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Volume 67 (2020): Issue 4 (December 2020)

Volume 67 (2020): Issue 3 (September 2020)

Volume 67 (2020): Issue 2 (June 2020)

Volume 67 (2020): Issue 1 (March 2020)

Volume 66 (2019): Issue 4 (December 2019)

Volume 66 (2019): Issue 3 (December 2019)

Volume 66 (2019): Issue 2 (June 2019)

Volume 66 (2019): Issue 1 (March 2019)

Volume 65 (2018): Issue 4 (December 2018)

Volume 65 (2018): Issue 3 (September 2018)

Volume 65 (2018): Issue 2 (September 2018)

Volume 65 (2018): Issue 1 (March 2018)

Volume 64 (2017): Issue 4 (December 2017)

Volume 64 (2017): Issue 3 (September 2017)

Volume 64 (2017): Issue 2 (July 2017)

Volume 64 (2017): Issue 1 (March 2017)

Volume 63 (2016): Issue 4 (December 2016)

Volume 63 (2016): Issue 3 (September 2016)

Volume 63 (2016): Issue 2 (July 2016)

Volume 63 (2016): Issue 1 (May 2016)

Journal Details
Format
Journal
eISSN
1854-7400
First Published
30 Mar 2016
Publication timeframe
4 times per year
Languages
English

Search

AHEAD OF PRINT

Journal Details
Format
Journal
eISSN
1854-7400
First Published
30 Mar 2016
Publication timeframe
4 times per year
Languages
English

Search

15 Articles
Open Access

Regression methods for evaluation of the underwater noise levels in the Slovenian Sea

Published Online: 11 Dec 2021
Page range: -

Abstract

Abstract

Anthropogenic underwater noise pollution of seas and oceans caused by shipping can have negative effects on marine animals. The aim of this study was to evaluate quantitatively how much the underwater noise levels in the Slovenian Sea were influenced by anthropogenic pressures and meteorological parameters in the period from 2015 until 2018. For this purpose, correlation method and least squares multiple linear regression analysis were used. The results of this study show that the correlation of underwater noise levels with the dredging activity is significant but low, while correlation with the ship densities is insignificant, which could be due to reduced sound wave propagation in the shallow sea levels. Correlation of the underwater noise levels with the wind speed was significant but low to medium, which could be explained by the breaking waves generated by the wind that produced sound.

Keywords

  • Underwater noise
  • correlation
  • multiple linear regression
  • anthropogenic pressures
  • meteorological parameters

Ključne besede

  • Podvodni hrup
  • korelacija
  • multipla linearna regresija
  • antropogeni pritiski
  • meteorološki parametri
Open Access

Physico-Chemical Trends in the Sediments of Agbede Wetlands, Nigeria

Published Online: 23 Jun 2017
Page range: -

Abstract

Abstract

This study assessed the physico-chemical status of sed­iments in the Agbede Wetlands with the aim to create a reference archive for the Edo North catchment and to further identify the characteristics mostly influenced by the natural and anthropogenic activities going on at the watershed. Nutrients, zinc, nickel and lead were identified to be mostly of anthropogenic origin, while alkali metals and alkaline earth metals were from both anthropogenic and natural sources. The clustering of stations 1 and 4 indicates that the sediment quality in the lentic systems was not completely excluded from the lotic system, suggesting that principal component analysis (PCA) and cluster analysis (CA) techniques are invaluable tools for identifying factors influencing the sediment quality. The mean values of the particle size distribution were in the following order across the ecosystems: sand (61.86-80.53%) > silt (9.75-30.34%) > clay (7.83-13.89%). The contamination of the water bodies was primarily derived from agricultural run-offs and through geochemical weathering of the top soils. Therefore, our analysis indicates that the concentra­tions of cations, anions and nutrients in the sediments of the lotic and lentic ecosystems in Agbede Wetlands are not at an alarming level.

Keywords

  • sediment
  • physico-chemical character­istics
  • pond
  • stream
  • principal component analysis
  • watershed
Open Access

Copper tailings reprocessing

Published Online: 10 Jan 2022
Page range: -

Abstract

Abstract in English

Copper is widely used in the modern world. An excellent conductor of electricity, it is used in the electrical industry, in the construction industry because of its good corrosion resistance, and in the manufacture of heat exchangers in heating and cooling systems owing to its excellent thermal conductivity. Copper production has increased throughout the twentieth century, and this trend has continued over the last twenty years. The demand for copper is expected to increase significantly by the year 2030. Owing to the high prices of this metal and the lack of deposits, part of the demand can be met by extraction from copper-bearing tailings. In the past, owing to the lower level of technological development and lower copper prices, materials comparable in copper content to the copper ores mined today have ended up in tailings. Since these are already processed materials, the costs of mining, crushing and milling are largely eliminated, making them promising raw materials. The article presents the technological possibilities of reprocessing and also estimates the amount of copper that could be obtained worldwide in this way.

