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Biochar as efficient tool for soil ammendement
No full textFood production generates significant amounts of waste, especially in fruits and vegetables
processing industries (FVPI), where biodegradable lignocellulosic waste (LCW) represents approx.
25-30% of processed raw materials. In most cases, this type of waste is landfilled, representing
unsustainable practices with significant environmental hazards. Biochar, a highly carbonaceous
organic material obtained from thermochemical conversion of LCW biomass, pose significant
positive characteristics with multifunctional purpose. Biochar application might remove emerging
contaminants from wastewater, and its application on soils improves soil properties such as fertility
leading to improved crop productivity, soil pH regulation and soil CEC improvement, as well as
microbial activities enhancement. In this paper, the characterization of biochar obtained via slow
pyrolysis of peach stone (PS) is done along with its possible application as a soil amendment. This
preliminary investigation revealed that the properties of the biochar produced from PS are in line with
those necessary to act as a suitable agent for soil amendment
Microplastic occurrence in urban and suburban soils of Bor, Eastern Serbia
No full textMicroplastics (MPs) are a newly acknowledged, pervasive pollutants found even in distant Earth
areas and represent a matter of global concern. This study inspects, for the first time, microplastic
content in terrestrial environments in the city of Bor, known as one of the most polluted industrial
cities in Serbia. Soils from the park in the II kilometer and the periphery of the Bor (Brezonik
settlement) were collected and analyzed. Plastic particle extraction from the soil matrix was
performed using the flotation method based on density separation. MP content differed significantly
between the two sites. Urban soil contained around 3800 items kg-1
, while suburban held 600 particles
per kilogram. The outstandingly high difference likely originates from the distinction in the
anthropogenic activity levels of the two localities. There was no notable difference in appearance. All
extracted items were white to transparent fragments. The morphological shape of plastic particles
indicated defragmentation as a governing origin source. Future investigations should be concentrated
on the MPs' correlation with other contaminants, namely heavy metals, and the eventual recognition
of MP`s role as the metal pollution vector in the investigated are
Simulation of the impact of preheating temperature on railway aluminothermic welding
No full textFor more than a century, railway rails have been joined using the aluminothermic welding process. The flexibility, compactness of the weld, and ease of execution are all advantages of this process. It is not necessary to use external energy to finish the operation. It is provided by the exothermic effect of the chemical reactions of the elements of the aluminothermic combination. 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 in order to obtain an appropriate micro and macro structure of steel, free of internal and external defects, is an important factor in producing a welded joint of the required quality. As a result, the design of the mold was continually developing, necessitating the adoption of expensive experimental approaches in industrial settings. To eliminate costly and time-consuming industrial experiments, software applications are being employed to imitate aditional casting methods that can be used in the casting of thermite steel during the fabrication of welded railway connections. This study presents a simulation of casting thermite steel in the mold cavity, i.e., in the weld joint, for the 49E1 rail using the NovaFlow & Solid CV software package
The removal of thiophanate-methyl using novely synthesized catalysts CeO2-P25 under simulated sunlight: Structural characterisation and photocatalytic activity
No full textEnvironmental pollution by wastewater
represents one of the greatest challenges nowadays.
The solution for this issue requires implementation
of novel treatment methods. Therefore, enhanced
techniques so-called Advanced oxidation processes
(AOPs) are gaining increasing attention.
Photocatalysis is a process based on the use of
different types of irradiations on a pollutants
adhered on a catalyst, driven by formation of
radicals and oxidative species on the catalyst
surface. Modern agricultural practice relies on use
of different classes of pesticides, and to its, often,
uncontrolled and excessive use. It leads to their
widespread in the environment, with frequent
detection in waterbodies and soil. Thiophanatemethyl
(TPM) is benzimidazole fungicide, used in
control of diverse groups of phytopatogenic fungus
[1].
Specifically efficient and economically viable
catalysts are TiO2-based. Multiphase catalysts
showed better results in the degradation of various
pollutants, so TiO2 P25 (Degussa) was used as a
material that boosts photocatalytic decomposition.
In order to advance and fasten the reaction, the
surface of TiO2 P25 was decorated with cerium (IV)
oxide [2]. Surface and photochemical properties of
newly obtained material are characterised by
HR - TEM, HAADF - STEM; FTIR and UV - DRS
methods.
