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Fourier-Transform Infrared Spectroscopy Analysis of Mechanochemical Transformation Kinetics of Sodium Carbonate to Bicarbonate
No full textDuring mechanical activation, qualitative changes that can produce various phenomena occur in the material. In this study, anhydrous sodium carbonate was mechanically activated for 2, 7, 14, and 28 minutes in a vibro mill at a frequency of 3000 oscillations per minute. After activation, four series of activated samples were stored in the air at room conditions for 31 days (relaxation period). To monitor the kinetics of the transformation process of activated sodium carbonate samples, i.e. the mechanism of sodium bicarbonate formation during relaxation, Fourier-transform infrared (FTIR) spectroscopy analysis was used. FTIR testing was performed as a function of relaxation time for all four series of samples, with characteristic groups observed: CO32-, HCO3- and OH-. The obtained results provided kinetics parameters for the transformation of sodium carbonate into sodium bicarbonate due to the chemisorption of moisture and carbon dioxide from the atmosphere
Significance of infrared spectroscopic branching factor for investigation of structural characteristics of alkanes, geochemical properties and viscosity of oils
No full textA detailed investigation of significance of the infrared (IR) spectroscopic branching factor (CH2/CH3; the ratio of methylene and methyl group peak heights at 2917-2921 and 2951-2954 cm(-1), respectively in the IR spectra) for characterization of alkane structure, geochemical properties and viscosity of 76 oil samples was performed. These oils, originating from 13 Serbian oil fields in SE Pannonian Basin, differ according to source and depositional environment of organic matter (OM), as well as by thermal maturity and biodegradation stage. Methylene and methyl asymmetric stretching peak absorbances were used for the branching factor calculation. CH2 peak positions exhibited 3-4 cm(-1) red shift with increasing the CH2/CH3 ratio, due to a greater contribution of trans vs. gauche rotamers in aliphatic chains. Comparing IR spectra of the oils and model n-alkanes, it was established that the average (CH2)(n) methylene chain length per CH3 group varied from n = 3.5 to 6.5. The CH2/CH3 ratio showed significant concordance with geochemical parameters, enabling clear distinction of the oils according to source and depositional environment of OM. At the same time, dependence of the CH2/CH3 ratio on oil maturity in the range from immature to mature was not observed, allowing for an accurate determination of oil genetic types irrespective of maturity. The CH2/CH3 ratio showed good accordance with oil biodegradation scale and oil viscosity
Adsorpcija odabranih lekova na LDPE, PA i PET mikroplastici
No full textUnappropriated disposing of unused drugs leads to an increase in their concentration in the
environment. Furthermore, wastewater treatment plants are not sufficient to prevent the
transport of drugs. Microplastics (MPs), which are also recognized as important pollutants,
can be divided into primary and secondary. The primary MPs are produced for commercial
purposes, while the secondary MPs are formed by the decomposition of plastic residues.
The hydrophobic nature and large specific surface area of MPs facilitate pollutants
binding. Animals misunderstand MPs for food and consume it, which could have harmful
health impacts because both MPs and adsorbed pollutants are ingested. In this paper, the
adsorption of the selected drugs - azithromycin, carbamazepine, sulfamethoxazole, and
diclofenac on low-density polyethylene (LDPE), polyamide (PA), and poly(ethylene
terephthalate) (PET) microplastics are presented. The experiment showed that drugs bind
best to PA and that azithromycin has the highest binding affinity.Neadekvatno odlaganje neiskorišćenih lekova dovodi do povećanja njihove koncentracije u životnoj sredini. Pored toga, postrojenja za prečišćavanje otpadnih voda nisu dovoljna barijera za sprečavanje transporta lekova. Mikroplastika (MP), koja je takođe detektovana kao bitan polutant, može se podeliti na primarnu i sekundarnu. Primarna se proizvodi za komercijalne svrhe, a sekundarna nastaje razgradnjom plastičnih ostataka. Hidrofobna priroda i velika specifična površina MP olakšava adsorpciju polutanata na ove materijale.
