Browsing by Author "Černík, Miroslav"
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- ItemA new method for assessment of the sludge disintegration degree with the use of differential centrifugal sedimentation(TAYLOR & FRANCIS LTD, 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND, 2019) Silvestri, Daniele; Waclawek, Stanislaw; Goncukova, Zuzanna; Thekkae Padil, Vinod Vellora; Grubel, Klaudiusz; Černík, MiroslavA novel method for assessing the disintegration degree (DD) of waste activated sludge (WAS) with the use of differential centrifugal sedimentation method (DCS) was shown herein. The method was validated for a WAS sample at four levels of disintegration in the range of 14.4-82.6% corresponding to the median particle size range of 8.5-1.6 mu m. From the several sludge disintegration methods used (i.e. microwave, alkalization, ultrasounds and peroxydisulfate activated by ultrasounds), the activated peroxydisulfate disintegration resulted in the greatest DD 83% and the smallest median particle size of WAS. Particle size distribution of pretreated sludge, measured by DCS, was in a negative correlation with the DD, determined from soluble chemical oxygen demand (SCOD; determination coefficient of 0.995). Based on the obtained results, it may be concluded that the DCS analysis can approximate the WAS disintegration degree.
- ItemA Polymeric Composite Material (rGO/PANI) for Acid Blue 129 Adsorption(MDPI, 2020-05-03) Kukulski, Tomasz; Wacławek, Stanisław; Silvestri, Daniele; Krawczyk, Kamil; Padil, Vinod V. T.; Fryczkowski, Ryszard; Janicki, Jarosław; Černík, MiroslavOver the years, polyaniline (PANI) has received enormous attention due to its unique properties. Herein, it was chosen to develop a new polymeric composite material: reduced graphene oxide/polyaniline (rGO/PANI). The composite was prepared by a simple and cost-effective fabrication method of formation by mixing and sonication in various conditions. The obtained materials were characterized and identified using various techniques such as scanning electron microscopy (SEM), Raman and ATR–FTIR spectroscopy, and X-ray diffraction (XRD). The objective of the paper was to confirm its applicability for the removal of contaminants from water. Water could be contaminated by various types of pollutants, e.g., inorganics, heavy metals, and many other industrial compounds, including dyes. We confirmed that the Acid Blue 129 dyes can be substantially removed through adsorption on prepared rGO/PANI. The adsorption kinetic data were modeled using the pseudo-first-order and pseudo-second-order models and the adsorption isotherm model was identified.
- ItemBioplastic Fibers from Gum Arabic for Greener Food Wrapping Applications(AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA, 2019-03-18) Padil, Vinod V. T.; Senan, Chandra; Waclawek, Stanislaw; Černík, Miroslav; Agarwal, Seema; Varma, Rajender S.The fabrication of bioplastic fibers from gum arabic (GA), a natural tree gum exudate, is described via the electrospinning method. The enrichment in surface properties of this bioplastic fiber was evaluated by methane plasma and gamma-ray irradiation treatments. The fibers with their modified forms, both treated and untreated, were investigated by various characterization techniques such as scanning electron microscopy, atomic force microscopy, X-ay diffraction and attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, BET surface area, water contact angle, and tensile strength measurements. A switchable hydrophobic/hydrophilic functionality on GA bioplastic fibers was established through CH4 plasma and gamma-ray irradiation treatments; higher water contact angle (130 degrees) was observed in GA bioplastic fibers that had undergone methane plasma treatment. However, the untreated and gamma-ray-irradiated GA bioplastics exhibited hydrophilic behavior. The comparative properties such as water resistance, antioxidant potency, gas barrier attributes, antibacterial effectiveness, biodegradability and food contact migration through the GA bioplastic fibers (untreated, plasma treated, and gamma-ray-irradiated) were assessed. The present work, in contrast to other existing bioplastic fibers, has the potential of becoming a viable option in greener food packaging as well as in environmental and medically related products based on tree gums.
