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  • 2012-2021
  • Open Access
  • Article
  • Kemija u Industriji

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  • Open Access English
    Authors: 
    Barišić, L.; Rapić, V.;
    Publisher: Croatian Society of Chemical Engineers

    This article is the second part of a series dealing with organometallic and bioorganometallic chemistry. In the first part of this series a short review on the history and development of these disciplines was given, emphasizing the importance and scope of bioorganometallic chemistry as a new field dealing with conjugates of organometallics and biomolecules (DNA, PNA, amino acids, peptides...). From the variety of biorganometallics, syntheses and properties of simple conjugates of ferrocene with natural amino acids/peptides were elaborated inter alia. This material is the basis for the second part in which ferrocene amino acids are described. The introduction presents nonproteinogenic alicyclic and aromatic amino acids as the models for the title compounds. Naturally occurring amino acids labelled with ferrocene moiety mostly retain properties of the biomolecules included. Contrary to these ω-ferrocenylamino acids, one could imagine specific amino acids with inserted ferrocene core belonging to either homo- or heterodisubstituted type. The central part of this article is devoted to our investigations of the second type - H2N-(CH2)m-Fn-(CH2)n-COOH. The general rational procedure for synthesis of these compounds and of their N- and/or C-protected derivatives via the azide intermediates N3-CO-(CH2)m- Fn-(CH2)n-COOMe has been described. In the solid state derivatives of ferrocene amino acids contain intermolecular hydrogen bonds giving dimeric structures, three-dimensional networks or endless helical chains. The solutions of homologues Ac-NH-(CH2)m-Fn-(CH2)n-COOMe in nonpolar solvents are dominated by open form conformers. Compounds containing 2–3 ferrocene cores connected by amide, imide and oxalamide spacers were prepared by oligomerization of 1'-aminoferrocene-1-carboxylic acid (Fca) or by its condensation with the appropriate reagents. Similar to natural amino acids, ferrocene amino acids are water-soluble substances with high melting points, insoluble in organic solvents.

  • Publication . Article . 2019
    Open Access English
    Authors: 
    Nenad Raos;
    Publisher: Croatian Society of Chemical Engineers

    Rad se bavi razvojem pojma elementa od antičkih vremena (Empedoklo, Aristotel) preko razdoblja alkemije i rane kemije (Paracelsus, Petar Bono, Boyle) te početaka moderne kemije (Lavoisier, Mendeljejev) do suvremenih shvaćanja utemeljenih na atomskoj teoriji. Pokazuje se da pojam elementa ima dva značenja, elementarne (jednostavne) tvari i elementa u užem smislu; dok se prvi pojam razvijao prateći napredak metoda kemijske analize, za razumijevanje drugog pojma, pojma elementa, bilo je nužno steći dublji uvid u narav kemijskih promjena.

