Recent Advances in Processing Technologies for Substance Extraction, Separation, and Enrichment

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Chemical Processes and Systems".

Deadline for manuscript submissions: closed (30 April 2024) | Viewed by 27668

Special Issue Editors


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Guest Editor
School of Chemistry, University of Melbourne, Parkville 3010, VIC, Australia
Interests: analytical science; separation science; materials science
Special Issues, Collections and Topics in MDPI journals

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Co-Guest Editor
Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112, USA
Interests: applied electrochemistry; thin film; separation process; extraction technology; metal recycling; corrosion; high entropy alloys; additive manufacturing

Special Issue Information

Dear Colleagues,

Extraction techniques, including liquid-phase extraction (LPE) and solid-phase extraction (SPE), have been among the dominant technologies in the separation of various types of substances and have found wide application in both lab-scale research and industrial production. With the development of new theories, materials, and techniques, significant advancements in these conventional technologies have been witnessed by scientists and engineers in recent decades. In particular, new modelling techniques for process optimization, novel extraction and separation systems, green solvents, and novel solid-phase materials (including mesoporous and nanostructured materials) for extraction have been developed and have found wide application, and fruitful achievements have been made which have contributed to scientific and technological advancements. Typical examples include experiments, modelling and simulation of electrochemical processes (deposition and separation), liquid–liquid extraction process for the optimization of mass transfer performance, the minimization of energy consumption in extraction, the application of green solvents and new ionic liquids, tailored materials for highly selective separation, membranes for SPE, extraction of natural products for nutritional, medical and health care application. The use of these new materials and technologies can effectively improve the mass transfer performance and separation factor, and facilitate environmental and/or user friendliness of separation, extraction, and enrichment processes, and improve the quality of life.

This Special Issue on “Recent Advances in Processing Technologies for Substance Extraction, Separation, and Enrichment” seeks high-quality works focusing on the latest advances in extraction technology for the separation, purification, and utilization of various natural and industrial resources and environmental protection. Topics include, but are not limited to:

  • Modelling of extraction and separation processes;
  • Low-temperature electrochemical processing for purification;
  • Green solvents for extraction and enrichment;
  • New materials and methods for solid- and liquid-phase extraction;
  • Application of extraction techniques for the separation and/or purification of elements and natural products;
  • Extraction of natural products;
  • Electrochemistry for metals, alloys, and nanostructure production and surface modification;
  • Aqueous and sol-gel processing of materials for energy and other applications.

Aims & Scope

The Special Issue is dedicated to the dissemination of novel methods for separation and purification in chemical and environmental areas by extraction technologies for homogeneous solutions and heterogeneous mixtures. This includes theoretical and experimental research outcomes relating to any separation and/or purification of all types of substances from natural or artificial resources for scientific and/or industrial applications. Articles, short communications, and reviews are all within the scope of consideration. Notes will ordinarily describe novel work of a limited nature or particularly significant work in progress. Articles of chromatographic separation methodology for pure analytical purposes are discouraged.

Dr. Yanlin Zhang
Dr. Prashant K. Sarswat
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • modelling extraction processes
  • green solvents for extraction
  • new materials for SPE
  • hydrometallurgy
  • natural products
  • environmental friendliness, low-temperature processing, materials electrochemistry
  • critical and rare earth metals

Published Papers (24 papers)