- ItemChemical oxidation and reduction of hexachlorocyclohexanes: A review(2019) Waclawek, Stanislaw; Silvestri, Daniele; Hrabák, Pavel; Padil, Vinod V. T.; Torres-Mendieta, Rafael; Waclawek, Maria; Černík, Miroslav; Dionysiou, Dionysios D.Lindane (gamma-hexachlorocyclohexane) and its isomers (HCH) are some of the most common and most easily detected organochlorine pesticides in the environment. The widespread distribution of lindane is due to its use as an insecticide, accompanied by its persistence and bioaccumulation, whereas HCH were disposed of as waste in unmanaged landfills. Unfortunately, certain HCH (especially the most reactive ones: gamma- and alpha-HCH) are harmful to the central nervous system and to reproductive and endocrine systems, therefore development of suitable remediation methods is needed to remove them from contaminated soil and water. This paper provides a short history of the use of lindane and a description of the properties of HCH, as well as their determination methods. The main focus of the paper, however, is a review of oxidative and reductive treatment methods. Although these methods of HCH remediation are popular, there are no review papers summarising their principles, history, advantages and disadvantages. Furthermore, recent advances in the chemical treatment of HCH are discussed and risks concerning these processes are given.
- ItemCombination of nZVI and DC for the in-situ remediation of chlorinated ethenes: An environmental and economic case study(PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND, 2020-04) Černíková, Martina; Nosek, Jaroslav; Černík, MiroslavOver the past two decades, the use of nanoscale zero-valent iron (nZVI) has emerged as a standard method of contaminated groundwater remediation. The effectiveness of this method depends on key intrinsic hydrogeological parameters, which can affect both reactivity of the nanoparticles and their migration in the aquifer. In the case of low hydraulic permeability, the migration of nanoparticles is limited, which negatively influences remediation. An application of nZVI reinforced with a DC electric field led to a significant increase in the efficiency of remediation, as demonstrated by long-term monitoring at a former industrial site in Horice (Czech Republic). For the method testing, a 12 x 9 m polygon was defined around well 154, where the original contamination was predominantly composed of DCE (7300 mu g/l), and with a total concentration of chlorinated ethenes of 8880 mu g/l. During the first stage of the activities, 49 kg of nZVI was injected and monitored for two years. Subsequently, the electrodes were installed, and for three years, the synergistic action of nZVI within an applied DC field was monitored. Based on 32 monitoring campaigns performed over the six years, the combined method was compared with an application of the only nZVI in technical, environmental and economic terms. Technically, the method requires annual reinstallation of anodes as a result of their oxidative disintegration. Environmentally, the method provides significantly improved chlorinated ethane reduction, remediation of low permeable zones, and extended efficiency. Economically, the method is five times cheaper when compared to the nZVI used alone.
- ItemCombining nanoscale zero-valent iron with electrokinetic treatment for remediation of chlorinated ethenes and promoting biodegradation: A long-term field study(PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND, 2020) Czinnerová, Marie; Voluščuková, Ondřejka; Marková, Kristýna; Ševců, Alena; Černík, Miroslav; Nosek, JaroslavNanoscale zero-valent iron (nZVI) is recognized as a powerful tool for the remediation of groundwater contaminated by chlorinated ethenes (CEs). This long-term field study explored nZVI-driven degradation of CEs supported by electrokinetic (EK) treatment, which positively affects nZVI longevity and migration, and its impact on indigenous bacteria. In particular, the impact of combined nZVI-EK treatment on organohalide-respiring bacteria, ethenotrophs and methanotrophs (all capable of CE degradation) was assessed using molecular genetic markers detecting Dehalococcoides spp., Desulfitobacterium spp., the reductive dehalogenase genes vcrA and bvcA and ethenotroph and methanotroph functional genes. The remediation treatment resulted in a rapid decrease of the major pollutant cis-1,2-dichloroethene (cDCE) by 75% in the affected area, followed by an increase in CE degradation products methane, ethane and ethene. The newly established geochemical conditions in the treated aquifer not only promoted growth of organohalide-respiring bacteria but also allowed for the concurrent presence of vinyl chloride- and cDCE-oxidizing methanotrophs and (especially) ethenotrophs, which proliferated preferentially in the vicinity of an anode where low levels of oxygen were produced. The nZVI treatment resulted in a temporary negative impact on indigenous bacteria in the application well close to the cathode; but even there, the microbiome was restored within 15 days. The nZVI-EK treatment proved highly effective in reducing CE contamination and creating a suitable environment for subsequent biodegradation by changing groundwater conditions, promoting transport of nutrients and improving CE availability to soil and groundwater bacteria.
