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“…Manganese , because of its low equilibrium potential, suffers from interference of side-reactions during electrodeposition, such as hydrogen evolution and co-deposition of other metal cations with higher redox potentials ( Padhy et al., 2016 ). In a single-cation solution of manganese, high current efficiency for manganese deposition was not possible without the use of additives, such as selenium, tellurium, and sulfite compounds in the electrowinning bath ( Griškonis et al., 2014 ; Lu et al., 2014 ; Sun et al., 2011 ).…”
Section: Electrochemical Separations For Selective Recoverymentioning
confidence: 99%
“…In a single-cation solution of manganese, high current efficiency for manganese deposition was not possible without the use of additives, such as selenium, tellurium, and sulfite compounds in the electrowinning bath ( Griškonis et al., 2014 ; Lu et al., 2014 ; Sun et al., 2011 ). Such additives preferentially increased the overpotential of hydrogen evolution, thereby improving the manganese deposition rate ( Padhy et al., 2016 ; Sun et al., 2011 ). Harris et al.…”
Section: Electrochemical Separations For Selective Recoverymentioning
confidence: 99%
“…The main advantage of the electrochemical pathways is the possible recovery of metals in preferred speciation forms. For example, in many electrodeposition cases, final products are recovered as zero-valent metallic species ( Jin et al., 2018 ; Jin and Zhang, 2020 ; Maguyon et al., 2012 ; Padhy et al., 2016 ; Yang et al., 2014 ; You et al., 2012 ). In other cases, metals with negative reduction potential can be recovered as air-stable precursors; for example, lithium can be recovered in the form of air-stable Li 2 CO 3 or LiOH ( Bae et al., 2016 ; Hoshino, 2015 ).…”
Section: Future Perspectives and Opportunitiesmentioning
Summary
Critical minerals are essential for the ever-increasing urban and industrial activities in modern society. The shift to cost-efficient and ecofriendly urban mining can be an avenue to replace the traditional linear flow of virgin-mined materials. Electrochemical separation technologies provide a sustainable approach to metal recovery, through possible integration with renewable energy, the minimization of external chemical input, as well as reducing secondary pollution. In this review, recent advances in electrochemically mediated technologies for metal recovery are discussed, with a focus on rare earth elements and other key critical materials for the modern circular economy. Given the extreme heterogeneity of hydrometallurgically-derived media of complex feedstocks, we focus on the nature of molecular selectivity in various electrochemically assisted recovery techniques. Finally, we provide a perspective on the challenges and opportunities for process intensification in critical materials recycling, especially through combining electrochemical and hydrometallurgical separation steps.
“…Manganese , because of its low equilibrium potential, suffers from interference of side-reactions during electrodeposition, such as hydrogen evolution and co-deposition of other metal cations with higher redox potentials ( Padhy et al., 2016 ). In a single-cation solution of manganese, high current efficiency for manganese deposition was not possible without the use of additives, such as selenium, tellurium, and sulfite compounds in the electrowinning bath ( Griškonis et al., 2014 ; Lu et al., 2014 ; Sun et al., 2011 ).…”
Section: Electrochemical Separations For Selective Recoverymentioning
confidence: 99%
“…In a single-cation solution of manganese, high current efficiency for manganese deposition was not possible without the use of additives, such as selenium, tellurium, and sulfite compounds in the electrowinning bath ( Griškonis et al., 2014 ; Lu et al., 2014 ; Sun et al., 2011 ). Such additives preferentially increased the overpotential of hydrogen evolution, thereby improving the manganese deposition rate ( Padhy et al., 2016 ; Sun et al., 2011 ). Harris et al.…”
Section: Electrochemical Separations For Selective Recoverymentioning
confidence: 99%
“…The main advantage of the electrochemical pathways is the possible recovery of metals in preferred speciation forms. For example, in many electrodeposition cases, final products are recovered as zero-valent metallic species ( Jin et al., 2018 ; Jin and Zhang, 2020 ; Maguyon et al., 2012 ; Padhy et al., 2016 ; Yang et al., 2014 ; You et al., 2012 ). In other cases, metals with negative reduction potential can be recovered as air-stable precursors; for example, lithium can be recovered in the form of air-stable Li 2 CO 3 or LiOH ( Bae et al., 2016 ; Hoshino, 2015 ).…”
Section: Future Perspectives and Opportunitiesmentioning
Summary
Critical minerals are essential for the ever-increasing urban and industrial activities in modern society. The shift to cost-efficient and ecofriendly urban mining can be an avenue to replace the traditional linear flow of virgin-mined materials. Electrochemical separation technologies provide a sustainable approach to metal recovery, through possible integration with renewable energy, the minimization of external chemical input, as well as reducing secondary pollution. In this review, recent advances in electrochemically mediated technologies for metal recovery are discussed, with a focus on rare earth elements and other key critical materials for the modern circular economy. Given the extreme heterogeneity of hydrometallurgically-derived media of complex feedstocks, we focus on the nature of molecular selectivity in various electrochemically assisted recovery techniques. Finally, we provide a perspective on the challenges and opportunities for process intensification in critical materials recycling, especially through combining electrochemical and hydrometallurgical separation steps.
