Papers by Efrosini Kokalari
Global NEST International Conference on Environmental Science & Technology
In recent years finding environmentally friendly and affordable sources to mitigate corrosion has... more In recent years finding environmentally friendly and affordable sources to mitigate corrosion has become demanding in many industries due to the increased awareness related to environmental issues. Due to their readily availability, biodegradability, low toxicity and relatively low cost, plant extracts have been shown to be an effective alternative for corrosion protection of different metals in various environments. This work reports on the performance of the alcoholic extract of Cornus sanguinea leaves (CSL) as a green corrosion inhibitor for carbon steel immersed in 1 M HCl solution. Weight loss and potentiodynamic polarization techniques have been used to investigate the corrosion rate of the carbon steel samples immersed in the 1 M HCl solution with and without the addition of various concentrations of the CSL alcoholic extract. The addition of 250 mg/L CSL alcoholic extract resulted in the highest corrosion inhibition efficiency (i.e. 91.68%) at 25 ºC. The polarization curves ...
Asian Journal of Chemistry, 2013
One of the most common and useful reactions to make polymers is free radical polymerization. This... more One of the most common and useful reactions to make polymers is free radical polymerization. This polymerization is used to make polymers from monomers containing carboncarbon double bonds such as acrylates, vinyl monomers, allylic monomers etc. Some acrylate monomers have been used by Voss et al. 1 and Wouters et al. 2 to study the effect of pendant functionality on the thermal and physical properties of polymers obtained by the reversible addition-fragmentation chain-transfer (RAFT) polymerization. The methacrylate copolymers studied by these authors contained n-butyl-methacrylate and methyl methacrylate (MMA) to control the glass transition temperature of the final polymer and a minor fraction of one of the monomers displayed in Fig. 1. These monomers were chosen for their particular interacting capabilities (H-bonding or π-π interaction). In this study, the authors assumed that the distribution of comonomers in the RAFT polymers is random and nevertheless no further investigation was done to prove this supposition. We extended the work of Voss et al. 1 and Wouters et al. 2 by performing free radical copolymerization of monomers 3 and 5 with methyl methacrylate and butyl-methacrylate with the aim to estimate the reactivity ratios, giving though insight in the monomer distribution in the polymer chain. The copolymerizations of monomers 3 and 5 with both methyl methacrylate and butyl methacrylate were carried out. Subsequently, the reactivy ratios are determined and the compositions of the present polymers are presented. 1 H NMR spectroscopy is employed to study the polymer composition.
Asian Journal of Chemistry, 2013
It is well known that the concrete mud particularly is not corrosive for steel bars. The concrete... more It is well known that the concrete mud particularly is not corrosive for steel bars. The concrete cracks, are responsible for penetration of aggressive media (industrial coastal areas) into the reinforced bars. Use of corrosion protection methods friendly with environment, is another priority of all scientific opinions related with corrosion sciences. This is very important to choose cheap and safely handled compounds, to be used as corrosion inhibitors. Steel is one of the most important engineering and construction materials in the world. Corrosion problems have received a considerable attention because of their attack on material. Many efforts have been made to develop a corrosion inhibition process to prolong the life of existing structures and minimize corrosion damages 1. At industrial coastal areas, penetration of the acidic media on steel bars, through chemical or mechanical cracks of concrete, caused corrosion of them 2-6. Use of inhibitors is one of the most practical methods for corrosion protection. Some inhibitors protect the environment from corrosive pollution, but are unacceptable for it. Beside the mitigation of chemical and mechanical cracks, use of green inhibitors, non-toxic substances (probably extracted by plants), will be a friendly choice for both corrosion and environment protection. Early publication by Abdallah 7 using guar-gum as a good inhibitor of acidic environment in presence of chloride (Cl-) ions 7. This has been
International Journal of Ecosystems and Ecology Science (IJEES), 2017
Proceedings of the 8th World Congress on Mechanical, Chemical, and Material Engineering
The use of green inhibitors as environmentally safe corrosion inhibitors for metal and alloys has... more The use of green inhibitors as environmentally safe corrosion inhibitors for metal and alloys has, in recent times, received attention from researches. The extract of pineapple crown was studied as an inhibitor in 1M H 2 SO 4 and 1 M HCl, with different concentration of pineapple extract, for iron B 500. The corrosion inhibition efficiency was investigated by using the weight loss method. The inhibition efficiency increases with the increase of the inhibitor concentration to attain 98.1 % at 4 g/L of pineapple crown extract. Based on the obtained results, pineapple crown extract reacts as a good inhibitor in aggressive media.