- ItemCorporate Social Responsibility of Companies Producing PFOA Containing Waxes for Cross-Country Skiing(MDPI, 2020-06-24) Švermová, Pavla; Černík, MiroslavThe chemical industry is a particularly sensitive sector that very often works with toxic, harmful and dangerous substances. This paper offers insight into the corporate socially responsible (CSR) behaviour of a specific segment of the chemical industry—the production of fluorinated ski waxes. Perfluorinated compounds, which excel in water and fat stability and repellency, are nowadays considered as harmful to human health and nature. During 2020, the basic compound, perfluorooctanoic acid (PFOA), will be banned, and finding its replacement will be a difficult task. So far, there are no alternatives in terms of environmentally friendly compounds that can maintain the desired properties of extreme ski glide. Based on a questionnaire distributed to twenty wax producers worldwide, we have concluded that, although the attitudes of companies towards CSR certification was rather negative (87.5%), and companies had not developed or documented any CSR policy/strategy with specific goals, they found CSR activities/instruments beneficial and important. The survey highlighted the fact that companies were aware that their products are dangerous for the environment, and that environmental issues are important for all of the responders, despite them being mostly without certified systems. The size of a company had no significant effect on their attitude. Micro and small producers were involved in raising awareness of environmental policies and responsibilities to the same extent (maybe even more) as medium or large companies. We also found varying behaviours between companies involved in environmental programs and those who were not. The companies involved felt a strong attitude towards all three pillars of CSR, which are the environment, as well as social and economic aspects. Those companies not involved had a strong attitude towards their customers, but not towards their employees, suppliers or the wider community. They also had stronger feelings about the quality of their products and economic profit, but without a strong approach to the related environmental issues. The Norwegian approach and the commitment of the company Swix to CSR are two positive examples leading to a fluorine-free future.
- ItemDisintegration of Wastewater Activated Sludge (WAS) for Improved Biogas Production(MDPI, 2019-12-21) Wacławek, Stanisław; Grübel, Klaudiusz; Silvestri, Daniele; Padil, Vinod V. T; Wacławek, Maria; Černík, Miroslav; Varma, Rajender SDue to rapid urbanization, the number of wastewater treatment plants (WWTP) has increased, and so has the associated waste generated by them. Sustainable management of this waste can lead to the creation of energy-rich biogas via fermentation processes. This review presents recent advances in the anaerobic digestion processes that have led to greater biogas production. Disintegration techniques for enhancing the fermentation of waste activated sludge can be apportioned into biological, physical and chemical means, which are included in this review; they were mainly compared and contrasted in terms of the ensuing biogas yield. It was found that ultrasonic- and microwave-assisted disintegration provides the highest biogas yield (>500%) although they tend to be the most energy demanding processes (>10,000 kJ kg−1 total solids).
