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Održivo upravljanje otpadnom biomasom primenom novih metoda termohemijske konverzije
No full textSrbija godišnje generiše oko 3 miliona tona lignocelulozne otpadne biomase iz agro-industrijskog sektora koja se odlaže na otvorene deponije ili spaljuje, čime se ugrožava životna sredina i doprinosi emisiji gasova staklene bašte. Poslednjih go-dina velika pažnja javnosti okrenuta je naučno istraživačkom sektoru koji se bavi ispitivanjem novih metoda termohemijske konverzije biomase i njihovog potencijala u rešavanju problema održivog upravljanja otpadom. U ovom radu biće predstavljene dve najzastupljenije metode, piroliza i hidrotermalna karbonizacija. Obe metode danas se sve više koriste u cilju dobijanja bio-goriva, hemikalija i novih multifunkcionalnih materijala iz obnovljivih izvora
The effects of the phosphates mechanical activation
No full textThe investigation was conducted with an aim to increase the reactivity of the comminuted phosphate ore and to establish the optimal mechanical activation period of the grain mixture. In order to obtain complete insight into the process and phenomena of the phosphate grain mixture activation, a good understanding of the theoretical principles of the activation operation is necessary. In the experiments, the vibratory and planetary mills were used as activators. The obtained results pointed out that both amorphous and crystallized forms appeared within the Lisina ore deposit mixture due to the specific genetic conditions which rarely occur in the deposits. Such a heterogenic composition of the useful phosphoric part of the ore gave a variety of the results during the leaching. For the first time, the experiments of phosphate (apatite) mechanochemical activation from Lisina ore deposit were performed in order to improve its reactivity
Izučavanje procesa okrupnjavanja mlevenog krečnjaka radi primene u poljoprivredi
No full textPrimena krečnjaka je veoma široka, na svim „kiselim“ zemljištima u ratarstvu, voćarstvu, vinogradarstvu, hortikulturi i šumarstvu, za podizanje prinosa i kvaliteta proizvoda. Cilj je da se postigne optimalna pH vrednost zemljišta (pH u normalnom rastvoru KCl od 5 do 5,5). Kako se za ovu primenu uglavnom koristi i praškasti krečnjak iz raznih filterskih postrojenja, najveći problem pri njegovoj aplikaciji je rasipanje pri transportu i manipulaciji. Takođe dolazi do raznošenja te prašine sa zemljišta putem vetra. Sa druge strane krečnjak treba bude dovoljno sitan da bi se pod uticajem atmosferilija rastvorio i ravnomerno rasporedio u zemjištu Nakon preliminarnih opita okrupnjavanja utvrđeno je da se okrupnjavanje mlevenog litotamnijskog krečnjaka ležišta „Dobrilovići“, kod Loznice, može obaviti (jednostavnim i ekonomičnim) postupcima briketiranja i peletizacije. Postupci okrupnjavanja u najvećem broju slučajeva zahtevaju primenu vezivnih sredstava (u ovom slučaju bentonit), koja utiču na kvalitet (mehanička svojstva) gotovih proizvoda (briketa i peleta). Iz tih razloga je osnovni zadatak ispitivanja izvršenih u okviru ove doktorske disertacije bio da se ispita uticaj različitih postupaka okrupnjavanja na kvalitet tj. hemijski sastav, granulometrijski sastav, otpornost na udar, otpornost na pritisak i dezintegraciju u vodi proizvoda okrupnjavanja (briketa i peleta) dobijenih od litotamnijskog krečnjaka ležišta „Dobrilovići“, kao i njihovu rastvorljivost u vodi, a ispitivan je i uticaj vetra na raznošenje materijala tokom primene. Takođe, na briketima i peletima su urađene DTA/TG analiza, analiza FT-IR i SEM analize. Sagledavanjem rezultata dobijenih ispitivanjem mehaničkih osobina dobijenih briketa i peleta možemo reći da je moguće dobiti proizvod zahtevanih karakteristika za potrebe poljoprivrede, a to su uzorci briketa sa masenim udelom veziva od 10% za sve radne pritiske prese (2, 5, 10, 15, 20 i 25 kN), kao i tri uzorka briketa sa masenim udelom veziva od 5%, pri visokim i najvišim vrednostima radnog pritiska prese (20 i 25 kN). Ovo predstavlja ispunjenje jednog od ciljeva izrade ove disertacije – „Utvrđivanje optimalnih parametara u procesu okrupnjavanja“, kao i potvrdu hipoteza predstavljenih u postavci disertacije. Dakle, sa aspekta održanja kvaliteta hemijskog sastava krečnjaka za potrebe poljoprivrede, kao i ekonomije, sadržaj vezivnog sredstva treba da bude kontrolisan I nizak, dok sa aspekta mehaničkih karakteristika učešće veziva treba da bude što veće. Mada ocena ekonomičnosti navedenih postupaka nije izvedena logično je da smanjenje veziva doprinosi smanjenju troškova. Rukovodeći se ovim saznanjima, uz jasnu težnju da se kvalitet dobijenih proizvoda okrupnjavanja (peleta i briketa) održi u zahtevanim granicama, izvedena ispitivanja pokazuju da se najkvalitetniji proizvodi dobijaju postupkom briketiranja i to pri svim oblastima radnog pritiska prese, od niskog preko srednjeg do visokog, kao i pri različitim udelima vezivnog sredstva. Prethodni zaključak pokazuje da je postavljeni cilj – dobijanje kvalitetnog proizvoda okrupnjavanja na mlevenom krečnjaku ostvaren, što je istovremeno I praktični doprinos ove disertacije. Istovremeno