Rivista e Edizione

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Volume 29 (2021): Edizione 48 (June 2021)

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Special Number

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Dettagli della rivista
Formato
Rivista
eISSN
1338-0532
Pubblicato per la prima volta
03 Mar 2011
Periodo di pubblicazione
2 volte all'anno
Lingue
Inglese

Cerca

Volume 29 (2021): Edizione 48 (June 2021)

Dettagli della rivista
Formato
Rivista
eISSN
1338-0532
Pubblicato per la prima volta
03 Mar 2011
Periodo di pubblicazione
2 volte all'anno
Lingue
Inglese

Cerca

17 Articoli
Accesso libero

Importance of Recycling the Waste-Cables Containing Copper and PVC

Pubblicato online: 05 Aug 2021
Pagine: 1 - 21

Astratto

Abstract

Urbanization, development of economy, increasing population and improved living standards and lifestyle have caused a sharp growth in waste. Inappropriate or inefficient waste disposal techniques can cause serious air, soil, and groundwater pollution, which subsequently can negatively affect the urban environment and threaten the health of residents. The goal of waste management is to move to a circular economy in which waste does not exist. If there is no possible way to reduce or reuse waste, the best solution is recycling it. Recycling brings abundant benefits on the economic and ecological levels levels, and helps reduce overall human health risk of adverse impacts. Recycling of the waste-cables which contain PVC and copper replaces the production of virgin PVC and mining of copper from copper ore, it reduces landfill solid waste pressures, saves energy and water sources, reduces emissions to environment, and also reduces negative impacts from improperly dispose of waste, etc. This paper presents an overview of recycling techniques for the waste-cables containing copper as a core and polyvinyl chloride as an insulating layer or sheath. It also lists advantages and disadvantages of these techniques and importance of recycling this type of waste.

Parole chiave

  • Waste-cables
  • recycling
  • copper
  • PVC
  • circular economy
Accesso libero

Utilization of Waste-Based Sorbents for Removal of Pharmaceuticals from Water: A Review

Pubblicato online: 05 Aug 2021
Pagine: 22 - 36

Astratto

Abstract

Nowadays, the water contamination which is due to pharmaceuticals is increasing and alarming. The pharmaceuticals in water are very hazardous and toxic not only for the human life but also for environment. One of the promising methods of removing pharmaceuticals from the contaminated water is adsorption. Agricultural and industrial wastes or by-products can be used as low-cost adsorbents for pharmaceuticals removal. Low-cost adsorbents provide particular economic and environmental advantages. This paper presents an overview of utilizing of the waste-based adsorbents (mainly spent coffee grounds) for the removal of pharmaceuticals from water.

Parole chiave

  • Pharmaceuticals
  • tetracycline
  • adsorption
  • waste utilization
  • spent coffee grounds
Accesso libero

Preliminary Study Into the Decolorization of Selected Dyes By the Ozone Application

Pubblicato online: 05 Aug 2021
Pagine: 37 - 44

Astratto

Abstract

Synthetic dyes widely used in many kinds of industry affect the colour of wastewater when released to environment due to insufficient treatment in typical sewage treatment plants. Only a small dose of those dyes may significantly affect colour of water and, according to the chemical composition, may pose risks to wildlife and humans. In the research described in this study, decolorization of three various dyes was investigated. Since colour removal of Congo Red such as Methylene blue using ozone have been reported by several authors, and the literature on Naphthol Green B is rather limited, in the present study we compare the decolorization rate of CR, MB and NGB. The colour removal occurred quickly and more than 90% of colour reduction was achieved within 3-6 minutes throughout all tested pH of the solution.

Parole chiave

  • Dyes
  • decolorization
  • ozone
  • AOPs
  • water treatment
Accesso libero

Preliminary Bioleaching Experiment of E-Waste

Pubblicato online: 05 Aug 2021
Pagine: 45 - 54

Astratto

Abstract

Nowadays, we can hardly imagine our life without the achievements of modern technology, such as refrigerators, televisions, computers, or smartphones. Producers are pushing consumers to buy newer, more modern appliances instead of repairing the original ones. However, all the devices represent a huge amount of waste. E-waste is one of the fastest growing types of waste, and only less than a half of it is recycled. Its disposal poses a great challenge for the population and constitutes a huge burden for the environment. In the research described in this article, we focused on individual techniques for metals recovery from e-waste. In the experimental part, we deal with the recycling of electronic waste by bioleaching, using microorganisms Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Compared to conventional techniques, bioleaching is a more environmentally friendly and economical alternative of metals recovery from e-waste.

