Materials

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6 pages, 217 KiB

Open AccessEditorial

Processing of End-of-Life Materials and Industrial Wastes

by Ndue Kanari, Seit Shallari and Eric Allain

Materials 2022, 15(21), 7662; https://doi.org/10.3390/ma15217662 - 31 Oct 2022

Cited by 1 | Viewed by 1285

Abstract

This Special Issue (SI) offered the opportunity to present the latest scientific developments and findings in the field of processing of end-of-life materials and solid industrial wastes. Due to the large quantity of wastes generated and to their complex elemental and mineralogical composition, [...] Read more.

This Special Issue (SI) offered the opportunity to present the latest scientific developments and findings in the field of processing of end-of-life materials and solid industrial wastes. Due to the large quantity of wastes generated and to their complex elemental and mineralogical composition, the approaches, methods and processes proposed for their decontamination, energy beneficiation and high-added-value metal recovery are complex and diverse. Some transversal research investigations using wastes as remediation agents and for synthesis of new materials were also included in the SI. After a brief introduction, the main scientific contributions and findings of each article published in the SI are summarized. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

Research

Jump to: Editorial

11 pages, 2876 KiB

Open AccessArticle

Preparation and Basic Properties of Praseodymium-Neodymium-Chromium Containing Imitation Gemstone Glass

by Siqi Zhang, Keqing Li, Junyuan Pu and Wen Ni

Materials 2022, 15(20), 7341; https://doi.org/10.3390/ma15207341 - 20 Oct 2022

Cited by 3 | Viewed by 2038

Abstract

Imitation gemstone glass has numerous characteristics, including low cost, rich colour, stable colouring, and the formation of colour-changing effects that can meet the jewellery market demand for beautiful gemstones of middle and low grades. In this study, four types of gem-imitating glass were [...] Read more.

Imitation gemstone glass has numerous characteristics, including low cost, rich colour, stable colouring, and the formation of colour-changing effects that can meet the jewellery market demand for beautiful gemstones of middle and low grades. In this study, four types of gem-imitating glass were prepared by the elemental substitution of praseodymium, neodymium and chromium elements based on rare earth glass and examined by combining refractive index, density, spectral characteristics and colour parameters. Sample 1 contained only Pr₆O₁₁ and showed a golden-yellow colour like chrysoberyl. Sample 2 contained only Nd₂O₃ and showed a blue-purple colour like amethyst. Sample 3 contained Pr₆O₁₁ and Nd₂O₃ and appeared green under D65 light source and red under A light source, with a colour-change effect like alexandrite. Sample 4 contained Pr₆O₁₁, Nd₂O₃ and Cr₂O₃ and showed a highly saturated green colour like emerald because of the strong colouring effect of Cr³⁺ in the glass. The findings revealed that all four samples are transparent, with a refractive index greater than 1.5 and a density higher than 2.6 g/cm³. The comprehensive performance of the four imitation gemstone glasses can be found in the corresponding natural gemstones, which has a certain practical value. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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27 pages, 11692 KiB

Open AccessArticle

Multicomponent Low Initial Molar Ratio of SiO₂/Al₂O₃ Geopolymer Mortars: Pilot Research

by Barbara Słomka-Słupik, Paulina Wiśniewska and Wiktor Bargieł

Materials 2022, 15(17), 5943; https://doi.org/10.3390/ma15175943 - 28 Aug 2022

Cited by 9 | Viewed by 2029

Abstract

Alkali-activated binders have the potential to consume various types of waste materials. Low initial molar ratios of SiO₂/Al₂O₃ geopolymer mortars were considered in this article. Here we studied alkali-activated binders produced with photovoltaic glass powder in 5%; kaolin [...] Read more.

