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Sustainable mining and acid mine water treatment
No full textThe mining sector, nowadays, faces rising
challenges to find suitable practice that are
sustainable for already disposed waste streams
(AMD, flotation tailings and fly ash) [1]. There is a
growing tendency globally to use waste from
various industries to neutralize AMD, which has
both economic and environmental benefits. In
attempt to connect mining waste with concept of
sustainable development in the Republic of Serbia,
several experiments were taken into consideration:
neutralisation of AMD from Bor’s mine with a)
flotation tailings from copper mine Majdanpek
(FJM) b) fly ash (FA) from thermal power Nikola
Tesla (EF) and Kostolac (KOST). All three samples
of alternative product are voluminous, hazardous
waste products, difficult and expensive for safe
deposition, causes environmental pollution (by
spontaneous leaching of useful components, which
causes additional investment in the rehabilitation of
that or reversibly lost compounds that pollutes the
environment, or its dispersion by wind in
surrounding streams and groundwater resources of
drinking water, air or soil and also degradation by
soil erosion) and can affects human health’s if are
not regularly discharged. But its benefits are that
there are free of charge alkaline wastes, suitable to
neutralize the AMD by altering pH, which leads to
precipitation of valuable metal which can be reused,
such as Fe or Cu. The chemical and mineralogical
composition of the initial samples of FJM and FA
was evaluated two standard leaching tests: TCLP
and EN 12457-4, as well as Acid Neutralization
Capacity test. These base materials were shown to
have a large capacity to neutralize acid, making
them a highly effective alternative material for
neutralizing acid mine drainage and eliminating
metals, even better than results of neutralisation
with NaOH, as conventional reagent. According to
the findings the FJM and FA neutralization
experiments precipitated more than 99 % of Al, Fe,
and Cu, 90 % of Pb, and 92 % of Zn. Leaching of
these metals from FJM and FA raises Cd and Mn
concentrations. Additional treatment was
undertaken using hydrated lime to boost the pH to
10 and so offer circumstances for its removal, in
order to reduce the concentration of Mn below the
authorized limits by Serbian legislation. At the end,
as a result of utilizing alternative materials such as
FJM and two FA purified water, safe for release into
the environment was obtained. In this way,
resources are preserved for the future generation,
and the treatment of already disposed amounts of
waste reduces the contamination of the
environment, the emission of toxic metals and the
formation of acidic mine waters
Possibility of “Topionica” - Veles Pb-Zn slag valorization by gravity concentration procedure
No full textThis paper presents the results of laboratory tests of the valorization possibility of Pb-Zn slag "Smelter" -Veles, by gravity concentration. It is an inhomogeneous raw material that has a significant content of non-ferrous metals, primarily Pb, Zn and Cu, as well as the presence of precious metal in the form of Ag. The contents of the mentioned non-ferrous metals vary from a few percent to over 10%. The content of silver also varies from a few grams per ton to as many as tens of grams per ton of technogenic raw materials. Mineralogical analysis of the products of the grinding experiment by size classes determined that the useful components from Pb-Zn slag "Veles" are free at grinding fineness of -0.1 + 0.00 mm. Thus, the prepared technogenic raw material was subjected to magnetic separation and gravitational concentration processes. In this paper, only gravitational concentration is treated. It was decided to perform the gravitational concentration of the individual size classes on the Wilfley 13 shaking table, with the selected table surface for small classes and sludges. The obtained results of gravitational concentration of different size classes show that there was a separation of individual components into separate products.. This operation of the lead separation into concentrate (ΔH fraction) and silver in lead concentrate (ΔH fraction) was relatively successful, while the separation of zinc and copper in concentrate (ΔH fraction) gave slightly worse results. The best results in terms of content of Pb, Zn, Cu and Ag in concentrate (ΔH fraction) were achieved for the largest class (-100 + 75 μm) where the content of Pb in this product is 8.44%, zinc 7.42%, copper 0.77% and silver 125 g/t. In all other concentrates (ΔH fractions) obtained from smaller size classes, lower contents of non-ferrous metals and silver in them were obtained
Limestone of „Međeđe“ Nikšić as filer in various industries
No full textThis paper presents the results of testing the possibility of using limestone from the „Međeđe“ - Nikšić
deposit in different industries. During the examination, the coarse moisture, chemical composition,
granulometric composition, bulk and particle density, degree of whiteness, oil and water absorption,
granulometric composition of micronized samples and specific surface area were determined. All tests
were performed on 8 samples taken from different parts of the deposit and the mean values of the
obtained results are presented here. Based on the physico-chemical characteristics, it can be stated that
