HIGH VOLUME RESOURCES FROM BAUXITE RESIDUE

Alcoa World Alumina (Alcoa) has been investigating opportunities to produce products from bauxite residue for many years. While many products have been produced, their economics are generally unfavourable due to the high volumes of materials that are required to be processed. A new approach has been taken to investigate high volume products in an attempt to improve economics and utilisation of the bauxite residue resource. Three of these potential products are described here, being Red Sand, Alkaloam^®, and Red Lime^TM.

Red Sand has a nominal particle size of +100 micron and is physically little different to crushed bauxite. In Alcoa’s Western Australian refineries, Red Sand constitutes up to half of the bauxite residue going to impoundment areas. Trials indicate that this sand can be processed to provide various industrial raw materials. Such materials include: a sand suitable for concrete, a material that is acceptable as general landfill or in road base construction, and a material containing high iron content.

Alkaloam^® is the fine-grained residue often referred to as red mud. Intensive research has shown the benefits of adding this material to sandy soils, common in coastal regions of Western Australia (WA). Alkaloam^® has properties that can elevate the pH of the acidic soils and also retain phosphorus, reducing overall fertiliser use and protecting sensitive waterways. This work is being expanded in the USA and Brazil.

Red mud has many potential uses within the construction industry. Due to the high content of aluminium and iron in the bauxite residue, there is a potential for red mud to be used as cement feedstock. Preliminary analysis indicated that both brown mud and red mud could be used, limited by the proportion of iron and salt content. Other uses include tile, brick, block and concrete manufacture.

Red Lime^TM is a by-product of the refining process. This material has a high acid neutralising value and could be more effective at pH control than most available products, due to the fine particle size and entrained sodium carbonate. Testing indicates this product has potential use as an agricultural lime, a general neutralising agent and as a feedstock for cement manufacture.