je pokazano da postoji veza između postupka okrupnjavanja, uslova okrupnjavanja, kao i udela vezivnog sredstva sa kvalitetom dobijenih proizvoda.Wide application of limestone on the „acidic“ soils in farming, fruit growing, viticulture, horticulture and forestry, for increase in yield and quality of products. The aim is to achieve the optimal pH value of soil (pH in normal solution of KCl, in the range between 5 and 5.5). For this purpose, the most often material that is aplicated is the powdered limestone from a variety of filter plants. The great problem, connected with application of powdered material is wastage during transport and manipulation. Additionally, the spreading the dust from the land by the wind is present. On the other hand, limestone should be fine grinded so it could be diluted and evenly distributed into the soil under the atmospheric influence. After the preliminary trials, it was concluded that agglomeration of grinded litotamnian limestone form the „Dobrilovići“ deposite, near Loznica, could be done (simply and economically) using briquetting and pelletization process. Agglomeration processes, in the most cases, demand application of binding agens (bentonite, in this case), which influences the quality (mechanical characteristics) of the final products (briquettes and pellets). The aim of this doctoral dissertation is to investigate the influence of the different agglomeration processes on the quality, e.g. chemical composition, granulometrical composition, impact resistance, compressive strength as well as disintegrating in water, of the agglomeration products (briquettes and pellets) produced using the litotamnian limestone from the „Dobrilovići“ deposite. Additionally, the water solubility and the influence of the windage loss during application. Also, the DTA/TG, FT-IR and SEM analysis were done. The results obtained from the investigation of mechanical characteristics of obtained briquettes and pellets it could be concluded that it is possible to get the product with required characteristics for the agriculture application. These are briquette samples with 10wt.% of binder for press at all operating pressures (2, 5, 10, 15, 20 and 25 kN), as well as three briquette samples with 5wt.% of binder, under the high and highest values of operating pressure (20 and 25 kN). This represents the fulfillment of one of the objectives of this doctoral dissertation - „Establishing the optimal parameters in agglomeration process“, as well as the confirmation of the hypotheses put into the setting of dissertation. So, from the point of the aspect of maintaining the quality of chemical composition of the limestone for the agriculture purposes, as well as the economy, the binder content should be low and controlled. On the other hand, from the point of mechanical characteristics, the binder content should be as high as possible. Even though economic evaluation of these procedures is not provided, it is logical that the reduction of binders content leeds to costs reduction. Guided by these findings, with a clear tendency that the quality of the obtained agglomeration products (pellets and briquettes) keep the required limits, provided investigation showed that the highest quality products can be obtained by briquetting process for all operating pressures, from low to high, as well as for different amounts of binder. The previous conclusion shows that the set goal – obtaining the quality agglomeration product from grinded limestone is achieved, which was, at the same time, the practical contribution of this doctoral dissertation. At the same time, the connection between the agglomeration process, the conditions of agglomeration, as well as the binder amount with the quality of obtains product is established
Monitoring of Krivelj river collector deformation
No full textStudy of monitoring and analyzing the deformation of the collector Krivelj River. has been developed. In the period May - July 2009, the recording of the measurements and the state of the crack deformation in reinforced concrete collectors lining was performed.
Based on analysis of the recording, four characteristic lining deformation of the shape in vulnerable parts of the collector were identified: in calotte, on the sides of calotte, sides themselves, and sides of ducts.
Deformations in calotte zone were in form of tension cracks, reinforcement tears and separation of concrete from the reinforcement created due to high tensile stresses in the inner part of the reinforced concrete lining. The worst damage was observed due to shear stresses in the lateral parts of the calotte, while the cracks in some parts exceeded 10 cm. These are very large and dangerous damages to the collector. Given that there was a fracture of concrete, loads in those areas was taken over by the armature, which was affected by severe corrosion. Due to the large vertical pressures and the tendency for flattening of the collector in internal lateral parts of support, there was erosion of concrete in the form of plates. Small cracks appeared in the side parts of the collector ducts, too.
