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  • 2013-2022
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  • Kemija u Industriji

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  • Open Access English
    Authors: 
    Cemre Avşar; Didem Tümük; Abdullah Emre Yüzbaşıoğlu; Ahmet Ozan Gezerman;
    Country: Croatia

    Due to greenhouse gas emissions in industrial production, global warming and the resulting climate change pose significant threats to a liveable world. The emission of carbon dioxide, which is released as a result of industrial activities, is the most important component that triggers the global warming process. The use of waste material, which is the result of industrial activity, as raw material within the framework of circular economy is of vital importance in terms of the use of sustainable resources. The problem of phosphogypsum, which is released during the production of phosphoric acid, can be eliminated by the Merseburg process. With such waste minimisation, the destruction caused by emission gases such as carbon dioxide in the atmosphere will also be prevented. In this evaluation study, the use of carbon dioxide gas as a raw material is discussed, while reducing the emission values of industries such as cement and thermal power plants that cause large amounts of carbon dioxide emissions from phosphogypsum waste. Although an ammonium sulphate production is foreseen with the evaluation of carbon dioxide and phosphogypsum waste with the Merseburg process, the effect of the impurity content of the waste material used on the recommended ammonium sulphate concentration will be an important research topic. Various protocols are being worked on worldwide in order to minimise the emissions on international scale. The use of the Merseburg process for this and similar processes will provide significant advantages to the manufacturer in reaching the targeted emission amount. Globalno zatopljenje i klimatske promjene, kao rezultat emisija stakleničkih plinova u industriji, predstavljaju veliku prijetnju živom svijetu. Ugljikov dioksid, koji se oslobađa kao rezultat industrijskih aktivnosti, najvažnija je komponenta u procesu globalnog zagrijavanja. Otpadni materijal, kao još jedan produkt industrijske aktivnosti, može se u okviru kružnog gospodarstva upotrebljavati kao sirovina. Problem fosfogipsa, koji se oslobađa tijekom proizvodnje fosforne kiseline, može se otkloniti Merseburg procesom. Takvim smanjenjem otpada smanjit će se i destrukcija uzrokovana emisijom plinova, poput ugljikova dioksida, u atmosferu. U ovoj studiji komentirana je uporaba plinovitog ugljikova dioksida kao sirovine, uz smanjenje njegovih emisija u cementarama i termoelektranama, gdje se emitiraju velike količine ugljikova dioksida iz fosfogipsnog otpada. U svijetu se radi na različitim protokolima da bi se smanjile emisije na međunarodnoj razini. Primjena Merseburg procesa za taj i slične procese pružit će značajnu prednost proizvođačima u postizanju ciljanih količina emisija.

  • Publication . Article . Other literature type . 2022
    Open Access English
    Authors: 
    Bensaber Bensebia; Fatma Zohra Chaouche; Soumia Kouadri Moustefaï;
    Country: Croatia

    Knowledge of gas holdup is important for the development of the three-phase fluidized bed reactors. This work concerns the study of the effect of different operating conditions on gas retention in a turbulent bed contactor type 2 (TBC), such as superficial gas and liquid velocities, liquid to gas mass flows ratio (L/G), particle diameter and density, static bed height and free-open area of the supporting grid. The influence of the free area of the packing support grid (φ) on gas holdup was demonstrated and proved. The gas holdup increased to 22.92 % when φ decreased from 0.82 to 0.32. The experimental data (1746) led to the development of two correlations to predict gas holdup, one of which incorporated the ratio (L/G) which is an important design factor for gas-liquid contactors. The predicted results of holdup gas were in good agreement with the experimental data. Poznavanje zadržavanja plina važno je za razvoj trofaznih reaktora s fluidiziranim slojem. Ovaj rad bavi se proučavanjem utjecaja različitih radnih uvjeta na zadržavanje plina u kontaktoru s turbulentnim slojem tipa 2 (TBC), kao što su površinske brzine plina i tekućine, omjer masenih protoka tekućine i plina (L/G), promjer čestica i gustoća, statička visina sloja i slobodna otvorena površina potporne rešetke. Dokazan je utjecaj slobodne površine potporne rešetke (φ) na zadržavanje plina. Zadržavanje plina povećalo se na 22,92 % kad se φ smanjio s 0,82 na 0,32. Iz dobivenih eksperimentalnih rezultata (1746) razvile su se dvije korelacije za predviđanje zadržavanja plina, od kojih je jedna uključivala omjer L/G, koji je važan faktor pri dizajnu plinsko-tekućinskih kontaktora. Predviđeni rezultati zadržavanja plina podudarali su se s eksperimentalnim podatcima.