Alkali-activated binders have the potential to consume various types of waste materials. Low initial molar ratios of SiO₂/Al₂O₃ geopolymer mortars were considered in this article. Here we studied alkali-activated binders produced with photovoltaic glass powder in 5%; kaolin clay in 15%; ground granulated blast furnace slag in 30%; alumina-lime cement in 30%; and, interchangeably, fly ash from coal combustion in 5%, fly ash from biomass combustion in 5%, or granulated autoclaved cellular concrete in 5%. The influence of clay dehydroxylation, curing conditions, glass presence, and a kind of waste material was investigated. According to the experimental results, strength (compressive and tensile) gradually increased with increasing time and with the use of calcined clay. Significant improvement in compressive strength was seen with the additional 3 days curing time in 105 °C when non-sintered clay was used. The presence of photovoltaic glass in alkali-activated mortars immobilised mercury and arsenic but released zinc, chromium, and sulphates. The microscopic observations confirmed the greater densification of the microstructure of the binder made of calcined clay due to its greater surface development and dehydroxylation. The binder of non-calcined clay was granular, and the interfacial transitional zone was more porous. The C–A–S–H gel seemed to be the main phase. XRD examination confirmed the presence of C–A–S–H, C–S–H, zeolites, and many other phases in minor amount. The presented research was a pilot study, and its main goal was to develop it further. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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20 pages, 78152 KiB

Open AccessArticle

Removal of Organic Dyes from Aqueous Solutions by Activated Carbons Prepared from Residue of Supercritical Extraction of Marigold

by Aleksandra Bazan-Wozniak, Robert Wolski, Dorota Paluch, Piotr Nowicki and Robert Pietrzak

Materials 2022, 15(10), 3655; https://doi.org/10.3390/ma15103655 - 20 May 2022

Cited by 9 | Viewed by 1655

Abstract

In the present work, we reported on the efficiency of the removal of organic dyes by adsorption on activated carbons prepared from the residue of supercritical extraction of marigold. The performance of adsorbents prepared was tested towards methyl red, methylene blue, malachite green, [...] Read more.

In the present work, we reported on the efficiency of the removal of organic dyes by adsorption on activated carbons prepared from the residue of supercritical extraction of marigold. The performance of adsorbents prepared was tested towards methyl red, methylene blue, malachite green, and crystal violet at room temperature. The effects of carbonization (500 and 700 °C) and activation (700 and 800 °C) temperatures, textural parameters, and acid-base character of the adsorbent surface on the sorption properties of the activated carbons were established. Activated carbons are characterized by low developed specific surface area, from 2 to 206 m²/g, and have a basic character of the surface (pH of carbons water extracts ranging from 10.4 to 11.2). Equilibrium adsorption isotherms were investigated. The equilibrium data were analyzed in the Langmuir, Freundlich, and Temkin models. The adsorption capacities of activated carbons studied varied from 47.62 to 102.43 mg/g towards methyl red, 53.14 to 139.72 mg/g towards methyl red, 425.46 to 622.80 towards malachite green and 155.91 to 293.75 mg/g towards crystal violet, from their water solutions. Kinetics of the adsorption of the organic dyes studied were found to be described by the pseudo-second-order model. It was proven that through the physical activation of the residue of supercritical extraction of marigold, it is possible to obtain carbonaceous materials of very high adsorption capacity towards organic pollutants. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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13 pages, 9028 KiB

Open AccessArticle

Research on Flocculant Selection for Classified Fine Tailings Based on Micro-Characterization of Floc Structure Characteristics

by Yuye Tan, Xiang Meng, Zhiwei Jiang, Chongchong Han and Mochuan Guo

Materials 2022, 15(7), 2460; https://doi.org/10.3390/ma15072460 - 27 Mar 2022

Cited by 3 | Viewed by 1874

Abstract

The rapid settlement of tailings is an important technical guarantee for the continuous production of downhole filling. The selection of a reasonable flocculant is essential for accelerating the settlement speed of classified fine tailings. The present paper conducts indoor static sedimentation experiments, NMR [...] Read more.

The rapid settlement of tailings is an important technical guarantee for the continuous production of downhole filling. The selection of a reasonable flocculant is essential for accelerating the settlement speed of classified fine tailings. The present paper conducts indoor static sedimentation experiments, NMR observation, electron microscope scanning, and other methods to analyze the porosity and pore-size distribution characteristics of floc solution for classified fine tailing under four flocculants, namely, ZYZ, ZYD, JYC-1, and JYC-2. The dimension, spatial distribution characteristics, particle size characteristics, and morphological characteristics of the scanning electron microscope images of floc were studied. Results show that the unit consumption of flocculant at 30 g/t is the critical value for increasing the flocculation and sedimentation effect of the classified fine tailings solution. The highest distribution percentage of small-sized classified fine tailings and the lowest average pore size was observed under the ZYZ-type flocculant. This flocculant also obtained the lowest porosity, largest average floc size, largest area occupied by the floc, lowest pore percentage, and the densest floc structure. Thus, this flocculant showed the best flocculation effect. A negative correlation was observed between the equivalent diameter of floc with varying settlement heights. The dimension of floc increased with the decrease in bed settlement height, and the overall structure of the floc gradually transitioned from loose to dense from top to bottom. The present paper characterizes the microscopic morphology and spatial structure characteristics of floc under different flocculants from a microscopic point of view. The present paper also provides a scientific basis for the selection of the optimal flocculant. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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14 pages, 24726 KiB

