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Recycling the valuable metals found in spent permanent magnets (REPMs) poses a significant global challenge for the future. This study examines the efficiency of back extraction of rare earth elements (REEs) by oxalic acid solution from di-(2-ethylhexyl) phosphoric acid (D2EHPA) in recycling REPMs. To evaluate the efficiency of this process, several experiments were carried out using designed BOX-Behnken methodology to investigate the effects of various operational and chemical parameters, including stripping solution to loaded organic phase volume ratio (in the range of 1.0-2.0), oxalic acid concentration (ranging from 0.25 to 0.75 M), the stirring rate (ranged between 150 and 350 rpm), and stripping time (ranging from 15 to 45 min) on the REEs recovery and the purity of final production. Analysis of variance was applied to rigorously examine the results statistically. The results showed that more than 85 % of light and 80 % of heavy REEs can be recovered under optimal conditions. Moreover, the final product contained 43.5 % REEs and approximately 0.1 % iron. The stripping experiment using phosphoric acid as the reagent demonstrated ∼57 % light and ∼4 % heavy REEs recovery. Additionally, the recyclability of the organic phase showed its effective reuse for up to four cycles. This study underscores significant progress in the selective recovery of rare earth elements through a relatively straightforward process consuming mild reagents., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Permanent magnets are fundamental constituents in key sectors such as energy and transport, but also robotics, automatization, medicine, etc. High-performance magnets are based on rare earth elements (RE), included in the European list of critical raw materials list. The volatility of their market increased the research over the past decade to develop RE-free magnets to fill the large performance/cost gap existing between ferrites and RE-based magnets. The improvement of hard ferrites and Mn-Al-C permanent magnets plays into this important technological role in the near future. The possible substitution advantage was widely discussed in the literature considering both magnetic properties and economic aspects. To evaluate further sustainability aspects, the present paper gives a life cycle assessment quantifying the environmental gain resulting from the production of RE-free magnets based on traditional hexaferrite and Mn-Al-C. The analysis quantified an advantage of both magnets that overcomes the 95% in all the considered impact categories (such as climate change, ozone depletion, human toxicity) compared to RE-based technologies. The benefit also includes the health and safety of working time aspects, proving possible reduction of worker risks by 3-12 times. The results represent the fundamentals for the development of green magnets that are able to significantly contribute to an effective sustainable transition., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The present work aims to describe and review the available technologies and the recent advancements in treating industrial wastewater containing tetramethylammonium hydroxide (TMAH). It is a quaternary ammonium salt and widely used in the microelectronics industry; this kind of company produces large quantities of wastewater containing TMAH. The exhausted solutions must be treated appropriately since TMAH is corrosive, toxic to human health, and ecotoxic. Regarding the concentration at discharge, currently there are no European regulations. Still, it has been indicated that the substance has a negative influence on the oxygen balance and cause eutrophication, and fall into the relevant categories. In the first part of the work, the available technologies and the recent advancements for the treatment of TMAH contained in industrial wastewater are reviewed. Separation methods as such adsorption, ion exchange, membrane processes, and destruction technologies classified as advanced oxidation processes and biological processes have been considered. In the second part of the manuscript, industrial patented wastewater treatments have been described. Biological processes are those more used, being more economically feasible, require very long times not always sustainable., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The current paper presents an innovative hydrometallurgical methodology for recovery of precious metals from different waste streams. The used hydrometallurgical process, which has been already patented (Birloaga and Francesco Veglio, 2019), consists of a single leaching system (HCl, H 2 O 2 and C 2 H 4 O 2 ) of all elements and then selective recovery of elements from solution by chemical reduction/processes. About 99% of Au dissolution efficiency was achieved using: 3.5 M HCl; 1.96 M H 2 O 2 ; 1.67 M of C 2 H 4 O 2 ; 5 h without stirring; room temperature; 20% of solid concentration. The same conditions have resulted recovery of over 95% of Au from spent mobile phones PCBs. Over 80% of Au was achieved by three steps of leaching of ceramic Intel CPU. The influences of hydrochloric acid concentration and process time have been evaluated for Pd and Pt leaching from spent autocatalyst. Over 89% of Pt and 100% of Pd recovery were obtained from spent catalyst using: 5 M HCl; 1.96 M H 2 O 2 ; 1.67 M of C 2 H 4 O 2 ; 250 rpm of stirring for 3 h; room temperature; 10% of solid concentration. More than 98% of Pd recovery was achieved from the turbine residue after 20 min of reaction. The almost complete recovery of Au (99%) from solution was achieved by reduction with ascorbic acid. Complete recovery of Pd and about 79% of Pt have been obtained by cementation with ion metal powder from the leaching solution of spent autocatalyst. The application of reduction process with iron metal on the solution of turbine residues led to over 99% of Pd recovery. This efficient process provides a new way to recycle precious metals and to effectively prevent environmental pollution from different e-waste and other waste streams., (Copyright © 2022 Elsevier Ltd. All rights reserved.)