Global recycling experience of red mud - a review. Part i: pyrometallurgical methods

Abstract

This review considers the papers aimed to find an effective solution to the red mud utilization problem. Red mud or bauxite residue is a hazardous materials that are generating during production of alumina by the Bayer process. Depending on the composition of bauxite and the technology, production of 1 ton alumina forms from 0.9 to 1.5 tons of this waste. The global inventory of red mud is estimated at about 4 billion ton in 2015. The main quantity of bauxite residue is not processed, but pumped into land-based ponds and it leads to environmental pollution. In 2010 in Hungary a pond containing red mud were collapsed, freeing about 700 thousand m3 of liquid waste, as a result 10 people were died, about 350 houses were destroyed and significant regions were polluted. Red mud obtained by different plants has various chemical and phase compositions. Despite this fact the main components of red mud is iron-containing minerals, so bauxite residue can be considered primarily as a raw material for the metallurgical industry. This part of the review considers pyrometallurgical methods for of red mud treatment, including both methods of low-temperature reduction at temperatures of 1050 - 1200 °C and high-temperature reduction melting, as well as utilization methods of the resulting slags. These slag utilization methods can be used for extraction of alumina, titanium and rare-earth metals, obtaining building materials such as various cements, mineral wool and flux materials for metallurgy. Methods of alkali removing, drying and agglomeration of red mud also considered. It has been shown that the best ways of bauxite residue recycling are the pyrometallurgical methods with obtaining of iron-containing product and slag for the production of building materials or metallurgical fluxes. These techniques make possible to utilize a large amount of red mud with exception of additional waste formation. This is the first part in a series of three related reviews examining the world experience of red mud recycling by various ways.

Influence of Na2CO3 and K2CO3 Addition on Iron Grain Growth during Carbothermic Reduction of Red Mud

“…Red mud contains many valuable elements such as Fe, Al, Ti, and Sc, but the Fe content is highest and can reach 45% [21], so the development of a robust and cost efficient method of iron extraction is still the aim of many studies. The most common ways of iron extraction are reduction smelting at 1450-1650 • C and reduction roasting at 1050-1200 • C followed by magnetic separation of reduced iron [22]. Reduction roasting is more economically viable than reduction smelting because it consumes less energy.…”

Spatial Distribution of Elements, Environmental Effects, and Economic Potential of Technogenic Waste Materials of Pavlodar Aluminum Plant (Pavlodar, Kazakhstan)

“…This separation is conditional because in most cases the proposed technologies include both pyrometallurgical and hydrometallurgical transformations. There are many critical reviews in the literature on how red mud is treated, both considering all applications Klauber et al, 2011;Power et al, 2011) and describing specific areas, such as their use for pollutant treatment (Liu et al, 2011) extraction of metals from them (Liu & Naidu, 2014), pyrometallurgical processing (Zinoveev et al, 2018), use in construction (Siverio Lima et al, 2017). Despite numerous studies, only a small proportion of red mud is still recycled, owing to the low profitability of most technologies, the high capital cost of the development of new products, and the complexity of sales.…”

Solvent Extraction of Iron(III) from Al Chloride Solution of Bauxite HCl Leaching by Mixture of Aliphatic Alcohol and Ketone

“…Iron oxide (Fe2O3), along with silica (SiO2), is the main impurity in the alumina production industry. When using alkali methods (Bayer, sintering), iron remains in an alkali-insoluble residue-red mud [1,2]. To extract Fe2O3 in a separate fraction, hydrothermal treatment with the addition of FeSO4 is used [3].…”