Parole chiave

  • Bioleaching
  • electronic waste
  • microorganisms
  • printed circuit boards
Accesso libero

Determination of Timing Parameters of Dust Clouds Explosion in Dependence on the Size of the Vessel Volume

Pubblicato online: 05 Aug 2021
Pagine: 55 - 64

Astratto

Abstract

EN 14034 standard defines the requirements for igniter, to determine the properties of dust clouds. The standard specifies the conditions for occurrence of explosions of dust clouds. According to the standard, equipment with a volume of 1m3 and 20L can be used to determine the explosion parameters of dispersed dusts. The equipment has the time parameters of dispersing and the ignition system defined in the Standard. Experimental determination of time parameters is required for a different chamber volume. The article therefore deals with the determination of parameters for dispersing system in the 291 litre chamber. Determination of igniter delay was performed on the base of setting the time relay. Activation of pressurised air flow was determined by calculation, and it was subsequently experimentally verified in laboratory conditions. A video camera recording was selected for measuring the rate of nitrocellulose ignition from the resistance wire. The result of this study is determination of the igniter timing in dependence of the explosion chamber volume. The time delay of the nitrocellulose igniter is 320 ms.

Parole chiave

  • Nitrocellulose
  • ignition
  • resistance wire
  • dust clouds explosion
  • timing parameters
Accesso libero

Fire Characteristics of Polyethylene Dust

Pubblicato online: 05 Aug 2021
Pagine: 65 - 72

Astratto

Abstract

Dust is a product or by-product in many industries. To ensure effective measures of explosion prevention, it is necessary to know the fire properties of dispersed and settled dust. These parameters cannot be calculated, but can be determined on the base of measurements in standard equipment. The article deals with the measurement of fire properties of polyethylene. The values of the minimum ignition temperature of settled and dispersed dust (MIT) and the values of explosion characteristics of polyethylene dust cloud lower explosion limit (LEL), maximum pressure Pmax and maximum rate of pressure rise (dp/dt)max were measured. The measurements were performed on the equipment according to the STN EN 80079-20-2: 2016 Standard Explosive atmospheres - Part 20-2: Material characteristics - Combustible dust test methods and according to the STN EN 14034 + A1: 2011 Standard Determination of explosion characteristics of dust clouds. The MIT of the settled dust was not determined (the sample melted), the MIT of the dispersed dust was 435 °C. The maximum explosion pressure Pmax reached 7.0 bar, and the maximum rate of pressure rise dP/dt was 37.5 bar.s−1.

Parole chiave

  • Fire characteristic
  • dust cloud
  • dust explosion
  • polyethylene
Accesso libero

The Use of Red Mud and Black Nickel Mud in Sorption of 3,5-Dichlorophenol

Pubblicato online: 05 Aug 2021
Pagine: 73 - 80

Astratto

Abstract

This article discusses the use of alternative inexpensive adsorbents – wastes from the metal production - red mud (RM) and black nickel mud (BNM) and their sorption efficiency in 3,5-dichlorophenol removal. Chlorophenols are organic compounds consisting of a benzene ring, OH groups and chlorine atoms. The effects of adsorbent dose, contact time, and temperature on sorption process were monitored. The results showed that the optimal conditions to achieve the highest sorption efficiency of 3,5-dichlorophenol were reached with the use of black nickel mud at the amount (2.0 g), sorption time (1 hour) and at increased temperature (45 °C). The sorption efficiency under these conditions was 87.99 %. With increasing sorption time, the sorption efficiency decreased and desorption occurred. The same behaviour was observed using red mud of the same amount (2.0 g) at the same temperature (45 °C); however, after 1 hour, sorption efficiency was slightly reduced (85.16 %) compared to black nickel mud. Anyway, both of used materials are suitable for the use as alternative sorbents of 3,5-dichlorophenol under suitable conditions.

Parole chiave

  • Red mud
  • black nickel mud
  • 3,5-dichlorophenol
  • sorption efficiency
Accesso libero

Fire Growth Rate Index as a Key Fire Characteristic of Electrical Cables

Pubblicato online: 05 Aug 2021
Pagine: 81 - 90

Astratto

Abstract

This study deals with the Fire Growth Rate Index (FIGRA) as a key fire characteristic of electrical cables (determined by a cone calorimeter) that allows to estimate their reaction to fire class. Three power (supply) electrical cables (reaction to fire class B2ca) were tested by a cone calorimeter using different heat fluxes of 20, 30, 40 a 50 kW·m−2. The cables were three-wire (cross-section of each wire was 1.5 mm2) with a nominal voltage of 0.6 kV (alternating current), resp. 1 kV (direct current). The cable sheaths were made of an ethylene copolymer filled with aluminum hydroxide. The beddings were made of an ethylene copolymer filled with a mixture of aluminum hydroxide and calcium carbonate. The conductor insulations of one electrical cable were made of crosslinked polyethylene and the conductor insulations of the other two electrical cables were made of an ethylene copolymer filled with aluminum hydroxide. FIGRA was determined per unit length and unit area of electrical cables. FIGRA increased with increasing heat flux. At a heat flux of 50 kW·m−2, all the electric cables examined showed a very similar FIGRA (from 0.19 to 0.21 kW·m−1·s−1 and 18.4 to 21.2 kW·m−1·s−1, respectively). Conversely, at a heat flux of 20 kW·m−2, the investigated cables showed greater FIGRA variance (in the range of 0.11 to 0.16 kW·m−1·s−1 or 10.8 to 16.2 kW·m−1·s−1).

