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Recently, more and more attention has been paid to the application of process intensification methodology, and accordingly, the possibility of applying additive manufacturing technology or 3D-printing to the manufacture of advanced versions of catalysts and chemical reactors using different materials is being studied. Considering that it is possible to create computer-optimized reactors using additive manufacturing techniques, it is easy to see the enormous potential this technique offers, especially on a laboratory scale. In this research, the analysis and modelling of a 3D-printed ceramic monolithic reactor fabricated by stereolithography was performed, while the deposition of the catalytically active layer was done using the wet impregnation technique. Their effectiveness was tested by the catalytic oxidation of BTEX compounds consisting of benzene (C6H6), toluene (C6H5CH3), ethylbenzene (C6H5CH2CH3), and xylene (C6H4(CH3)2). BTEX are aromatic hydrocarbons that occur in the environment as compounds naturally found in the oil. However, they are most commonly found in the atmosphere, where they can have harmful effects not only on the environment but also on living organisms and humans. A one-dimensional (1D) heterogeneous reactor model is proposed to model the reactor, which includes a kinetic model for the first-order reaction. The results obtained with the BTEX mixture and individual BTEX compounds were compared. The evaluation of the acceptability of the proposed model based on the corresponding values of the root of the standard deviation between the experimentally determined and the theoretically predicted values showed that the proposed model successfully describes the experimental results. Considering that the 1D heterogeneous model was derived based on the associated balances for model components in the gas phase and the balance for model components on the surface of the catalytic layer, which corresponds to the physical picture of the process, it was concluded that the proposed model is suitable for describing the catalytic oxidation of BTEX and similar aromatic volatile organic compounds using heterogeneously structured catalysts.

In chemical engineering, the term monolith refers to structures with clearly defined and invariable geometry. They are usually produced by extrusion (ceramic monoliths, usually made of synthetic cordierite) or by coiling and grooving (metal monoliths, usually made of stainless steel). In recent years, the possibility of 3D printing, i.e. additive manufacturing (AM), has been explored for various applications in the field of biotechnology and chemical sciences, but also in the field of catalytic reaction engineering as an advanced method to fabricate complex monolithic catalysts/reactors from different materials. In this work, stereolithography (SLA) was used to fabricate ceramic monolithic catalyst carriers for the preparation of potential monolithic catalysts for the catalytic oxidation of a benzene/toluene/ethylbenzene/o-xylene (BTEX) gaseous mixture. This approach involves the preparation of inert catalyst carriers, on the surface of which the catalytically active components are subsequently deposited using the impregnation technique. The prepared monolithic catalysts differed in the characteristic geometry of the channels, resulting in different geometric surface areas (11 cm2, 15 cm2, 20 cm2, and 22 cm2) of the monolithic catalysts. As catalyst precursors, 1 M aqueous solutions of manganese(II) nitrate tetrahydrate, copper(II) nitrate trihydrate, iron(III) nitrate nonahydrate, and nickel(II) nitrate hexahydrate were used. Two-component mixed oxides of manganese and transition metals (Fe, Cu and Ni) were used as catalytically active components. As expected, the conversion of the BTEX components increased with increasing temperature, and characteristic S-shaped curves (i.e., self-ignition curves) were obtained. The carrier with a geometric surface area of 22 cm2 proved to be the best, as expected, while in terms of the chemical composition of the catalyst, the best results were obtained with MnFeOx, followed by MnCuOx with very similar conversion values, and MnNiOx, which proved to be less catalytically active under the tested operating conditions.