  • Open Access
    Authors: 
    Vlado Merzel; Sanja Lučić Blagojević; Zrinka Buhin Šturlić; Mario Meheš; Mirela Leskovac;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    In this paper, the influence of flame treatment on the surface properties of polypropylene (PP) and thermoplastic polyolefins with talc and carbon black filler (TPO), and adhesion of the applied coating in the conditions of industrial robotic dyeing process were investigated. The flame treatment was carried out at two distances from the flame (7.5 cm and 12.5 cm) at constant air and methane flows as well as speed of the burner. The thermal stability of untreated samples was investigated using thermogravimetric analysis (TGA). The change in thermal properties before and after flame treatment was investigated using differential scanning calorimetry (DSC). Changes of the samples’ surface energy were examined before flame treatment, 1 h and 24 h after flame treatment, by the contact angle method. Qualitative analysis of the surface chemical composition, before and after flame treatment, was performed by ATR – FTIR analysis, and morphological changes by scanning electron microscopy (SEM). After applying the base layer, dye and topcoat on the surface of the treated samples, the adhesion was determined by standard methods ISO 2409 and ISO 16925/D25 2018-B. The results showed that TPO containing talc and carbon black filler have better thermal stability compared to PP. Flame treatment influenced the surface characteristics of the samples, namely the increase in surface free energy and the appearance/structure of the surface. With ATR – FTIR, the existence of polar groups on the surface after flame treatment were determined. According to the standards, all dyed samples met the requirements of excellent adhesion on the substrate/coating interface. This work is licensed under a Creative Commons Attribution 4.0 International License. U ovom radu istražen je utjecaj obrade plamenom polipropilena (PP) i termoplastičnih poliolefina s talkom i čađom (TPO) na površinska svojstva i adheziju nanesenog premaza u uvjetima industrijskog procesa robotskog bojenja. Obrada plamenom provedena je na dvije udaljenosti plamena od površine (7,5 cm i 12,5 cm) pri konstantnom protoku zraka i metana te brzini kretanja plamenika. Toplinska postojanost netretiranih uzoraka ispitana je primjenom termogravimetrijske analize (TGA). Promjena toplinskih svojstava prije i nakon obrade plamenom praćena je primjenom diferencijalne pretražne kalorimetrije (DSC). Metodom kontaktnog kuta određena je površinska energija uzoraka prije obrade plamenom te 1 h i 24 h nakon obrade plamenom. Promjene uzrokovane obradom plamenom istražene su ATR – FTIR analizom, a morfološke promjene pretražnim elektronskim mikroskopom (SEM). Nakon nanošenja temeljnog sloja, sloja boje i sloja laka na površinu obrađenih uzoraka određena je adhezija standardnim metodama ISO 2409 i ISO 16925/D25 2018-B. Rezultati su pokazali da TPO uzorci koji sadrže punilo talk i čađu imaju bolju toplinsku postojanost u odnosu na PP. Obrada plamenom utječe na promjenu površinskih karakteristika uzoraka, povećanje slobodne površinske energije i na izgled/strukturu površine. ATR – FTIR analizom utvrđeno je postojanje polarnih skupina na površini nakon obrade plamenom. Svi obojeni uzorci prema zahtjevima normi zadovoljavaju uvjete izvrsne adhezije na međupovršini supstrat/premaz. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

  • Open Access Croatian
    Authors: 
    Nikolina Mrkonjić; Gordana Martinko; Emi Govorčin Bajsić; Igor Slivac; Vedrana Špada; Tamara Holjevac Grgurić;
    Country: Croatia

    Polilaktidna kiselina (PLA) i bakterijska nanoceluloza (BNC) zbog svoje biorazgradljivosti, biokompatibilnosti i netoksičnosti imaju velik potencijal za primjenu u biomedicini. Cilj ovog rada bio je pripraviti i ispitati biokompozit PLA/BNC. Istražen je utjecaj BNC-a na morfološku strukturu, kemijski sastav, toplinska svojstva, toplinsku postojanost i hidrofobnost PLA te zasijavanje i rast stanica biokompozita PLA/BNC primjenom pretražnog elektronskog mikroskopa (SEM), infracrvene spektroskopije (FTIR), diferencijalne pretražne kalorimetrije (DSC) i termogravimetrijske analize (TGA) te određivanjem kontaktnog kuta i metodom MTT. Dodatkom BNC-a u PLA dolazi do pomaka staklišta (Tg) prema nižim temperaturama, što ukazuje na veću pokretljivost amorfne faze PLA te porasta stupnja kristalnosti zbog nukleacijskog učinka celuloze. Početak toplinske razgradnje pomaknut je na niže temperature u odnosu na čisti PLA, što ukazuje na smanjenje toplinske postojanosti PLA dodatkom BNC-a. Biokompozit PLA/BNC pokazuje poroznu, vlaknastu strukturu. Test zasijavanja stanica pokazao je da je biokompozit PLA/BNC pogodan za prihvaćanje i rast humanih stanica, pa je prema tome potencijalno primjenjiv u regenerativnoj medicini i tkivnom inženjerstvu. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna. Polylactic acid (PLA) and bacterial nanocellulose (BNC) are promising materials in medicine due to their biodegradability, biocompatibility, and non-toxicity. The aim of this work was to prepare and characterize the PLA/BNC biocomposite. Morphology, chemical composition, thermal properties, thermal stability, hydrophobicity and cell seeding, and growth of the PLA/BNC biocomposite were characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle, and MTT method. DSC showed that the glass transition temperature (Tg) of PLA decreased with the addition of BNC due to higher mobility of amorphous PLA phase. The degree of crystallinity increased due to nucleation effect of cellulose. With the addition of BNC, the thermal stability of biocomposite decreased. The PLA/BNC biocomposite exhibited a porous, fibrous structure. The cell seeding test showed the PLA/BNC biocomposite to be suitable for growth of human cells, and therefore, potentially applicable in regenerative medicine and tissue engineering. This work is licensed under a Creative Commons Attribution 4.0 International License.

