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3 pages, 165 KiB

Open AccessEditorial

Recovery of Non-Ferrous Metal from Metallurgical Residues

by Guo Chen

Materials 2023, 16(21), 6943; https://doi.org/10.3390/ma16216943 - 29 Oct 2023

Viewed by 1610

Abstract

Non-ferrous metals and alloys are essential resources for the development of modern industries [...] Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

Research

Jump to: Editorial, Review

22 pages, 12896 KiB

Open AccessArticle

Mineralogical Characterization of Historic Copper Slag to Guide the Recovery of Valuable Metals: A Namibian Case Study

by Godfrey Dzinomwa, Benjamin Mapani, Titus Nghipulile, Kasonde Maweja, Jaquiline Tatenda Kurasha, Martha Amwaama and Kayini Chigayo

Materials 2023, 16(18), 6126; https://doi.org/10.3390/ma16186126 - 8 Sep 2023

Cited by 2 | Viewed by 1303

Abstract

The depletion of the ore reserves in the world necessitates the search for secondary sources such as waste products (tailings and slag). The treatment and cleaning up of such secondary sources also has a positive impact on the environment. A smelter in Namibia [...] Read more.

The depletion of the ore reserves in the world necessitates the search for secondary sources such as waste products (tailings and slag). The treatment and cleaning up of such secondary sources also has a positive impact on the environment. A smelter in Namibia we examined had historic slag which accumulated over decades of its operating life, thus posing the challenge of how best to collect representative samples to evaluate and propose viable methods of recovering contained metals. In this study, analytical and mineralogical characterization of the slag was performed using X-ray fluorescence (XRF) analysis, atomic absorption spectrometer (AAS), ICP-OES, scanning electron microscopy energy dispersive spectroscopy (SEM-EDS) analysis, and optical microscopy analysis. The chemical analyses showed that the metal values contained in the slag were mainly copper, lead, and zinc whose average contents were approximately 0.35% Cu, 3% Pb, and 5.5% Zn. About 10.5% Fe was also contained in the slag. Germanium was detected by scanning electron microscopy, but was however below detection limits of the chemical analysis equipment used. Based on the results, approximate conditions under which the different slag phases were formed were estimated and the recovery routes for the various metals were proposed. Analysis by both optical and scanning electron microscopy revealed that Zn and Fe occurred mainly in association with O as oxides, while Cu and Pb were mainly associated with S as sulphides. The slag consisted of three different phases, namely the silicate phase (slag), metallic phase and the sulphide phases. The phases in the slag were mainly silicate phases as well as metallic and sulphide phases. It was observed that the metallic and sulphide phases were dominant in the finer size fractions (−75 µm) whereas the sulphide phase was also present in the coarser size fractions (+300 µm). An important finding from the microscopy examination was that the sulphide phases were interstitial and could be liberated from the slag. This finding meant that liberation and subsequent concentration of the sulphide phases was feasible using conventional processing techniques. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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19 pages, 13572 KiB

Open AccessArticle

Drying Kinetics of Microwave-Assisted Drying of Leaching Residues from Hydrometallurgy of Zinc

by Chunlan Tian, Ju Zhou, Chunxiao Ren, Mamdouh Omran, Fan Zhang and Ju Tang

Materials 2023, 16(16), 5546; https://doi.org/10.3390/ma16165546 - 9 Aug 2023

Cited by 5 | Viewed by 1287

Abstract

In the hydrometallurgical process of zinc production, the residue from the leaching stage is an important intermediate product and is treated in a Waelz kiln to recover valuable metals. To ensure optimal results during the Waelz kiln process, it is necessary to pre-treat [...] Read more.