In the field of chemical engineering, the term "monolith" refers to structures with clearly defined and invariable geometry. Monolithic structures typically serve as inert substrates or carriers of catalytically active components applied to such a structure by conventional methods for the preparation of heterogeneous catalysts. Increasing attention is being paid to the application of process intensification methodology, and, consequently, to the possibility of using additive manufacturing technologies (3D printing) to produce various catalysts from different materials, including ceramics [1, 2]. In this work, stereolithography (SLA) was used to fabricate ceramic monolithic catalyst carriers with different geometries for the production of novel monolithic catalysts for the catalytic oxidation of benzene/toluene/ethylbenzene/o-xylene (BTEX) gas mixture. For this purpose, a Form 2 3D printer (Formlabs) and commercially available ceramic resin (Formlabs) were used. 3D models of monolithic catalyst carriers of various geometries and surface areas (11, 15, 20, and 22 cm2) were created using Autodesk Fusion 360 and prepared for 3D printing using PreForm (Formlabs) slicer. The ceramic resin and heat-treated carriers were characterized in detail [3], while the catalysts used were previously characterized [4]. After heat treatment of the carriers, the precursors of the catalytically active components (Mn, Fe, Cu, and Ni) were applied in the form of 1 M aqueous solutions of nitrate salts using the impregnation technique. After application of the precursors, the carriers were calcined at 500 °C for 2 hours to form a stable layer of manganese mixed oxides, MnMOx (M = Fe, Cu, Ni). Adhesion tests were performed using ultrasound to test the mechanical stability of the catalyst layer. The test specimens were placed in a bottle containing petroleum ether and sonicated for 30 minutes. The test results showed excellent adhesion of the catalyst layer with mass losses below 2%. Catalytic oxidation of the gaseous BTEX mixture (Messer) was carried out in a reactor filled with a previously prepared monolithic ceramic catalyst. The gaseous BTEX mixture contained 50 ppm of benzene, toluene, ethylbenzene and o-xylene in nitrogen. Catalytic oxidation was carried out at atmospheric pressure, at various temperatures, and at constant total flow rate (92 ml/min) of the reaction mixture. As expected, the conversion of BTEX components increased with increasing temperature, and characteristic S-shaped curves were obtained. The carrier with a geometric surface area of 22 cm2 proved to be the most catalytically active. Regarding the chemical composition of the catalyst layer, the best results were obtained with MnFeOx, closely followed by MnCuOx, while MnNiOx showed the lowest catalytic activity under the operating conditions used. With the most active combination of 3D printed carrier (22 cm2) and mixed Mn oxides (MnFeOx), 90% conversion of benzene at 212 °C, toluene at 179 °C, ethylbenzene and o-xylene at 177 °C was achieved. Future work will focus on the development of catalyst carriers with more complex geometries, including the use of integrated static mixers, and a three-component catalyst (MnMOx, M=Fe, Cu) to further improve the BTEX conversions achieved.

Raman spectroscopy is optical resonance technique sensitive to atomic bonding. As such it is often used for catalyst characterization and for the investigation of the bulk and surface chemistry during catalyst use. Method is of considerable interest in situations when catalyst is not single-phase material, but consists of a mixture of crystal phases. Ideally, in such cases, Raman spectra in comparison with theoretical model would be indispensable tool for description of physicochemical properties of these complex structures including phase contacts. Modeling the Raman spectra, however, even at the level of density-functional theory proves to be rather computationally demanding. In the attempt to elucidate catalyst composition, and complement experimental findings (XRD, XPS, Raman spectroscopy) in our research of MnMOx catalysts, we begin by modeling separate crystal phases expected to be present in the multi-phase catalyst samples [1]. To some extent, the interfacial effects are accounted for by the finite size of the theoretically studied structures representing crystallites. Based on comparison of weighted superposed theoretical spectra of several crystal phases and experimental Raman spectra of the catalyst, we comment on the possibility to use such approach for determination of multi-phase catalyst composition and investigation of its properties.

A recent investigation of doped ceria catalyst, as well as advanced synthesis methods of ceria catalyst support will be presented. First, the optimization of the hydrothermal synthesis process in order to obtain as small crystallites as possible, as well as testing of the catalytic activity of the prepared nanocatalysts will be described. Then, the properties of ceria doped with various transition metal ions will be presented, after which the focus will be on ceria doped with manganese and copper, which have proven to be the most effective catalysts. Particularly, crystal phases and distribution of manganese, grain growth kinetics, properties and catalytic activity of manganese doped hydrothermally derived ceria, as well as doping levels, thermal stability, properties and catalytic activity of copper doped hydrothermally derived ceria will be presented. Other synthesis procedures such as sol- gel and mechanochemical synthesis will be also presented, as well as the use of doped ceria for other purposes such as UV filter, with focus on cell toxicity, and humidity sensing thin films. Finally, several possible directions of research in the field of synthesis, utilization and properties of ceria and doped ceria nanomaterials will be proposed.

