5and the de Nora brothers is arguably the last technological breakthrough in industrial 6 electrolysis 1 . To practice the principles of green chemistry, extractive metallurgy awaits a 7 discovery of comparable magnitude directed at the mitigation of greenhouse gas emissions.

A novel potassium fertilizer material is obtained via hydrothermal processing of K-feldspar ore in alkaline conditions.

The production of iron metal with low greenhouse gas emissions can be performed by electrolysis. However, the electrolytic reduction of iron ore is not a technique that has reached a high degree of knowledge and development. With the aim of getting insight into the electrochemical reaction mechanism, this work shows that the reduction of iron ore to metal at low temperature in alkaline electrolyte is possible and occurs in a solid-state macroscopic mode. Electrochemical reactions take place in the volume of the solid, progressing from its outer surface toward the core, leading to full conversion to metal. A magnetite intermediate phase has been identified and high current efficiency is measured. Such a reaction occurs at high reaction rates, which further stimulates the interest of producing iron metal by the sole use of electricity.

Molten oxide electrolysis (MOE) is a carbon-free, electrochemical technique to decompose a metal oxide directly into liquid metal and oxygen gas. From an environmental perspective what makes MOE attractive is its ability to extract metal without generating greenhouse gases. Hence, an inert anode capable of sustained oxygen evolution is a critical enabling component for the technology. To this end, iridium has been evaluated in ironmaking cells operated with two different electrolytes. The basicity of the electrolyte has been found to have a dramatic effect on the stability of the iridium anode. The rate of iridium loss in an acidic melt with high silica content has been measured to be much less than that in a basic melt with high calcia content. Electrolysis is being investigated by the steel industry as a carbon-lean route that copes with the potential environmental constraints on emissions.1-3 Of all the new methods under consideration, only molten oxide electrolysis (MOE) produces liquid metal, 4,5 which occurs by the decomposition of iron oxide dissolved in an appropriately designed solvent melt according toThe reduction mechanism of MOE is similar to that of the HallHéroult process for aluminum production, which consists of the electrolytic decomposition of aluminum oxide dissolved in a molten fluoride solvent comprising cryolite. However, the two processes are fundamentally different with regards to the compensating oxidation reaction at the anode. In the Hall-Héroult cell, oxidation requires the attendant consumption of the carbon anode resulting in the generation of carbon dioxide. In MOE the compensating reaction is the generation of oxygen, which is predicated on the existence of a so-called inert anode whose development is nontrivial given the extreme conditions in the cell including:-temperatures in excess of the melting point of iron (1538 C) -high solubilizing power of a multicomponent oxide melt -evolution of pure oxygen gas at atmospheric pressure.Furthermore, to meet the production requirements of an industrial process, the anode must sustain high current densities, potentially exceeding 1 A cm À2 . Under these conditions, most metals are poor candidates due to the oxidizing atmosphere surrounding the anode and the extreme anodic potential to which the electrode is subjected. Furthermore, passivating oxide layers, which would normally protect a metallic surface, are dissolved by the molten oxide electrolyte resulting in unabated oxidation of the metal. 6,7 Previous work in this laboratory demonstrated that iridium can serve as an oxygen-evolving anode. 4,8 Furthermore, the anodic current density and, hence, the rate of oxygen evolution was found to increase with the optical basicity of the electrolyte at a given value of potential. The focus of the present study is the assessment of the chemical stability of iridium as a function of electrolyte composition. While the cost and scarcity of this metal make it unsuitable for industrial applications, it has a role to play in laboratory-scale studies ...

The electrodeposition of metal iron from iron dissolved species in alkaline media has been investigated. Dissolved ferric species in equilibrium with hematite (α-Fe2normalO3) have been electrochemically identified and their reduction to iron was demonstrated. The reduction efficiency was poor, however, because of the low concentration of dissolved matter (2.6×10−3M) . In order to determine more precisely the electrochemical features of the deposition reaction from iron ions, more concentrated solutions at 1.9×10−2M have been obtained using an iron anode as the ion source. Voltammetric and chronoamperometric investigations using a rotating disk electrode revealed that such concentrated solutions contain ferric and ferrous species, with higher concentration of the trivalent form. Metal can be deposited with higher current efficiency in these concentrated solutions with less than 30% of the current spent in hydrogen evolution.

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The mining of soluble potassium salts (potash) is essential for manufacturing fertilizers required to ensure continuous production of crops and hence global food security. As of 2014, potash is mined predominantly in the northern hemisphere, where large deposits occur. Production tonnage and prices do not take into account the needs of the farmers of the poorest countries. Consequently, soils of some regions of the southern hemisphere are currently being depleted of potassium due to the expansion and intensification of agriculture coupled with the lack of affordable potash. Moving away from mined salts towards locally available resources of potassium, such as K-bearing silicates, could be one option to improve this situation. Overall, the global potash production system and its sustainability warrant discussion. In this contribution we examine the history of potash production, and discuss the different sources and technologies used throughout the centuries. In particular, we highlight the political and economic conditions that favored the development of one specific technology over another. We identified a pattern of needs driving innovation. We show that as needs evolved throughout history, alternatives to soluble salts have been used to obtain K-fertilizers. Those alternatives may meet the incoming needs of our century, providing the regulatory and advisory practices that prevailed in the 20 th century are revised.

The electrolytic decomposition of metal oxides to metal and oxygen is an extractive metallurgy principle that, when coupled with carbon-free electricity, drastically mitigates the global warming impact of metal production. The present perspective discusses the electrochemical engineering features of an unconventional electrolyte, molten oxides. A survey of its thermodynamic properties suggests exceptional features, both in terms of applicability to multiple metals and operation at high temperature to produce liquid metal. The review of molten oxides' transport properties indicates that an unprecedented throughput can be envisioned, a promising feature for tonnage production. However, our ability to define the optimal electrolyte composition with regard to energy consumption is rendered limited due to the lack of predictive tools for both of the reviewed properties. A look at the state of the art in electrode materials reveals that quantitative design criteria remain to be developed for both the cathode and the anode. Metals have been essential materials for mankind for more than 2 millennia, and they remain the most important materials in terms of market value. Because of their centrality in the structural framework of the modern world, some metals have developed a commodity status, much like water or food. In the last two decades, an unprecedented increase in the global demand for metals has occurred ( Figure 1a). This trend is expected to continue with the world population predicted to reach 9 billion by 2020.Such growth does not come without challenges, particularly when it comes to the sustainability of primary metal production. Current extraction and processing routes are indeed characterized by large capital and environmental impacts. The former issue leads to difficulty in financing new facilities, particularly in developing countries that are poised to become significant consumers of primary metals. The existing technical paradigm necessitates multi-billion dollar investments that in turn require exceptional profits and short-term metal price stability in order to be supported by financing organizations. The environmental impact, illustrated in Figure 1b via the specific global warming and acidification potentials of key metals, can hinder the implementation of greenfield plants in countries with the most stringent environmental regulations. Additionally these emission potentials constitute a threat to the market in the eventuality of their taxation.The present perspective offers first to reconsider the existing paradigm for the extraction of metals from oxides, which accounts for the majority of metal resources in tonnage and value. In particular, this document focuses on the use of electricity for the direct decomposition of metal oxides. The first section discusses the metallurgical strategies to extract a metal (M) from its oxide (MO) and the characteristics of the direct electrolytic decomposition pathway. In the second section, an argument is made for the use of molten oxides as a possible supporti...