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Technical features of Pb-Zn slag that allow its valorization and application
No full textAccording to earlier physical-chemical and mineralogical analysis, slag from "Topionica"-
Veles (Northern Macedonia) represents a potentially important raw resource. It is an
inhomogeneous raw material with considerable nonferrous metal content, particularly Pb, Zn,
Cu, and Ag (considered as a precious metal). This technogenic resource's mineralogical
analysis revealed a very complex composition: amorphous phase, lead alloys, zinc alloys,
wüstite (FeO), sphalerite, galena, cerussite, elemental silver, elemental copper, elemental
iron, magnetite, spinel, rutile, hematite, troilite (FeS). The most abundant phase is an
amorphous phase (glassy matrix) composed of spinel, silicate, and mixed (spinel-silicate).
The sample has substantially less wüstite, that appears as skeletal inclusions in the glassy
matrix. SEM investigation revealed the presence of Fe-Mn-Zn spinels in the Pb-Zn slag, as
well as Pb and Zn alloys. These alloys are primarily composed of Cu. The grains of these
phases are up to 100μm appearing as inclusions (usually as complex inclusions with a glassy
matrix of elemental iron and wüstite). Grains bigger than 100μm in length are typically free
or have simple inclusions. The biggest grains in the aforementioned stages have diameters of
up to 300μm. The mineralogical study revealed that the Pb-Zn slag is a very complex raw
material. It is required to investigate it in detail and establish the methods in which it can be
done in order to value it and eventually apply it. Every stage of the preparation process has to
be accompanied by numerous analyzes that will indicate the relevance of the preparation
process and ways of concentrating useful components into commercial product
Thermal and adsorption study of the spent mushroom substrate and its hydrochar
No full textMushroom cultivation and consumption have been steadily increasing in recent decades, however, after mushroom cultivation, a large amount of by-products, known as spent mushroom substrate (SMS), are left behind in open dumps where about 5 kg of SMS are generated for every kilogram of mushroom (Agaricus bisporus). Around 51 million tons of SMS are produced in the world every year. Hydrothermal carbonization (HTC) is a promising technology for the conversion of SMS into a rich carbon product, hydrochar. The hydrochar was synthesized in a hydrothermal reactor at a temperature of 180 °C for a reaction time of 1 h. The characterization of the SMS and its chars was done by FTIR, SEM, and TGA analysis. The FTIR analysis showed that aromatic and oxygen-rich functional groups are dominant on the hydrochar surface. It was noticed that the hydrochar had more visible pores compared to the SMS. The porous structure and oxygen functional groups of hydrochar probably influenced the improvement of adsorption performance, since the adsorption capacity of SMS for Cd2+ ions was 28 mg L-1, while for hydrochar it was 92 mg L-1. On the other hand, the thermal kinetic analysis has shown that hydrothermally treatment upgrades the combustion behavior of hydrochar. The kinetic parameters were determined by Kissinger and Ozawa methods. The hydrochar had notably lower activation energy compared to the SMS, which means that this hydrochar requires a smaller amount of energy to start combustion. The preliminary results show that HTC effectively transforms SMS into alternative solid biofuel and eco-friendly sorbent
Food waste (beetroot and apple pomace) as sorbent for lead from aqueous solutions – alternative to landfill disposal
No full textThis article presents studies, whose main goal was to minimize food waste. To achieve this goal, it is necessary to expand the scope of their application, for example, for the purification of polluted water from heavy metals. Millions of tons of waste from the fruit and vegetable industry, including pomace of apples and beetroots, are thrown into landfills, posing a danger to the environment. In order to solve the problems with the disposal of these wastes, the authors investigated their sorption potential for the removal of lead from wastewater. The sorbents, dried apple (AP), and beetroots (BR) pomaces were characterized by various methods (study of composition, zeta potential, FTIR-ATR, and SEM-EDX). Various models of sorption kinetics and sorption isotherms were analyzed. Kinetical studies