- ItemEffect of CoSi2 interfacial layer on the magnetic properties of Si vertical bar CoSi2 vertical bar Sm-Co thin films(ELSEVIER, RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2020-01-01) Saravanan, P.; Boominathasellarajan, S.; Sobel, Bartlomiej; Waclawek, Stanislaw; Vinod, Vellora Thekkae Padil; Černík, MiroslavMagnetic thin films with a layer sequence of Si vertical bar CoSi2 vertical bar Sm-Co were grown by direct sputter deposition at elevated temperatures, through interfacial diffusion between Si (1 0 0) substrate and the overlying Sm-Co layer. HR-TEM analysis revealed the occurrence of CoSi2 -interfacial layer close to the Si-substrate surface, with controllable thicknesses of similar to 20 and 35 nm at deposition temperatures: 450 and 500 degrees C, respectively. XRD studies confirmed the crystallization of Sm2Co17 and SmCo5 magnetic phases accompanied by the other phases such as CoSi2 and SmCoSi2 due to the intermixing of Co and Si-atoms at higher deposition temperatures. The measured coercivity values are found to be increased from 8.7 to 11.6 kOe at higher CoSi2-layer thickness. The angular-dependent hysteresis measurements demonstrated a distinct isotropic and uniaxial magnetic anisotropy characteristics for the Sm-Co films consisting of 35 and 20-nm thick CoSi2 interfacial layers, respectively and the associated magnetization reversal mechanisms are discussed using the Stoner-Wohlfarth model. The temperature coefficients of remanence (alpha) and coercivity (beta) were determined from the temperature-dependent hysteresis curves. The Sm-Co films consisting of 35-nm thick CoSi2-layer exhibited a better thermal stability with 'alpha' and 'beta' values of 0.35 +/- 0.05%/degrees C and -0.13 +/- 0.02%/degrees C, respectively. The results of present study provide splendid opportunities for exploiting the potential of CoSi2 as an under layer, for growing the Sm-Co films towards high-temperature applications.
- ItemEngineered in situ biogeochemical transformation as a secondary treatment following ISCO – A field test(2019) Němeček, Jan; Nechanická, Magda; Špánek, Roman; Eichler, František; Zeman, Josef; Černík, MiroslavISCO using activated sodium persulphate is a widely used technology for treating chlorinated solvent source zones. In sensitive areas, however, high groundwater sulphate concentrations following treatment may be a drawback. In situ biogeochemical transformation, a technology that degrades contaminants via reduced iron minerals formed by microbial activity, offers a potential solution for such sites, the bioreduction of sulphate and production of iron sulphides that abiotically degrade chlorinated ethenes acting as a secondary technology following ISCO. This study assesses this approach in the field using hydrochemical and molecular tools, solid phase analysis and geochemical modelling. Following a neutralisation and bioaugmentation, favourable conditions for iron- and sulphate-reducers were created, resulting in a remarkable increase in their relative abundance. The abundance of dechlorinating bacteria (Dehalococcoides mccartyi, Dehalobacter sp. and Desulfitobacterium spp.) remained low throughout this process. The activity of iron- and sulphate-reducers was further stimulated through application of magnetite plus starch and microiron plus starch, resulting in an increase in ferrous iron concentration (from
- ItemFabrication, Characterization, and Antibacterial Properties of Electrospun Membrane Composed of Gum Karaya, Polyvinyl Alcohol, and Silver Nanoparticles(Hindawi Publishing Corporation, 2015) Padil, Vinod Vellora Thekkae; Nguyen, Nhung H. A.; Ševců, Alena; Černík, MiroslavGum karaya (GK), a natural hydrocolloid, was mixed with polyvinyl alcohol (PVA) at different weight ratios and electrospun to produce PVA/GK nanofibers. An 80 : 20 PVA/GK ratio produced the most suitable nanofiber for further testing. Silver nanoparticles (Ag-NPs) were synthesised through chemical reduction of AgNO3 (at different concentrations) in the PVA/GK solution, the GK hydroxyl groups being oxidised to carbonyl groups, and Ag+ cations reduced to metallic Ag-NPs. These PVA/GK/Ag solutions were then electrospun to produce nanofiber membranes containing Ag-NPs (Ag-MEMs). Membrane morphology and other characteristics were analysed using scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy, and UV-Vis and ATR-FTIR spectroscopy. The antibacterial activity of the Ag-NP solution and Ag-MEM was then investigated against Gram-negative Escherichia coli and Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. Our results show that electrospun nanofiber membranes based on natural hydrocolloid, synthetic polymer, and Ag-NPs have many potential uses in medical applications, food packaging, and water treatment.