Keywords

  • tailings reprocessing
  • multi-gravity separator
  • flotation
  • copper

Ključne besede

  • reprocesiranje jalovišč
  • multi-gravitacijski separator
  • flotacija
  • baker
Open Access

An analysis of coal consumption, CO2 emissions and economic growth in Slovenia

Published Online: 30 Dec 2021
Page range: -

Abstract

Abstract in English

The common characteristics and possible correlations between coal consumption, CO2 emissions, emission productivity and economic growth in Slovenia are discussed in this article. The correlation between these variables was analysed by using the Pearson correlation coefficient, and we used linear regression and the least squares method to develop predictive mathematical models that can be used to estimate trends in coal consumption and CO2 emissions in the future. The link between coal consumption, emissions, and emission productivity is significant, while the correlation between coal consumption and economic growth is minimal. Therefore, coal consumption and the resulting emissions do not have a significant impact on economic growth. Mathematical models show a good fit, which is a condition for the reliability of the prediction. Possible scenarios of the transition to carbon neutrality and the related problems of future electricity supply as a consequence of the cessation of coal mining and use are also discussed below.

Keywords

  • coal
  • emissions
  • correlation
  • forecasting

Ključne besede

  • premog
  • emisije
  • povezanost
  • napovedovanje
Open Access

Field Observations, Petrography, and Microstructures of Granite from Abeokuta Southwestern Nigeria

Published Online: 04 Feb 2022
Page range: -

Abstract

Abstract in English

The granite of Abeokuta is part of the Older Granite suite of the basement complex of southwestern Nigeria. Field observation has identified the granite as porphyritic in texture, with a preferred alignment of megacrysts of K-feldspar >5 cm that are mostly euhedral to subhedral in shape. K-feldspar megacrysts are predominantly yellowish, but whitish and pinkish colouration has also been observed. The dark grey porphyritic, mafic rock composition occurs as enclaves within the granite, with phenocrysts having a preferred alignment as the enclosing granite. Also, K-feldspar megacrysts show zoning defined by concentric arrangement of inclusions of biotite relative to the crystal faces. Petrographic study shows the following minerals in order of abundance: K-feldspar, biotite, quartz, and plagioclase, with K-feldspar having a microperthitic intergrowth and biotite crystals aligned in a preferred direction. Evidence such as the crystal shape of K-feldspars, preferred alignment of K-feldspar phenocrysts, and concentric crystallographic arrangements of inclusions of biotite in K-feldspar support a magmatic/phenocrystic origin of K-feldspar megacrysts of Abeokuta granite rather than originating by growing in a solid state as porphyroblasts.

Keywords

  • megacrysts
  • microperthitic
  • K-feldspar
  • zoning
  • porphyroblasts

Ključnebesede

  • vtrošniki
  • mikropertit
  • kalijev glinenec
  • conarna rast
  • porfiroblasti
Open Access

Valuation of Rubber Waste and Dune Sand: Mortar for Construction and Environmental Protection

Published Online: 23 Feb 2022
Page range: -

Abstract

Abstract

The main objective of this study is the recovery of dune sands and rubber waste (powders). The latter constitutes a potential source of several environmental and economic problems.

The objective of this present work is to examine the ability to use dune sand for the preparation of mortars with sufficient physico-mechanical properties to allow them to be used in various building construction applications. The formulation of the mixtures is based on replacing dune sand with powders, at different weight contents: 10 %, 20 %, and 30 %. The quantity of cement is set at 450 g. The results obtained show in the first place that the particle size of the mixture tends to be spread out with a remarkable increase in the fineness modulus, and in the second place the density of the mixture decreases by 6.5 % (for the apparent) and by 10 % (for the absolute), which means the calculation of loads for the resulting mortar must decrease. Porosity has decreased to 20 % and absorption has increased to 30%. The strengths have decreased over 40 % for compressive strength and over 30 % for tensile strength, with an improvement in the relationship between the two strengths.

Keywords

  • Mortar
  • dune sand
  • rubber
  • porosity
  • absorption
  • strength
Open Access

Lateral squeezing effects on cement-slag-bentonite slurry wall performance

Published Online: 02 Mar 2022
Page range: -

Abstract

Abstract

Cement-slag-bentonite slurry walls are self-hardening structures, and they are mainly used to retard contamination transport into the groundwater stream. Whilst permeability of a mixture is an initial criterion in slurry wall design and material selection, long-term performance is mainly influenced by curing ages and stress-state caused by adjacent soil. In this study, the steady-state of effective stresses at 7 days and 28 days of curing age is predicted. The effect of the modulus of horizontal subgrade reaction, interface friction, and transition of the earth pressure from at-rest to the active condition was applied to develop the model. Unlike the quantities that the geostatic model presented, this method gives a slight decrease of stresses after a certain depth, and the trend is in good agreement with trends provided by previous studies. Furthermore, the predicted stresses are then applied to estimate the permeability of the wall at each depth and compare it with those obtained in the laboratory. Finally, predicted effective stresses stay lower than geostatic stress, and the slurry wall consolidation along with the sidewalls’ lateral squeezing leads to keeping the stress state under control.

