This research presents the effects of sintering process and clay composition on the physico-mecha... more This research presents the effects of sintering process and clay composition on the physico-mechanical properties of ceramics from the fifth and fourth millennium BC (6950 ± 280 to 5040 ± 220 TL dating). The combined multiscale mercury intrusion porosimetry (MIP) revealed the increase of round cryptopores and ultramicropores in a range of 0.01-0.1 μm and 0.1-5 μm respectively, closely linked to vitrified glassy connections and bonding between particles and the partial melting of phyllosilicates with different sizes of bubbles at 950 • C. Cold crushing strength (CCS) of the ceramics, containing high calcite and phyllosilicate mineral exhibited a lower strength value from 6.24 to 6.31 MPa at ~750-800 • C due to the increase in crack porosity area with high interconnectivity and internal stresses. However, the ceramics with a well glassy network show a higher strength value of 16.5Mpa, contributing to sustainable ceramic materials with a uniform cross-section >900 • C and minimal shrinkage for conservation treatment.
Diatomite is one of the most intensively examined raw materials in the materials industry with a ... more Diatomite is one of the most intensively examined raw materials in the materials industry with a broad range of various applications. The diatomite sample, collected from Vitačevo plateau in the vicinity of Kavadarci, was fully characterized by means of physical-mechanical, chemical, XRPD, SEM, TEM, DTA/TGA and IR techniques. The physical-mechanical features pointed out to soft, light, white to gray rock with shell-like structure exhibiting compressive strength from 4.65-4.88 MPa in dry form, whereas the total porosity ranges 70-72% and the density is 2.06-2.09 g/cm 3. The chemical analysis of the diatomite revealed that SiO2 content exceeds 91%. The results from the X-ray powder diffraction indicate predominant amorphous SiO2 phase associated with minor presence of crystalline quartz, muscovite, chlorites and plagioclase. The IR spectrum of the diatomite manifested characteristic bands for amorphous silica at 799 cm-1 and 1101 cm-1. DTA/TGA results display great thermal stability of the sample remaining amorphous up to 1050ºC whereas the SEM analysis determined the morphology, surface characteristics and the nanometric pores in the raw material. Thus, the studied diatomite is classified as a natural nanomaterial that is suitable for broad application in various construction materials, refractory ceramics, special oxide ceramics, and also finds potential use in filtering, adsorbent, catalysts, food and pharmaceutical industries.
The diatomaceous earth (DE), collected from the Mariovo region in North Macedonia, was characteri... more The diatomaceous earth (DE), collected from the Mariovo region in North Macedonia, was characterized and thermally modified. The material represents a sedimentary rock of biogenic origin, soft solid that can be easily disintegrated, with white to grayish color, with bulk density of 0.51-0.55 g/cm 3 , total porosity of 61-63%, and specific gravity of 2.25 g/cm 3. The chemical composition is as follows: SiO 2, 86.03; Al 2 O 3 , 3.01; Fe 2 O 3 , 2.89; MnO, 0.06; TiO 2, 0.20; CaO, 0.76; MgO, 0.28; K 2 O, 0.69; Na 2 O, 0.19; P 2 O 5 , 0.15; and loss of ignition, 5.66 (wt%). The mineralogy of the raw DE is characterized by the predominant presence of amorphous phase, followed by crystalline quartz, mus-covite, kaolinite, and feldspar. Significant changes in the opal phase are observed in the 1,000-1,200°C temperature region. At 1,100°C, the entire opal underwent solid-solid transition to cristobalite. Further ramp of the temperature (1,100-1,200°C) induced formation of mullite. Scanning electron microscopy (SEM) and transmission electron micro-scopy depict the presence of micro-and nanostructures with pores varying from 260 to 650 nm. SEM analysis further determined morphological changes in terms of the pore diameters shrinkage to 120-250 nm in comparison to the larger pores found in the initial material. The results from this investigation improve the understanding of mechanism of silica phase transition and the relevant phase alterations that took place in DE upon calcination temperatures from 500 to 1,200°C.
As important non-timber forest products, wild mushrooms provide diverse benefits, especially nutr... more As important non-timber forest products, wild mushrooms provide diverse benefits, especially nutritional, medicinal and other socioeconomic benefits for ethnic groups located in NorthEast part of the Republic of North Macedonia. Ethno-mycological knowledge of most frequently used fungi was gathered from 32 inhabitants in 12 localities using in-depth interviews during April and November 2019. Each informant was asked about the local name of the fungus, its edibility, methods of preparation, habitat of growth, mode of consumption and medical use. A total of 33 species of wild mushrooms were cited. The results show that knowledge of useful mushrooms differs between two ethnic groups. The Macedonian ethnic group has the highest ethno-mycological expertise compared to Aromanian, which is expressed in their extensive cultural and practical use of fungi. On both ethnic groups man is more involved in harvesting and is the main holders of cultural aspects related to fungi. Despite the presence of edible ectomycorrhizal taxa in the research area, the two ethnic groups only seem to have an interest in saprotrophic taxa.