The development of photocatalytic systems has led to great advances in environmental remediation and environmentally friendly energy production. Due to their high efficiency and potential to remove various priority pollutants, the focus of modern research is to overcome existing challenges, which include several key parameters, such as the distribution of radiation intensity, suitable modifications of photocatalysts to extend the range of their catalytic activity in the visible light region, the preparation of an immobilized layer of photocatalysts on a suitable substrate, the preparation of stable and efficient photocatalysts for use in real systems, etc. With rapid industrialization, the number of priority pollutants has increased significantly, so their removal from the environment requires the use of advanced oxidation processes as a promising technology. Acetamiprid (N-[(6-chloropyridin-3-yl)methyl]-N'- cyano-N-methylethanimidamide ; C10H11ClN4) is a commonly used neonicotinoid insecticide in practice due to its exceptional insecticidal activity, broad spectrum of activity, high stability and water solubility. However, due to its long half-life, it can accumulate in many plants and microorganisms, leading to adverse effects on human health (toxicity, carcinogenicity, mutagenicity). Therefore, it is extremely important to develop a reliable and effective technique for its removal from the environment. There are several types of photoreactors used for photocatalytic degradation of various persistent and toxic organic compounds in an aqueous medium. In this work, an advanced design of a photoreactor was used which was developed considering the basic methodology of process intensification. Photocatalytic degradation of acetamiprid was studied in a rotating photoreactor with recirculation of the reaction mixture using an immobilized layer of TiO2 photocatalyst. Two 15 W UV-A lamps were used as an external source for photoinduced excitation of the photocatalyst, and modified TiO2 was used as the photocatalyst. The modification of TiO2 was carried out to decrease its band gap energy and shift its photoactivity to the visible light region. The aim of the study was to determine the reactive oxygen radicals and to investigate the influence of some interfering compounds, crucial for the successful performance of the photocatalytic degradation of the selected model component. For this purpose, various scavengers were used that exhibit high reactivity with individual oxygen and other reactive species. Based on the determination of the change in concentration of the model component as a function of irradiation time, conclusions were drawn about the efficiency of photocatalytic degradation. The experimentally obtained results during photocatalytic degradation were tested with the adopted reactor and kinetic model, and the model parameters were estimated. The analysis of the obtained results showed that superoxide anion radicals and singlet oxygen play a crucial role in the photocatalytic degradation mechanism of acetamipride. In the presence of low concentrations of hydrogen peroxide, the efficiency improves, which is explained by the formation of additional superoxide anion radicals. In the presence of potassium persulfate, the degradation of acetamiprid is significantly improved due to the formation of sulfate radicals, which are extremely strong oxidants. Based on the obtained results, recommendations were made for future research to determine the role of reactive oxygen radicals, which are crucial for the successful performance of photocatalytic degradation.