  • Open Access
    Authors: 
    Čulo, Ivana; Grgić, Filip; Jurina, Tamara; Šalić, Anita; Benković, Maja; Valinger, Davor; Gajdoš Kljusurić, Jasenka; Jurinjak Tušek, Ana; Zelić, Bruno;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Emulsions are traditionally prepared with the application of high shear forces generated by the use of static mixers, homogenisers, or ultrasound. The resulting emulsions are sensitive to change of process conditions. The application of high forces and temperatures can significantly affect the constituents of the emulsions and their final stability. Microfluidic technology seems to be a very efficient alternative to classic emulsification methods. The dimensions of microdevices in combination with continuous processes offer a great advantage over classic batch emulsification processes carried out on a larger scale. The small dimensions of the microdevices allow easy transport of equipment, better control and safety of the process, and intensified mass and energy transfer. The mixing time in microdevices is reduced to a few milliseconds because the molecules in the microchannels have a short diffusion path. In this paper, an overview of emulsification processes, the advantages of use of microfluidics in emulsification, and future perspectives of microemulsification are presented. Tradicionalno se emulzije pripremaju primjenom jakih smičnih sila koje nastaju upotrebom statičkih miješala, homogenizatora ili primjenom ultrazvuka. Tako proizvedene emulzije osjetljive su na promjenu procesnih uvjeta. Primjena jakih sila i povišenih temperatura može značajno utjecati na komponente emulzija i njihovu konačnu stabilnost. Primjena protočnih mikrosustava pokazala se učinkovitom alternativnom tehnologijom klasičnim metodama emulgiranja. Male dimenzije mikrouređaja u kombinaciji s kontinuiranom provedbom procesa omogućuje brojne prednosti u odnosu na klasične šaržne procese emulsifikacije koji se provode u većem mjerilu. Male dimenzije mikrouređaja omogućuju lakši transport opreme, bolju kontrolu i sigurnost procesa te intenzivniji prijenos tvari i topline. Vrijeme miješanja u mikrouređajima smanjeno je na nekoliko milisekundi zbog kratkog difuzijskog puta molekula u mikrokanalima. U ovom radu dan je pregled procesa emulgiranja, prednosti primjene protočnih mikrosustava u provedbi procesa emulgiranja te potencijalnih novih područja primjene te tehnologije.

  • Publication . Other literature type . Article . 2022
    Open Access English
    Authors: 
    Houda Douba; Ourida Mohammedi; Benamar Cheknane;
    Country: Croatia