Streptococcus mutans (S. mutans) has been identified as a major etiologic agent of human dental c... more Streptococcus mutans (S. mutans) has been identified as a major etiologic agent of human dental caries and forms a significant proportion of oral strepto-cocci in carious lesions. This study investigates the correlation of surface properties (effect of contact angle [CA] and free surface energy) on three restorative materials (zirconia, nickel-chromium-molybdenum alloy and composites) used in dental prosthetics with bacterial adhesion to S. mutans. Ten samples of each material (zirconia, nickel-chromium-molybdenum alloy and composites) of 8 mm diameter and 2.5 mm thickness were used. Aqueous CA measurements, free surface energy and bacterial adhesion to the sample surfaces were performed. Bacterial adhesion is determined by planting samples in the blood agar cultures and using an electron microscope (scanning electron microscopy [SEM]). The highest values of bacterial adhesion are found in composites, followed by the metal alloy, while the lowest values are observed in zirconia. Measurements show that zirconia has 17 bacteria; Ni-Cr-Mo alloy has 65, while the composite has 80 bacteria. The composites showed the highest degree of bacterial adhesion, compared to the other investigated materials, which correlates with the free surface energy of the samples (24.31 mJ/m 2 for zirconia, 31.78 mJ/m 2 for Ni-Cr-Mo alloy and 48.82 mJ/m 2 for the composite).
This study is focused on the adsorption of hexavalent chromium ions Cr(VI) using graphene oxide (... more This study is focused on the adsorption of hexavalent chromium ions Cr(VI) using graphene oxide (GO). The GO was prepared by chemical oxidation (Hummers method) of graphite particles. The synthesized GO adsorbent was characterized by Fourier transform infrared spectroscopy and UV-Vis spectroscopy. It was used for the adsorption of Cr(VI) ions. The theoretical calculations based on density functional theory and Monte Carlo calculations were used to explore the preferable adsorption site, interaction type, and adsorption energy of GO toward the Cr(VI) ions. Moreover, the most stable adsorption sites were used to calculate and plot non-covalent interactions. The obtained results are important as they give molecular insights regarding the nature of the interaction between GO surface and the adsorbent Cr(VI) ions. The found adsorption energy of −143.80 kcal/mol is indicative of the high adsorptive tendency of this material. The adsorption capacity value of GO toward these ions is q = 240.361 mg/g.
Contamination of soil by air sediment emitted from coal based thermal power plants is one of the ... more Contamination of soil by air sediment emitted from coal based thermal power plants is one of the basic ecological issue. The aim of this research is to define the impact of production of REK Bitola on the soils from defined microlocality in Pelagonia basin. Chemical, mineralogical and granulometric analyses were performed upon the soil samples. Also basic physical properties of the soil are determined. The chemical composition of the air sediment was also determined. According to the measured values and statistical data of REK Bitola, an average cumulative deposited quantity of air sediment is calculated, as well as the cumulative deposited quantity of trace elements in soil. The deposited air sediment has a negative impact on some of the basic physical and chemical properties of soil, but has no significant effect on the change in porosity and soil properties resulting from it.
Clayey diatomite is the local name for a mixture of diatomaceous earth and clay minerals. It repr... more Clayey diatomite is the local name for a mixture of diatomaceous earth and clay minerals. It represents a greyish, soft, very light, weakly cemented, fine biogenetic sedimentary rock. The studied material is taken from the vicinity of Bitola city (Republic of Macedonia). Here, clayey diatomite was treated up to three temperature intervals (800, 1000 and 1200oC) for a period of 1 hour. The X-ray powder diffraction results indicate the presence of both an amorphous phase and the following crystalline phases: quartz, feldspars (plagioclase), mica (muscovite) and chlorites. The results of SEM analysis revealed skeletons of alga Diatomeae with nano-pores. By thermal treatment of the samples, a gradual change in color as well as higher bulk density and compressive strength was observed. The increase of the temperature, in addition, affected the mineralogical composition and increased the presence of the amorphous phase (aluminasilicate glassy phase). SEM results of the thermally investigated samples depicted morphological changes expressed by shrinkage of the pore diameters in comparison to the initial material. The major and minor constituents were established by chemical analysis revealing the following chemical composition of raw clayey diatomite: SiO2 (63.65 wt%), Al2O3 (11.76 wt%), Fe2O3 (5.93 wt%), MnO (0.13 wt%), TiO2 (0.63 wt%), CaO (1.42 wt%), MgO (2.22 wt%), P2O5 (0.11 wt%), K2O (1.63 wt%), Na2O (0.92 wt%), LOI (11.50 wt%).
Extreme winter time air pollution episodes, fortify public concerns and put focus on air pollutio... more Extreme winter time air pollution episodes, fortify public concerns and put focus on air pollution as most important environmental problem in urban areas throughout the country. However, focused research efforts to derive information about pollution sources and the amount they contribute to ambient air pollution levels, are still missing, thus leaving room for dubious discussions and political, instead of scientifically based abetment strategies. Having in mind importance of proper information on air pollution sources and utilizing the data collected during several different measurement's campaigns performed for city of Skopje, as much extensive additional lab works and modeling efforts, indicative source apportionment analysis was performed for two sites (receptors) within Skopje urban area, one source specific (traffic) and one background site.
