Blagica Cekova’s scientific contributions

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Publications (5)


Table 3 .
APPLICATION OF ZEOFIT AND ZEOLIT AS ABSORPTION OF HEAVY METALS IN SOIL PLANTED WITH VEGETABLES
  • Article
  • Full-text available

November 2014

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828 Reads

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Blagica Cekova

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Katerina Atkoska

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Zeofit as ecological product is new to the Macedonian market, having a wide range of functioning. According to its chemical composition it is a natural raw material created through the opalization and is part of the group of zeolitizes volcanic rocks. The zeofit produces extraordinary results in the area of fruit-growing, stock-breeding, market gardening etc. Zeolites are natural or synthetic micro porous hydrated aluminosilicates with open 3D crystal structure composed of aluminum, silicon and oxygen atoms whose pores are filled with molecular water. In our tests was used synthetic zeolite type 4A derived from water glass. Besides zeolite type 4A we also used the natural material known as zeofit. Zeofit is a vulcanic rock with zeolitic structure. Zeolites are characterized by large ion changing power of ions of heavy metals found in soil also known as soil additives. The zeofit produces extraordinary results in the area of plants-growing, market gardening etc. It plays a role in increasing the plants’ resistance against high and low temperatures, increasing the yield, protecting against diseases and vermin in plants . One of the important characteristics of this raw material is the fact that it preserves moisture in its contents, which is made of use in its application since it enables the root to use part of the nutrients in the soil during drought periods, thus improving the nutrition of the plants, contributing to a better development of the root system, thereby intensifying growth and the fertility itself of the plants. The concentration of elements: Cr(III),arsenic, mercury and iron were determined using atomic absorption spectroscopy (AAS). The results of the research will be presented in tables and graphics. Also in this paper will be provided chemical analyzes of the soil, zeofit and zeolite type 4A.

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Figure 1. DTA/TGA analysis of amorphous ZrO 2 powder 
Figure 3. X-ray diffractogram of partially stabilized ZrO 2 , with 3 mol % Y 2 O 3 , sintered at 1300 ° C (3 hrs) 
SPECIAL CERAMICS BASED ON PARTIALLY STABILIZED ZIRCONIUM DIOXIDE

March 2014

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228 Reads

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1 Citation

The aim of this research was to get a product, partially stabilized zirconia. The powders of partially stabilized zirconia were prepared from zirconium tetrachloride and hydrated yttrium chloride precursors using a precipitation method. After drying and calcination, the powders were examined using X-ray diffraction. X-ray analysis shows that the powder dried at 120ºC is in amorphous phase, while upon calcination at 800ºC, it represents a partially stabilized zirconia with a presence of cubic and monoclinic phases. The basic purpose in preparing such mixtures was to obtain a finally-dispersed and homogenous powder which could be sintered at relatively low temperatures. From the super fine powder were prepared probes which were then dried at 120ºC and sintered at temperature of 1300ºC, for a period of 1 and 3 hours. Further analysis of the sintered probes showed density of 4.37 and 4.46 g/cm3. The X-ray analyses show that these probes are represented with 70% of cubic phase and 30% of monoclinic phase, thus concluding the partial stabilized zirconia. Probes sintered at 1300ºC were tested to the resistance to the thermal shocks. The probes were heated at 1300ºC, for the time of 5 minutes and after that cooled at 20ºC, for the same time. All probes endured 40 thermal shocks without appearance of cracks. The probes don’t change their phase content, and have high thermal stability. Key words: precipitation, sintering, partial stabilized zirconia, thermal shock


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Structural examinations of natural raw materials pumice and trepel from Republic of Macedonia

December 2013

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685 Reads

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21 Citations

The aim of this paper is to present the physic-mechanical, chemical and mineralogical-petrographic examinations of the pumice and trepel. The pumice is from deposit site called Bojanciste, near Kavadarci, and the trepel deposit is from Suvodol near Bitola, Republic of Macedonia. The mineralogical-petrographic examinations of the pumice and pumicite have shown that the main component of the pumice and pumicite it is the volcanic glass, while in the crystal phase there is presence of albit, oligoclass, anorthit, microklin and in small quantities presence of quartz, biotit and augit. The examinations of the trepel have shown that it is a sedimentary rock (of biogenic origin) with greyish-white colour, very light and soft, porous and with fine to superfine grained structure. The trepel is composed mainly of opal as well as quartz, feldspar, illite and chlorites.


