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Corrodive cracks from flux residuals after brazing of thin leaves at an artistic desk lamp
No full textIzrada jednog umetničkog dela obično uključuje brojne različite tehnologije. To podrazumeva da je za razumevanje eventualno prisutnih nepravilnosti potrebno znati puno tehničkih detalja. Tehnologija lemljenja je jedna od njih, ispitivanje integriteta, takođe. Tehnologija lemljenja, uopšte, se razvijala na empirijski način, uglavnom pokušajima i greškama. Osnovnu teškoću čini realna situacija, koja je veoma složena, usled prisustva velikog broja uticajnih veličina, neke od njih se ne mogu lako prepoznati. Veliki problem je pojava pukotina u periodu posle čišćenja, tj. po završetku lemljenja, a to znači nekada posle više godina ili decenija. Dobar zalemljeni spoj mora biti valjano fizički i hemijski spojen. Jedna od primenljivih metoda ispitivanja je radiografsko ispitivanje, kada debljina ispitivanih delova obično ne predstavlja problem. Ovde izvedena radiografska ispitivanja su nagovestila prisustvo nekih indikacija samo na listovima. Penetranstsko ispitivanje je sledeći korak za ispitivanje površine. Registrovanje indikacija i njihovo lociranje su neophodni koraci u svakom daljem pristupu u cilju uklanjanja takvih diskontinuiteta. Izbor metode reparacije uvek je poseban problem, dakako u celoj tehnici, a posebno na osetljivim umetničkim predmetima. Svako delovanje u reparaciji ili restauraciji može dovesti do manje ili više vidljivih tragova. Neodgovarajuća delovanja mogu dovesti do manje ili više vidljivih tragova. Ovde je pokazana jedna nepravilnost (pukotina) na zalemljenom listu, na jednoj umetničkoj stonoj lampi.Making of an artistic piece usually includes a number of different technologies. It implies that for understanding of eventually present irregularities one should knows a lot of technical details. Brazing tehnology is one of them, inspection of integrity, also. Brazing technology generally has evolved on empirical manner, mainly by trial and error(s). The basic difficulty in this technology is that the real situation is highly complex due to the presence of large number of variables, some of them may not be easy to recognize. The great problem is the appearance of crack(s) in postcleaning periode, i.e after brazing is finished, it means over years or decades. A good braze joint must be both physically and chemically bounded. One of the available method for investigation is radiographic testing, when the thickness of testing components commonly does not represents a problem. Here provided radiographic testing has revealed the existence of some indications only at leaves. The indications usualy mean discontinuity in material homogenity. Penetrant testing is a next step for investigation of surface. Registration of indications and their locations are necessary steps in any further approach for removing such discontinuities. Choosing the repair method always is particular problem, however in entire technique, especially on sensitive artistic component(s). Every action in repairing or restauration may led to more or less visible traces. Unadequate actions may permanently change the appearance or usage of treated artefact. Here is shown one irregularity (crack) at one brazed leaf from an artistic desk lamp
The distribution and retardation coefficients as a tool in selection of low-cost sorbent as a material for permeable reactive barrier – SEM-EDS analysis
No full textIntroduction
A permeable reactive barrier (PRB) is considered as an innovative, green engineering approach for
remediation of contaminated groundwater, using a passive, in situ technology with high potential of treatment
of contaminant plume at in a cost-effective manner. Recently, scientific investigations are focused on
discovering of materials for PRB which are abundant in nature or are waste material from another process. In
this study, distribution and retardation coefficient were used as a tool to select various natural materials such
as natural zeolites, clays and apatite as a material for PRB for removal of heavy metals lead, cadmium, zinc
and cooper from contaminated groundwater. In addition, scanning electron microscopy (SEM) analysis and
semi-quantitative energy dispersive spectrometry (EDS) of selected sorbent were analysed before and after
saturation with the best removing metals.
Experimental Methods
The following sorbents were investigated: natural zeolite, NZ (Zlatokop deposit,Vranjska Banja, Serbia),
IMZ (prepared by modification of natural zeolite), bentonite (Šipovo deposit, Bosnia), apatite (ore deposit
Lisina, Bosilegrad, Serbia), concentrate apatite (prepared from apatite), kaolin (plant for production of quartz
sand, Rgotina Serbia) (Ugrina et al., 2017). All samples were analysed on sorbent density and sorbent
porosity (results not given here). Batch sorption experiments are performed by mixing metal ion (Pb, Cu, Zn
or Cd) solutions with each sorbent, at solid/liquid ratio of 10 g/l, during 48 hours at room temperature. The
leaching experiment included evaluation of metal released from saturated sorbents in ultrapure water with
adjusted pH values in range 6.07-6.47. SEM-EDS of selected sorbent were analysed on a JEOL JSM-6610
instrument.