Parole chiave

  • Cone calorimeter
  • heat release rate
  • electrical cable
  • fire growth rate index
  • reaction to fire class
Accesso libero

Heterogeneous Fenton-Like Oxidation of Methylene Blue Using Alternative Catalysts

Pubblicato online: 05 Aug 2021
Pagine: 91 - 97

Astratto

Abstract

The usage of the low-cost catalysts for methylene blue removal from wastewater was investigated. Heterogeneous Fenton-like process consists of the use of a hydrogen peroxide solution, and an iron-rich catalyst, red mud and black nickel mud were used for that purpose. The factors such as the catalyst dose and the hydrogen peroxide solution volume were monitored. The results of experiments showed that the degradation of methylene blue dye in Fenton-like oxidation process using selected catalysts can be described by a pseudo-second-order kinetic model. The highest dye removal efficiency (87.15 %) was achieved using the black nickel mud catalyst after 30 minutes of reaction.

Parole chiave

  • Fenton-like process
  • red mud
  • black nickel mud
  • methylene blue
Accesso libero

Degradation of Electrical Wire Sheaths By UV Radiation

Pubblicato online: 05 Aug 2021
Pagine: 98 - 104

Astratto

Abstract

The objective of this manuscript is to report experimental results concerning the effect of accelerated UV-C ageing on the properties of samples of halogen-free sheaths of power cables. Two samples of halogen free sheaths of power cables of Vuki a.s. CHKE-V E30 and Nexans 273-K3 HERP/CWB/2SZH were studied after exposition on the UV-C radiation in a closed chamber. Degradation was monitored by the change in infrared spectra of the samples, their hardness and colour. Based on the observed changes, it can be argued that exposure to the UVC radiation affects the observed properties on the surface of the studied samples. All the observed changes were due to the rupture of the bonds towing to the absorption of UV-C radiation.

Parole chiave

  • Wire sheath
  • UV-C degradation
  • infrared spectra
  • hardness
  • decolouration
Accesso libero

Study Into Dynamic Behaviour of the Methylene Blue Adsorption on Activated Carbon

Pubblicato online: 05 Aug 2021
Pagine: 105 - 113

Astratto

Abstract

This paper presents a study into dynamic behaviour of the methylene blue adsorption (MB) on activated carbon. Effect of four parameters were studied: effect of the adsorbent dosage, effect of contact time, effect of pH, and effect of the initial concentration of methylene blue. The adsorption kinetic data were modelled using the pseudo-first and pseudo-second orders. Results show that, based on the experimental data, the pseudo-second order could be considered satisfactory. Thermodynamic parameters proved that adsorption of dye was spontaneous owing to increase in temperature and endothermic nature. Taguchi method was applied to determine the optimum conditions for removal of methylene blue by activated carbon. The optimum conditions were found to be pH = 7, contact time 60 min, initial concentration of MB 4 mg/L.

Parole chiave

  • Adsorption
  • dye removal
  • Taguchi
  • kinetics
  • thermodynamic
Accesso libero

Initiation Parameters of Granulated Synthetic Polymers

Pubblicato online: 05 Aug 2021
Pagine: 114 - 122

Astratto

Abstract

Polymeric materials, which are currently very often used in various industries, are often transported and stored in the form of granules before processing. This method has several advantages, but in most studies the test samples are modified to different shapes and dimensions. This paper is therefore focused on the initiation of selected granular plastics. Samples of five polymeric materials were exposed to an external heat flux from 20 kW.m−2 to 40 kW.m−2. A spark initiator was used to ignite the released gaseous products of thermal decomposition of the polymer sample. FTP (flow-time product) method was applied to the obtained parameter - time to ignition, from which other initiation parameters were determined. The critical heat flux was determined in the range of 5.0 kW.m−2 - 11.8 kW.m−2. Despite the relatively small thickness (4 mm), the samples behaved as thermally thick. During the measurement, thin surface layer melted, and the rest of the polymer remained in its original granulated form. Ignition temperatures were calculated according to the Stefan-Boltzmann’s law between 273 °C - 402 °C.

Parole chiave

  • Critical heat flux
  • flow-time product
  • initiation
  • initiation temperature
Accesso libero

Potential Applications of Nanomaterials in Wastewater Treatment

Pubblicato online: 05 Aug 2021
Pagine: 123 - 130

Astratto

Abstract

Over the last few decades, nanotechnologies have gained a great deal of attention, and various nanomaterials and techniques have been developed for water remediation. This study deals with the adsorption of Naphthol green B onto the magnetite nanoparticles synthetized by the coprecipitation method at the laboratory temperature. According to the obtained results, the sorption process is obvious only at the acidic condition when the pH of solution decreases to pH level 3. According to nonlinear fit of experimental data, the sorption of the Naphthol green B onto magnetite nanoparticles is assumed as multilayer, while the Freundlich model fits better (96.158 %) than the Langmuir model does (55.941 %).

