In this paper, different metallic materials (alloys of Fe, Al, and Zn) were investigated as sacrificial anodes during electrocoagulation (EC) for the treatment of compost leachate. Taguchi’s L9 ...orthogonal array design was applied to investigate the four controllable factors (different metallic material, initial pH value, stirring speed, and contact time) on decrease of chemical oxygen demand (COD) and electrodes mass loss. COD decrease reached values in the range of 75.72–92.97 %. The Taguchi optimisation results showed that the most effective factor for decrease of COD is the duration of the experiment, while the electrode material was for electrodes mass loss. The zinc electrode showed the lowest potential for use in the EC process for treatment of compost leachate, while the Al and Fe electrodes could be used in an acid or slightly acidic environment. The following decreasing order of energy consumption was recorded: Zn > Al > Fe. The measured values of metal electrode mass loss exceeded the theoretical values calculated using Faraday’s law in EC experiments with Al electrodes, while in experiments with Fe and Zn electrodes, those differences were insignificant.
Disposable protective face masks, the most used personal protective tools during the Covid-19 pandemic, have become a serious environmental concern that needs urgent attention. In this study, ...disposable protective face masks were disassembled into their components and mechanically recycled through extrusion. Fourier transform infrared spectroscopy and scanning electron microscopy were employed to investigate the effect of recycling on the structure and morphology of the mask material. Microscopy revealed morphological differences among the layers of the mask. Differential scanning calorimetry and thermogravimetric analysis were used to characterise the thermal properties of the samples before and after recycling. Although the mechanical recycling process had minor effect on the thermal properties and stability of the mask material, thermal methods verified differences between the layers of the mask.
Jednokratne zaštitne maske (DPM), kao najčešće upotrebljavani alat tijekom SARS-Covid-19 pandemije, postale su ozbiljan ekološki problem koji je potrebno riješiti. U ovom radu jednokratne zaštitne maske razdvojene su na sastavne komponente i mehanički reciklirane ekstrudiranjem. Infracrvena spektroskopija s Fourierovom transformacijom i pretražna elektronska mikroskopija primijenjene su za određivanje utjecaja recikliranja na strukturu i morfologiju materijala maske. Mikroskopija je ukazala na postojanje morfoloških razlika između slojeva maske. Toplinska svojstva istraživanih uzoraka prije i poslije recikliranja karakterizirane su primjenom diferencijalne pretražne kalorimetrije i termogravimetrijske analize. Iako su toplinske metode analize potvrdile razliku između slojeva maske, može se zaključiti da mehaničko recikliranje nije znatno utjecalo na toplinska svojstva i toplinsku stabilnost materijala maske.
In a previous study, the larger size of synthetic zeolite particles was highlighted as better choice for electrocoagulation combined with zeolite (ECZ). This choice resulted in a smaller rise in pH ...and temperature, a more significant decline in turbidity as well as chemical oxygen demand (COD), and lower electrode wastage, but with greater damage to the electrode surface. The focus of this study was to determine whether natural zeolite of three different particle sizes has the same effect on the ECZ process. The Taguchi method L9 was employed in planning the experiments, with particle sizes of natural zeolite ranging up to 600 μm, three different electrode materials (carbon steel, aluminium alloy, and sacrificial zinc anode), current density in the range of 0.003–0.018 A cm –2 , and contact time in the range 10–30 min. The Taguchi optimisation results revealed a more significant decrease in COD and turbidity with the smallest particle size of natural zeolite used (90 µm) and with Al electrodes. Evidently, the zeolite particle size, together with the zeolite composition, had a significant influence on the reduction in COD and turbidity. Anode consumption ranged from 0.0172 to 0.6469 g, with minor cathode consumption evident on all electrode materials. Optical microscopy analysis indicated significant corrosion of the anodes, particularly with the largest natural zeolite particle size of 160–600 µm, while minor corrosion damage was also observed on the cathodes.
Prethodno istraživanje istaknulo je veće čestice sintetskog zeolita kao bolji izbor za provedbu hibridnog procesa elektrokoagulacije kombinirane sa zeolitom (EKZ), budući da rezultira manjim porastom pH i temperature, znatnijim smanjenjem kemijske potrošnje kisika (KPK) i mutnoće, manjom potrošnjom elektroda, no uz veće oštećenje površine elektrode. Cilj ovog rada je ispitati pokazuje li prirodni zeolit triju različitih veličina čestica isti učinak na EKZ proces. Eksperimenti su planirani prema L9 Taguchi metodi, s veličinama čestica prirodnog zeolita do najviše 600 μm, trima različitim materijalima elektroda (ugljični čelik, aluminijske legure i žrtvene cinkove anode), gustoćom struje u rasponu 0,003 – 0,018 A cm –2 te kontaktnim vremenom u rasponu 10 – 30 min. Rezultati Taguchi optimizacije pokazuju znatnije smanjenje KPK i mutnoće primjenom čestica prirodnog zeolita manjih od 90 µm i Al elektrode. Očigledno je da veličina čestica zeolita, kao i sastav zeolita, znatno utječe na smanjenje KPK i mutnoće. Potrošnja anode je u rasponu 0,0172 – 0,6469 g, dok je manja potrošnja katode također uočena na svim materijalima. Analiza optičkim mikroskopom pokazuje značajnu koroziju anoda, a koje su više oštećene s najvećim česticama prirodnog zeolita (160 – 600 µm), dok su manja korozijska oštećenja uočena i na katodama.