this limestone has a high content of CaO and CaCO3 of 99.01%, as well as a relatively low content of
MgO of 0.32% and a low content of SiO2 of 0.26% and alkali and R2O3, with also low content of heavy
metals, which is very favorable for limestone. With these physico-chemical properties, this limestone
can be used in the following industries: paints and varnishes, paper, rubber and PVC, foundry and
foundry industry, sugar industry, metallurgical purposes, glass production, animal feed production and
mineral fertilizer production. A serious defect of „Međeđa“ limestone is the low degree of whiteness,
which does not exceed 89.6%, which prevents its use in the pharmaceutical and chemical industries,
while the relatively high content of K2O, Fe and Mn prevents its use in calcification of acid soils
Renewable hydrogen production perspective in Serbia via biogas generated from food processing wastewaters
No full textRenewable hydrogen produced from the waste streams can be a good option for clean energy production and reduction of greenhouse gases emissions into the environment. In this study, the potential for hydrogen production from the food industry wastewaters in Serbia and the further use of the calculated potentials were investigated. This was performed through two technological routes including the biogas steam reforming process and the electrolysis after biogas cogeneration process. Furthermore, the environmental impacts of these processes were considered. The total hydrogen potential via the biogas steam reforming process was 4094.70 tons, while the total hydrogen potential via the electrolysis after biogas cogeneration process was 1751.08 tons. These potentials can be used for direct energy production in the food industry, electricity production for the national electric grid, transport, injection in the natural gas grid and/or as a resource in the chemical industry. Regarding the Greenhouse Gas emissions reduction, hydrogen production by both routes represents a promising pathway. The results of this work can serve the decision makers to plan hydrogen application in the energy sector of the Republic of Serbia defining supporting measures for its application. Also, the presented analysis is enforceable in the Western Balkan countries for the application of hydrogen as an energy source in their systems for energy production, transport and economy
A Mechanism Assessment and Differences of Cadmium Adsorption on Raw and Alkali-Modified Agricultural Waste
No full textIn this study, raw corn silk was considered for the removal of cadmium ions from aqueous solutions. In order to improve adsorption characteristics, the KOH treatment was applied as a route to obtain modified materials. Both materials before and after metal adsorption were characterized by pH(PZC), SEM-EDX and FTIR analysis. SEM images and FTIR spectra revealed that alkali modification caused some structural changes that could improve the adsorption properties of the investigated material. The experimental results and the ion-exchange study revealed that the biosorption process of cadmium ions on to raw and modified corn silk was caused predominantly by the ion-exchange mechanism, followed by chemisorption. The kinetic parameters implied that there are three stages in the biosorption process. In addition, the cadmium adsorption on both materials is very fast and is followed by the pseudo-second-order kinetic model. The experimental results were fitted by two and three parameter isotherm models, while the Sips isotherm model best describes the biosorption process on both materials. According to the Sips isotherm model, the maximum adsorption capacity of cadmium adsorbed on modified materials was 49.06 mg g(-1), which is 2.23 times greater in comparison to the raw material (21.96 mg g(-1)). Furthermore, the mechanisms of cadmium adsorption onto the investigated materials are summarized in order to better understand the modification influence on the adsorption properties of corn silk. In order to examine reusability of the investigated material, diluted nitric acid was used for regeneration. A desorption study was performed in three adsorption-desorption cycles. A high desorption efficiency (>85%) indicated that MCS after Cd adsorption can be efficiently recovered and reused for a new adsorption cycle
The Analysis of the Nucleation Process of the Lithium Germanium Phosphate Glass
No full textThe nucleation process of lithium germanium-phosphate glass was studied to determine the temperature range of nucleation and the temperature of the maximum nucleation rate. The differential thermal analysis (DTA), and scanning electron microscope (SEM) were used to reveal the nonisothermal and isothermal process of nucleation, respectively. The crystallization process occurred at a high homogeneous nucleation rate and the spherulitic crystal growth morphology. Nanostructured samples were obtained
A Multifocal Study Investigation of Pyrolyzed Printed Circuit Board Leaching