Parole chiave

  • Adsorption
  • magnetite
  • FeO
  • dyes
  • naphthol green B
Accesso libero

Study Into the Changes in Soil Organic Matter, Caused By Laboratory Simulated Fires in Four Slovak Soils 1. UV-VIS Spectrum Analysis

Pubblicato online: 05 Aug 2021
Pagine: 131 - 142

Astratto

Abstract

The study was focused on describing ultraviolet-visible spectra of the humic substances, humic acids and fulvic acids isolated from four Slovak soils. The samples were heated in a laboratory furnace, to simulate soil behaviour during fires. The absorbances at the wavelengths corresponding to the selected chromophores and specific wavelength for groups of substances were compared. Analysis of the UV -VIS spectra of the extracted humic substances may indicate the directions of interest in the changes in soil organic matter, along with the changes in external conditions, such as natural fires.

Parole chiave

  • Fire
  • Humic substances (HS)
  • Humic acid (HA)
  • Fulvic acid (FA)
  • UV-VIS spectrophotometry
Accesso libero

Influence of Explosion Chamber Shape on Timing Parameters of Disperser

Pubblicato online: 05 Aug 2021
Pagine: 143 - 148

Astratto

Abstract

A standardized device with a volume of 1 m3 or 20 L is used to determine explosion parameters. An explosion chamber where explosion takes place is of a spherical or cylindrical shape that suits the shape of a cubic container. In the case of a cylindrical vessel, the diameter and depth of the vessel are 1: 1. In this case, it is a spherical vessel with a volume of 365 liters. Time parameters of the disperser in the spherical vessel are compared with those of a truncated spherical vessel with a volume of 291 liters. Comparison of the measurement results showed that the optimal delay time of the explosion chamber with a volume of 291 liters is 290 ms, while the delay time of the explosion chamber with a volume of 365 liters is 350 ms.

Parole chiave

  • Explosion chamber
  • dispersed dust
  • disperser
  • timing parameters
Accesso libero

Infuence of Selected Pharmaceuticals on Biogas Production in Mesophilic Anaerobic Fermentation

Pubblicato online: 05 Aug 2021
Pagine: 149 - 157

Astratto

Abstract

This article deals with pharmaceutical compounds as micropollutants in anaerobic digestion of sludge from waste water treatment plant (WWTP). Part of the work included the research into presence of pharmaceuticals in different types of waters. Description of anaerobic fermentation process is also important in terms of optimal conditions. The practical aim of the investigation was preparation of a model of anaerobic fermentation of sewage sludge, where influence of pharmaceuticals on mesophilic anaerobic digestion was monitored. Wash out of micropollutants from sludge in big semicontinuous anaerobic reactors was running since October 2013. The resulting non-adapted sludge from mesophilic reactor was used since March 2014 for pharmaceuticals tests in half-a-litre glass bottles with a septum cap. The compounds of interest were diclofenac, tramadol, ibuprofen, carbamazepine and amoxicillin and their concentration in the tested sludge was 10 μg/L and 500 μg/L. The results showed that pharmaceuticals have different influence on the amount of produced biogas even if they are from the same therapeutic group. In the low concentration, the inhibition was present for diclofenac, carbamazepine and amoxicillin, at the high concentration, while diclofenac showed almost no influence. Other compounds caused a stimulative effect on the process. The mixture of all pharmaceuticals of interest in low concentration was stimulative at first, while it was inhibotory since mid-time of the test.

Parole chiave

  • Pharmaceuticals
  • micropollutants
  • anaerobic fermentation
  • sewage sludge
Accesso libero

Electrochemical Recovery of Silver Using a Simple Cell

Pubblicato online: 05 Aug 2021
Pagine: 158 - 166

Astratto

Abstract

The amount of generated e-waste during the last decades has been steadily raising to the point at which it is highly desirable to obtain the precious metals by recycling the e-waste without the need of exploiting the environment. The rapid development of technology, steep growth of modern facilities with user-friendly electronical devices and a stiff competition between manufacturers are among the main reasons for decreasing the life span of such devices, and subsequently end up as an obsolete waste product. Rapid industrialization and urbanization have also caused many environmental problems, e.g. heavy metal contamination. Silver is one of the precious metals with exceptionally high industrial applications, which makes it an area of research of high interest. Demand for silver continues to grow with progress in the industrialized world, while the world reserves of high-quality silver ores are declining. Although, there are large stocks of low and lean quality silver ores still to be mined, the main goal of this article is to provide a simple, effective and eco-friendly method of silver recovery from e-waste, e.g. electrical circuit breakers using an electrochemical cell. After 20.75 days of the experiment, 1481.5 grams of silver contacts were processed with a final yield of 61.41 % grams of silver dendrite crystals (99.9 % purity).

