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In this study, open cell 25 % antimony-lead alloy foams are fabricated for possible use to lighten thick plates of lead-acid batteries. A new inexpensive and simple variant of the salt replication process is developed and explored. Different morphology and shapes have been successfully obtained with “excess salt replication” method (abbreviated as ESR method). Best porosity of about 68 % is obtained with salt particles size of about 3 mm. SEM and EDXS investigation of the composite salt/antimony alloy before NaCl leaching revealed the presence of the lead oxides microfilm coating cell walls and becoming lead carbonates after salt removal. Uniaxial compressive behaviour of the resulting cellular materials is studied for foams with porosities between 45 % and 70 %, and salt grain size ranging between 2.5 and 5 mm. A higher plateau stress is reached compared to the results obtained in the literature working on the aluminium foams. The reproducibility of the process is proved along samples. This work is licensed under a Creative Commons Attribution 4.0 International License. U ovom istraživanju izrađene su otvorene ćelije od 25 % antimon-olovnih pjena za moguću primjenu u osvjetljavanju debelih ploča olovno-kiselih baterija. Razvijena je i istražena nova jeftina i jednostavna varijanta procesa repliciranja soli. Različite morfologije i oblici uspješno su dobiveni metodom “prekomjerne replikacije soli” (ESR metodom). Najbolja poroznost od oko 68 % dobivena je pri veličini čestica soli od oko 3 mm. SEM i EDXS ispitivanje kompozitne legure soli/antimona prije ispiranja s NaCl otkrilo je prisutnost mikrofilma olovnih oksida koji oblažu zidove ćelije i nakon uklanjanja soli postaju olovni karbonati. Jednoosno tlačno ponašanje dobivenih materijala ćelije proučava se za pjene s poroznošću između 45 % i 70 % i za veličine zrna soli između 2,5 i 5 mm. Postignuta je veća granica stlačivanja u usporedbi s rezultatima o aluminijskim pjenama dobivenim u literaturi. Ponovljivost postupka dokazana je na uzorcima. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

The teaching of the periodic system in the historical context has an advantage because students in this way comprehend more easily the basic chemical concepts, such as relative atomic mass, proton number, chemical element, elementary substance, equivalent and molar mass. The story of the periodic system also shows the following: (1) Before a key scientific discovery there is a long period of data collection and systematization, (2) Theories in chemistry must be based on experimental results and methods, (3) The advancement of science is also determined by the development of concepts, and (4) Scientific theories usually do not contradict but support each other. Therefore, the historical periodic system (based on relative atomic mass) is not obsolete, but complementary to the modern.

Liquid-liquid equilibria were experimentally investigated in systems in which the first component was aliphatic (n-hexane, n-heptane or i-octane) or aromatic hydrocarbon (toluene), the second component was pyridine or thiophene, and the third quasi-component was DES consisting of choline chloride and glycerol or choline chloride and ethylene glycol, at 25 °C and atmospheric pressure. The equilibria were successfully described by the NRTL and UNIQUAC models. The same models were successfully applied to describe the liquid-liquid equilibria in quasi-seven-component systems that comprised all the mentioned low molecular weight components and one DES. The restrictions of the models were discussed; it seems that the preference can be given to the UNIQUAC model. This work is licensed under a Creative Commons Attribution 4.0 International License. Eksperimentalno su istražene ravnoteže kapljevina-kapljevina u sustavima u kojem je prva komponenta alifatski (n-heksan, n-heptan odnosno i-oktan) ili aromatski ugljikovodik (toluen), druga komponenta je piridin ili tiofen, a treća kvazi-komponenta je DES koji se sastoji od kolin klorida i glicerola, odnosno kolin klorida i etilen-glikola, pri 25 °C i atmosferskom tlaku. Ravnoteže su uspješno opisane modelima NRTL i UNIQUAC. Isti su modeli uspješno primijenjeni i za opis ravnoteža kapljevina-kapljevina i u kvazi-sedmerokomponentnim sustavima koji uključuju sve navedene niskomolekulske komponente i jedan DES. Raspravljena su ograničenja modela; čini se da se prednost može dati modelu UNIQUAC. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