Kemija u Industriji, 2012
Mitigation of corrosion impact on environment is an important step in environmental protection. U... more Mitigation of corrosion impact on environment is an important step in environmental protection. Use of environmentally friendly corrosion protection methods is very important. It is smart to choose cheap and safe to handle compounds as corrosion inhibitors. The use of green inhibitors (extracted inexpensively, from the seed endosperm of some Leguminosae plants), and investigation of their efficiency in corrosion protection is the aim of this study. As green inhibitor one kind of polysaccharides (galactomannan) from locust bean gum (also known as carob gum, carob bean gum) extracted from the seed of carob tree is used. Corrosion protection efficiency of these extracted green inhibitors was tested for carbon steel marked as: steel 39, steel 44, and iron B 500 (usually applied as reinforcing bars to concrete). Sulfuric acid solution in the presence of chloride ions was used as corrosion media. The composition of corrosion acid media used was 1 mol L–1 H2SO4 and 10–3 mol L–1 Cl– (in the...
Proceedings of the 7th World Congress on Mechanical, Chemical, and Material Engineering, 2021
The durability degradation of reinforced concrete structures is one of the biggest problems hinde... more The durability degradation of reinforced concrete structures is one of the biggest problems hindering the breakthrough in engineering and has attracted a great deal of attention in the field of civil engineering. Corrosion issues of internal steel reinforcement have become a top priority in durability treatment since they seriously threaten the durability and sustainability of the structure. Migrating corrosion inhibitors (MCIs) are a good alternative to prevent or control reinforcing steel corrosion because of their moderate cost and easy application compared with other preventive methods. Our study concerns the investigation of the protective effect of MCI; different concentrations of butanol-1 amin-2 refer 1g/L lysine. Materials under investigation are two kind of low allow carbon steel marked as: Steel 39, Steel 44. The corrosion media is sulfuric acid in presence of chloride ions, in form of NaCl (H2SO4 1M + Cl 10M). Potentiodynamic polarization method is used for inhibitor eff...
Mitigation of corrosion impact on environment is an important step in environmental protection. U... more Mitigation of corrosion impact on environment is an important step in environmental protection. Use of environmentally friendly corrosion protection methods is very important. It is smart to choose cheap and safe to handle compounds as corrosion inhibitors. The use of green inhibitors (extracted inexpensively, from the seed endosperm of some Leguminosae plants), and investigation of their efficiency in corrosion protection is the aim of this study. As green inhibitor one kind of polysaccharides (galactomannan) from locust bean gum (also known as carob gum, carob bean gum) extracted from the seed of carob tree is used. Corrosion protection efficiency of these extracted green inhibitors was tested for carbon steel marked as: steel 39, steel 44, and iron B 500 (usually applied as reinforcing bars to concrete). Sulfuric acid solution in the presence of chloride ions was used as corrosion media. The composition of corrosion acid media used was 1 mol L-1 H 2 SO 4 and 10-3 mol L-1 Cl-(in the form of NaCl). Electrochemical techniques such as potentiodynamic polarization methods were used for inhibitor efficiency testing.
Proceedings of the 8th World Congress on Mechanical, Chemical, and Material Engineering
The development of green corrosion inhibitors are highly demanded because of the increasing deman... more The development of green corrosion inhibitors are highly demanded because of the increasing demand of green chemistry in the area of science and technology. Use of plant extracts as corrosion inhibitors has attracted significantly attention. The present study investigates corrosion inhibition of pineapple crown extract for steel 39 in 1M H₂SO 4 and 1M HCl. The weight loss method is used for inhibitor efficiency testing. The inhibition efficiency of inhibitor increases with the increases of concentration of inhibitor. Use of this inhibitor in concentration 3g/L present protection efficiency 82.88 % for steel 39 in aggressive media. The results present that pineapple crown extract is a good choice for steel 39 and environment, too.