Parole chiave

  • Electrochemical recovery
  • electrolytic cell
  • silver
  • circuit breakers contacts
17 Articoli
Accesso libero

Importance of Recycling the Waste-Cables Containing Copper and PVC

Pubblicato online: 05 Aug 2021
Pagine: 1 - 21

Astratto

Abstract

Urbanization, development of economy, increasing population and improved living standards and lifestyle have caused a sharp growth in waste. Inappropriate or inefficient waste disposal techniques can cause serious air, soil, and groundwater pollution, which subsequently can negatively affect the urban environment and threaten the health of residents. The goal of waste management is to move to a circular economy in which waste does not exist. If there is no possible way to reduce or reuse waste, the best solution is recycling it. Recycling brings abundant benefits on the economic and ecological levels levels, and helps reduce overall human health risk of adverse impacts. Recycling of the waste-cables which contain PVC and copper replaces the production of virgin PVC and mining of copper from copper ore, it reduces landfill solid waste pressures, saves energy and water sources, reduces emissions to environment, and also reduces negative impacts from improperly dispose of waste, etc. This paper presents an overview of recycling techniques for the waste-cables containing copper as a core and polyvinyl chloride as an insulating layer or sheath. It also lists advantages and disadvantages of these techniques and importance of recycling this type of waste.

Parole chiave

  • Waste-cables
  • recycling
  • copper
  • PVC
  • circular economy
Accesso libero

Utilization of Waste-Based Sorbents for Removal of Pharmaceuticals from Water: A Review

Pubblicato online: 05 Aug 2021
Pagine: 22 - 36

Astratto

Abstract

Nowadays, the water contamination which is due to pharmaceuticals is increasing and alarming. The pharmaceuticals in water are very hazardous and toxic not only for the human life but also for environment. One of the promising methods of removing pharmaceuticals from the contaminated water is adsorption. Agricultural and industrial wastes or by-products can be used as low-cost adsorbents for pharmaceuticals removal. Low-cost adsorbents provide particular economic and environmental advantages. This paper presents an overview of utilizing of the waste-based adsorbents (mainly spent coffee grounds) for the removal of pharmaceuticals from water.

Parole chiave

  • Pharmaceuticals
  • tetracycline
  • adsorption
  • waste utilization
  • spent coffee grounds
Accesso libero

Preliminary Study Into the Decolorization of Selected Dyes By the Ozone Application

Pubblicato online: 05 Aug 2021
Pagine: 37 - 44

Astratto

Abstract

Synthetic dyes widely used in many kinds of industry affect the colour of wastewater when released to environment due to insufficient treatment in typical sewage treatment plants. Only a small dose of those dyes may significantly affect colour of water and, according to the chemical composition, may pose risks to wildlife and humans. In the research described in this study, decolorization of three various dyes was investigated. Since colour removal of Congo Red such as Methylene blue using ozone have been reported by several authors, and the literature on Naphthol Green B is rather limited, in the present study we compare the decolorization rate of CR, MB and NGB. The colour removal occurred quickly and more than 90% of colour reduction was achieved within 3-6 minutes throughout all tested pH of the solution.

Parole chiave

  • Dyes
  • decolorization
  • ozone
  • AOPs
  • water treatment
Accesso libero

Preliminary Bioleaching Experiment of E-Waste

Pubblicato online: 05 Aug 2021
Pagine: 45 - 54

Astratto

Abstract

Nowadays, we can hardly imagine our life without the achievements of modern technology, such as refrigerators, televisions, computers, or smartphones. Producers are pushing consumers to buy newer, more modern appliances instead of repairing the original ones. However, all the devices represent a huge amount of waste. E-waste is one of the fastest growing types of waste, and only less than a half of it is recycled. Its disposal poses a great challenge for the population and constitutes a huge burden for the environment. In the research described in this article, we focused on individual techniques for metals recovery from e-waste. In the experimental part, we deal with the recycling of electronic waste by bioleaching, using microorganisms Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Compared to conventional techniques, bioleaching is a more environmentally friendly and economical alternative of metals recovery from e-waste.

Parole chiave

  • Bioleaching
  • electronic waste
  • microorganisms
  • printed circuit boards
Accesso libero

Determination of Timing Parameters of Dust Clouds Explosion in Dependence on the Size of the Vessel Volume

Pubblicato online: 05 Aug 2021
Pagine: 55 - 64

Astratto

Abstract

EN 14034 standard defines the requirements for igniter, to determine the properties of dust clouds. The standard specifies the conditions for occurrence of explosions of dust clouds. According to the standard, equipment with a volume of 1m3 and 20L can be used to determine the explosion parameters of dispersed dusts. The equipment has the time parameters of dispersing and the ignition system defined in the Standard. Experimental determination of time parameters is required for a different chamber volume. The article therefore deals with the determination of parameters for dispersing system in the 291 litre chamber. Determination of igniter delay was performed on the base of setting the time relay. Activation of pressurised air flow was determined by calculation, and it was subsequently experimentally verified in laboratory conditions. A video camera recording was selected for measuring the rate of nitrocellulose ignition from the resistance wire. The result of this study is determination of the igniter timing in dependence of the explosion chamber volume. The time delay of the nitrocellulose igniter is 320 ms.

