The effect of preparation of biogenic sorbent on zinc sorption

The aim of this study is to prepare biogenic sulphides by using bacteria for the removal of zinc cations from their solutions. Theproduction was realized in a bioreactor under anaerobic conditions at 30 °C. Sorbents were prepared by sulphate-reducing bacteria indifferent nutrient medium modifications, under two modes of bacteria cultivation. Created precipitates of iron sulphides were removedfrom the liquid phase of the cultivation medium by filtration, dried and used for the sorption experiments

Neka svojstva prašine smrekovine dobivene procesom brušenja

This paper presents the research of selected properties of spruce dust generated from experimental sanding by a hand belt sander with two sanding models - along the wood fibres and perpendicular to the wood fibres in the radial direction. The experiment was carried out for the purpose of obtaining the basic characteristics of wood sanding dust – granularity, size and shape of individually formed particles, and bulk properties (bulk density, bulk angle, and tilt angle) that are important for suction, which is connected with the quality of living and working environments. The particles smaller than 100 micrometers are unsuitable for both environments, since they do not sediment in space at all or only partly, and they are characterized as airborne dust. The most harmful particles for humans are those smaller than 2.5 μm as they reach the lung alveoli. When sanding wood the finest particles are formed and therefore it is important to know the basic characteristics of sanding dust in order to deal with these problems effectively. On the basis of the mesh sieve analysis, we can state that in sanding perpendicular to the wood fibres the share of particles smaller than 100 μm is 76.94 % on average and along the wood fibres it is only 56.01 %. The structure, shape and size of particles were investigated by microscope. When using the longitudinal model of sanding, the fibrous elements were formed for the most part. When using the perpendicular model, isometric particles were predominantly formed in smaller fractions and particles of fibrous shape in larger fractions. The smallest particles were found in the following samples. When the perpendicular model of sanding was used, we have found the smallest particle in the investigated samples with the diameter of 1.68 μm, and when the longitudinal model of sanding was used, the particle with the diameter of 1.75 μm. Bulk density of spruce dust from the longitudinal model of sanding is 77.77 kg · m-3, while dust from the perpendicular model of sanding is 116.68 kg · m-3. Tilt angle of spruce dust in a longitudinal direction of sanding is 33.4°, and in a perpendicular direction it is 37.4°. Bulk angle for the perpendicular model of sanding is 48.7°, and for longitudinal model of sanding it is 48.3°. The obtained results have confirmed that the model of sanding at which wood dust was formed is a significant factor affecting properties of wood bulk material.U radu su istraživana neka svojstva prašine smrekovine dobivene ručnim eksperimentalnim brušenjem u dva smjera – u smjeru vlakanaca i okomito na njih, i to u radijalnom smjeru. Cilj istraživanja bio je odrediti osnovna obilježja čestica bruševine – granulaciju, veličinu čestica i oblike individualnih čestica, nasipna svojstva (nasipnu gustoću, nasipni kut i kut klizanja s kosine), koje su važne pri njihovu odsisavanju i za njihov utjecaj na kvalitetu općega i radnog okoliša. Za obje vrste okoliša štetno je postojanje čestica manjih od 100 μm, a s obzirom na to da se one teško talože ili se uopće ne talože, smatraju se lebdećim česticama. Najštetnije čestice za ljudski organizam jesu one manje od 2,5 μm jer dospijevaju do plućnih alveola. Uspješno rješavanje problema nastajanja najfinijih čestica bruševine moguće je uz poznavanje njihovih osnovnih obilježja. Granulometrijskom analizom bruševine nastale brušenjem okomito na drvna vlakanca izmjeren je udio od 76,94 % čestica manjih od 100 μm, a brušenjem u smjeru vlakanaca samo 56,01 %. Struktura, oblik i veličina čestica istražena je uz pomoć mikroskopa. Pri brušenju duž vlakanaca formirani su pretežno vlaknasti elementi. Pri brušenju okomito na vlakanca uglavnom su nastajale izometrične čestice u sitnijim frakcijama te čestice vlaknastog oblika u krupnijim frakcijama. Među česticama nastalim pri brušenju okomito na vlakanca izmjeren je najmanji promjer čestice od 1,68 μm, a pri brušenju uzdužno s vlakancima promjer 1,75 μm. Nasipna gustoća smrekove bruševine pri uzdužnom brušenju iznosi 77,77 kg/m³, odnosno 116,68 kg/m³ pri brušenju okomito na vlakanca. Kut klizanja s kosine bruševine nastale brušenjem u smjeru vlakanaca iznosi 33,4°, a kut klizanja bruševine nastale brušenjem okomito na vlakanca 37,4°. Nasipni kut za bruševinu nastalu brušenjem okomito na vlakanca iznosi 48,7°, a za bruševinu nastalu brušenjem uzdužno na vlakanca 48,3°. Dobiveni rezultati potvrdili su da smjer brušenja s obzirom na smjer vlakanaca ima značajan utjecaj na veličinu i svojstva usitnjenoga drvnog materijala