In the hydrometallurgical process of zinc production, the residue from the leaching stage is an important intermediate product and is treated in a Waelz kiln to recover valuable metals. To ensure optimal results during the Waelz kiln process, it is necessary to pre-treat the residues by drying them first due to their higher water content. This work studies the residue’s drying process using microwave technology. The study results indicate that microwave technology better removes the residue’s oxygen functional groups and moisture. The dehydration process’s effective diffusion coefficient increases as the microwave’s heating power, the initial moisture content, and the initial mass increase. The Page model is appropriate for imitating the drying process, and the activation energy of the drying process for the residues is −13.11217 g/W. These results indicate that microwave technology efficiently dries the residues from the leaching stage. Furthermore, this study provides a theoretical basis and experimental data for the industrial application of microwave drying. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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14 pages, 10618 KiB

Open AccessArticle

Numerical and Experimental Study on Carbon Segregation in Square Billet Continuous Casting with M-EMS

by Pengchao Li, Guifang Zhang, Peng Yan, Peipei Zhang, Nan Tian and Zhenhua Feng

Materials 2023, 16(16), 5531; https://doi.org/10.3390/ma16165531 - 9 Aug 2023

Cited by 2 | Viewed by 1248

Abstract

Electromagnetic stirring (M-EMS) has been extensively applied in continuous casting production to reduce the quality defects of casting billets. To investigate the effect of continuous casting electromagnetic stirring on billet segregation, a 3D multi-physics coupling model was established to simulate the internal heat, [...] Read more.

Electromagnetic stirring (M-EMS) has been extensively applied in continuous casting production to reduce the quality defects of casting billets. To investigate the effect of continuous casting electromagnetic stirring on billet segregation, a 3D multi-physics coupling model was established to simulate the internal heat, momentum, and solute transfer behavior, to identify the effect of M-EMS on the carbon segregation of a continuous casting square billet of 200 mm × 200 mm. The results show that M-EMS can move the high-temperature zone upward, which is favorable for the rapid solidification of the billet, and can promote the rotational flow of the molten steel in the horizontal direction. When the electromagnetic stirring current is varied in the range of 0–500 A, the degree of carbon segregation first decreases and then increases, with the best control of segregation at 300 A. In the frequency range of 3–5 Hz, the degree of carbon segregation degree increases with frequency. Meanwhile, the simulation and experimental results show that 3 Hz + 300 A is the best electromagnetic stirring parameter for improving the carbon segregation of casting billets with a size of 200 mm × 200 mm. So, a reasonable choice of the M-EMS parameters is crucial for the quality of the billet. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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11 pages, 1725 KiB

Open AccessArticle

Investigations of the Density and Solubility of Ammonium Perrhenate and Potassium Perrhenate Aqueous Solutions

by Szymon Orda, Michał Drzazga, Katarzyna Leszczyńska-Sejda, Mateusz Ciszewski, Alicja Kocur, Pola Branecka, Kacper Gall, Mateusz Słaboń and Marcin Lemanowicz

Materials 2023, 16(15), 5481; https://doi.org/10.3390/ma16155481 - 5 Aug 2023

Cited by 3 | Viewed by 1537

Abstract

Rhenium is largely used as an additive to nickel- and cobalt-based superalloys. Their resistance to temperature and corrosion makes them suitable for the production of turbines in civil and military aviation, safety valves in drilling platforms, and tools working at temperatures exceeding 1000 [...] Read more.

Rhenium is largely used as an additive to nickel- and cobalt-based superalloys. Their resistance to temperature and corrosion makes them suitable for the production of turbines in civil and military aviation, safety valves in drilling platforms, and tools working at temperatures exceeding 1000 °C. The purity of commercial rhenium salts is highly important. Potassium, which is a particularly undesirable element, can be removed by recrystallization. Therefore, it is crucial to possess detailed knowledge concerning process parameters including the dissolved solid concentration and the resulting saturation temperature. This can be achieved using simple densimetric methods. Due to the fact that data concerning the physicochemical properties of ammonium perrhenate (APR) NH₄ReO₄ and potassium perrhenate (PPR) KReO₄ are imprecise or unavailable in the scientific literature, the goal of this study is to present experimental data including the solubility and density of water solutions of both salts. In the experiments, a densimeter with a vibrating cell was used to precisely determine the densities. Although the investigated solutions did not fit into the earlier proposed mathematical model, some crucial conclusions could still be made based on the results. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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16 pages, 4851 KiB

Open AccessArticle

Adsorption of Sc on the Surface of Kaolinite (001): A Density Functional Theory Study

by Zilong Zhao, Kaiyu Wang, Guoyuan Wu, Dengbang Jiang and Yaozhong Lan

Materials 2023, 16(15), 5349; https://doi.org/10.3390/ma16155349 - 29 Jul 2023

Cited by 2 | Viewed by 1337

Abstract

The adsorption behavior of Sc on the surface of kaolinite (001) was investigated using the density functional theory via the generalized gradient approximation plane-wave pseudopotential method. The highest coordination numbers of hydrated

{Sc}^{3 +}

,

Sc {(OH)}^{2 +}

, and [...] Read more.