Results and Discussion Distribution coefficient Kd (l/g) and the retardation
coefficient Rd (-), are calculated using the following
equations:
where co and ce are the initial and equilibrium metal
concentrations (mmol/l), V is the metal solution
volume (l), m is the sorbent mass (g), is the sorbent
density (g/cm3), is the sorbent porosity (-). Figure 1
represents the results of retardation coefficient.
Based on calculated distribution and retardation coefficients using equation (1) and (2), raw bentonite and
IMZ showed the highest removal potential for zinc, cadmium and lead, while raw bentonite was the best
option for cooper removal, as in system of Cu-IMZ, adjustment of pH was necessary in order to avoid
precipitation. Beside the distribution and retardation coefficients, the leaching test in ultrapure water solution at pH=6.07-6.46 was performed and leaching of lead and cadmium from raw bentonite was noticed. This indicates that distribution and retardation coefficients are not sufficient for selection of material for PRB, as secondary pollution as a consequence of leaching cannot be predicted. Thus, based on retardation coefficients and performing leaching test, selected low-cost sorbents with the best removal properties for investigated heavy metals are: raw bentonite and IMZ for zinc ions, raw bentonite for cooper, and IMZ for lead and cadmium.
SEM-EDS analysis is giving insight into surface characterization of selected sorbents before and after saturation with certain heavy metals (Figure 2.)
Non-isothermal analysis of nucleation the Li2O-GeO2-Al2O3-P2O5 glass
No full textThe nucleation of powder glass from the system Li2O-Al2O3-GeO2-P2O5 was studied. The investigations were performed under non-isothermal conditions using the DTA method. The field of nucleation is determined. It was observed that there is possibility of simultaneous nucleation and crystal growth in glass. Dependence (Tp-1)max of Tn is linear for studied glass system
Grape pomace hydrochar as an efficient adsorbent for cadmium removal
No full textHydrochar prepared from the hydrothermal carbonization of the grape pomace was investigated as potential adsorbent for the Cd from aqueous solution. To increase the sorption efficiency, the hydrochar was modified using the different chemical treatments (citric acid (CA), H2O, and KOH) and characterized by a FTIR spectroscopy. The preliminary adsorption tests showed that the adsorption capacity of hydrochars was 3.8 before and 5.0, 14.5 and 49.34 mg/g upon modification by CA, HO and KOH, respectively. It was observed that the KOH activation enhances the surface functionality of the hydrochar, and thus significantly improves the Cd adsorption capacity. Therefore, the KOH-modified hydrochar should be considered as an efficient adsorbent for Cd removal
Dobijanje koncentrata liskuna iz kaolinisanog granita postupkom flotiranja
No full textKaolinisani granit čine kaolin, feldspat, kvarcni pesak i liskun. Nakon odvajanja kaolinske komponente koja se nalazi u najsitnijoj frakciji ispod 0,043 mm i frakcije iznad 0,63 mm, ostaje klasa -0,63+0,043 mm koja sadrži kvarcni pesak, feldspat i liskun. U radu su dati rezultati flotiranja liskunskih minerala iz polimineralne sirovine uzete iz ležišta „Bašića bare“ – Kobaš, Srbac, Republika Srpska. Rezultati su pokazali da se postupkom flotacijske koncentracije može dobiti koncentrat liskuna, dok u otoku flotiranja ostaju feldspat i kvarcni pesak. U koncentratu liskuna sadržaj SiO2 je 52,70%, a Al2O3 24,6%. Rendgenskom difrakcionom analizom je određen semikvantitativni udeo pojedinačnih minerala: liskuni ~55%, minerali hlorita/glina ~35%, kvarc ~5%, plagioklasi i K-feldspati zajedno ~5%
Hydrogen genaration in mechanocemical reactor
No full textHydrogen is considered to be be the fuel of the future. Fuel cells allow that the change of Gibbs function can provide maximum electrical work. Activation with mechanochemical treatment of mineral matter represents a technology that enables us to get fuel with high heat of combustion. The hydrogen generator represents a mechanochemical reactor or a mill with balls in whose operating cylinder is the metal creator in view of grinding bodies, water and abrasive. It is interesting to notice the fact that we calculated the work of the mill (reactor) in the dimension A(=) Jmol-1. It is also important the fact that one of the balls in a mill (reactor) mass m = 6.5 g, in the process of MH treatment, with its operation on the mineral grain size d = 100 um creates the pressure of 0.65 MPa