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20 pages, 1028 KiB  
Article
NADES-Based Extracts of Selected Medicinal Herbs as Promising Formulations for Cosmetic Usage
by Djurdja Ivkovic, Ilija Cvijetic, Aleksandra Radoicic, Jelena Stojkovic-Filipovic, Jelena Trifkovic, Maja Krstic Ristivojevic and Petar Ristivojevic
Processes 2024, 12(5), 992; https://doi.org/10.3390/pr12050992 - 13 May 2024
Viewed by 434
Abstract
As a functional extraction medium, natural deep eutectic solvents (NADESs) can dissolve various plant metabolites. Those solvents provide untapped potential for creating novel green extracts with distinctive phytochemical signatures and unique biological activities. This is particularly relevant given the rising need for eco-friendly [...] Read more.
As a functional extraction medium, natural deep eutectic solvents (NADESs) can dissolve various plant metabolites. Those solvents provide untapped potential for creating novel green extracts with distinctive phytochemical signatures and unique biological activities. This is particularly relevant given the rising need for eco-friendly and sustainable skin care products. The main aim of this work was to optimize the most efficient natural deep eutectic solvents (NADESs) for extracting bioactives from 18 medicinal herbs applicable to the cosmetic industry. Selection of the most potent herbs involved assessing their conventional extracts for tyrosinase inhibition, antioxidant activity, and keratinocyte cytotoxicity. Moreover, we analyzed the phenolic profile using ultra-high-pressure liquid chromatography/mass spectrometry (UHPLC/MS) and spectrophotometric assays such as total phenolic (TPC) and flavonoid content (TFC). Using the COSMO-RS method, we modeled the solubility of 12 phenolics in 64 virtual NADESs and selected the 7 most promising ones for further experimental validation. NADESs, including betaine-urea, betaine-proline, and betaine-lysine, were computationally chosen and demonstrated the highest levels of TPC and antioxidative capacity, as confirmed by in vitro assays. The proposed combination of NADES herbal extracts represents a promising natural constituent for the cosmetic industry. Full article
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14 pages, 6077 KiB  
Article
Comparative Analysis of Enzyme-, Ultrasound-, Mechanical-, and Chemical-Assisted Extraction of Biflavonoids from Ginkgo Leaves
by Anita Šalić, Lina Šepić, Iva Turkalj, Bruno Zelić and Dunja Šamec
Processes 2024, 12(5), 982; https://doi.org/10.3390/pr12050982 - 12 May 2024
Viewed by 518
Abstract
The biflavonoid extraction from ginkgo (Ginkgo biloba L.) leaves using solvent-based extraction with 70% ethanol, alone and in combination with enzyme-assisted, ultrasound-assisted, mechanical-assisted, and chemically assisted methods was investigated and the influence of extraction duration was explored. The total content of polyphenols, [...] Read more.
The biflavonoid extraction from ginkgo (Ginkgo biloba L.) leaves using solvent-based extraction with 70% ethanol, alone and in combination with enzyme-assisted, ultrasound-assisted, mechanical-assisted, and chemically assisted methods was investigated and the influence of extraction duration was explored. The total content of polyphenols, flavonoids, and phenolic acids in the extracts was determined spectrophotometrically, while individual biflavonoids were identified and quantified using HPLC-DAD. Amentoflavone, bilobetin, ginkgetin, isoginkgetin, and sciadopitysin were identified in all our extracts. Among these, sciadopitysin emerged as the most prevalent biflavonoid with an amount above 1 mg g−1 dw, followed by isoginkgetin. Comparative analysis of the extraction methods revealed that, except for chemically assisted extraction, similar levels of compounds were obtained after 45 min of extraction. However, enzymatic (EAE) and mechanical-assisted extraction (MAE) exhibited significantly higher individual (EAE: 19–41% higher; MAE: 22–67% higher) and total biflavonoid (EAE: 29% higher; MAE 50% higher) levels after just 5 min, suggesting their potential to abbreviate extraction duration and facilitate the efficient retrieval of target compounds. However, as extraction efficiency varies between individual biflavonoids, our findings also underscore the importance of considering specific compounds and extraction kinetics in the optimization of ginkgo leaf extraction processes. Full article
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12 pages, 7589 KiB  
Article
The Recovery of Sulfuric Acid in the Presence of Zr(IV) and Hf(IV) by Solvent Extraction with TEHA and Its Mixtures
by Xiaoxi Ding, Jiaxin Jiang, Yafang Zhao, Zaichao Dong, Lingyun Wang and Yang Liu
Processes 2024, 12(5), 940; https://doi.org/10.3390/pr12050940 - 6 May 2024
Viewed by 453
Abstract
The recovery of sulfuric acid in the presence of Zr(IV) and Hf(IV) was studied via solvent extraction using TEHA (tri-2-ethylhexyl amine) and its mixtures. A solidification phenomenon occurred in the loaded organic phase when a single TEHA was employed in the extraction of [...] Read more.
The recovery of sulfuric acid in the presence of Zr(IV) and Hf(IV) was studied via solvent extraction using TEHA (tri-2-ethylhexyl amine) and its mixtures. A solidification phenomenon occurred in the loaded organic phase when a single TEHA was employed in the extraction of 1 to 5 M H2SO4. Octanol, decanol and TBP (tri butyl phosphate) were mixed with TEHA, separately, to prevent the solidification of sulfuric-acid-loaded organic. Due to the relatively high aqueous solubility of octanol and decanol, the mixture of TEHA + TBP was selected as the optimal system for the extraction of H2SO4. Simulated counter-current extraction and stripping experiments were performed on the basis of the McCabe–Thiele diagrams, indicating that sulfuric acid could be reduced by TEHA + TBP from 4.2 to around 0.5 M without Zr(IV) and Hf(IV) extraction and recovered by its complete stripping with water. The proposed sulfuric acid recovery step would contribute to the completion of the closed-circuit of the Zr(IV) and Hf(IV) separation process in our previous work and help to re-separate the remaining Zr(IV) and Hf(IV) in the sulfuric acid stripping solution. Full article
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14 pages, 4783 KiB  
Article
Solvent Extraction of Gold(III) by 2-Ethylhexanol and Modeling of Facilitated Transport across a Supported Liquid Membrane
by Francisco Jose Alguacil and Jose Ignacio Robla
Processes 2024, 12(4), 771; https://doi.org/10.3390/pr12040771 - 11 Apr 2024
Viewed by 609
Abstract
The solvent extraction of gold(III) by undiluted 2-ethylhexanol or dissolved in toluene from a HCl solution has been investigated in this paper. The numerical analysis of gold distribution data suggests the formation of HAuCl4·L and HAuCl4·2L (L = 2-ethylhexanol) [...] Read more.