In this study, the photocatalytic degradation of
thiophanate-methyl (TPM) in the presence of
CeO2 - P25 was investigated. Different
experimental conditions were varied, such as the
concentration of the pesticide solution and the mass
of the catalyst. Monitoring of the pesticide
concentration in the reaction system was based on
the decrease in absorbance using a Shimadzu 1800
UV spectrophotometer.
Results of textural and structural analyses prove
decoration of P25 surface with particles of cerium
(IV) oxide uniformly. Synthesised nanocatalyst
CeO2-P25 has lower band gap energy (2.90 eV) then
P25 (3.30 eV).
The optimal experimental conditions were
obtained using 0.07 g/L of CeO2-P25 and 5 mg/L of
TPM solution. Degradation reaction rate follows
pseudo-first order law. Complete degradation was
performed after 120 min. In experiments with TiO2
P25 catalyst (Degussa) degradation time was 240
min. Hence, it can be concluded that the synthesized
CeO2-P25 catalyst has better performance
Investigation of the possibility the Pb-Zn slag from "Topionica" -Veles quality improving using magnetic separation
No full textSmelting slag from "Topionica" -Veles (Northern Macedonia) owned by the company "KEPS MONT GROUP" Skopje is a potentially valuable raw material. Tests have shown that this is an inhomogeneous raw material with significant contents of non-ferrous metals, primarily Pb, Zn, Cu, and silver is present from precious metals. Mineralogical tests have shown that the composition of man-made raw materials is very complex and consists of amorphous and mineral phases, ie the microscopic method showed the following composition: amorphous phase, lead alloys, zinc alloys, vistite (FeO), sphalerite, galena, cerusite, elemental silver, elemental copper, elemental iron, magnetite, spinel, rutile, hematite, troilite (FeS). The most common amorphous phase (glass matrix) of spinel, silicate and mixed (spinel-silicate) composition is in the sample, while vistite, which occurs in the form of skeletal separations in the glass matrix, is significantly less represented. Based on SEM analysis (scanning electron microscopy), these are Fe-Mn-Zn spinels. Lead and zinc alloys are the most common. Mineralogical analysis by size classes determined that useful and unuseful components of Pb-Zn slag "Veles" were released at a fineness of -0.1 + 0.00 mm, so that magnetic separation tests were performed on this size class. Magnetic separation was performed on two devices, a Davis wet analyzer and a dry disk magnetic separator. By magnetic separation on a Davis magnetic separator, a small degree of iron concentration in the MF (1,134) relative to the input was obtained, with low iron distribution in the magnetic fraction of 16.79%. Magnetic separation on a dry disk magnetic separator also yielded a low degree of iron concentration in the magnetic fraction with distribution of 55.38% and 44.62% in the non-magnetic fraction
Investigation of the possibility of application of mechanochemically activated sodium carbonate in environmental protection
No full textThere is a growing problem in the world of eliminating carbon dioxide and the atmosphere,
which leads to the greenhouse effect, and causes a constant increase in the average
temperature on Earth. Cutting large green areas in order to obtain space for cattle breeding is
especially present in Brazil and Argentina. Increasing CO2 concentrations and rising air
temperatures are leading to the melting of large ice masses causing rising sea levels. That is
why the issue of eliminating carbon dioxide from the air is a priority in environmental
protection. Sodium carbonate samples were activated for 1 to 28 minutes in a vibro mill. The
increase in the free surface area of the activated samples was monitored by the BET method,
and the state of the crystal lattice by the diffraction method. The analysis of the results
showed a significant increase in the free surface of the activated material as well as
significant changes in the crystal structure of the samples due to grinding in a vibro mill. Such
activation of sodium carbonate would enable a significant increase in the sorption properties
of sodium carbonate and its application
Electrochemical stability of gold complex based on mercaptotriazole at optimal condition
No full textThis study investigates the electrochemical stability of the gold complex based on mercaptotriazole at an optimum pH of nine in the electrolyte with a gold concentration of 2.5 g dm(-3). The stability of the complex was studied by visual monitoring and electrochemical characterization of electrolytes over a period of 1 year. Electrochemical characterization of the mercaptotriazole gold complex was performed using open circuit potential measurement, cyclic voltammetry, recording the polarization curves, pH, and conductivity of the electrolyte. Electrochemical characteristics and visual appearance of the mercaptotriazole gold complex at a pH similar to 9 were not significantly changed for one year, with no changes in its visual appearance. The results of this study are important for industrial applications in order to replace cyanide electrolytes with a stable organic complex