Keywords

  • cement-slag-bentonite
  • compressibility
  • lateral squeezing
  • permeability
  • slurry wall
Open Access

Hydrocarbon Potential and Biomarker Studies of EE-1 Well, Offshore Eastern Dahomey Basin, SW Nigeria

Published Online: 18 Mar 2022
Page range: -

Abstract

Abstract

The hydrocarbon potential, organic source input, and paleodepositional environment of subsurface sediments from EE-1 well, offshore Eastern Dahomey Basin, were assessed using Rock-Eval pyrolysis and biomarker geochemistry. The total organic carbon (TOC) and soluble organic matter (SOM) in the sediments ranged from 0.96wt% to 8.92wt% and 676.12 ppm to 2883.85 ppm, respectively, indicating adequate to excellent organic richness. The pseudo-Van Krevelen plot classified the sediments as types II and III kerogen, which have the potential to generate both oil and gas. The Tmax and production index (PI) ranged from 422°C to 431°C (average, 426°C) and 0.03 to 0.24, respectively, suggesting low thermal maturity. The presence of C27–C29 steranes, oleanane, and hopane/sterane ratio (1.53/16.11), indicated organic matter from mixed sources with more terrigenous input. Cross plots of Pr/nC17 against Ph/nC18, C35/C31 – C35 homohopane index (0.05 – 0.17) and other related biomarker ratios such as C21/C23 trycyclic terpane ratio (0.33 – 0.82) signified that the sediments were deposited in mixed marine/terrigenous environment under oxic – suboxic conditions. This study has demonstrated that sediments had adequate organic matter with the potential to generate both oil and gas at appropriate thermal maturity.

Keywords

  • hydrocarbon potential
  • biomarker
  • Dahomey Basin
Open Access

Returning Electrostatic Precipitators to the Fe-Ni Production Process

Published Online: 21 Mar 2022
Page range: -

Abstract

Abstract

The process of frying the Fe-Ni charge in rotary kilns inherently produces large amounts of process dust, which rotary kilns clean out through the use of electro-static precipitators [1].

One kiln contains two sections of electrostatic precipitators as a safety mechanism [1]. Electrodes installed in the sections produce electric fields when electricity passes through them, and ionize the dust.

The timing of the process must be coordinated carefully, and these electrodes are struck with hammers and occasionally shaken, generating quantities of dust which are then collected in a snail dust conveyor, then returned to the production process and recycled. In addition, a smaller amount of dust is derived from the gas chamber, which returns to production without entering the cleaning process in the electro filters. The difference between the two types of dust is their granulation size [1].

We conducted the research during the years from 2017 through 2020, calculating the components of the rotary kiln process. Here, we present a linear equation as a result of the ratio of calcine and electrofilter dust.

Keywords

  • dust
  • calcine
  • electro filter
  • adhesion
  • rotary kiln

Ključnebesede

  • prah
  • žganje
  • elektrofilter
  • adhezija
  • rotacijska peč
Open Access

Determining the Enthalpy of an Fe-Ni Alloy at Various Temperatures Using the ‘STA’ PT 1600 Equipment

Published Online: 21 Mar 2022
Page range: -

Abstract

Abstract

In this research paper we have determined the enthalpy of the Fe-Ni alloy using the ‘STA’ equipment at the laboratory of the University of Mitrovica “Isa Boletini”, Department of Materials and Metallurgy. The sample for analysis was taken at the Ferronikel plant, whereas the preparation of the sample for analysis on the ‘STA PT 1600’ equipment took place at the laboratory of the University of Mitrovica ‘Isa Boletini’.

The sample of the Fe-Ni alloy analysed was 2–4 cm in size, in the shape of a granule. It contained, 22.55% Ni, 76.51% Fe, and small amounts of other elements [1, 2]. During the analysis of the Fe-Ni alloy, we obtained three enthalpy values under analytical conditions that included a maximum temperature of 800 °C and a minimum temperature of 600 °C; the alloy was exposed to each temperature separately for 45 minutes at each temperature.

The results showed negative enthalpy values during the three scenarios examined and an exothermic process where ΔH<0 [3]. The enthalpy decreases as the system releases heat with an increase in temperature [4].

Keywords

  • STA
  • alloy
  • Fe-Ni
  • enthalpy
  • exothermic process

Ključnebesede

  • STA
  • zlitina
  • Fe-Ni
  • entalpija
  • eksotermni proces
Open Access

Identification of favourable geological formations for the determination of groundwater

Published Online: 25 Sep 2022
Page range: -

Abstract

Abstract

Clean drinking water supply is a major concern to the population of the urban municipality of Boké, Republic of Guinea. This study is aimed to investigate the favourable geological structure for the accumulation of groundwater in Boké. Apparent resistivity data was collected by using the Schlumberger-type vertical electrical sounding technique. The apparent resistivity values were obtained on a bi-logarithmic scale in which the distances AB/2 were plotted on the abscissa and the resistivities are on the ordinate. It found the number of terrains and their characteristics (resistivity and thickness) in the area and the behaviour of the current in the soil through a curve. The results show that the structures favourable to the accumulation of groundwater were fractured dolerites, cracked shales and cracked or crushed sandstones. The sandstones were the most important in terms of the amount of water. They are located at a depth of more than 100 metres. It was also found that dolerites and shales are located at shallower depths (less than 100 m).