The solvent extraction of gold(III) by undiluted 2-ethylhexanol or dissolved in toluene from a HCl solution has been investigated in this paper. The numerical analysis of gold distribution data suggests the formation of HAuCl4·L and HAuCl4·2L (L = 2-ethylhexanol) species in the organic phase, with formation constants K11 = 38 and K12 = 309, respectively. The results derived from gold(III) distribution have been implemented in a solid-supported liquid membrane system. The influence of several variables on gold transport has been considered: feed and receiving phases’ stirring speeds, HCl and gold concentrations in the feed phase, and carrier concentration in the membrane phase as well as the presence of base metals (Fe, Cu, Ni) and platinum-group metals (PGMs) in the feed phase. Gold transport is influenced by the stirring speed of the feed phase and the variation in HCl and gold (feed phase) and carrier (membrane phase) concentrations. Also, diffusional resistances to mass transfer are estimated, and the contribution of each resistance to gold transport is estimated. Gold is recovered as zero-valent nanoparticles. Full article
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13 pages, 1689 KiB  
Article
Studies on Reactive Extraction of Itaconic Acid from Fermentation Broths
by Alexandra Cristina Blaga, Lenuta Kloetzer, Dan Cascaval, Anca-Irina Galaction and Alexandra Tucaliuc
Processes 2024, 12(4), 725; https://doi.org/10.3390/pr12040725 - 3 Apr 2024
Viewed by 502
Abstract
Itaconic acid is a high-value organic acid that serves as a platform molecule in different industries. This research focuses on the separation of itaconic acid using reactive extraction as a sustainable and efficient method for acid recovery from fermentation broth. Itaconic acid was [...] Read more.
Itaconic acid is a high-value organic acid that serves as a platform molecule in different industries. This research focuses on the separation of itaconic acid using reactive extraction as a sustainable and efficient method for acid recovery from fermentation broth. Itaconic acid was produced through fungal fermentation processes involving Aspergillus terreus ATCC® 32588™, obtaining a concentration of 47 g/L in the final broths. For the reactive extraction system, the organic phase included tri-n-octylamine as an extractant dissolved in dichloromethane or n-heptane and 1-octanol as a phase modifier. The effect of the main influencing factors (pH of the aqueous phase, extractant concentrations in the organic phase, and the addition of 1-octanol) on extraction efficiency was investigated. The highest extraction degree (97%) was achieved using an organic phase with tri-n-octylamine dissolved in dichloromethane and with 20% 1-octanol. Conversely, in the reactive extraction system with tri-n-octylamine dissolved in n-heptane and 20% 1-octanol, the extraction efficiency reached 67%. This finding suggests a promising separation system that is less toxic for microorganisms. The study results highlight the feasibility of employing reactive extraction systems for the direct separation of itaconic acid. Full article
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18 pages, 2037 KiB  
Article
Preliminary Study on the Chemical and Biological Properties of Propolis Extract from Stingless Bees from the Northern Region of Brazil
by Lindalva Maria de Meneses Costa Ferreira, Poliana Dimsan Queiroz de Souza, Rayanne Rocha Pereira, Edilene Oliveira da Silva, Wagner Luiz Ramos Barbosa, José Otávio Carréra Silva-Júnior, Attilio Converti and Roseane Maria Ribeiro-Costa
Processes 2024, 12(4), 700; https://doi.org/10.3390/pr12040700 - 29 Mar 2024
Cited by 1 | Viewed by 582
Abstract
Natural products are historically regarded as the main sources of bioactive compounds to fight the most diverse diseases; among them, propolis deserves to be highlighted due to several biological activities, such as antioxidant, anti-inflammatory, healing, antibacterial and antileishmanial activity. In this study, the [...] Read more.
Natural products are historically regarded as the main sources of bioactive compounds to fight the most diverse diseases; among them, propolis deserves to be highlighted due to several biological activities, such as antioxidant, anti-inflammatory, healing, antibacterial and antileishmanial activity. In this study, the antioxidant and antipromastigote activities and the cytotoxicity of propolis of the Scaptotrigona aff. postica stingless bee were evaluated. Propolis extract was analyzed by infrared spectroscopy, thermogravimetry and spectrophotometry for total polyphenols and flavonoid contents. Antioxidant activity was assessed spectrophotometrically by the DPPH, ABTS and FRAP methods, while antipromastigote activity and cytotoxicity were assessed by the MTT assay. The infrared spectra showed the characteristic bands of both phenols and alcohols. The thermogravimetry study revealed two events and thermal stability around 370 °C, while differential scanning calorimetry showed two endothermic events and an exothermic event. Total polyphenol and flavonoid contents were 21.29 ± 0.003 mg/g and 8.17 ± 0.00 mg/g, respectively, and the antioxidant activities identified by the DPPH, ABTS and FRAP methods were 910.09 ± 0.0264 µM Trolox (IC50 18.9 ± 0.01 µg/mL), 859.97 ± 0.0854 µM Trolox (IC50 692 ± 0.01 µg/mL) and 1613.67 ± 0.2610 µM Trolox (IC50 80 ± 0.1 µg/mL), respectively. The satisfactory antioxidant activity of propolis can be related to the high content of phenolic compounds, which adds value to this product and can contribute to the development of meliponiculture in the Brazilian state of Pará. The propolis extract caused a toxic effect on promastigote forms of Leishmania amazonensis at all concentrations tested, with an IC50 value of 1.50 µg/mL and a statistically significant difference compared to the negative control (p < 0.001). These results show that the propolis extract from S. postica bees may be a promising alternative for treatment against promastigote forms of L. amazonensis. Full article
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24 pages, 665 KiB  
Article
Efficiency of Supercritical CO2 and Ultrasound-Assisted Extraction Techniques for Isolation of Bioactive Molecules from Sea Buckthorn (Elaeagnus rhamnoides (L.) A. Nelson) Berry Oils and Cakes
by Patricija Čulina, Sandra Balbino, Stela Jokić, Verica Dragović-Uzelac and Sandra Pedisić
Processes 2024, 12(4), 698; https://doi.org/10.3390/pr12040698 - 29 Mar 2024
Viewed by 508
Abstract
This study compared the efficiency of advanced supercritical CO2 extraction (SC-CO2) and conventional Soxhlet extraction (SE) in the isolation of lipophilic bioactive molecules (BAMs) from the oils of different sea buckthorn (SB) berries (Leikora and Ascola). A SB cake, a [...] Read more.
This study compared the efficiency of advanced supercritical CO2 extraction (SC-CO2) and conventional Soxhlet extraction (SE) in the isolation of lipophilic bioactive molecules (BAMs) from the oils of different sea buckthorn (SB) berries (Leikora and Ascola). A SB cake, a valuable by-product of oil extraction, was analyzed for phenolic compounds and antioxidant activity (AA). For this purpose, ultrasound-assisted extraction (UAE) with 70% (v/v) ethanol was optimized, and the following optimal UAE conditions were determined: ultrasonic power of 60%, temperature of 50 °C, and extraction time of 20 min. The individual BAMs in the oils and cake extracts were analyzed chromatographically, while the AAs were determined using the ORAC method. The oils extracted with SC-CO2 had a higher content of lipophilic BAMs and a higher AA value than the oils extracted with SE. Palmitic and palmitoleic acids, β-sitosterol, and α-tocopherol dominated the Leikora oil, while a higher content of oleic, linoleic, and α-linolenic acids and carotenoids was found in the Ascola oil. The highest phenolic content was found in the Ascola cake, with the flavonols isorhamnetin-3-hexoside, isorhamnetin-3-rutinoside, and quercetin-3-glucoside being the most abundant. Oil and cake extracts of the Ascola variety also had a higher AA. Full article