Calcium-pyro-hydrochar derived from the spent mushroom substrate as a functional sorbent of Pb2+ and Cd2+ from aqueous solutions
No full textA calcium-pyro-hydrochar (Ca-PHC) can be distinguished as a novel sorbent of Pb2+ and Cd2+ from an aqueous solution. It was obtained using hydrothermal treatment of the spent mushroom substrate (SMS), followed by a CaCl2 center dot 5H(2)O activation and pyrolysis. The characterisation of chars before and after modifications was done by scanning electron microscope (SEM), Brunauer-Emmett- Teller (BET) and Fourier transform infrared (FTIR). Batch experiments were performed to examine Ca-PHC's sorption properties and binding mechanisms to selected metal ions. The maximum sorption capacities of Ca-PHC for Pb2+ and Cd2+ were 297 mg g(-1) , and 131 mg g(-1) respectively. The obtained results demonstrated that the sorption of Pb2+ and Cd2+ by Ca-PHC follows a pseudosecond kinetic model and Freundlich isotherm. The binding of the selected metals onto Ca-PHC was enabled by the ion-exchange mechanism, surface complexation, mineral precipitation and cation-pi interaction. Thermodynamic parameters indicate that metal ions binding by Ca-PHC are spontaneous and endothermic. Due to the high adsorption capacities, the obtained Ca-PHC has good potential for application in industrial wastewater treatment. In addition, the demonstrated use of SMS highlights another possibility of applying this specific biomass relevant to sustainable and economical waste management in the growing mushroom industry
Cleavage Fracture of the Air Cooled Medium Carbon Microalloyed Forging Steels with Heterogeneous Microstructures
No full textCleavage fracture of the V and Ti-V microalloyed forging steels was investigated by the four-point bending testing of the notched specimens of Griffith-Owen's type at -196 degrees C, in conjunction with the finite element analysis and the fractographic examination by scanning electron microscopy. To assess the mixed microstructure consisting mostly of the acicular ferrite, alongside proeutectoid ferrite grains and pearlite, the samples were held at 1250 degrees C for 30 min and subsequently cooled instill air. Cleavage fracture was initiated in the matrix under the high plastic strains near the notch root of the four-point bending specimens without the participation of the second phase particles in the process. Estimated values of the effective surface energy for the V and the Ti-V microalloyed steel of 37 Jm(-2) and 74 Jm(-2), respectively, and the related increase of local critical fracture stress were attributed to the increased content of the acicular ferrite. It was concluded that the observed increase of the local stress for cleavage crack propagation through the matrix was due to the increased number of the high angle boundaries, but also that the acicular ferrite affects the cleavage fracture mechanism by its characteristic stress-strain response with relatively low yield strength and considerable ductility at -196 degrees C
Application of the Hazardous Waste Vitreous Enamel Generated in the Production Process of Heating Devices as a Partial Replacement for Cement
No full textSolving problems with hazardous waste materials is of crucial importance today. In the presented study, the application of waste vitreous enamel as a cement replacement up to 30% in mortar and concrete production was investigated. The chemical and physical-chemical characterization of the starting material was performed, as well as a leaching test and physical-mechanical characterization of mortar and concrete mixes. Obtained results showed that, due to its chemical composition, the vitreous enamel used must be classified as hazardous waste. At the same time, it possesses pozzolanic properties and satisfies minimal criteria for use as a cement replacement. Testing mortars and concrete mixes indicate that waste vitreous enamel can be applied as a construction material for cement replacement in the maximal amount of 20%. The leaching test was performed in accordance with international standard EN 12457-2 on hardened mortar with a maximal cement replacement of 20%. The results showed that there was no significant release of toxic elements, i.e., that the practical application of hazardous waste vitreous enamel in the construction industry may be fully in line with environmental standards