Ekonomické reformy Kórey v období prechodu k demokracii

Luptáková, J. Economic reforms of Korea in the period of transition to democracy. Bachelor thesis. Brno: Mendel university, 2023. The bachelor's thesis presents the issue of the economic development of Korea during the transition to democracy in the eighties and nineties of the 20th century. The main goal of the bachelor's thesis is to answer and evaluate the research question: What were the factors of successful economic development in the period of political transformation when the country generally faced economic decline and imbalances? The main subject of the bachelor thesis is the analysis of the implemented reforms and their impact on the economic development of Korea in the specified period. The theoretical starting points are drawn from available, mostly foreign scientific and professional literature and reliable, verified internet sources. In the theoretical part of the bachelor's thesis, the focus is on defining the concepts necessary for the analytical part. In the analytical part, research methods such as analysis, synthesis, deduction, and generalization are used to describe the economic development of Korea during the political transition to democracy. The actual contribution of the work is in summarizing the acquired knowledge and providing one's own perspective on the investigated issue, plus in the evaluation of the chosen monetary, fiscal and exchange rate policy in Korea during the transition to democracy

The Metal And Sulphate Removal From Mine Drainage Waters By Biological-Chemical Ways

Mine drainage waters are often characterized by high concentrations of sulphates and metals as a consequence of the mining industry of sulphide minerals. The aims of this work are to prove some biological-chemical processes utilization for the mine drainage water treatment. The studied principles of contamination elimination from these waters include sulphate reduction and metal bioprecipitation by the application of sulphate-reducing bacteria (SRB). Other studied process was metal sorption by prepared biogenic sorbent. Mine drainage waters from Slovak localities Banská Štiavnica and Smolník were used to the pollution removal examination. In Banská Štiavnica water, sulphates decreased below the legislative limit. The elimination of zinc by sorption experiments achieved 84 % and 65 %, respectively

Neka svojstva prašine smrekovine dobivene procesom brušenja

This paper presents the research of selected properties of spruce dust generated from experimental sanding by a hand belt sander with two sanding models - along the wood fibres and perpendicular to the wood fibres in the radial direction. The experiment was carried out for the purpose of obtaining the basic characteristics of wood sanding dust – granularity, size and shape of individually formed particles, and bulk properties (bulk density, bulk angle, and tilt angle) that are important for suction, which is connected with the quality of living and working environments. The particles smaller than 100 micrometers are unsuitable for both environments, since they do not sediment in space at all or only partly, and they are characterized as airborne dust. The most harmful particles for humans are those smaller than 2.5 μm as they reach the lung alveoli. When sanding wood the finest particles are formed and therefore it is important to know the basic characteristics of sanding dust in order to deal with these problems effectively. On the basis of the mesh sieve analysis, we can state that in sanding perpendicular to the wood fibres the share of particles smaller than 100 μm is 76.94 % on average and along the wood fibres it is only 56.01 %. The structure, shape and size of particles were investigated by microscope. When using the longitudinal model of sanding, the fibrous elements were formed for the most part. When using the perpendicular model, isometric particles were predominantly formed in smaller fractions and particles of fibrous shape in larger fractions. The smallest particles were found in the following samples. When the perpendicular model of sanding was used, we have found the smallest particle in the investigated samples with the diameter of 1.68 μm, and when the longitudinal model of sanding was used, the particle with the diameter of 1.75 μm. Bulk density of spruce dust from the longitudinal model of sanding is 77.77 kg · m-3, while dust from the perpendicular model of sanding is 116.68 kg · m-3. Tilt angle of spruce dust in a longitudinal direction of sanding is 33.4°, and in a perpendicular direction it is 37.4°. Bulk angle for the perpendicular model of sanding is 48.7°, and for longitudinal model of sanding it is 48.3°. The obtained results have confirmed that the model of sanding at which wood dust was formed is a significant factor affecting properties of wood bulk material.U radu su istraživana neka svojstva prašine smrekovine dobivene ručnim eksperimentalnim brušenjem u dva smjera – u smjeru vlakanaca i okomito na njih, i to u radijalnom smjeru. Cilj istraživanja bio je odrediti osnovna obilježja čestica bruševine – granulaciju, veličinu čestica i oblike individualnih čestica, nasipna svojstva (nasipnu gustoću, nasipni kut i kut klizanja s kosine), koje su važne pri njihovu odsisavanju i za njihov utjecaj na kvalitetu općega i radnog okoliša. Za obje vrste okoliša štetno je postojanje čestica manjih od 100 μm, a s obzirom na to da se one teško talože ili se uopće ne talože, smatraju se lebdećim česticama. Najštetnije čestice za ljudski organizam jesu one manje od 2,5 μm jer dospijevaju do plućnih alveola. Uspješno rješavanje problema nastajanja najfinijih čestica bruševine moguće je uz poznavanje njihovih osnovnih obilježja. Granulometrijskom analizom bruševine nastale brušenjem okomito na drvna vlakanca izmjeren je udio od 76,94 % čestica manjih od 100 μm, a brušenjem u smjeru vlakanaca samo 56,01 %. Struktura, oblik i veličina čestica istražena je uz pomoć mikroskopa. Pri brušenju duž vlakanaca formirani su pretežno vlaknasti elementi. Pri brušenju okomito na vlakanca uglavnom su nastajale izometrične čestice u sitnijim frakcijama te čestice vlaknastog oblika u krupnijim frakcijama. Među česticama nastalim pri brušenju okomito na vlakanca izmjeren je najmanji promjer čestice od 1,68 μm, a pri brušenju uzdužno s vlakancima promjer 1,75 μm. Nasipna gustoća smrekove bruševine pri uzdužnom brušenju iznosi 77,77 kg/m³, odnosno 116,68 kg/m³ pri brušenju okomito na vlakanca. Kut klizanja s kosine bruševine nastale brušenjem u smjeru vlakanaca iznosi 33,4°, a kut klizanja bruševine nastale brušenjem okomito na vlakanca 37,4°. Nasipni kut za bruševinu nastalu brušenjem okomito na vlakanca iznosi 48,7°, a za bruševinu nastalu brušenjem uzdužno na vlakanca 48,3°. Dobiveni rezultati potvrdili su da smjer brušenja s obzirom na smjer vlakanaca ima značajan utjecaj na veličinu i svojstva usitnjenoga drvnog materijala