Open AccessArticle

Leaching of Copper Contained in Waste Printed Circuit Boards, Using the Thiosulfate—Oxygen System: A Kinetic Approach

by Eleazar Salinas-Rodríguez, Juan Hernández-Ávila, Eduardo Cerecedo-Sáenz, Alberto Arenas-Flores, Maria A. Veloz-Rodríguez, Norman Toro, Maria del P. Gutiérrez-Amador and Otilio A. Acevedo-Sandoval

Materials 2022, 15(7), 2354; https://doi.org/10.3390/ma15072354 - 22 Mar 2022

Cited by 5 | Viewed by 1976

Abstract

The present work is related to the treatment of crushed waste of printed circuit boards (WPCBs) from electrical and electronic devices (WEEE), carrying out the recovery of copper in solution. In the first stage, the studied material was characterized by AAS, SEM-EDS, and [...] Read more.

The present work is related to the treatment of crushed waste of printed circuit boards (WPCBs) from electrical and electronic devices (WEEE), carrying out the recovery of copper in solution. In the first stage, the studied material was characterized by AAS, SEM-EDS, and XRD. The results revealed significantly high amounts of copper (744.42 mg/g), compared with the rest of the metals present in the sample, mainly iron and zinc. In the second stage of the work, alkali dynamic leaching experiments were carried out in the

S_{2} O_{3}^{- 2} - O_{2}

medium, evaluating important kinetic variables in order to verify the controlling step of the system and adjust the data to a kinetic model. According to the results obtained from the various experimental tests executed, it was found that in the studied system of

S_{2} O_{3}^{- 2} - O_{2}

, the leaching of copper was preferably adjusted to the model of spherical particles with a shrinking core finding a mixed chemical–diffusive control, with values of E_a = 25.78 kJ/mol and n = 0.22 (for the leaching reagent), indicating that the reaction was controlled by the oxygen transport to the solid–liquid interface and also by the chemical reaction in the surface of particles, obtaining up to 99.82% copper in solution. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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16 pages, 3935 KiB

Open AccessArticle

High-Selective Extraction of Scandium (Sc) from Bauxite Residue (Red Mud) by Acid Leaching with MgSO₄

by Andrei Shoppert, Irina Loginova, Julia Napol’skikh and Dmitry Valeev

Materials 2022, 15(4), 1343; https://doi.org/10.3390/ma15041343 - 11 Feb 2022

Cited by 10 | Viewed by 2477

Abstract

Bauxite residue, also known as red mud (RM), from alumina production is the most promising technogenic material for the production of scandium (Sc) and other rare earth elements (REEs). Conveniently, RM is processed by using a strong acid (pH < 2.5), which lead [...] Read more.

Bauxite residue, also known as red mud (RM), from alumina production is the most promising technogenic material for the production of scandium (Sc) and other rare earth elements (REEs). Conveniently, RM is processed by using a strong acid (pH < 2.5), which lead to co-dissolution of iron and other undesirable major components. In this work, for the first time, the possibility of selective extraction of scandium from red mud by using highly diluted acid (pH > 4) in the presence of MgSO₄ was shown. The effect of temperature (40–80 °C), time (0–60 min), pH (2–5), and the MgSO₄ concentration (12–36 g L⁻¹) on Sc extraction efficiency was evaluated. It was shown that Sc extraction was higher than 63% even at a pH of 4, at 80 °C, after 1 h, while more than 80% could be extracted at a pH of 2. Iron extraction reduced from 7.7 to 0.03% by increasing the pH from 2 to 4. The kinetics study using the shrinking core model (SCM) has shown that diffusion through a product layer is a rate-limiting stage of the process at high temperatures (>60 °C) and low pH (<3), whereas, at lower temperatures and higher pH values, the leaching rate is limited by diffusion through the liquid film. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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11 pages, 2656 KiB