Parole chiave

  • Nitrocellulose
  • ignition
  • resistance wire
  • dust clouds explosion
  • timing parameters
Accesso libero

Fire Characteristics of Polyethylene Dust

Pubblicato online: 05 Aug 2021
Pagine: 65 - 72

Astratto

Abstract

Dust is a product or by-product in many industries. To ensure effective measures of explosion prevention, it is necessary to know the fire properties of dispersed and settled dust. These parameters cannot be calculated, but can be determined on the base of measurements in standard equipment. The article deals with the measurement of fire properties of polyethylene. The values of the minimum ignition temperature of settled and dispersed dust (MIT) and the values of explosion characteristics of polyethylene dust cloud lower explosion limit (LEL), maximum pressure Pmax and maximum rate of pressure rise (dp/dt)max were measured. The measurements were performed on the equipment according to the STN EN 80079-20-2: 2016 Standard Explosive atmospheres - Part 20-2: Material characteristics - Combustible dust test methods and according to the STN EN 14034 + A1: 2011 Standard Determination of explosion characteristics of dust clouds. The MIT of the settled dust was not determined (the sample melted), the MIT of the dispersed dust was 435 °C. The maximum explosion pressure Pmax reached 7.0 bar, and the maximum rate of pressure rise dP/dt was 37.5 bar.s−1.

Parole chiave

  • Fire characteristic
  • dust cloud
  • dust explosion
  • polyethylene
Accesso libero

The Use of Red Mud and Black Nickel Mud in Sorption of 3,5-Dichlorophenol

Pubblicato online: 05 Aug 2021
Pagine: 73 - 80

Astratto

Abstract

This article discusses the use of alternative inexpensive adsorbents – wastes from the metal production - red mud (RM) and black nickel mud (BNM) and their sorption efficiency in 3,5-dichlorophenol removal. Chlorophenols are organic compounds consisting of a benzene ring, OH groups and chlorine atoms. The effects of adsorbent dose, contact time, and temperature on sorption process were monitored. The results showed that the optimal conditions to achieve the highest sorption efficiency of 3,5-dichlorophenol were reached with the use of black nickel mud at the amount (2.0 g), sorption time (1 hour) and at increased temperature (45 °C). The sorption efficiency under these conditions was 87.99 %. With increasing sorption time, the sorption efficiency decreased and desorption occurred. The same behaviour was observed using red mud of the same amount (2.0 g) at the same temperature (45 °C); however, after 1 hour, sorption efficiency was slightly reduced (85.16 %) compared to black nickel mud. Anyway, both of used materials are suitable for the use as alternative sorbents of 3,5-dichlorophenol under suitable conditions.

Parole chiave

  • Red mud
  • black nickel mud
  • 3,5-dichlorophenol
  • sorption efficiency
Accesso libero

Fire Growth Rate Index as a Key Fire Characteristic of Electrical Cables

Pubblicato online: 05 Aug 2021
Pagine: 81 - 90

Astratto

Abstract

This study deals with the Fire Growth Rate Index (FIGRA) as a key fire characteristic of electrical cables (determined by a cone calorimeter) that allows to estimate their reaction to fire class. Three power (supply) electrical cables (reaction to fire class B2ca) were tested by a cone calorimeter using different heat fluxes of 20, 30, 40 a 50 kW·m−2. The cables were three-wire (cross-section of each wire was 1.5 mm2) with a nominal voltage of 0.6 kV (alternating current), resp. 1 kV (direct current). The cable sheaths were made of an ethylene copolymer filled with aluminum hydroxide. The beddings were made of an ethylene copolymer filled with a mixture of aluminum hydroxide and calcium carbonate. The conductor insulations of one electrical cable were made of crosslinked polyethylene and the conductor insulations of the other two electrical cables were made of an ethylene copolymer filled with aluminum hydroxide. FIGRA was determined per unit length and unit area of electrical cables. FIGRA increased with increasing heat flux. At a heat flux of 50 kW·m−2, all the electric cables examined showed a very similar FIGRA (from 0.19 to 0.21 kW·m−1·s−1 and 18.4 to 21.2 kW·m−1·s−1, respectively). Conversely, at a heat flux of 20 kW·m−2, the investigated cables showed greater FIGRA variance (in the range of 0.11 to 0.16 kW·m−1·s−1 or 10.8 to 16.2 kW·m−1·s−1).

