Blagoj Pavlovski’s research while affiliated with Saints Cyril and Methodius University of Skopje and other places

What is this page?


This page lists works of an author who doesn't have a ResearchGate profile or hasn't added the works to their profile yet. It is automatically generated from public (personal) data to further our legitimate goal of comprehensive and accurate scientific recordkeeping. If you are this author and want this page removed, please let us know.

Publications (22)


Fabrication of Ceramic Monoliths from Diatomaceous Earth: Effects of Calcination Temperature on Silica Phase Transformation
  • Article
  • Full-text available

December 2022

·

178 Reads

Science of Sintering

·

·

·

[...]

·

The raw diatomaceous earth from the vicinity of Bitola (North Macedonia) showed low bulk density (0.61-0.69 g/cm3), high-water absorption (75-81%) and porosity (66- 72%). The chemical composition was determined with ICP-MS, revealing the following results for the diatomaceous earth: SiO2 (63.69 wt%), Al2O3 (11.79 wt%), Fe2O3 (5.95 wt%), MnO (0.15 wt%), TiO2 (0.65 wt%), CaO (1.51 wt%), MgO (2.24 wt%), P2O5 (0.13 wt%), K2O (1.64 wt%), Na2O (0.93 wt%), LOI (11.21 wt%). XRPD data of the examined sample of clayey diatomite mainly depicted crystalline behavior with a small presence of amorphous phase. The crystalline mineral phases mainly comprise: silica (quartz), feldspars (plagioclase), mica (muscovite), chlorites and dolomite. SEM and TEM results show cased presence of micro- and nanostructures with pores ranging from 250 to 600 nm. The clayey diatomite was sintered at three temperatures (900, 1000 and 1100ºC) for a period of 1 h. XRPD of the sintered samples at 1100ºC showed certain thermal stability and formation of new phases (mullite and tridymite) that makes the analyzed diatomaceous earth suitable for production of various types of ceramic, construction and thermal insulating materials.

Download

Adsorption of Cr(VI) ions from aqueous solutions by diatomite and clayey diatomite

January 2022

·

95 Reads

·

4 Citations

This paper compares the percentage of removal of Cr(VI) ions from aqueous solutions with pure diatomite and clayey diatomite. To characterize the adsorbents, the following analyses were performed: classical silicate chemical, differential thermal and thermogravimetric, X-ray dispersive, Fourier transform infrared, scanning electron microscopy, and transmission electron microscopy. The Brunauer–Emmett–Teller model (as, m2/g) was used to determine the specific area. Atomic absorption spectrophotometric method and UV/Vis spectrophotometric analysis were used to determine the concentration before and after the Cr(VI) adsorption process. A series of experiments was performed to determine the point of zero charge. The influence of pH was also examined, and we obtained the best results at low pH values. At an initial concentration of Cr(VI) ions of 0.5 mg/L and a pH equal to 2, the best results were shown by the clayey diatomite, where the percentage of removal is 100%, while the diatomite is 28%. So the used natural raw material clayey diatomite at low cost is an effective adsorbent for the removal of Cr(VI) ions.


CHARACTERIZATION OF THE CALCITE RAW MATERIAL FROM THE MICROLOCALITIES OF SUŠIČKI MOST AND GORNA BANJICA NEAR GOSTIVAR, REPUBLIC OF NORTH MACEDONIA

December 2021

·

33 Reads

Geologica Macedonica

The aim of this research is characterization of the calcite raw material from two microlocalities: Sušički Most and Gorna Banjica near Gostivar. The properties of the calcite raw materials were defined applying complex examinations. XRD analysis determined the presence of calcite and dolomite as basic mineral phases, which was confirmed by optical transmission microscopy. The dominant content of CaCO3 was defined by chemical analysis. ICP-AES analysis confirmed a high degree of purity of the raw materials. DTA/TGA correlate with other analyses. Some basic physical properties of the raw materials were also determined. Additionally, the parameters of the mechan­ical preparation have been optimized. According to the presented results, the calcite materials which have very similar composition and approximately the same properties have a wide spectrum of application possibilities.