under optimal conditions showed that the sorption process occurs through complexation and ion exchange and the determining stage limiting the rate of sorption is the diffusion of lead ions in the sorbent. The maximum sorption capacity was 31.7 and 79.8 mg/g for AP and BR, respectively. The thermodynamic data revealed the spontaneous sorption of lead ions by sorbents. The temperature rise contributes to the sorption increase by the AP sorbent, while for the BR sorbent, the opposite effect is observed. The obtained results showed that apple and beetroots pomaces can serve as effective renewable materials for the preparation of sorbents, contributing to the solution of complex environmental problems
Influence of mold preheating on railway aluminothermic welding casting simulation
No full textRailway rails have been linked using the aluminothermic welding process for over a century. This method has several
advantages, including flexibility, compactness of the weld, and ease of execution. It is not necessary to employ outside
energy to complete the procedure. It is provided by the exothermic effect of the chemical reactions of the aluminothermic combination's elements. 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 the required quality welded joint. As a result, the mold's design was constantly evolving, necessitating the use of costly experimental procedures in industrial settings. In this iteration of the model the casting cavity was improved by adding hoes in the sand and putting rails on both sides in order to more aquratly simuate heat transfer. Software programs are being used to simulate conventional
casting procedures that can 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 package
was used to simulate casting thermite steel in the mold cavity, i.e. in the weld joint, for the 49E1 rail
Characterization of raw peach stones and its biochar by SEM, FTIR and Raman spectroscopy
No full textGrowing industrialization and non-renewable resource depletion have a huge impact on alternative clean up technologies
development, inducing investigation of the renewable, low-cost waste materials. Recently, lignocellulosic waste biomass,
generated at a large scale by different industries, appeared as an attractive feedstock worldwide, due to its abundance,
availability, multi-functionality and low cost. Since the fruits production has increasing trend all over the world,
generation of lignocellulosic waste such as fruit stones (that represent approximately 1/5 of the total fruit mass) became
a great environmental threat. In order to minimize negative impact on the environment, avoid greenhouse gasses emissions
and help in resource depletion by its renewable nature, it is necessary to explore its performances regarding its wide
application potential. Thermo-chemical conversion of lignocellulosic biomass in oxygen limited conditions, in order to
get biochar, has received a lot of attention recently. The biochar production requires lower energy inputs and less
expensive technology compared to activated carbon (estimation is that production cost of activated carbon are six times
higher than biochar costs).
In this paper, waste peach stones biomass was effectively converted into biochar at 500 °C under inert (Ar) atmosphere.
Pyrolysis was performed in Nabertherm 1300 muffle furnace for residence time of 1.5 h, with a heating rate of 10 °C/min,
while Ar was circulated through the sample at a rate of 100 mL/min. The raw biomass (PS) and obtained biochar (PS-B)
with particle size 0.1 mm < dp < 0.5 mm, were characterized by Scanning Electron Microscopy (SEM), Fourier transform
infrared spectrometry (FTIR) and Raman spectrometry to understand physicochemical changes which have been occurred
after pyrolysis. SEM analysis revealed the increased surface area due to the visible augmentation of pores and roughness.
FTIR analysis showed that many bands present in native biomass cannot be observed in biochar, due to the conversion or
removal of the most of the functional groups. Prominent bands have confirmed presences of aromatic compounds in
biochar: at 1592 cm−1 (C=C bond stretching derived from aromatic rings in the lignin), 1030 cm-1 (alcohol C-O stretching
vibration) and in the region 900 to 700 cm−1 (originating from aromatic compounds). These finding are in accordance
with results from Raman analysis, where D and G bands (at 1350 cm-1 and 1580 cm-1 respectively), indicate the presence
of poly-aromatic hydrocarbons.
