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This paper was previously published in the ICSOBA Newsletter Volume 14, December 2015

Management and use of bauxite residue

By Ken Evans*

This paper serves as a brief overview of especially true of the early European sites the mud washing circuit is pumped, the history and trends in the management including: Bergheim (Germany) - on site with a solids content of 20 to 30%, into and use of bauxite residue, outlining: The storage then in a former lignite mines; storage areas created by dams and other dimensions of the problem; how methods Burntisland (UK) - disposal into an estuary, earthworks for secure containment. In of storage and disposal have developed then behind a sea wall, see Figure 1, then many instances valleys were dammed for over time and the implications for bauxite an old shale mine; see Figure 2, Gardanne example, Ewarton (Jamaica), see Figures residue use; characteristics of bauxite (France) - storage in a dammed valley 3 and 4, Gardanne, Salindres, Saint Cyr residue; the technically successful uses; then disposal by pipeline to the sea; La (France), Ouro Preto (Brazil). Examples the challenges to implementation – real Barasse (France) - storage on site then of old mine storage were: bauxite mines and perceived; a review of large scale/ nearby dammed valley then disposal to (Kirkvine (Jamaica), Bauxite (USA)), lignite industrial scale successes; and some hopes mines (Bergheim), and oil shale quarries for the future. (Burntisland). Annual production of smelter grade In the case with sites constructed and chemical grade alumina in 2015 was in the past three or four decades, the some 115 million tonnes1 which, with storage areas have normally been sealed the exception of some plants in Russia, to minimise leakage to the underlying Iran and China, is all produced using the ground and ground-water, however, this Bayer process. The global average for the tended not to be the practice in earlier production of bauxite residue per tonne years. Sealing approaches cover a range of of alumina is between 1 and 1.5 tonnes, materials including compacted clay and/or though the range is much broader, so it the use of plastic and other membrane is estimated that some of the 150 million materials. tonnes of bauxite residue is produced The supernatant liquor above the annually. This is generated at some 60 residue was normally returned to the active Bayer plants. In addition there are plant for reuse thereby recovering some at least another 50 closed legacy sites, so of the caustic soda value and avoiding the combined stockpile of bauxite residue contaminating the environment. Various at active and legacy sites is estimated at drainage and seepage collection systems three thousand million tonnes. have been incorporated into the design and construction of the facilities. The History and trends in disposal and construction of the storage area was often storage methods Fig 1. Bauxite disposasl into an estuary to recover land dictated by the type of bauxite residue and Management of and the methods of the differed for clay like muds compared to storage of bauxite residue has evolved sea via a pipeline; Larne (UK) - disposal more sandy residues. At Gramercy (USA), progressively over the decades2. In the into sea water lagoons; Ludwigshafen sand-bed filtration was used and “French early Bayer alumina plants, the residue (Germany) - storage on site; Newport (UK) Drains” were used with drainage pipes and generated was often merely piled up on – disposal into estuary from barges then covering layers of sand of different size site or an area adjoining the alumina plant. sea water lagoons; Salindres (France) – on and gravel to give permeability through Occasionally nearby depleted mine or site storage then in a dammed valley and the base of the lake. This was termed the quarry sites, were used. In other situations Schwandorf (Germany) – on site storage.. Decantation, Drainage and Evaporation of nearby estuaries or sea lagoons were used Prior to 1980, most of the inventory Water (DREW) system. and then later as the closest convenient of bauxite residue was stored in lagoon- There are many examples of this storage areas were filled, valleys were dammed type impoundments and the practice is method but they include Stade (Germany), to contain the ever-growing volume of still carried out at some facilities. In this Burnside (USA) and Vaudreuil (Canada). In residue. These methods of storage were method, the bauxite residue slurry from some cases, low dykes or levees were built