Fig. 1. Geographical map of North Macedonia that pinpoints the diatomite deposit in Vitačevo (plateau near Kavadarci).
Fig. 5. SEM of diatomite. A) Rod-like diatoms with dimensions 25-35 microns length and 8-12 microns width. B) Close up view of rod-like diatoms. C) Various fragments of diatoms and lepispheres of silica. D) Fragments of diatoms and flake shape frustule in the middle
Fig. 6. Secondary electron image photos of diatomite
Fig. 7. TEM of diatomite show arrangement and details of the porous structure and the amorphous glassy mass
Fig. 8. DTA/TGA of diatomite

+1

Diatomite – evaluation of physico-mechanical, chemical, mineralogical and thermal properties

June 2021

·

957 Reads

·

4 Citations

Geologica Macedonica


Diatomaceous Earth: Characterization, thermal modification, and application

April 2021

·

991 Reads

·

54 Citations

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/cm3, total porosity of 61–63%, and specific gravity of 2.25 g/cm3. The chemical composition is as follows: SiO2, 86.03; Al2O3, 3.01; Fe2O3, 2.89; MnO, 0.06; TiO2, 0.20; CaO, 0.76; MgO, 0.28; K2O, 0.69; Na2O, 0.19; P2O5, 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, muscovite, 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 microscopy 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.


Removal of Chromium(VI) from Aqueous Solution by Clayey Diatomite: Kinetic and Equilibrium Study

March 2021

·

115 Reads

·

4 Citations

The clayey diatomite from the village of Suvodol (Bitola region) used in this research has shown to be a very effective and efficient natural material for the removal of Cr(VI) ions from aqueous solutions. The adsorption of Cr(VI) ions onto a clayey diatomite was shown to occur very efficiently with 96.7%. During the experiments the effect of operating parameters, such as amount of adsorbent (0.5–5.5 g/l), initial adsorbate concentration (0.3, 0.4, 0.5, and 0.6 mg/l), and time of adsorption (5–180 min) at pH of the solution 3, was examined. It was found that 2.5 g/l is optimal adsorbent dosage for maximal removal of Cr(VI) ions. Atomic absorption spectrophotometric (AAC) method and UV-Vis spectrophotometric analysis are used for quantitative monitoring of the dynamics of the studied system regarding the presence of Cr(VI) ions in the model solutions. The effect of the initial concentration and quantity of adsorbent is examined, in order to determine the conditions that enable maximum removal of Cr(VI) ions with clayey diatomite. For the purpose of modeling the equilibrium, the kinetics, and dynamics of the tested system of the process of elimination of Cr(VI) ions with the raw material in different operating conditions, MATLAB/Curve Fitting Toolbox was conducted.


Effect of Thermal Treatment of Clayey Diatomite at Temperature Range 800- 1200°C

May 2020

·

339 Reads

·

4 Citations

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%).




Effect Of Thermal Treatment Of Trepel At Temperature Range 800-1200˚C

December 2019

·

435 Reads

·

14 Citations

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 1200 C) 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%).


Citations (14)


... It represents a mixture of diatomite and clay minerals. It constitutes a biogenetic rock; grayish, soft, very light, weakly cemented, finely opal sedimentary rock [11][12][13][14][15][16][17][18][19]. ...

Reference:

Fabrication of Ceramic Monoliths from Diatomaceous Earth: Effects of Calcination Temperature on Silica Phase Transformation
TREPEL -A PECULIAR SEDIMENTARY ROCK OF BIOGENETIC ORIGIN FROM THE SUVODOL VILLAGE, BITOLA, R. MACEDONIA

... Under alkaline conditions (pH > 7.0), the hematite surface is negatively charged, leading to a reduction in the adsorption efficiency of A(III) (Han et al., 2022). The negative charge of the mineral surface results in a low adsorption efficiency of As(III) on bentonite and diatomite (Memedi et al., 2022). ...

Adsorption of Cr(VI) ions from aqueous solutions by diatomite and clayey diatomite
  • Citing Chapter
  • January 2022

... It represents a mixture of diatomite and clay minerals. It constitutes a biogenetic rock; grayish, soft, very light, weakly cemented, finely opal sedimentary rock [11][12][13][14][15][16][17][18][19]. ...

