A review of the red mud utilization possibilities

Environmental assessment, management and utilization of red mud in China

Proposal for resources, utilization and processes of red mud in India — A review

Red mud is the main by-product of the production of alumina according to the Bayer process. It is a highly alkaline, brick-red suspension. It is characterized by a diversity of chemical and mineralogical composition. The main elements in red mud are Fe, Al, Si, Ti, Na, Ca, and they account for about 90% of the mass of the mud. In addition to these, a large number of other components can be found in minor quantities. Most elements are present in the form of oxides and hydroxides in various minerals. The demand for aluminum is constantly growing, the amount of discharged red mud is continually increasing. The annual amount of red mud produced globally, is already estimated at 200 million tons, and further growth is expected. High production rates and only minimal and sporadic utilization of red mud have resulted in the accumulation of large quantities of disposed red mud, so that the global red mud stockpile is estimated at more than 5 billion tons. In addition to financial costs, the disposal of red mud also poses certain risks to the environment. For this reason, the safe disposal of red mud is one of the main concerns of all alumina producers. Reducing the amount of red mud that is disposed of, and consequently reducing the risks and costs, requires constant efforts to find procedures for its valorization. The possibilities of valorization of red mud are diverse. It has been shown that red mud can be successfully used in many areas, such as construction, metallurgy, chemical industry, environmental protection, agriculture, etc. Analyzing the patents related to the use of red mud, it can be observed that 12% of the patents refer to the wastewater and waste treatment. The heterogeneous composition of red mud indicates the possibility of its application as a composite sorbent. The application of red mud as a low-cost sorbent has been extensively investigated, and favorable results have been obtained in the sorption of metals and metalloids, radionuclides, phosphates, nitrates, fluorides, dyes and phenols, etc. In order to increase the sorption capacity of red mud and obtain a more environmentally friendly sorbent, various treatment techniques are applied. These treatment techniques can modify the physical and chemical properties, which can lead to a change in alkalinity, specific surface area and porosity, a change in the number of active sorption sites, and its surface charge can also be changed. Modifications of red mud to remove various types of pollutants have shown promising results. Many studies have shown that red mud can be used as an efficient and low-cost sorbent for removing heavy metal cations from solutions, such as Pb2+, Cu2+, Zn2+ , Cd2+, Ni2+, Co2+, Sr2+, Cs2+, as well as for the treatment of waste water and leachate from landfills and mines. During the removal of heavy metals from solutions using red mud, various mass transfer phenomena occur: physical and chemical adsorption, surface precipitation, co-precipitation, ion exchange, precipitation, complexation, hydration, dissolution, etc. Despite the numerous possibilities of application and the benefits that arise from it, we still do not have a significant utilization of red mud.

Minerals engineering conferences

Bayer red mud is a strong alkaline solid waste discharged during alumina production. Due to large emissions and strong alkalinity, red mud is now mostly dammed or buried, which not only occupies huge land but also contaminates the surrounding ecosystem, causing the risk of collapse and landslide. In addition to its overall utilization in building materials, agriculture, the environment, and the chemical industry, red mud also contains valuable metals such as sodium, aluminum, iron, titanium, and scandium and is considered to be an important secondary resource. In this paper, the physicochemical properties and hazards of red mud are first introduced, and then, the overall utilization of red mud is summarized. Then, the latest research progress on the separation and extraction of valuable metals from red mud is reviewed in detail and a new comprehensive utilization method is recommended and evaluated. This paper also provides suggestions for the future development direction of the comprehensive utilization technology of red mud.

Study on the utilization of red mud (bauxite waste) as a supplementary cementitious material: Pathway to attaining sustainable development goals

Performance evaluation of red mud as a construction material – A review

Peatlands are suboptimal lands that can be improved its quality to be used for agricultural cultivation. One of which is by using red mud and biofertilizer. Red mud, a by-product of bauxite processing, is widely available in West Kalimantan. Red mud has high pH, electrical conductivity, exchangeable sodium and base saturation. Biofertilizers are products containing selected microorganisms that can help enhance plant growth and yield. This study aims to examine the effects of red mud and biofertilizer applications on peat quality improvement and their impact on the growth and yield of hybrid corn. The experiment was arranged in a randomized block design (RBD) with two factors. The first factor was red mud with three dosage levels: control (l0), 6 tons/ha (l1), and 12 tons/ha (l2). The second factor was biofertilizer with three types: control (p0), Mycofer at 10 g/plant (p0), and Provibio at 10 ml/l (p2). The results showed that red mud at a dose of 12 tons/ha significantly affected soil pH, electrical conductivity, plant growth, and hybrid corn yield. The interaction of 12 tons/ha red mud and Provibio biofertilizer significantly increased sodium content and achieved the highest uptake of phosphorus, potassium, calcium, and magnesium.