Keywords

  • Groundwater
  • geo-electric method
  • litho-logical section
  • fracture zones
  • Prefecture of Boké

Ključne besede

  • podzemna voda
  • geoelektrična metoda
  • litološki profil
  • razpoklinska območja
  • Prefektura Boké
Open Access

Microstructure of a nickel insert, a special copper alloy, and a cast joint between them

Published Online: 01 Oct 2022
Page range: -

Abstract

Abstract

This work deals with the characterisation of the micro-structure of a nickel insert, a special copper alloy and the cast joint between them after their use as a glass manufacturing mould. The microstructure was characterised by optical microscopy, scanning electron microscopy and microanalysis by energy dispersive X-ray spectroscopy.

It was found that the nickel insert contained 7 at. % Si and 0.3 at. % Fe. The special copper alloy contains undesirable phases or compounds, including lead, aluminium-based oxides and borides. The borides are either iron-, iron-chromium- or chromium-based with different stoichiometries between metal components and boron. The cast joint between the nickel insert and the special copper alloy has evidence of mixing the two alloys, while only in some areas porosity and oxides prevented the formation of a suitable cast joint. Aluminium-based oxides and some borides could be the cause of the formation of cracks due to their morphology.

Keywords

  • nickel alloy
  • copper alloy
  • microstructure
  • microanalysis

Ključne besede

  • nikljeva zlitina
  • bakrova zlitina
  • mikrostruktura
  • mikroanaliza
Open Access

Solid Mineral Potential and Geothermal Energy Reserve of Northern Basement Complex, Nigeria

Published Online: 23 Oct 2022
Page range: -

Abstract

Abstract

The spectral analysis of aeromagnetic data over the study area (Northern basement complex, Nigeria) revealed the existence of two major source depths. The second segment of the spectrum layer shows shallow sources ranging in depth from 0.135 km to 0.201 km, with an average depth of 0.140 km. The depth to the basement or deeper source ranges between 1.655 km and 2.021 km, with an average depth of 1.882 km. The Precambrian basement is reflected in the deeper sources, beginning with the first segment of the power spectrum. Structural and topographic relief of the basement surface, lateral differences in basement susceptibilities, and intra-basement features such as faults and fractures contribute to the variation in basement composition. The mean thickness of sediments in the study area is represented by the D2 values obtained from the spectral plots. The depths revealed by this study appears to be reasonable and consistent with previous researchers’ findings. Tectonically active regions have a major impact on heat flows. The average heat flow in thermally normal continental regions is reported to be above 60 mW/m2. Values between 80 and 100 mW/m2 indicate a good geothermal source; values in excess of about 80–100 mW/m2 indicate anomalous geothermal conditions.

Keywords

  • 3-D Euler deconvolution
  • spectral inversion
  • magnetic basement depth
  • linear features
  • Nigeria

Ključne besede

  • 3-D Eulerjeva dekonvolucija
  • spektralna inverzija
  • globina magnetne podlage
  • linearne strukture
  • Nigerija
Open Access

Determination of material quality by methods of thermal analysis

Published Online: 07 Nov 2022
Page range: -

Abstract

Abstract

Cast aluminium alloys are commonly used in the automotive industry for casting applications. There are both primary and secondary/recycled aluminium alloys in the market, which differ in price and quality. In this study, the effect of alloy quality on solidification, microstructure and mechanical properties was investigated. The comparison of properties was carried out in the as-cast condition and in the heat-treated condition. The influence of alloy quality on solidification was analysed by simple thermal analysis and differential scanning calorimetry, and thermodynamic simulations. The basic mechanical properties analysed were tensile strength, yield strength, elongation, and hardness. The microstructural differences were analysed using a light microscope. The Mn:Fe ratio, which is strongly influenced by the alloy quality, was found to have a pronounced effect on the mechanical properties, while magnesium together with silicon hardens the aluminium matrix during heat treatment, which significantly increases the mechanical properties. This research proved that thermal analysis methods can give us a necessary and important indication of the quality of the alloys used.

Keywords

  • Alloy quality
  • casting alloys
  • thermal analysis
  • solidification
  • microstructure
  • mechanical properties

Ključne besede

  • kakovost zlitin
  • livarske zlitine
  • termična analiza
  • strjevanje
  • mikrostruktura
  • mehanske lastnosti
Open Access

Rare Earth Element Geochemistry and Abundances in Syenites and Charnockitic Rocks of Selected Locations within Southwestern Nigeria

Published Online: 18 Nov 2022
Page range: -

Abstract

Abstract

Rare earth elements (REE) are critical metals widely used in modern technology. There is an increased demand for these elements which has necessitated additional exploration. The REE geochemistry of syenites and charnockitic rocks from selected locations within southwestern Nigeria were studied to determine their concentrations, distribution patterns, and mineralisation potential to deduce if they can be economically exploited. Mineralogical studies were carried out using scanning electron microscopy (SEM). Ten rock samples including five syenites and five charnockites were analysed for their elemental composition using inductively coupled plasma – mass spectrometry (ICP-MS). The REE-bearing minerals identified from the SEM analysis include apatite and monazite. The fractionation ratio (La/Yb)N ranged from 29.36 to 48.75 for the syenites and from 24.43 to 48.29 for the charnockites, indicating magmatic differentiation. Total REE (∑REE) in the syenites (342–675 ppm) and charnockites (220–802 ppm) suggests that they are enriched with respect to REE but the REE concentration in the rocks of the study area had very low ∑REE compared to the REE contents of the rocks where they have been mined and may therefore not be economically viable.

