Decomposition of poly(N-isopropylmethacrylamide) homopolymer network

Poly(N-isopropylmethacrylamide) homopolymer, which belongs to thermosensitive hydrogels, was synthesized by free radical polymerization method with 1.5 mol% of ethylene glycol dimethacrylate as cross-linker. The structure of obtained homopolymer network was confirmed by Fourier transform infrared spectroscopy analysis. The hydrogel in the gelatinous state was subjected to gamma irradiation in order to additionally form a three-dimensional network in a solid state. Suddenly, the synthesized gelatinous homopolymer was transformed into the liquid state after irradiation instead of expected additional crosslinking. Breakdown of poly(Nisopropylmethacrylamide) homopolymer was confirmed by using different methods: gel permeation chromatography, the static headspace gas chromatography mass spectrometry and gas chromatography/flame ionization detection methods. New compounds, different from the homopolymer, monomer and crosslinker were detected after irradiation. As result, the gamma irradiation will be applicable for the poly(N-isopropylmethacrylamide) homopolymer decomposition and useful to further recyclability analysis

Bacterially generated H2SO4 from pyrite, as a leaching agent for phosphorus from phosphate ore

The object of this study was to investigate the possibility of phosphorus leaching from mixture of phosphate ore and pyrite minerals, in laboratory conditions using sulfuric acid generated by bacterial culture of Acidithiobacillus ferrooxidans (At. ferrooxidans), because the possible application of these mixtures as a natural phosphate fertilizers. Results obtained show that phosphorus has been leached from the test mixture up to 34,5 % in suspension with At. ferrooxidans, and in the same time, degree of leaching in control suspension (without At. ferrooxidans) was up to 3,8

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

Bacterially generated H2SO4 from pyrite, as a leaching agent for phosphorus from phosphate ore

The object of this study was to investigate the possibility of phosphorus leaching from mixture of phosphate ore and pyrite minerals, in laboratory conditions using sulfuric acid generated by bacterial culture of Acidithiobacillus ferrooxidans (At. ferrooxidans), because the possible application of these mixtures as a natural phosphate fertilizers. Results obtained show that phosphorus has been leached from the test mixture up to 34,5 % in suspension with At. ferrooxidans, and in the same time, degree of leaching in control suspension (without At. ferrooxidans) was up to 3,8

The Origin of 99Tc in the Environment and Its Removal

Technetium-99 (99Tc), as one of the important high-yield fission products, is a significant threat to the environment and human health. It is produced in large amounts by nuclear fission of 235U or 239Pu in nuclear reactions, though the quantity of Tc produced by the spontaneous fission of 238U or by decay of 99Mo in the nature which is very small. 99Tc in the environment originates from nuclear weapons tests, discharges from nuclear power plants, nuclear medicine and radiobiology. These activities generate large volumes of low and intermediate radioactive waste which can cause a significant impact on the environment if disposed without suitable treatment. Immobilization of 99Tc into a relatively small volume waste is vital for long term permanent disposal. High mobility and long half-life of 99Tc considered to be one of the most important radionuclides in safety assessment of environmental radioactivity as well as nuclear waste management. Effective removal of radioactive technetium (99Tc) from contaminated water is of enormous importance from an environmental and public health perspective, yet many current methodologies are highly ineffective. This paper summarizes physico-chemical separation procedures emphasizing those that are the most used in practice. Classic sorbents such as activated carbons, ion exchange resins as well, as new materials, such as metal−organic frameworks and graphene based membranes are described in the paper

Intelligent Poly(N-Isopropylmethacrylamide) Hydrogels: Synthesis, Structure Characterization, Stimuli-Responsive Swelling Properties, and Their Radiation Decomposition

Poly(N-isopropylmethacrylamide) (p(NiPMAm)) is one of the lesser known homopolymers that has significant potential for designing new “intelligent” materials. The aims of this work were the synthesis a series of cross-linked p(NiPMAm) hydrogels by the free radical polymerization method and the application of gamma-ray radiation for additional cross-linking. The synthesized p(NiPMAm) hydrogels were structurally characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The amount of unreacted monomers was analyzed using high pressure liquid chromatography (HPLC) to evaluate conversion of monomers into polymers. The swelling behavior was monitored in dependence of pH and temperature changes. The previous aim of gamma-ray radiation was the further the cross-linkage of the obtained hydrogel sample in the gelatinous, paste-like state, but the gamma-ray radiation caused decomposition. After absorbing irradiation doses, they transformed into the liquid phase. The results obtained by the gel permeation chromatography (GPC) method indicated that only oligomers and monomers were present in the irradiated liquid material, without molecules with a higher average molar mass, i.e., that the decomposition of the hydrogels occurred. Additionally, the irradiated liquid material was analyzed using the static headspace gas chromatography mass spectrometry (HSS-GC/MS) and gas chromatography/flame ionization detection (HSS-GC/FID) methods. The presence of unchanged initiator molecule and a dominant amount of four new molecules that were different from homopolymers and the reactant (monomer and cross-linker) were determined