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17 pages, 1276 KiB  
Article
Antioxidant Activity of Carob Tree (Ceratonia siliqua L.) Leaf Extracts Obtained by Advanced Extraction Techniques
by Ena Cegledi, Erika Dobroslavić, Zoran Zorić, Maja Repajić and Ivona Elez Garofulić
Processes 2024, 12(4), 658; https://doi.org/10.3390/pr12040658 - 26 Mar 2024
Viewed by 578
Abstract
Carob (Ceratonia siliqua L.) is a widely spread Mediterranean evergreen tree whose plant parts are rich in bioactive compounds with potential for application in functional food production. Carob leaves are the least explored part of the plant, and the main compounds of [...] Read more.
Carob (Ceratonia siliqua L.) is a widely spread Mediterranean evergreen tree whose plant parts are rich in bioactive compounds with potential for application in functional food production. Carob leaves are the least explored part of the plant, and the main compounds of interest are polyphenols. Advanced extraction techniques, such as pressurized liquid (PLE), microwave-assisted (MAE) and ultrasound-assisted (UAE) extraction have not been sufficiently explored for their potential in extracting these compounds. Therefore, the aim of this paper was to optimize the parameters (temperature and time) of PLE, MAE and UAE of carob leaf polyphenols, characterize the individual compounds by ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS2) and determine the antioxidant activity of the extracts. The optimal temperature and time were 160 °C/5 min for PLE, resulting in a total phenolic content of 68.21 mg of gallic acid equivalents (GAE) g−1. For MAE and UAE, the optimal conditions were 70 °C/10 min, under which total phenolic contents of 78.80 and 55.98 mg GAE g−1 were achieved, respectively. A total of 26 compounds, represented mainly by myricetin, quercetin-3-rhamnoside and gallic acid, were identified in extracts obtained by all three extraction techniques. All extracts showed high antioxidant activity (0.46–1.05 and 0.50–0.58 mmol TE g−1 for FRAP and DPPH, respectively), which correlated with the polyphenolic content and was affected by the concentration of ascorbic acid (0.03–0.52 mg mL−1), confirming that carob leaf extracts obtained by advanced extraction possess high potential for application in functional food products. Full article
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16 pages, 2604 KiB  
Article
Comparing Quality and Functional Properties of Protein Isolates from Soybean Cakes: Effect of De-Oiling Technologies
by Giulia Cestonaro, Rodrigo Gonzalez-Ortega, Antonella L. Grosso, Ksenia Morozova, Giovanna Ferrentino, Matteo Scampicchio and Enrico Costanzo
Processes 2024, 12(3), 600; https://doi.org/10.3390/pr12030600 - 17 Mar 2024
Viewed by 1093
Abstract
Driven by growing concerns about food supply and the environment, research on alternative protein sources has become increasingly important. In this context, de-oiled seed cakes, particularly soybean cakes, have emerged as a promising option. However, the conventional methods, such as organic solvent extraction, [...] Read more.
Driven by growing concerns about food supply and the environment, research on alternative protein sources has become increasingly important. In this context, de-oiled seed cakes, particularly soybean cakes, have emerged as a promising option. However, the conventional methods, such as organic solvent extraction, from which these cakes are obtained present several limitations. This study aims to evaluate the efficiency of supercritical fluid extraction (SFE) as an alternative method for de-oiling soybean seeds and obtaining related protein isolates. By using SFE for de-oiling, it was possible to achieve 19% more protein isolates from soybean cakes than the conventional de-oiling method using hexane. Moreover, protein isolates from the SFE de-oiled cake reported significantly improved (p < 0.05) emulsifying abilities and water absorption capacity. Gel electrophoresis and differential scanning calorimetry indicated the presence of a higher concentration of proteins in their native state in the SFE de-oiled flour. Finally, results from the sulfhydryl group content, surface hydrophobicity, and protein dispersibility index also supported these conclusions. The SFE process produced de-oiled soybean cakes with superior functional characteristics and lower environmental impact. Thus, this study provided important information for the food industry to develop more sustainable and healthier production methods. Full article
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19 pages, 5485 KiB  
Article
Seeking Optimal Extraction Method for Augmenting Hibiscus sabdariffa Bioactive Compounds and Antioxidant Activity
by Athanasia Kourelatou, Theodoros Chatzimitakos, Vassilis Athanasiadis, Konstantina Kotsou, Ioannis Makrygiannis, Eleni Bozinou and Stavros I. Lalas
Processes 2024, 12(3), 581; https://doi.org/10.3390/pr12030581 - 14 Mar 2024
Viewed by 853
Abstract
The dried flowers of Hibiscus sabdariffa (HS), available worldwide, have various applications in both non-medicinal and medicinal fields. The growing global interest in the health benefits of HS is linked to its potential prevention or management of non-communicable diseases. The aim of this [...] Read more.
The dried flowers of Hibiscus sabdariffa (HS), available worldwide, have various applications in both non-medicinal and medicinal fields. The growing global interest in the health benefits of HS is linked to its potential prevention or management of non-communicable diseases. The aim of this research was to find the optimal extraction method that ensures the maximum yield of multiple beneficial bioactive components, such as polyphenols, anthocyanins, vitamin C, β-carotene, antioxidant activity, free radical scavenging activity DPPH and ferric reducing antioxidant power (FRAP). To this end, stirring, pulsed electric field, and ultrasound-assisted extraction were evaluated, either alone or in combination. Under optimized extraction conditions, the obtained extract exhibited an elevated total polyphenol content (37.82 mg of gallic acid equivalents/g dry weight (dw)), total anthocyanin content (610.42 μg of cyanidin equivalents/g dw), total carotenoids content (921.84 μg of β-carotene equivalents/g dw), and ascorbic acid content (507.44 mg/100 g dw). Remarkably, the extracts exhibited strong antioxidant properties (487.51 μmol of ascorbic acid equivalents (AAE)/g dw and 243.42 μmol AAE/g dw as evidenced by FRAP and DPPH assays, respectively). This research advances the parameters that should be employed to produce the optimal and nutritionally enhanced HS flower extracts, that can be used in the commercial sector. Full article