Keywords

  • rare earth elements
  • syenites
  • charnockites
  • abundances
  • fractionation

Ključne besede

  • elementi redkih zemelj
  • sieniti
  • čarnokiti
  • vsebnost
  • frakcionacija
15 Articles
Open Access

Regression methods for evaluation of the underwater noise levels in the Slovenian Sea

Published Online: 11 Dec 2021
Page range: -

Abstract

Abstract

Anthropogenic underwater noise pollution of seas and oceans caused by shipping can have negative effects on marine animals. The aim of this study was to evaluate quantitatively how much the underwater noise levels in the Slovenian Sea were influenced by anthropogenic pressures and meteorological parameters in the period from 2015 until 2018. For this purpose, correlation method and least squares multiple linear regression analysis were used. The results of this study show that the correlation of underwater noise levels with the dredging activity is significant but low, while correlation with the ship densities is insignificant, which could be due to reduced sound wave propagation in the shallow sea levels. Correlation of the underwater noise levels with the wind speed was significant but low to medium, which could be explained by the breaking waves generated by the wind that produced sound.

Keywords

  • Underwater noise
  • correlation
  • multiple linear regression
  • anthropogenic pressures
  • meteorological parameters

Ključne besede

  • Podvodni hrup
  • korelacija
  • multipla linearna regresija
  • antropogeni pritiski
  • meteorološki parametri
Open Access

Physico-Chemical Trends in the Sediments of Agbede Wetlands, Nigeria

Published Online: 23 Jun 2017
Page range: -

Abstract

Abstract

This study assessed the physico-chemical status of sed­iments in the Agbede Wetlands with the aim to create a reference archive for the Edo North catchment and to further identify the characteristics mostly influenced by the natural and anthropogenic activities going on at the watershed. Nutrients, zinc, nickel and lead were identified to be mostly of anthropogenic origin, while alkali metals and alkaline earth metals were from both anthropogenic and natural sources. The clustering of stations 1 and 4 indicates that the sediment quality in the lentic systems was not completely excluded from the lotic system, suggesting that principal component analysis (PCA) and cluster analysis (CA) techniques are invaluable tools for identifying factors influencing the sediment quality. The mean values of the particle size distribution were in the following order across the ecosystems: sand (61.86-80.53%) > silt (9.75-30.34%) > clay (7.83-13.89%). The contamination of the water bodies was primarily derived from agricultural run-offs and through geochemical weathering of the top soils. Therefore, our analysis indicates that the concentra­tions of cations, anions and nutrients in the sediments of the lotic and lentic ecosystems in Agbede Wetlands are not at an alarming level.

Keywords

  • sediment
  • physico-chemical character­istics
  • pond
  • stream
  • principal component analysis
  • watershed
Open Access

Copper tailings reprocessing

Published Online: 10 Jan 2022
Page range: -

Abstract

Abstract in English

Copper is widely used in the modern world. An excellent conductor of electricity, it is used in the electrical industry, in the construction industry because of its good corrosion resistance, and in the manufacture of heat exchangers in heating and cooling systems owing to its excellent thermal conductivity. Copper production has increased throughout the twentieth century, and this trend has continued over the last twenty years. The demand for copper is expected to increase significantly by the year 2030. Owing to the high prices of this metal and the lack of deposits, part of the demand can be met by extraction from copper-bearing tailings. In the past, owing to the lower level of technological development and lower copper prices, materials comparable in copper content to the copper ores mined today have ended up in tailings. Since these are already processed materials, the costs of mining, crushing and milling are largely eliminated, making them promising raw materials. The article presents the technological possibilities of reprocessing and also estimates the amount of copper that could be obtained worldwide in this way.

Keywords

  • tailings reprocessing
  • multi-gravity separator
  • flotation
  • copper

Ključne besede

  • reprocesiranje jalovišč
  • multi-gravitacijski separator
  • flotacija
  • baker
Open Access

An analysis of coal consumption, CO2 emissions and economic growth in Slovenia

Published Online: 30 Dec 2021
Page range: -

Abstract

Abstract in English

The common characteristics and possible correlations between coal consumption, CO2 emissions, emission productivity and economic growth in Slovenia are discussed in this article. The correlation between these variables was analysed by using the Pearson correlation coefficient, and we used linear regression and the least squares method to develop predictive mathematical models that can be used to estimate trends in coal consumption and CO2 emissions in the future. The link between coal consumption, emissions, and emission productivity is significant, while the correlation between coal consumption and economic growth is minimal. Therefore, coal consumption and the resulting emissions do not have a significant impact on economic growth. Mathematical models show a good fit, which is a condition for the reliability of the prediction. Possible scenarios of the transition to carbon neutrality and the related problems of future electricity supply as a consequence of the cessation of coal mining and use are also discussed below.

