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Coupled substitutions of fluorapatite crystals in the engineering of optically-active bionanomaterials
No full textA wide range of new biomaterials for medical use has been prepared using various coupled ionic substitutions in a fluorapatite (FAp) crystal matrix [1-4]. FAp is present in human enamel, so its synthetic form is often used in the treatment of dental caries or osteoporosis [5]. In recent years, FAP nano-sized particles doped with rare-earth ions have been extensively studied as potential luminescent material for cell labeling, bone imaging in bone tissue engineering, and for cancer therapies [1-4]. Moreover, FAp is a suitable crystal matrix for various substituents that can alter its physicochemical, luminescent, and biological properties [5].
Uniform nanopowders of pure fluorapatite (FAp) and praseodymium-nitrate-carbonate substituted fluorapatite (PrNCFAp) have been successfully synthesized by precipitation reaction, and systematically characterized by XRD, FTIR, SEM, TG and PL methods. Coupled substitution of FAp reduces the crystallite size, and FTIR spectra indicate the presence of nitrate (NO3-) and carbonat (CO32-) species. Structure thermally analysis confirm decomposition of water, NO3- and CO32- species in the range of 100-750 oC. Emission of FAp nanopowder occurred in the violet-blue region of visible part of the spectrum, with redshift to the green color region when Pr3+, NO3- and CO32- substituted in the lattice. Analysis of luminescence spectra by MCR-ALS method extract three fluorophores from the samples and showed simultaneous existents of emission-reabsorption between dopants in FAp lattice.
The obtained samples showed a small degree of hemolysis and antibacterial activity and could potentially be candidates for further research in dentistr
Characterization of pellet samples obtained by peletization of limestone and seaweed
No full textThis paper presents the results of physico-chemical characterization of both the initial samples of lithotamnian
limestone and seaweed (Ascophyllum Nodosum), and the products of aggregation of their mixtures in different
ratios by the pelletization process. The initial samples were waste limestone from filter plants and dried seaweed.
The final product of the pelletization process should serve the needs of agriculture as a means of biostimulation
and can also be used in raising the pH levels of acidic soils. Several different pellet formulations were obtained by
the process of discontinuous pelletization, and also by using a simulation of the continuous pelletization process on
a pelletization plate. Tests of the mechanical properties of the pellets showed that the best results are shown by the
pellets of the 4K sample, which were obtained by a continuous pelletization process with a mutual ratio of seaweed
and limestone of 70:30%
Aktivacija čvrstih disperznih materijala
No full textU toku mehanohemijske aktivacije na materijalu dolazi do promena koje mogu da dovedu do
različitih fenomena. U ovom istraživanju mehanohemijski je aktiviran natrijum karbonat tokom 2,
7, 14 i 28 minuta. Aktivacija je vršena u vibro mlinu pri frekfenciji od 3000 oscilacija u minuti
(mleveno je po 50g Na2CO3 anhidrovanog). Nakon mehanohemijske aktivacije uzorci su izloženi
sobnim uslovima u prisustvu vlage i ugljen dioksida, u trajanju od 31 dana. U tom periodu (period
relaksacijie) praćene su transformacije koje su se dešavale na aktiviranim uzorcima. U cilju
praćenja kvalitativnih promena na aktiviranim uzorcija korišćena je infracrvena spektralna analiza.