    The present study aimed to evaluate the potential of mesoporous silica MCM-41 and Al-MCM-41 (molar ratio Si/Al = 20) for the removal of Rhodamine 6G (Rh6G) from aqueous solution. The adsorbents were characterised by XRD, FTIR, SEM-EDX, BET, and UV-Raman. Obtained results related to XRD analysis indicated that the MCM-41 structure remained intact after the incorporation of Al species. Kinetic adsorption study showed that the higher removal (88.75 %, 26.62 mg g–1) of Rh6G dye was achieved by Al-MCM-41 at 60 min. FTIR analysis showed that hydrogen bonding played the dominant role in the Rh6G removal mechanism, while the pH results showed that electrostatic interaction was also a key factor. This study shows that the prepared mesoporous materials are inexpensive and efficient adsorbents for the removal of cationic dyes. Cilj ovog istraživanja bio je procijeniti potencijal mezoporoznih silikata MCM-41 i Al-MCM-41 (molarni omjer Si/Al = 20) za uklanjanje rodamina 6G (Rh6G) iz vodene otopine. Za karakterizaciju adsorbensa primijenjeni su XRD, FTIR, SEM-EDX, BET i UV-Raman. Rezultati XRD analize pokazali su da je struktura MCM-41 nakon ugradnje iona Al ostala netaknuta. Kinetička analiza adsorpcije pokazala je da je u 60. minuti veće uklanjanje Rh6G bojila postignuto uporabom Al-MCM-41 (88,75 %, 26,62 mg g–1). FTIR analiza pokazala je da vodikova veza ima dominantnu ulogu u mehanizmu uklanjanja Rh6G, dok su rezultati pH pokazali da je elektrostatička interakcija također ključni čimbenik. Ovo istraživanje pokazalo je da su pripremljeni mezoporozni materijali jeftini, ali učinkoviti adsorbensi za uklanjanje kationskih boja.

  • Open Access English
    Authors: 
    Toyese Oyegoke; Fadimatu Nyako Dabai; Saidu Muhammad Waziri; Adamu Uzairu; Baba Yakubu Jibril;
    Country: Croatia

    The impact of molybdenum (Mo) and tungsten (W) on improving the catalytic characteristics of the chromium-based catalyst, Cr2O3, was explored in this study. The use of semi-empirical and density functional theory computational methods was deployed to understand the impact of the substitution of the chromium (Cr) with Mo and W on the catalyst, CrXO3 (where X = Cr, Mo, W) in the production of propylene from propane. Findings from the investigation confirmed that the surface modified with Mo showed better potential for improving the catalyst selectivity, retarding propylene dehydrogenation, cracking, and coking path than W, which offered a lower selectivity. The use of Mo was found to have better facilitated the propylene production due to its lower affinity for coke and cracking promoting adsorbates accounted for its sites, including easier desorption of propylene and higher barrier of deep dehydrogenation for preventing the production of undesired products, unlike the use of W. This study, therefore, recommends the use of Mo for the improvement of the catalyst that could result in better propylene yield, which could aid in meeting its rising market demand. S ciljem poboljšanja karakteristika katalizatora na bazi kroma, u ovom su se istraživanju kombinirano primijenile poluempirijske računalne metode i metode temeljene na teoriji funkcionala gustoće. Nastojao se dobiti uvid u katalitički potencijal izmjene kroma molibdenom i volframom u katalizatoru CrXO3 (gdje X označava krom, molibden i volfram) za dehidrogeniranje propana pri proizvodnji propilena. Rezultati su potvrdili da površina modificirana molibdenom pokazuje bolju selektivnosti u usporedbi s površinom modificiranom volframom, usporavajući dehidrogenaciju, pucanje i koksiranje propilena. Utvrđeno je da upotreba molibdena olakšava proizvodnju propilena zbog njegova nižeg afiniteta prema adsorbatima koji potiču pucanje i koksiranje, uključujući i lakšu desorpciju propilena te višu barijeru potpune dehidrogenacije što sprječava nastanak neželjenih produkata; to nije bio slučaj kod volframa. Ovo istraživanje stoga preporučuje upotrebu molibdena za poboljšanje svojstava katalizatora, što bi moglo rezultirati većim iskorištenjem u proizvodnji propilena te pomoći zadovoljavanju rastuće tržišne potražnje za propilenom.