Keywords

  • coal
  • emissions
  • correlation
  • forecasting

Ključne besede

  • premog
  • emisije
  • povezanost
  • napovedovanje
Open Access

Field Observations, Petrography, and Microstructures of Granite from Abeokuta Southwestern Nigeria

Published Online: 04 Feb 2022
Page range: -

Abstract

Abstract in English

The granite of Abeokuta is part of the Older Granite suite of the basement complex of southwestern Nigeria. Field observation has identified the granite as porphyritic in texture, with a preferred alignment of megacrysts of K-feldspar >5 cm that are mostly euhedral to subhedral in shape. K-feldspar megacrysts are predominantly yellowish, but whitish and pinkish colouration has also been observed. The dark grey porphyritic, mafic rock composition occurs as enclaves within the granite, with phenocrysts having a preferred alignment as the enclosing granite. Also, K-feldspar megacrysts show zoning defined by concentric arrangement of inclusions of biotite relative to the crystal faces. Petrographic study shows the following minerals in order of abundance: K-feldspar, biotite, quartz, and plagioclase, with K-feldspar having a microperthitic intergrowth and biotite crystals aligned in a preferred direction. Evidence such as the crystal shape of K-feldspars, preferred alignment of K-feldspar phenocrysts, and concentric crystallographic arrangements of inclusions of biotite in K-feldspar support a magmatic/phenocrystic origin of K-feldspar megacrysts of Abeokuta granite rather than originating by growing in a solid state as porphyroblasts.

Keywords

  • megacrysts
  • microperthitic
  • K-feldspar
  • zoning
  • porphyroblasts

Ključnebesede

  • vtrošniki
  • mikropertit
  • kalijev glinenec
  • conarna rast
  • porfiroblasti
Open Access

Valuation of Rubber Waste and Dune Sand: Mortar for Construction and Environmental Protection

Published Online: 23 Feb 2022
Page range: -

Abstract

Abstract

The main objective of this study is the recovery of dune sands and rubber waste (powders). The latter constitutes a potential source of several environmental and economic problems.

The objective of this present work is to examine the ability to use dune sand for the preparation of mortars with sufficient physico-mechanical properties to allow them to be used in various building construction applications. The formulation of the mixtures is based on replacing dune sand with powders, at different weight contents: 10 %, 20 %, and 30 %. The quantity of cement is set at 450 g. The results obtained show in the first place that the particle size of the mixture tends to be spread out with a remarkable increase in the fineness modulus, and in the second place the density of the mixture decreases by 6.5 % (for the apparent) and by 10 % (for the absolute), which means the calculation of loads for the resulting mortar must decrease. Porosity has decreased to 20 % and absorption has increased to 30%. The strengths have decreased over 40 % for compressive strength and over 30 % for tensile strength, with an improvement in the relationship between the two strengths.

Keywords

  • Mortar
  • dune sand
  • rubber
  • porosity
  • absorption
  • strength
Open Access

Lateral squeezing effects on cement-slag-bentonite slurry wall performance

Published Online: 02 Mar 2022
Page range: -

Abstract

Abstract

Cement-slag-bentonite slurry walls are self-hardening structures, and they are mainly used to retard contamination transport into the groundwater stream. Whilst permeability of a mixture is an initial criterion in slurry wall design and material selection, long-term performance is mainly influenced by curing ages and stress-state caused by adjacent soil. In this study, the steady-state of effective stresses at 7 days and 28 days of curing age is predicted. The effect of the modulus of horizontal subgrade reaction, interface friction, and transition of the earth pressure from at-rest to the active condition was applied to develop the model. Unlike the quantities that the geostatic model presented, this method gives a slight decrease of stresses after a certain depth, and the trend is in good agreement with trends provided by previous studies. Furthermore, the predicted stresses are then applied to estimate the permeability of the wall at each depth and compare it with those obtained in the laboratory. Finally, predicted effective stresses stay lower than geostatic stress, and the slurry wall consolidation along with the sidewalls’ lateral squeezing leads to keeping the stress state under control.

Keywords

  • cement-slag-bentonite
  • compressibility
  • lateral squeezing
  • permeability
  • slurry wall
Open Access

Hydrocarbon Potential and Biomarker Studies of EE-1 Well, Offshore Eastern Dahomey Basin, SW Nigeria