- ItemGreen synthesis of copper oxide nanoparticles using gum karaya as a biotemplate and their antibacterial application(Dove Medical Press Ltd, 2013) Padil, Vinod Vellora Thekkae; Černík, MiroslavBackground: Copper oxide (CuO) nanoparticles have attracted huge attention due to catalytic, electric, optical, photonic, textile, nanofluid, and antibacterial activity depending on the size, shape, and neighboring medium. In the present paper, we synthesized CuO nanoparticles using gum karaya, a natural nontoxic hydrocolloid, by green technology and explored its potential antibacterial application. Methods: The CuO nanoparticles were synthesized by a colloid-thermal synthesis process. The mixture contained various concentrations of CuCl2 center dot 2H(2)O (1 mM, 2 mM, and 3 mM) and gum karaya (10 mg/mL) and was kept at 75 degrees C at 250 rpm for 1 hour in an orbital shaker. The synthesized CuO was purified and dried to obtain different sizes of the CuO nanoparticles. The well diffusion method was used to study the antibacterial activity of the synthesized CuO nanoparticles. The zone of inhibition, minimum inhibitory concentration, and minimum bactericidal concentration were determined by the broth microdilution method recommended by the Clinical and Laboratory Standards Institute. Results: Scanning electron microscopy analysis showed CuO nanoparticles evenly distributed on the surface of the gum matrix. X-ray diffraction of the synthesized nanoparticles indicates the formation of single-phase CuO with a monoclinic structure. The Fourier transform infrared spectroscopy peak at 525 cm(-1) should be a stretching of CuO, which matches up to the B-2u mode. The peaks at 525 cm(-1) and 580 cm(-1) indicated the formation of CuO nanostructure. Transmission electron microscope analyses revealed CuO nanoparticles of 4.8 +/- 1.6 nm, 5.5 +/- 2.5 nm, and 7.8 +/- 2.3 nm sizes were synthesized with various concentrations of CuCl2 center dot 2H(2)O (1 mM, 2 mM, and 3 mM). X-ray photoelectron spectroscopy profiles indicated that the O 1s and Cu 2p peak corresponding to the CuO nanoparticles were observed. The antibacterial activity of the synthesized nanoparticles was tested against Gram-negative and positive cultures. Conclusion: The formed CuO nanoparticles are small in size (4.8 +/- 1.6 nm), highly stable, and have significant antibacterial action on both the Gram classes of bacteria compared to larger sizes of synthesized CuO (7.8 +/- 2.3 nm) nanoparticles. The smaller size of the CuO nanoparticles (4.8 +/- 1.6 nm) was found to be yielding a maximum zone of inhibition compared to the larger size of synthesized CuO nanoparticles (7.8 +/- 2.3 nm). The results also indicate that increase in precursor concentration enhances an increase in particle size, as well as the morphology of synthesized CuO nanoparticles.
- ItemGreen Synthesis of High Temperature Stable Anatase Titanium Dioxide Nanoparticles Using Gum Kondagogu: Characterization and Solar Driven Photocatalytic Degradation of Organic Dye(MDPI, 2019-12-04) Sivan Saranya, Kothaplamoottil; Vellora Thekkae Padil, Vinod; Senan, Chandra; Pilankatta, Rajendra; Saranya, Kunjumon; George, Bini; Wacławek, Stanisław; Černík, MiroslavThe present study reports a green and sustainable method for the synthesis of titanium dioxide (TiO2) nanoparticles (NPs) from titanium oxysulfate solution using Kondagogu gum (Cochlospermum gossypium), a carbohydrate polymer, as the NPs formation agent. The synthesized TiO2 NPs were categorized by techniques such as X-Ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy analysis, Raman spectroscopy, scanning electron microscope- Energy-dispersive X-ray spectroscopy (SEM-EDX), Transmission electron microscopy (TEM), High-resolution transmission electron microscopy (HR-TEM), UV-visible spectroscopy, Brunauer-Emmett-Teller (BET) surface area and particle size analysis. Additionally, the photocatalytic actions of TiO2 NPs were assessed with regard to their ability to degrade an organic dye (methylene blue) from aqueous solution in the presence of solar light. Various parameters affecting the photocatalytic activity of the TiO2 NPs were examined, including catalyst loading, reaction time, pH value and calcination temperature of the aforementioned particles. This green synthesis method involving TiO2 NPs explores the advantages of inexpensive and non-toxic precursors, the TiO2 NPs themselves exhibiting excellent photocatalytic activity against dye molecules.