*Consultant, International Aluminium Institute

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of valuable soda and alumina to the Bayer process plants and to minimise the potential for leakage to the surrounding environment. The current trend in residue storage practice is towards increasing use of dry stacking as the preferred technology, and further research to optimise this technology is appropriate. Very many plants now use equipment such as Amphirols to aid dewatering of the mud in order to compact and consolidate the Fig 2. Bauxite residue disposal into a former oil shale mine residue. See Figure 6. Partial neutralisation using seawater is practiced at a number of to the final expected height at the start discharge is no longer undertaken at Australian plants close to the sea (Yarwun and a new area constructed when more any alumina refining facilities and all sea and QAL); carbonation by using waste volume was required whilst in others the discharge will be completely phased out carbon dioxide from ammonia production dam walls were successively increased by the end of 2015. has been used (Kwinana (Australia)); and when the space was filled. The area of As land for lagoon storage became accelerated carbonation using intensive suitable land readily available dictated the scarce for many plants, “Dry stacking” farming methods, Aughinish (Ireland), approach. methods were used. A dry stacking regime Kwinana, Worsley (Australia)) is showing If the residue material is not neutralised was adopted nearly 75 years ago in the considerable benefits. before discharge to the storage lagoon, UK3 and about 50 years ago in Germany4 Filtration using drum filters and plate it becomes a highly alkaline, poorly and since the 1980s the trend has been and frame filter presses to recover caustic compacted mud area covered by a highly increasingly towards dry stacking to reduce soda, produce a lower moisture and alkaline lake, see for example the lake in more handleable bauxite residue have Figure 4 which had a pH >12 and a soda been employed for some 80 years but is level in excess of 2,000 mg/L many years now growing in usage. Plate and frame after pumping had stopped. filter presses were adopted in Vaudreuil This creates safety and environmental in 1936 when the plant was constructed hazards including the potential for contact and in Burntisland in 1941 as the lagoons of humans and wildlife with alkaline adjacent to the site were full. In the case liquor and mud, and contamination of of Burntisland the bauxite residue needed surface and ground waters by leaching to be transported on public roads through of caustic liquor and other contaminants. the town to a nearby old oil shale mine Regrettably in many cases these early so a high solids content mud was a ponds have proved of limited efficacy and Fig 3. Bauxite residue disposal into a dammed valley key requirement. In the mid 1960s at caustic liquor, plus other contaminants, has to create a lagoon, early stages Ludwigshafen, vacuum drum filters were subsequently seeped into the surrounding adopted. Figure 7 shows a press filter. environment. Ongoing remediation of In addition to helping recover more these situations is proving to be a costly the potential for leakage of caustic liquor caustic, this trend opens up considerable exercise. Addressing the risk and to to the surrounding environment, reduce benefits in terms of reuse as the material eliminate the potential for catastrophic the land area required, and maximise is normally produced as a friable cake, failure of the dam/impoundment and the recoveries of soda and alumina. with typically less than 28% moisture, and consequent environmental hazard to Considerable work was undertaken in lower soda thereby dramatically reducing the surrounding area/communities Jamaica on the Robinsky5 sloped thickened transport issues and costs. Alunorte introduces high monitoring, maintenance tailing disposal system and Ewarton (Brazil), Distomon (Greece), Gardanne, and remediation costs. Under some adopted the practice in the mid-1980s6. Kwinana, Seydisehir (Turkey) and many circumstances, this has created the See Figure 5. Additionally, improved plants in China have already adopted prospect of an indefinite legacy. methods for thickening and washing of or plan to adopt plate and frame filter Another disposal technique adopted the residues prior to storage, and recovery presses. Hyper Baric filters are reported to by some plants was sea or river disposal of decant water during storage, have achieve particularly low moisture content particularly in the 1940s to 1960s. In at been developed to increase the recovery material with the performance of the least six plants, two located in France (Gardanne and La Barasse), one in Greece (Distomon) and three in Japan (Shimizu, Ehime, Yokohama), bauxite residue was discharged into the sea either via pipelines or from ocean going vessels. Other alumina plants disposed of the residue into rivers or estuaries, for example into the Mississippi River (Gramercy), and Severn Estuary (Newport). In other cases in Ireland (Larne), Wales (Newport) and Scotland (Burntisland), land was reclaimed from the sea by disposing of the residue Fig 4. Bauxite residue disposal into dammed valley, later stages in tidal lagoons or behind sea walls. River