Diatomite – evaluation of physico-mechanical, chemical, mineralogical and thermal properties

Geologica Macedonica

... In addition, it also served as a buffering agent to control the pH of the formulation after mixing with water. On the other hand, diatomaceous earth and talc were incorporated into the formulation for their absorption properties, targeting dirt and facial sebum [84,85]. Different weight ratios of diatomaceous earth to talc (55:22, 65:12, and 75:2) were used in the formulations of blank powder for facial peel-off gel masks. ...

Diatomaceous Earth: Characterization, thermal modification, and application

... This may account for maximum Cr(VI) adsorption values on DM and TMD that were obtained at pH 3. This result is in agreement with previous reports (Memedi et al. 2021). Also, Fe 3 O 4 functionalization of TMD does not significantly change the pH of MDM for maximum Cr(VI) adsorption, allowing maximum adsorption performance at a pH of 3. Similar results were reported for Cr(VI) removal using activated carbon-attapulgite clay composite (Hlungwane et al. 2018), clay-biochar composite (Wang et al. 2019) and DM supported by zero-valent iron nanoparticle (Zhang et al. 2019). ...

Removal of Chromium(VI) from Aqueous Solution by Clayey Diatomite: Kinetic and Equilibrium Study
  • Citing Chapter
  • March 2021

... Studies of diatomite with an increased clay mineral content have shown that heat treatment at 1000 °C causes the formation of mullite typical of this temperature. Diatomites contaminated with clay minerals, which are referred to as "diatomaceous clay", have the potential as a basic raw material for the production of various ceramic materials, such as structural and thermal materials (various types of zeolites, water glass, amorphous SiO2, etc.) [11,12]. An interesting application of sintered diatomite is as orthopaedic magnesium implants [13]. ...

Effect of Thermal Treatment of Clayey Diatomite at Temperature Range 800- 1200°C

... The Republic of North Macedonia is rich in inorganic materials with a wide range of potential application as adsorbents, including trepel [4,5], diatomaceous earth [6,7], perlite [8] and zeolite-bearing tuff [9], but using sludge-based activated carbon as adsorbent also achieves the goal of waste utilization. In the past few years, the European Union promoted ecological management of such wastes by introducing directives regarding sewage sludge management and therefore classical methods, such as storage, are being replaced by methods leading to waste stabilization and safe recycling [10] The aim of this paper is preparation of activated carbon from sewage sludge from Volkovo wastewater treatment plant in Skopje, the Republic of North Macedonia, its characterization, and possibility of using the material as adsorbent. ...

Effect Of Thermal Treatment Of Trepel At Temperature Range 800-1200˚C

... Perlite (and pumice stone) are natural resources, amorphous glasses of volcanic origin, which have the unusual property of great expansion by heating at 850-1100 • C. The bound water content trapped in its structure vaporizes and causes 7-16-fold expansion to its original volume. The bulk densities of the expanded perlite and pumice are only 30-150 kg·m −3 [1,2]. Their composites with gypsum and cement are superabsorbents, which means they have extreme absorption capacities for water or other liquids [3,4]. ...

Chemical, mineralogical and structural features of native and expanded perlite from Macedonia

Geologia Croatica

... Diatomite, or diatomaceous earth, is of sedimentary origin and consists mainly of an accumulation of the skeletons formed as a protective covering of the diatoms (Ivanov and Belyakov 2008;Inglethorpe 1993;Ilia, Stamatakis, and Perraki 2009). The skeletons are essentially eukaryotic unicellular microalgae composed of amorphous hydrated or opaline silica, while alumina originates from clay minerals such as illite, kaolinite, and minerals from micas group (muscovite), and organic matters (Reka, Pavlovski, and Makreski 2017). When heated at high temperatures, the diatomite undergoes a series of reactions, forming mullite, cristobalite, and impurity-containing silica-rich liquid phase. ...

New optimized method for low-temperature hydrothermal production of porous ceramics using diatomaceous earth
  • Citing Article
  • June 2017

Ceramics International

... It represents a mixture of diatomite and clay minerals. It constitutes a biogenetic rock; grayish, soft, very light, weakly cemented, finely opal sedimentary rock [11][12][13][14][15][16][17][18][19]. ...

Physical-Chemical and Mineralogical-Petrographic Examinations of Trepel from Republic of Macedonia