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Novel Mg-doped pyro-hydrochars as methylene blue adsorbents: Adsorption behavior and mechanism
No full textIn this study, Mg-based pyro-hydrochars derived from waste grape pomace (Mg-GP), corn cob (Mg-CC), and Miscanthus x giganteus (Mg-MIS) were successfully prepared applying one-step hydrothermal carbonization followed by pyrolysis. The structural characteristics and surface analysis of the prepared materials were characterized by various techniques, while its adsorption ability was examined through remediation of methylene blue (MB) under batch adsorption experiments. The obtained results revealed that pyro-hydrochars are highly effective adsorbents of MB with achieved capacities of 289.65 mg g(-1), 262.30 mg g(-1), and 232.48 mg g(-1) for Mg-GP, Mg-CC and Mg-MIS, respectively. The binding of MB to the surface on either of the tested material was achieved by a complex mechanism that unifies electro-static interaction, hydrogen bonding, pi-pi interaction, surface complexation, and ion-exchange mechanism. The kinetic study display that the adsorption process onto used Mg-doped pyro-hydrochars is favorable and follows pseudo-second order kinetics, while the isotherm equilibriums were determined by Sips isotherm model. Tested materials can be effectively reused for at least 3 cycles, with minimal loss of efficiency. Overall, findings from this work promote Mg-doped pyro-hydrochars form different precursors as promising, sustainable, and efficient adsorbents of MB from polluted wastewaters
Electrophoretically deposited gentamicin-loaded composite coating
No full textUvođenje antibiotika u polimer/mineralnu kompozitnu prevlaku poboljšava antibakterijska svojstva prevlaka. Kompozitna prevlaka (hidroksiapatit - HAP, poli(vinilalkohol), hitozan, gentamicin) dobijena je elektroforetskim taloženjem iz četvorokomponentne vodene suspenzije. Primenom termogravimetrijske i rendgenske difrakcione analize pokazano je prisustvo karbonatno-supstituisanog HAP. Antibakterijska aktivnost kompozitne prevlake sa gentamicinom potvrđena je protiv soja S. aureus i E. coli, čineći ovu prevlaku pogodnom za potencijalnu primenu u biomedicini.Antibiotic introduction in polymer/mineral coating can improve the antibacterial properties of coatings. Composite coating (hydroxyapatite, poly(vinyl alcohol), chitosan, gentamicin) was fabricated from a four-component aqueous suspension using electrophoretic deposition. Structural and morphological characterization of the coating was investigated by X-ray diffraction and thermogravimetric analysis proving carbonate-substituted HAP. The presence of gentamicin contributed to the antibacterial activity of composite coating against S. aureus and E. coli strains, representing a suitable material for possible application in biomedicine
Influence of mould preheating on solidification stress of railway aluminothermic welding by casting simulation aluminothermic welding by casting simulation
No full textAluminothermic welding has been used to connect railway rails for over a century. This method has several advantages, including its versatility, the tightness of the weld it creates, and its ease of execution. To complete the procedure, no further power source is necessary. The design of the mold with the pouring system, which should ensure even pouring of thermal steel without turbulence, then even heat dissipation or cooling to obtain an appropriat micro and acro structure of steel free of internal and external defects, is one of several factors that contribute to a quality welded joint. As a result, costly experimental techniques in industrial settings were necessary to keep up with the ever-changing mould design. The model design was upgraded in comparison to the previous version [1], and will be imroved even further.The two sets of solid steel rails put on either side of the casting mould will be adjusted as heating media within the mould material category in the future, bringing the model closer to reality. As a result, cooling and heating temperatures will be more evenly distributed. Stress and strain modeling were performed to the preheated model to provide a more complete understanding of how shrinkage is related to stress. In future iterations of the model, we will either move the heat source to its right place approximately 40 cm above ground or adjust the temperature, diameter, and gas at the current site to more exactly reproduce real-life circumstances. Furthermore, during simulation setup, the
replace material function may be used to model a new component that represents the divider that will be changed between air and silica sand material at the end of
prehearing. Software programs are being used to simulate conventional casting procedures that may be used in the casting of thermite steel during the fabrication
of welded railway connections in order to prevent costly and time-consuming
industrial experimentation. The NovaFlow & Solid CV software suite [2] was used
to simulate casting thermite steel in the mold cavity or weld joint for the 49E1 rail
Understanding the Role of Ruderal Plant Species in Restoration of Degraded Lands