- ItemGreener assembling of MoO3 nanoparticles supported on gum arabic: cytotoxic effects and catalytic efficacy towards reduction of p-nitrophenol(2019) Kothaplamoottil Sivan, Saranya; Padinjareveetil, Akshay K.K.; Padil, Vinod V. T.; Pilankatta, Rajendra; George, Bini; Senan, Chandra; Černík, Miroslav; Varma, Rajender S.An economical and easy one-step method for the biosynthesis of highly stable molybdenum trioxide (MoO3) nanoparticles was developed using gum arabic as a bio-template; ensuing nanoparticles (NP) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, UV–visible spectroscopy, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The crystallinity and purity of MoO3 nanoparticles in the orthorhombic phase were confirmed by XRD analysis, and their rod-shaped identity (average sizes ranging from 7.5 to 42 nm) were observed by TEM. Cytotoxic effects of the NP were monitored using Hep G2 (human liver cancer) and HEK 293 (human embryonic kidney) cell lines via 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assays. The results of this study revealed that MoO3 nanoparticles are nontoxic towards Hep G2 cell lines and displayed negligible toxicity, even at very high concentrations (1000 ppm), although had moderate toxicity towards HEK 293 cells. Furthermore, their catalytic activity was evaluated for the reduction of p-nitrophenol to p-aminophenol. Graphical abstract: Synopsis: Green synthesis of MoO3 nanorods using gum arabic demonstrated as an eco-friendly catalyst for the conversion of p-nitrophenol with negligible toxicity towards Hep G2 cell lines.[Figure not available: see fulltext.].
- ItemGum Kondagogu/Reduced Graphene Oxide Framed Platinum Nanoparticles and Their Catalytic Role(MDPI, 2019-10) Venkateshaiah, Abhilash; Silvestri, Daniele; Ramakrishnan, Rohith K; Wacławek, Stanislaw; Padil, Vinod V. T; Černík, Miroslav; Varma, Rajender S.This study investigates an environmentally benign approach to generate platinum nanoparticles (Pt NP) supported on the reduced graphene oxide (RGO) by non-edible gum waste of gum kondagogu (GK). The reaction adheres to the green chemistry approach by using an aqueous medium and a nontoxic natural reductant-GK-whose abundant hydroxyl groups facilitate in the reduction process of platinum salt and helps as well in the homogenous distribution of ensued Pt NP on RGO sheets. Scanning Electron Microscopy (SEM) confirmed the formation of kondagogu gum/reduced graphene oxide framed spherical platinum nanoparticles (RGO-Pt) with an average particle size of 3.3 ± 0.6 nm, as affirmed by Transmission Electron Microscopy (TEM). X-ray Diffraction (XRD) results indicated that the Pt NPs formed are crystalline with a face-centered cubic structure, while morphological analysis by XRD and Raman spectroscopy revealed a simultaneous reduction of GO and Pt. The hydrogenation of 4-nitrophenol could be accomplished in the superior catalytic performance of RGO-Pt. The current strategy emphasizes a simple, fast and environmentally benign technique to generate low-cost gum waste supported nanoparticles with a commendable catalytic activity that can be exploited in environmental applications.