  • Open Access English
    Authors: 
    Yun-Fei Long; Xiao-Yan Lv; Yi-Ju Lv; Yogn-Ni Li; Jing Su; Yanxuan Wen;
    Publisher: Croatian Society of Chemical Engineers

    Manganese is widely used in many fields. Many efforts have been made to recover manganese from low-grade pyrolusite due to the depletion of high-grade manganese ore. Thus, it is of practical significance to develop a clean, energy-saving and environmentally friendly technical route to reduce the low-grade pyrolusite. The reported results show that biomass wastes from crops, crop waste, wood and wood waste are environmentally friendly, energy-saving, and low-cost reducing agents for roasting reduction of low-grade pyrolusite. Kinetics of the reduction reactions is necessary for an efficient design of biomass reduction of pyrolusite. Therefore, it is important to look for a general kinetics equation to describe the reduction of pyrolusite by different kinds of biomass, because there is a wide variety of biomass wastes, meaning that it is impossible to investigate the kinetics for each biomass waste. In this paper, thermal gravimetric analysis and differential thermal analysis were applied to study the overall reduction kinetics of pyrolusite using a mixture of hemicellulose and lignin, two major components of biomass. Overall reduction process is the overlap of the respective reduction processes. A new empirical equation based on the Johnson–Mehl–Avrami equation can be used to describe the respective reduction kinetics using hemicellulose and lignin as reductants, and the corresponding apparent activation energy is 30.14 kJ mol−1 and 38.91 kJ mol−1, respectively. The overall kinetic model for the reduction of pyrolusite by the mixture of hemicellulose and lignin can be simulated by the summation of the respective kinetics by considering their mass-loss fractions, while a unit step function was used to avoid the invalid conversion data. The obtained results in this work are necessary to understand the biomass reduction of pyrolusite and provide valuable assistance in the development of a general kinetics equation.

  • Publication . Article . Other literature type . 2015
    Open Access English
    Authors: 
    M. Šekutor; K. Mlinarić-Majerski;
    Publisher: Croatian Society of Chemical Engineers
    Country: Croatia

    Biological activity of different adamantane derivatives and their application has been described in various reviews. Similarly, many reviews deal with biological activity and application of guanidine compounds. However, up to now no review has been made concerning the guanidine derivatives of adamantane and other polycycles, compounds which incorporate both of these moieties in the same molecule. Therefore, a literature survey of polycyclic guanidine derivatives is here provided and their application as potential pharmacophores stressed. Biološka aktivnost različitih adamantanskih derivata i njihova primjena opisane su u brojnim preglednim člancima. Isto tako, mnogi revijalni članci opisuju biološku aktivnost i primjenu gvanidinskih spojeva. Međutim do sada nije načinjen pregled koji bi se bavio gvanidinskim derivatima adamantana i drugih policikla, tj. spojevima koji sadrže obje navedene podjedinice u istoj molekuli. U ovom radu bit će stoga dan pregled policikličkih derivata gvanidina, i to s naglaskom na njihovu primjenu kao potencijalnih farmakofora.

  • Open Access
    Authors: 
    Shulan Yu; Jialin Peng; Xinwen Zhang; Guoguang Wang;
    Publisher: Croatian Society of Chemical Engineers/HDKI

    It is of great challenge and significance to recycle activated carbon (AC), yet still with various problems in operation. Here, we have performed a simulation on the regeneration of AC by using an indirect heating method with an unsteady cylindrical heat transfer model. The result has shown that the optimal parameters for a regeneration tube of outer diameter Φ = 108 with wall thickness 4 mm were: heating in the tube for 30 min at a surrounding temperature of 550 °C. In these conditions, a temperature of 417.5 °C could be obtained at the centre of the cylindrical tube, reaching the temperature required for AC regeneration. The experimental values obtained in our laboratory were consistent with the simulation, providing significant references for scaling up pilot plant of AC regeneration.