HAZOP (Hazard and Operability Analysis) is a method of safety analysis, which is widely used in chemical processes. The conventional methods for safety analysis consist of human based safety analysis and computer aid safety analysis. All of them are off-line and qualitative and it is difficult to carry out on-line safety analysis. On-line safety analysis based on scenario object model was proposed for chemical processes. The scenario object model was built using ontology, by which the safety information can be transferred, reused and shared effectively. Deviation degree and qualitative trend were added to the model. Based on the model and new inference algorithm, on-line safety analysis can be implemented for chemical processes. Once a fault or abnormal event occurs, the causes can be traced and the consequences can be predicted. At the same time, semi-quantitative safety analysis is carried out. The resolution can be improved and it can help the operators handle the problems in time and effectively. The method was used for safety analysis of a reactor process and the effectiveness of the method was proved. This work is licensed under a Creative Commons Attribution 4.0 International License. HAZOP (analiza opasnosti i operativnosti) metoda je sigurnosne analize koja se primjenjuje u kemijskim procesima. Konvencionalne metode za analizu sigurnosti mogu biti ljudske i računalne. Sve su to kvalitativne i off-line analize, a sigurnosnu on-line analizu teško je provesti. Za kemijske procese predložena je sigurnosna on-line analiza temeljena na scenarijskom objektnom modelu. Scenarijski objektni model izrađen je ontološki, čime se sigurnosne informacije mogu učinkovito prenijeti, ponovno upotrijebiti i dijeliti. Stupanj devijacije i kvalitativni trend pridodani su modelu. Na temelju modela i novog algoritma zaključivanja sigurnosna se on-line analiza može implementirati u kemijske procese. Kada se dogodi pogreška ili abnormalni događaj, mogu se pratiti uzroci i predvidjeti posljedice. Istodobno se provodi polukvantitativna sigurnosna analiza. Rješenje je moguće poboljšati i time omogućiti operaterima pravodobno i učinkovito rješavanje problema. Metoda je primijenjena za sigurnosnu analizu reaktorskog procesa te je dokazana njezina učinkovitost. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

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.

Blueberry contains many substances that are important to the human body and can prevent cardiovascular diseases, protect the retina, and soften blood vessels. Anthocyanin, which is extracted from blueberry, can activate the retina, strengthen vision, reduce serum cholesterol, triglyceride and high-density lipoprotein, and protect cell nucleus tissues from radical oxidation; hence, blueberry is of importance to scientists from different countries. In this study, anthocyanin was extracted and separated from blueberry using ethyl alcohol to investigate the effects of factors, such as ethyl alcohol volume ratio on anthocyanin extraction and separation technologies. The extracting solution was then purified using the macroreticular resin purification method to investigate the effects of ethyl alcohol concentration and eluent dosage on anthocyanin extraction during purification. The research results demonstrated that 60 % ethyl alcohol volume fraction, 1 : 10 mass ratio of solid to liquid, and 60 °C ultrasonic temperature were the best conditions for anthocyanin extraction. The best purification conditions were 95 % ethyl alcohol, which had been acidized by 0.3 % hydrochloric acid and 70 ml of eluent. This work provides a reference for the application of ethyl alcohol in anthocyanin extraction. This work is licensed under a Creative Commons Attribution 4.0 International License. Borovnica sadrži niz tvari koje su važne za ljudsko tijelo te mogu spriječiti kardiovaskularne bolesti, zaštititi mrežnicu i poboljšati stanje krvnih žila. Antocijanin, ekstrahiran iz borovnice, može aktivirati mrežnicu, ojačati vid, smanjiti serumski kolesterol, triglicerid i lipoprotein visoke gustoće te zaštititi tkivo stanica od radikalske oksidacije; dakle, borovnica je važna znanstvenicima diljem svijeta. Kako bi se istražili učinci čimbenika kao što je volumni omjer etilnog alkohola pri ekstrakciji antocijanina i tehnologija odvajanja, antocijanin je u ovoj studiji ekstrahiran i odvojen iz borovnice etanolom. Otopina za ekstrakciju je zatim pročišćena makroretikularnom smolom radi ispitivanja učinaka koncentracije etanola i doziranja eluenta na ekstrakciju antocijanina tijekom čišćenja. Rezultati istraživanja pokazali su da su volumni udjel etanola od 60 %, maseni omjer čvrste tvari i tekućine od 1 : 10 i ultrazvučna kupelj pri 60 °C najbolji uvjeti za ekstrakciju antocijanina. Najbolji uvjeti za pročišćavanje bili su 95 % etilnog alkohola koji je bio zakiseljen s 0,3 % klorovodične kiseline i 70 ml eluenta. Ovaj rad daje referenciju za primjenu etanola u ekstrakciji antocijanina. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