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18 pages, 2486 KiB  
Article
Recovery of Strategic Metals from Waste Printed Circuit Boards with Deep Eutectic Solvents and Ionic Liquids
by Urszula Domańska, Anna Wiśniewska and Zbigniew Dąbrowski
Processes 2024, 12(3), 530; https://doi.org/10.3390/pr12030530 - 6 Mar 2024
Viewed by 756
Abstract
The recycling of metals from waste printed circuit boards (WPCBs) has been presented as a solid–liquid extraction process using two deep eutectic solvents (DESs) and four ionic liquids (ILs). The extraction and separation of Cu(II), Ag(I), and other metals, such as Al(III), Fe(II), [...] Read more.
The recycling of metals from waste printed circuit boards (WPCBs) has been presented as a solid–liquid extraction process using two deep eutectic solvents (DESs) and four ionic liquids (ILs). The extraction and separation of Cu(II), Ag(I), and other metals, such as Al(III), Fe(II), and Zn(II), from the solid WPCBs (after the physical, mechanical, and thermal pre-treatments) with different solvents are demonstrated. Two popular DESs were used to recover valuable metal ions: (1) choline chloride + malonic acid, 1:1, and (2) choline chloride + ethylene glycol, 1:2. The extraction efficiencies of DES 1 after two extraction and two stripping stages were only 15.7 wt% for Cu(II) and 17.6 wt% for Ag(I). The obtained results were compared with those obtained with four newly synthetized ILs as follows: didecyldimethylammonium propionate ([N10,10,1,1][C2H5COO]), didecylmethylammonium hydrogen sulphate ([N10,10,1,H][HSO4]), didecyldimethylammonium dihydrogen phosphate ([N10,10,1,1][H2PO4]), and tetrabutylphosphonium dihydrogen phosphate ([P4,4,4,4][H2PO4]). Various additives, such as didecyldimethyl ammonium chloride surfactant, DDACl; hydrogen peroxide, H2O2; trichloroisocyanuric acid, TCCA; and glycine or pentapotassium bis(peroxymonosulphate) bis(sulphate), PHM, were used with ILs during the extraction process. The solvent concentration, quantity of additivities, extraction temperature, pH, and solid/liquid, as well as organic/water ratios, and the selectivity and distribution ratios were described for all of the systems. The utilization of DESs and the new ILs with different additives presented in this work can serve as potential alternative extractants. This will help to compare these extractants, additives, extraction efficiency, temperature, and time of extraction with those of others with different formulas and procedures. The metal ion content in aqueous and stripped organic solutions was determined by the ICP-MS or ICP-OES methods. The obtained results all show that solvent extraction can successfully replace traditional hydrometallurgical and pyrometallurgical methods in new technologies for the extraction of metal ions from a secondary electronic waste, WPCBs. Full article
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14 pages, 2651 KiB  
Article
Extraction Kinetics of Pyridine, Quinoline, and Indole from the Organic Phase with Natural Deep Eutectic Solvents and Separation Study Using a Centrifugal Extractor
by Dmitriy V. Lobovich, Inna V. Zinov’eva, Nikita A. Milevskii, Artak E. Kostanyan, Yulia A. Zakhodyaeva and Andrey A. Voshkin
Processes 2024, 12(3), 488; https://doi.org/10.3390/pr12030488 - 28 Feb 2024
Viewed by 598
Abstract
In this study, the kinetics of extracting pyridine, quinoline, and indole from model fuels using natural deep eutectic solvents (NaDES) composed of carboxylic acids, xylitol, and water were investigated under static conditions. This research marks the first examination of extraction kinetics in this [...] Read more.
In this study, the kinetics of extracting pyridine, quinoline, and indole from model fuels using natural deep eutectic solvents (NaDES) composed of carboxylic acids, xylitol, and water were investigated under static conditions. This research marks the first examination of extraction kinetics in this context. The key kinetic parameters of the extraction process were identified. Notably, it was observed that the mass transfer coefficient for indole was in the range of 3.4 × 10−6 to 1.2 × 10−6, depending on NaDES. That is significantly lower, by an order of magnitude, than for pyridine and quinoline under identical experimental conditions. The study revealed that, under specific conditions, where thermodynamic equilibrium for indole cannot be reached, it becomes possible to achieve kinetic separation of the components. The presented experimental data obtained on a centrifugal extractor showed a decrease in the degree of indole extraction with increasing flow: Extraction efficiency decreased from 63% at a flow rate of 0.05 L/h to 18% at 0.8 L/h. Moreover, the research indicated that, during indole extraction, the mass transfer coefficient in a centrifugal extractor was 1.3 × 10−4, which is two orders of magnitude higher than under static conditions. The study underscores the potential utility of the proposed extraction systems based on environmentally friendly NaDES, comprised of carboxylic acids and xylitol, for the kinetic separation of various classes of heterocyclic compounds. Overall, the research provides valuable insights into the kinetics of extraction and the potential applications of ‘green’ NaDES in the separation of heterocyclic compounds from organic liquids. Full article
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15 pages, 1006 KiB  
Article
Correlations between a Friabilin Content Indicator and Selected Physicochemical and Mechanical Properties of Wheat Grain for Processing Suitability Assessment
by Zdzisław Kaliniewicz, Agnieszka Markowska-Mendik, Małgorzata Warechowska, Seweryn Lipiński and Sebastian Gasparis
Processes 2024, 12(2), 398; https://doi.org/10.3390/pr12020398 - 17 Feb 2024
Viewed by 704
Abstract
A new approach to determining the friabilin content of wheat grain was proposed. Electropherograms were taken, and the intensity of the friabilin bands was compared in the analyzed wheat cultivars and the cv. Chinese Spring. The friabilin content indicator was calculated in the [...] Read more.
A new approach to determining the friabilin content of wheat grain was proposed. Electropherograms were taken, and the intensity of the friabilin bands was compared in the analyzed wheat cultivars and the cv. Chinese Spring. The friabilin content indicator was calculated in the grain of 17 common wheat cultivars, which differed mostly in their crude protein content and hardness index (HI). The basic properties of the kernels were measured in each wheat cultivar, and the correlations between the measured parameters and the friabilin content indicator were determined. In the analyzed wheat cultivars, the friabilin content indicator ranged from around 0.21 to around 0.77. This indicator was significantly correlated with the kernel length, thickness, mass, vitreousness, HI, and rupture force. The strongest correlation was observed between the friabilin content indicator and kernel length. An increase in the mean kernel length from around 5.4 mm to around 8.0 mm decreased the friabilin content indicator by approximately 51%. After the mean kernel length had been calculated in a given wheat cultivar, a certain value of the friabilin content indicator could be ascribed to this cultivar, and the energy consumption during grain grinding or milling could be partly predicted. In the group of analyzed wheat cultivars, the process of grain grinding would be the most energy-intensive in the cvs. Ceres, SMH200, and SMH214 and the least energy-intensive in the cvs. Chinese Spring, Julius, and Askalon. Full article