No full textRuderal plants are dynamic functional group characterized by their resistance to changing conditions of areas under anthropogenic influence. Opportunistic character enables them wide and fast spreading on growing number of degraded sites, including polluted ones. Not only are ruderal plants able to easily colonize open, degraded areas of land, but they can also be observed as a biological signal that the degraded land is able to recover. Therefore, many ruderal plants are studied for their capacity to cope with various inorganic and organic contaminants in the environment and recognized for their potential in remediation of various degraded lands. Many annual, perennial and woody species are investigated on range of contaminated sites where they showed potential to be applied in phytoremediation technologies. Degraded habitats represent favorable areas for introduction and spreading of invasive species, and some ruderal species. Those ruderal species, owing traits such as high seed production rate, efficient vegetative spreading and rapid nutrient uptake, could rapidly spread in such areas out of their native range, becoming invasive. Common traits of ruderal plants are mostly matching the desirable traits of plant suitable for phytoremediation purposes. As research in the area of phytoremediation continues to develop toward increasing the remediation efficiency, ruderal plants are gradually being subjected to various experiments and applications aiming to improve element bioavailability, plant tolerance or accumulation capacity. Overall, ruderal plants show high potential for remediation of degraded lands, and their importance will grow over time with increasing rate of anthropogenic disturbances and climate changes
Study of the effects of active bromine species presence in electrolytic desulfurization of subbituminous coal
No full textThe removal of organic and inorganic sulfur from the Bogovina Basin subbituminous coal by
electrochemical redox reactions was performed. The effect of presence of active bromine species
on the desulfurization process was monitored. The desulfurization was performed in inorganic
acidic solutions that contained different bromide concentrations and in pure acid solution. To
determine the optimal conditions for the desulfurization process, polarization curves were
recorded in three different electrolytes: 0.1 M H2SO4, 0.1 M H2SO4 + 0.01 M KBr, and 0.1 M
H2SO4 + 0.1 M KBr using graphite and dimensionally stable anode (DSA) electrodes as the
anode, while in all cases stainless steel S31603 electrode was used as cathode. By analyzing the
results obtained from the polarization curves, 0.1 M H2SO4 and 0.1 M H2SO4 + 0.1 M KBr were
chosen as the most suitable electrolytes. Also, it was found that the DSA anode showed better
results in terms of energy efficiency of the process compared to the graphite anode and therefore
it was selected for the coal desulfurization process. It is considered that finely suspended coal
particles in an electrolyte can behave according to bipolar electrochemistry. Coal was treated
for 4 hours in two selected electrolytes. The suspension was sampled at different times up to 240
min from the beginning of the process. Sulfur content in coal was determined by elemental
analysis. The results showed that the sulfur content decreases faster in the case of the electrolyte
containing KBr, i.e. that the desulfurization effect is significantly better than in the case of the
system containing only H2SO4. It can be concluded that active bromine species accelerate the
desulfurization process and thus improve energy efficiency
Morphology investigation of sulfur-polymer composite
No full textThis research evaluates the effects of the acid environment on sulfur-polymer composite. For this purpose, a morphology investigation consisting of mathematical morphology analysis and SEM analysis was performed. Based on the obtained results, insignificant changes in the pore system of sulfur-polymer composite in terms of deterioration, pore distribution, and homogeneity were observed. Namely, no signs of severe damage were detected at the surface and inside the samples. With increasing the acid exposure time, the material exhibited further changes in the direction of homogenization and drowning of the aggregate in the sulfur binder compared with the starting structure. These facts indicate that sulfur-polymer composite can be effectively used as a construction material in an acid environment
Bentonite modified with cationic surfactant as promissing adsorbent for carbamazepine
No full textNumerous chemical compounds present in natural waters and wastewater are resistant to
conventional water treatments and persist in treated effluents. Among these substances,
pharmaceuticals, due to their widespread use, raise special concern due to their potentially
harmful effects on human health especially when they reach drinking water. One of the most
efficient technique for removal of pharmaceuticals from polluted water is their adsorption on
various adsorbents, such as activated carbons, clays (kaolin, bentonite, etc.) and zeolites. In
this study, the potential of modified bentonite for removal of carbamazepine, a
pharmaceutical with anticonvulsant and mood-stabilizing properties, was investigated. The
natural bentonite from Šipovo deposit, Bosnia and Herzegovina, was modified with the
cationic surfactant Arquad®2HT-75 in amounts equivalent to 50% and 100% of the
bentonite's cationic exchange capacity. Characterization of prepared samples by Fouriertransform
infrared spectroscopy and Simultaneous Thermal Analysis, confirmed presence of
surfactant in modified bentonites. Results on carbamazepine removal by modified bentonites
showed that its adsorption increased with increasing of the amount of surfactant as well as
with increasing of the initial pharmaceutical concentration. The highest adsorption of
carbamazepine was achieved with bentonite containing the highest amount of surfactant.