Open AccessArticle

Metallurgical Coke Combustion with Different Reactivity under Nonisothermal Conditions: A Kinetic Study

by Yuelin Qin, Qingfeng Ling, Wenchao He, Jinglan Hu and Xin Li

Materials 2022, 15(3), 987; https://doi.org/10.3390/ma15030987 - 27 Jan 2022

Cited by 10 | Viewed by 2394

Abstract

The combustion characteristics and kinetics of high- and low-reactivity metallurgical cokes in an air atmosphere were studied by thermogravimetric instrument. The Coats–Redfern, FWO, and Vyazovkin integral methods were used to analyze the kinetics of the cokes, and the kinetic parameters of high- and [...] Read more.

The combustion characteristics and kinetics of high- and low-reactivity metallurgical cokes in an air atmosphere were studied by thermogravimetric instrument. The Coats–Redfern, FWO, and Vyazovkin integral methods were used to analyze the kinetics of the cokes, and the kinetic parameters of high- and low-reactivity metallurgical cokes were compared. The results show that the heating rate affected the comprehensive combustion index and combustion reaction temperature range of the cokes. The ignition temperature, burnout temperature, combustion characteristics, and maximum weight-loss rate of low-reactivity coke (L-Coke) were better than high-reactivity coke (H-Coke). Low-reactivity coke had better thermal stability and combustion characteristics. At the same time, it was calculated via three kinetic analysis methods that the combustion activation energy gradually decreased with the progress of the reaction. The coke combustion activation energy calculated by the Coats–Redfern method was larger than the coke combustion activation energy calculated by the FWO and Vyazovkin methods, but the laws were consistent. The activation energy of L-Coke was about 4~8 kJ/mol more than that of H-Coke. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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19 pages, 8049 KiB

Open AccessArticle

Physico-Chemical Characteristics of Spodumene Concentrate and Its Thermal Transformations

by Allen Yushark Fosu, Ndue Kanari, Danièle Bartier, Harrison Hodge, James Vaughan and Alexandre Chagnes

Materials 2021, 14(23), 7423; https://doi.org/10.3390/ma14237423 - 3 Dec 2021

Cited by 11 | Viewed by 3313

Abstract

Spodumene concentrate from the Pilbara region in Western Australia was characterized by X-ray diffraction (XRD), Scanning Electron Microscope Energy Dispersive Spectroscopy (SEM-EDS) and Mineral Liberation Analysis (MLA) to identify and quantify major minerals in the concentrate. Particle diameters ranged from 10 to 200 [...] Read more.

Spodumene concentrate from the Pilbara region in Western Australia was characterized by X-ray diffraction (XRD), Scanning Electron Microscope Energy Dispersive Spectroscopy (SEM-EDS) and Mineral Liberation Analysis (MLA) to identify and quantify major minerals in the concentrate. Particle diameters ranged from 10 to 200 microns and the degree of liberation of major minerals was found to be more than 90%. The thermal behavior of spodumene and the concentration of its polymorphs were studied by heat treatments in the range of 900 to 1050 °C. All three polymorphs of the mineral (α, γ and β) were identified. Full transformation of the α-phase was achieved at 975 °C and 1000 °C after 240 and 60 min treatments, respectively. SEM images of thermally treated concentrate revealed fracturing of spodumene grains, producing minor cracks initially which became more prominent with increasing temperature. Material disintegration, melting and agglomeration with gangue minerals were also observed at higher temperatures. The metastable γ-phase achieved a peak concentration of 23% after 120 min at 975 °C. We suggest 1050 °C to be the threshold temperature for the process where even a short residence time causes appreciable transformation, however, 1000 °C may be the ideal temperature for processing the concentrate due to the degree of material disintegration and α-phase transformation observed. The application of a first-order kinetic model yields kinetic parameters which fit the experimental data well. The resultant apparent activation energies of 655 and 731 kJ mol⁻¹ obtained for α- and γ-decay, respectively, confirm the strong temperature dependence for the spodumene polymorph transformations. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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16 pages, 3617 KiB