For collector cross sections recording, in addition to the geodetic procedure, rotating laser beam procedure was applied. Based on these recordings it can be concluded that the profile of the collector, on his damaged sections, is ""flattened"". The laser process enables easier, faster and more credible measurements of the size and shape of the profile, which may be of particular importance when installing frameworks for future temporary and permanent rehabilitation of vulnerable sections of the collector.
Changes in the deformation of the ten selected places in collectors were observed using embedded devices for measuring deformation cracks in collector reinforced concrete support. Final results of monitoring changes in absolute and relative deformation of reinforced concrete collector of over time show that established shifts arc part of the process of reinforced concrete roof supports deformation, which is directed towards the fracture and support breaking
Stability of lead ethyl xanthate on galena surface
No full textThe stability of lead ethyl xanthate (ethyl xantate ion C2H5OCS2- , EX-) on galena (PbS) surface in an alkaline medium (pH=9-12) was investigated using ATR-IR and UV spectrophotometric methods. The prolonged time of mineral treatment with ethyl xanthate solution up to 4 hours, at pH=9.2, did not affect the surface adsorbed ethyl xanthate. However, within pH range 10-12, the decomposition of surface layer occurs. The ethyl monothiocarbonate ion EMTC- (monothiocarbonateCO2S2− ) is an intermediate product of lead ethyl xanthate decomposition
(Pb-Sb)-bearing sphalerite from the Cumavici polymetallic ore deposit, Podrinje Metallogenic District, East Bosnia and Herzegovina
No full textCumavici is a medium- to low-temperature hydrothermal Sb-Zn-Pb-Ag polymetallic vein-type ore deposit in the Srebrenica orefield, part of the Podrinje Metallogenic District, Eastern Bosnia and Herzegovina. The ore deposit occurs in the form of simple and complex veins along faults and fractures, as well as stockworks and disseminations hosted within Neogene volcanic rocks (pyroclastics and andesite lavas of calc-alkaline affinity). The deposit comprises sulfides (sphalerite, galena, stibnite, pyrite, marcasite, chalcopyrite, arsenopyrite, gudmundite, safflorite, lollingite, gersdorffite and acanthite), sulfosalts (berthierite, geocronite, boulangerite, semseyite, plagionite, jamesonite, boumonite, twinnite, andante, fizeliyte, Ag-bearing tetrahedrite, stephanite, polybasite, pyrargyrite and argyrodite), native gold and silver, tungstates (hubnerite), oxides, and gangue quartz, chalcedony, Mn-siderite, anglesite, smithsonite, fluorite, gypsum and ludlamite. Three generations of sphalerite are recognized in the Cumavici deposit, evolving from Fe-rich to Fe-poor. The most common are yellowish to colorless Fe-poor varieties. Electron Probe Microanalyses of sphalerite free of micro-inclusions of galena and Pb-Sb-sulfosalts revealed wide compositional variations in minor- and trace-element contents (e.g., Fe, Cd, Mn, Cu, Sn, As, and In). Of particular interest are the lead and antimony content of sphalerite, which vary from 0.10 to 3.08, and 0.02 to 1.62 wt.%, respectively. Lead- and Pb-Sb-rich zones are the most common in sphalerite, while individual Sb-bearing zones are rare. These zones have fan-like forms with circular to wave-like, micron-scale bands, filled with galena or Pb-Sb sulfosalts. In the Pb-Sb zones, the Sb/Pb atomic ratio ranges between 0.3 and 1.5, similar to ratios between geocronite and jamesonite, thus suggesting the presence of micro- to nano-scale inclusion of sulfosalts within the sphalerite. The mean composition of all sphalerite samples is (Zn0.78-0.99,Fe LT 0.01-0.21,CU0.00-0.02,Pb LT 0.01-0.01,Cd LT 0.01-0.01,Sb LT 0.01-0.01,Mn LT 0.01-0.01)(Sigma) S-0.97-1.03(0.97-1.08) (Sn and As atomic proportions are LT 0.01 apfu). In all sphalerite samples, excellent negative correlations have been determined between Fe and Zn, and Sigma (Fe + Sb) and Zn. The studied mineralization shares many mineralogical and geological characteristics in common to polymetallic Sn-Ag-Sb deposits in Bolivia and elsewhere
Mineralogy and genetic characteristics of the Rudnik Pb-Zn/Cu,Ag,Bi,W polymetallic deposit (Central Serbia) - New occurrence of Pb(Ag)Bi sulfosalts