The 8-mm diameter bars of Cu-Al-Mn shape memory alloys were produced by continuous casting technique. The samples were characterised using optical microscopy and scanning electron microscopy along with EDX analysis. The continuous cast alloy revealed some martensitic phase, which, after quenching, led to the microstructure that is completely martensite. Quenching of samples had an effect on several mechanical properties and change in morphology of fracture. After ageing at 200 °C and 300 °C, the tensile strength increased and elongation drastically decreased. Morphology of fracture surface changed from primary ductile to a mixture of intergranular and ductile. This work is licensed under a Creative Commons Attribution 4.0 International License. Šipke promjera 8 mm proizvedene su iz legure Cu-Al-Mn s prisjetljivosti oblika tehnikom kontinuiranog lijevanja. Uzorci su karakterizirani pomoću optičke mikroskopije i pretražne elektronske mikroskopije uz analizu EDX. Kontinuirano lijevana legura je pokazala mjestimičnu prisutnost martenzitne faze, dok je nakon kaljenja nastala potpuno martenzitna mikrostruktura. Kaljenje uzoraka utjecalo je na mehanička svojstva i na promjenu morfologije prijeloma. Nakon starenja pri 200 °C i 300 °C porasla je vlačna čvrstoća a izduženje se drastično smanjilo. Morfologija prijelomne površine se mijenjala od duktilne do mješavine interkristalne i duktilne. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

Biodiesel is the first alternative fuel the physicochemical properties of which are regulated by appropriate standards: American ASTM D 6751 and European standard EN 14214. The process of biodiesel production consists of three main phases: 1) preparation of feedstock, 2) transesterification, and 3) processing of the reaction product – purification of crude biodiesel to meet the specification provided by the previously mentioned standards. The purification process of crude biodiesel is usually carried out by two notable techniques: wet and dry washing. The most commonly used process is wet washing. A major drawback in the use of water in purification process is the generation of a large amount of wastewater that greatly increases biodiesel production costs, followed by drying of the product, which requires an additional amount of energy and is time consuming. The greatest disadvantage of dry washing using different ion-exchange resins is the inability to remove glycerol and methanol from crude biodiesel to those limits prescribed by EN 14214, followed by the disposal problem of spent ion-exchange resins. Because of the aforementioned, the use of membrane technology in the process of biodiesel purification has appeared as an alternative for the existing purification techniques. The membrane filtration is environmentally friendly and requires less energy. By membrane filtration, the glycerol, methanol, and water contents in biodiesel can be decreased to the amounts prescribed by the standards. In the frame of this review article, the short overview of the possibility of using ultra- and/or micro-filtration in the purification process of biodiesel is presented.

Aerobic bioconversion is very interesting process for the mathematical modelling and optimisation from the aspect of improving and accelerating the process, which is reflected in a higher organic matter decomposition rate. The aim of this research was to estimate the kinetic parameters in a dynamic model that described aerobic biodegradation of organic fraction of municipal solid waste (OFMSW) with various additions, from an engineering aspect. The presented mathematical model based on heat and mass transfer phenomena is a dynamic model for the gas-liquid-solid system. For the optimization and process simulation, three experiments were performed in three geometrically identical reactor systems at the same time, with different initial composition of composting mixtures. Data obtained experimentally from one reactor were used to optimize kinetic parameters of the model, and data from the other two reactors were used to verify and evaluate the dynamic model. Detailed statistical analysis showed narrow values of 95 % confidence interval for estimated parameters, indicating the appropriate accuracy of parameter estimation. Better data agreement was achieved in the reactor with a smaller ratio of OFMSW and additives, and the most accurately predicted dynamic state variable was the mass of organic matter. Parameter sensitivity analysis showed that the most sensitive parameters were reaction order n and activation energy E. Overall, the application of this model with optimised kinetic parameters of the aerobic biodegradation process represents a tool to predict the most important process variables (SD = 0.3378). This work is licensed under a Creative Commons Attribution 4.0 International License. Postupak aerobne biorazgradnje zanimljiv je za numerička istraživanja da bi se postigla bolja učinkovitost postupka, što se odražava u većoj brzini razgradnje organske tvari. Cilj ovog istraživanja bio je procijeniti kinetičke parametre u dinamičkom modelu koji opisuje proces aerobne biorazgradnje organske frakcije komunalnog krutog otpada s različitim dodatcima s inženjerskog aspekta. Predstavljeni matematički model zasnovan na pojavama prijenosa topline i mase dinamički je model sustava plin–tekućina–krutina. U svrhu optimizacije i simulacije postupka izveden je jedan pokus u tri reaktorska sustava sa smjesama različitog početnog sastava. Eksperimentalni podatci dobiveni iz jednog reaktora upotrijebljeni su za procjenu kinetičkih parametara modela, a podatci iz preostala dva reaktora upotrijebljeni su za provjeru i procjenu dinamičkog modela koji izvodi simulaciju. Detaljna statistička analiza pokazala je uske vrijednosti 95 %-tnog intervala pouzdanosti, što ukazuje na odgovarajuću točnost procjene parametara. Bolje slaganje podataka postignuto je u reaktoru s manjim udjelom dodataka, a najpreciznije predviđena varijabla je konverzija organske tvari. Analiza osjetljivosti parametara pokazala je da su najosjetljiviji red reakcije n i energija aktivacije E. Sveukupno, primjena ovog modela s procijenjenim kinetičkim parametrima u aerobnom procesu biorazgradnje pruža alat za predviđanje najvažnijih procesnih varijabli (SD = 0,3378). Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