The adsorption behavior of Sc on the surface of kaolinite (001) was investigated using the density functional theory via the generalized gradient approximation plane-wave pseudopotential method. The highest coordination numbers of hydrated

{Sc}^{3 +}

,

Sc {(OH)}^{2 +}

, and

Sc {(OH)}_{2}^{+}

species are eight, six, and five, respectively. The adsorption model was based on

Sc {(OH)}_{2} {(H_{2} O)}_{5}^{+}

, which has the most stable ionic configuration in the liquid phase. According to the adsorption energy and bonding mechanism, the adsorption of Sc ionic species can be categorized into outer layer and inner layer adsorptions. We found that the hydrated Sc ions were mainly adsorbed on the outer layer of the kaolinite (001)Al-OH and (00−1)Si-O surfaces through hydrogen bonding while also being adsorbed on the inner layer of the deprotonated kaolinite (001)Al-OH surface through coordination bonding. The inner layer adsorption has three adsorption configurations, with the lying hydroxyl group (O_l) position having the lowest adsorption energy (−653.32 KJ/mol). The adsorption energy for the inner layer is lower compared to the outer layer, while the extent of deprotonation is limited. This is because the deprotonation of the inner adsorption layer is energetically unfavorable. We speculate that Sc ions species predominantly adsorb onto the surface of kaolinite (001) in an outer layer configuration. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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13 pages, 4923 KiB

Open AccessArticle

The Removal of Inclusions with Different Diameters in Tundish by Channel Induction Heating: A Numerical Simulation Study

by Bing Yi, Guifang Zhang, Qi Jiang, Peipei Zhang, Zhenhua Feng and Nan Tian

Materials 2023, 16(15), 5254; https://doi.org/10.3390/ma16155254 - 26 Jul 2023

Cited by 6 | Viewed by 1218

Abstract

The quality of the bloom will be impacted by the non-metallic impurities in the molten steel in the tundish, which will reduce the plasticity and fatigue life of the steel. In this research, a mathematical model of a six-flow double-channel T-shaped induction heating [...] Read more.

The quality of the bloom will be impacted by the non-metallic impurities in the molten steel in the tundish, which will reduce the plasticity and fatigue life of the steel. In this research, a mathematical model of a six-flow double-channel T-shaped induction heating tundish was established, the effects of induction heating conditions on the removal of inclusions in the tundish were investigated, and the impact of various inclusion particle sizes on the removal effect of inclusions under induction heating was explored. The results show that the Residence Time Distribution (RTD) curve produced through numerical simulation and physical simulation is in good agreement. The reduction of inclusion particles in the channel is made affordable by the dual-channel induction heating technique. As the diameter of inclusion particles increases from 10 μm to 50 μm, the probability of inclusion particles being removed from the channel gradually decreases from 70.9% to 56.1%. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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14 pages, 6620 KiB

Open AccessArticle

Prediction of Compressive Strength of Biomass–Humic Acid Limonite Pellets Using Artificial Neural Network Model

by Haoli Yan, Xiaolei Zhou, Lei Gao, Haoyu Fang, Yunpeng Wang, Haohang Ji and Shangrui Liu

Materials 2023, 16(14), 5184; https://doi.org/10.3390/ma16145184 - 24 Jul 2023

Cited by 3 | Viewed by 1147

Abstract

Due to the detrimental impact of steel industry emissions on the environment, countries worldwide prioritize green development. Replacing sintered iron ore with pellets holds promise for emission reduction and environmental protection. As high-grade iron ore resources decline, research on limonite pellet technology becomes [...] Read more.