Published Online: 18 Mar 2022
Page range: -

Abstract

Abstract

The hydrocarbon potential, organic source input, and paleodepositional environment of subsurface sediments from EE-1 well, offshore Eastern Dahomey Basin, were assessed using Rock-Eval pyrolysis and biomarker geochemistry. The total organic carbon (TOC) and soluble organic matter (SOM) in the sediments ranged from 0.96wt% to 8.92wt% and 676.12 ppm to 2883.85 ppm, respectively, indicating adequate to excellent organic richness. The pseudo-Van Krevelen plot classified the sediments as types II and III kerogen, which have the potential to generate both oil and gas. The Tmax and production index (PI) ranged from 422°C to 431°C (average, 426°C) and 0.03 to 0.24, respectively, suggesting low thermal maturity. The presence of C27–C29 steranes, oleanane, and hopane/sterane ratio (1.53/16.11), indicated organic matter from mixed sources with more terrigenous input. Cross plots of Pr/nC17 against Ph/nC18, C35/C31 – C35 homohopane index (0.05 – 0.17) and other related biomarker ratios such as C21/C23 trycyclic terpane ratio (0.33 – 0.82) signified that the sediments were deposited in mixed marine/terrigenous environment under oxic – suboxic conditions. This study has demonstrated that sediments had adequate organic matter with the potential to generate both oil and gas at appropriate thermal maturity.

Keywords

  • hydrocarbon potential
  • biomarker
  • Dahomey Basin
Open Access

Returning Electrostatic Precipitators to the Fe-Ni Production Process

Published Online: 21 Mar 2022
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Abstract

Abstract

The process of frying the Fe-Ni charge in rotary kilns inherently produces large amounts of process dust, which rotary kilns clean out through the use of electro-static precipitators [1].

One kiln contains two sections of electrostatic precipitators as a safety mechanism [1]. Electrodes installed in the sections produce electric fields when electricity passes through them, and ionize the dust.

The timing of the process must be coordinated carefully, and these electrodes are struck with hammers and occasionally shaken, generating quantities of dust which are then collected in a snail dust conveyor, then returned to the production process and recycled. In addition, a smaller amount of dust is derived from the gas chamber, which returns to production without entering the cleaning process in the electro filters. The difference between the two types of dust is their granulation size [1].

We conducted the research during the years from 2017 through 2020, calculating the components of the rotary kiln process. Here, we present a linear equation as a result of the ratio of calcine and electrofilter dust.

Keywords

  • dust
  • calcine
  • electro filter
  • adhesion
  • rotary kiln

Ključnebesede

  • prah
  • žganje
  • elektrofilter
  • adhezija
  • rotacijska peč
Open Access

Determining the Enthalpy of an Fe-Ni Alloy at Various Temperatures Using the ‘STA’ PT 1600 Equipment

Published Online: 21 Mar 2022
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Abstract

Abstract

In this research paper we have determined the enthalpy of the Fe-Ni alloy using the ‘STA’ equipment at the laboratory of the University of Mitrovica “Isa Boletini”, Department of Materials and Metallurgy. The sample for analysis was taken at the Ferronikel plant, whereas the preparation of the sample for analysis on the ‘STA PT 1600’ equipment took place at the laboratory of the University of Mitrovica ‘Isa Boletini’.

The sample of the Fe-Ni alloy analysed was 2–4 cm in size, in the shape of a granule. It contained, 22.55% Ni, 76.51% Fe, and small amounts of other elements [1, 2]. During the analysis of the Fe-Ni alloy, we obtained three enthalpy values under analytical conditions that included a maximum temperature of 800 °C and a minimum temperature of 600 °C; the alloy was exposed to each temperature separately for 45 minutes at each temperature.

The results showed negative enthalpy values during the three scenarios examined and an exothermic process where ΔH<0 [3]. The enthalpy decreases as the system releases heat with an increase in temperature [4].

Keywords

  • STA
  • alloy
  • Fe-Ni
  • enthalpy
  • exothermic process

Ključnebesede

  • STA
  • zlitina
  • Fe-Ni
  • entalpija
  • eksotermni proces
Open Access

Identification of favourable geological formations for the determination of groundwater

Published Online: 25 Sep 2022
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Abstract

Abstract

Clean drinking water supply is a major concern to the population of the urban municipality of Boké, Republic of Guinea. This study is aimed to investigate the favourable geological structure for the accumulation of groundwater in Boké. Apparent resistivity data was collected by using the Schlumberger-type vertical electrical sounding technique. The apparent resistivity values were obtained on a bi-logarithmic scale in which the distances AB/2 were plotted on the abscissa and the resistivities are on the ordinate. It found the number of terrains and their characteristics (resistivity and thickness) in the area and the behaviour of the current in the soil through a curve. The results show that the structures favourable to the accumulation of groundwater were fractured dolerites, cracked shales and cracked or crushed sandstones. The sandstones were the most important in terms of the amount of water. They are located at a depth of more than 100 metres. It was also found that dolerites and shales are located at shallower depths (less than 100 m).

Keywords

  • Groundwater
  • geo-electric method
  • litho-logical section
  • fracture zones
  • Prefecture of Boké

Ključne besede

  • podzemna voda
  • geoelektrična metoda
  • litološki profil
  • razpoklinska območja
  • Prefektura Boké
Open Access

Microstructure of a nickel insert, a special copper alloy, and a cast joint between them

Published Online: 01 Oct 2022
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Abstract

Abstract

This work deals with the characterisation of the micro-structure of a nickel insert, a special copper alloy and the cast joint between them after their use as a glass manufacturing mould. The microstructure was characterised by optical microscopy, scanning electron microscopy and microanalysis by energy dispersive X-ray spectroscopy.

