare new heterocyclic stilbene systems that will be subjected to the thermal tests in acidic medium in an attempt to synthesize indane and indene (methyl, pyridine, phenyl and thiophene) stilbene derivatives. The outcome of the considered chemical reactions was predicted using quantum-chemical computer methods
Characterisation of pyrolytic products produced by pyrolysis of wood chips made from oak
No full textBiomasa predstavlja obnovljiv, ugljično neutralan i lako dostupan izvor sirovine za dobivanje energije i raznih drugih produkata. Tehnologija pirolize omogućava pretvaranje biomase u vrijedne nusprodukte, kao što su bioplin i bio-ulje s posebnim naglaskom na bio-ugljen. Njegova raznolika primjena predmet je mnogih istraživanja, dok se u posljednje vrijeme ispituje mogućnost korištenja bio-ugljena kao prekursora za proizvodnju grafena. Svrha ovog rada bila je u laboratorijskom mjerilu pronaći najoptimalniju sirovinu i procesne uvjete u cilju smanjenja nastanka dioksina i furana te dobivanja što većeg prinosa bio-ugljena kao željenog produkta. Nakon preliminarnih rezultata dobivenih pomoću analize plinova, kalorijske vrijednosti, elementarne analize te analize teških metala, odabrani uzorak „Hrast“ podvrgnut je pirolizi u poluindustrijskom mjerilu pri 800 ⁰C. Dobiveni bio-ugljen modificiran je s ciljem dobivanja grafen oksida i to na dva načina. Dio uzorka podvrgnut je Hummersovoj metodi, a dio persulfatnoj interkalaciji grafitnog materijala. Tako interkalirani uzorak stavljen je u mufolnu peć kako bi se dodatno termički ekspandirao. Rezultati morfološke, strukturne i elektrokemijske analize pokazali su kako svi uzorci imaju grafitnu strukturu sa slobodnim π-elektronima, dok najveći potencijal za daljnju obradu ima upravo uzorak modificiran po Hummersu. On ima najjednostavniji kemijski sastav, najuređeniju strukturu i najveći doprinos sp2 hibridizirane veze.Biomass is a renewable, carbon-neutral and easily available source of raw material for obtaining energy and various other products. Pyrolysis enables the conversion of biomass into valuable by-products, such as biogas and bio-oil with a special emphasis on biochar. Its diverse application is the subject of many studies, while recently the possibility of using bio char as a precursor for the production of graphene has been examined. The purpose of this work was to find the most optimal raw material and process conditions on a laboratory scale in order to reduce the formation of dioxins and furans and obtain the highest possible yield of biochar as the desired product. After preliminary results obtained using gas analysis, calorific value, elemental analysis and heavy metal analysis, the selected sample "Oak" was subjected to pyrolysis on a semi-industrial scale at 800 ⁰C. The obtained biochar was modified with the aim of obtaining graphene oxide in two ways. Part of the sample was subjected to the Hummers method, and part to persulfate intercalation of graphite material. The thus intercalated sample was placed in a muffle furnace to further expand thermally. The results of the morphological, structural and electrochemical analysis showed that all samples have a graphite structure with free π-electrons, while the sample modified according to Hummers has the greatest potential for further processing. It has the simplest chemical composition, the most ordered structure and the largest contribution of hybridized sp2 bonds
Regeneration of NAD(P)+ in the oxidation reactions catalyzed by oxidoreductases
No full textIndustrijski procesi temeljeni na biokatalizi korištenjem enzima ili cijelih stanica smatraju se ekološki prihvatljivom tehnologijom. Oksidoreduktaze su jedna od najvećih skupina enzima (25 % svih enzima) i imaju veliku industrijsku i znanstvenu važnost. Glavna prepreka njihovoj široj primjeni je činjenica da ovi enzimi zahtijevaju kofaktore koji se troše tijekom reakcije, pri čemu je potrebno pronaći odgovarajući način za njihovu regeneraciju. Koenzimi NAD+ i NADP+ služe kao oksidansi koji se reduciraju u NAD(P)H dok se supstrat oksidira u ciljni produkt. U ovom radu provedeno je istraživanje potencijalne upotrebe enzima NAD(P)H oksidaze (NOX) za regeneraciju koenzima u reakcijama oksidacije. Budući da je upotrijebljeni enzim aktivan u reakcijama oksidacije koenzima NADH i NADPH, provedene su reakcije oksidacije supstrata etanola i 2-propanola s dva različita enzima i određen je ukupni broj obrtaja koenzima u svakoj reakciji. Izmjerena je kinetika svih enzima te je uspostavljen i validiran procesni model u kotlastom bioreaktoru. Rezultati pokazuju da se NOX može uspješno primjeniti za regeneraciju koenzima, pri čemu je enzim učinkovitiji prilikom regeneracije NADP+.Industrial processes based on biocatalysis using enzymes or whole cells are considered environmentally friendly technology. Oxidoreductases are one of the largest classes of enzymes (25 % of all enzymes) and have far-reaching industrial and scientific importance. The main obstacle to their wider application is the fact that these enzymes require cofactors that are consumed during the reaction and it is necessary to find a suitable way for their regeneration. The coenzymes NAD+ and NADP+ serve as oxidants that are reduced to NAD(P)H while the substrate is oxidized to the target product. This study investigated the potential use of regenerating coenzymes in oxidation reactions using the enzyme NAD(P)H oxidase (NOX). Ethanol and 2-propanol oxidation processes were carried out with two enzymes, and the total turnover number of coenzymes in each reaction was calculated.
The kinetics of all enzymes were measured and a process model was established and validated in a batch bioreactor. The findings indicate that the application of NOX for the regeneration of coenzymes is feasible, with NADP+ showing significantly better results