Trepel is the local name for a mixture of diatomaceous earth and clay minerals. It represents a g... more Trepel is the local name for a mixture of diatomaceous earth and clay minerals. It represents a greyish, soft, very light, weakly cemented, fine biogenetic sedimentary rock. The studied material is taken from the vicinity of Bitola city (Republic of Macedonia). Here, trepel was treated up to three temperature intervals (800, 1000 and 1200ºC) for a period of 1 hour. The X-ray powder diffraction results indicate the presence of both an amorphous phase and the following crystalline phases: quartz, feldspars (plagioclase), mica (muscovite) and chlorites. The results of SEM analysis revealed skeletons of alga Diatomeae with nano-pores. By thermal treatment of the samples, a gradual change in color as well as higher bulk density and compressive strength was observed. The increase of the temperature, in addition, affected the mineralogical composition and increased the presence of the amorphous phase (aluminasilicate glassy phase). SEM results of the thermally investigated samples depicted morphological changes expressed by shrinkage of the pore diameters in comparison to the initial material. The major and minor constituents were established by chemical analysis revealing the following chemical composition of raw trepel: SiO 2 (63.65 wt%), Al 2 O 3 (11.76 wt%), Fe 2 O 3 (5.93 wt%), MnO (0.13 wt%), TiO 2 (0.63 wt%), CaO (1.42 wt%), MgO (2.22 wt%), P 2 O 5 (0.11 wt%), K 2 O (1.63 wt%), Na 2 O (0.92 wt%), LOI (11.50 wt%).
The physico-mechanical, chemical and mineralogical characteristics of volcanic glass (perlite) fr... more The physico-mechanical, chemical and mineralogical characteristics of volcanic glass (perlite) from the Mariovo region (Macedonia) as well as the mineralogical changes that occur during its thermal treatment were investigated to demonstrate its utilization for industrial use. The native perlite was characterized by chemical analysis, X-ray powder diffraction (XRPD), infrared (IR) spectroscopy, thermal analysis (TGA/DTA), scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), and solid- state NMR. The chemical examination suggests that the perlite represents an acidic volcanic rock with a high percentage of SiO2 (72.45%), high in alkali metal oxides (4.21 wt.% K2O, 3.56 wt.% Na2O), with a loss of ignition 3.54 wt.%. Results from the XRPD indicated major amorphous behaviour, with low amounts of feldspars, quartz, and cristobalite. SEM examinations revealed glassy structure with presence of certain pores (dimensions ranging from 50–100 μm). The determined expansion coefficient was 20 times its original volume. XRPD of expanded perlite compared to the native perlite depicted new intensive peaks of cristobalite. SEM and TEM revealed irregular morphology with broken or ragged edges. On the basis of the chemical and mineralogical composition, the studied perlite is classified as an appropriate material suitable as ceramic flux to lower the sintering temperature.
A B S T R A C T The aim of this study was to test the diatomaceous earth from a deposit near Rožd... more A B S T R A C T The aim of this study was to test the diatomaceous earth from a deposit near Rožden Village (Macedonia) as a raw material for low temperature hydrothermal production of porous ceramics. Hydrothermal synthesis of porous ceramics has been carried out under saturated steam pressure at 130 °C for a period of 1, 2 and 3 h. The objective of this work was to investigate the impact of slaked lime, autoclave curing time, autoclaving temperature and compaction pressure on the compressive strength and porosity of the products. During the hydrothermal synthesis, newly obtained calcium silicate hydrate dominates which give positive effect to the compressive strength and product porosity confirmed by X-ray powder diffraction. Moreover, a calcite was also evidenced by FTIR spectroscopy whose presence additionally increases the compressive strength of the hydrothermal products. The products obtained during the low-temperature hydrothermal reaction are classified as light porous ceramics with bulk density ranging from 0.71 to 0.91 g/cm 3 and compressive strength within 14.7–19.4 MPa.
During the treatment process of drinking water, chlorine reacts with the organic matter present i... more During the treatment process of drinking water, chlorine reacts with the organic matter present in water and forms various disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). The high content of THMs in the drinking water may be cancerogenic for humans and this has resulted in significant scientific and public concern. The aim of this paper was to determine the factors that have an impact on THM formation in the drinking water in the city of Tetova for the autumn season 2011. Results of this research have shown that during high contact time, temperature, pH and chlorine dosage, more THMs were formed. Based on the examined factors, results show that contact time, pH and the chlorine dosage were crucial and had a significant role in THM formation. The presence of THMs was determined with UV-VIS spectrophotometry. This was the first study that researched the factors that impact the formation of THMs in the drinking water in the Republic of Macedonia. The study results match conclusions reached by previous research in the field.
Water is the most essential product that is consumed by humans, which must be prevented from dete... more Water is the most essential product that is consumed by humans, which must be prevented from deterioration in quality. The quality of drinking water becomes even more important as water borne diseases spread through water. For this purpose, we assess the quality of drinking water in the city of Kumanova with some physico-chemical parameters, which have a significant role in determining the potability of drinking water. The obtained results were compared with Macedonian standards as well as with those set by the WHO and the EU. In this research, parameters such as temperature, turbidity, RC, pH, EC, TRAE, TDS, COD, nitrites, nitrates, ammonia and chlorides were found to be within the permissible limits, while residual chlorine in one case were found to be below lower than the recommended limit. Finally, the Drinking Water Quality Index (DWQI) developed by Canadian Council of Ministers of the Environment for five sample points is calculated. It has been found that drinking water in the 2011 spring season was of a Excellent category (average value of DWQI = 95.21) and suitable for drinking. We recommend that the relevant municipal authorities make regular and proper amount disinfection of drinking water, as there is no compromise that can be made when it comes to the drinking water.
In this paper are shown results of the
physical-chemical and mineralogical-petrographic
examinati... more In this paper are shown results of the physical-chemical and mineralogical-petrographic examinations of trepel from Brod-Gneotino, Bitola region, Republic of Macedonia. According to the scanning electronic microscopy (SEM), the infra-red (IR) and powder X-ray (XRPD) examinations, it was determined that examined trepel is composed mainly of opal (of biogenetic origin) as well as quartz, illite – hydromicas, feldspars (plagioclases, feldspars), and chlorites of minor importance. DTА and TGA examinations show results which are in line with the determined mineralogical composition of the sample. With these examinations it is concluded presence of organic matter in the sample. As result of these examinations it can be concluded that this raw material (trepel, natural mixture of diatomite and clay minerals) can be used as raw material for production of ceramic products (based on classical and hydrothermal technology), for synthesis of zeolites, as absorbent for cleaning of raw industrial waters.