Due to the detrimental impact of steel industry emissions on the environment, countries worldwide prioritize green development. Replacing sintered iron ore with pellets holds promise for emission reduction and environmental protection. As high-grade iron ore resources decline, research on limonite pellet technology becomes crucial. However, pellets undergo rigorous mechanical actions during production and use. This study prepared a series of limonite pellet samples with varying ratios and measured their compressive strength. The influence of humic acid on the compressive strength of green and indurated pellets was explored. The results indicate that humic acid enhances the strength of green pellets but reduces that of indurated limonite pellets, which exhibit lower compressive strength compared to bentonite-based pellets. Furthermore, artificial neural networks (ANN) predicted the compressive strength of humic acid and bentonite-based pellets, establishing the relationship between input variables (binder content, pellet diameter, and weight) and output response (compressive strength). Integrating pellet technology and machine learning drives limonite pellet advancement, contributing to emission reduction and environmental preservation. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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18 pages, 3277 KiB

Open AccessArticle

Recovery of Zinc from Metallurgical Slag and Dust by Ammonium Acetate Using Response Surface Methodology

by Xuemei Zheng, Jinjing Li, Aiyuan Ma and Bingguo Liu

Materials 2023, 16(14), 5132; https://doi.org/10.3390/ma16145132 - 20 Jul 2023

Cited by 1 | Viewed by 1364

Abstract

Metallurgical slag and dust (MSD) are abundant Zn-containing secondary resources that can partially alleviate the shortage of zinc minerals, with hazardous characteristics and a high recycling value. In this work, the process conditions of recycling Zn from MSD materials leaching by ammonium acetate [...] Read more.

Metallurgical slag and dust (MSD) are abundant Zn-containing secondary resources that can partially alleviate the shortage of zinc minerals, with hazardous characteristics and a high recycling value. In this work, the process conditions of recycling Zn from MSD materials leaching by ammonium acetate (NH₃-CH₃COONH₄-H₂O) were optimised using response surface methodology (RSM). The influences of liquid/solid ratio, stirring speed, leaching time, total ammonia concentration, and the interactions between these variables on the Zn effective extraction rate during the ammonium acetate leaching process were investigated. Additionally, the predicted regression equation between the Zn effective extraction rate and the four affecting factors was established, and the optimal process parameters were determined with a stirring speed of 345 r/min, leaching temperature of 25 °C, [NH₃]/[NH₄]⁺ of 1:1, total ammonia concentration of 4.8 mol/L, liquid/solid ratio of 4.3:1, and leaching time of 46 min. The Zn effective extraction rates predicted by the proposed model and the measured values were 85.25% and 84.67%, respectively, with a relative error of 0.58% between the two values, indicating the accuracy and reliability of the proposed model. XRD and SEM-EDS analysis results showed that Zn₂SiO₄, ZnS, and ZnFe₂O₄ were among the main factors affecting the low extraction rate of zinc from metallurgical slag dust. This work established a new technology prototype for the effective and clean extraction of zinc resources, which can provide new routes to effectively utilise Zn-containing MSD materials and lay a foundation for developing other novel techniques for recycling Zn from Zn-containing secondary resources. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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14 pages, 7569 KiB

Open AccessArticle

Preparation of Spherical Ultrafine Silver Particles Using Y-Type Microjet Reactor

by Xiaoxi Wan, Jun Li, Na Li, Jingxi Zhang, Yongwan Gu, Guo Chen and Shaohua Ju

Materials 2023, 16(6), 2217; https://doi.org/10.3390/ma16062217 - 10 Mar 2023

Cited by 3 | Viewed by 1793

Abstract

Herein, micron-sized silver particles were prepared using the chemical reduction method by employing a Y-type microjet reactor, silver nitrate as the precursor, ascorbic acid as the reducing agent, and gelatin as the dispersion at room temperature (23 °C ± 2°C). Using a microjet [...] Read more.

Herein, micron-sized silver particles were prepared using the chemical reduction method by employing a Y-type microjet reactor, silver nitrate as the precursor, ascorbic acid as the reducing agent, and gelatin as the dispersion at room temperature (23 °C ± 2°C). Using a microjet reactor, the two reaction solutions collide and combine outside the reactor, thereby avoiding microchannel obstruction issues and facilitating a quicker and more convenient synthesis process. This study examined the effect of the jet flow rate and dispersion addition on the morphology and size of silver powder particles. Based on the results of this study, spherical and dendritic silver particles with a rough surface can be prepared by adjusting the flow rate of the reaction solution and gelatin concentration. The microjet flow rate of 75 mL/min and the injected gelatin amount of 1% of the silver nitrate mass produced spherical ultrafine silver particles with a size of 4.84 μm and a tap density of 5.22 g/cm³. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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12 pages, 4295 KiB