In this research, nickel oxide (NiO) nanoparticles with different concentrations of 1, 2, 3, and 4 wt% were added to a zinc-rich ethyl silicate (ZRES) coating containing 90 wt% zinc dust particles to ...promote the cathodic and barrier performance of coating systems. FTIR, XRD, and EDX analysis indicated the chemical composition and created bonds in ZRES coatings. SEM, AFM and TEM images showed the surface roughness and particle size in ZRES structure. Also, TEM confirmed the uniform dispersion of NiO nanoparticles in the coating matrix loaded with 3 wt% NiO particles. The effect of NiO content and the anticorrosion behavior of nanocomposite coatings were investigated by different techniques, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and salt spray tests. Results revealed that ZRES coatings containing 3 wt% NiO nanoparticles had boosted sacrificial anode and barrier protection during 120 days of immersion in a 3.5 wt% NaCl solution. The addition of 3 wt% NiO into the coating system significantly reduced corrosion products and blisters while increasing corrosion resistances from 3069 Ω cm2 to 16482 Ω cm2 compared with the control ZRES sample. This high-performance anticorrosion behavior of the nanocomposite coatings is mostly due to the NiO nanoparticles, which have the capability to moderate the zinc dissolution rate in addition to improving the barrier by filling porosity and creating tortuous paths.
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•A zinc-rich ethyl silicate coating was modified by nickel oxide nanoparticles.•FTIR, XRD, and EDX analysis indicated the chemical composition and created bonds of zinc rich silicate coatings.•SEM, AFM and TEM analysis showed the surface roughness and particle size in ZRES structure.•EIS, OCP, PDP and salt spray tests clarified the anticorrosion behavior of the modified ZRES coatings with Nano NiO.•Nano NiO improved the barrier property and cathodic protection ability of the ZRES coating especially with 3 %w addition.
U ovom pregledu prikazan je dio znanstvenih istraživanja pri razvoju legura s prisjetljivošću oblika (engl. Shape Memory Alloy, SMA) na bazi bakra na Metalurškom fakultetu Sveučilišta u Zagrebu u ...razdoblju od 2006. do 2022. godine u suradnji s brojnim visokoškolskim i znanstvenim institucijama u regiji. Istraživane su sljedeće legure SMA: CuAlNi, CuAlMn, itd. Provedeno je fizikalno modeliranje uključujući numeričku simulaciju razvoja mikrostrukture i toplinsku analizu tih legura. Legure SMA rađene su u lučnoj, visokofrekventnoj i indukcijskim pećima pomoću tri različite tehnologije lijevanja: brzo skrućivanje, lijevanje u metalne i/ili grafitne kokile te kontinuirano lijevanje u šipke. Nakon toga odabrane legure su toplo i hladno valjane. Provedena je toplinska obrada (austenitizacija uz naknadno gašenje u vodi i žarenje) i karakterizacija funkcionalnih svojstava legura SMA u različitim stanjima. Za karakterizaciju, osim ispitivanja mehaničkih svojstava, primijenjene su brojne visokosofisticirane metode: optička mikroskopija (OM), pretražna (SEM) i transmisijska elektronska mikroskopija (TEM), energetsko disperzijska-spektroskopija (EDS), pretražna diferencijalna kalorimetrija (DSC), dinamičko-mehanička analiza (DMA), rendgenska difrakcija (XRD), elektrokemijska impedancijska spektroskopija (EIS) itd. Već pri lijevanju kod pojedinih legura SMA, a posebice nakon toplinske obrade austenitizacijom uz naknadno gašenje u vodi, utvrđena je martenzitna mikrostruktura koja je osnovni preduvjet za svojstvo prisjetljivosti oblika. Na temelju provedenih istraživanja po većini parametara (plastičnost, korozijska otpornost itd.) može se zaključiti da su se najbolje pokazale legure CuAlMn.