“…The Mn 2p spectra showed a peak with a binding energy of 640.4 eV and a satellite peak 5.1 eV ahead of the binding energy (Fig. 5(C)), which may be assigned to structural Mn 2+ in MnS 33,34 . These results reveal that reduction of MnO 2 by Na 2 S, along with the generation of MnS, occurs in P0.05 and P0.2.Figure 5High-resolution ( A ) S 2p, ( B ) Fe 2p and ( C ) Mn 2p XPS spectra of P0, P0.05 and P0.2.…”
Erdite is a rare sulphide mineral found in mafic and alkaline rocks. Only weakly crystallised fibrous erdite has been artificially synthesised via evaporation or the hydrothermal method, and the process generally requires 1–3 days and large amounts of energy to complete. In this study, well-crystallised erdite nanorods were produced within 3 h by using MnO2 as an auxiliary reagent in a one-step hydrothermal method. Results showed that erdite could synthesised in nanorod form with a diameter of approximately 200 nm and lengths of 0.5–3 μm by adding MnO2; moreover, the crystals grew with increasing MnO2 addition. Without MnO2, erdite particles were generated in irregular form. The capacity of the erdite nanorods for tetracycline (TC) adsorption was 2613.3 mg/g, which is higher than those of irregular erdite and other reported adsorbents. The major adsorption mechanism of the crystals involves a coordinating reaction between the −NH2 group of TC and the hydroxyl group of Fe oxyhydroxide produced from erdite hydrolysis. To the best of our knowledge, this study is the first to synthesise erdite nanorods and use them in TC adsorption. Erdite nanorods may be developed as a new material in the treatment of TC-containing wastewater.
“…Manganese electrodeposition was conducted in a two-compartment electrochemical cell separated by a membrane (Nafion 115). In the cathodic compartment, the electrolyte solution consisted 0.2 M MnSO 4 ·H 2 O (Sigma-Aldrich, 99%), 1.0 M (NH 4 ) 2 SO 4 (Sigma-Aldrich, 99%) and 20 mg/L of sodium octyl sulfate (Sigma-Aldrich, ≥95%), a surfactant that has been previously reported to improve current efficiency and manganese deposit morphology . Prior to deposition, the catholyte was purified via a pre-electrolysis procedure .…”
Manganese electrodeposition and anodization are performed on an Fe−Ni−Cr alloy (Incoloy 800H) to form an Mn/MnO surface coating after thermal pretreatment. The Mn/ MnO-coated alloy is coked under simulated steam cracking conditions in ethylene-steam, and its anticoking performance is compared with pretreated, uncoated alloys. The mass of deposited coke during repeated coking cycles is measured by thermogravimetric analysis (TGA) and also determined from the measured CO/CO 2 concentrations during decoking with air. Compared to the uncoated alloys that have Cr 2 O 3 -rich surfaces, the Mn/MnO-coated alloy shows 30−40% less deposited coke and a peak coke oxidation temperature reduced by about 100 °C. The Mn/MnO surface coating is hypothesized to reduce coke deposition by limiting the amount of Fe/Ni species on the surface and by catalyzing coke gasification/oxidation reactions via the formation of catalytically active Mn 3+ species.
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