Since the natural bentonite has no affinity to remove carbamazepine, these findings suggest
that modified bentonite is a promising adsorbent for its removal from contaminated water
The Bridgman method of (BiAs)2(TeSe)3 bulk single crystal growth by spontaneous nucleation
No full textThe Bi0.5As1.5Te2.98Se0.02 single crystal in 11 mm × 80 mm size was grown using the Bridgman method. Energy dispersive spectrometry (EDS) analysis was used to determine the chemical composition of the studied samples, as well as for checking and confirming the homogeneity of the samples. Mobility, concentration of charge majority carriers and Hall coefficient of single crystal, were determined using a Hall Effect system based on the Van der Pauw method. Hall Effect was measured at room temperature with four ohmic contacts and at temperature of liquid nitrogen with silver contacts with an applied magnetic field strength of 0.37 T at different current intensities. The expected improvement in the mobility of obtained single crystal doped with this content of arsenic was not obtained
Microplastics in urban soils of Belgrade: Abundance and potential sources
No full textMicroplastics (MPs), the long-lasting anthropogenic contaminant omnipresent in the environment, have become a threat to ecosystems’ function and living organisms’ health, potentially harming the food chain globally. The presence of MPs emerged on a worldwide scale, while the evidence of microplastic particles is already being detected in human tissues. Terrestrial environments are sinks for plastic deposition and are one of the main routes of MPs reaching the groundwater and water bodies. In this regard, urban soils could significantly contribute to overall plastic pollution even though it have been mostly neglected by the research investigations carried out so far. Herein, we investigated MPs abundance in the soils of Belgrade, a city located in the northeast of Serbia, the capital and the most populated city in Serbia. Two sampling points chosen to represent the pollution gradient were the city center zone, close to the highway (BG1), and Košutnjak, the urban forest area around 7 km distant from the center (BG2). MPs extraction was performed using a density separation method, by saturated NaCl solution (1.2 g cm-3). Before extraction, soil organic matter was digested by 30% H2O2. Found average concentration of MPs was 400 items per kg of dry soil sampled in BG1. Soil from Košutnjak contained no MPs according to our findings. MPs abundance found in sampled soils from Belgrade is in agreement with previous reports analyzing urban areas. Isolated plastic particles were identified and counted using a polarizing microscope (Carl Zeiss Jena Pol-U). All found items were white/transparent fragments, characterized afterward by ATR-FTIR spectroscopy using a Thermo Scientific Nicolet iS50 spectrophotometer. Detected polymer types were polystyrene (PS) and phosphorylated cardanol prepolymer (PCP), suggesting the insulation, packing, and rubber materials as potential pollution sources. Transportation, overload of customer goods and packaging, construction, and building activities are the prevailing anthropogenic origins of MPs accumulation in urban environments. Further investigations will aim to reveal the relations between MPs and other pollutants and the potential impact on soil biota
Stability of solid residue after integral treatment of acid mine drainage
No full textAcid mine drainage is a challenging environmental problem caused by mining activities. Long-term copper ore exploitation and vast amounts of mining waste lead to severe soil contamination as well as river and groundwater pollution. In this paper, research is focused on utilizing waste mine waters and off-balance parts of the mine deposit (such as flotation tailings) and converting their negative characteristics to an environmentally friendly one. In the authors’ previous work, acid mine water from Robule, which is part of the Bor copper mining and smelting complex in Serbia, was successfully treated using flotation tailings, and the resulting solution was suitable for safe discharge. This paper investigates the characteristics of the solid residue that remained after the treatment of the modified flotation tailings in order to evaluate the possibility of its safe disposal back into the environment. The solid residue was subjected to TCLP and EN 12457-4 tests as standard procedures that assess the leaching characteristics of a material. The solid residue was also exposed to long-term leaching with melted snow to simulate environmental conditions for one year. This drainage water was analyzed and compared with the results of the standard leaching procedures. The investigated treatments lead to improved economic and environmental effects, while the process itself is adjusted to preserve the environment