Open AccessArticle

Use of the O₂-Thiosemicarbazide System, for the Leaching of: Gold and Copper from WEEE & Silver Contained in Mining Wastes

by Eduardo Cerecedo-Sáenz, Edgar A. Cárdenas-Reyes, Abner H. Rojas-Calva, Ma. Isabel Reyes-Valderrama, Ventura Rodríguez-Lugo, Norman Toro, Edelmira Gálvez, Otilio A. Acevedo-Sandoval, Juan Hernández-Ávila and Eleazar Salinas-Rodríguez

Materials 2021, 14(23), 7329; https://doi.org/10.3390/ma14237329 - 30 Nov 2021

Cited by 4 | Viewed by 1648

Abstract

Environmental pollution today is a latent risk for humanity, here the need to recycle waste of all kinds. This work is related to the kinetic study of the leaching of gold and copper contained in waste electrical and electronic equipment (WEEE) and silver [...] Read more.

Environmental pollution today is a latent risk for humanity, here the need to recycle waste of all kinds. This work is related to the kinetic study of the leaching of gold and copper contained in waste electrical and electronic equipment (WEEE) and silver contained in mining wastes (MW), using the O₂-thiosemicarbazide system. The results obtained show that this non-toxic leaching system is adequate for the leaching of said metals. Reaction orders were found ranging from 0 (Cu), 0.93 (Ag), and 2.01 (Au) for the effect of the reagent concentration and maximum recoveries of 77.7% (Cu), 95.8% (Au), and 60% (Ag) were obtained. Likewise, the activation energies found show that the leaching of WEEE is controlled by diffusion (Cu Ea = 9.06 and Au Ea = 18.25 kJ/Kmol), while the leaching of MW (Ea = 45.55 kJ/Kmol) is controlled by the chemical reaction. For the case of stirring rate, it was found a low effect and only particles from WEEE and MW must be suspended in solution to proceed with the leaching. The pH has effect only at values above 8, and finally, for the case of MW, the O₂ partial pressure has a market effect, going the Ag leaching from 33% at 0.2 atm up to 60% at a 1 atm. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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10 pages, 5020 KiB

Open AccessArticle

Effect of Oily Sludge Treatment with Molten Blast Furnace Slag on the Mineral Phase Reconstruction of Water-Quenched Slag Properties

by Yuelin Qin, Ke Zhang, Xinlong Wu, Qingfeng Ling, Jinglan Hu, Xin Li and Hao Liu

Materials 2021, 14(23), 7285; https://doi.org/10.3390/ma14237285 - 28 Nov 2021

Cited by 4 | Viewed by 2521

Abstract

Blast furnace slag, which is the main by-product of the ironmaking process discharged at 1450 °C, contains high-quality sensible heat, while oily sludge is the main solid waste produced in the process of gas exploration, storage, and transportation. The energy and resource utilization [...] Read more.

Blast furnace slag, which is the main by-product of the ironmaking process discharged at 1450 °C, contains high-quality sensible heat, while oily sludge is the main solid waste produced in the process of gas exploration, storage, and transportation. The energy and resource utilization of blast furnace slag is complementary to the environmentally friendly treatment of oily sludge, which has provided a new idea for the multi-factor synergistic cycle and energy transformation of the two wastes. The pyrolysis of the oily sludge with the molten blast furnace slag was conducted in the current paper. Results showed that the oily sludge was rapidly pyrolyzed, and the heavy metal elements in the oily sludge were solidified. The solidification rate of the heavy metals exceeds 90%, except for vanadium. The reconstituted water-quenched blast furnace slag still has good activity, and it will not affect the further use of the slag after pyrolysis (BFS-P). Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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16 pages, 1512 KiB

Open AccessArticle

Solid Peroxy Compounds as Additives to Organic Waste for Reclamation of Post-Industrial Contaminated Soils

by Angelika Więckol-Ryk, Maciej Thomas and Barbara Białecka

Materials 2021, 14(22), 6979; https://doi.org/10.3390/ma14226979 - 18 Nov 2021

Cited by 2 | Viewed by 1819

Abstract

Solid peroxy compounds have been increasingly applied for the removal of organic pollution from contaminated groundwater and soil due to their ability to release oxygen and hydrogen peroxide. The influence of two solid peroxy compounds (sodium percarbonate, 2Na₂CO₃·3H₂ [...] Read more.