Pollution of the environment, especially of the aquatic ecosystem, is one of the most serious problems today. Due to their high toxicity, strong bioaccumulation in the environment and high persistence, a relatively new group of insecticides - neonicotinoids - pose a serious threat to the ecosystem and the health of living organisms. Since conventional water treatment methods do not allow the complete removal of pesticides from polluted waters, a large amount of scientific research today is focused on the development of environmentally friendly and energy-efficient treatment methods. Heterogeneous photocatalysis is carried out in the presence of a solid semiconductor material and under the influence of sunlight as a radiation source. Due to its properties such as high photochemical stability, oxidative efficiency, availability and non-toxicity, the most commonly used photocatalyst is titanium dioxide (TiO2). Despite its many advantages, the high energy of the bandgap, i.e., the need for UV radiation for excitation, is a factor limiting the use of TiO2 in solar systems. In this work, photolytic and photocatalytic degradation of the neonicotinoid insecticide imidacloprid was investigated with Sun as a radiation source. Investigations were carried out in a plate photoreactor under recirculating reaction conditions with an immobilized photocatalyst (TiO2). To reduce the bandgap, TiO2 was modified by prior irradiation with UVC radiation. The experiments were performed at a constant initial reactant concentration (10 ppm) and at a constant pH of the reaction solution (pH = 6.5). The influence of the recirculation flow (50 - 300 cm3 min-1) and the surface area of the photocatalyst exposed to radiation on the rate of degradation of the model component was studied. The course of imidacloprid degradation was followed by high performance liquid chromatography (HPLC), while the degradation intermediates were identified by QTof analysis. The test results indicated the possibility of photocatalytic degradation of imidacloprid using Sun, a clean and alternative energy source, as a radiation source. In the presence of the prepared photocatalyst, the reaction rate is significantly increased. Higher conversions of imidacloprid were achieved at higher recirculation flows and larger surface area of the photocatalyst exposed to radiation.

The development of efficient and affordable catalysts for the removal of volatile organic compounds is a pressing issue in environmental protection. Strontium-doped lanthanum manganites, La1-xSrxMnO3 (LSMO) have potential as catalysts, since the level of doping influences both the Mn oxidation state and oxygen non-stoichiometry and thus redox properties and possible catalytic activity of LSMO [1]. LSMO catalysts (x = 0, 0.1, 0.2 and 0.3) were prepared by the citrate-nitrate autocombustion (CNA) and coprecipitation synthesis. Pure manganite phases of desired composition were obtained in all cases, as confirmed by energy dispersive spectroscopy, X-ray diffraction and Rietveld refinement analysis. Oxygen content as calculated from occupancy factors matched the one determined by Mohr's salt permanganate titration. Morphology and porosity of prepared catalysts were investigated by scanning electron microscopy and N2 adsorption/desorption analysis. It was observed that both synthesis methods yield catalysts of similar average pore size diameter and specific surface area, but the pore size distribution differed: CNA-prepared catalysts had a multimodal pore size distribution, while the coprecipitated ones had a single maximum at 4 nm. Furthermore, the LSMO catalysts prepared by the CNA synthesis were voluminous with a porous ‘sponge-like’ morphology, which is expected to allow a better exchange of reactants and products. Catalytic activity was tested on oxidation of BTEX (benzene, toluene, ethylbenzene and o-xylene) gas mixture in the temperature range 373 – 723 K. Catalysts prepared by the CNA method have shown a higher catalytic activity, reaching 100 % conversion in catalytic oxidation of all components except benzene. Temperatures required to reach 50 % conversion were 10 – 50 K higher for catalysts prepared by the coprecipitation method. Catalytic activity was further increased by Sr-doping, as the presence of Mn3+/Mn4+ mixed valences increased their reducibility [2]. Samples prepared by coprecipitation had higher oxygen deficiency, which would decrease their reducibility and thus their activity as oxidative catalysts. The catalytic activity of these samples could be improved by controlling their morphology and crystallite size. References: 1. A. Žužić et al., Open Ceram. 5 (2021) 100063. 2. E.G. Vrieland, J. Catal. 32 (1974) 415-428.

The aim of this study was to investigate the photolytic and photocatalytic degradation of neonicotinoids in an aqueous solution. Acetamiprid (ACE) and thiacloprid (TIA), two widely used insecticides, were used as model components. Experiments were performed in a flat-plate photoreactor under conditions of recirculation of the reaction mixture over an immobilized photocatalyst layer (TiO2 modified by urea) using two artificial lamps for simulation of solar irradiation (2.4% UVB and 12% UVA ; 300-700 nm). The catalyst used was characterized by XRD, UV/Vis-DRS, BET, SEM /EDX, and CHNS analysis. For most measurements, the reaction mixture was sonicated for 15 minutes immediately before charging the reactor. The study focused on the influence of the pH of the initial solution on the efficiency of photocatalytic and photolytic degradation. It was found that photocatalytic degradation of the two model components was most effective under acidic operating conditions, i.e., at pH 4.5, while photolysis resulted in their minimum degradation. It was also observed that pretreatment of the reaction mixture with ultrasound promoted photocatalytic degradation, while in the case of photolytic degradation, the application of ultrasound did not contribute to better degradation. Finally, photocatalytic degradation of TIA was found to be more successful than photodegradation of ACE under identical process conditions.