Životinje mešaju MP sa hranom i unose je u svoj organizam, što može imati negativni uticaj na njihovo zdravlje, jer se tako unose i MP i adsorbovani polutanti. U ovom radu je prikazana adsorpcija odabranih lekova - azitromicina, karbamazepina, sulfametoksazola i diklofenaka na sledećim vrstama mikroplastike - polietilenu niske gustine (LDPE), poliamidu (PA) i poli(etilen tereftalatu) (PET). Eksperiment je pokazao da se lekovi najbolje vezuju za PA, kao i da azitromicin ima najveći afinitet vezivanja
Ispitivanje uticaja pH i granulacije na početnu brzinu rastvaranja fosfatnog stakla/ Investigation of the influence of pH and granulation on the initial dissolution rate of phosphate glass
No full textFosfatna stakla imaju jedinstveno svojstvo da se mogu potpuno rastvoriti u vodenim rastvorima, a brzina rastvaranja može da se kontroliše. Proces rastvaranja stakla počinje razmenom katjona sa površine stakla sa protonima iz rastvora (H+ ili H3O+) i hidratacijom staklene mreže. Početna brzina rastvaranja je osnovna karakteristika rastvaranja stakla. Analiza početnih brzina rastvaranja fosfatnog stakla, koje je dobijeno topljenjem, pokazuje da su brzine značajno veće u kiseloj sredini u odnosu na brzine rastvaranja u neutralnoj. Granulacija uzorka ima veći uticaj na početne brzine u neutralnoj sredini. Granulacija uzorka ne utiče na vrednost energije aktivacija početnih brzina rastvaranja u obe sredine. U neutralnoj sredini temperatura manje utiče na hidrolizu, a više na difuziju katjona, dok je u kiseloj sredini suprotno
Stress state optimisation of vertical atmospheric large-volume tanks
No full textThe strength calculation is very important in the design of the tank. Significant efforts have been made to solve this task and have led to standardized procedures, recommendations and standards for tank design. Within the existing standards, the designers are able to define mainly the geometry of the tank and technical conditions of the structure. When it is necessary to check the stability of the shell or the complete tank, they resort to analytical methods with the use of classical patterns from general theory of shells. As is well known, the application of general shell theory, even in the simplest of cases, leads to very complex calculations. When using membrane theory in the calculation, it is shown that satisfactory results are obtained only for parts of the shell far enough from ends, but it cannot satisfy all the conditions on the contour and the area of supports.U projektovanju rezervoara proračun čvrstoće je veoma značajan. Značajniji napori uloženi u cilju rešavanja ovog zadatka doveli su do standardizovanih postupaka i do pre-poruka i standarda u oblasti projektovanja rezervoara. U okvirima postojećih standarda projektanti su u mogućnosti da definišu uglavnom geometriju rezervoara i tehničke uslo-ve izrade. Kada je potrebno proveriti stabilnost omotača ili kompletnog rezervoara, pribegavali su analitičkim metoda-ma uz korišćenje klasičnih obrazaca iz opšte teorije ljuski. Kako je poznato, primena opšte teorije ljuski, čak i u naj-jednostavnijim slučajevima, dovodi do vrlo složenih računa. Primena membranske teorije u proračunu pokazuje da se dobijaju zadovoljavajući rezultati samo za delove ljuske dovoljno udaljene od krajeva, ali ona ne može zadovoljiti sve uslove na konturi i u području oslonaca
Analysis of changes of mechanically activated sodium carbonate sample
No full textFor mechanical activation of sodium carbonate, a vibro mill at a frequency of 3000 oscillations per
minute was used for 28 minutes. After activation, samples were placed for 31 days in the air at room
conditions. In aim to monitor the kinetics of the transformation process of sodium carbonate to
bicarbonate, Fourier-transform infrared (FTIR) spectroscopy analysis was used. As a function of
relaxation time characteristic groups were observed: CO3
2-, HCO3
- and OH-. The obtained results
provided kinetics parameters for the transformation of carbonate into bicarbonate as a result of
chemisorption of moisture and carbon dioxide from the atmosphere
Antibacterial activity of amine-functionalized silver-enriched beta zeolite
No full textZeolites are inorganic, crystalline aluminosilicates that nowadays has been used as
adsorbents, catalysts and carriers of catalytically activated substances, due to the small size
of their pores, large internal surface, and well-defined chemical composition. In this paper,
the modification of beta zeolite using (3-aminopropyl)-triethoxysilane (APTES) was
investigated. The results of the Fourier transform infrared spectroscopy and
thermogravimetric analysis confirmed the presence of amino groups derived from APTES
onto the modified zeolite surface. APTES-enriched zeolite was further used as an adsorbent
of silver ions from aqueous solutions. The obtained results reveal that a zeolite after
