Leaching resistance of alkali-activated binder contaminated with cesium

Leaching is a phenomenon of fundamental interest in low-level radioactive waste disposal, and the measurement of the leaching resistance of different wasteforms is very important for proper waste management. In general, alkali-activated binders (AABs) can be considered as a sustainable solution for safe immobilization of hazardous wastes containing different toxic or radioactive elements. In this paper, the leaching resistance of AAB based on blast furnace slag (BFS), contaminated with 2% cesium (i.e., solidified simulated low-level radioactive waste), was investigated according to the ANSI/ANS-16.1-2003 standard procedure. Based on the leaching results obtained for different elements, in particular for Cs, Si, Al, Ca, Na, and K, it was concluded that the short (up to 5 days) semi-dynamic process of leaching from AAB can be divided into two distinct stages: a) fast leaching of non-bound or loosely bound ions during the initial 24 hours, which occurred mostly between the surface of AAB and the leachant, and b) slower leaching in the later stages of the experiment, which was controlled by diffusion of ions through AAB matrix. By calculating the diffusion coefficient (D) and the leachability index (L) of cesium, it was also concluded that AAB based on blast furnace slag, synthesized under the given experimental conditions, can be considered as a potentially efficient matrix for immobilizing up to 2% cesium in hazardous wastes

Hidrogeohemijska istraživanja u jugoistočnom Banatu na teritoriji Republike Srbije

In the research phase of the geological status of the area of southeastern Banat, samples were collected from surface waters, wells, and lakes. The content of U, Ra, Rn is determined in water. The sampling network was adjusted to the hydrographic characteristics of the terrain, and a hydrogeochemical map has been made at a scale of 1:50 000. In addition to hydrogeochemical prospecting, samples of the soil river sediments were taken to determine the profile of the coast of the following lakes: Vračarevo, Šaransko, Bagersko and Veliko lake. The regional hydrogeochemical prospecting included the area of the Bela Crkva, which drained the sediments of Negotin and Kvartara. In this area and wider, in accordance with the results of regional investigation, semi-geological and semi-geochemical research was carried out to identify resources of mineral deposits as well as the sources for water supply of rural settlements. During research, samples of water from surface streams, sources, wells, lakes, water reservoirs, creek sediments and wall samples were collected and examined.U fazi istraživanja geološkog statusa područja jugoistočnog Banata, prikupljeni su uzorci sa površinskih akvatorija, bunara i jezera. U vodi je determinisan sadržaj U, Ra, Rn. Mreža uzorkovanja je prilagođena hidrografskim karakteristikama terena, i napravljena je hidrogeohemijska mapa 1:50 000. Pored hidrogeohemijske prospekcije, uzeti su uzorci rečnih sedimenata zemljišta kako bi se odredio profil obale sledećih jezera: Vračarevo, Šaransko, Bagersko i Veliko jezero. Regionalna hidrogeohemijska prospekcija obuhvatila je područje Bele Crkve, koje dreniraju sedimente Neogena i Kvartara. U ovom području i šire, u skladu sa rezultatima regionalnih ispitivanja, obavljena su i poludetaljna geološka-geohemijska istraživanja u cilju identifikacije ležišta mineralnih sirovina, kao i izvorišta za vodosnabdevanje ruralnih naselja. U toku prospekcije, prikupljeni i ispitani su uzorci voda iz površinskih tokova, izvora, bunara, jezera, vodenih akumulacija, potočnih sedimenata i uzorci stena

Hidrogeohemijska istraživanja u jugoistočnom Banatu na teritoriji Republike Srbije

In the research phase of the geological status of the area of southeastern Banat, samples were collected from surface waters, wells, and lakes. The content of U, Ra, Rn is determined in water. The sampling network was adjusted to the hydrographic characteristics of the terrain, and a hydrogeochemical map has been made at a scale of 1:50 000. In addition to hydrogeochemical prospecting, samples of the soil river sediments were taken to determine the profile of the coast of the following lakes: Vračarevo, Šaransko, Bagersko and Veliko lake. The regional hydrogeochemical prospecting included the area of the Bela Crkva, which drained the sediments of Negotin and Kvartara. In this area and wider, in accordance with the results of regional investigation, semi-geological and semi-geochemical research was carried out to identify resources of mineral deposits as well as the sources for water supply of rural settlements. During research, samples of water from surface streams, sources, wells, lakes, water reservoirs, creek sediments and wall samples were collected and examined.U fazi istraživanja geološkog statusa područja jugoistočnog Banata, prikupljeni su uzorci sa površinskih akvatorija, bunara i jezera. U vodi je determinisan sadržaj U, Ra, Rn. Mreža uzorkovanja je prilagođena hidrografskim karakteristikama terena, i napravljena je hidrogeohemijska mapa 1:50 000. Pored hidrogeohemijske prospekcije, uzeti su uzorci rečnih sedimenata zemljišta kako bi se odredio profil obale sledećih jezera: Vračarevo, Šaransko, Bagersko i Veliko jezero. Regionalna hidrogeohemijska prospekcija obuhvatila je područje Bele Crkve, koje dreniraju sedimente Neogena i Kvartara. U ovom području i šire, u skladu sa rezultatima regionalnih ispitivanja, obavljena su i poludetaljna geološka-geohemijska istraživanja u cilju identifikacije ležišta mineralnih sirovina, kao i izvorišta za vodosnabdevanje ruralnih naselja. U toku prospekcije, prikupljeni i ispitani su uzorci voda iz površinskih tokova, izvora, bunara, jezera, vodenih akumulacija, potočnih sedimenata i uzorci stena