  • Open Access
    Authors: 
    Pazalja, Mirha; Salihović, Mirsada; Smajović, Alisa;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Ash is a by-product of wood biomass combustion that must be removed daily from stoves or fireplaces. Therefore, operators or owners are exposed to the potential impact of ash. The goal of this study was to determine whether heavy metal present in wood pellet ash posed a health concern to stove operators/owners. The risk assessment procedure was carried out in several steps, including exposure evaluation, toxicity evaluation, and risk categorisation. The hazard coefficient (HQ) and non-carcinogenic hazard index (HI) were calculated for Cd, Cr, Cu, Ni, Pb, and Zn. HQ had the highest value for the ingestion pathway (3.62 ∙ 10–6), and the value for non-carcinogenic HI was 3.70 ∙ 10–6. The value HI < 1 suggests that there is no risk to operator health related to heavy metals in analysed wood pellets ash. The carcinogenic risk (CR) was calculated for Ni, Pb, Cr, and Cd, and the values were within the permitted limits. The risk assessment based on HI and CR indicators proved that there was no significant health concern regarding exposure to the analysed ashes. Pepeo je nusproizvod izgaranja drvne biomase koji se svakodnevno mora uklanjati iz peći ili kamina. Stoga su operateri ili vlasnici izloženi potencijalnom utjecaju pepela. Ovo istraživanje ima cilj procijeniti zdravstveni rizik izloženosti operatera/vlasnika pepelu drvenih peleta zbog sadržaja teških metala. Postupak procjene rizika proveden je u nekoliko koraka uključujući procjenu izloženosti, procjenu toksičnosti i kategorizaciju rizika. Izračunati su koeficijent opasnosti (HQ) i indeks nekarcinogene opasnosti (HI) za Cd, Cr, Cu, Ni, Pb i Zn. HQ je imao najveću vrijednost za izloženost putem gutanja (3.62 ∙ 10–6), a vrijednost za nekarcinogeni HI bila je 3.70 ∙ 10–6. Vrijednost HI < 1 ukazuje na to da sadržaj teških metala u analiziranom pepelu ne predstavlja rizik za zdravlje operatera. Karcinogeni rizik (CR) izračunat je za Ni, Pb, Cr i Cd, a vrijednosti su bile unutar dopuštenih granica. Rizik procijenjen primjenom HI i CR pokazatelja potvrdio je da ne postoji značajna opasnost za zdravlje osoba koje dolaze u kontakt s analiziranim pepelom.

  • Publication . Article . Other literature type . 2022
    Open Access Croatian
    Authors: 
    Mirko Budiša; Anita Ptiček Siročić;
    Country: Croatia

    In the last fifty years, there has been a significant increase in plastic waste, which has become an increasing environmental problem due to uncontrolled dumping, with significant consequences on living ecosystems. Plastic is an important and ubiquitous material in the economy and everyday life, and nearly 26 million tonnes of plastic waste are generated annually in the countries of the European Union. About 30 % of this waste is recycled, a significant part is recovered for energy, and part is still disposed of in landfills. Recycling plastic waste preserves natural raw materials such as oil and natural gas, which are used to produce plastic materials, and reduces emissions into the environment and energy consumption. Under the Resource Efficient Europe Plan, plastic waste is recognised as an important raw material for the production of new products, and is one of the key raw materials in the transition to a circular economy. This paper presents general possibilities for recycling plastic waste. Based on the indicative examination results of the composition of separately collected plastic waste in Zagreb, an assessment of the possibility of its recycling is given. In the Republic of Croatia, plastic waste is a major problem since it is inadequately sorted, and therefore represents a significant financial burden for utility companies that manage it within public service of municipal waste collection. U zadnjih pedesetak godina zabilježen je značajan rast količina plastičnog otpada koji nekontroliranim odbacivanjem postaje sve veći problem za okoliš i sa značajnim posljedicama na živuće ekosustave. Plastika je važan i sveprisutan materijal u gospodarstvu i svakodnevnom životu i godišnje u zemljama Europske unije nastaje blizu 26 milijuna tona plastičnog otpada. Oko 30 % tog otpada se reciklira, znatan dio se energetski oporabljuje, a dio se još uvijek odlaže i na odlagališta otpada. Recikliranjem plastičnog otpada čuvaju se prirodne sirovine kao što su nafta i zemni plin koje se upotrebljavaju za proizvodnju plastičnih materijala te se smanjuju emisije u okoliš i potrošnja energije. Planom za resursno učinkovitu Europu, plastični otpad prepoznat je kao važna sirovina za proizvodnju novih proizvoda i jedna je od ključnih sirovina u prelasku na kružno gospodarstvo. U ovom je radu dan prikaz općih mogućnosti recikliranja tj. oporabe plastičnog otpada. Na temelju indikativnih rezultata ispitivanja sastava odvojeno prikupljenog plastičnog otpada u Zagrebu dana je procjena mogućnosti njegove reciklaže. U Republici Hrvatskoj plastični otpad velik je problem budući da se adekvatno ne sortira. Zbog toga je značajno financijsko opterećenje komunalnim društvima koja njime gospodare u sklopu javne usluge prikupljanja komunalnog otpada.