The term monolith in the technical sense refers to structures with well-defined and invariable geometry. Monoliths are mainly used as an inert substrate (carrier) for various catalytically active components that are subsequently deposited on their surface, but there are also numerous examples where monoliths are made directly from catalytically active material [1]. In the field of chemical engineering, the possibility of using additive manufacturing (AM) technology, i.e. 3D printing, as an advanced method of fabricating monolithic catalysts/reactors is being increasingly explored, especially at laboratory scale. The aim of this work was to prepare 3D printed monolithic ceramic catalysts for the catalytic oxidation of benzene, toluene, ethylbenzene, and o-xylene (BTEX). The first step was the 3D printing of ceramic catalyst carriers using stereolithography (SLA). Autodesk Fusion 360 was used to create a 3D model of the catalyst carrier, PreForm was used as a slicer to prepare the models for 3D printing, and the 3D printer used was Form 2 (Formlabs). The dimensions of the monolith were 4 cm in length and 7 mm in diameter to fit in the reactor system and for comparison with cordierite monoliths (with the same dimensions) used in our previous work [2]. A commercial photopolymer resin with ceramic particles, Ceramic resin (Formlabs), was used to fabricate the monoliths. After 3D printing, the monoliths were washed in isopropyl alcohol and heat-treated according to the manufacturer's instructions [3]. In our previous work, we investigated the preparation of ceramic catalyst carriers with the Ceramic resin and characterized them [4]. Most commercially available monolithic cordierite catalysts contain various noble metals (mostly Pt, Pd, and Rh) as catalytically active components deposited on their surface. Although noble metals have great catalytic activity, they are very expensive and prone to catalyst poisoning. Various compounds were investigated as potential replacements, and mixed manganese oxides were found to be a good substitute due to their low cost and resistance to poisoning, although their catalytic activity is not as high as that of noble metals. In this work, catalytically active components (MnCuOx oxides) were applied to the surface of the heat-treated monolith using the impregnation technique. 1M aqueous solutions of Mn(NO3)2 x 4 H2O and Cu(NO3)2 x 3H2O were used as catalyst precursors. A series of five 3D printed ceramic plates (2 cm x 1 cm x 2 mm) were used according to the same principle as 3D printing the monolith to determine the optimum impregnation time and to test the mechanical stability (adhesion) of the catalytic layer. The optimal impregnation time was determined (15 min), and the impregnated monolith was calcined at 500 °C for 2 h to fabricate a MnCuOx layer on its surface. Adhesion tests were performed using a laboratory ultrasonic bath (Elmasonic S 30 H) to investigate the stability of the catalyst layer before the monolith could be used in the reactor. The mass of the plates was weighed and compared before and after the use of ultrasound for 30 minutes at room conditions. It was found that the mass loss of the catalyst was < 2%, indicating good adhesion of the catalyst layer and that the fabricated monolith (Figure 1) can be used for catalytic oxidation of BTEX. Catalytic oxidation was carried out at atmospheric pressure, at different temperatures, and with a constant total flow rate of the reaction mixture (80 mL/min of BTEX components and 12 mL/min of synthetic air as an oxidant). As can be seen in Figure 2, the high activity of the monolithic catalyst was achieved. Benzene showed to be the most difficult BTEX component to oxidize due to its known stable structure. Benzene was completely oxidized (XA=100%) at 300 °C, toluene and o-xylene at 200 °C, and ethylbenzene at 190 °C.