No full textAschamalmite, ideally Pb6-3xBi2+xS9, ordered monoclinic homeotype of heyrovskyite from the Rudnik Pb-Zn/Cu,Ag,Bi,W polymetallic deposit in the central part of Serbia has been investigated. This polymetallic deposit includes over 90 hydrothermal and skarn-replacement orebody types, primarily hosted by Cretaceous sediments and occassionally by Oligocene dykes and sills of dacitic composition, and contact-metamorphic-metasomatic rocks. These rocks are host to an assemblage of pyrrhotite, colloform pyrite, chalcopyrite, galena, arsenopyrite, native bismuth and scheelite as well as minor pyrite, sphalerite, bismuthinite, argentopentlandite, and native silver. The chemical composition of the ore is very complex, where weight contents of valuable metals range as follows (%): Zn 0.49-4.49; Pb 0.90-5.66; Cu 0.08-2.18; WO3 0.05-1.18; Ag 0.005-0.030; Bi 0.005-0.081; and Cd 0.002-0.016. Well-developed aschamalmite crystals have not been observed, only stocky and spindle-like aggregates up to 10 mm in length intergrown with sulfides. Electron-microprobe analysis gave the average crystallochemical formula (Pb5.82Ag0.20)(Sigma 6.02)Bi-2.03(S8.93Te0.02Se0.01)(Sigma 8.96). The strongest diffraction reflections of the X-ray powder diffraction pattern [d(in angstrom)(I)] are: 3.419(100), 3.382(92), and 3.334(66). Monoclinic unit-cell parameters are a=13.727(7); b=4.122(3); c=31.32(2)angstrom; beta=90.72(5)degrees; and V=1771.8(1)angstrom(3). Mineral assemblages and genesis of the Rudnik polymetallic deposit are discussed in detail and the thiobismuthite mineralization has been compared with similar well-known deposits
Wetting phenomena of grooves at liquid metal/ceramics interface
No full textThe grain boundary groove (GBG) developing at the ceramic substrate under the liquid metal is evident, yet not fully explained influencing appearance in describing the wetting phenomena at liquid metal/ceramics interface. The focus here is on modelling of the phenomena at/around a groove between grains depending on grooves' geometry. Based on atomic force microscopy results, the groove efficiency assessment is provided as a function of the transferred mass quantity and related to grooves geometry. The transferred mass quantity and, according to it, the groove efficiency at parabolic GBG is about 10% higher comparing to the triangular GBG
Hydrochars, perspective adsorbents of heavy metals: A review of the current state of studies
No full textKao alternativa pirolizi, hidrotermalna karbonizacija je predložena kao perspektivan pravac konverzije širokog spektra otpadnih biomasa u biogoriva, adsorbente i specifične hemikalije. U ovom preglednom radu predstavljena su aktuelna istraživanja primene različitih otpadnih biomasa, kao prekursora za dobijanje hidročađi - efikasnih adsorbenata teških metala iz otpadnih voda postupkom hidrotermalne konverzije. Efikasnost biosorbenata je diskutovana u odnosu na strukturne karakteristike, reakcione parametre, sorpcione kapacitete i mehanizme, kao i predložene metode poboljšanja površinske reaktivnosti hidročađi. Sveukupno, biosorpcija hidročađima je identifikovana kao dobra alternativa konvencionalnim tehnologijama uklanjanja toksičnih metalnih jona iz otpadnih voda.As an alternative to dry pyrolysis, hydrothermal carbonization has been proposed as a promising route for conversion of different wastes into biofuels, adsorbents and specific chemicals. Herein, the application of a wide range of waste biomasses as precursors to obtain hydrochars - efficient adsorbents of heavy metals from wastewaters, using hydrothermal conversion, was reviewed. The efficiency of biosorbents has been discussed with respect to the structural characteristics, reaction parameters, sorption capacities and mechanisms, as well as proposed methods of improving hydrochar's surface reactivity. Altogether, biosorption with hydrochars has been identified as a proper alternative to the existing technologies applied for the removal of toxic metal ions from wastewater streams
Removal of Cs Ions from Aqueous Solutions by Using Matrices of Natural Clinoptilolite and its Safe Disposal
No full textThe possibility to use natural zeolite - clinoptilolite as a host material for radioactive Cs immobilization has been investigated. Cs-exchanged form of clinoptilolite which was prepared by treatment of clinoptilolite powder with 0.25 M CsCl solution was compacted. Both, powder and powder compact of exchanged clinoptilolite were thermally treated at 1200 C-0. The XRPD analysis showed that Cs was successfully immobilized after heat treatment by formation of stable cesium dodecaoxo-alumopentasilicate in both, powder sample and compact. The newly formed compound showed satisfactory Cs ions retention during leaching test. The sintered compact showed somewhat better resistance to Cs leaching than the thermally treated powder. The compressive strength of sintered compact was close to 200 MPa which is more than enough for easy handling and safe storage