Figure 1. Adsorption isotherm with steam – Langmuir isotherm of zeolite obtained within 2 hours 
Figure 4. Linear form of the isotherm of zeolite obtained within 2 hours 
Figure 5. Linear form of the isotherm of zeolite obtained within 4 hours 
Figure 6. Linear form of the isotherm of zeolite obtained within 6 hours 
THE ADSORPTION CHARACTER OF ZEOLITES, TYPE 4A, OBTAINED BY NATURAL RAW TREPEL BITOLA R. MACEDONIA

October 2013

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223 Reads

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1 Citation

Zeolites as micropore adsorbents are characterized by a pore diameter of less than 1.5 nm. The basic characteristic of the micropore absorbers is the emergence of the molecular sieves action which is expressed with the absorption to specific molecules, the diameter of which is less than the open micropore. This way, the zeolites appear to be typical micropore adsorbents. The process of permeating molecules, which are adsorbed through the fringes in the gaps in the zeolites has a complex physical and chemical nature. In order to describe this process, specific notions are used such as an effective, critical diameter of the shafts, and a critical diameter of the molecules that are adsorbed. In our case, the adsorption properties of the zeolites of the 4A type, with a static gravimetric method, are determined. For the determination of the specific surface, the LANGMUIR equation is applied. The designated specific areas of the zeolites that are synthesized for 2, 4 and 6 hours are: S = 163m2/g, S = 197m2/g, S = 239m2/g. The results are shown graphically. The designated specific areas define the application of the zeolites as adsorbents used on the natural raw material - trepel - Bitola for the synthesis of zeolites from the type 4A. Key words: Trepel, adsorption, LANGMUIR - equation, the specific surface area.


Preliminary Examinations from Wastewater Treatment by Zeolites from Waste Materials

July 2013

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140 Reads

Zeolitite as an independent group of natural hidroaluminosillicates of alkalines and alkaline earth elements. Because of their unique porous properties, zeolites are used in a variety of applications with a global market. In the western world, major uses are in petrochemical cracking, ion - exchange (water softening and purification), and in the separation and removal of gases and solvents. In our case, the synthetic zeolite 4A will be presented in detail, with its application for treatment of wastewater, which has ion change capability, micropore structure and high capacity of adsorption, treatment of water and it allows complete removal of ions from heavy metals. Key words: zeolitite 4A, water, ion, adsorption.

Citations (2)


... Infra-red spectroscopic examinations of trepel are shown in Fig 6. , strongly H-bonded hydroxyl groups and OHhydroxyl groups. As result of these examinations, it is concluded that trepel can find application in the industry of construction materials [4][5][6][7]. ...

Reference:

Physical-Chemical and Mineralogical-Petrographic Examinations of Trepel from Republic of Macedonia
THE ADSORPTION CHARACTER OF ZEOLITES, TYPE 4A, OBTAINED BY NATURAL RAW TREPEL BITOLA R. MACEDONIA

... These surface complexes can subsequently undergo reactions and transformations, resulting in the conversion of ammonia to other nitrogen species. Thirdly, reactions between ammonia and the pumice and brick present in the lower layers may be enhanced due to increased reaction times in the presence of saturation zones further promoting adsorption, ion exchange and chemical reactions as represented in Eq. (4), (5) and (6), respectively [33,39]. ...

Structural examinations of natural raw materials pumice and trepel from Republic of Macedonia