Brzina korozije cevi od nerđajućih čelika izračunata pomoću elektrohemijske frekvencione modulacije

The use of high energy, ionizing radiation in nuclear medicine is now pervasive and routine. The interaction of gamma radiation with aqueous solutions produces different kinds of reducing and oxidizing agents. Reducing agents represent eaq, H• and H2 while oxidizing agents represent H2O2, •OH, O2, O2 - and HO2 [1]. Production of such species under gamma irradiation, there may affect the rates or mechanisms of corrosion attack modes. In recent times, electrochemical frequency modulation (EFM) has caught the attention of corrosion scientists as a rapid and non–destructive technique for the instantaneous determination of corrosion rate. The advantage of the EFM technique is the fact that the measurement can be completed in a short time period [2]. The EFM technique offers an excellent alternative for the analysis of electrochemical corrosion behavior of metals compared with contemporary techniques like potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy and weight loss. This technique provides measurements of corrosion rate directly without knowledge of the Tafel constants. Even though the Tafel constants are not required, it measures them and a change in Tafel constant may indicate a change in corrosion mechanism. The theory behind the technique is the same Butler-Volmer kinetics that underpins all corrosion rate measurements. It is a small signal ac technique where two sine waves (at different frequencies) are applied to the cell simultaneously. In our work, we used the EFM technique to calculate the corrosion rate on stainless steel samples in saline and under gamma radiation.Nerđajući čelici su omiljeni materijali u nuklearnoj medicini zbog jednostavnog održavanja (brisanje, dekontaminacija, itd.). Otpornost na rđanje ovih materijala je smanjena usled istovremenog delovanja hloridnih jona i jonizujućeg zračenja. Brza i nedestruktivna tehnika merenja korozije, kao što je elektrohemijska frekvenciona modulacija (EFM), korisna je za brzu procenu materijala koji moraju biti otporni na rđаnje. Tri različite cevi od nerđajućeg čelika su analizirane pomoću EFM metode i Gamry potenciostata / galvanostata, i izračunate su njihove brzine korozije. Uzorak označen kao S II, koji ne sadrži Mo u svom sastavu pokazuje veću brzinu korozije u odnosu na uzorke koji sadrže Mo ako je istovremeno izložen hloridnim jonima i gama zračenju. Ovaj rezultat je u sagalsnosti sa sastavom nerdjajučćeg čelika dobijenim rentgenskim fluorescentnim spektrometrom koji pokazuje nedostatak bakra i vanadijuma u tragovima, uključujući molibden.57th Meeting of the Serbian Chemical Society; June 18-19, Kragujevac, Serbi

Swelling behavior of synthesized poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) hydrogels

Poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) has great application in cosmetics, primarily in personal care products. It is used in drug delivery, and in a variety of biomedical applications. Also, significant is the application as an adsorbent of various pesticides. The aim of this paper is to examine structural characterization and the swelling behavior of synthesized poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) copolymer hydrogels with 10 mol% of vinyl acetate and with 1.0; 1.5; 2.0; 2.5 and 3.0 mol% of cross-linker ethylene glycol dimethacrylate (EGDM). The characterization of the synthesized hydrogels was performed using FTIR spectroscopy. The swelling study was monitored gravimetrically until equilibrium was reached in solutions of different pH values (3.0, 6.0, 9.0) at a temperature of 25°C. The sensitivity of poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) hydrogels to changes in external temperature was examined by monitoring the change in the equilibrium degree of swelling with increasing fluid temperature from 25ºC to 80ºC in a pH solution of 6.0. FTIR spectra of xerogels confirm the performed synthesis. Swelling of hydrogels poly(1-vinyl-2-pyrrolidone-co-vinyl acetate) was favored at a lower temperature (25°C), in a solution whose pH=6.0, when the sample with 1.0 mol% EGDM reaches the highest degree of swelling (αe=87.23) compared to the achieved capacity at a temperature of 80ºC (αe=20.74). The most intense phase transition was observed in the temperature range of 40-45°C. Based on the obtained results, the synthesized copolymers can be classified into negative thermosensitive hydrogels that have a lower critical dissolution temperature (LCST). pH sensitivity analysis led to the conclusion that the highest value of the equilibrium degree of swelling (αe=168.97) was observed in the hydrogel sample with 1.5 mol% EGDM in the solution whose pH=9 at 25°C. An increase in the molar content of cross-linkers in the hydrogels composition shows a decrease in swelling capacity at all pH values and temperaturesVIII International Conference on Radiation in Various Fields of Research : RAD 2020 : book of abstracts; Virtual Conferenc