Influence of Boundary Conditions on the Solution to a Mathematical Model for a Given Wooden Plate

The article examines deformation of wood veneer and internal forces resulting from bending. Wood is modelled as an orthotropic material. A thin circular wooden plate hemispherically supported at its free edge is bent by axial hubbing of the punch with a hemispherical end. The analysis of the models is carried out by the ANSYS software. Geometric boundary conditions are calculated and set by a macro formed by the APDL (ANSYS Parametric Design Language) scenario language. For the reason of comparison the models were solved for a given plate with simplified boundary conditions

Influence of Boundary Conditions on the Solution to a Mathematical Model for a Given Wooden Plate

The article examines deformation of wood veneer and internal forces resulting from bending. Wood is modelled as an orthotropic material. A thin circular wooden plate hemispherically supported at its free edge is bent by axial hubbing of the punch with a hemispherical end. The analysis of the models is carried out by the ANSYS software. Geometric boundary conditions are calculated and set by a macro formed by the APDL (ANSYS Parametric Design Language) scenario language. For the reason of comparison the models were solved for a given plate with simplified boundary conditions

Magnetic sorbents biomineralization on the basis of iron sulphides

Biomineralization means mineral formation under the influence of organisms. Sulphate-reducing bacteria (SRB) constitute an essential role of iron sulphide minerals precipitation. Their composition involves amorphous, non-stoichiometric or crystalline iron sulphides, weakly or strongly magnetic. Variation in environmental conditions can alter the reactive iron species within the mineral, potentially modifying their magnetic properties. Biogenic iron sulphide minerals can be used as heavy metals and toxic ions adsorbents in soil or water remediation. For these reasons, a series of laboratory-scale iron sulphide synthesis experiments with the aim to study the chemical composition, mineralogy and magnetic properties of iron sulphide precipitates were carried out using SRB under various cultivation mode and nutrient medium composition. Energy-dispersive X-ray analysis (EDX) showed formation of iron sulphides in all biogenic samples and iron phosphates in abiotic controls. Results of X-ray diffraction analysis (XRD) in biomineralized samples confirmed nanocrystalline greigite, mackinawite and sulphur alpha. Magnetic measurements showed that sample prepared by static cultivation without addition of fresh nutrient medium was the most magnetic, magnetic hysteresis of sample formed under semicontinuous mode without any nutrient supply was the lowest. Abiotic samples contained only vivianite and they did not prove any significant response to magnetic field.Web of Science39222925291

Changes in Chemical Structure of Thermally Modified Spruce Wood Due to Decaying Fungi

Fungi play a critical role in the decomposition of wood and wood-based products in use. The ability of decaying fungi to cause degradation of polysaccharides and lignin in the thermally modified Norway spruce (Picea abies L. Karst.) wood was examined with pure culture decomposition tests in laboratory conditions using the brown-rot fungus Serpula lacrymans (Schumacher ex Fries) S.F. Gray and white-rot fungus Trametes versicolor (Linnaeus ex Fries) Pilat. Spruce wood samples were primary thermally treated under atmospheric pressure at the temperatures of 100, 150, 200, 220, 240 and 260 °C during 1, 3 and 5 h, whereby larger losses in their mass, holocellulose, mannose and xylose were achieved at harder thermal regimes. Meanwhile, the holocellulose percent content reduced considerably, and the percent content of lignin increased sharply. Spruce wood thermally modified at and above 200 °C better resisted to brown-rot fungus S. lacrymans than the white-rot fungus T. versicolor. Due to the decay processes, the mass fractions of holocellulose, cellulose and hemicelluloses were lower in those spruce wood samples in which thermal degradation was more intensive, with achieving the highest mass loss values after thermal treatments, after which the decay attacks were poorer or even none with the minimal mass loss values due to action by the brown-rot fungus S. lacrymans and the white-rot fungus T. versicolor. The mannose and glucose percent content in thermally–fungally attacked spruce wood was intensive reduced, e.g., by 17% to 98% in wood after thermal treatments at temperature equal and above 200 °C