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Metal Manufacturing Processes and Energy Systems
Published in Swapan Kumar Dutta, Jitendra Saxena, Binoy Krishna Choudhury, Energy Efficiency and Conservation in Metal Industries, 2023
Swapan Kumar Dutta, Binoy Krishna Choudhury
Pure aluminum hydroxide is precipitated as a white fluffy solid as the solution is cooled down to ambient conditions and is separated and calcined at 980°C in a rotary kiln to produce pure alumina. However, in the process, a large amount of impurities—called red mud—is separated out and must be stored in a holding pond, as it is highly basic and so far remains a challenge for productive use. As its color signifies, “red mud” is rich in oxides of iron and also a bit of titanium.
2 Sequestration
Published in S. Komar Kawatra, Advanced Coal Preparation and Beyond, 2020
The dangers of red mud are primarily due to its quantity, alkalinity, and traces of embedded toxic metals. In 2010, a retaining wall on a red mud pond in western Hungary failed, releasing a tremendous quantity of red mud into the local ecosystem in what was described in 2014 as the largest release of caustic waste in history (Anton et al., 2014). However, despite the scale of the disaster, the ecosystem showed significant signs of recovery after only a handful of years. Thus, if the red mud’s alkalinity could be reduced the threat it would pose to the environment would likely decrease proportionally, correspondingly increasing the ease with which the red mud can be handled. Furthermore, as the toxic metals present within it, such as vanadium, chromium, cobalt, nickel, and arsenic (Anton et al., 2014), have industrial uses, this increased ability to handle red mud may lead to additional processing opportunities to increase the recovery of nonaluminum valuables. Some red muds contain a considerable concentration of rare earth metals, which may also present a valuable extraction opportunity.
Sustainable and Economically Profitable Reuse of Bauxite Mining Waste with Life Cycle Assessment
Published in Hossain Md Anawar, Vladimir Strezov, Abhilash, Sustainable and Economic Waste Management, 2019
Hossain Md Anawar, Vladimir Strezov, Tanveer M. Adyel, Golam Ahmed
A wide variety of potential applications of bauxite residue have been reviewed, yet there is no economically viable and environmentally acceptable solution for the utilization of large volumes of bauxite residue. Although methods have been developed for maximum recovery of sodium and aluminium from bauxite residue, further investigations to reduce the required high reaction temperatures are needed to ensure that recovery of other metals can be made more economical. Efforts are being carried out to study the amelioration of red mud by possibly incorporating a pH-reduction processing step during disposal and include studies on processes based on acid neutralization, CO2 treatment, seawater neutralization, bioleaching and sintering. Further research is required on residue neutralization technologies to reduce the alkalinity/high pH of bauxite residue, which is the most important barrier to its and disposal management (Rai et al., 2012).The evidence of low levels of injured bacterial cells indicated that adding various nutrients and/or hay to bauxite residue helped to grow bacteria including the species of Bacillus, Lactobacillus, Leuconostoc, Micrococcus, Staphylococcus, Pseudomonas, Flavobacterium and Enterobacter and formed organic acids that lowered the pH from 13 to about 7.0 (Hamdy and Williams, 2001).
Application potential of Chrysopogon zizanioides (L.) Roberty for the remediation of red mud-treated soil: an analysis via determining alterations in essential oil content and composition
Published in International Journal of Phytoremediation, 2021
Meenu Gautam, Madhoolika Agrawal
Bauxite residue (also referred as red mud) is an industrial solid waste, which originates during the beneficiation of bauxite into aluminum through Bayer process (Samal et al. 2013). Global annual generation of red mud is about 120 million tons with an overall residue of 2.7 billion tons being accumulated on land (Narayanan et al.2020). Red mud is highly alkaline and saline residue with low water retention capacity, high levels of metal(oid)s i.e. aluminum (Al), iron (Fe), sodium (Na), calcium (Ca), vanadium (V), titanium (Ti), silica (Si), lead (Pb), nickel (Ni), chromium (Cr), cadmium (Cd), and arsenic (As), and poor bioavailability of essential nutrients (Gautam and Agrawal 2017a). Even though several advanced technologies are available to utilize red mud in making construction materials, compounding roofs, road sub-layers, bricks, tiles, cement, and bituminous mixtures, but there are still no policies for reutilization of the waste on large scale (Lima et al.2017). Besides, such technological innovations are not only cost extortionate, but also not environmentally benign options. Hence, only 2–3% of the generated residue has been known to be utilized in a productive manner and rest is disposed off on land or stored in impoundments without proper pretreatment (Gautam and Agrawal 2019). Inappropriate disposal and/or storage of red mud may cause environmental contamination, thereby negatively affecting living organisms (Xue et al. 2016; Gautam et al. 2017).
Red Mud: Fundamentals and New Avenues for Utilization
Published in Mineral Processing and Extractive Metallurgy Review, 2021
Red mud has been seen as a material that is detrimental to wildlife and a serious harm to the environment. Some research has gone into actually using red mud to improve the conditions of solid by removing dangerous heavy metal ions. This is possible because red mud that has been neutralized with seawater contains minerals known as hydrotalcites, which can adsorb to heavy toxic elements in solution (Palmer et al. 2010). Results from these experiments were performed with red mud samples from the Gove plant in Australia and it was found the seawater neutralized red mud could remove dangerous metals in aqueous solution like arsenate, vanadate, and molybdate (Palmer et al. 2010). Another study conducted arsenic adsorption experiments with raw red mud and red mud that had been activated through heat-treatment and through acid washing. The results showed that arsenic can absorb to regular red mud and activated red mud but the adsorption to activated red mud which contained a lower pH was more effective (Altundogn et al, 2002).
Overview On Extraction and Separation of Rare Earth Elements from Red Mud: Focus on Scandium
Published in Mineral Processing and Extractive Metallurgy Review, 2018
Ata Akcil, Nazym Akhmadiyeva, Rinat Abdulvaliyev, Pratima Meshram
Red mud is a waste product produced by extraction of alumina from bauxite ores. The characteristic red color can be attributed to hydrated iron (III) oxide, i.e., hematite, whereas large amount goethite are responsible for the characteristic yellow-red color. The amount of red mud has been rising rapidly, increasing by approximately 120 million tons per annum (Mtpa) (Abhilash et al., 2014a; Power et al., 2011). The average pH value of red mud is 11.3 ± 1.0. It is an alkaline product and needs disposal. It is also considered as a hazardous material owing to its high alkalinity. There are several disposal methods for red mud which include marine discharge, lagoons, dry stacking and dry cake disposal. In the year 2005, Japan had made an agreement with the International Maritime Organization regarding the discontinuation of bauxite residue disposal into the sea by 2015. The country had reported that the previous 5 years had witnessed a bauxite residue disposal rate of 1.0 Mtpa in the sea at two different locations. The main disadvantage of the lagoon method of disposal is the risk it possesses towards humans and wildlife upon contact with caustic liquor and residue. Apart from that, it also causes contamination of surface and ground waters. In the year 2010, the collapse of a red mud reservoir led to the release of approximately one million cubic meters of red mud in western Hungary which caused the death of ten people, while 150 people were injured (Marshal, 2014).