Ovidius University Annals of Chemistry
The efficiency of pineapple crown extract as corrosion inhibitor of aluminum in 1M H2SO4 acidic m... more The efficiency of pineapple crown extract as corrosion inhibitor of aluminum in 1M H2SO4 acidic medium was tested using weight loss and potentiodynamic methods, at varied inhibitor concentration. Through the data from the weight loss method there was calculated the corrosion rate and pineapple crown extract’s inhibition on aluminum corrosion in acidic medium, at varied inhibitor concentration. Also, with the data obtained from the potentiodynamic method, the polarization curves and Tafel tangents were constructed, while calculating the corrosion rate and inhibition efficiency of pineapple crown extract. Experimental measurements showed that pineapple crown extract acts as a mixed inhibitor and the inhibition efficiency increases with increasing the extract concentration.
World Congress on Mechanical, Chemical, and Material Engineering, 2021
Corrosion is an inevitable natural phenomenon. The amino acids are green corrosion inhibitors due... more Corrosion is an inevitable natural phenomenon. The amino acids are green corrosion inhibitors due to their nontoxicity and biodegradability. For this reason they are a good choice for corrosion protection. As inhibitors, we have used two amino acids, lysine and methionine. They have shown good inhibitor properties in protection of low allow carbon steel against the corrosion in acidic media. The aim of this study is to compare corrosion protection efficiency of these amino acids. Material under investigation is low alloy carbon steel marked as: Steel 39, Steel 44 and the corrosion media is: 1M H2SO4 + 10-3 mol/L Cl-(in form of NaCl). A Tafel polarization technique was used for investigation of corrosion inhibitor efficiency. The results present that methionine is more protective again acidic corrosion and the steel 44 is more sustainable again sulfuric acidic corrosion. The best case in the respect of corrosion sustainability for steel 44 is in presence of 1g/L methionine with protection efficiency respectively 81.27%.
Proceedings of the 6th World Congress on Mechanical, Chemical, and Material Engineering
Corrosion undermines the physical integrity of structures and can lead to destruction of property... more Corrosion undermines the physical integrity of structures and can lead to destruction of property and loss of life. Chlorideinduced steel corrosion is one of the major worldwide deterioration problems for steel reinforced concrete structures. The use of green inhibitors in producing high performance concrete has increased significantly. The aim of our study was to investigate the efficiency of green inhibitor and migration inhibitor admixed in concrete. The concrete samples were exposed in aggressive media H2SO4 1M and 10-3 Cl-. As corrosion inhibitor we have used locust bean gum as a green inhibitor and methionine+butanolamine as migration inhibitor. Half-cell potential, polarization resistance and Tafel extrapolation methods are used for inhibitor efficiency testing. The results shows high resistance polarization and low corrosion rate for concrete sample with inhibitor. The corrosion rate decrease approximately 90% in presence of locust bean gum and 80% in presence of migration inhibitor
Proceedings of the 6th World Congress on Mechanical, Chemical, and Material Engineering
Corrosion undermines the physical integrity of structures and can lead to destruction of property... more Corrosion undermines the physical integrity of structures and can lead to destruction of property and loss of life. Chlorideinduced steel corrosion is one of the major worldwide deterioration problems for steel reinforced concrete structures. The use of green inhibitors in producing high performance concrete has increased significantly. The aim of our study was to investigate the efficiency of green inhibitor and migration inhibitor admixed in concrete. The concrete samples were exposed in aggressive media H2SO4 1M and 10-3 Cl-. As corrosion inhibitor we have used locust bean gum as a green inhibitor and methionine+butanolamine as migration inhibitor. Half-cell potential, polarization resistance and Tafel extrapolation methods are used for inhibitor efficiency testing. The results shows high resistance polarization and low corrosion rate for concrete sample with inhibitor. The corrosion rate decrease approximately 90% in presence of locust bean gum and 80% in presence of migration inhibitor
