Keywords:end-of-life recycling rate (EOL-RR) industrial ecology old scrap ratio (OSR) recycled content (RC) recycling input rate (RIR) recycling metrics Supporting information is available on the JIE Web site SummaryThe recycling of metals is widely viewed as a fruitful sustainability strategy, but little information is available on the degree to which recycling is actually taking place. This article provides an overview on the current knowledge of recycling rates for 60 metals. We propose various recycling metrics, discuss relevant aspects of recycling processes, and present current estimates on global end-of-life recycling rates (EOL-RR; i.e., the percentage of a metal in discards that is actually recycled), recycled content (RC), and old scrap ratios (OSRs; i.e., the share of old scrap in the total scrap flow). Because of increases in metal use over time and long metal in-use lifetimes, many RC values are low and will remain so for the foreseeable future. Because of relatively low efficiencies in the collection and processing of most discarded products, inherent limitations in recycling processes, and the fact that primary material is often relatively abundant and low-cost (which thereby keeps down the price of scrap), many EOL-RRs are very low: Only for 18 metals (silver, aluminum, gold, cobalt, chromium, copper, iron, manganese, niobium, nickel, lead, palladium, platinum, rhenium, rhodium, tin, titanium, and zinc) is the EOL-RR above 50% at present. Only for niobium, lead, and ruthenium is the RC above 50%, although 16 metals are in the 25% to 50% range. Thirteen metals have an OSR greater than 50%. These estimates may be used in considerations of whether recycling efficiencies can be improved; which metric could best encourage improved effectiveness in recycling; and an improved understanding of the dependence of recycling on economics, technology, and other factors.

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.

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.

The characterization of electric arc furnace (EAF) dust shows that bubble burst at the liquid steel surface is the principal source of dust emission. We have therefore developed an experimental device for studying this phenomenon. As in the case of the air-water system, the bubble-burst gives birth to two types of droplets: film drops and jet drops. The jet drop formation is observed with high-speed video. The film drop aerosol is collected on filters and, then, characterized by means of SEM, granulometric and gravimetric analyses. Results are presented and discussed. The quantification of both types of projections leads to the conclusion that the film drop projections represent the major source of dust. The amount of film drops greatly decreases with the parent bubble size. Under 4.5 mm in bubble diameter, no film drops are formed. Decreasing enough the bubble size would therefore represent an effective solution for reducing drastically the EAF dust emission. Published in Powder Technology, 2005, 157, 1-3, 2-11.

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The accurate determination of the diffusion coefficient of dissolved CO2 in aqueous solutions is a key parameter to predict the transport of the dissolved gas in the aqueous solution of porous aquifers and caprocks in the context of the mitigation of greenhouse gases emissions. A better understanding of the diffusion kinetics of dissolved CO2 as a function of subsurface conditions is essential to ensure the integrity of CO2 storage in saline aquifers. Experimental data are available to predict the CO2 diffusion kinetics as a function of temperature and pressure. However, the impact of salinity on CO2 diffusivity is still poorly documented. In this work, the diffusion coefficients of dissolved CO2 were determined using in situ Raman microspectrometry in Fused Silica Capillaries in a range of salinity from 0.0 to 6.0 molNaCl kg−1H2O. The diffusion coefficient of CO2 dissolved in pure water at 21 ± 1 °C and 40 bar is 1.71 × 10−9 ± 0.06 m2 s−1. In the same conditions of pressure and temperature, the diffusion coefficient of dissolved CO2 decreases with salinity increase: from 0.0 to 6.0 molNaCl kg−1H2O (the diffusion kinetics of dissolved CO2 is divided by two). Consequently, the impact of salinity on the diffusion coefficient of dissolved CO2 must be taken into account to evaluate the transport of dissolved gases in the brine of the reservoir and caprock. Copyright © 2015 John Wiley & Sons, Ltd.