- ItemHigh reactive nano zero-valent iron produced via wet milling through abrasion by alumina(ELSEVIER SCIENCE SA, PO BOX 564, 1001 LAUSANNE, SWITZERLAND, 2019-06-15) Ribas, D.; Pešková, Kristýna; Jubany, I.; Parma, Petr; Černík, Miroslav; Benito, J. A.; Marti, V.The performance of new nano zero-valent iron (nZVI) particles produced by a promising new milling method in organic solvent was examined. The basic feature of the new process involves the addition of abrasive alumina particles having an average particle size of 5 mu m during milling. The milled particles with alumina had a specific surface area exceeding 20m(2) . g(-1) as well as high percentages of Fe(0) content of 75-80%. The reactivity against Cr(VI), Trichloroethylene, and Tetrachloroethylene was determined and in all cases, the removal capacity of the milled particles was higher than that of commercial available nZVI particles. This high reactivity may be related to the absence of a thick and continuous oxide layer on the surface, the high disorder levels of the metallic structure and the large number of reaction sites. Sedimentation tests revealed very good suspension stability, while in mobility tests, the particles could be distributed throughout the column length. The results showed a low tendency to agglomerate in aqueous solution. This behaviour has been attributed to two factors related to the milling process: first, the high.-Potential found in the particles, which enhances electrostatic repulsion. The second factor is the significant decrease of saturation magnetization of the milled particles with alumina in comparison with the values of the commercial nZVI particles, leading to a reduction in magnetic interparticle interaction. This decrease may be related to the introduction of a significant carbon content in the iron particles (0.65-1.35% wt, depending on the sample) and the presence of a highly deformed nanostructure.
- ItemHydrochemical Conditions for Aerobic/Anaerobic Biodegradation of Chlorinated Ethenes—A Multi-Site Assessment(MDPI, 2020-01-23) Němeček, Jan; Marková, Kristýna; Špánek, Roman; Antoš, Vojtěch; Kozubek, Petr; Lhotský, Ondřej; Černík, MiroslavA stall of cis-1,2-DCE and vinyl chloride (VC) is frequently observed during bioremediation of groundwater chloroethenes via reductive dechlorination. These chloroethenes may be oxidised by aerobic methanotrophs or ethenotrophs co-metabolically and/or metabolically. We assessed the potential for such oxidation at 12 sites (49 groundwater samples) using hydrochemical and molecular biological tools. Both ethenotroph (etnC and etnE) and methanotroph (mmoX and pmoA) functional genes were identified in 90% of samples, while reductive dehalogenase functional genes (vcrA and bvcA) were identified in 82%. All functional genes were simultaneously detected in 78% of samples, in actively biostimulated sites in 88% of samples. Correlation analysis revealed that cis-1,2-DCE concentration was positively correlated with vcrA, etnC and etnE, while VC concentration was correlated with etnC, etnE, vcrA and bvcA. However, feature selection based on random forest classification indicated a significant relationship for the vcrA in relation to cis-1,2-DCE, and vcrA, bvcA and etnE for VC and no prove of relationship between cis-1,2-DCE or VC and the methanotroph functional genes. Analysis of hydrochemical parameters indicated that aerobic oxidation of chloroethenes by ethenotrophs may take place under a range of redox conditions of aquifers and coincide with high ethene and VC concentrations.
- ItemHydrocolloid-Stabilized Magnetite for Efficient Removal of Radioactive Phosphates(Hindawi Publishing Corporation, 2014) Padil, Vinod Vellora Thekkae; Rouha, Michael; Černík, MiroslavLiquid radioactive waste is a common by-product when using radioactive isotopes in research and medicine. Efficient remediation of such liquid waste is crucial for increasing safety during the necessary storage of the material. Herein, we present a novel Gum Karaya stabilized magnetite for the efficient removal of radioactive phosphorus P-32 from liquid radioactive waste. This environmentally friendly material is well suited to be used as a nanohydrogel for the removal of liquid waste, which can then be stored in a smaller space and without the risk of the spills inherent to the initial liquid material. The maximum adsorption capacity of the GK/M in this study was found to be 15.68GBq/g. We present a thorough morphological characterization of the synthesised GK/M, as well as a discussion of the possible phosphorus adsorption mechanisms.