In our previous work, different methods were used to modify the photocatalytic properties of TiO2- based photocatalysts and improve their performance for the degradation of imidacloprid as a representative of neonicotinoids [1]. This work aims to investigate the efficiency of reactive oxygen species (ROS) generated by TiO2-based photocatalysts. The identification and quantification of ROS is very important for understanding the photodegradation mechanism, improving the degradation efficiency as well as for practical application. Photocatalytic degradation of imidacloprid (10 ppm) was carried out using aqueous suspensions of different TiO2- based photocatalysts (0.08 g) in an 80 mL batch reactor equipped with a UVP Pen Ray lamp (UVA, =365 nm). The generation of hydroxyl radicals (OH●), singlet oxygen (1O2) and superoxide radicals (O2-●) formed by the UVA irradiation were determined using appropriate quenchers such as isopropanol, sodium azide and p-benzoquinone. To test the possibility that degradation occurs via direct oxidation of the adsorbed reactant molecules with holes (h+) in the valence band, additional experiments were performed using EDTA- Na2 as a hole scavenger. The effect of H2O2 addition in different concentrations on imidacloprid degradation was also investigated. Finally, to detect the presence of the short- living ROS in the aqueous medium, the electron paramagnetic resonance (EPR) spin-trap technique was employed using 5, 5-dimethyl-1-pyrroline-N- oxide (DMPO) as a scavenger reagent. The spectra were recorded under the UVA irradiation at different reaction times. Based on the results obtained, conclusions were drawn about the major ROS responsible for the efficient degradation of imidacloprid.

The preparation of monolithic catalysts with high activity and stability is crucial for the catalytic oxidation of aromatic volatile organic compounds (AVOCs). Monoliths are mainly used as inert carriers for various catalytically active components, which are subsequently deposited on the monolithic structure. This work aimed to examine the adhesion between 3D-printed ceramic (SiO2) catalyst carriers (plates) and the catalytically active layer (manganese based mixed oxides). Two methods, impregnation and sol-gel method, were chosen for the deposition of the catalyst layer on inert ceramic carriers (Figure 1). The mechanical stability, i.e. the adhesion of the catalytic layer to 3D-printed ceramic plates was tested by exposing the coated plates to the ultrasonic vibrations, i.e. by determining the difference in mass of individual plates before and after the exposure. Due to the low mass loss of the catalyst (

Air pollution is a problem that is attracting more and more attention and is at the center of numerous researches. Rapid industrialization and global development result in an increase in pollution, and volatile organic compounds are an example of large group of pollutants that are dangerous to human health and environment. Catalytic oxidation proved to be a promising process for the degradation of volatile organic compounds and one of the most efficient and economically acceptable processes for their decomposition. Catalysts for this application are generally divided into noble metals and metal oxides. Although noble metals, such as palladium and platinum, are more catalytically active than transition metal oxides, their use is limited due to their high cost and susceptibility to poisoning by chlorinated and sulphuric compounds that can be present in the polluted gas. The aim of this work is to develop monolithic catalysts for catalytic oxidation of aromatic volatile organic compounds. A gaseous mixture of benzene, toluene, ethylbenzene and o-xylene (BTEX) in nitrogen was used as a model component. Reactions were carried out in a monolithic reactor at different temperatures, with a constant initial concentration of reactants (BTEX) and a constant ratio of reactant and oxidant (synthetic air). Gaseous mixtures were analyzed on-line before and after reaction using gas chromatography. The work involves finding the optimal chemical composition of the catalytic layer on inert cordierite carrier, using different combinations of transition metals oxides (manganese with copper, iron and nickel) and palladium as a representative of noble metals. The prepared cordierite monolithic catalysts showed acceptable mechanical stability and high performance regarding oxidation of the mixture of aromatic compounds. High conversion values (>95 %) of all components of the mixture was achieved at a temperature around 200 ⁰C, depending on the chemical composition of the catalytic layer. A comparison with the activity of a commercial monolithic catalyst (Purelyst PH-304) was also performed and appropriate conclusions were drawn.

