Since recycled technologies usage is mandatory for environmental safety, and in this regard, it is important to examine new materials that can be used in construction and are primarily produced from ...fly ash. In addition to characteristics such as hardness and compressive strength, the given materials must also be radiologically and environmentally safe. The main concept of engineered geopolymer gel composites based on fly ash residues is focused on developing binder materials via gel formation processes that can replace ordinary cement materials. This study is unique in researching the potential use of fly ash from the Nikola Tesla thermal power plant in Serbia, where the hybrid geopolymeric materials synthesized from fly ash are experimentally examined with the addition 1 wt% and 2 wt% of polyvinyl alcohol (PVA). This paper aims to investigate the structural, morphological, mechanical, and radiological properties of hybrid materials with the addition of PVA and without additive in the period of ageing for 28 days at room temperature. The phase composition was investigated using X-ray powder diffraction (XRPD) analysis, while morphological characteristics of these materials were examined using scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDS). Vibrational spectra of obtained samples are investigated using diffuse reflectance infrared Fourier transform (DRIFT) and Fourier transform infrared (FTIR) techniques. The hardness and compressive strength are also examined, indicating that the 1 wt% addition in geopolymeric matrix results in the best mechanical properties. Radiological measurements of investigated all geopolymer samples show decreasing activity concentrations of radionuclides for 50% compared to fly ash.
The aim of the study was to investigate the influence of low heating
temperatures with two different retention times to optimize the process for
obtaining nanosized hydroxyapatite material that can ...possibly be used in the
fields of biology and pharmacy. Nanosized hydroxyapatite was successfully
obtained by wet chemical precipitation. The annealing of the material
performed at 300 oC with two different retention times i.e. 3 and 6 hours in
air atmosphere. Low annealing temperature with extended retention time was
selected in terms to reduce energy consumption. FTIR spectroscopy was used
to confirm characteristic vibrational bands of hydroxyapatite samples, and
presence of carbonate bands of hydroxyapatite annealed for 3h and 6h. X-Ray
powder diffraction analysis were used to examine phase composition,
determine the size of unit cells and crystallite sizes, and SEM-EDS methods
were used to obtain particle size and arrangement also grain growth
morphology and confirmed the presence of calcium, phosphorous oxygen and
carbonate peaks. The results show that different retention time has
influence on particle growth as well as unit cell parameters and crystallite
sizes changes of hydroxyapatite material
Development in many areas of engineering and technology are closely linked to the development of new or improvement of existing materials. Having in mind wide use of bacterial nanocellulose (BNC) in ...various areas of everyday life, from biomedicine, ecology to electronics, BNC-based composites are becoming widely used and attracting the attention of the scientific community. It is especially important to examine in detail the synthesis parameters that affect the changes in the crystal structure and morphology of the obtained composites, having in mind that these changes have a crucial influence on their final functional properties. In this paper, a composite material based on bacterial nanocellulose BNC (as the matrix) and ferromagnetic Fe3O4 was studied. BNC was obtained by the activity of acetic fermentation bacteria after 7 days of growth in a suitable medium. The research is aimed to optimization of the Fe3O4 precipitation conditions. It's especially considering the time interval of BNC films spend in the iron salt solution. The influence of the performed synthesis conditions was considered by the SEMEDS, FTIR and XRD methods.
In this paper, the properties of organic-inorganic hybrid polymer materials, which were synthesized from an aluminosilicate inorganic matrix with the addition of brushite and aminosilane grafted on ...one side and PEI covalently bonded composites on the other side, were examined. The synthesized organic-inorganic hybrid polymers were examined in terms of a structural, morphological, thermo-gravimetric, and adsorption-desorption analysis and also as potential CO
capturers. The structural and phase properties as well as the percentage contents of the crystalline and amorphous phase were determined by the X-ray diffraction method. The higher content of the amorphous phase in the structure of hybrid polymers was proven in metakaolin and metakaolin-brushite hybrid samples with the addition of amino silane and with 1,000,000 PEI in a structure. The DRIFT method showed the main band changes with the addition of an organic phase and inorganic matrix. Microstructural studies with the EDS analysis showed a uniform distribution of organic and inorganic phases in the hybrid geopolymers. The thermo-gravimetric analysis showed that organic compounds are successfully bonded to inorganic polymer matrix, while adsorption-desorption analysis confirmed that the organic phase completely covered the surface of the inorganic matrix. The CO
adsorption experiments showed that the amine-modified composites have the higher capture capacity, which is 0.685 mmol·g
for the GM10 sample and 0.581 mmol·g
for the BGM10 sample, with 1,000,000 PEI in the structure.