Kao rezultat provedenih istraživanja na legurama SMA, prema podatcima iz baze CROSBI (na dan 23. prosinca 2022.), istraživački tim objavio je 33 rada u časopisima (od kojih su 23 rada u časopisima indeksiranim u bazi podataka Web of Science), 74 rada u zbornicima međunarodnih konferencija, 18 sažetaka u zbornicima konferencija te pet ostalih radova. Također, obranjena je jedna doktorska disertacija te je izrađeno i obranjeno 12 završnih i 25 diplomskih radova u području tehničkih znanosti iz znanstvenih polja metalurgije i kemijskog inženjerstva.
U ovom radu istražen je utjecaj komercijalnog inhibitora (Chemtec FI30) na proces korozije ugljičnog čelika P235 u različitim vodenim otopinama; demineraliziranoj i/ili vodovodnoj vodi uz dodatak ...komercijalnog biocida (Chemtec BI01). Istraživanja su provedena gravimetrijskom metodom i elektrokemijskim metodama, dok je površina ispitivanog materijala analizirana pomoću optičkog mikroskopa. Analize pokazuju da inhibitor smanjuje brzinu korozije ugljičnog čelika u ispitivanim otopinama, ima visoku djelotvornost te da se može svrstati u anodne inhibitore. Također, uočeno je da inhibitor smanjuje opću i jamičastu koroziju ugljičnog čelika u korozivnim vodenim otopinama.
The effect of a commercial inhibitor (Chemtec FI30) on the corrosion of P235 carbon steel in water (demineralised and/or tap water) with the addition of a commercial biocide (Chemtec BI01) was studied in the present work. This study was carried out by weight loss and electrochemical methods, while specimen’s surface was examined using optical microscope.
Results obtained from gravimetric measurement revealed that P235 carbon steel corroded in aqueous solution,
i.e.
, in a solution of demineralised and tap water (50 : 50) and a biocide (Fig. 1), and in tap water with a biocide (Fig. 5). By analysing the surface of carbon steel with an optical microscope, general and pitting corrosion was observed, which was more pronounced in tap water with biocide (Figs. 2 and 6). The addition of a commercial inhibitor significantly reduced the occurrence of corrosion damage on the surface of carbon steel (Figs. 3, 4, 7, and 8) and decreased the rate of carbon steel corrosion in all aqueous solutions (Table 1).
Electrochemical investigations performed by open circuit potential measurement, linear polarisation and potentiodynamic polarisation measurement showed that the inhibitor Chemtec FI03 shifted the potential to more positive values (Figs. 9 and 10), increased polarisation resistance (Table 3), decreased the rate of carbon steel corrosion, and had high efficiency in all tested solutions (Table 4).
The results obtained showed that this commercial inhibitor could be used as an effective inhibitor for the corrosion of carbon steel in aqueous media.
This study investigates the changes at the electrodes and in the solution during crystal violet dye removal by electrocoagulation at different current densities (0.016, 0.024, and 0.032 A cm –2 ) and ...initial pH values (3.2, 5.5, and 7.0). The electrocoagulation process, which lasted 50 min, revealed changes in pH, temperature, electrical conductivity, and concentration of the crystal violet dye in the solution. The results demonstrate complete removal of crystal violet dye at the highest current density (achieved after 40 min) and an initial pH of 5.5 (complete removal after 30 min). During the electrocoagulation process, both the anodic and cathodic electrode materials were consumed. The consumption of electrode material increased with higher current density and solution pH, the influence of current density being more pronounced. Examination of the electrode surfaces under a light microscope revealed that the anodes dissolved uniformly and locally during the electrocoagulation process, while the cathodes mostly underwent uniform corrosion.
Promatrane su promjene na elektrodama i u otopini tijekom uklanjanja kristalno ljubičaste ( crystal violet ) boje elektrokoagulacijom, izvedene pri različitim početnim gustoćama struje (0,016, 0,024 i 0,032 A cm –2 ) i početnim pH (3,2, 5,5 i 7,0). Tijekom procesa elektrokoagulacije, koji je trajao 50 min, uočene su promjene pH, temperature, električne vodljivosti i koncentracije kristalno ljubičaste boje u otopini. Dobiveni rezultati istaknuli su ukupno uklanjanje kristalno ljubičaste boje pri najvećoj gustoći struje (potpuno uklanjanje nakon 40 min) i pri početnom pH od 5,5 (potpuno uklanjanje nakon 30 min). Materijal anodne i katodne elektrode troši se tijekom procesa elektrokoagulacije. Potrošnja elektrodnog materijala raste s porastom gustoće struje i pH otopine, pri čemu je utjecaj gustoće struje sve izraženiji. Izgled površina elektroda (snimljen svjetlosnim mikroskopom) pokazuje da se anode otapaju ravnomjerrno i lokalno tijekom procesa elektrokoagulacije, dok su katode uglavnom podložne ravnomjernoj koroziji.