Open AccessArticle

Preparation of Micro-Size Spherical Silver Particles and Their Application in Conductive Silver Paste

by Na Li, Jun Li, Xiaoxi Wan, Yifan Niu, Yongwan Gu, Guo Chen and Shaohua Ju

Materials 2023, 16(4), 1733; https://doi.org/10.3390/ma16041733 - 20 Feb 2023

Cited by 6 | Viewed by 3092

Abstract

In this paper, micro-size spherical silver particles were prepared by using a wet-chemical reduction method. The silver particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and a laser particle-size analyzer. The results indicate that different types and the content of [...] Read more.

In this paper, micro-size spherical silver particles were prepared by using a wet-chemical reduction method. The silver particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and a laser particle-size analyzer. The results indicate that different types and the content of surfactants can be used to prevent the accumulation, and control the morphology and particle size distribution, of silver particles. Moreover, the morphology of silver particles was changed from polyhedral to spherical when the pH was raised from 1 to 3. Under the optimal synthesis conditions (0.1 mol/L silver nitrate, 0.06 mol/L ascorbic acid, gelatin (5% by weight of silver nitrate), pH = 1), the micro-size spherical silver particles with diameter of 5–8 μm were obtained. In addition, the resistivity of conductive silver paste that prepared with the as-synthesized spherical silver particles was discussed in detail and the average resistivity of the conductive silver paste was 3.57 × 10⁻⁵ Ω·cm after sintering at 140 °C for 30 min. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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14 pages, 4003 KiB

Open AccessArticle

Effect of Cu on the Formation of Reversed Austenite in Super Martensitic Stainless Steel

by Wen Jiang and Kunyu Zhao

Materials 2023, 16(3), 1302; https://doi.org/10.3390/ma16031302 - 3 Feb 2023

Cited by 4 | Viewed by 1861

Abstract

We investigated the effect of Cu on the formation of reversed austenite in super martensitic stainless steel by using X-ray diffraction (XRD), a transmission electron microscope (TEM) and an energy-dispersive spectrometer (EDS). Our results showed that the microstructure of the steels comprised tempered [...] Read more.

We investigated the effect of Cu on the formation of reversed austenite in super martensitic stainless steel by using X-ray diffraction (XRD), a transmission electron microscope (TEM) and an energy-dispersive spectrometer (EDS). Our results showed that the microstructure of the steels comprised tempered martensite and diffused reversed austenite after the steels were quenched at 1050 °C and tempered at 550–750 °C. The volume fraction of reversed austenite in the steel with 3 wt.% of Cu (3Cu) was more than that with 1.5 wt.% of Cu (1.5Cu). The transmission electron microscope results revealed that the reversed austenite in 1.5Cu steel mainly had the shape of a thin strip, while that in 3Cu steel had a block shape. The nucleation points and degree of Ni enrichment of reversed austenite in 3Cu steel were higher than those in 1.5Cu steel. The reversed austenite was more likely to grow in ε-Cu enriched regions. Therefore, Cu can promote reversed austenite nucleation and growth. The mechanical properties of 3 Cu steel are obviously better than those of 1.5Cu steel when tempered at 550–650 °C. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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14 pages, 5754 KiB

Open AccessArticle

Hot Deformation Behavior of TA1 Prepared by Electron Beam Cold Hearth Melting with a Single Pass

by Zhibo Zhang, Weiwei Huang, Weidong Zhao, Xiaoyuan Sun, Haohang Ji, Shubiao Yin, Jin Chen and Lei Gao

Materials 2023, 16(1), 369; https://doi.org/10.3390/ma16010369 - 30 Dec 2022

Cited by 4 | Viewed by 1773

Abstract

The Gleeble-3800 thermal simulator was used for hot compression simulation to understand the hot deformation performance of TA1 prepared by the single-pass electron beam cold hearth (EB) process. The deformation degree is 50% on a thermal simulator when the temperature range is 700–900 [...] Read more.