Thermo-chemically modified biomass like this has a great application potential: as a pollutants sorbent, biofuel, soil
amendment, biocarriers, and in construction and electronic industries
The effect of SrO and La2O3 addition on the crystallization characteristics and sintering behavior of distinct polyphosphate glasses
No full textThe goal of this research is to investigate the effect of SrO and La2O3 addition on the crystallization characteristics and sintering behavior of polyphosphate glasses. Differential scanning calorimetry (DSC), hot stage microscopy (HSM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) methods were used to investigate the crystallization and sintering behaviors of glasses. The addition of SrO and La2O3 (1 or 5%), at the expense of phosphate mole fraction in polyphosphate bioactive glass, raises the characteristic temperature of glasses, and resistance to crystallization. Furthermore, the temperature of maximal shrinkage increases with the addition of SrO and La2O3. Surface crystallization is the dominant mechanism of crystallization in all samples. All glasses show complex crystallization leading to the formation of several crystalline phases. Sintered phosphate glass-ceramic containing bioactive beta-CaP2O6, alpha-Ca-3(PO4)(2,) and beta-Ca-3(PO4)(2) phases were successfully prepared
Seeded silicon nitride powders obtained by carbothermal reduction—nitridation of diatomite and various sources of carbon
No full textIn this paper, the effects of the addition of silicon nitride seeds on the phase composition, particle size, and shape of silicon nitride powders obtained by carbothermal reduction-nitridation were studied. Environmentally friendly natural raw material, diatomaceous earth, was used as a Si precursor. Three different carbon sources were used: activated carbon, carbonized sucrose, and carbon cryogel as reducing agents in the molar ratio C/SiO2 = 5. To obtain better-quality Si3N4 powder, the commercial α-Si3N4 powder was added into starting mixtures as seeds in four different quantities. The X-ray diffraction, specific surface area, infrared spectroscopy with Fourier transform, and scanning electron microscopy were employed to characterize the obtained powders. Sucrose as a carbon source enables a major reduction of SiO2 and the onset of β-Si3N4 crystallization at a lower temperature (1350 °C) as well as the complete absence of diatomaceous earth relics. It indicates that the carbothermal reduction-nitridation takes place faster in contrast to the other two carbon sources
Cobalt extraction from spent lithium-ion battery cathode material using a sulfuric acid solution containing SO2
No full textTo increase the degree of cobalt (Co) extraction, the process of the cathode material leaching was performed in a sulfuric acid (H2SO4) solution containing sulfur dioxide (SO2) as a reducing agent. To provide a high resolution of the obtained results, frequent monitoring of Co concentrations in leached solution was conducted using an ultraviolet–visible spectrophotometer with several specific modifications related to the connection of the reaction vessel with the instrumental cuvette. The maximum degree of Co leaching (99.4%) was achieved with H2SO4 concentration of 3 mol/L, solid phase concentration of 33 g/L, temperature of 85 °C, SO2 volume flow of 2 L/min, and leaching time of 60 min. The results of the performed kinetic analyses indicated that the Avrami equation best describes the investigated leaching process, which later was supported by the results of X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy analyses. Also, the activation energy of 28 ± 3 kJ/mol is in favor of the fact that the process of Co leaching was controlled by the factors, such as diffusion and chemical reaction. The results of this study indicated that SO2 can be used as an effective reducing agent in the investigated process
Morphological assessment of cavitation caused damage of cordierite and zircon based materials using principal component analysis
No full textThe pattern recognition approach, explored by this study, applies the principal component analysis (PCA) as the most widely used statistical method with the aim of assessing the initiation and propagation of the cracks and defects that appear on the surface of material exposed to the cavitation. The experiment was performed in four stages: (a) synthesis of two ceramic materials (cordierite and zircon); (b) subjecting the samples to the cavitation; (c) using image analysis software for collecting the data about morphological characteristics that describe defects; (d) principal component analysis as a pattern recognition tool in order to characterize the defects at the material surface. Besides that, according to standard, cavitation erosion was monitored by determining material mass loss during the cavitation. Large experimental datasets collected from morphological descriptors by image analysis are multivariate and difficult to interpret, thus are processed by principal component analysis as the most informative technique for extracting possible differences. The performed approach proved that this method has a great potential for better assessment of induced defects by proper distinguishing among them at different levels and that can be considered a very efficient and cost-effective one
Insights into the application of polyaniline-based composites in environmental engineering
No full textEnvironmental management demands innovative techniques for its protection and
treatment. The essential agreement of the modern world is to overcome every issue in a
sustainable way. The two major financial problems in this area are water pollution and
material corrosion. Persistent, organic compounds such as pesticides have devastating effects
on the water ecosystem. This problem can be solved by applying advanced treatment processes
(ATPs) like membrane separation and photocatalysis. Additionally, the corrosion of metal
materials needs to be prevented to preserve natural resources and reduce environmental
concerns. Therefore, researchers are trying to develop tunable, multifunctional materials
with broad applications. Employed materials in these operations must fulfill high criteria, like
durability, stability, and chemical and optical activity, to make specified processes efficient
and viable. Electroconductive polymers (ECPs) can meet the aforementioned standards. The
most used ECP is polyaniline (PANI), due to its catalytic and electrochemical performances.
These two properties are beneficial for both water purification and anticorrosion applications.
The objectives of the paper are to represent various PANI-based composites utilized in the
removal of different classes of pesticides during wastewater treatment by adsorption or
photocatalytic degradation. Further corrosion inhibition, utilizing PANI-based inhibitors, will
be discussed as well