The formation of carcinogenic trihalomethanes (THMs) in the process of water disinfection by chlo... more The formation of carcinogenic trihalomethanes (THMs) in the process of water disinfection by chlorine has raised concerns in the scientific community as well as in the public opinion. This study aims to determine the concentration of THMs in Tetova's drinking water during the autumn season and compare it with the regulation in the Republic of Macedonia, the European Union and the World Health Organization. To this end, we have used the UV-VIS spectrophotometric method based on Fujiwara's reaction. The THMs concentration was measured in fifteen different locations in September, October and November 2011. The results indicate that the seasonal variation is below the critical values stipulated in the state, EU and WHO regulations (seasonal average 22.22 ± 12.06 μg/L). This study is the first of its kind on THMs in the Republic of Macedonia. In conclusion, it can be inferred that the concentration of THMs in the drinking water of Tetova is not hazardous to human health.
Water is the most essential product that is consumed by humans, which must be prevented from dete... more Water is the most essential product that is consumed by humans, which must be prevented from deterioration in quality. The quality of drinking water becomes even more important as water borne diseases spread through water. For this purpose, we assess the quality of drinking water in the city of Tetova with some physico-chemical parameters, which have a significant role in determining the potability of drinking water. The obtained results were compared with Macedonian standards as well as with those set by the WHO and the EU. In this research, parameters such as temperature, pH, EC, TRAE, TDS, COD, TOC, DOC, nitrates and chlorides were found to be within the permissible limits, while turbidity and residual chlorine in some cases were found to be below ore above the recommended limit. Finally, the Drinking Water Quality Index (DWQI) developed by Canadian Council of Ministers of the Environment for fifteen sample points is calculated. It has been found that drinking water in the 2011 a...
This research presents the effects of sintering process and clay composition on the physico-mecha... more This research presents the effects of sintering process and clay composition on the physico-mechanical properties of ceramics from the fifth and fourth millennium BC (6950 ± 280 to 5040 ± 220 TL dating). The combined multiscale mercury intrusion porosimetry (MIP) revealed the increase of round cryptopores and ultramicropores in a range of 0.01-0.1 μm and 0.1-5 μm respectively, closely linked to vitrified glassy connections and bonding between particles and the partial melting of phyllosilicates with different sizes of bubbles at 950 • C. Cold crushing strength (CCS) of the ceramics, containing high calcite and phyllosilicate mineral exhibited a lower strength value from 6.24 to 6.31 MPa at ~750-800 • C due to the increase in crack porosity area with high interconnectivity and internal stresses. However, the ceramics with a well glassy network show a higher strength value of 16.5Mpa, contributing to sustainable ceramic materials with a uniform cross-section >900 • C and minimal shrinkage for conservation treatment.
Diatomite is one of the most intensively examined raw materials in the materials industry with a ... more Diatomite is one of the most intensively examined raw materials in the materials industry with a broad range of various applications. The diatomite sample, collected from Vitačevo plateau in the vicinity of Kavadarci, was fully characterized by means of physical-mechanical, chemical, XRPD, SEM, TEM, DTA/TGA and IR techniques. The physical-mechanical features pointed out to soft, light, white to gray rock with shell-like structure exhibiting compressive strength from 4.65-4.88 MPa in dry form, whereas the total porosity ranges 70-72% and the density is 2.06-2.09 g/cm 3. The chemical analysis of the diatomite revealed that SiO2 content exceeds 91%. The results from the X-ray powder diffraction indicate predominant amorphous SiO2 phase associated with minor presence of crystalline quartz, muscovite, chlorites and plagioclase. The IR spectrum of the diatomite manifested characteristic bands for amorphous silica at 799 cm-1 and 1101 cm-1. DTA/TGA results display great thermal stability of the sample remaining amorphous up to 1050ºC whereas the SEM analysis determined the morphology, surface characteristics and the nanometric pores in the raw material. Thus, the studied diatomite is classified as a natural nanomaterial that is suitable for broad application in various construction materials, refractory ceramics, special oxide ceramics, and also finds potential use in filtering, adsorbent, catalysts, food and pharmaceutical industries.
The diatomaceous earth (DE), collected from the Mariovo region in North Macedonia, was characteri... more The diatomaceous earth (DE), collected from the Mariovo region in North Macedonia, was characterized and thermally modified. The material represents a sedimentary rock of biogenic origin, soft solid that can be easily disintegrated, with white to grayish color, with bulk density of 0.51-0.55 g/cm 3 , total porosity of 61-63%, and specific gravity of 2.25 g/cm 3. The chemical composition is as follows: SiO 2, 86.03; Al 2 O 3 , 3.01; Fe 2 O 3 , 2.89; MnO, 0.06; TiO 2, 0.20; CaO, 0.76; MgO, 0.28; K 2 O, 0.69; Na 2 O, 0.19; P 2 O 5 , 0.15; and loss of ignition, 5.66 (wt%). The mineralogy of the raw DE is characterized by the predominant presence of amorphous phase, followed by crystalline quartz, mus-covite, kaolinite, and feldspar. Significant changes in the opal phase are observed in the 1,000-1,200°C temperature region. At 1,100°C, the entire opal underwent solid-solid transition to cristobalite. Further ramp of the temperature (1,100-1,200°C) induced formation of mullite. Scanning electron microscopy (SEM) and transmission electron micro-scopy depict the presence of micro-and nanostructures with pores varying from 260 to 650 nm. SEM analysis further determined morphological changes in terms of the pore diameters shrinkage to 120-250 nm in comparison to the larger pores found in the initial material. The results from this investigation improve the understanding of mechanism of silica phase transition and the relevant phase alterations that took place in DE upon calcination temperatures from 500 to 1,200°C.