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Newly designed mesoporous brushite-metakaolin-based geopolymer materials were examined with an idea for using this material as a potential adsorbent for Pb(II) removal from aqueous solutions. As a ...starting component for geopolymer synthesis, a natural raw kaolinite clay with the addition of 2 wt.%, 4 wt.%, 6 wt.%, 8 wt.%, and 10 wt.% of pure brushite was used. Phase, structural, morphological, and adsorption properties of newly synthesized mesoporous brushite-metakaolin geopolymer materials were examined in detail by the means of XRPD, FTIR, SEM-EDS, BET/BJH, and ICP-OES methods. The ICP-OES results showed that the synthesized material samples with 2 wt.%, 4 wt.%, and 6 wt.% of brushite possess significant adsorption properties and the mechanisms of the adsorption process can be attributed to chemisorption. The most notable result is that brushite-metakaolin-geopolymer with 2 wt.% of brushite have the best efficiency removal, more than 85% of Pb(II).
The phenomenon of the resource curse is based on the assumption that countries with large natural resources are unable to achieve adequate economic development, and cannot provide benefits to their ...citizens. High impact on this issue lays in inadequate management of human resources and corruption. The main objective of this paper is to examine the basic assumptions of the theory of resource curse, to determine the factors that have the greatest impact on its (non)existence, to determine the causal dependence between natural wealth and the political environment, as well as with the quality of life of citizens. The research was carried out by analysing five variables that define resources curse and Human Development Index. For data processing, Fisher's F test is applied. The survey was done on a sample of 22 countries. The results show: a) the characteristics of the political regime do not have a clearly defined impact on existence of resource curse, b) resources rent and export of energy products do not have a significant impact on the quality of life of citizens (expressed through the Human Development Index) and c) a significant degree of deviation from the expected is determined in countries rich in ores and metals.
Due to the growing number of people infected with the new coronavirus globally, which weakens immunity, there has been an increase in bacterial infections. Hence, knowledge about simple and low-cost ...synthesis methods of materials with good structural and antimicrobial properties is of great importance. A material obtained through the combination of a nanoscale hydroxyapatite material (with good biocompatibility) and titanium dioxide (with good degradation properties of organic molecules) can absorb and decompose bacteria. In this investigation, three different synthesis routes used to prepare hydroxyapatite/titanium dioxide nanomaterials are examined. The morphology and semiquantitative chemical composition are characterized by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). The obtained materials' phase and structural characterization are determined using the X-ray powder diffraction method (XRD). The crystallite sizes of the obtained materials are in the range of 8 nm to 15 nm. Based on XRD peak positions, the hexagonal hydroxyapatite phases are formed in all samples along with TiO
anatase and rutile phases. According to SEM and TEM analyses, the morphology of the prepared samples differs depending on the synthesis route. The EDX analysis confirmed the presence of Ti, Ca, P, and O in the obtained materials. The IR spectroscopy verified the vibration bands characteristic for HAp and titanium. The investigated materials show excellent antimicrobial and photocatalytic properties.
Octacalcium phosphate (OCP) is a material from the calcium phosphate group with a crystal structure similar to hydroxyapatite. The removal process of lead and cadmium in aqueous solution using ...octacalcium phosphate material was investigated. OCP material was synthesized by the solution precipitation method. The structural and phase properties of OCP before and after the removal process were determined by the X-ray diffraction (XRD) method. Microstructural and semi-quantitative analysis of the material was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS). Characteristic bands and functional group determination were revealed using the Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR). As target pollutants, Cd(II) and Pb(II) were chosen in adsorption experiments. Results show that OCP in the first 10 min has a very fast removal rate for Pb(II); the equilibrium state was reached after 10 min with more than 98 % adsorption efficiency. Results for Cd(II), results showed the same removal rate but somewhat lower adsorption efficiency, amounted to approximately 63 %.
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Goal of this work is to establish technical feasibility and fundamentals of producing activated carbon from plane tree seeds biomass for porous materials derivation. Bio-chars produced via ...carbonization from plane tree seeds precursor were activated in CO2 at 750 and 850?C, during various residence times. Their surface area and porosity were characterized by N2 adsorption at 77 K. Surface areas of activated carbons can be correlated with kinetics mechanism and activation energy magnitudes of oxidation reaction by CO2, which are closely related to applied activation temperature. Result showed that high temperature activated carbon had higher gas adsorption as compared to activated carbon obtained from lower temperature during two-hour residence time. Breakthrough behavior was detected at 850?C where surface reactions dominate, and it is characterized by autocatalytic kinetic model under designed conditions. Both, temperature and CO2 concentration in vicinity of solid surface effect on breakthrough time of adsorbent. Derived bio-chars are converted into high quality activated carbons, with surface area of 776.55 m2/g, where micro-pores with pore diameters less than 2 nm prevail. Produced activated carbons have properties comparable with commercially available activated carbons, which can be successfully used for removal of harmful gaseous pollutants toward air purification.
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