Natrijum karbonat je dobar apsorbent ugljen dioksida, i istovremeno je material koji dobro
odgovara na uticaj mehaničke energije. Praćen je mehanizam nastajanja natrijum bikarbonata iz
mehanohemijski aktiviranog natrijum. Ispitivanja FTIR metodom su izvršena u funkciji od vremena
aktivacije, i vremena relaksacije. Praćene su karakteristične CO3
2-, HCO3
- i OH- grupe
Novi postupak sinteze amino i epoksi derivata taninske kiseline i lignina za proizvodnju epoksidnih smola na bioobnovljivoj osnovi
No full textRemoval of Pb(II), Cu(II), and Cd(II) from Aqueous Solution by Alginate-Immobilized Aquatic Weed M. spicatum
No full textBiosorption is evolving as a potential alternative to the
existing conventional technologies for the removal and/
or recovery of pollutants from aqueous solutions. The
present work investigates the possible application of
waste biomass Myriophyllum spicatum (Ms) in removing
contaminants, evaluating equilibrium through isotherms
of selected heavy metals: lead, copper, and
cadmium. As a heavy metal biosorbent, Ms was immobilized
in alginate beads (Ms: Alginate 2:1). Applied
biosorbent, MsA, was characterized by scanning electron
microscopy with energy dispersive X-ray spectroscopy
(SEM–EDX) and Fourier transform infrared spectroscopy
(FT-IR). Experimental results were fitted (nonlinear)
by six isotherm models: Langmuir, Freundlich,
Sips, Redlich and Peterson, Toth, and Temkin. For
lead(II) ion removal, fitting follows the following
sequence, F ≈ R-P > S > To > L > Te, while for copper(II)
and cadmium(II) ions are as follows: R-P > To ≈ Te ≈
L > S > F and R-P > L > To > S > F > Te, respectively. TOC
analyses revealed that M. spicatum releases 35.04 mg/L
of total organic content while immobilized sample, MsA,
only 6.81 mg/L. Finally, this biosorbent was tested on a sample of real wastewater from a coal-fired thermal
power plant complex TPP Kostolac (operated by PE
“Electric Power Industry of Serbia”). The results indicate
that using immobilized aquatic weed M. spicatum as
a biosorbent has a high potential for heavy metal wastewater
treatment applications
Upgrading fuel potentials of waste biomass via hydrothermal carbonization
No full textIn recent decades, massive exploitation of fossil fuels caused a growing demand for the production of energies from renewable sources. Hydrochar obtained from waste biomass via hydrothermal carbonization (HTC) possesses good potentials as a biofuel. Therefore, we performed HTC of corn cob, paulownia leaves, and olive pomace at different temperatures (180, 220, and 260 degrees C). The main goal of this study was to comparatively evaluate the influence of HTC conditions on the structure and fuel characteristics of the obtained solids. The results showed that the yields of hydrochar decrease significantly with increasing temperature in all samples. The carbon content and higher heating value increased and reached the highest values in hydrochars obtained at 260 degrees C, while the content of volatile matter decreased. Furthermore, the Van Krevelen diagram reveals that the transformation of feedstock to lignite-like products upon HTC was achieved. In this study, the results showed that processes of dehydration and decarboxylation during HTC provoke intensive biomass transformation and that hydrochars obtained at higher temperatures have significantly enhanced fuel properties and fewer volatiles compared to the feedstock
The methods of safe storage of spent nuclear fuel and waste
No full textThe current problem is the issue of safe storage of nuclear waste, especially materials generated as waste in nuclear power plants. In the nuclear fuel cycle, in the fuel, a large amount of artificial radionuclides are created (most of them are much more active than uranium), so radioactivity in the normal reactor operation is about a billion times greater than before entering the reactor (1021 Bq observed for 100 tons). Radionuclides are the most important part of the nuclear waste and their safe storage and removal from the natural environment is very important. For now, utilized nuclear fuel (high radio-co-active waste which remains after its transformation) is temporarily stored in special storages in order to exploit a rapid decline initial period of its radioactivity and thus simplify further operation with it. In this paper the literature data of different methods of disposal of nuclear waste are presented
Brassica Species in Phytoextractions: Real Potentials and Challenges