No full textElectric waste from numerous devices that are put out of use every day has some form of printed circuit board that contains precious and valuable metals in their components. In order to extract these metals, the printed circuit boards were crushed and pyrolyzed into powder. The fine pyrolyzed printed circuit board (PPCB) powder was separated into fractions, and the fine metallic fraction was used as a raw material for metal leaching extraction. In order to better understand how various metal species react in leaching media, several leaching agents were used (sulfuric acid, nitric acid, glycine, and acid mine drainage-AMD) alone, and with the addition of hydrogen peroxide. Additionally, the influence of the S/L ratio and leaching temperature were investigated in sulfuric acid leaching solutions, as this is the one most widely used. In one case, the reactor was heated in a thermal bath, while in the other, it was heated in an ultrasonic bath. Lastly, several experiments were conducted with a (consecutive) two-pronged leaching approach, with and without applied pretreatment. The aim of this paper is to give a multifocal and detailed approach to how metals such as Al, Cu, Co, Zn, Sn, and Ca behave when extracted from fine PPCB powder. However, some attention is given to Nd, Pd, Pb, and Ba as well. One of the main findings is that regardless of the pretreatment or the sequence of leaching media applied, consecutive two-pronged leaching cannot be used for selective metal extraction. However, AMD was found to be suitable for selective leaching with very limited applications
Structural changes of waste biomass induced by alkaline treatment: the effect on crystallinity and thermal properties
No full textA low-cost waste biomass generated from a food industry, apricot shells, was subjected to alkali modification in order to compare morphology, crystalline structure and thermal stability of native and modified biomass, accompanied by their cellulose-rich fractions. The surface morphology and structure of compared samples were analysed by the scanning electron microscopy (SEM) and mercury porosimetry. Furthermore, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal analysis (TG/DTA) were applied. The results have shown that after alkaline treatment, inter- and intra-particle porosity in the material rises, resulting in increase of the total surface area. The XRD diffractograms showed that crystallinity index increased together with crystallite size, suggesting that modified sample has more ordered crystalline structure than native sample (also confirmed by the FTIR analysis). Although the cellulose-rich fraction extracted from the alkali-modified sample showed higher thermal stability, the overall thermal analysis revealed that alkali-modified biomass has lower thermal stability than the native sample. This indicates that this type of modification will improve the fuel properties of this lignocellulosic biomass and imply its possible application in energy recovery process
Physical simulation of finish rolling of microalloyed steels in isothermal conditions
No full textThe aim of this work was to establish a temperature of finish rolling stage of Nb/Ti microalloyed steel containing 0.06 wt.% C, 0.77 wt.% Mn, 0.039 wt.% Nb and 0.015 wt.% Ti, using physical simulation. Samples were subjected to laboratory simulation at a twist plastometer at high temperatures, i.e. between 825 and 950 degrees C. Five pass deformation and interpass times were selected in accordance with a processing parameters at five stand finishing hot strip mill. Restoration (recovery and/or recrystallization) behavior was evaluated by calculation of Fraction Softening (FS) and Area Softening Parameter (ASP) values. At 950 degrees C all individual pass stress-strain curves, FS and ASP show full recrystallization in all interpass intervals. On the other hand, with a decrease in temperature to the interval of 875-825 degrees C, the extent of restoration is decreasing, leading to recovery as a sole softening mechanism at 825 degrees C, which was confirmed by the stress-strain curve shape, and values of FS and ASP. It is assumed that, due to high supersaturation, strain-induced precipitation promoted pinning of grain and subgrain boundaries and suppressed recrystallization. Therefore, the critical temperature for finish rolling was estimated to be 825 degrees C
Applicability of the risk ranking methodology designed for water reservoirs to tailings storage facilities
No full textThe risks associated with operating water reservoirs and tailings storage facilities (TSFs) are different because of their different purposes, methods of construction and operation, and characteristics of the materials impounded and their flow behaviour. Regardless of the differences, these two types of structures are often put in the same category when it comes to risk assessment and the application of relevant methodologies, which may result in unrealistic outcomes. In this paper we investigate whether it is possible to apply the risk ranking methodology designed for water reservoirs to TDFs and overview the key differences between these two types of structures. We also provide a comparative analysis of the results obtained by conducting a risk assessment of the operation of a TSF, applying the method recommended by the International Commission on Large Dams (ICOLD), and analyse the results using the failure mode and effects analysis (FMEA) technique. It is concluded that a more realistic evaluation of risk levels can be obtained by adopting a systematic approach to risk assessment in accordance with the traditional risk definition on which the FMEA technique is based