Solid peroxy compounds have been increasingly applied for the removal of organic pollution from contaminated groundwater and soil due to their ability to release oxygen and hydrogen peroxide. The influence of two solid peroxy compounds (sodium percarbonate, 2Na₂CO₃·3H₂O₂ and calcium peroxide, CaO₂) with poultry manure (PM) added to contaminated soil on the growth of the tested plants (Sinapis alba, Lepidium sativum L. and Sorghum bicolor L. Moench) and the quality of soil water leachates was investigated. A series of experiments involving the addition of CaO₂ and 2Na₂CO₃·3H₂O₂ at the dose of 0.075 g/g PM improved the growth of tested plants. The conducted study indicated that the use of peroxy compounds not only removed pathogens from livestock waste, but also improved the quality of plant growth. The calculated factors for the growth of roots (GFR) and growth of shoots (GFS) in soils treated with a mixture of peroxy compounds and PM were higher than in soils treated only with PM. The physicochemical analysis of soil water leachates indicated that solid peroxy compounds may be a promising alternative compared to the currently used hygienizing agent such as calcium hydroxide (Ca(OH)₂). Solid peroxy compounds increased the bioavailability of components necessary for proper seed germination and plant growth (N, P, K, Ca, Mg and S). In most of the studied cases, the obtained plant shoot and root growth rates were higher for soil mixtures containing organic waste deactivated by biocidal compounds, compared to soils that contained only poultry manure. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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14 pages, 2825 KiB

Open AccessArticle

Volcanic Tuff as Secondary Raw Material in the Production of Clay Bricks

by Nicoleta Cobîrzan, Gyorgy Thalmaier, Anca-Andreea Balog, Horia Constantinescu, Andrei Ceclan and Mircea Nasui

Materials 2021, 14(22), 6872; https://doi.org/10.3390/ma14226872 - 15 Nov 2021

Cited by 8 | Viewed by 2584

Abstract

The present work examines an innovative manufacturing technique for fired clay bricks, using tuff as a secondary raw material. Samples were made of clay and tuff (0–30 wt.%) fired at 900 to 1100 °C. The chemical and mineralogical compositions and physical and thermal [...] Read more.

The present work examines an innovative manufacturing technique for fired clay bricks, using tuff as a secondary raw material. Samples were made of clay and tuff (0–30 wt.%) fired at 900 to 1100 °C. The chemical and mineralogical compositions and physical and thermal analyses of raw materials were investigated by using SEM-EDS, RX and DTA-TG curves. The samples were analysed from the mineralogical, technological and mechanical points of view. The result show that the tuff’s presence in the clay mixtures considerably reduced the shrinkage of the product during the firing process, and the manufactured samples were of excellent quality. The compressive strength of the bricks varied from 5–35.3MPa, being influenced by the tuff content, clay matrix properties and firing temperatures. Finally, the heat demand for increasing the temperature from room to the firing temperature of the sample with 10% tuff content was 22%. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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11 pages, 380 KiB

Open AccessArticle

Micronized Oat Husk: Particle Size Distribution, Phenolic Acid Profile and Antioxidant Properties

by Dariusz Dziki, Wojciech Tarasiuk and Urszula Gawlik-Dziki

Materials 2021, 14(18), 5443; https://doi.org/10.3390/ma14185443 - 20 Sep 2021

Cited by 16 | Viewed by 2779

Abstract

Oat husk (OH; hull) is a by-product generated from oat processing and is rich in insoluble fibre and phenolic compounds. The aim of this work was to study the particle size distribution, antioxidant activity, and phenolic profile of micronized OH. For this purpose, [...] Read more.

Oat husk (OH; hull) is a by-product generated from oat processing and is rich in insoluble fibre and phenolic compounds. The aim of this work was to study the particle size distribution, antioxidant activity, and phenolic profile of micronized OH. For this purpose, the hull was first sterilized using superheated steam and was then ground using an impact classifier mill. The particle size distribution (PSD) of the ground husk was determined using the laser diffraction method and the parameters characterizing the PSD of the ground husk, and its antioxidant activity were calculated. In addition, UPLC-MS/MS analysis of phenolic acids was also performed. Micronization of the sterilized husk effectively decreased the size of the particles, and with the increasing speed of the rotor and classifier, the median size of the particles (d₅₀) decreased from 63.8 to 16.7 µm. The following phenolic acids were identified in OH: ferulic, caffeic, p-hydroxybenzoic, vanillic, syringic, and synapic acid. Ferulic acid constituted about 95% of total phenolic acids. The antioxidant activity of the obtained extracts increased as the particle size of the micronized husk decreased. The highest half maximal inhibitory concentration (EC₅₀ index) was found for chelating power, and the lowest was found in the case of radical scavenging activity against DPPH. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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19 pages, 5005 KiB