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press being enhanced when steam is particle size distribution, morphology and used; moisture contents lower than 25% Component Typical range (%) nature of the residue emanating from a have been reported. particular plant. Fe O 5 - 60 The appalling and tragic incident at the 2 3 There is relatively little published data Al O 5 - 30 bauxite residue ponds adjacent to the Ajka 2 3 on the cost of disposal of bauxite residue TiO2 0.3 -15 alumina refinery in Hungary in October CaO 2 - 14 but it is generally estimated to be between 2010 when some 600,000 to 800,000m3 1 and 3% of the total production cost, SiO2 3 - 50 of caustic red mud slurry inundated the Na2O 1 - 10 perhaps US$4 to 12. This is lower than village of Kolontar and flowed into the LOM 5 - 20 often expected and must be borne in mind Torna Creek, Marcal and Raba rivers when potential uses are considered. In the had a significant effect on the alumina Table 1. Chemical composition, expressed as oxides, absence of landfill taxes, which for example industry. The producers, via organisations commonly found in bauxite residue were introduced on bauxite residue in the such as European Aluminium and the UK in 1996, most companies have been International Aluminium Institute, have operators but in spite of over a century of reluctant to spend more than is required since worked collaboratively to look endeavour and trials, only some 2 to 3% to comply with the law and ensure storage for improved solutions and propose of the nearly 140 million tonnes of bauxite is undertaken safely in a manner that does best practice guidelines, which were residue produced annually is used in a not pollute the surrounding environment published in a guideline document1. The productive way. Thousands of trials have and the area can subsequently be IAI continues to encourage collaborative been successfully completed and dozens restored. Despite the strong desire and effort on improving storage, monitoring, of uses have been identified as being enthusiasm of companies to present a safety standards, looking at improved technically feasible but the challenge ‘green’ and ‘sustainable’ corporate image, remediation techniques and reuse remains to find good economically viable the utilisation opportunity must make opportunities. In 2011 the International uses for the amount generated every year economic sense, or at least close to, for let alone eat into the material already stockpiled. The bauxite residue disposal costs for a plant are obviously very dependent on the availability of a suitable disposal site, the distance from the plant to the disposal area and the method on conveying used (by pumping, conveyor or truck). It should be noted that pumping over long distances can be achieved, even in excess of 50km. Residues from different bauxites also behave quite differently in terms of composition, mineralogy and particle size. They will have different handling and pumping characteristics and display Fig 5. Dry mud stacking widely different settling and particle Fig 6. Mud dewatering and compaction packing characteristics thereby influencing moisture contents after treatment Aluminium Institute issued a set of targets and handling costs. The variation in projects to be implemented. Corporate for IAI members to work towards2. Key composition naturally has an overriding attitudes have change dramatically over messages coming out of the best practice effect on potential applications so any the past 10 years, reflecting growing reviews have been the drive to dispose practical work looking at applications community awareness and to meet the of and store bauxite residue in a safer must take into account the specific demands of concerned shareholders and way with lower caustic and higher solids chemical composition, mineralogy, pH, NGOs, and producers now have a more content. holistic attitude to resolving the problem

The changes within the industry over Component Typical range (%) and reducing the area given over to the last 20 years has meant than many residual disposal areas. of the relatively small Bayer plants have Despite the increasing trend to higher Sodalite (3Na2O.3Al2O3.6SiO2.Na2SO4) 4 - 40 ceased operation and there has been an Al -goethite ((Fe,Al)2O3.nH2O) 1 - 55 solids contents and lower soda values, inexorable shift to much larger alumina Haematite (Fe2O3) 10 - 30 one retrograde factor with respect to Magnetite (Fe O ) 0 - 8 refineries in countries such as Australia, 3 4 generation of bauxite residue is the Silica (SiO ) crystalline and amorphous 3 - 20 Brazil and India. In a number of cases, the 2 current diminishing stocks of high quality, Calcium aluminate (3CaO.Al O .6H O) 2 - 20 former alumina plant has been converted 2 3 2 easily extractable, high alumina bauxite to a speciality alumina plant, which uses Boehmite (AlOOH) 0 - 20 sources – this has the effect of driving Titanium Dioxide (TiO ) anatase and rutile 2 - 15 aluminium hydroxide as feed instead of 2 up the amount of residue produced per Muscovite (K2O.3Al2O3. 6SiO2.2H2O) 0 - 15 bauxite; this trend has been particularly Calcite (CaCO ) 2 - 20 tonne of alumina produced. apparent in Europe and includes Ajka, 3 Kaolinite (Al2O3. 2SiO2.2H2O) 0 - 5

Bergheim, Ludwigshafen, Salindres and Gibbsite (Al(OH)3) 0 - 5 Bauxite residue characteristics

Schwandorf. In the USA the two former Perovskite (CaTiO3) 0 - 12 The key first steps in discussing uses is a

Bayer plants at Bauxite have closed but the Cancrinite (Na6[Al6Si6O24].2CaCO3) 0 - 50 consideration of the chemical compounds speciality alumina operation at the former Diaspore (AlOOH) 0 - 5 present in the bauxite residue, the levels Alcoa plant continues in operation. present and the physical characteristics of Reuse of bauxite residue has long Table 2. Typical range of components found in bauxite the material. As discussed, the variation in featured in the thinking of Bayer plant residues composition is extremely wide as shown