Velik problem današnjice predstavlja intenzivna uporaba pesticida koji onečišćuju tlo, površinske i podzemne vode. Cilj ovog rada je izučavanje fotokatalitičke razgradnje imidakloprida u modelnoj otpadnoj vodi na imobiliziranom sloju fotokatalizatora u uvjetima simuliranog i prirodnog Sunčevog zračenja. Imidakloprid je izabran kao predstavnik neonikotinoidnih insekticida koji predstavljaju sve veću opasnost za okoliš. Istraživanja su provedena u pločastom fotoreaktoru s recirkulacijom reakcijske smjese pri različitim radnim uvjetima (pH, protok recirkulacije, vrsta i intenzitet izvora zračenja). Da bi se aktivno radno područje komercijalno dostupnog TiO2 katalizatora pomaknulo u vidljiv dio spektra i poboljšala ekonomska učinkovitost izučavanog procesa primijenjeni su različiti postupci funkcionalizacije koji su uključivali predobradu praškastog fotokatalizatora uslijed izlaganja djelovanju UVC zračenja u vodenoj suspenziji (TiO2-UVC-S), predobradu imobiliziranog sloja TiO2 izravnim izlaganjem djelovanju UVC zračenja neposredno nakon pripreme takvoga sloja (TiO2-UVC-D), dopiranju TiO2 dušikom primjenom uree (TiO2-U) te predobradu hladnom plazmom dušika (TiO2-PL N2) odnosno argona (TiO2- PL Ar). Svi postupci rezultirali su smanjenjem širine zabranjene zone, Ebg. Najveće smanjenje Ebg postignuto je za uzorak modificiran hladnom plazmom u struji dušika (TiO2-PL N2). Usporedbom fotokatalitičke aktivnosti pripremljenih fotokatalizatora ustanovljeno je da TiO2-UVC-D, TiO2-UVC-S i TiO2-U pokazuju veću učinkovitost u odnosu na fotokatalizatore modificirane hladnom plazmom dušika i argona (TiO2-PL N2, TiO2-PL Ar). U nastavku istraživanja nađeno je da se optimalno područje pH vrijednosti pri fotorazgradnji imidakloprida na imobiliziranoj sloju TiO2-UVC-D nalazi između 5 i 7. Protok recirkulacije reakcijske smjese nije značajno utjecao na učinkovitost fotorazgradnje. Najveće smanjenje koncentracije imidakloprida pri uvjetima korištenim u ovom radu postignuto je u uvjetima prirodnog Sunčevog zračenja, što je objašnjeno s izmjerenim intenzitetima zračenja.

Cilj ovoga rada bio je razvoj keramičkog monolitnog katalizatora za katalitičku oksidaciju aromatskih hlapljivih organskih spojeva. Razvoj katalizatora uključivao je nanošenje katalitički aktivnih komponenata na inertne monolitne nosače, pri čemu je u prvom slučaju korišten komercijalni inertni monolitni nosač (kordijerit), a u drugom slučaju je tehnologijom 3D-ispisa ili aditivne proizvodnje pripremljen monolitni nosač primjenom postupka stereolitografije. U oba slučaja kao katalitički aktivna komponenta korišten je miješani oksid mangana i bakra. Istraživanja su provedena primjenom toluena kao pojedinačne modelne komponente i smjese organskih spojeva koja je sadržavala benzen, toluen, etilbenzen i ksilen (BTEX). Ustanovljeno je da se aditivna proizvodnja može uspješno primijeniti za pripremu monolitnih katalizatora za katalitičku oksidaciju hlapljivih organskih spojeva, te da se pripremljeni monolitni katalizatori mogu koristiti kao zamjena za skupe komercijalne katalizatore koji sadrže teško dostupne i skupe plemenite metale kao što su Pt i Pd.