Radon exhalation from fly-ash geopolymer mortar

Geopolymers are a type of alkali activated binders, inorganic aluminosilicate polymers with amorphous cross-linked structure. Fly-ash is produced in abundance during coal firing, and poses an environmental and health risk in untreated powder form. Fly-ash geopolymer presents a sustainable alternative to Portland cement, due to lower net greenhouse gas emissions. Presence of naturally occurring radioactive elements in fly-ash is one of the factors taken into account when estimating the safety of fly-ash based building materials. Radon, a radioactive noble gas originating from the decay of radium, can leave the material and contribute to internal dose in closed spaces, so radon exhalation is of special interest. Radon exhalation for a standard sample of fly-ash geopolymer mortar was measured

Effect of accelerated carbonation on the efficiency of immobilization of Cs in the alkaliactivated blast furnace slag

In this paper the effect of accelerated carbonation process on the effectiveness of immobilization of cesium (simulated radioactive and toxic waste) in the alkali-activated blast furnace slag (AABFS) matrix was studied. Blast furnace slag (BFS) was contaminated with 2% and 5% Cs (with respect to the dry BFS mass) and alkali-activated with sodium silicate solution, while the AABFS samples were cured sealed in plastic envelopes for 24 h at 95oC. First series of AABFS samples were exposed to accelerated carbonation (open curing), while the second (reference) series of ABFS samples left to aging (also sealed) at room temperature until testing. Thereafter AABFS samples were subjected to a short-term (five-day) leaching tests according to the ANSI/ANS-16.1-2003 standard. The strength of AABFS mortars were tested according to the SRPS EN 196-1 standard, while the carbonation was confirmed by phenolphthalein test and SEM analysis. The diffusion coefficient (D) and non-dimensional leachability index (L) of cesium leached from ABFS were calculated according to the ANSI/ANS-16.1–2003 standard. A correlation between the accelerated carbonation process and the effectiveness of immobilization of cesium in AABFS was established

Tехнолошки поступак синтезе порозних материјала на бази алкално активиране смеше (композита) електрофилтерског пепела из термоелектране „Морава“ - Свилајнац и згуре високе пећи из железаре „Hesteel Serbia Iron & Steel, d.o.o.“ - Смедерево

Овим техничким решењем дефинисан је поступак синтезе порозних материјала на бази алкално активиране смеше (композита) електрофилтерског пепела из термоелектране ''Морава'' - Свилајнац и згуре високе пећи из железаре ''Hesteel Serbia Iron & Steel d.o.o.'' - Смедерево. Смеша ЕФП-ЗВП је алкално активирана при различитим масеним уделима ЕФП-ЗВП (100-0; 75-25; 50-50; 25-75; 0-100), употребом раствора натријум-силиката модула 1,5 при концентрацији од 10% Na2O у односу на масу смеше ЕФП-ЗВП. Као генератор пора употребљен је прах металног Аl који је додат у концентрацији од 0,2% у односу на масу смеше ЕФП-ЗВП. Испитиване су физичко-механичке карактеристике добијеног материјала – чврстоће на савијање и притисак после неговања на собној температури у трајању од 28 дана и израчуната запреминска маса синтетисаних порозних алкално активираних композита. Вредности чврстоће на притисак биле у опсегу од 1,17 до 2,92 МРа, док су вредности запреминске масе били у опсегу од 0,49 - 0,74 g/cm3. Добијене физичко-механичке карактеристике порозних алкално активираних композита поредиве су са физичко-механичким карактеристикама порозних материјала на бази портланд-цемента. Синтеза порозних материјала алкалном активацијом смеше (композита) ЕФП-ЗВП у нашој земљи представља нов поступак, којим се постиже искоришћење великих количина ових отпадних материјала, односно, валоризација ЕФП и ЗВП. Добијени порозни алкално активирани материјали могли би се користити као термоизолациони материјали за облагање грађевинских објеката.Tehničko rešenj