Open AccessArticle

Some Aspects of the Thermochemical Route for the Valorization of Plastic Wastes, Part I: Reduction of Iron Oxides by Polyvinyl Chloride (PVC)

by Ndue Kanari, Nour-Eddine Menad, Lev O. Filippov, Seit Shallari, Eric Allain, Fabrice Patisson and Jacques Yvon

Materials 2021, 14(15), 4129; https://doi.org/10.3390/ma14154129 - 24 Jul 2021

Cited by 5 | Viewed by 2395

Abstract

The mass production of synthetic plastics began in the last century and today they have become one of the most abundant man-made materials. The disposal or the beneficiation of end-of-life plastics represent a great challenge for society especially in the case of polyvinyl [...] Read more.

The mass production of synthetic plastics began in the last century and today they have become one of the most abundant man-made materials. The disposal or the beneficiation of end-of-life plastics represent a great challenge for society especially in the case of polyvinyl chloride (PVC). This study is focused on the use of PVC waste as a useful agent for the direct reduction of hematite (Fe₂O₃) after a thermal treatment at 300 °C for removing the chlorine contained in PVC. Thermal reduction tests were conducted from 600 °C to 1100 °C with (Fe₂O₃ + PVC + clay) pellet mixtures in which clay was used as plasticizing and binder agent of the pellets. The starting samples and treatment residues were analyzed by scanning electron microscopy through energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD) to monitor the chemical behavior and reactivity of the pellet constituents during their thermal treatment. The stepwise reduction of hematite up to metallic iron was achieved at temperatures approaching 1000 °C, confirming the capability of using PVC waste for the direct reduction of iron oxides. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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17 pages, 3139 KiB

Open AccessArticle

Improving the Properties of Degraded Soils from Industrial Areas by Using Livestock Waste with Calcium Peroxide as a Green Oxidizer

by Angelika Więckol-Ryk, Maciej Thomas and Barbara Białecka

Materials 2021, 14(11), 3132; https://doi.org/10.3390/ma14113132 - 7 Jun 2021

Cited by 4 | Viewed by 2712

Abstract

Over the past years, the treatment and use of livestock waste has posed a significant problem in environmental engineering. This paper outlines a new approach to application of calcium peroxide (CaO₂) as a green oxidizer and microbiocidal agent in the treatment [...] Read more.

Over the past years, the treatment and use of livestock waste has posed a significant problem in environmental engineering. This paper outlines a new approach to application of calcium peroxide (CaO₂) as a green oxidizer and microbiocidal agent in the treatment of poultry manure. It also presents the application of pretreated waste in improvement of degraded soils in industrial areas. The CCD (Central Composite Design) and RSM (Response Surface Methodology) were employed for optimizing the process parameters (CaO₂ concentration 1.6–8.4 wt %, temperature 5.2–38.8 °C and contact time 7–209 h). The analysis of variance (ANOVA) was used to analyze the experimental results, which indicated good fit of the approximated to the experimental data (R² = 0.8901, R²_adj = 0.8168). The amendment of CaO₂ in optimal conditions (8 wt % of CaO_2, temperature 22 °C and contact time 108 h) caused a decrease in bacteria Escherichia coli (E. coli) in poultry manure from 8.7 log₁₀ CFU/g to the acceptable level of 3 log₁₀ CFU/g. The application of pretreated livestock waste on degraded soils and the studies on germination and growth of grass seed mixture (Lollum perenne—Naki, Lollum perenne—Grilla, Poa pratensis—Oxford, Festuca rubbra—Relevant, Festuca rubbra—Adio and Festuca trachypylla—Fornito) showed that a dose of 0.08 g of CaO₂ per 1 gram of poultry manure induced higher yield of grass plants. The calculated indicators for growth of roots (GFR) and shoots (GFS) in soils treated with poultry manure were 10–20% lower compared to soils with amended CaO₂. The evidence from this study suggests that CaO₂ could be used as an environmentally friendly oxidizer and microbiocidal agent for livestock waste. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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23 pages, 13731 KiB