As important non-timber forest products, wild mushrooms provide diverse benefits, especially nutr... more As important non-timber forest products, wild mushrooms provide diverse benefits, especially nutritional, medicinal and other socioeconomic benefits for ethnic groups located in NorthEast part of the Republic of North Macedonia. Ethno-mycological knowledge of most frequently used fungi was gathered from 32 inhabitants in 12 localities using in-depth interviews during April and November 2019. Each informant was asked about the local name of the fungus, its edibility, methods of preparation, habitat of growth, mode of consumption and medical use. A total of 33 species of wild mushrooms were cited. The results show that knowledge of useful mushrooms differs between two ethnic groups. The Macedonian ethnic group has the highest ethno-mycological expertise compared to Aromanian, which is expressed in their extensive cultural and practical use of fungi. On both ethnic groups man is more involved in harvesting and is the main holders of cultural aspects related to fungi. Despite the presence of edible ectomycorrhizal taxa in the research area, the two ethnic groups only seem to have an interest in saprotrophic taxa.
Streptococcus mutans (S. mutans) has been identified as a major etiologic agent of human dental c... more Streptococcus mutans (S. mutans) has been identified as a major etiologic agent of human dental caries and forms a significant proportion of oral strepto-cocci in carious lesions. This study investigates the correlation of surface properties (effect of contact angle [CA] and free surface energy) on three restorative materials (zirconia, nickel-chromium-molybdenum alloy and composites) used in dental prosthetics with bacterial adhesion to S. mutans. Ten samples of each material (zirconia, nickel-chromium-molybdenum alloy and composites) of 8 mm diameter and 2.5 mm thickness were used. Aqueous CA measurements, free surface energy and bacterial adhesion to the sample surfaces were performed. Bacterial adhesion is determined by planting samples in the blood agar cultures and using an electron microscope (scanning electron microscopy [SEM]). The highest values of bacterial adhesion are found in composites, followed by the metal alloy, while the lowest values are observed in zirconia. Measurements show that zirconia has 17 bacteria; Ni-Cr-Mo alloy has 65, while the composite has 80 bacteria. The composites showed the highest degree of bacterial adhesion, compared to the other investigated materials, which correlates with the free surface energy of the samples (24.31 mJ/m 2 for zirconia, 31.78 mJ/m 2 for Ni-Cr-Mo alloy and 48.82 mJ/m 2 for the composite).
This study is focused on the adsorption of hexavalent chromium ions Cr(VI) using graphene oxide (... more This study is focused on the adsorption of hexavalent chromium ions Cr(VI) using graphene oxide (GO). The GO was prepared by chemical oxidation (Hummers method) of graphite particles. The synthesized GO adsorbent was characterized by Fourier transform infrared spectroscopy and UV-Vis spectroscopy. It was used for the adsorption of Cr(VI) ions. The theoretical calculations based on density functional theory and Monte Carlo calculations were used to explore the preferable adsorption site, interaction type, and adsorption energy of GO toward the Cr(VI) ions. Moreover, the most stable adsorption sites were used to calculate and plot non-covalent interactions. The obtained results are important as they give molecular insights regarding the nature of the interaction between GO surface and the adsorbent Cr(VI) ions. The found adsorption energy of −143.80 kcal/mol is indicative of the high adsorptive tendency of this material. The adsorption capacity value of GO toward these ions is q = 240.361 mg/g.
Contamination of soil by air sediment emitted from coal based thermal power plants is one of the ... more Contamination of soil by air sediment emitted from coal based thermal power plants is one of the basic ecological issue. The aim of this research is to define the impact of production of REK Bitola on the soils from defined microlocality in Pelagonia basin. Chemical, mineralogical and granulometric analyses were performed upon the soil samples. Also basic physical properties of the soil are determined. The chemical composition of the air sediment was also determined. According to the measured values and statistical data of REK Bitola, an average cumulative deposited quantity of air sediment is calculated, as well as the cumulative deposited quantity of trace elements in soil. The deposited air sediment has a negative impact on some of the basic physical and chemical properties of soil, but has no significant effect on the change in porosity and soil properties resulting from it.
Clayey diatomite is the local name for a mixture of diatomaceous earth and clay minerals. It repr... more Clayey diatomite is the local name for a mixture of diatomaceous earth and clay minerals. It represents a greyish, soft, very light, weakly cemented, fine biogenetic sedimentary rock. The studied material is taken from the vicinity of Bitola city (Republic of Macedonia). Here, clayey diatomite was treated up to three temperature intervals (800, 1000 and 1200oC) for a period of 1 hour. The X-ray powder diffraction results indicate the presence of both an amorphous phase and the following crystalline phases: quartz, feldspars (plagioclase), mica (muscovite) and chlorites. The results of SEM analysis revealed skeletons of alga Diatomeae with nano-pores. By thermal treatment of the samples, a gradual change in color as well as higher bulk density and compressive strength was observed. The increase of the temperature, in addition, affected the mineralogical composition and increased the presence of the amorphous phase (aluminasilicate glassy phase). SEM results of the thermally investigated samples depicted morphological changes expressed by shrinkage of the pore diameters in comparison to the initial material. The major and minor constituents were established by chemical analysis revealing the following chemical composition of raw clayey diatomite: SiO2 (63.65 wt%), Al2O3 (11.76 wt%), Fe2O3 (5.93 wt%), MnO (0.13 wt%), TiO2 (0.63 wt%), CaO (1.42 wt%), MgO (2.22 wt%), P2O5 (0.11 wt%), K2O (1.63 wt%), Na2O (0.92 wt%), LOI (11.50 wt%).