No full textThe genus Brassica is recognized for including species with phytoaccumulation potential and a large amount of research has been carried out in this area under a variety of conditions, from laboratory experiments to field trials, with spiked or naturally contaminated soils, using one- or multi-element contaminated soil, generating various and sometimes contradictory results with limited practical applications. To date, the actual field potential of Brassica species and the feasibility of a complete phytoextraction process have not been fully evaluated. Therefore, the aim of this study was to summarize the results of the experiments that have been performed with a view to analyzing real potentials and limitations. The reduced biomass and low metal mobility in the soil have been addressed by the development of chemically or biologically assisted phytoremediation technologies, the use of soil amendments, and the application of crop management strategies. Certain issues, such as the fate of harvested biomass or the performance of species in multi-metal-contaminated soils, remain to be solved by future research. Potential improvements to current experimental settings include testing species grown to full maturity, using a greater amount of soil in experiments, conducting more trials under real field conditions, developing improved crop management systems, and optimizing solutions for harvested biomass disposal
X-ray diffraction and SEM analysis of waste sulfur modification for use in concretes
No full textSecondary sulfur obtained as a by-product in the oil refining process is a major problem as an environmental pollutant. One of the possibilities of environmental protection is the use of sulfur obtained in this way as a component of sulfur concrete. Mixing of sulfur with suitable additives can provide longer working lifetime of sulfur concrete, as well as maintenance of the former physical, chemical, and mechanical properties of concrete. Such mixtures are usually called modified sulfur or sulfur cement. Secondary sulfur produced in the oil refining process by the Klaus process (approval of crude oil) cannot be used in this form. In order to be ready for the use of sulfur concrete and asphalt, it is necessary to modify elemental sulfur from cyclic to chain form, obtaining of modified sulfur whose application is as a binding agent in a concrete instead of portland cement is described in this paper. Influence of dicyclopentadien, an organic additive, on sulfur modification has been studied in this research. Microstructure and mineral analysis of modified and unmodified sulfur cement binding are performed using polarized and scanning electron microscopes and X-ray diffraction spectrometer
Removal of Chromium(VI) and Arsenic(V) from Water Solution Using Modified Lignin Microspheres
No full textWith the development of the industry and growth of
the population, there is an increasing amount of waste,
which, due to inadequate treatment, pollutes water. The
group of the most dangerous pollutants present in water
includes heavy metals, such as As, Cd, Pb, Ni, Hg, Cr,
etc. [1]. Heavy metal ions are highly toxic and not biodegradable,
but are prone to accumulation in the body in
certain tissues and organs [2].
In recent years, natural materials, originating from
waste or renewable sources, have been increasingly
used as adsorbents in the removal of heavy metal ions
from water, due to their low cost, high prevalence and
beneficial impact on the environment [3]. Lignin, cellulose
and hemicellulose are the main polymers of wood
biomass [4]. Lignin is represented as a by-product in the
paper and pulp industry [5]. Chemical modification of
lignin was performed using acrylate derivatives (L-AC).
Modified lignin microspheres (LMS) were synthesized
by inverse suspension copolymerization using L-AC,
trimethylolpropane triacrylate (TMPTA) and methacryl
functionalized magnetite modified with MEMO silane
or with methacryloyl chloride (MACM1 or MACM2).
The procedure of inverse emulsion-suspension copolymerization
developed by Popović et al. [6] was used. In
a summary, disodium laureth sulfosuccinate (surfactant)
was stirred in water solution for 30 min at 80 °C. Afterwards,
TMPTA, L-MAC, MACM1 or MACM2 and the
initiator AIBN (1 wt. %) were added, followed by the
mixture of pore-forming solvents (tetradecanol and toluene),
stirred for 18 h at the same elevated temperature.
LMS microspheres were characterized by zero
charge point determination, FT-IR and SEM. The efficiency
of pollutants (chromium(VI) and arsenic(V)
ions) removal was analysed in terms of varying the
experimental conditions: the mass of adsorbent, the pH
of solution, the temperature of reaction and the contact
time. The best sorption was observed for the pH between
5.0 and 7.0. Synthesized bio-adsorbents showed
high efficiency, with capacities of 35.5 and 54.0 mg g-1
for the LMS adsorbents loaded with magnetite modified
using methacyl functionalized silane (LMS-1) or
methacryloyl chloride (LMS-2), respectively, obtained
according to Freundlich isothermal model. Adsorption
kinetics are described according to a pseudo-second
order model. Based on the obtained results, both adsorbents
showed excellent adsorption abilities.
Thermodynamic parameters, including the Gibbs
free energy (ΔGΘ), enthalpy (ΔHΘ) and entropy (ΔSΘ),
proved that adsorption is viable, spontaneous and endothermic
process (LMS-1) and exothermic process
(LMS-2) at temperatures between 25 and 45 °C