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18 pages, 4774 KiB  
Article
Prospects of Processing Tungsten Ores from the Akchatau Deposit
by Bolotpay Baimbetov, Gulnara Moldabayeva, Akmaral Yeleuliyeva, Saltanat Jumankulova, Akbota Taimassova, Zhanargul Adilzhan, Rinat Baisultanov, Elena Yakob and Valery Serikbayev
Processes 2024, 12(1), 77; https://doi.org/10.3390/pr12010077 - 28 Dec 2023
Cited by 1 | Viewed by 806
Abstract
An overview of the composition of wolframite ores of the Akchatau deposit and the technologies for processing concentrates using NaOH and Na2CO3 by hydro- and pyrometallurgical methods is given, and the disadvantages associated with both the technology and the equipment [...] Read more.
An overview of the composition of wolframite ores of the Akchatau deposit and the technologies for processing concentrates using NaOH and Na2CO3 by hydro- and pyrometallurgical methods is given, and the disadvantages associated with both the technology and the equipment are noted. To develop a technology for processing Akchatau wolframite concentrates, samples of ore materials were taken, the chemical and mineralogical composition of the samples was studied, and enrichment was carried out to obtain rich concentrates. The kinetics of the sintering of the wolframite concentrate with soda was investigated, the dependences of the degree of transformation of the tungsten minerals into sodium tungstate were obtained, and the rate constants, the order of the reaction, and the values of the apparent activation energy were calculated. The results of sintering an enlarged sample of wolframite concentrate with soda in a muffle furnace are presented. After the subsequent leaching, studies were carried out to purify the obtained solutions of sodium tungstate from the impurities while eliminating the operations of the neutralizing solutions through the use of electrodialysis with an MK-40 cation-exchange membrane. The scheme of processing the wolframite ores of Akchatau is proposed. Full article
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12 pages, 2323 KiB  
Article
Experimental Study on Enrichment of Indole in Wash Oil by a Combined Process of Extraction and Re-Extraction
by Su Jin Kim
Processes 2023, 11(11), 3097; https://doi.org/10.3390/pr11113097 - 27 Oct 2023
Viewed by 795
Abstract
Wash oil, one of the by-products of coal tar distillation, contains useful nitrogen heterocyclic compounds (NHC) such as indole (IN), which is used as a raw material for perfume, essential amino acid, and pharmaceuticals. In this study, as a [...] Read more.
Wash oil, one of the by-products of coal tar distillation, contains useful nitrogen heterocyclic compounds (NHC) such as indole (IN), which is used as a raw material for perfume, essential amino acid, and pharmaceuticals. In this study, as a pre-treatment step for purification of IN, which is about 5.75% contained in wash oil, the enrichment of IN in wash oil was examined by combining formamide extraction (FE) and n-hexane re-extraction (HRE). The raw material for the re-extraction was a mixture of the preceding formamide extract phase acquired through batchwise 5-stage co-current extraction trial under fixed FE condition. As the 5-stage FE and HRE progressed, the IN yield based on IN in the wash oil was approximately 73.3%, and the IN concentration in the raffinate oil acquired from the re-extraction run was highly enriched to about 92.4%. In addition, the IN enrichment efficiency of the FE-HRE combined process (FHC) employed in this study was compared with methanol extraction (ME)-hexane re-extraction (HRE) combination (MHC). Full article
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12 pages, 1808 KiB  
Article
Extraction and Purification of Kiwifruit Seed Oil Using Three-Phase Partitioning: An Efficient and Value-Adding Method for Agro-Industrial Residue Utilization
by Bangfu Liu, Xiufang Li, Qingchun Liu and Zhijian Tan
Processes 2023, 11(9), 2581; https://doi.org/10.3390/pr11092581 - 29 Aug 2023
Viewed by 1182
Abstract
Kiwifruit seeds are usually discarded as waste in the kiwifruit processing industry. However, kiwifruit seeds are rich in oil, which implies their value as a potential resource. Therefore, three-phase partitioning (TPP) using ammonium sulfate and n-butanol has been developed to extract kiwifruit seed [...] Read more.
Kiwifruit seeds are usually discarded as waste in the kiwifruit processing industry. However, kiwifruit seeds are rich in oil, which implies their value as a potential resource. Therefore, three-phase partitioning (TPP) using ammonium sulfate and n-butanol has been developed to extract kiwifruit seed oil (KSO) from discarded kiwifruit seeds. The factors influencing the extraction process have been investigated. The highest extraction yield of 36.06% for KSO was obtained under the following conditions: an extraction time of 18 h, a liquid-solid ratio of 4:1, an amount of ammonium sulfate of 28.5 wt%, and a phase ratio (top phase/bottom phase) of 1/1. The composition of obtained KSO was analyzed by gas chromatography-mass spectrometry (GC-MS), and the results indicated the high content of α-linolenic acid. This simple and low-cost method can be used as an efficient approach for utilizing the value of kiwifruit seeds. Full article
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11 pages, 1784 KiB  
Article
Separation of Rare Earth Elements in Multistage Extraction Columns in Chromatography Mode: Experimental Study and Mathematical Simulation
by Artak E. Kostanyan, Vera V. Belova, Yulia V. Tsareva and Maria M. Petyaeva
Processes 2023, 11(6), 1757; https://doi.org/10.3390/pr11061757 - 9 Jun 2023
Cited by 1 | Viewed by 1745
Abstract
The application of liquid–liquid chromatography principles to solvent extraction processes in hydrometallurgy can greatly simplify rare earth metal separation technologies by separating multicomponent mixtures in one technological operation. In this study, the chromatographic separation of rare earth elements (REEs) in multistage extraction columns [...] Read more.