Natural zeolites are well-known materials widely applied in the environmental remediation treatment process. However, the integration of various treatment methods is exceedingly investigated for ...achieving satisfactory effluent quality. In this paper, the integration of electrocoagulation and natural zeolite was evaluated in the treatment of biowaste compost leachate in a single step. The influence of different distances of electrodes (1.5, 3, and 4.5 cm), stirring speed (70, 200, and 400 rpm), the addition of natural zeolite and electrolyte NaCl on the efficiency of treatment of biowaste compost leachate has been carried out. Process efficiency was evaluated by measuring the change of pH value, electrical conductivity, temperature, turbidity, chemical oxygen demand (COD), total Kjeldahl nitrogen (TNK), total solids, and sludge settling test. The Taguchi method was applied to optimize biowaste compost leachate treatment. Experiments are planned according to Taguchi’s L8 (24 41) orthogonal array. The stirring speed, electrode distance, electrolyte and zeolite addition, solution initial pH adjustment were chosen as controllable factors, and their impact on COD, turbidity, TNK, settling rate, and electrode consumption were studied. Results show that optimal conditions depend on the parameter of interest and that optimal values for a particular parameter are not always the optimum if the desired goal is considered.
Service-learning represents an innovative pedagogy that integrates academic learning with community service to address environmental issues based on experiential learning principles. This innovative ...pedagogy enhances higher education learning outcomes by fostering active engagement, real-world context, interdisciplinary insight, skills development, and civic engagement among students. The merging of service-learning contributes to a profound understanding of the subject matter, its practical applications, and personal and professional growth. This paper provides an overview of the implementation of service-learning in the STEM field, with a primary focus on the decade-long involvement of the Faculty of Chemistry and Technology in environmental protection projects. Through collaboration with the non-governmental organisation Sunce and partners from the University of Split, this initiative, led by environmental experts, has introduced a novel approach to higher education, facilitating knowledge expansion, skill improvement, and expertise development for both students and academic staff. The impact has been substantial, with the University of Split attaining the 21st position globally on the “World Universities with Real Impact” list for ethics in 2021, largely attributable to these service-learning projects. Service-learning has been integrated into the SEA-EU initiative, furthering its development at the University of Split, and establishing it as a pioneer in this field. Institutionalising service-learning in higher education requires the establishment of dedicated courses, integration into existing programmes, and the allocation of resources for academic staff, community partners, and students. Successful implementation requires a collaborative, iterative process involving careful planning, preparation, and assessment, ensuring that students benefit from meaningful opportunities to apply course content to real-world challenges while positively impacting the community.
Društveno-korisno učenje (DKU) je obrazovni pristup koji spaja akademsko učenje s korisnim radom u zajednici da bi se riješili problemi okoliša utemeljeni na principima iskustvenog učenja. Taj inovativni pristup poboljšava ishode učenja u visokom obrazovanju nudeći studentima aktivan angažman, kontekst stvarnog svijeta, interdisciplinarne uvide, razvoj vještina i uključenost građana. Uključivanje DKU-a potiče dublje razumijevanje materijala kolegija, njegove praktične primjene te osobni i profesionalni rast. Ovaj rad daje pregled implementacije DKU učenja u STEM području, uglavnom se fokusirajući na desetljetnu uključenost Kemijsko-tehnološkog fakulteta u projekte zaštite okoliša. Suradnjom Udruge za zaštitu prirode i okoliša Sunce s partnerima sa Sveučilišta u Splitu, ova inicijativa, koju vode stručnjaci za okoliš, uvela je nov pristup visokom obrazovanju. Omogućila je studentima, nastavnicima i suradnicima da prošire svoja znanja, unaprijede svoje vještine i razviju stručnost. Utjecaj je bio znatan, a Sveučilište u Splitu zauzelo je 21. mjesto u svijetu na popisu “Svjetska sveučilišta sa stvarnim utjecajem” u kategoriji etike u 2021., uglavnom zahvaljujući DKU projektima. DKU je integriran u inicijativu SEA-EU i nastavlja se razvijati na Sveučilištu u Splitu, postavši predvodnik u tom području. Institucionalizacija DKU-a unutar visokog obrazovanja zahtijeva razvijanje DKU kolegija, integraciju DKU-a u postojeće programe i osiguravanje resursa za nastavno osoblje, partnere u zajednici i studente. Uspješna implementacija zahtijeva kolaborativni, iterativni proces koji uključuje pažljivo planiranje, pripremu i evaluaciju. Taj pristup osigurava studentima smislene prilike za primjenu sadržaja kolegija na izazove iz stvarnog svijeta, a istodobno pozitivno utječu na zajednicu.
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