Extreme winter time air pollution episodes, fortify public concerns and put focus on air pollutio... more Extreme winter time air pollution episodes, fortify public concerns and put focus on air pollution as most important environmental problem in urban areas throughout the country. However, focused research efforts to derive information about pollution sources and the amount they contribute to ambient air pollution levels, are still missing, thus leaving room for dubious discussions and political, instead of scientifically based abetment strategies. Having in mind importance of proper information on air pollution sources and utilizing the data collected during several different measurement's campaigns performed for city of Skopje, as much extensive additional lab works and modeling efforts, indicative source apportionment analysis was performed for two sites (receptors) within Skopje urban area, one source specific (traffic) and one background site.
Trepel is the local name for a mixture of diatomaceous earth and clay minerals. It represents a g... more Trepel is the local name for a mixture of diatomaceous earth and clay minerals. It represents a greyish, soft, very light, weakly cemented, fine biogenetic sedimentary rock. The studied material is taken from the vicinity of Bitola city (Republic of Macedonia). Here, trepel was treated up to three temperature intervals (800, 1000 and 1200ºC) for a period of 1 hour. The X-ray powder diffraction results indicate the presence of both an amorphous phase and the following crystalline phases: quartz, feldspars (plagioclase), mica (muscovite) and chlorites. The results of SEM analysis revealed skeletons of alga Diatomeae with nano-pores. By thermal treatment of the samples, a gradual change in color as well as higher bulk density and compressive strength was observed. The increase of the temperature, in addition, affected the mineralogical composition and increased the presence of the amorphous phase (aluminasilicate glassy phase). SEM results of the thermally investigated samples depicted morphological changes expressed by shrinkage of the pore diameters in comparison to the initial material. The major and minor constituents were established by chemical analysis revealing the following chemical composition of raw trepel: SiO 2 (63.65 wt%), Al 2 O 3 (11.76 wt%), Fe 2 O 3 (5.93 wt%), MnO (0.13 wt%), TiO 2 (0.63 wt%), CaO (1.42 wt%), MgO (2.22 wt%), P 2 O 5 (0.11 wt%), K 2 O (1.63 wt%), Na 2 O (0.92 wt%), LOI (11.50 wt%).
The physico-mechanical, chemical and mineralogical characteristics of volcanic glass (perlite) fr... more The physico-mechanical, chemical and mineralogical characteristics of volcanic glass (perlite) from the Mariovo region (Macedonia) as well as the mineralogical changes that occur during its thermal treatment were investigated to demonstrate its utilization for industrial use. The native perlite was characterized by chemical analysis, X-ray powder diffraction (XRPD), infrared (IR) spectroscopy, thermal analysis (TGA/DTA), scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), and solid- state NMR. The chemical examination suggests that the perlite represents an acidic volcanic rock with a high percentage of SiO2 (72.45%), high in alkali metal oxides (4.21 wt.% K2O, 3.56 wt.% Na2O), with a loss of ignition 3.54 wt.%. Results from the XRPD indicated major amorphous behaviour, with low amounts of feldspars, quartz, and cristobalite. SEM examinations revealed glassy structure with presence of certain pores (dimensions ranging from 50–100 μm). The determined expansion coefficient was 20 times its original volume. XRPD of expanded perlite compared to the native perlite depicted new intensive peaks of cristobalite. SEM and TEM revealed irregular morphology with broken or ragged edges. On the basis of the chemical and mineralogical composition, the studied perlite is classified as an appropriate material suitable as ceramic flux to lower the sintering temperature.
A B S T R A C T The aim of this study was to test the diatomaceous earth from a deposit near Rožd... more A B S T R A C T The aim of this study was to test the diatomaceous earth from a deposit near Rožden Village (Macedonia) as a raw material for low temperature hydrothermal production of porous ceramics. Hydrothermal synthesis of porous ceramics has been carried out under saturated steam pressure at 130 °C for a period of 1, 2 and 3 h. The objective of this work was to investigate the impact of slaked lime, autoclave curing time, autoclaving temperature and compaction pressure on the compressive strength and porosity of the products. During the hydrothermal synthesis, newly obtained calcium silicate hydrate dominates which give positive effect to the compressive strength and product porosity confirmed by X-ray powder diffraction. Moreover, a calcite was also evidenced by FTIR spectroscopy whose presence additionally increases the compressive strength of the hydrothermal products. The products obtained during the low-temperature hydrothermal reaction are classified as light porous ceramics with bulk density ranging from 0.71 to 0.91 g/cm 3 and compressive strength within 14.7–19.4 MPa.