PREČIŠĆAVANJE KONTAMINIRANIH OTPADNIH VODA UZ POMOĆ GRAFENSKIH KOMPOZITA SA HIDROGELOVIMA

Lack of clean water requires the use of new wastewater treatment technologies. Adsorption is a simple and effective method for removing contaminants from contaminated water. Graphene composites with hydrogels have found application in wastewater treatment because they have unique properties such as porous structure, unique morphology, good rheological properties, non-toxicity, etc. The paper presents a literature overview of potential solutions to wastewater treatment using composite graphene and graphene oxide with hydrogel-like adsorbents. The mentioned composite compounds have been used in the treatment or elimination of various hazardous substances. In this work, we have investigated the possible adsorption of different classes of colored pollutants (paints) and pesticides (both organic and inorganic).Nedostatak čiste vode zahteva korišćenje novih tehnologija za prečišćavanje otpadnih voda. Adsorpcija je jednostavan i efikasan metod za uklanjanje zagađivača iz kontaminirane vode. Kompoziti grafena sa hidrogelovima našli su primenu u prečišćavanju otpadnih voda jer imaju jedinstvena svojstva kao što su porozna struktura, jedinstvena morfologija, dobra reološka svojstva, netoksičnost itd. Rad predstavlja pregled literature potencijalnih rešenja za tretman otpadnih voda korišćenjem kompozitnog materijala, grafena i grafen oksida sa hidrogelom. U ovom radu su pomenuta kompozitna jedinjenja korišćena u tretmanu različitih opasnih materija odnosno adsorpciji različitih klasa obojenih zagađivača (boja) i pesticida (organskih i neorganskih)

KVALITET ZEMLJIŠTA DIVLJE DEPONIJE NA TERITORIJI GRDELICE

Soil protection is carried out by monitoring soil quality, while preventing it from emissions of harmful and hazardous substances. Soil analysis at closed landfills includes soil quality testing, as well as detection of potentially harmful substances. This paper presents the results of the analysis of soil samples at a wild landfill on the territory of the town of Grdelica.  The purpose of this paper is to determine soil quality, detect possible contamination, and identify potentially harmful and hazardous substances in samples using key aspects of Serbia's regulatory policy.Zaštita zemljišta se sprovodi praćenjem kvaliteta zemljišta, ali i sprečavanjem emisije štetnih i opasnih materija. Analiza zemljišta na zatvorenim deponijama uključuje ispitivanje kvaliteta zemljišta, kao i otkrivanje potencijalno štetnih supstanci. U radu su prikazani rezultati analize uzoraka zemljišta na divljoj deponiji na teritoriji Grdelice. Ovaj rad ima za cilj da utvrdi kvalitet zemljišta, detekciju moguće kontaminacije i identifikaciju potencijalno štetnih i opasnih materija u uzorcima sa osvrtom na ključne aspekte regulatorne politike Republike Srbije