  • Open Access English
    Authors: 
    Valdrin Beluli;
    Publisher: Croatian Society of Chemical Engineers
    Country: Croatia

    Gjilan (42˚28’08” V, 21˚27’48” L) is one of the seven largest cities in Kosovo. Throughout the city flow three rivers: Mirusha and Stanishor which mix and discharge into the largest river called Morava. The reason for the research of these rivers is the extreme pollution resulting from the discharge of industrial waters. Analysis of these rivers shows that they are extremely polluted and some physicochemical parameters are not in accordance with the regulations of the European Union (EU) and the World Health Organization (WHO). Parameters analysed are: pH, CW, NTU, DO, COD, BOD5, A-HCl, HCO3, GH, CS, Cl–, Cl2, Ca2+, Mg2+, NO2–, NO3–, PO43–, and NH3–. This work is licensed under a Creative Commons Attribution 4.0 International License. Grad Gjilan (42˚28’08”, V 21˚27’48” L) jedan je od sedam najvećih gradova na Kosovu. Kroz njega prolaze tri rijeke: Mirusha i Stanishor koje se miješaju i ulijevaju u najveću rijeku Moravu. Razlog za istraživanje tih rijeka je njihovo onečišćenje nastalo ispuštanjem industrijskih voda. Analiza tih rijeka pokazuje izrazito onečišćenje te neusklađenost nekih fizikalno-kemijskih parametara s propisima Europske unije (EU) i Svjetske zdravstvene organizacije (SZO). Analizirani su sljedeći parametri: pH, CW, NTU, DO, COD, BOD5, A-HCl, HCO3, GH, CS, Cl–, Cl2, Ca2+, Mg2+, NO2–, NO3–, PO43– i NH3–. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

  • Open Access English
    Authors: 
    Amina Yettou; Maamar Laidi; Abdelmadjid El Bey; Salah Hanini; Mohamed Hentabli; Omar Khaldi; Mihoub Abderrahim;
    Publisher: Croatian Society of Chemical Engineers
    Country: Croatia

    Cilj ovog rada bio je razviti tri metode temeljene na umjetnoj inteligenciji za modeliranje trostruke adsorpcije iona teških metala {Pb2+, Hg2+, Cd2+, Cu2+, Zn2+, Ni2+, Cr4+} na različitim adsorbatima {aktivni ugljen, kitozan, danski treset, treset Heilongjiang, ugljik glave suncokreta i ugljik stabljike suncokreta). Rezultati pokazuju da se regresija potpornih vektora (SVR) pokazala nešto boljom, preciznijom, stabilnijom i bržom od regresije potpornih vektora najmanjih kvadrata (LS-SVR) i umjetnih neuronskih mreža (ANN). Za procjenu kinetike trostrukog adsorpcijskog sustava višekomponentnog sustava preporučuje se model SVR. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna. The aim of this work was to develop three artificial intelligence-based methods to model the ternary adsorption of heavy metal ions {Pb2+, Hg2+, Cd2+, Cu2+, Zn2+, Ni2+, Cr4+} on different adsorbates {activated carbon, chitosan, Danish peat, Heilongjiang peat, carbon sunflower head, and carbon sunflower stem). Results show that support vector regression (SVR) performed slightly better, more accurate, stable, and more rapid than least-square support vector regression (LS-SVR) and artificial neural networks (ANN). The SVR model is highly recommended for estimating the ternary adsorption kinetics of a multicomponent system. This work is licensed under a Creative Commons Attribution 4.0 International License.

  • Publication . Other literature type . Article . 2016
    Open Access Croatian
    Authors: 
    Jelena Parlov Vuković;
    Country: Croatia

    U ovome preglednom radu opisane su najznačajnije i najčešće primjenjivane jednodimenzijske i dvodimenzijske tehnike NMR u analizi biodizela. Biodizel je ekološki prihvatljivo alternativno gorivo koje se sastoji od zasićenih i nezasićenih metilnih estera masnih kiselina. Budući da analiza kemijskog sastava i proučavanje svojstava biodizela i ostalih biogoriva analitičarima predstavlja izazov, sve više se razvijaju nove i učinkovitije analitičke metode. Spektroskopija NMR jedna je od takvih metoda koja može dati niz informacija o sastavu i strukturi biodizela. Nadalje, analiza spektara NMR pruža vrijedne podatke i o sirovinama iz kojih nastaje biodizel te o procesu esterifikacije. Isto tako primjenom tehnika 1H i 13C NMR može se odrediti sastav aditiva koji se dodaju za sprječavanje rasta mikroorganizama i sastav smjese acetilglicerola i sličnih nusproizvoda sinteze biodizela. U tu svrhu se osim spektara 1H i 13C analiziraju i spektri 31P. U radu su dani karakteristični spektri biodizela, dizela, biljnog ulja tretiranog vodikom te reprezentativan spektar jednog od uzoraka biocida snimljeni u Laboratoriju za spektroskopiju NMR u INA d. d.

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