Utilization of red mud in road projects is an effective way to consume large amounts of red mud on a large scale. In order to meet the requirements for road performance, a modified material, Heinchem, has been developed on the basis of extensive experiments, and the long-term environmental risks of red mud modified by this material have been investigated. By collecting and modifying original red mud samples, a series of continuous leaching tank experiments are carried out based on the exposure scenario analysis. According to the leaching content of pollution in the original and modified red mud, the characteristic pollutants are identified. The release mechanism of these characteristic pollutants in the modified red mud is revealed, and the long-term release amount is predicted. Furthermore, in light of the actual road use scenario of the modified red mud, a risk assessment model is established and used to simulate the release, migration, and transformation of characteristic pollutants during the use of modified red mud as roadbed material. The groundwater environmental risk is then assessed. Finally, an acute toxicity test of earthworms and a seed germination test are conducted to investigate the impact of the modified red mud on the farmlands. The results showed that the proposed red mud modified materials have obvious curing effects on V, As, Se, Mo, and F. When the leaching contents of V, Cr6+, Cr3+, As3+, Se4+, Se6+, Mo, and F in the modified red mud were lower than 0.15 mg/L, 0.1 mg/L, 0.2 mg/L, 0.012 mg/L, 0.012 mg/L, 0.012 mg/L, 0.075 mg/L, and 1.2 mg/L, respectively, the environmental risk of modified red mud during long-term road use is acceptable. This study provides a new way for the resource utilization of red mud.

Red Mud is the solid residue generated from Alumina refinery during the process of bauxite ore processing through Bayer’s process. Typical generation of red mud is 1.5 tons of red mud per ton of alumina produced. The disposal and storage of red mud has been a concern for the alumina industry since its inception, more than a hundred years ago. With the increase in alumina production, the magnitude of the problem is getting multiplied. Its alkaline nature (Na2O ~ 3-7%) and fine size make red mud unsuitable for many applications; a limited utilization is reported in cement industries as one of the raw mix components for cement. The present work deals with the utilization of red mud in geopolymer based paving blocks. Alumina, silica and alkali are the essential items required for geopolymer preparation. Having all these in red mud, the current study attempted to use the same in geopolymer based products. The focus has been on bulk utilization of red mud; target strength of 20 MPa after 28 days of curing (M20 grade) has been the goal as this strength is sufficient for many applications. The study focused on optimizing the red mud content, alkali concentration, fly ash content, etc. The samples are tested for its compressive strength and leachability. The study reveals that significant amount of red mud incorporation is possible with products conforming to USEPA 1311 norms.

An experimental investigation of utilizing waste Red Mud in soil grouting

Red mud is a solid waste residue of the digestion of bauxite ores with caustic soda for alumina production. Its disposal remains a worldwide issue in terms of environmental concerns. During the past decades, extensive work has been done by a lot of researchers to develop various economic ways for the utilization of red mud. One of the economic ways is using red mud in cement production, which is also an efficient method for large-scale recycling of red mud. This paper provides a review on the utilization of red mud in cement production, and it clearly points out three directions for the use of red mud in cement production, namely the preparation of cement clinkers, production of composite cements as well as alkali-activated cements. In the present paper, the chemical and mineralogical characteristics of red mud are summarized, and the current progresses on these three directions are reviewed in detail.

Transferring red mud to efficient adsorbent for the adsorption and immobilization of Ni(Ⅱ) from aqueous solution

Red mud is one of the major wastes produced from aluminum industry which utilize bauxite (Al2O3) as raw material to extract aluminum out of it. This research work investigates the suitable utilization for a particular red mud samples depending upon its permeability and hazardous characteristics. Red mud was stabilized with Fly ash which is another solid waste material produced from thermal power plants and in combination with gypsum. The Fly ash content was varied from 0%, 15% and 25% and gypsum content is varied from 0%, 0.25% and 0.75% of dry weight of the red mud. The main objective of this research work is to evaluate the environmental impact of red mud utilization and explore the means to allay the leaching problem. The effect on the toxic metals in the leachate coming out from the compacted mix when fly ash is added solely or when combined with gypsum to red mud is to be clarified. All the experiments were carried out on each mix to obtain an optimum mix. The permeability and leachate characteristics are studied for different flowing periods from 1 to 7 days of each sample combination. An attempt further was made to understand the metal concentration in the leachate of raw red mud, red mud – fly ash and red mud-flyash–gypsum combinations. It is revealed from the test results and analysis that stabilization with proper proportioning the hazardous metal concentration and permeability of the red mud will decrease with increase in flow period.

Bauxite residue is the waste generated during alumina production by Bayer's process. The amount of bauxite residue (40-50 wt%) generated depends on the quality of bauxite ore used for the processing. High alkalinity and high caustic content in bauxite residue causes environmental risk for fertile soil and ground water contamination. The caustic (NaOH) content in bauxite residue leads to human health risks, like dermal problems and irritation to eyes. Moreover, disposal of bauxite residue requires a large area; such problems can only be minimised by utilising bauxite residue effectively. For two decades, bauxite residue has been used as a binder in cement industries and filler/reinforcement for composite materials in the automobile industry. Valuable metals and oxides, like alumina (Al2O3), titanium oxide (TiO2) and iron oxide Fe2O3, were extracted from bauxite residue to reduce waste. Bauxite residue was utilised in construction and structure industries to make geopolymers. It was also used in the making of glass-ceramics and a coating material. Recently bauxite residue has been utilised to extract rare earth elements like scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), neodymium (Nd) and dysprosium (Dy). In this review article, the mineralogical characteristics of bauxite residue are summarised and current progresses on utilisation of bauxite residue in different fields of science and engineering are presented in detail.