THE EVALUATION OF CROSS-LINKER CONTENT IMPACT ON THE SWELLING CAPACITY OF POLY(1-VINYL-2-PYRROLIDONE) HYDROGELS

Poly(1-vinyl-2-pyrrolidone), p(VP), is a polar, hydrophilic, amphoteric polymer, derived from a monomer of 1-vinyl-2-pyrrolidone. It is used in many branches of industry (in the production of glues, paper and detergent). Due to its solubility in water and low cytotoxicity is one of the most used polymers in medicine. The aim of this study was to examine swelling behavior of synthesized poly(1-vinyl-2-pyrrolidone) hydrogels. By free radical polymerization of 1-vinyl-2-pyrrolidone, samples of poly(1-vinyl-2-pyrrolidone) hydrogels with 1.0, 2.0 and 3.0 mol% of ethylene glycol dimethacrylate (EGDM) as cross-linker were synthesized. The polymerization reaction was initiated by the addition of 2,2\u27-azobis(2-methylpropionitrile) (AZDN) initiator, and the reactants were dissolved in an adequate amount of methanol. Data obtained by scanning electron microscopy (SEM) were used to determine the structure and pore size of the freeze-dried hydrogels, swelled to equilibrium state. Synthesized p(VP) hydrogels were used to test swelling behavior and their sensitivity to changes in pH values (3.0, 6.0 and 9.0) and temperature (25-80°C). The swelling process was monitored gravimetrically. Swelling of hydrogels p(VP) is most intense at room temperature (25°C). The most intensely swelling is in a alkaline fluid, pH=9.0 (αe=141.98 for the sample with 1 mol% EGDM). In a fluid of pH 6.0 they achieved equilibrium degree of swelling αe=67.46. At 25°C the smallest degree of swelling of p(VP) is in the strong acidic fluid, pH=3.0 (αe=34.13). The thermo-sensitivity testing showed that degree of swelling decreases along with temperature increasing. The phase transition is in the temperature interval from 40°C to 45°C. The lowest degree of swelling of p(VP) was achieved in the highest tested temperature at 80°C (α=12.13). Porous structure of p(VP) hydrogels were confirmed by SEM micrographs. It can be concluded that with a decrease in the amount of cross-linker increases the pore size and degree of swelling of synthesized cross-linked p(VP) hydrogels

Investigation of silver impact on hydroxyapatite/lignin coatings electrodeposited on titanium

Silver doped hydroxyapatite (HAP) [Ca9.95Ag0.05(PO4)(6)(OH)(2)] composite coatings with natural polymer organosolv lignin (Lig) were produced by electrophoretic deposition (EPD) on titanium. Coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The corrosion stability of electrodeposited coatings was evaluated in vitro in Kokubo's simulated body fluid (SBF) at 37 degrees C using electrochemical impedance spectroscopy (EIS). Antimicrobial properties are directly proportional to the rate of silver ions release from the coatings, determined from inductively coupled plasma spectrometry (ICP-AES). The obtained results are in good agreement with viability of pathogenic bacteria strain Staphylococcus aureus TL in suspension, which had completely disappeared after 24 h. Composite Ag/HAP/Lig coatings were confirmed as non-toxic for healthy immunocompetent peripheral blood mononuclear cells (PBMC)

Material flow management of construction waste: case study Jablanica district, Serbia

The paper analyses the current situation and perspectives of construction waste management in the territory of Jablanica district, Serbia. Considering the importance of construction waste management for the ecosystem, the state and perspectives are assessed through the assessment of the possibilities of reuse and recycling. According to Rulebook on waste categories with catalogue in Serbia, construction waste found at the landfill Donja Jajina is classified and observed in this research. Based on a six-month daily monitoring of the material flow of construction waste at the landfill in Dona Jajina, the current estimated state of the amount of waste as well as further growth of waste at the landfill is presented. Using MATLAB simulation code, predictions for the next 15 years are obtained, and conclusions are made. At the moment, concrete, brick, asphalt, as well as other construction waste are being buried at the landfill in Donja Jajina, and no further waste treatment is being done. The landfill has a lot of material that could be further used and put into use. It is necessary to build a stationary recycling plant on the landfill itself that would produce recycled aggregates and thereby reduce the use of natural aggregates

Bioactive hydroxyapatite/graphene composite coating and its corrosion stability in simulated body fluid

The hydroxyapatite/graphene (HAP/Gr) composite was electrodeposited on Ti using the electrophoretic deposition process to obtain uniform bioactive coating with improved mechanical strength and favorable corrosion stability in simulated body fluid (SBF). Incorporation of Gr was verified by Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron analysis. The HAP/Gr composite coating exhibited reduced surface cracks, nearly double the hardness, and elastic modulus increased by almost 50% compared to pure HAP coating, as estimated by a nanoindentation test. The bioactive HAP/Gr composite coating provided a newly formed apatite layer in SBF with enhanced corrosion stability, as evidenced by electrochemical impedance spectroscopy. The thermal stability of the HAP/Gr coating was improved in comparison to the pure HAP coating, and the Ca/P ratio was closer to the stoichiometric value. No antibacterial activity against Staphylococcus aureus or Escherichia coli could be verified. The HAP/Gr composite coating was classified as non-cytotoxic when tested against healthy peripheral blood mononuclear cells (PBMC)