The Gleeble-3800 thermal simulator was used for hot compression simulation to understand the hot deformation performance of TA1 prepared by the single-pass electron beam cold hearth (EB) process. The deformation degree is 50% on a thermal simulator when the temperature range is 700–900 °C, with a strain rate of 0.01–10⁻¹ s. According to the thermal deformation data, the true stress-strain curve of TA1 was studied. Meanwhile, the constitutive model and processing map were established through the experimental data. These results indicate that the deformation temperature negatively affects strain rate and flow stress. The heat deformation activation energy of EB produced TA1 sample was lower than that of VAR produced TA1 sample in the studied range. The best processing areas of EB-produced TA1 were strain rates of 0.05–0.01 s⁻¹, within 700–770 °C; or strain rates of 0.01–0.15 s⁻¹; 840–900 °C. The results of this paper enrich the fundamental knowledge of the thermal deformation behavior of TA1 prepared by EB furnaces. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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19 pages, 6260 KiB

Open AccessArticle

Study on the Roasting Process of Guisha Limonite Pellets

by Chuang Zhang, Xiaolei Zhou, Lei Gao and Haoyu Fang

Materials 2022, 15(24), 8845; https://doi.org/10.3390/ma15248845 - 11 Dec 2022

Cited by 2 | Viewed by 1421

Abstract

In this paper, a pelletizing method has been researched to enhance the subsequent iron-making process applying Guisha limonite, with advantages including large reserves and low price. The purpose is to provide an alternative for the sinter, thus reducing the greenhouse gas emission during [...] Read more.

In this paper, a pelletizing method has been researched to enhance the subsequent iron-making process applying Guisha limonite, with advantages including large reserves and low price. The purpose is to provide an alternative for the sinter, thus reducing the greenhouse gas emission during the iron-making process. The response surface method is used to optimize the experimental design of the pelleting process. A multivariate regression model for estimating the compressive strength of pellets was developed using Box–Behnken experimental methodology, where the relevant factors were the roasting temperature, pellet diameter, and bentonite content. The maximum influencing factors of each experimental design response are determined using analysis of variance (ANOVA). Under optimum conditions, the compressive strength of pure limonite pellets is 2705 N, similar to the response goal value of 2570.3 N, with a relative error of 5.20%. Since the high-grade iron ore resources are depleted, the comprehensive utilization of ore resources is becoming increasingly important. The aim of this paper was to provide a valuable technical foundation for lignite pellet-roasting processes in the iron and steel industries, since steel companies is increasing its imports of Guisha limonite. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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15 pages, 2540 KiB

Open AccessArticle

Studies on the Processing of Fine Dusts from the Electric Smelting of Ilmenite Concentrates to Obtain Titanium Dioxide

by Almagul Ultarakova, Zaure Karshyga, Nina Lokhova, Azamat Yessengaziyev, Kaisar Kassymzhanov and Arailym Mukangaliyeva

Materials 2022, 15(23), 8314; https://doi.org/10.3390/ma15238314 - 23 Nov 2022

Cited by 6 | Viewed by 1491

Abstract

This article presents studies on the ammonium fluoride processing of dusts from the reduction smelting of ilmenite concentrate with separation of silicon to obtain titanium dioxide. Optimal conditions for pyrohydrolysis of titanium fluorides were determined. The effects of temperature and duration on the [...] Read more.

This article presents studies on the ammonium fluoride processing of dusts from the reduction smelting of ilmenite concentrate with separation of silicon to obtain titanium dioxide. Optimal conditions for pyrohydrolysis of titanium fluorides were determined. The effects of temperature and duration on the process were studied. The optimal conditions for pyrohydrolysis of titanium fluorides were a temperature of 600 °C and duration of 240–300 min. The degree of titanium fluoride conversion to titanium oxide was 99.5% at these conditions. Titanium dioxide obtained by pyrohydrolysis of titanium fluorides was purified from iron, chromium, and manganese impurities. The effect of hydrochloric acid solution concentration, S:L ratio, and the process duration on the purification degree of titanium fluoride pyrohydrolysis was studied. The following optimum purification conditions were determined: hydrochloric acid solution concentration 12.5–15 wt%, temperature 25–30 °C, S:L = 1:6÷8, duration 20–30 min. The purified titanium dioxide consisted mainly of anatase. The pigmented titanium dioxide of rutile modification with 99.8 wt% TiO₂ was obtained after calcination at 900 °C for 120 min. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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20 pages, 48888 KiB