modification exhibited significantly better adsorption efficiency (97%) in comparison to the
unmodified (37%). The kinetic data follows the pseudo-second-order model which
indicates a chemical interaction between silver ions and functional amino groups on the
surface of the silanizedbeta zeolite. Ag-APTES enriched beta zeolite also was studied as
anantibacterial agent toward the pathogenic bacteria Gram-negative Escherichia coliDSM
498 and Gram-positive Staphylococcus aureus ATCC 25923
Removal efficiency of pb(II), Zn(II) and Cu(II) in mono- and multimetal systems by alkali treated apricot shells biosorbent
No full textThe mutual interaction of metal ions (lead, zinc and copper) on removal efficiency in binary and ternary systems, by biosorbent based on alkali treated apricot shells (Prunus armeniaca L.) was examined. The evaluation was done in batch system at two metals concentrations: 0.2 and 0.5mmol/ dm3. Tested biosorbent exhibited preferential uptake of lead in a multimetal systems. It is evident that mutual inhibition exists in all multimetal systems, but systems containing lead ex-hibited extreme inhibition toward copper and zinc ions. Process of sorption depends not only on specific chemistry of each metal, their affinity toward binding sites and the type of metal binding onto biosorbent, but also on sorbent chemical and morphological characteristics. In multimetal systems, tested sorbent showed preferential sorption orders: Pb (II)>Cu (II)>Zn (II)
Approach on recycling of printed circuit boards (PCB) via hydrometallurgical procedures: Principle and methodology
No full textRecent mankind demand for electronic devices is in constant upgrowth, those devices
always contain printed circuit boards (PCB) which are mainly constructed of plastics, semiconductors
and decent content of various metals. Hence, in the end-of-life of those
products, it is highly recommended to recover those materials or functionalize those waste
into other products or feed materials, in order to lessen their harmful impact on the
environment. One of the promising processing procedures is hydrometallurgical treatment,
since it is cost-effective and simple. In order to recover metals as aqueous soluble salts,
crushed and milled PCB is air-pyrolyzed and obtained powder is processed as start material
in leaching experiments. The use of concentrated aqua regia led to the passivation of solid
material and consequently impede the leaching process. Dry-digestion leaching using
concentrated sulfuric acid partially leached some metals. The highest leaching rate (≥70 %)
has been achieved using diluted sulfuric acid (for Al, Ni, Fe, Co, and rare-earth) and copper
yield was highest utilizing 2 M H2SO4 + 3 M H2O2; S/L = 0.1 g/ml. While sulfuric acid has
accomplished some results for enumerated leachates, it achieved limited success for
leaching Ba, Pb, Ag, Au, Pt and Pd. Overall findings imply that hydrometallurgical
procedures may be used but only together with previous separation techniques. That
approach would increase overall leaching with oxidizing agents and enable leaching of
noble metals
Utilization of construction material and unsaturated resin from waste PET as a stabilizer for desorbed metal ion Pb2+
No full textWastewater management covers various techniques developed to provide purified water that would
do minimum harm to the environment. Applying adsorption leaves a saturated adsorbent that should
be regenerated or stabilized so it can’t release pollutants into the environment. Lead, one of the most
toxic pollutants, can be efficiently removed utilizing the adsorption process. After the consecutive
adsorption and desorption processes, the lead must be processed to significantly reduce and prevent
the risk to human health and environmental pollution. As one of the most efficient technologies for
treating this toxic pollutant, stabilization has been tested by converting a desorbed lead to its salt leadphthalate
(LP). Obtained LP is used as a component in the production of construction materials and
composites with unsaturated polyester resins (UPR). A standard leaching test (Toxicity Characteristic
Leaching Procedure - TCLP) was performed to determine the toxicity of the waste material used as
an additive. The concentration of leached lead from the construction material with the addition of
Ca(OH)2 can be as high as 54 mg/L, which significantly exceeds the permitted limits. After adding
cement, lead concentration is lower - 13 mg/L. The acquired results from the sample with UPR show
that the concentration of released lead is as low as 0.01 mg/L. Such results indicate complete
crosslinking of the UPR and strong binding of the lead ions. Applying the S/S technique together with
the utilization of UPR would be an environmentally friendly operation and easily applicable
procedure for stabilizing Pb2+