In this paper, the thermal ageing of nitrile-butadiene rubber (NBR) reinforced with different graphene (GE) concentrations has been investigated. NBR and NBR-GE composites were exposed to an accelerated thermal ageing environment produced by an air-circulating oven for seven days. The mechanical properties, chemical changes, and thermal stability of ageing samples and neat samples were evaluated. The results showed that the surface damage of NBR was severe and inhomogeneous, and the degree of ageing was most serious on the edge region of the voids, but NBR-GE composites were changed slightly before and after ageing. The tensile strength increased with the increase of GE concentration, up to a maximum value, and decreased with further increases in GE concentration. The GE embedded crosslinked network limited the segment movement of chains in the stretch direction and played a role in the composites properties, and the GE sheets (contained the functional groups of −OH, −C=O and C=C) after ageing. This behaviour may indicate greater interface adhesion between the GE and NBR. In addition, results obtained by thermogravimetric analysis (TGA) indicated that the thermal stability of NBR significantly changed with accelerated thermal ageing environment, but with addition of a certain amount of GE to NBR, the thermal stability of NBR could be improved. The NBR/GE composites exhibited good comprehensive performance with a mass fraction of GE of 10 %. Before and after the thermal ageing, the failure mechanism of NBR-GE composites appeared intergranular and ductile fracture, respectively. This work is licensed under a Creative Commons Attribution 4.0 International License. U ovom radu istraživano je toplinsko starenje nitril-butadienskog kaučuka (NBR) uz različite udjele grafena (GE). Kompoziti NBR i NBR-GE bili su izloženi ubrzanom toplinskom starenju koje je proizvodila zračna cirkulacijska pećnica tijekom sedam dana. Ispitivana su mehanička svojstva, kemijske promjene i toplinska stabilnost uzoraka starenja i čistih uzoraka. Rezultati su pokazali veliko i nehomogeno površinsko oštećenje NBR-a. Stupanj starenja bio je najozbiljniji na rubnom dijelu praznina, dok su se kompoziti NBR-GE prije i poslije starenja neznatno promijenili. S povećanjem koncentracije GE, vlačna čvrstoća se uvećala do maksimalne vrijednosti i smanjila s daljnjim povećanjem koncentracije GE. Ugrađena GE mreža ograničila je kretanje lanaca u smjeru rastezanja i odigrala ulogu u svojstvima kompozita i slojevima GE (sadržavali su funkcionalne skupine −OH, −C=O i C=C) nakon starenja. Ta pojava može ukazivati na veću međupovršinsku adheziju GE i NBR. Dodatno, rezultati dobiveni termogravimetrijskom analizom (TGA) pokazuju da se termička stabilnost NBR-a znatno promijenila s ubrzanim uvjetima toplinskog starenja, ali uz dodatak određene količine GE u NBR, može se poboljšati toplinska stabilnost NBR-a. Kompoziti NBR-GE pokazali su dobra sveobuhvatna svojstva s masenim udjelom GE od 10 %. Prije i nakon toplinskog starenja, mehanizam kvara kompozita NBR-GE pokazao je intergranularne i duktilne prijelome. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.