  • Open Access Croatian
    Authors: 
    Ivana Cetina; Dragutin Tušek; Valentina Ključarić;
    Country: Croatia

    Shortly after introduction of commercial automatic chemical detectors, mostly based on ion mobility spectrometry technology, at the end of 20th century field devices using other chemical detection techniques (FTIR, Raman, GC-MS, surface acoustic wave, photoacoustic, electrochemical, biosensor and others) were developed. Among these techniques, portable GC-MS detectors provide very reliable qualitative and quantitative chemical analysis, but high cost of these devices, the complexity of operating with them and the complexity of sample preparation for analysis present a problem. Some chemical detection technologies cannot be used for the development of a reliable hand-held chemical detector, and not a single technique, for the time being, allows the development of a universal chemical detector. A potential solution is the development of a multi-sensor device that compensates negative sides of each of the sensors. This paper provides an overview of commercially available chemical detectors based on new generation detection technologies and an overview of scientific research focused on further development of detection with simpler, more reliable and preferably cheaper solutions is given. Ubrzo nakon uvođenja komercijalnih automatskih detektora bojnih otrova, većinom temeljenih na spektrometriji ionske pokretljivosti, krajem 20. stoljeća razvijaju se terenski uređaji koji primjenjuju i druge tehnike kemijske detekcije (FTIR, Raman, GC-MS, površinski akustični val, fotoakustične, elektrokemijske, biosenzorske i ostale). Od navedenih tehnika, prijenosni GC-MS detektori omogućuju vrlo pouzdanu kvalitativnu i kvantitativnu kemijsku analizu, no problem predstavljaju visoka cijena tih uređaja, zahtjevnost u rukovanju s njima te kompleksna priprema uzoraka. Neke tehnike kemijske detekcije nisu primjenjive za razvoj pouzdanog ručnog kemijskog detektora, a niti jedna tehnika, zasad, ne omogućuje razvoj univerzalnog kemijskog detektora. Potencijalno rješenje je razvoj višestrukog senzorskog uređaja koji bi kompenzirao negativne strane svakog od senzora. U ovom radu dan je pregled komercijalno dostupnih kemijskih detektora temeljenih na novim generacijama tehnika detekcije te pregled znanstvenih istraživanja usmjerenih na daljnji razvoj detekcije bojnih otrova s jednostavnijim, pouzdanijim i poželjno jeftinijim rješenjima.