Në kuadër të këtij punimi janë studiuar nanostrukturat e një shtrese filmike të përgatitur në mën... more Në kuadër të këtij punimi janë studiuar nanostrukturat e një shtrese filmike të përgatitur në mënyrë eksperimentale. Janë përcaktuar vetitë strukturale dhe elektronike edhe të nanostrukturave të një gjysmëpërçuesi. Tensioni mekanik i nanostrukturave dhe kompozicioni i tyre janë përcaktuar me anë të difraksionit të rrezeve të rëntgenit. Janë matur spektrat difraksionalë të rrezeve të rëntgenit (XRD) për CdTe të elektrodepozituara mbi çelik inoks, mbi nikel dhe për CdTe në formë pluhuri. Me anë të elektroskopit elektronik me rreze depërtuese është bërë përcaktimi i kompozicionit ndërtues. Është përcaktuar koeficienti i absorbimit optik i shtresës së hollë prej CdTe, me trashësi prej 0.95 μm, në funksion të energjisë fotonike. Është përcaktuar kalimi kuantik i drejtpërdrejtë për shtresën e hollë prej CdTe duke fituar vlerën 1. 51 eV. Fjalët çelës: nanostrukturat, gjysmëpërçuesi, absorbimi kuantik, shtresa e hollë.. SUMMARY Nanostructures on the experimentally prepared thin film layer are studied. Structural and electronic properties of these semiconductor nanostructures are accessed. Strain and composition are evaluated by using high-resolution xray diffraction technique. The X Ray Diffraction (XRD) spectra for CdTe electrodeposited on stainless steel, on nickel and for CdTe powder are measured. Transition electron microscopy techniques for composition evaluation are applied. The optical absorption coefficient as a function of photon energy for a 0.95 μm thin CdTe film originally deposited on stainless steel is evaluated. Direct allowed transition in a 0.23 μm thin CdTe film deposited initially on molybdenum at −580 m is determined and the value of 1.51 eV is obtained.
Ovidius University Annals of Chemistry
Concrete is more widely used than any other manmade material. The objective of this paper is to i... more Concrete is more widely used than any other manmade material. The objective of this paper is to investigate the behavior of reinforced cement when migration corrosion and guar gum inhibitors are used. The concrete samples were exposed in aggressive media H2SO4 1 M and in the presence of 1∙10-3 M Cl-. Electrochemical measurements such as half-cell potential, polarization resistance and Tafel extrapolation methods were performed in order to obtain information on the corrosion behavior of the reinforcing steel in cement mortar. Results demonstrate high resistance polarization and low corrosion rate for concrete sample with inhibitor. The corrosion rate decreases approximately 95% in presence of locust bean gum and 80% in presence of migration inhibitor.
Journal of Institute Alb Shkenca, 2011
Në kuadër të këtij punimi janë studiuar nanostrukturat e një shtrese filmike të përgatitur në mën... more Në kuadër të këtij punimi janë studiuar nanostrukturat e një shtrese filmike të përgatitur në mënyrë eksperimentale. Janë përcaktuar vetitë strukturale dhe elektronike edhe të nanostrukturave të një gjysmëpërçuesi. Tensioni mekanik i nanostrukturave dhe kompozicioni i tyre janë përcaktuar me anë të difraksionit të rrezeve të rëntgenit. Janë matur spektrat difraksionalë të rrezeve të rëntgenit (XRD) për CdTe të elektrodepozituara mbi çelik inoks, mbi nikel dhe për CdTe në formë pluhuri. Me anë të elektroskopit elektronik me rreze depërtuese është bërë përcaktimi i kompozicionit ndërtues. Është përcaktuar koeficienti i absorbimit optik i shtresës së hollë prej CdTe, me trashësi prej 0.95 μm, në funksion të energjisë fotonike. Është përcaktuar kalimi kuantik i drejtpërdrejtë për shtresën e hollë prej CdTe duke fituar vlerën 1. 51 eV. Fjalët çelës: nanostrukturat, gjysmëpërçuesi, absorbimi kuantik, shtresa e hollë.. SUMMARY Nanostructures on the experimentally prepared thin film layer are studied. Structural and electronic properties of these semiconductor nanostructures are accessed. Strain and composition are evaluated by using high-resolution xray diffraction technique. The X Ray Diffraction (XRD) spectra for CdTe electrodeposited on stainless steel, on nickel and for CdTe powder are measured. Transition electron microscopy techniques for composition evaluation are applied. The optical absorption coefficient as a function of photon energy for a 0.95 μm thin CdTe film originally deposited on stainless steel is evaluated. Direct allowed transition in a 0.23 μm thin CdTe film deposited initially on molybdenum at −580 m is determined and the value of 1.51 eV is obtained.
