Leaching of rare earths from bauxite residue (red mud)

“Red mud” or “bauxite residue” is a highly alkaline waste generated from alumina refinery with a pH of 10.5–12.5 which poses serious environmental problems. Neutralization or its treatment by sintering in presence of additives is one of the methods for overcoming the caustic problem as it fixes nearly all the leachable free caustic soda present in red mud. In the present study, feasibility of reducing the alkaline nature of red mud by sintering using fly ash as an additive via Taguchi methodology and its use for brick production, as an alternative to clay, is investigated. The analysis of variance (ANOVA) shows that sintering temperature is the most significant parameter in the process. A pH of 8.9 was obtained at 25–50% of red mud and 50–75% fly ash with water and temperature of . Alternatively 50% of red mud can be mixed with 50% of fly ash with water at temperature of to get a pH of about 8.4. The mechanism of this process has been explained with also emphasis on chemical, mineralogical, and morphological analysis of the sintered red mud. The results would be extremely useful in utilization of red mud in building and construction industry.

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Red Mud-Blast Furnace Slag-Based Alkali-Activated Materials

Sustainability ◽

10.3390/su132011298 ◽

2021 ◽

Vol 13 (20) ◽

pp. 11298

Author(s):

Alessio Occhicone ◽

Mira Vukčević ◽

Ivana Bosković ◽

Claudio Ferone

Keyword(s):

Compressive Strength ◽

Blast Furnace ◽

Red Mud ◽

Blast Furnace Slag ◽

Bauxite Residue ◽

Sodium Silicate Solution ◽

Silicate Solution ◽

Waste Products ◽

Furnace Slag ◽

Alkali Activated

The aluminum Bayer production process is widespread all over the world. One of the waste products of the Bayer process is a basic aluminosilicate bauxite residue called red mud. The aluminosilicate nature of red mud makes it suitable as a precursor for alkali-activated materials. In this work, red mud was mixed with different percentages of blast furnace slag and then activated by sodium silicate solution at different SiO2/Na2O ratios. Obtained samples were characterized by chemical–physical analyses and compressive strength determination. Very high values of compressive strength, up to 50 MPa, even for high percentage of red mud in the raw mixture (70 wt.% of RM in powder mixture), were obtained. In particular, the higher compressive strength was measured for cubic samples containing 50 wt.% of RM, which showed a value above 70 MPa. The obtained mixtures were characterized by no or scarce environmental impact and could be used in the construction industry as an alternative to cementitious and ceramic materials.

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Red Mud (RM) and Soil Amelioration

Advances in Environmental Engineering and Green Technologies - Amelioration Technology for Soil Sustainability ◽

10.4018/978-1-5225-7940-3.ch009 ◽

2019 ◽

pp. 151-167 ◽

Cited By ~ 1

Author(s):

Amit Kumar

Keyword(s):

Red Mud ◽

Sodium Hydroxide Solution ◽

Bauxite Residue ◽

Acid Soils ◽

Large Area ◽

Vegetation Growth ◽

Ground Water Pollution ◽

Trace Metal Content ◽

Rich Material ◽

Ph Range

Rapid growth in industrialization, which is necessary and inevitable for society progress, has also created negative encroachment. Red mud produced during alumina production has strong alkanity in a pH range of 10-13% because of the sodium hydroxide solution used in the refining process. The base is strong enough to kill plant and animal life, and due to finer particle and trace metal content, it creates soil contamination, ground water pollution, and suspension in ocean; hence, we need precautions while we use this waste to add with soil. Red mud occupies a large area or its deposition in it. Red mud has properties similar to sandy clay. Red mud has property similar to clay and sand, even if it does not contain quartz or clay mineral. Bauxite residue/red mud can be mixed with variant type of saline soils, acid soils organic rich material, and silicate soil suitable pH conditions were achieved to promote vegetation growth.

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