Characterization of the zeolitic tuff from the “igroš-vidojevići” deposit regarding geological and technological aspects
No full textThis study presents investigations of zeolitic tuff samples from the “Igroš--Vidojevići” deposit. The aim of the research was to determine the quality of samples taken from all deposit parts. Thus, samples were taken from the footwall (“Zeolit 1”), and four samples from the central deposit part (“Zeolit 2”, “Zeolit 3”, “Zeolit 4” and “Zeolit 5”). Characterization of the samples included chemical analysis, determination of the adsorption coefficient for methylene blue dye and cation-exchange capacity (CEC), X-ray powder diffraction analysis (XRPD), differential thermal and thermogravimetric analysis (DTA and TGA), and Fourier transform Infrared spectroscopic analysis (FTIR). Results have shown that the footwall consists mostly of clays, whereas zeolite minerals dominate in the rest of the deposit. XRD analysis of the “Zeolit 1” sample confirmed presence of smectite and kaolinite clays, while zeolite of analcime type and quartz are present as smaller fractions. Chemical composition analysis and determination of heavy metal contents showed a significant amount (7.58%) of Fe2 O3 in this sample. Therefore, further research can be pursued to find a method for removal of magnetic impurities in this deposit portion in order to utilize the clay fraction. On the other hand, according to XRD, FTIR, DTA/TGA and SEM/EDS analyses, samples which belong to the central deposit part (“Zeolit 2–5”) consist of clinoptilolite zeolite type, while clays are present in less than 10%. Thus, clays (smectites and kaolinite) accompanied with analcime and quartz are the most abundant footwall minerals while central deposit parts contain predominantly clinoptilolite accompanied with small amounts of clays. Mineragenetically, zeolites are most abundant in the “Zeolit 2” and “Zeolit 3” samples. The smallest value of CEC was determined for the “Zeolit 1” sample (46.98 mmol/100g). According to CEC values determined for “Zeolit 2” and “Zeolit 3” (141.99 and 121.01 mmol/100 g, respect-ively) these samples are of the best quality, and could be utilized as adsorbents of inorganic pollutants from contaminated waters. Moreover, they could be potentially used for removal of mycotoxins from cattle feed. “Zeolit 4” and “Zeolit 5” samples have shown slightly lower CEC values (89.48 and 83.75 mmol/100 g, respectively), which implies lower quality, and, therefore, could be used for soil quality improvement. Finally, determination of the external CEC has revealed a significant difference between “Zeolit 1” and “Zeolit 5” samples (17.9 and 5.31 mmol/100 g, respectively)
The effect of alternations in mineral additives (zeolite, bentonite, fly ash) on physico-chemical behavior of Portland cement based binders
No full textInstrumental analyses accompanied by analytical modeling tools were employed to assess physico-chemical changes induced by variations in chemical composition of cementitious composites, i.e. mortar binders. Coal combustion ash was utilized as pozzolanic mineral additive. The binders' mix-design was supplemented with sorptive clays to prevent migration of toxic elements from fly ash. The experiment was established on the premise of clay's ion-exchanging ability. Ten binders comprising cement CEM I 42.5 and fly ash, zeolite and/or bentonite additions were prepared in accordance with chemometric experimental design rules. Chemical composition was determined via XRF method. The changes in mineral phases and crystallinity were traced by X-ray diffraction. Hydration mechanisms and thermal behavior were investigated via DTA/TGA. The chemical bonds were identified by FTIR. Morphology of hardened samples was detected by SEM. Mathematical tools employed data sets of instrumental analyses to form a clear differentiation between binders and to assess changes caused by adoption of mineral additives in the mix designs. Sorptive clays showed pozzolanic behavior, thereby causing no incapacitation to the cement hydration mechanism, and classifying as a possible economical resources which can be used in production technology of construction materials to redeem environmental pollution issues of building industry
In vitro removing of mycotoxins by using different inorganic adsorbents and organic waste materials from Serbia