  • Publication . Other literature type . Article . 2022
    Open Access
    Authors: 
    Žagar, Patricia; Božičević, Marin; Fiket, Lucija; Blažic, Roko; Sačer, Denis; Katančić, Zvonimir;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Poly(3,4-ethylenedioxythiophene) (PEDOT) is a conductive polymer used in batteries, supercapacitors, solar cells, and various biosensors in wearable electronics. Through controlled atom transfer radical polymerisation (ATRP), it is possible to modify the properties of PEDOT for specific applications by grafting the side branches. In this work, PEDOT-based ATRP macroinitiators, functionalised with reactive bromine allowing the grafting of different polymers as side branches, were synthesised. Characterisation of the obtained samples was carried out by NMR, FTIR, GPC, TGA and measurement of electrochemical properties. Results showed that the sample with lower bromine content had better chemical properties; hence it was more suitable for further synthesis and modification of PEDOT. Poli(3,4-etilendioksitiofen) (PEDOT) je elektrovodljivi polimer koji se primjenjuje u baterijama, superkondenzatorima, solarnim ćelijama i različitim biosenzorima u nosivoj elektronici. Kontroliranom radikalskom polimerizacijom prijenosom atoma (ATRP) moguće je cijepljenjem bočnih grana modificirati svojstava PEDOT-a za specifičnu primjenu. U ovom radu sintetizirani su ATRP makroinicijatori na osnovi PEDOT-a, funkcionalizirani reaktivnim bromom, koji omogućuje cijepljenje različitih polimera kao bočnih grana. Karakterizacija dobivenih uzoraka provedena je pomoću NMR-a, FTIR-a, GPC-a, TGA-a i mjerenjem elektrokemijskih svojstava. Pokazalo se da uzorak s manjim udjelom broma ima bolja kemijska svojstva i kao takav je prikladniji za daljnju sintezu i modifikaciju PEDOT-a.

  • Open Access English
    Authors: 
    Stjepan Kožuh; Ivana Ivanić; Tamara Holjevac Grgurić; Mirko Gojić;
    Country: Croatia

    The aim in this work was to investigate the change in microstructure, phase transformation temperatures, and thermal properties due to the quenching of the investigated Cu-Al-Mn and Cu-Al-Mn-Ti alloys in ribbon form. This paper presents the results of microstructure analysis and thermal properties of Cu-Al-Mn and Cu-Al-Mn-Ti shape memory alloys produced in ribbon form by melt spinning technique. The microstructural analysis was carried out before and after quenching. After casting of the investigated alloys, annealing at 900 °C for 30 min was performed, followed by water quenching. The microstructural analysis was carried out by optical and scanning electron microscopy equipped with an energy dispersive spectrometer and by X-ray diffractometer. Thermodynamic calculation of a ternary Cu-Al-Mn system in equilibrium condition was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry and electrical resistance measuring. The results of microstructural analysis show the presence of martensite microstructures before and after quenching in the Cu-Al-Mn alloy, while in the Cu-Al-Mn-Ti alloy martensite microstructure exists only after quenching. Phase transformation temperatures decreased after quenching and titanium addition. Cilj rada bio je istražiti promjene u mikrostrukturi, temperaturama transformacije i toplinskim svojstvima nastale uslijed kaljenja Cu-Al-Mn i Cu-Al-Mn-Ti legura u obliku trake. U radu su prikazani rezultati mikrostrukturne analize i toplinskih svojstava Cu-Al-Mn i Cu-Al-Mn-Ti legura s prisjetljivosti oblika proizvedenih u obliku trake postupkom melt spinning. Mikrostrukturna analiza je provedena prije i nakon kaljenja. Nakon lijevanja istraživane legure su žarene pri 900 °C u trajanju 30 minuta, nakon čega je slijedilo kaljenje u vodi. Mikrostrukturna analiza je provedena optičkim i pretražnim elektronskim mikroskopom opremljenim energetsko disperzijskim spektroskopom te rendgenom. Termodinamički proračun ternarnog Cu-Al-Mn sustava proveden je u ravnotežnim uvjetima pomoću Thermo-Calc 5 programskog paketa. Temperature fazne transformacije određene su diferencijalnom pretražnom kalorimetrijom i mjerenjem električnog otpora. Rezultati mikrostrukturne analize pokazuju prisutnost martenzitne mikrostrukture prije i nakon kaljenja Cu-Al-Mn legure, dok u Cu-Al-Mn-Ti leguri martenzitna mikrostruktura postoji samo nakon kaljenja. Temperature faznih transformacija smanjuju se nakon kaljenja i dodatka titana.

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