Parole chiave

  • Cone calorimeter
  • heat release rate
  • electrical cable
  • fire growth rate index
  • reaction to fire class
Accesso libero

Heterogeneous Fenton-Like Oxidation of Methylene Blue Using Alternative Catalysts

Pubblicato online: 05 Aug 2021
Pagine: 91 - 97

Astratto

Abstract

The usage of the low-cost catalysts for methylene blue removal from wastewater was investigated. Heterogeneous Fenton-like process consists of the use of a hydrogen peroxide solution, and an iron-rich catalyst, red mud and black nickel mud were used for that purpose. The factors such as the catalyst dose and the hydrogen peroxide solution volume were monitored. The results of experiments showed that the degradation of methylene blue dye in Fenton-like oxidation process using selected catalysts can be described by a pseudo-second-order kinetic model. The highest dye removal efficiency (87.15 %) was achieved using the black nickel mud catalyst after 30 minutes of reaction.

Parole chiave

  • Fenton-like process
  • red mud
  • black nickel mud
  • methylene blue
Accesso libero

Degradation of Electrical Wire Sheaths By UV Radiation

Pubblicato online: 05 Aug 2021
Pagine: 98 - 104

Astratto

Abstract

The objective of this manuscript is to report experimental results concerning the effect of accelerated UV-C ageing on the properties of samples of halogen-free sheaths of power cables. Two samples of halogen free sheaths of power cables of Vuki a.s. CHKE-V E30 and Nexans 273-K3 HERP/CWB/2SZH were studied after exposition on the UV-C radiation in a closed chamber. Degradation was monitored by the change in infrared spectra of the samples, their hardness and colour. Based on the observed changes, it can be argued that exposure to the UVC radiation affects the observed properties on the surface of the studied samples. All the observed changes were due to the rupture of the bonds towing to the absorption of UV-C radiation.

Parole chiave

  • Wire sheath
  • UV-C degradation
  • infrared spectra
  • hardness
  • decolouration
Accesso libero

Study Into Dynamic Behaviour of the Methylene Blue Adsorption on Activated Carbon

Pubblicato online: 05 Aug 2021
Pagine: 105 - 113

Astratto

Abstract

This paper presents a study into dynamic behaviour of the methylene blue adsorption (MB) on activated carbon. Effect of four parameters were studied: effect of the adsorbent dosage, effect of contact time, effect of pH, and effect of the initial concentration of methylene blue. The adsorption kinetic data were modelled using the pseudo-first and pseudo-second orders. Results show that, based on the experimental data, the pseudo-second order could be considered satisfactory. Thermodynamic parameters proved that adsorption of dye was spontaneous owing to increase in temperature and endothermic nature. Taguchi method was applied to determine the optimum conditions for removal of methylene blue by activated carbon. The optimum conditions were found to be pH = 7, contact time 60 min, initial concentration of MB 4 mg/L.

Parole chiave

  • Adsorption
  • dye removal
  • Taguchi
  • kinetics
  • thermodynamic
Accesso libero

Initiation Parameters of Granulated Synthetic Polymers

Pubblicato online: 05 Aug 2021
Pagine: 114 - 122

Astratto

Abstract

Polymeric materials, which are currently very often used in various industries, are often transported and stored in the form of granules before processing. This method has several advantages, but in most studies the test samples are modified to different shapes and dimensions. This paper is therefore focused on the initiation of selected granular plastics. Samples of five polymeric materials were exposed to an external heat flux from 20 kW.m−2 to 40 kW.m−2. A spark initiator was used to ignite the released gaseous products of thermal decomposition of the polymer sample. FTP (flow-time product) method was applied to the obtained parameter - time to ignition, from which other initiation parameters were determined. The critical heat flux was determined in the range of 5.0 kW.m−2 - 11.8 kW.m−2. Despite the relatively small thickness (4 mm), the samples behaved as thermally thick. During the measurement, thin surface layer melted, and the rest of the polymer remained in its original granulated form. Ignition temperatures were calculated according to the Stefan-Boltzmann’s law between 273 °C - 402 °C.

Parole chiave

  • Critical heat flux
  • flow-time product
  • initiation
  • initiation temperature
Accesso libero

Potential Applications of Nanomaterials in Wastewater Treatment

Pubblicato online: 05 Aug 2021
Pagine: 123 - 130

Astratto

Abstract

Over the last few decades, nanotechnologies have gained a great deal of attention, and various nanomaterials and techniques have been developed for water remediation. This study deals with the adsorption of Naphthol green B onto the magnetite nanoparticles synthetized by the coprecipitation method at the laboratory temperature. According to the obtained results, the sorption process is obvious only at the acidic condition when the pH of solution decreases to pH level 3. According to nonlinear fit of experimental data, the sorption of the Naphthol green B onto magnetite nanoparticles is assumed as multilayer, while the Freundlich model fits better (96.158 %) than the Langmuir model does (55.941 %).