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in Table 1; these are for commonly used and hydroxyacids such as humic, fulvic, Bauxsol®, ReadyGritTM, BPR – Bayer bauxites and the range can be even succinic, acetic or oxalic acids. Process Residue, ARR – Alumina Refinery broader for some unusual bauxites. In addition, the bauxite residue will Residue, Bauxite tailings, Ferroalumina, A wide range of other components may contain small quantities of some of the Ferraloks, ART – Alumina refinery also be present at low levels; these will soluble sodium compounds resulting tailings, Redmedite, TerraBTM, ViroMineTM, invariably be as metallic oxides e.g. arsenic, from the sodium hydroxide used in the ViroSoilsTM, ViroSewageTM, CajuniteTM beryllium, cadmium, chromium, copper, extraction process will remain depending and RMG. Bauxite residue is arguably a gallium, lead, manganese, mercury, nickel, on the dewatering and washing systems more inclusive name as some alumina potassium, scandium, thorium, uranium, used. All alumina refineries try to maximise refineries separate the coarse high silica vanadium, zinc, zirconium and rare earth the recovery of the valuable caustic soda sandy fraction from the fine muds; some elements. Non-metallic elements that from the residues in order to reuse it of the muds are brown rather than red; may occur in the bauxite residue are during the extraction process. The residual and some diasporic derived residues are phosphorus, carbon and sulphur. soluble sodium species, predominantly a almost black in colour. However, the name The minerals present are complex and mixture of sodium aluminate and sodium “red mud” tends to be more commonly comprise some which are present in the carbonate, give rise to an elevated pH used in North America and Europe. bauxite and others that are produced for bauxite residue slurries. Over time during the autoclaving and the desilication the residual sodium species are partially Technical successes in the use of processes. The range of minerals typically neutralised by carbon dioxide from the bauxite residue found for bauxite residues is shown in air to form sodium carbonate and other Many potential applications have been Table 2. metal carbonate species; these species considered and explored for decades In addition there are various other will resulting in a lower pH for the with particular focus on the recovery of elements present in the bauxite residue. Even Bayer himself in his 1892 patent describing the Bayer Process proposed the potential for iron recovery. Possible applications can broadly be broken down into various categories: ᔢ Recovery of specific components present in the bauxite residue, e.g. iron, titanium, aluminium, lanthanides, yttrium and scandium; ᔢ Use as a major component in manufacture of another product, e.g. cement; ᔢ Use of the bauxite residue as a component in a building or construction material, e.g. concrete, tiles, bricks; ᔢ Use for soil amelioration or capping; Fig 7. Plate and filter press ᔢ Use for some specific property, which might include conversion of the bauxite residue to a useful material by minerals sometimes found at low levels bauxite residue which renders them less modifying the compounds present, e.g. including Brookite, Calcite, Carnegieite, hazardous. Virotec process. Chantalite, Dolomite, Hydrogarnet, The other factors that are in important Hydroxycancrinite, Katoite–Si, Lawsonite, when considering uses are the physical The list of areas where bauxite residue Nepheline, Nosean, Portlandite, characteristics such as particle size covers almost all of inorganic material Schaeferite, sodium titanate, and zircon. distribution and some variable parameters science and a full review would extend Sodium is the only element not found such as moisture content. The median to pages, some of the most attractive in the bauxite itself; some of the elements particle size is normally in the range of 5 to have been: cement manufacture, use are soluble in the Bayer process and either 10 µm, however, the breadth of particles in concrete, iron recovery, titanium build up in the Bayer liquor, or precipitate is both very broad ranging from coarse recovery, use in building panels, bricks, along with the aluminium hydroxide. sandy grains about 1mm in size down to foamed insulating bricks, tiles, refuse tip Depending on the temperature used in sub-micron particles for bauxite residues capping/site restoration, treatment of acid the extraction process, some elements will produced from different alumina plants mine drainage, soil amelioration, road increase in concentration in the bauxite and different bauxites. Some alumina construction, dam/levee construction, residue relative to the bauxite, whilst refineries separate the different size pigments, glass ceramics. Meanwhile others will be lower in the bauxite residue. fractions during processing whilst others some other uses which have been Other than caustic soda, lime is normally do not; the coarse sandy fraction has been shown to be technically feasible but not the only other inorganic compound given various names, for example “Red yet exploited to any significant degree introduced during the Bayer process. SandTM” or “Red Oxide Sand”. are: Lanthanides (rare earth elements) A wide variety of organic compounds It should be noted that bauxite residue recovery, scandium recovery, gallium can also be present, these are derived or red mud has been called a variety of recovery, vanadium recovery, cobalt from vegetable and organic matter in names by different companies, sometimes recovery, yttrium recovery, adsorbent of the bauxite/overburden or the use of after additional treatment and some of the heavy metals, dyes, phosphates, fluoride, crystal growth modifiers or flocculants names are registered trademarks. These water treatment chemical, ceramics, and includes carbohydrates, alcohols, names include: Bauxaline®, AlkaloamTM, foamed glass, oil drilling or gas extraction phenols, and the sodium salts of polybasic Red Oxide Sand, Red SandTTM, Ferraloks, proppants, gravel/railway ballast, calcium