No full textAflatoksin B1 (AFB1), ohratoksin A (OTA), zearalenon (ZON), dezoksinivalenol (DON) i T-2 toksin su najviše izučavani toksični metaboliti gljiva. Kada mikotoksini uđu u proizvodni lanac za hranu/hranu za životinje, zadržavajući svoje toksične karakteristike, teško ih je ukloniti ili eliminisati. Jedna od obećavajućih metoda za smanjenje nivoa mikotoksina u kontaminiranoj hrani/hrani za životinje je korišćenje mikotoksinskih veziva. Ovaj rad predstavlja rezultate in vitro istraživanja mineralnih mikotoksinskih veziva (bentonit - BEN, diatomit - DIA i zeolit - ZEO) i organskih veziva mikotoksina - poljoprivrednog otpadnog materijala (Myriophillium spicatum, koštice breskve i višnje). Hemijski sastavi adsorbenata pokazali su da ne sadrže elemente toksične za životinje. Neorganski adsorbenti (BEN, DIA i ZEO) testirani in vitro bolje su vezivali AFB1 (94,97% - 96,90%), dok su biosorbenti bili efikasniji u adsorpciji OTA (19,98% - 66,66%), ZON-a (33,33% - 75,00% ) i T-2 toksina (16,67% - 50,00%). Neorganski adsorbenti i organski otpadni materijali su pokazali sličan kapacitet in vitro vezivanja DON-a, sa izuzetkom M. spicatum koji uopšte nije adsorbovao ovaj trihotecen tipa B. Naši rezultati koji su prikazani ovde pokazuju da zagađivanje hrane i hrane za životinje različitim vrstama mikotoksina može biti smanjeno dodavanjem preparata dobijenog kombinacijom različitih neorganskih i organskih adsorbenata koji poseduju različite karakteristike vezivanja mikotoksina.Aflatoxin B1 (AFB1), ochratoxin A (OTA), zearalenone (ZON), deoxynivalenol (DON) and T-2 toxin are the most extensively studied toxic fungal metabolites. Once mycotoxins enter the food/feed production chain keeping their toxic characteristics, it is very difficult to remove or eliminate them. One of promising methods to reduce mycotoxins in contaminated food/feedstuffs is the use of mycotoxin binders. This paper presents the results of in vitro investigations of mineral mycotoxin binders (bentonite - BEN, diatomite - DIA and zeolite - ZEO), and organic mycotoxin binders - agricultural waste materials (Myriophillium spicatum, peach and sour cherry pits). Chemical compositions of the adsorbents have showed that they do not consist of elements toxic to the animals. Inorganic adsorbents (BEN, DIA and ZEO) tested in vitro were better binders of AFB1 (94.97% - 96.90%), while the biosorbents were more efficient in adsorption of OTA (19.98% - 66.66%), ZON (33.33% - 75.00%) and T-2 toxin (16.67% - 50.00%). Inorganic adsorbents and organic waste materials expressed similar binding capacity for DON in vitro, with the exception of M. spicatum that did not at all adsorb this type B trichothecene. Our results indicate that feed contamination with different types of mycotoxins might be diminished by a product that combines different inorganic and organic adsorbents with diverse mycotoxin binding properties
Study of heavy metals biosorption on native and alkali-treated apricot shells and its application in wastewater treatment
No full textLocally available apricot (Prunus armeniaca L.) shells classified as a waste product from fruit processing, were alkali activated in order to develop an efficient heavy metal ions sorbent for water purification. To examine the changes occurred after alkali treatment, raw (SH) and modified apricot shells (SHM) were thoroughly characterized in terms of their chemical composition and surface properties. Chemical analysis revealed that alkaline treatment causes the disintegration of hemicellulose (its content decreased from 19.2 to 3.5%), which was in accordance with FTIR results. SEM micrographs and the mercury intrusion porosimetry revealed a larger surface area and porosity of SHM. Bohem's acid-base titration method indicated that the most of the SHM surface carboxylic groups were in sodium salt form and together with the pH of points of zero charge showed increase of surface alkalinity after modification. Treatment with NaOH enhanced the adsorption capacity by 154, 61 and 90% for Cu2+, Zn2+ and Pb2+, respectively. The amount of cations released from SHM was almost equal to the amount of adsorbed metal ions, suggesting ion exchange mechanism. The pseudo-second order kinetic indicated that the heavy metals cations were bound predominantly by complexation. In order to establish the effectiveness of the biosorbent in real wastewater sample, SHM was employed for cleaning-up of drain water emanating from atomic adsorption spectrophotometer. The SHM showed high removal efficiency towards multiple metal ions. The amounts of Fe, Pb, Cu and Cr ions were reduced by 97, 87, 81 and 80%, respectively, while Ni and Zn amounts were reduced for 33 and 14%. Used biosorbent SHM can be successfully regenerated with HCl (desorption > 95%) and after regeneration biosorbent can be reused or it can be safely disposed