LAUSR

Since 2000, global primary aluminum production has increased by 250% to an annual output of almost 65 million metric tonnes in 2018, much of this due to growth in China. Global demand continues to be driven by the need for strong, lightweight materials for vehicles and transport (to reduce fuel consumption and greenhouse gas emissions), durable and long-lasting materials for building and construction, protective packaging for food products, innovative consumer products, and many other uses. Aluminum’s durability and almost limitless recyclability, requiring only 5% of the original energy to produce primary metal, make it a key material and commodity in the world today. By 2040, global aluminum demand is projected to continue to grow, to as much as 90 million tonnes of primary metal per year with an additional 70 million tonnes of demand met by recycled aluminum. However, it is clear that further intensification of global production must be sustainable and matched by effective solutions that can address both current and future environmental challenges faced by the industry. The following JOM topic brings together eight articles highlighting the latest research in aluminum recycling and in the mitigation of environmental impacts from primary aluminum production, particularly management of hazardous by-products and airborne emissions. This JOM topic presents four articles on the management of bauxite residue (also known as ‘‘red mud’’), a solid by-product from the Bayer alumina refining process and a major environmental challenge. With current global inventory estimated at 3 billion tonnes and over 150 million tonnes being generated each year, much of it in long-term storage facilities, it is vital that the aluminum industry continues to develop effective, large-scale programs to remediate or reuse this by-product stream. The first article by Vaughan et al., titled ‘‘The Sandy Desilication Product Process Concept,’’ proposes a novel approach to address the challenge of reactive silica impurities in bauxite. These precipitate in the Bayer process as desilication product (DSP) and are discarded with bauxite residue, resulting in losses for the alumina refinery and making bauxite residue management more complex. The authors examine coarsening of this DSP via controlled crystallization, which provides lower-cost extraction and recycling of aluminum and sodium in the DSP than conventional sinter-leach processes. The second article, titled ‘‘Comprehensive Recovery of Iron and Aluminum from Ordinary Bayer Red Mud by Reductive Sintering–Magnetic Separation–Digesting Process,’’ by Gao et al. presents a design of experiments to optimize sintering and alkaline digestion conditions (temperature, time, ratio of added MgO/SiO2, and % NaOH) for their proposed RSMSD process, recovering up to 91% iron and 70% aluminum from bauxite residue. In this process, the magnetic separation step occurs prior to digestion, improving iron recovery, and MgO is used as the mineralising agent instead of the typical CaO. A third article, by Wang et al., titled ‘‘Assessment of Bauxite Residue for Reclamation Purposes, following Calcification–Carbonization Treatment,’’ compares the soil characteristics of treated bauxite residue with those of natural soil, nutritional soil, and untreated bauxite residue, if using it for reclamation purposes. Similarly, the fourth article, by Shi et al., titled ‘‘Analysis of Remediating Effects of Peat, Sawdust, and Gypsum in Alkaline Bauxite Residue Based on Orthogonal Experiments,’’ examines the suitability for plant growth of remediated bauxite residue following application of different treatments Moving away from the Bayer process, Zhou et al. present research relating to the extraction of alumina from coal fly ash (a major industrial waste stream from the coal-fired energy sector in China) as an alternate input to the primary aluminum industry. Their paper, titled ‘‘Heating Mechanism of David Wong and Pascal Lavoie are guest editors for the Aluminum Committee of the TMS Light Metals Division and also for the Recycling and Environmental Technologies Committee of the TMS Extraction & Processing and Light Metals Divisions for the topic Aluminum: Recycling and Environmental Footprint in this issue. JOM, Vol. 71, No. 9, 2019