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and silicon fertiliser, filler for PVC, wood (naturally occurring radioactivity material) include the manufacture of bricks for substitute, geopolymers, catalysts, plasma in particular 238U and 232Th, and this is domestic buildings in Jamaica, the use spray coating of aluminium and copper, normally doubled in the bauxite residue. of construction materials in applications manufacture of aluminium titanate- The radioactivity in the bauxite residue other than roof tiles in Hungary and the Mullite composites for high temperature is sometimes referred to as TENORM manufacture of ceramic insulating fibre resistant coatings, composites with (technologically enhanced naturally for domestic situations. An “Activity epoxides, composites with poly aniline, occurring radioactivity material). Index” assessment has been proposed to manufacture of radiopaque materials In general, two approaches are used consider each application on its merits for the construction of X-Ray diagnostic to assess the risk from radioactivity: looking at the level of radioactivity in the and CT scanner rooms, desulfurisation Measurement of the elements that could bauxite residue, the amount of bauxite of flue gas, arsenic removal, chromium lead to radioactivity, namely analysing residue in the product and the time and removal7,8. Some applications, such as use for Ac, At, Bi, Pa, Pb, Po, Ra, Th, Tl, degree of expected exposure11. in pigments have been successful but use U and then calculating a radioactivity very small tonnages. value; or by direct measurement. The EU Alkalinity/high sodium The question so often asked is why some Radiation Protection Guideline 112 has The high pH is a problem from both a health of these potentially exciting applications a recommended range of 0.3 – 1 mSv/y and safety aspect and potentially adverse have failed to be implemented when on for building materials; the particular effects in the particular application. This a small scale they look so attractive. It is limit being determined by the expected ranges from poor weathering resistance certainly not the desire of producers to exposure. in construction materials to high sodicity harbour their bauxite residue! The data published on radioactivity when used in soil amelioration. Both high levels has historically been limited but Major barriers to reuse some information that has been reported Fig 8. Use of Red SandTM for road construction When considering the commercial/ on a range of bauxite residue shows that (Photo courtesy of Alcoa) industrial implementation of uses that have thorium was only present in significant been found to be technically successful, it levels in bauxite residue from Venezuelan is important to consider the barriers that bauxite but still remains below acceptable have prevented the implementation of limits. The uranium content is more than apparently sound and economic solutions. 10 mg/kg in Jamaican and Venezuelan The materials that bauxite residue would bauxites but the total radioactivity be replacing in any application are very calculated will still remain below often readily and cheaply available so any legislative limits in bauxite residue. Some negative feature or minor impediment is of the uranium does dissolve in the Bayer a potential barrier to change. Assessing process but it subsequently re-precipitates both the actual risk, and the perceived and is associated with the coarser bauxite risk to the stakeholders for any particular residue fraction. Meanwhile thorium is not application is crucial. Some important risk affected by low temperature extraction factors to consider are discussed below. process and is most often associated with the fine bauxite residue fraction. Data for Leaching of heavy metals Australian derived bauxite residue shows The leaching of metals, especially a level of 0.005 – 0.2 Bq/g for the sand heavy metals, into the environment is fraction and 0.15 – 0.6 Bq/g for the mud sodium levels and high pH will be reduced a particular issue for any material that fraction due to 238U and 0.3 – 0.8 Bq/g when press filters are used. Accelerating is used in building products, bricks, for the sand fraction and 1– 1.9 Bq/g for carbonation by the use of carbon dioxide, roads, in construction, soil capping or the mud fraction due to 232Th and 0.07 intensive farming or acid neutralisation as soil amelioration. Soluble chromium is – 0.23 Bq/g due to 40K in mud fraction9. a first stage could also be considered to normally the element of most concern The International Atomic Energy reduce the pH. though arsenic can also be a problem for Authority (IAEA) Basic Safety Guide for some specific residues. This is generally marketable materials sets a limit of 1 Hazardous rating of bauxite only a particular issue when the materials Bq/g per radionuclide; for uranium this residue in some jurisdictions are exposed to high or low pH values. is equivalent to 81 mg/kg. From the There have been many discussions, Solubility/extraction tests of components published data for bauxite residue, this particularly in the EU, concerning the or aggregates (for example EN 12457 level does not representative a problem hazardous nature of bauxite residue in – Waste Acceptance Criteria Testing) or for bauxite residues although it should be particular in respect of its pH. If classified metal uptake studies in vegetation may all noted that the level measured for 238U and as a hazardous waste, this will add be necessary depending on the application 232Th on bauxite residue from the closed considerably to the cost of all aspects of in order to show that the bauxite residue Jamaican alumina plant at Moggetty was handling, storage and transport. Based will not be a problem in use. 0.97 and 0.32 Bq/g10. The values generally on a number of standard test criteria, Possible concerns over liability of present in local soil for 238U and 232Th were any waste material with a pH value above contaminating surrounding land may be 0.22 and 0.037 Bq/g respectively. 11.5 is often considered hazardous. a particular concern if the product is used A thorough understanding of the Implementation of an improved filtering in some way where the leachate from the radioactivity issues are most important operation, may reduce the pH of bauxite structure etc. could leach into a water when any application is considered. residue to a level that avoids skin and eye course. Public perception and concerns must irritation. be addressed as despite the data shown Radioactivity above, the radioactivity levels measured Moisture level Most bauxites will contain low levels have stopped a number of interesting A high moisture level will add to transport of radioactive elements, termed NORM applications proceeding. Examples costs and will be an issue if energy has to