Open AccessArticle

Effect of Waste Glass on the Properties and Microstructure of Magnesium Potassium Phosphate Cement

by Qiubai Deng, Zhenyu Lai, Rui Xiao, Jie Wu, Mengliang Liu, Zhongyuan Lu and Shuzhen Lv

Materials 2021, 14(8), 2073; https://doi.org/10.3390/ma14082073 - 20 Apr 2021

Cited by 16 | Viewed by 2366

Abstract

Waste glass is a bulk solid waste, and its utilization is of great consequence for environmental protection; the application of waste glass to magnesium phosphate cement can also play a prominent role in its recycling. The purpose of this study is to evaluate [...] Read more.

Waste glass is a bulk solid waste, and its utilization is of great consequence for environmental protection; the application of waste glass to magnesium phosphate cement can also play a prominent role in its recycling. The purpose of this study is to evaluate the effect of glass powder (GP) on the mechanical and working properties of magnesium potassium phosphate cement (MKPC). Moreover, a 40mm × 40mm × 40mm mold was used in this experiment, the workability, setting time, strength, hydration heat release, porosity, and microstructure of the specimens were evaluated. The results indicated that the addition of glass powder prolonged the setting time of MKPC, reduced the workability of the matrix, and effectively lowered the hydration heat of the MKPC. Compared to an M/P ratio (MgO/KH₂PO₄ mass ratio) of 1:1, the workability of the MKPC with M/P ratios of 2:1 and 3:1 was reduced by 1% and 2.1%, respectively, and the peak hydration temperatures were reduced by 0.5% and 14.6%, respectively. The compressive strength of MKPC increased with an increase in the glass powder content at the M/P ratio of 1:1, and the addition of glass powder reduced the porosity of the matrix, effectively increased the yield of struvite-K, and affected the morphology of the hydration products. With an increase in the M/P ratio, the struvite-K content decreased, many tiny pores were more prevalent on the surface of the matrix, and the bonding integrity between the MKPC was weakened, thereby reducing the compressive strength of the matrix. At less than 40 wt.% glass powder content, the performance of MKPC improved at an M/P ratio of 1:1. In general, the addition of glass powders improved the mechanical properties of MKPC and reduced the heat of hydration. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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14 pages, 6460 KiB

Open AccessArticle

New EAF Slag Characterization Methodology for Strategic Metal Recovery

by Nour-Eddine Menad, Nassima Kana, Alain Seron and Ndue Kanari

Materials 2021, 14(6), 1513; https://doi.org/10.3390/ma14061513 - 19 Mar 2021

Cited by 20 | Viewed by 3818

Abstract

The grown demand of current and future development of new technologies for high added value and strategic metals, such as molybdenum, vanadium, and chromium, and facing to the depletion of basic primary resources of these metals, the metal extraction and recovery from industrial [...] Read more.

The grown demand of current and future development of new technologies for high added value and strategic metals, such as molybdenum, vanadium, and chromium, and facing to the depletion of basic primary resources of these metals, the metal extraction and recovery from industrial by-products and wastes is a promising choice. Slag from the steelmaking sector contains a significant amount of metals; therefore, it must be considered to be an abundant secondary resource for several strategic materials, especially chromium. In this work, the generated slag from electric arc furnace (EAF) provided by the French steel industry was characterized by using multitude analytical techniques in order to determine the physico-chemical characteristics of the targeted slag. The revealed main crystallized phases are larnite (Ca₂SiO₄), magnetite (Fe₃O₄), srebrodolskite (Ca₂Fe₂O₅), wüstite (FeO), maghemite (Fe_2.6O₃), hematite (Fe₂O₃), chromite [(Fe,Mg)Cr₂O₄], and quartz (SiO₂). The collected slag sample contains about 34.1% iron (48.5% Fe₂O₃) and 3.5% chromium, whilst the vanadium contents is around 1500 ppm. The Mössbauer spectroscopy suggested that the non-magnetic fraction represents 42 wt% of the slag, while the remainder (58 wt%) is composed of magnetic components. The thermal treatment of steel slag up to 900 °C indicated that this solid is almost stable and few contained phases change their structures. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes)

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