Population growth and increasing food demand require a shift from traditional to modern and intensive agricultural production, leading to increased use of insecticides. Neonicotinoid insecticides, including imidacloprid, have been added to the European Commission’s expanded “Watch” list within the Water Framework Directive since 2018, due to confirmed risk and danger to the aquatic environment. In this work, photocatalytic degradation of imidacloprid was investigated using immobilized TiO2 and two UVA-LED modules as irradiation source. A suitable mineral binder and an abrasive material as a support were used to prepare a stable immobilized photocatalytic layer with acceptable mechanical properties. Surface functionalization of TiO2 with urea was carried out to reduce the energy band gap (Ebg) of TiO2 as confirmed by UV-Vis diffuse reflectance spectroscopy (DRS). The chemical and structural properties of the catalyst were investigated by X- ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX). Photolytic and photocatalytic experiments were performed in the flat-plate photoreactor in recirculated batch mode, equipped with two UVA-LED modules connected to a voltage source. The intensity of the radiation was changed by applying a different voltage to the module. Influences of different process parameters such as initial concentration of imidacloprid, irradiation intensity and pH were studied using response surface methodology (RSM). An experimental design was prepared using Design-Expert. The kinetic study was also carried out for imidacloprid photodegradation at optimum conditions. According to the results of the model, the predicted response values showed high agreement with the actual response values. Finally, the model was found to be suitable for the design conditions of the experiment.

In a recent unpublished research of catalytic activity of several MnMOx (M = Cu, Fe, Ni) metal-oxide catalysts the Reactive force field (ReaxFF) method has been shown to model well such processes. The investigation raised interest in developing parameters for calculation of mixed metal-oxide species, which were at the time non-existent. Here we present first and preliminary results of training the ReaxFF for the Mn-Fe-O-C interaction. The training set of 39 structures consisting of at minimum the Mn, Fe and O atoms, obtained in their crystal form from Materials Project database [1, 2]. Each step in parameter optimization has been done performing MD minimization of 5000 steps of 0.1 fs using the NVT/Berendsen thermostat. Parameters were optimized using the parabolic search as implemented in the original van Duin code [3] with some in-home modifications. First, optimization is performed at temperature of 1 K. Initial parameters are then re-optimized using the same training set at temperatures 300 K and 500 K. The force field is applied to the process of toluene adsorption/degradation on MnFeO3 catalyst. Results obtained show agreement to previous experimental expectations, although some remarks are given, since the presumed crystal structure of Mn1-xFexO3 may have major impact for such theoretical predictions.

Ovo enciklopedijsko poglavlje razmatra temeljne postavke i povijesni razvoj kemijskog inženjerstva kao tehničke znanosti koja se bavi istraživanjem i razvojem postupaka pretvorbe tvari i energije, kao i dimenzioniranjem, izvedbom i radom uređaja kojima se provode te pretvorbe, uvažavajući pritom osnovna načela održivoga razvoja.

U radu je dan osvrt na promociju sveučilišnog udžbenika "Modeliranje u kemijskom inženjerstvu" autora Zorana Gomzija i Želimira Kurtanjeka.

Neonicotinoid insecticides, including imidacloprid, thiacloprid, thiamethoxam, clothianidin and acetamiprid have been included in the extended "Watch" list of the European commission within the water framework directive since 2018, due to the confirmed risk and danger for the aquatic environment. Their removal from contaminated waste streams is one of the major challenges with regard to solving global environmental problems [1, 2]. The aim of this work was to develop modified TiO2 photocatalysts and innovative designs of photocatalytic reactors for the decomposition of neonicotinoid insecticides under conditions of simulated solar irradiation. In this study surface functionalization of TiO2 was performed to reduce the energy band gap (Ebg) of the TiO2 and to prepare a stable immobilized photocatalytic layer with acceptable mechanical and catalytic properties under different operating conditions. A flat-plate photoreactor equipped with two lamps was designed for degradation of imidacloprid, which was used as a representative of neonicotinoid insecticides. Physicochemical, morphological and mechanical properties of the prepared photocatalytic layers were determined and their photocatalytic activity for imidacloprid degradation was tested. A comparison of photolytic and photocatalytic degradation was performed using different radiation sources for simulation of the solar light. Photocatalytic decomposition under the visible part of the solar spectrum was carried out to reduce the investment costs of the process in the real system. It was concluded that different modification methods can be used to reduce the energy band gap (Ebg) of the TiO2, but this does not necessarily mean a better conversion of imidacloprid during its photocatalytic degradation. Nevertheless, some classical synthesis routes for surface functionalization of TiO2 followed by an additional post-functionalization showed great potential to improve TiO2 activity for photocatalytic decomposition of imidacloprid under the visible part of the solar spectrum.