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plant in Milaki but changing economic circumstances have put increased usage on hold. There has also been some historical usage of bauxite residue from the refinery in Tulcea in a local Romanian cement plant and also reportedly small- scale usage of bauxite residue from the Gandja alumina refinery in Azerbaijan in cement. The use of bauxite residue in cement in China was formerly several million tonnes a year but this has fallen because of the changes in construction industry standards and also a reduction in the number of plants operating a sinter or Bayer-sinter extraction route. It should be noted that the bauxite residue produced Fig 9. Use of Bauxaline in landfill capping in Provence from the sinter or Bayer-sinter extraction route is very different chemically from that be expended in driving it off in drying or some opportunities for the use of bauxite produced in a conventional Bayer alumina firing (calcination), so it is advantageous residue. This makes the transport cost issue plant. for the bauxite residue to have as high a even more critical when considering uses. The usage of bauxite residue in steel solids content as possible. Additives such manufacture is of the order of 70,000 to as starch have been used for dewatering Industrial scale successes 100,000 tonne/year, excluding China. The for very many decades but from the It is generally estimated that some 2 to iron ores that are normally used in iron and 1980s there was growing use of synthetic 3.5 million tonnes of the bauxite residue steel manufacture have an iron content flocculants. The use of plate and frame produced annually is used in some way of typically 55 to 70% with 66% being press filters goes back a very long period although reliable data is difficult to obtain available from many good quality sources. and was certainly being used in the 1940s. as it does fluctuate markedly from year to Meanwhile for comparison, bauxite It then seems to have fallen out of favour year as the economics change. residues have a typical range of iron of 3 and rotary drum filters became more Current estimates from various sources to 42%. It is important to consider these common. Now there is a trend back to are: contents and realise the difficulty in even the use plate and frame press filters being ᔢ Cement – 500,000 to 1,500,000 closely matching the economics against adopted to reduce water content, which tonnes; using virgin iron ore, especially at the can yield a moisture level of 26/27% or ᔢ Raw material/additive in iron and current price of iron ore. Some success lower. steel production – 400,000 to 1,500,000 has been achieved in China, particularly tonnes; in plants in Southern China where the Transport costs ᔢ Roads (see Figure 8)/landfill capping bauxite residue can have an iron content The logistics cost is very substantially (see Figure 9)/soil amelioration – 200,000 of up to 42%. Notably success has also increased if the material is classified as to 500,000 tonnes; been achieved using magnetic separation hazardous since special procedures must ᔢ Construction materials (bricks, tiles, techniques as a first stage of processing to be implemented during transportation. ceramics etc.) – 100,000 to 300,000 concentrate the iron fraction. The bauxite Whilst the high alkalinity does not impose tonnes; residue material is also wet and has a high a problem with corrosion of steel, it does ᔢ Other (refractory, adsorbent, acid sodium content, which is a disadvantage cause pitting of aluminium, which is a part mine drainage (Virotec), catalyst etc.) – in steel production. of the UN transport code. If the conversion 100,000 tonnes. The simultaneous recovery of other or use is not carried out at the alumina metals, for example titanium and refinery, the bauxite residue will almost Bauxite residue can provide valuable aluminium, would improve the economics certainly be competing with some other iron and alumina values in the production of using bauxite residue for iron recovery low cost ore, mineral or waste - reducing of Ordinary Portland cement. Excluding in steel production. The only non-Chinese the transport costs to as low as possible China, the use of bauxite residue in the plant using bauxite residue for making is therefore essential. All mitigating cement industry in the manufacture of steel is based in the Urals. The work on operations should be considered, e.g. clinker is estimated at approximately iron extraction from bauxite residue in pumping the bauxite residue to some 260,000 t/y almost all of which is from the the Southern Chinese alumina plants is other area and processing it, dewatering Nikolayev alumina plant in the Ukraine. discussed later. Several Indian sources of methods/aids, solar drying. The bauxite residue from Nikolayev is bauxite residue are relatively high in iron, A major trend since the 1980s has used in cement plants in the Ukraine, between 30 to 39%, and a considerable been the closure of small and medium Russia, Georgia, Moldova and Belarus. amount of work has been done to recover size alumina plants, perhaps 100,000 to The Nikolayev refinery blends the residue the iron values in the bauxite residue from 300,000 t/y annual production, in Europe produced to give the cement plant a the NALCO plant using the Romelt process and the growth of much larger plants, this consistent feed and the climate allows but whilst technically feasible, it was is especially true in Brazil and Australia. a reasonably low moisture product to uneconomic because of the high-energy The largest ones can produce more than be produced. There is modest usage costs involved in the process. 6 million tonnes per year of alumina. of bauxite residue from AdG’s plant in China is worth discussing separately as These larger plants are very often remote Distomon in cement production at a plant it devoting a very considerable effort into from large centres of population, which in Patras; further usage is restricted by the searching for and implementing reuse of is likely to mean there is a lower level of lack of dry storage. Much larger usage, up bauxite residue, much of it being driven industrial activity and consequently limit to 180,000 t/y was anticipated at a cement by Chinese Government initiatives8. China