The application of liquid–liquid chromatography principles to solvent extraction processes in hydrometallurgy can greatly simplify rare earth metal separation technologies by separating multicomponent mixtures in one technological operation. In this study, the chromatographic separation of rare earth elements (REEs) in multistage extraction columns was experimentally studied under conditions of impulse sample injection—single and multiple loading of large volumes of metal salt solution into the installation. The results obtained showed the feasibility of operating sieve plate extraction columns in the liquid–liquid chromatography mode. A closed-loop recycling technology is proposed for the separation of rare earth elements in multistage extraction columns operating in the liquid–liquid chromatography mode. For further development and industrial implementation of this technology, experimental studies should be conducted on intensified multistage extraction columns, such as sectioned columns with agitators and vibrating plate columns. Computer simulation of the chromatographic separation of rare earth elements by closed-loop recycling liquid–liquid chromatography was carried out. Full article
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17 pages, 2286 KiB  
Article
Green and Cost-Effective Separation of Cadmium from Base Metals in Chloride Medium with Halide-Loaded Anion Exchanger
by Yanlin Zhang, Xiaofei Duan, Chaoquan Hu, Guanshang Du and Yong Wang
Processes 2023, 11(4), 1051; https://doi.org/10.3390/pr11041051 - 31 Mar 2023
Viewed by 1439
Abstract
A novel strategy for the separation of cadmium from base metals in chloride medium by anion exchange based on the formation of cadmium halo-complexes is presented in this article. Instead of using excess Br or I in the feed solution, the [...] Read more.
A novel strategy for the separation of cadmium from base metals in chloride medium by anion exchange based on the formation of cadmium halo-complexes is presented in this article. Instead of using excess Br or I in the feed solution, the anion exchange resin or fibre was first preloaded with Br or I for Cd2+ adsorption from Cl solution. Thus, the consumption of iodide or bromide was minimized while promising high adsorption stability of Cd2+. The adsorption thermodynamics and kinetics of Cd2+ were studied. The adsorption thermodynamics results were processed with Langmuir and Freundlich models and adsorption kinetics results were treated with Pseudo first order model, Pseudo second order model and intraparticle diffusion model. The adsorption mechanism was studied with the aid of FTIR and elemental analysis. Three strategies were applied for the stripping of Cd2+, including the use of water for disequilibrating its halo-complex formation, the formation of positively charged species with ammonia, and the formation of positively charged chelate with multidentate ligand ethylenediamine. On the bases of these results, separation performance was investigated with strongly basic anion exchange resin and fibre, and it was shown that Cd2+ can be efficiently separated from base metals in a wide range of acidity, and that pure Cd2+ solution can be obtained, thus providing a robust, environmentally friendly, and economic technology for its separation. Full article
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15 pages, 4051 KiB  
Article
Assessing and Improving Biooxidation for Acid Generation and Rare Earth Element Extraction
by Michael L. Free, Joel K. Ilunga, Prasenjit Podder and Prashant K. Sarswat
Processes 2023, 11(4), 1005; https://doi.org/10.3390/pr11041005 - 26 Mar 2023
Cited by 1 | Viewed by 992
Abstract
Microorganisms (Acidithiobacillus ferrooxidanns) are effective in oxidizing ferrous ions that can be used to oxidize pyrite and produce sulfuric acid. Many coal waste resources contain significant concentrations of rare earth elements (REE) and critical materials (CM) that can be extracted using [...] Read more.
Microorganisms (Acidithiobacillus ferrooxidanns) are effective in oxidizing ferrous ions that can be used to oxidize pyrite and produce sulfuric acid. Many coal waste resources contain significant concentrations of rare earth elements (REE) and critical materials (CM) that can be extracted using sulfuric acid. These coal waste resources often contain significant concentrations of pyrite, which if not utilized or removed present a future environmental liability for potential acid mine drainage. Thus, the combination of pyrite and REE/CM in coal waste provides a significant resource opportunity for sulfuric acid generation that can be utilized using biooxidation. In addition, the pyrite concentrate used for acid generation also contains REE/CM content that is released during biooxidation of the pyrite concentrate that augments the REE/CM release from the main ore being leached with the acid generated from the pyrite. Thus, this approach provides a very significant environmental advantage as well as augmented REE/CM recovery. Although there are many studies associated with biooxidation in relation to mineral oxidation, there is a lack of information regarding the effects of operating parameters on biooxidation performance and optimization for practical applications. In this study, findings from research in assessing and improving biooxidation for acid generation for REE/CM extraction are presented. Results show that bacteria can very effectively and efficiently oxidize ferrous ions to ferric ions, which oxidize pyrite to produce acid for REE/CM extraction. The factors that showed significant impact on biooxidation performance include air flow rate, stirring speed, residence time, solids concentration, and temperature. The dominance of Leptospirillum ferriphilum species was noted in the bioreactor after a prolonged period of operation, although Acidithiobacillus ferrooxidanns was used in the beginning. Full article
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10 pages, 1832 KiB  
Article
Desilication of Sodium Aluminate Solutions from the Alkaline Leaching of Calcium-Aluminate Slags
by James Malumbo Mwase and Jafar Safarian
Processes 2022, 10(9), 1769; https://doi.org/10.3390/pr10091769 - 3 Sep 2022
Cited by 2 | Viewed by 2138
Abstract
The desilication of sodium aluminate solutions prior to precipitation of aluminum tri-hydroxides is an essential step in the production of high purity alumina for aluminum production. This study evaluates the desilication of sodium aluminate solutions derived from the leaching of calcium-aluminate slags with [...] Read more.
The desilication of sodium aluminate solutions prior to precipitation of aluminum tri-hydroxides is an essential step in the production of high purity alumina for aluminum production. This study evaluates the desilication of sodium aluminate solutions derived from the leaching of calcium-aluminate slags with sodium carbonate, using CaO, Ca(OH)2, and MgO fine particles. The influence of the amount of CaO used, temperature, and comparisons with Ca(OH)2 and MgO were explored. Laboratory scale test work showed that the optimal conditions for this process were using 6 g/L of CaO at 90 °C for 90 min. This resulted in 92% of the Si being removed with as little as 7% co-precipitation of Al. The other desilicating agents, namely Ca(OH)2 and MgO, also proved effective in removing Si but at slower rates and higher amounts of Al co-precipitated. The characteristics of solid residue obtained after the process indicated that the desilication is via the formation of hydrogarnet, Grossular, and hydrotalcite dominant phases for CaO, Ca(OH)2 and MgO agents, respectively. Full article
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Review