It was found that the nickel insert contained 7 at. % Si and 0.3 at. % Fe. The special copper alloy contains undesirable phases or compounds, including lead, aluminium-based oxides and borides. The borides are either iron-, iron-chromium- or chromium-based with different stoichiometries between metal components and boron. The cast joint between the nickel insert and the special copper alloy has evidence of mixing the two alloys, while only in some areas porosity and oxides prevented the formation of a suitable cast joint. Aluminium-based oxides and some borides could be the cause of the formation of cracks due to their morphology.

Keywords

  • nickel alloy
  • copper alloy
  • microstructure
  • microanalysis

Ključne besede

  • nikljeva zlitina
  • bakrova zlitina
  • mikrostruktura
  • mikroanaliza
Open Access

Solid Mineral Potential and Geothermal Energy Reserve of Northern Basement Complex, Nigeria

Published Online: 23 Oct 2022
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Abstract

Abstract

The spectral analysis of aeromagnetic data over the study area (Northern basement complex, Nigeria) revealed the existence of two major source depths. The second segment of the spectrum layer shows shallow sources ranging in depth from 0.135 km to 0.201 km, with an average depth of 0.140 km. The depth to the basement or deeper source ranges between 1.655 km and 2.021 km, with an average depth of 1.882 km. The Precambrian basement is reflected in the deeper sources, beginning with the first segment of the power spectrum. Structural and topographic relief of the basement surface, lateral differences in basement susceptibilities, and intra-basement features such as faults and fractures contribute to the variation in basement composition. The mean thickness of sediments in the study area is represented by the D2 values obtained from the spectral plots. The depths revealed by this study appears to be reasonable and consistent with previous researchers’ findings. Tectonically active regions have a major impact on heat flows. The average heat flow in thermally normal continental regions is reported to be above 60 mW/m2. Values between 80 and 100 mW/m2 indicate a good geothermal source; values in excess of about 80–100 mW/m2 indicate anomalous geothermal conditions.

Keywords

  • 3-D Euler deconvolution
  • spectral inversion
  • magnetic basement depth
  • linear features
  • Nigeria

Ključne besede

  • 3-D Eulerjeva dekonvolucija
  • spektralna inverzija
  • globina magnetne podlage
  • linearne strukture
  • Nigerija
Open Access

Determination of material quality by methods of thermal analysis

Published Online: 07 Nov 2022
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Abstract

Abstract

Cast aluminium alloys are commonly used in the automotive industry for casting applications. There are both primary and secondary/recycled aluminium alloys in the market, which differ in price and quality. In this study, the effect of alloy quality on solidification, microstructure and mechanical properties was investigated. The comparison of properties was carried out in the as-cast condition and in the heat-treated condition. The influence of alloy quality on solidification was analysed by simple thermal analysis and differential scanning calorimetry, and thermodynamic simulations. The basic mechanical properties analysed were tensile strength, yield strength, elongation, and hardness. The microstructural differences were analysed using a light microscope. The Mn:Fe ratio, which is strongly influenced by the alloy quality, was found to have a pronounced effect on the mechanical properties, while magnesium together with silicon hardens the aluminium matrix during heat treatment, which significantly increases the mechanical properties. This research proved that thermal analysis methods can give us a necessary and important indication of the quality of the alloys used.

Keywords

  • Alloy quality
  • casting alloys
  • thermal analysis
  • solidification
  • microstructure
  • mechanical properties

Ključne besede

  • kakovost zlitin
  • livarske zlitine
  • termična analiza
  • strjevanje
  • mikrostruktura
  • mehanske lastnosti
Open Access

Rare Earth Element Geochemistry and Abundances in Syenites and Charnockitic Rocks of Selected Locations within Southwestern Nigeria

Published Online: 18 Nov 2022
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Abstract

Abstract

Rare earth elements (REE) are critical metals widely used in modern technology. There is an increased demand for these elements which has necessitated additional exploration. The REE geochemistry of syenites and charnockitic rocks from selected locations within southwestern Nigeria were studied to determine their concentrations, distribution patterns, and mineralisation potential to deduce if they can be economically exploited. Mineralogical studies were carried out using scanning electron microscopy (SEM). Ten rock samples including five syenites and five charnockites were analysed for their elemental composition using inductively coupled plasma – mass spectrometry (ICP-MS). The REE-bearing minerals identified from the SEM analysis include apatite and monazite. The fractionation ratio (La/Yb)N ranged from 29.36 to 48.75 for the syenites and from 24.43 to 48.29 for the charnockites, indicating magmatic differentiation. Total REE (∑REE) in the syenites (342–675 ppm) and charnockites (220–802 ppm) suggests that they are enriched with respect to REE but the REE concentration in the rocks of the study area had very low ∑REE compared to the REE contents of the rocks where they have been mined and may therefore not be economically viable.

Keywords

  • rare earth elements
  • syenites
  • charnockites
  • abundances
  • fractionation

Ključne besede

  • elementi redkih zemelj
  • sieniti
  • čarnokiti
  • vsebnost
  • frakcionacija

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