Open AccessArticle

A Study on the Mechanism and Kinetics of Ultrasound-Enhanced Sulfuric Acid Leaching for Zinc Extraction from Zinc Oxide Dust

by Xuemei Zheng, Shiwei Li, Bingguo Liu, Libo Zhang and Aiyuan Ma

Materials 2022, 15(17), 5969; https://doi.org/10.3390/ma15175969 - 29 Aug 2022

Cited by 7 | Viewed by 2405

Abstract

As an important secondary zinc resource, large-scale reserves of zinc oxide dust (ZOD) from a wide range of sources is of high comprehensive recycling value. Therefore, an experimental study on ultrasound-enhanced sulfuric acid leaching for zinc extraction from zinc oxide dust was carried [...] Read more.

As an important secondary zinc resource, large-scale reserves of zinc oxide dust (ZOD) from a wide range of sources is of high comprehensive recycling value. Therefore, an experimental study on ultrasound-enhanced sulfuric acid leaching for zinc extraction from zinc oxide dust was carried out to investigate the effects of various factors such as ultrasonic power, reaction time, sulfuric acid concentration, and liquid–solid ratio on zinc leaching rate. The results show that the zinc leaching rate under ultrasound reached 91.16% at a temperature of 25 °C, ultrasonic power 500 W, sulfuric acid concentration 140 g/L, liquid–solid ratio 5:1, rotating speed 100 r/min, and leaching time 30 min. Compared with the conventional leaching method (leaching rate: 85.36%), the method under ultrasound increased the zinc leaching rate by 5.8%. In a kinetic analysis of the ultrasound-enhanced sulfuric acid leaching of zinc oxide dust, the initial apparent activation energy of the reaction was 6.90 kJ/mol, indicating that the ultrasound-enhanced leaching process was controlled by the mixed solid product layers. Furthermore, the leached residue was characterized by XRD and SEM-EDS, and the results show that, with ultrasonic waves, the encapsulated mineral particles were dissociated, and the dissolution of ZnO was enhanced. Mostly, the zinc in leached residue existed in the forms of ZnFe₂O₄, Zn₂SiO₄, and ZnS. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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24 pages, 4113 KiB

Open AccessReview

Review of the Preparation and Application of Porous Materials for Typical Coal-Based Solid Waste

by Jinsong Du, Aiyuan Ma, Xingan Wang and Xuemei Zheng

Materials 2023, 16(15), 5434; https://doi.org/10.3390/ma16155434 - 3 Aug 2023

Cited by 11 | Viewed by 2671

Abstract

The discharge and accumulation of coal-based solid waste have caused great harm to the ecological environment recently. Coal-based solid wastes, such as coal gangue and fly ash, are rich in valuable components, such as rare earth elements (REY), silicon dioxide, alkali metal oxides, [...] Read more.

The discharge and accumulation of coal-based solid waste have caused great harm to the ecological environment recently. Coal-based solid wastes, such as coal gangue and fly ash, are rich in valuable components, such as rare earth elements (REY), silicon dioxide, alkali metal oxides, and transition metal oxides, which can be used to synthesize various functional Si-based porous materials. This article systematically summarizes the physicochemical characteristics and general processing methods of coal gangue and fly ash and reviews the progress in the application of porous materials prepared from these two solid wastes in the fields of energy and environmental protection, including the following: the adsorption treatment of heavy metal ions, ionic dyes, and organic pollutants in wastewater; the adsorption treatment of CO₂, SO₂, NO_x, and volatile organic compounds in waste gas; the energy regeneration of existing resources, such as waste plastics, biomass, H₂, and CO; and the preparation of Li–Si batteries. Combining the composition, structure, and action mechanism of various solid-waste-based porous materials, this article points out their strengths and weaknesses in the above applications. Furthermore, ideas for improvements in the applications, performance improvement methods, and energy consumption reduction processes of typical solid-waste-based porous materials are presented in this article. These works will deepen our understanding of the application of solid-waste-based porous materials in wastewater treatment, waste gas treatment, energy regeneration, and other aspects, as well as providing assistance for the integration of new technologies into solid-waste-based porous material preparation industries, and providing new ideas for reducing and reusing typical Chinese solid waste resources. Full article

(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)

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