Jump to: Research

20 pages, 1071 KiB  
Review
The Use of Immobilised Enzymes for Lipid and Dairy Processing and Their Waste Products: A Review of Current Progress
by Fawzih Alzahrani, Taiwo O. Akanbi, Christopher J. Scarlett and Alberta N. A. Aryee
Processes 2024, 12(4), 634; https://doi.org/10.3390/pr12040634 - 22 Mar 2024
Viewed by 897
Abstract
The use of edible oils and fats in dairy products is becoming increasingly important in the food industry because of their complementary functional properties. Most of these products are produced using food-grade enzymes as processing aids because processes involving enzymes are considered mild [...] Read more.
The use of edible oils and fats in dairy products is becoming increasingly important in the food industry because of their complementary functional properties. Most of these products are produced using food-grade enzymes as processing aids because processes involving enzymes are considered mild and environmentally friendly for regulatory purposes. The poor stability and recovery of enzymes in their native state limit their performance, and to enhance their activity, stability, and reusability, enzymes are often immobilised—a process that involves attaching them to a solid support. Additionally, immobilisation enables enzymes to selectively target specific substrates or products, making them highly efficient. These features have led to the increased use of immobilised enzymes in dairy and lipid processing and enzymes have been used to produce a broad range of products such as whey protein concentrates and isolates, peptide–lipid conjugates, lipid concentrates, structured lipids, and human milk fat substitutes. Therefore, this article reviews the current progress on different enzyme preparations and their use in lipid and dairy processing. It also summarises opportunities in enzyme-catalysed valorisation of dairy and lipid waste streams with the ultimate goals of sustainable food production and reductions in waste. Full article
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37 pages, 11737 KiB  
Review
Hollow Fiber Membrane Modification by Interfacial Polymerization for Organic Solvent Nanofiltration
by Abdulaziz Y. Alammar, Seung-Hak Choi and Maria Giovanna Buonomenna
Processes 2024, 12(3), 563; https://doi.org/10.3390/pr12030563 - 13 Mar 2024
Viewed by 1449
Abstract
Hollow fiber (HF) organic solvent nanofiltration (OSN) membranes have recently attracted significant interest in the field of membrane technology. Their popularity stems from comparative advantages, such as high packing density, fouling resistance, and easier scalability for larger applications, unlike flat-sheet/spiral-wound OSN membranes, which [...] Read more.
Hollow fiber (HF) organic solvent nanofiltration (OSN) membranes have recently attracted significant interest in the field of membrane technology. Their popularity stems from comparative advantages, such as high packing density, fouling resistance, and easier scalability for larger applications, unlike flat-sheet/spiral-wound OSN membranes, which may present challenges in these aspects. The combination of interfacial polymerization (IP) and HF configuration has opened up new opportunities for developing advanced membranes with enhanced separation performance that can be tailored for various OSN applications. The objective of this review is to discuss the latest advancements in developing thin film composite (TFC) HF membranes, with a focus on the IP method. Novel materials and processes are discussed in detail, emphasizing the fabrication of greener, interfacially polymerized HF OSN membranes. In addition, the commercial viability and limitations of TFC HF membranes are highlighted, providing perspectives on future research directions. Full article
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30 pages, 1944 KiB  
Review
Pulsed Electric Field Technology for Recovery of Proteins from Waste Plant Resources and Deformed Mushrooms: A Review
by Ramya Ramaswamy, Sivaneasan Bala Krishnan and Susanna Su Jan Leong
Processes 2024, 12(2), 342; https://doi.org/10.3390/pr12020342 - 6 Feb 2024
Viewed by 1278
Abstract
Proteins are complex molecules, which play a vital role in our body’s function, the building of tissues, and the regulation of metabolic activity. They are crucial to children’s growth and serve as a key component in the body’s process of distributing oxygen. Proteins [...] Read more.
Proteins are complex molecules, which play a vital role in our body’s function, the building of tissues, and the regulation of metabolic activity. They are crucial to children’s growth and serve as a key component in the body’s process of distributing oxygen. Proteins fuel the body by supplying the required nutrition and energy. Currently, there is an increasing demand for proteins on large scales with no detrimental effects. The adverse health effects of animal proteins have resulted in a growing preference for plant-based proteins, which offer a healthier daily dosage. Valuable proteins can be extracted from various parts of the plant, including stems, leaves, seeds, fruits, vegetables, and roots. Notably, protein extraction from waste plant and mushroom parts minimizes the product wastage and improves the overall production to support economic sustainability. There are several protein extraction techniques available, where the replacement of non-thermal methods with thermal ones is promising nowadays due to the appreciable retainment of protein quality. Pulsed Electric Field (PEF) technology is one of the most efficient non-thermal tools used to assist with extracting these proteins at the minimum processing time and energy consumption when compared with thermal techniques. It relies on the application of a high-voltage pulse between two electrodes to treat samples inside the treatment chamber. While electrode shapes and treatment chamber designs primarily govern the electric field’s application, optimizing process parameters such as electric field strength, pulse width, number of pulses, and pulse waveshape assists in obtaining a desirable enhancement in the protein yield. The primary objective of this review is to explain the PEF-assisted protein extraction process applicable to waste plant parts and deformed mushrooms. While PEF is not a novel concept, utilizing it as a pre-extraction treatment to the aforementioned waste resources would aid in improving the production of value-added protein products economically. So far, PEF has shown immense promise in assisting with protein extraction studies, but requires further research in order to establish this area for large-scale industrial applications. Full article
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28 pages, 6677 KiB  
Review
A Comparative Study on Recent Developments for Individual Rare Earth Elements Separation
by Subbu Venkata Satyasri Harsha Pathapati, Michael L. Free and Prashant K. Sarswat
Processes 2023, 11(7), 2070; https://doi.org/10.3390/pr11072070 - 11 Jul 2023
Cited by 3 | Viewed by 3310
Abstract
Facilitating the demands of modern society, namely, smartphones, televisions, electric vehicles, and high-stability aircraft structures, requires low-cost and high-performance materials and a corresponding change in the approach needed to design them. Rare earth elements (REEs) play a significant role in achieving these objectives [...] Read more.
Facilitating the demands of modern society, namely, smartphones, televisions, electric vehicles, and high-stability aircraft structures, requires low-cost and high-performance materials and a corresponding change in the approach needed to design them. Rare earth elements (REEs) play a significant role in achieving these objectives by adding small amounts of these elements to alloys, thereby enhancing material properties. Despite being more abundant than precious metals, the 17 REEs exhibit subtle variations in their chemical and physical characteristics. Thus, their separation is still crucial for industrial applications. There is a corresponding need to develop more effective and efficient separation methods. Adding to the separation challenge is the complexity of the sources of REEs and related materials. Thus, large-scale production of REE materials is difficult. Current REE processing techniques can be categorized into pre-treatment, beneficiation, separation, and refining. Researchers have developed various technologies encompassing chemical, physical, and biological methods, focusing on economic and environmental considerations. However, not all these approaches can be scaled up for mass production. This article focuses on feasible strategies such as precipitation and crystallization, oxidation and reduction, ion exchange, adsorption, solvent extraction, and membrane separation. Further research into these traditional and modern methods can potentially revolutionize the separation dynamics of REEs. Full article
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