During the treatment process of drinking water, chlorine reacts with the organic matter present i... more During the treatment process of drinking water, chlorine reacts with the organic matter present in water and forms various disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). The high content of THMs in the drinking water may be cancerogenic for humans and this has resulted in significant scientific and public concern. The aim of this paper was to determine the factors that have an impact on THM formation in the drinking water in the city of Tetova for the autumn season 2011. Results of this research have shown that during high contact time, temperature, pH and chlorine dosage, more THMs were formed. Based on the examined factors, results show that contact time, pH and the chlorine dosage were crucial and had a significant role in THM formation. The presence of THMs was determined with UV-VIS spectrophotometry. This was the first study that researched the factors that impact the formation of THMs in the drinking water in the Republic of Macedonia. The study results match conclusions reached by previous research in the field.
Water is the most essential product that is consumed by humans, which must be prevented from dete... more Water is the most essential product that is consumed by humans, which must be prevented from deterioration in quality. The quality of drinking water becomes even more important as water borne diseases spread through water. For this purpose, we assess the quality of drinking water in the city of Kumanova with some physico-chemical parameters, which have a significant role in determining the potability of drinking water. The obtained results were compared with Macedonian standards as well as with those set by the WHO and the EU. In this research, parameters such as temperature, turbidity, RC, pH, EC, TRAE, TDS, COD, nitrites, nitrates, ammonia and chlorides were found to be within the permissible limits, while residual chlorine in one case were found to be below lower than the recommended limit. Finally, the Drinking Water Quality Index (DWQI) developed by Canadian Council of Ministers of the Environment for five sample points is calculated. It has been found that drinking water in the 2011 spring season was of a Excellent category (average value of DWQI = 95.21) and suitable for drinking. We recommend that the relevant municipal authorities make regular and proper amount disinfection of drinking water, as there is no compromise that can be made when it comes to the drinking water.
In this paper are shown results of the
physical-chemical and mineralogical-petrographic
examinati... more In this paper are shown results of the physical-chemical and mineralogical-petrographic examinations of trepel from Brod-Gneotino, Bitola region, Republic of Macedonia. According to the scanning electronic microscopy (SEM), the infra-red (IR) and powder X-ray (XRPD) examinations, it was determined that examined trepel is composed mainly of opal (of biogenetic origin) as well as quartz, illite – hydromicas, feldspars (plagioclases, feldspars), and chlorites of minor importance. DTА and TGA examinations show results which are in line with the determined mineralogical composition of the sample. With these examinations it is concluded presence of organic matter in the sample. As result of these examinations it can be concluded that this raw material (trepel, natural mixture of diatomite and clay minerals) can be used as raw material for production of ceramic products (based on classical and hydrothermal technology), for synthesis of zeolites, as absorbent for cleaning of raw industrial waters.
The formation of carcinogenic trihalomethanes (THMs) in the process of water disinfection by chlo... more The formation of carcinogenic trihalomethanes (THMs) in the process of water disinfection by chlorine has raised concerns in the scientific community as well as in the public opinion. This study aims to determine the concentration of THMs in Tetova's drinking water during the autumn season and compare it with the regulation in the Republic of Macedonia, the European Union and the World Health Organization. To this end, we have used the UV-VIS spectrophotometric method based on Fujiwara's reaction. The THMs concentration was measured in fifteen different locations in September, October and November 2011. The results indicate that the seasonal variation is below the critical values stipulated in the state, EU and WHO regulations (seasonal average 22.22 ± 12.06 μg/L). This study is the first of its kind on THMs in the Republic of Macedonia. In conclusion, it can be inferred that the concentration of THMs in the drinking water of Tetova is not hazardous to human health.
Water is the most essential product that is consumed by humans, which must be prevented from dete... more Water is the most essential product that is consumed by humans, which must be prevented from deterioration in quality. The quality of drinking water becomes even more important as water borne diseases spread through water. For this purpose, we assess the quality of drinking water in the city of Tetova with some physico-chemical parameters, which have a significant role in determining the potability of drinking water. The obtained results were compared with Macedonian standards as well as with those set by the WHO and the EU. In this research, parameters such as temperature, pH, EC, TRAE, TDS, COD, TOC, DOC, nitrates and chlorides were found to be within the permissible limits, while turbidity and residual chlorine in some cases were found to be below ore above the recommended limit. Finally, the Drinking Water Quality Index (DWQI) developed by Canadian Council of Ministers of the Environment for fifteen sample points is calculated. It has been found that drinking water in the 2011 a...
Trepel is the local name for a mixture of diatomaceous earth and
clay minerals. It represents a g... more Trepel is the local name for a mixture of diatomaceous earth and clay minerals. It represents a greyish, soft, very light, weakly cemented, fine biogenetic sedimentary rock. The studied material is taken from the vicinity of Bitola city (Republic of Macedonia). Here, clayey diatomite was treated up to three temperature intervals (800, 1000 and 1200oC) for a period of 1 hour. The X-ray powder diffraction results indicate the presence of both an amorphous phase and the following crystalline phases: quartz, feldspars (plagioclase), mica (muscovite) and chlorites. The results of SEM analysis revealed skeletons of alga Diatomeae with nano-pores. By thermal treatment of the samples, a gradual change in color as well as higher bulk density and compressive strength was observed. The increase of the temperature, in addition, affected the mineralogical composition and increased the presence of the amorphous phase (aluminasilicate glassy phase). SEM results of the thermally investigated samples depicted morphological changes expressed by shrinkage of the pore diameters in comparison to the initial material. The major and minor constituents were established by chemical analysis revealing the following chemical composition of raw clayey diatomite: SiO2 (63.65 wt%), Al2O3 (11.76 wt%), Fe2O3 (5.93 wt%), MnO (0.13 wt%), TiO2 (0.63 wt%), CaO (1.42 wt%), MgO (2.22 wt%), P2O5 (0.11 wt%), K2O (1.63 wt%), Na2O (0.92 wt%), LOI (11.50 wt%).