Fresenius Environmental Bulletin, 2011
Coumarins, quinolinones, tetramic and tetronic acid
analogues, play an integral role in biologi... more Coumarins, quinolinones, tetramic and tetronic acid
analogues, play an integral role in biological systems and
forms a variety of complexes with environmentally active
metals. A survey of their synthesis as ligands and their
ability to form coordination compounds is presented.
KEYWORDS: N-,O-ligands, biological activity, complexation,
environmental ions.
Analele Universitatii "Ovidius" Constanta - Seria Chimie, 2014
The use of inhibitors is one of the most practical means for protecting metals against corrosion,... more The use of inhibitors is one of the most practical means for protecting metals against corrosion, especially in acidic media. The interest is to use organic compounds as inhibitors due mainly to their inherent and non-toxic nature. Amino acids are attractive as corrosion inhibitors because they are nontoxic, relatively easy to produce with high purity at low cost, and are soluble in aqueous media. Lysine, one kind of amino acid is used as inhibitor. The aims of this study are to show corrosion protection efficiency of lysine and to explain the mechanism of corrosion. The experimental results demonstrated that the lysine offered protection for low alloy carbon steel in aggressive environments like H2SO4. Materials under investigation are two types of low alloy carbon steel marked as: Steel 39, Steel 44 (usually applied to concrete as reinforcing bars). The corrosion media consists in sulfuric acid in presence of chloride ions, in form of NaCl (H2SO4 1M + Cl- 10-3M). Potentiodynamic p...
Analele Universitatii "Ovidius" Constanta - Seria Chimie, 2014
The corrosion of metal surfaces causes huge financial damages to the industries annually, what ha... more The corrosion of metal surfaces causes huge financial damages to the industries annually, what has lead to an increase in the search for substances that can slow down or prevent corrosion rate. Green inhibitors which are biodegradable, without any heavy metals and other toxic compounds, are promoted. Amino acids are attractive as corrosion inhibitors because they are nontoxic. We have used methionine as corrosion inhibitor. Materials under investigation are two kind of low allow carbon steel marked as: Steel 39, Steel 44 usually applied to concrete as reinforcing bars, and manufacture in Elbasan. The inhibition effect of methionine on the corrosion behavior of low allow steel is investigated in sulfuric acid in presence of chloride ions, in form of NaCl (H2SO4 1M + Cl- 10-3M). Potentiodynamic polarization method is used for inhibitor efficiency testing. The pitting corrosion current shows that increasing concentration of the inhibitor causes a decrease in pitting current density, an...
Asian Journal of Chemistry, 2013
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Papers by Efrosini Kokalari
analogues, play an integral role in biological systems and
forms a variety of complexes with environmentally active
metals. A survey of their synthesis as ligands and their
ability to form coordination compounds is presented.
KEYWORDS: N-,O-ligands, biological activity, complexation,
environmental ions.
analogues, play an integral role in biological systems and
forms a variety of complexes with environmentally active
metals. A survey of their synthesis as ligands and their
ability to form coordination compounds is presented.
KEYWORDS: N-,O-ligands, biological activity, complexation,
environmental ions.