Application of modified red mud in environmentally-benign applications: A review paper

Abstract

Red mud (RM) is a waste product that results from bauxite refining via the Bayer process. Its disposal remains an issue which raises significant environmental concerns, particularly if disposed on land or water bodies. Much research has been done on the use of red mud for environmentally-benign applications such as wastewater treatment, catalysis, the production of construction materials and glass ceramics, and for the recovery of metals. This paper reviews the current efforts made in the utilization of red mud as a valuable industrial by-product, which in turn should minimize its harmful impact on the environment. This detailed review compiles and highlights a variety of novel applications of modified red mud as a coagulant, an adsorbent for wastewater treatment, as well as, its use in catalytic processes and in building materials. The physico-chemical properties of red mud can be tuned by a range of treatment methods include acidification, neutralization and heat treatment. As revealed from the literature reviewed, modifications on red mud for the removal of various types of contaminants have shown promising results. However, further amendment and modifications on red mud are needed to utilize this industrial waste in many other industrial applications.

Research on High-Pressure Hydrochloric Acid Leaching of Scandium, Aluminium and Other Valuable Components from the Non-Magnetic Residues Obtained from Red Mud after Iron Removal

“…Figure 13 demonstrates the influence of S:L ratio and concentration of the acid on the recovery degree of aluminum, titanium, iron, and scandium. As can be seen, the dissolution degree of Ti drastically grows up with an increase of acid concentration and S:L ratio that is consistent with equation (6). It has to be taken into account that an increase of S:L ratio led to a drop not only aluminum extraction degree, but also scandium extraction degree that accords with previous studies [63,64].…”

“…The lack of efficient processing technologies is the main reason why red mud is out of use and accumulated in special sludge storage facilities, which have an adverse impact on the environment and even have led to the technogenic catastrophe [3]. It has found that red mud is proved to be a promising material for the obtaining of coagulants and can be used as an adsorbent for heavy metals in wastewater; it can also be utilized in a wide range of catalytic applications [5], as well as for a production of various building materials [6].…”

Research on High-Pressure Hydrochloric Acid Leaching of Scandium, Aluminum and Other Valuable Components from the Non-Magnetic Tailings Obtained from Red Mud after Iron Removal

“…The lack of efficient processing technologies is the main reason why red mud is out of use and accumulated in special sludge storage facilities, which have an adverse impact on the environment and have even led to technogenic catastrophe [3]. It has found that red mud is proved to be a promising material for obtaining coagulants and can be used as an adsorbent for heavy metals in wastewater [5]; it can also be utilized in a wide range of catalytic applications [6], as well as for a production of various building materials [7]. Thus, a promising way for the extraction of valuable components from red mud is the reduction roasting with obtaining of magnetic iron concentrate and non-magnetic tailings enriched in aluminum, titanium and REEs followed by the treatment of the tailings by high-pressure hydrochloric acid leaching.…”

New glass‐based binders from engineered mixtures of inorganic waste

“…It is typically separated from other minerals through the Bayer process, which produces a large amount of inorganic waste. Globally, every tonne of alumina produced implies between 1 and 1.5 tonnes of red mud 1 . The waste deriving from the Bayer process, usually termed as “red mud,” is a caustic slurry, containing Al 2 O 3 (5‐30wt.%), SiO 2 (3‐50wt.%), and Fe 2 O 3 (5‐60wt.%) as major components, but also featuring toxic pollutants, in the form of heavy metal (Cr, Ni, Cu, Pb, etc.)…”

“…The handling of highly toxic constituents hinders but does not prevent red mud up‐cycling: multiple attempts to transform it into useful products have been reported 1–10 . Those based on vitrification treatment are generally favored in terms of stabilization of pollutants, 3–6 but some sustainability issues remain.…”