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has shown the most dramatic change in decades has prevented its implementation References the last 10 years with alumina production until now. 1. Data published annually by World increasing from about 2.5 million tonnes Usage for road building and dyke/levee Aluminium, www.world-aluminium.org in 2000 to over 59 million tonnes by construction is estimated at 20,000 tonne/ 2. World Aluminium and the European 2015. The generation of bauxite residue year, however, some is used internally Aluminium Association “Bauxite Residue has grown to over 50 million tonnes a within each alumina site complex, often Management: Best Practice”, available from year, the alumina manufacturing routes for roads within the bauxite disposal the International Aluminium Institute, 10 King have traditionally been very different area. A considerable about of work has Charles II Street, London, SW1Y 4AA, UK and because of the nature of the indigenous been done in Western Australia by Alcoa on line from http://bauxite.world-aluminium. bauxite. Sinter routes or combined Bayer- in conjunction with Curtin University on org/refining/bauxite-residue-management. sinter routes were widespread but are using Red Sand™ in the construction html now declining sharply and the industry of roads12. In this process, the coarse 3. B. G. Purnell, “Mud Disposal at the has become more dependent on imported sandy fraction of the bauxite residue is Burntisland Alumina Plant”. Light Metals, 157 bauxites. This change in route has neutralised with carbon dioxide to create – 159. (1986). significantly changed the characteristics the Red Sand™. 4. H. H. Pohland and A. J. Tielens, “Design and composition of the bauxite residues Soil amelioration of acidic and sandy and Operation on Non-decanted Red Mud being produced. Hitherto much of the soils offers considerable opportunities Ponds in Ludwigshafen”, Proc. Int. Conf. imported bauxite was from Indonesia although current usage is limited and Bauxite Tailings, Kingston, Jamaica (1986). and Australia but curtailment of bauxite spasmodic. 5. E. I. Robinsky, “Current Status of the exports from Indonesia is changing the Sloped Thickened Tailings Disposal System”, nature of the bauxite residue yet again. Summary Proc. Int. Conf. Bauxite Tailings, Kingston, Traditionally the alumina plants in the The early history of bauxite residue Jamaica (1986). Northern part of China produced a residue storage involved using estuaries or land 6. J. L. Chandler, “The Stacking and Solar very high in calcium and silicon oxides but impoundment areas adjacent to the Drying Process for disposal of bauxite tailings low in iron oxide making them suitable factory as a low solids slurry. Disposal into in Jamaica”, Proc. Int. Conf. Bauxite Tailings, for cement production whilst those in rivers, estuaries or the sea was common Kingston, Jamaica (1986). the south of China have a residue high in for a number of years but this has now 7. B. K. Parekh and W. M. Goldberger, “An iron which makes the recovery of iron the ceased. Storage of bauxite residue as a assessment of technology for the possible most likely option for them to pursue. A dilute slurry in old mines, impounded utilization of Bayer process muds”, published very strong driving force in China has been areas or dammed valleys was widely by the U. S. Environmental Protection Agency, government imposed legislation requiring practised until the mid-1980s but since EPA 600/2-76-301. that bauxite residue is reused. then there has been a growing trend 8. Wanchao Liu, Jiakuan Yang, Bo Xiao, The manufacture of bricks, tiles and to higher solids storage method. More “Review on treatment and utilization of other building materials has been shown recently, filter presses to produce an bauxite residues in China”, in Int. J. of Mineral to be technically possible by many groups even higher solids residue have become Processing, 93 220-231 (2009). of workers from a wide variety of sources increasing common. In many ways it is 9. M.B. Cooper, “Naturally Occurring of bauxite residue using both fired and discouraging that despite so much work Radioactive Material (NORM) in Australian chemically bonded methods. Outside over the last century only some 2 to 3% of Industries”, EnviroRad report ERS-006 prepared China, however, whilst plants have started the 140 million tonnes of bauxite residue for the Australian Radiation Health and Safety up, production has not continued. produced annually is used in a productive Advisory Council (2005). Use of bauxite residue for capping way. Some of the applications have been 10. W. Pinnock and W. Graham, municipal landfills is carried out in France; economically beneficial for a number of ”Radioactivity in Jamaican Bauxite Waste”, the amount varies considerably from years and then factors have changed which Proc. Int. Conf., Bauxite Tailings, 113-117, year to year but is estimated at 40,000 renders them no longer economically Kingston, Jamaica (1987). to 100,000 tonne/year. It can only be viable. However, it is vital to consider how 11. Y.Pontikes, G.N. Angelopoulos, B. undertaken within a relatively small changes in process technology or demand Blanpain, “Radioactive elements in Bayer’s radius of each refinery depending on requirements over time means that ideas process bauxite residue and their impact in local transport costs and the availability previously considered not worth exploiting valorization options”, Transportation of NORM, of other covering/capping materials; can become viable and commercially NORM Measurements and Strategies, Building the maximum distance that the residue attractive. Materials, Advances in Sci. and Tech, 45 2176- can effectively be transported for this From the process side, improvements 2181 (2006). application is estimated to be about 75 include: The increasing use of press 12. W.K.Biswas and D. J. Cooling, km. Municipalities will normally wait until filters will give residues with lower “Sustainability Assessment of Red SandTM an entire site is full before remediating/ moisture levels, lower soda levels, lower as a substitute for Virgin Sand and Crushed capping it, hence the wide variation in contaminants, lower pH levels; the higher Limestone”, J. of Ind. Ecology, 17(5) 756-762 usage between years. The bauxite residue efficiency electro-magnets that are now (2013). must be in a form that can readily be available allows for more effective iron carried in trucks on public roads. Possible recovery from bauxite residue. Meanwhile concerns are dust from the bauxite residue the growing demand for scandium in when dry and heavy metal leaching aluminium alloys or the demand for characteristics. particular rare earth elements also present Somewhat related, has been the use as new opportunities. In addition, public, a soil amendment/conditioner for acidic/ corporate and government attitudes have sandy soils; on large-scale trials this has never presented such an encouraging Acknowledgements been shown to be safe and beneficial, environment for developing and Thanks are due to Katy Tsesmelis of World especially in controlling high levels of implementing bauxite residue uses. ᔢ Aluminium and George Banvolgyi for very phosphorous. Controversy over two helpful comments on the manuscript.

Aluminium International Today March/April 2016