Parole chiave

  • Adsorption
  • magnetite
  • FeO
  • dyes
  • naphthol green B
Accesso libero

Study Into the Changes in Soil Organic Matter, Caused By Laboratory Simulated Fires in Four Slovak Soils 1. UV-VIS Spectrum Analysis

Pubblicato online: 05 Aug 2021
Pagine: 131 - 142

Astratto

Abstract

The study was focused on describing ultraviolet-visible spectra of the humic substances, humic acids and fulvic acids isolated from four Slovak soils. The samples were heated in a laboratory furnace, to simulate soil behaviour during fires. The absorbances at the wavelengths corresponding to the selected chromophores and specific wavelength for groups of substances were compared. Analysis of the UV -VIS spectra of the extracted humic substances may indicate the directions of interest in the changes in soil organic matter, along with the changes in external conditions, such as natural fires.

Parole chiave

  • Fire
  • Humic substances (HS)
  • Humic acid (HA)
  • Fulvic acid (FA)
  • UV-VIS spectrophotometry
Accesso libero

Influence of Explosion Chamber Shape on Timing Parameters of Disperser

Pubblicato online: 05 Aug 2021
Pagine: 143 - 148

Astratto

Abstract

A standardized device with a volume of 1 m3 or 20 L is used to determine explosion parameters. An explosion chamber where explosion takes place is of a spherical or cylindrical shape that suits the shape of a cubic container. In the case of a cylindrical vessel, the diameter and depth of the vessel are 1: 1. In this case, it is a spherical vessel with a volume of 365 liters. Time parameters of the disperser in the spherical vessel are compared with those of a truncated spherical vessel with a volume of 291 liters. Comparison of the measurement results showed that the optimal delay time of the explosion chamber with a volume of 291 liters is 290 ms, while the delay time of the explosion chamber with a volume of 365 liters is 350 ms.

Parole chiave

  • Explosion chamber
  • dispersed dust
  • disperser
  • timing parameters
Accesso libero

Infuence of Selected Pharmaceuticals on Biogas Production in Mesophilic Anaerobic Fermentation

Pubblicato online: 05 Aug 2021
Pagine: 149 - 157

Astratto

Abstract

This article deals with pharmaceutical compounds as micropollutants in anaerobic digestion of sludge from waste water treatment plant (WWTP). Part of the work included the research into presence of pharmaceuticals in different types of waters. Description of anaerobic fermentation process is also important in terms of optimal conditions. The practical aim of the investigation was preparation of a model of anaerobic fermentation of sewage sludge, where influence of pharmaceuticals on mesophilic anaerobic digestion was monitored. Wash out of micropollutants from sludge in big semicontinuous anaerobic reactors was running since October 2013. The resulting non-adapted sludge from mesophilic reactor was used since March 2014 for pharmaceuticals tests in half-a-litre glass bottles with a septum cap. The compounds of interest were diclofenac, tramadol, ibuprofen, carbamazepine and amoxicillin and their concentration in the tested sludge was 10 μg/L and 500 μg/L. The results showed that pharmaceuticals have different influence on the amount of produced biogas even if they are from the same therapeutic group. In the low concentration, the inhibition was present for diclofenac, carbamazepine and amoxicillin, at the high concentration, while diclofenac showed almost no influence. Other compounds caused a stimulative effect on the process. The mixture of all pharmaceuticals of interest in low concentration was stimulative at first, while it was inhibotory since mid-time of the test.

Parole chiave

  • Pharmaceuticals
  • micropollutants
  • anaerobic fermentation
  • sewage sludge
Accesso libero

Electrochemical Recovery of Silver Using a Simple Cell

Pubblicato online: 05 Aug 2021
Pagine: 158 - 166

Astratto

Abstract

The amount of generated e-waste during the last decades has been steadily raising to the point at which it is highly desirable to obtain the precious metals by recycling the e-waste without the need of exploiting the environment. The rapid development of technology, steep growth of modern facilities with user-friendly electronical devices and a stiff competition between manufacturers are among the main reasons for decreasing the life span of such devices, and subsequently end up as an obsolete waste product. Rapid industrialization and urbanization have also caused many environmental problems, e.g. heavy metal contamination. Silver is one of the precious metals with exceptionally high industrial applications, which makes it an area of research of high interest. Demand for silver continues to grow with progress in the industrialized world, while the world reserves of high-quality silver ores are declining. Although, there are large stocks of low and lean quality silver ores still to be mined, the main goal of this article is to provide a simple, effective and eco-friendly method of silver recovery from e-waste, e.g. electrical circuit breakers using an electrochemical cell. After 20.75 days of the experiment, 1481.5 grams of silver contacts were processed with a final yield of 61.41 % grams of silver dendrite crystals (99.9 % purity).

Parole chiave

  • Electrochemical recovery
  • electrolytic cell
  • silver
  • circuit breakers contacts

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