Chitosan and pectin-based films and coatings with active components for application in antimicrobial food packaging

This investigation was aimed to develop films and coatings based on natural biopolymers and active components, with physicochemical and functional properties for application in antimicrobial packaging. Biopolymer films were obtained from emulsions and dispersions by casting method. Coatings were formed by the application of emulsions on existing packaging. Synthesis of emulsions and dispersions were performed by combining biopolymers (chitosan-gelatin, pectin-gelatin) with lemongrass essential oil (LEO), Zn(CH3COO)2.2H2O, or ZnO, as active components. Fourier transform infrared (FTIR) spectra of the films showed that the addition of glycerol contributed to the forming of strong hydrogen bonds between glycerol and chitosan-gelatin or pectin-gelatin composites, facilitating the process of polymer branching, which is substantial for encapsulation. Thermal analyses revealed two characteristic processes occurring at 110 degrees C (water evaporation) and within 215-235 degrees C (degradation of polysaccharide and glycerol). Major weight losses were observed at 290 degrees C (chitosan-gelatin films) and 215 degrees C (pectin-gelatin films). The chitosan-gelatin films exhibited a lower degree of solubility (31-21%), and better mechanical properties comparing with the pectin-gelatin films. The chitosan-gelatin emulsions and dispersions exhibited a higher antibacterial effect in vitro against E. coli, B. subtilis, and S. aureus. In the case of the pectin-gelatin emulsions, the impact of LEO on the antibacterial activity was evident. The effects of biopolymer coatings on the development of microorganisms on fresh raspberries (Rubus idaeus L.) were performed in vivo during eight days of raspberry storage at refrigerator temperature. The tested coatings extended the shelf life of stored raspberries from four to eight days. The synergistic effect between LEO and ZnO or Zn-Ac was observed both in vivo and in vitro

Influence of silicon on polymerization process during lignin synthesis. Implications for cell wall properties

Silicon (Si) is considered a beneficial element for plants, mostly accumulating in cell walls, where its location and content are primed by the chemistry and structure of lignin. It is unrevealed how Si interacts with the process of lignin formation in the CWs. We studied, in an in vitro system, the interaction of SiO2 with the peroxidase-catalyzed polymerization of a lignin monomer into the lignin model compound, imitating conditions of the last step of lignin formation. FTIR and fluorescence spectroscopy and microscopy showed that Si is bound to the final polymer, and the structure of the Si-DHP differs from pure DHP. Fluorescence spectroscopy showed that Si does not bind to the monomers, so Si probably inhibits the formation of the larger lignin fragments, as evidenced by HPLC-DAD, by binding to dimmers formed during DHP synthesis. The structural changes of the polymer are related to the changed proportion of the fractions of various MW. The enzyme catalyzing DHP synthesis was not inhibited by Si. HRP activity was increased in presence of Si except for 6 mM Si. This may indicate that the complex formed with Si and short oligomers activates the enzyme, and prevents the formation of the large fragments

Chitosan and pectin-based films and coatings with active components for application in antimicrobial food packaging

This investigation was aimed to develop films and coatings based on natural biopolymers and active components, with physicochemical and functional properties for application in antimicrobial packaging. Biopolymer films were obtained from emulsions and dispersions by casting method. Coatings were formed by the application of emulsions on existing packaging. Synthesis of emulsions and dispersions were performed by combining biopolymers (chitosan-gelatin, pectin-gelatin) with lemongrass essential oil (LEO), Zn(CH3COO)2.2H2O, or ZnO, as active components. Fourier transform infrared (FTIR) spectra of the films showed that the addition of glycerol contributed to the forming of strong hydrogen bonds between glycerol and chitosan-gelatin or pectin-gelatin composites, facilitating the process of polymer branching, which is substantial for encapsulation. Thermal analyses revealed two characteristic processes occurring at 110 degrees C (water evaporation) and within 215-235 degrees C (degradation of polysaccharide and glycerol). Major weight losses were observed at 290 degrees C (chitosan-gelatin films) and 215 degrees C (pectin-gelatin films). The chitosan-gelatin films exhibited a lower degree of solubility (31-21%), and better mechanical properties comparing with the pectin-gelatin films. The chitosan-gelatin emulsions and dispersions exhibited a higher antibacterial effect in vitro against E. coli, B. subtilis, and S. aureus. In the case of the pectin-gelatin emulsions, the impact of LEO on the antibacterial activity was evident. The effects of biopolymer coatings on the development of microorganisms on fresh raspberries (Rubus idaeus L.) were performed in vivo during eight days of raspberry storage at refrigerator temperature. The tested coatings extended the shelf life of stored raspberries from four to eight days. The synergistic effect between LEO and ZnO or Zn-Ac was observed both in vivo and in vitro