Procedure for extraction of ellagic acid from lady`s mantles (Alchemilla vulgaris L.) RS-P-2017/0289.

Pronalazak se odnosi na nov postupak ekstrakcije elaginske kiseline iz herbe biljne vrste gospin plašt (Alchemilla vulgaris L.). Postupak ekstrakcije pokazuje neočekivanu selektivnost za elaginsku kiselinu, dok je sadržaj drugih jedinjenja ispod granica detekcije. Ispitivanja ekstrakta A. vulgaris pokazuju zadovoljavajuću antioksidativnu aktivnost, a određen je i sadržaj ukupnih flavonoida. Dobijeni ekstrakt herbe A. vulgaris može biti primenjen kao prirodni aditiv u prehrambenoj, kozmetičkoj i farmaceutskoj industriji, jer ima jak antioksidativni i zaštitni efekat.Решење о признању патента 990 број 2019/8183-П-2017/0289 од 14.05.2019. објава патента: Гласник интелектуалне својине 5/2019, Завод за интелектуалну својину, Република Србија. (RS 58657 B1

Postupak primene termoosetljivih hidrogelova za modifikovano oslobađanje elaginske kiseline

Pronalazak se odnosi na novu primenu hidrogelova poli(N-izopropilakrilamid-ko-2-hidroksipropilmetakrilata), p(NIPAM-HPMet)-a i poli(N-izopropilakrilamida), p(NIPAM)-a, kao nosača za modifikovano oslobađanje elaginske kiseline i ekstrakta Alchemilla vulgaris L. sa visokim sadržajem elaginske kiseline. Analiza FTIR spektara homopolimera p(NIPAM)-a i kopolimera p(NIPAM-HPMet)-a sa uklopljenim standardom elaginske kiseline i ekstraktom Alchemilla vulgaris L., ukazuju na formiranje intermolekulskih vodoničnih veza između lanaca homopolimera, tj. kopolimera, s jedne strane i elaginske kiseline, s druge strane. Hidrogelovi p(NIPAM) i p(NIPAM-HPMet) su se pokazali kao pogodni nosači elaginske kiseline, jer omogućavaju njeno modifikovano oslobađanje

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

The removal of heavy metal ions from aqueous solutions by hydrogels based on N-isopropylacrylamide and acrylic acid

The temperature- and pH-sensitive poly(N-isopropylacrylamide-co-acrylic acid) hydrogels, poly(NIPAM-co-AA), were synthesized by radical polymerization. The characterizations of hydrogels based on N-isopropylacrylamide (NIPAM) and acrylic acid (AA) before and after adsorption of heavy metal ions was performed by Fourier transform infrared spectroscopy and scanning electron microscopy. Heavy metal ions (Cr, Mn, Pb) adsorbed onto poly(NIPAM-co-AA) hydrogels were identified using the energy-dispersive X-ray spectroscopy. The mechanism of the water transport within the matrix of synthesized poly(NIPAM-co-AA) hydrogels at pH 4.5 is Super Case II diffusion, and at pH 6.8 corresponds to the non-Fickian diffusion mechanism. The effect of pH, temperature, contact time, and the initial concentration of heavy metals on the adsorption process of Cr(VI), Mn(II), and Pb(II) ions from aqueous solutions onto poly(NIPAM-co-AA) hydrogels were investigated. The kinetic and equilibrium data were best fitted by the pseudo-second-order model and Langmuir adsorption isotherm. Thermodynamic results indicate that the removal process of heavy metal ions from aqueous solutions by poly(NIPAM-co-AA) hydrogels was spontaneous and exothermic in nature. Maximum adsorption capacities of poly(NIPAM-co-AA) hydrogels for heavy metal ions decrease in the following order: Pb(II) > Cr(VI) > Mn(II).This is a post-peer-review, pre-copyedit version of an article published in Polymer Bulletin. The final authenticated version is available online at: [http://dx.doi.org/10.1007/s00289-018-2295-0