- ItemInterfacial layer formation during high-temperature deposition of Sm-Co magnetic thin films on Si (100) substrates(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2019-03) Saravanan, P.; Boominathasellarajan, S.; Sobel, Bartlomiej; Waclawek, Stanislaw; Vinod, Vellora Thekkae Padil; Talapatra, A.; Mohanty, J.; Černík, MiroslavThe interfacial layer that has formed during the deposition of similar to 240-nm thick Sm-Co films on the bare Si (100) substrate was investigated at different deposition temperatures, T-d,T-Sm-Co: 400, 450 and 500 degrees C with respect to structural and magnetic properties of Sm-Co films. X-ray diffraction analysis showed the crystallization of both Sm2Co17(R) and SmCo5(H) magnetic phases. Rutherford back scattering studies demonstrated that the surface-diffusion reactions between the Sm-Co layer and Si-surface not only accompanied by the quasi-layered growth of CoSi2-phase; but also led to the formation of SmCoSi2-phase. Cross-sectional transmission electron microscopy analysis revealed uneven boundary with deeply grown CoSi2-layer and Moire fringes at limited regions of Co/Si interface. Magnetic measurements showed a square hysteresis loop with maximum values of coercivity (11.6 kOe) and remanence ratio (0.99) for the films grown at 500 degrees C. Magnetic force microscopy images depicted patch-like domains with increasing phase contrast against T-d,T-Sm-Co. In addition, the changes that has occurred in the magnetization reversal processes accompanied by coercivity enhancement due to higher T-d,T-Sm-Co is discussed in the context of domain morphology and first-order reversal curves.
- ItemKombinovaná metoda laktát-nanoželezo pro odstranění chlorovaných uhlovodíků(Technická Univerzita v Liberci, 2007) Křiklavová, Lucie; Černík, MiroslavCílem této práce je optimalizace odstraňování kontaminace z lokality Kuřivody (obecně však z jakéhokoli území znečistěného zejména chlorovanými uhlovodíky), a to metodou co nejvíce šetrnou k okolnímu prostředí, metodou co nejúčinnější, časově a finančně nenáročnou. Jedním z možných postupů je kombinace mikrobiálně podpořené reduktivní dechlorace a reduktivní dechlorace s využitím nanočástic nulmocného železa. Základním principem dekontaminace je reduktivní dechlorace uhlovodíků, kdy atomy chloru jsou nahrazeny atomem vodíku, a to za pomoci chemické látky a současně za pomoci mikroorganismů. Při použití mikrobiálně podpořené dechlorace a částečně i při použití nanoželeza sice vznikají stále ještě toxické meziprodukty, ale i ty jsou postupně odbourávány a vznikají látky, které jsou méně toxické. Degradace končí plynným ethenem, který uniká do vzduchu, ve vodě se tak nachází minimální kontaminace nebo je v limitních hodnotách. Laboratorní práce jsou prováděny ve třech různých koncentracích nanoželeza (koncentrace laktátu je vždy stejná) a ve třech různých časových odstupech mezi injektážemi laktátu a železa. Na základě laboratorních experimentů jsou definovány podmínky pro optimální pilotní ověření. Získaná data ukazují velmi slibné výsledky použitelnosti metody pro plnou sanaci. Proces je o poznání jednodušší, šetrnější, účinnější a také lacinější než tradiční postupy za pomoci oxidačních činidel, sanačního čerpání či odtěžení, kdy se vytěžená kontaminovaná zemina odváží k čištění do specializovaných provozů. Při experimentech bylo zjištěno, že kombinace je nejúčinnější zejména pro nejvyšší koncentraci nanoželeza (3190 mg/l Fe) a pro dobu ne kratší než cca 3 měsíce mezi injektážemi laktátu a nanočásticemi. Pilotní aplikace proběhly na lokalitě Kuřivody, a to s velice příznivými výsledky. Metoda bude dále testována, což prokazuje, že daná technika je velice perspektivní. Konečným výsledkem je, že kombinovaná metoda laktátu a nanoželeza, ačkoli ještě není dokonale prostudována, je velice účinná a přináší spoustu výhodných vlastností.