The aim of this research is to obtain light ceramic products from the reaction of diatomite with ... more The aim of this research is to obtain light ceramic products from the reaction of diatomite with calcium hydroxide and trepel with calcium hydroxide. Diatomite is a loose, soft, porous, weakly bound rock with white to grayish color. Trepel is a natural mixture of diatomite and clay minerals. During the hydrothermal reaction of diatomite and trepel with calcium hydroxide new phases are formed. The newly formed phases are calcium silicate hydrates. The products obtained after the hydrothermal reaction are lightweight materials. Probes obtained from mixtures of trepel and calcium hydroxide have bulk density 0.85 g/cm 3 whereas the probes with diatomite and calcium hydroxide have bulk density 0.91 g/cm 3. The compressive strength of probes with trepel is 22.5 MPa while the compressive strength of probes with diatomite is 19.4 MPa.
Trepel is form of silica (SiO2) derived either from thedecomposition or alterations of ... more Trepel is form of silica (SiO2) derived either from thedecomposition or alterations of chert or as a residual product fromthe decomposition of a highly siliceous limestone.Diatomite or diatomaceous earth (also known as tripolite,kieselguhr, infusorial earth) is a hydrous or opalescent form of silica[5]. Trepelis a natural mixture of diatomite and clay minerals [6]. It’s a typical sedimentary rock of biogenetic origin, with greyish-white color,weakly bound, soft (1-2 by Mohs) and very light, porousmaterial [7]. Trepel is a suitable raw material for production of ceramic products, for synthesis of zeolites, as absorbent for cleaning of raw industrial waters etc [8-12]. In this paper the aim is to use trepel as raw material for production of porous ceramic products.
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produ... more Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced during the process of rapidly cooling of the extruded felsic lava from a volcano manifesting thereby minimal crystal growth. The subject obsidian was found as impurity in the perlite from the Mariovo region. It is found in tiny black crystals with irregular shapes. The XRPD analysis shows predominantly amorphous glassy phase with minor peaks of the following minerals: anorthite, muscovite, quartz, cristobalite and feldspars. SEM examinations confirmed the glassy structure with presence of certain phases that are most likely due to the clay impurities.
Uploads
Papers by Arianit Reka
physical-chemical and mineralogical-petrographic
examinations of trepel from Brod-Gneotino, Bitola
region, Republic of Macedonia. According to the
scanning electronic microscopy (SEM), the infra-red (IR)
and powder X-ray (XRPD) examinations, it was
determined that examined trepel is composed mainly of
opal (of biogenetic origin) as well as quartz, illite –
hydromicas, feldspars (plagioclases, feldspars), and
chlorites of minor importance. DTА and TGA
examinations show results which are in line with the
determined mineralogical composition of the sample.
With these examinations it is concluded presence of
organic matter in the sample. As result of these
examinations it can be concluded that this raw material
(trepel, natural mixture of diatomite and clay minerals)
can be used as raw material for production of ceramic
products (based on classical and hydrothermal
technology), for synthesis of zeolites, as absorbent for
cleaning of raw industrial waters.
physical-chemical and mineralogical-petrographic
examinations of trepel from Brod-Gneotino, Bitola
region, Republic of Macedonia. According to the
scanning electronic microscopy (SEM), the infra-red (IR)
and powder X-ray (XRPD) examinations, it was
determined that examined trepel is composed mainly of
opal (of biogenetic origin) as well as quartz, illite –
hydromicas, feldspars (plagioclases, feldspars), and
chlorites of minor importance. DTА and TGA
examinations show results which are in line with the
determined mineralogical composition of the sample.
With these examinations it is concluded presence of
organic matter in the sample. As result of these
examinations it can be concluded that this raw material
(trepel, natural mixture of diatomite and clay minerals)
can be used as raw material for production of ceramic
products (based on classical and hydrothermal
technology), for synthesis of zeolites, as absorbent for
cleaning of raw industrial waters.
clay minerals. It represents a greyish, soft, very light, weakly
cemented, fine biogenetic sedimentary rock. The studied
material is taken from the vicinity of Bitola city (Republic of
Macedonia). Here, clayey diatomite was treated up to three
temperature intervals (800, 1000 and 1200oC) for a period of 1
hour. The X-ray powder diffraction results indicate the presence
of both an amorphous phase and the following crystalline
phases: quartz, feldspars (plagioclase), mica (muscovite) and
chlorites. The results of SEM analysis revealed skeletons of alga
Diatomeae with nano-pores. By thermal treatment of the
samples, a gradual change in color as well as higher bulk density
and compressive strength was observed. The increase of the
temperature, in addition, affected the mineralogical composition
and increased the presence of the amorphous phase
(aluminasilicate glassy phase). SEM results of the thermally
investigated samples depicted morphological changes expressed
by shrinkage of the pore diameters in comparison to the initial
material. The major and minor constituents were established by
chemical analysis revealing the following chemical composition
of raw clayey diatomite: SiO2 (63.65 wt%), Al2O3 (11.76 wt%),
Fe2O3 (5.93 wt%), MnO (0.13 wt%), TiO2 (0.63 wt%), CaO
(1.42 wt%), MgO (2.22 wt%), P2O5 (0.11 wt%), K2O (1.63
wt%), Na2O (0.92 wt%), LOI (11.50 wt%).