Sustainable Utilization of Red Mud for Gas Denitrification and Desulfurization: A Review

Utilization of red mud in road base and subgrade materials: 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.

The utilization of red mud, which is a residue from the extraction of aluminum from mined bauxite ore, as a plant growing medium, needs to be studied further. There are some chemical aspects that may hinder the growth of, or even cause mortality in, plants such as very high pH, electrical conductivity (EC) and exchangeable Na (Na exch ), and very low nutrient elements content. The objective of this study was to investigate the effects of adding Ultisol soil material, mixed with compost, both soil ameliorating agents, to red mud for use as a growing medium for Sengon ( Paraserianthes falcataria ) seedlings. This study was conducted in two stages, namely: washing of the red mud, and trial planting in the greenhouse using different combinations of the soil ameliorants. Washing of the red mud with tap water was intended to reduce the levels of Na, EC, and pH. Trial planting in the greenhouse was carried out in 2-factorial Completely Randomized Design (CRD). Factor 1 was the proportion of the mixture of Ultisol soil material (sm-Ultisol) and red mud, viz : (1) 1500 g red mud + 0 g sm-Ultisol, (2) 1000 g red mud + 500 g sm-Ultisol, and (3) 750 g red mud + 750 g sm-Ultisol. Factor 2 was the dosage of compost that was mixed with the red mud and sm-Ultisol, namely: 0, 58.6, and 117.2 g/polybag which corresponded to 0, 2.5 and 5 kg/planting hole, respectively. The results of the trial indicated that washing the red mud could reduce the level of EC from 28.70 dS m -1 to 2.68 dS m -1 ; but it reduced pH and Na exch only from 11.91 and 149.38 cmol (+) kg -1 to become 10.55, and 66.74 cmol (+) kg -1 , respectively. A better outcome was obtained after the red mud was washed and then, mixed with sm-Ultisol up to 1:1 proportion in which resulted in lower rates of pH, EC, and Na exch from 10.28, 2.53 dS m -1 and 62.79 cmol (+) kg -1 to 8.65, 2.07 dS m -1 and 45.01 cmol (+) kg -1 , respectively. The treatment of using a mixture of 750 g red mud + 750 g sm-Ultisol, and adding compost at 117.18 g/polybag gave the best result in improving the chemical property of the red mud growing medium, and producing the best plant growth among all treatment combinations.

Applications of red mud as an environmental remediation material: A review

Environmental assessment, management and utilization of red mud in China

Red mud is generated from alumina production through bauxite digestion with caustic soda. Ma'aden aluminum production estimated the abundance in a million tons as 2.65:1:2 for bauxite, alumina, and red mud, respectively. The real challenge when it comes to red mud pertains to storage capacity; many solutions have been put forward in different industries, and in this study, the utilization of the red mud waste material is presented as a potential weighting material that could be incorporated into the design of drilling fluid systems. This study provides an assessment of the utilization of red mud as a drilling fluid, and it provides directions for the use of red mud in drilling mud systems as a filtration agent and as a finely divided solid used as a weighting material to increase the density of a given drilling fluid system. This study investigates the viability of red mud as an effective additive to drilling fluid and its effect on rheology and filtration. Different techniques are employed in red mud characterization and performance evaluation. The study assesses red mud as an inert solid in a drilling fluid system by investigating the drilling fluid rheology, apparent viscosity (AV), plastic viscosity (PV), and yield point (YP) before and after hot rolling at 150 °F, in addition to filtration properties under low-pressure, low-temperature and higher-pressure, higher-temperature conditions (at 150 °F and a differential pressure of 250 psi). Also, the study highlights the red mud solid characterization, material preparation, and acid dissolution at 150 °F. This study attempts to view the red mud situation from a practical application angle (primarily in the oil and gas industry). Test results show stable drilling mud fluid properties when utilizing red mud solid additives as weighting agents. The drilling mud exhibits relatively low plastic viscosity, gel strength, excellent sag behavior, and reasonable filtration control, even under HPHT conditions in aqueous-based fluids. The material dissolves in acid. Accordingly, red mud provides a viable option for weighting agents and filtration control.

Red mud (RM) is a by-product of extracting of alumina from bauxite. Red mud contains high quantities of alkali-generating minerals and metal ions, which can cause significant environmental damage. Many valuable components such as rare-earth elements, Al, and Fe, in RM are difficult to be utilized owing to their particle size and alkalinity. Thus, developing an economical and efficient technology to consume a large amount of RM can efficiently solve RM disposal issues. This paper systematically reviews the comprehensive utilization methods for reducing RM environmental pollution and divides the comprehensive utilization of RM into three aspects: the effective extraction of valuable components, resource transformation, and environmental application. Based on resource, economic, and environmental benefits, the development of new technologies and new processes with market competitiveness, environmental protection, and ecological balance should be the prerequisite for the low-energy, low-pollution, low-cost, and high-efficiency comprehensive utilization of RM. The direction of future research to solve RM disposal issues is also suggested.

Effect of ultrafine red mud on the workability and microstructure of blast furnace slag-red mud based geopolymeric grouts

Mechanical properties and micro-mechanism of loess roadbed filling using by-product red mud as a partial alternative

Objectives Total waste that is generated in South Korea per land area is ranked in fourth among OECD countries. Therefore, the importance of resource circulation through waste recycling should be emphasized. Red mud, one of the industrial wastes, is a by-product of the aluminum smelting process and is generated about 30 million tons per year. Methods Red mud is high in iron content and has a red color and strong alkalinity. Rice husk, a by-product of agricultural production, can be made into biochar through pyrolysis process and it also has alkalinity. By using red mud and biochar as soil amendment, experiment was conducted. The purpose of the experiment is to improve the quality of the acidic soil and find the growth-characteristics (length, width, weight, dry weight) through pot experiment. Results and Discussion The acid soil with a pH level of 4.84 was increased to pH 7.14 after adding the amendment. The CEC of the soil with 7.56 cmolc/kg was increased to 9.80 cmolc/kg. Pot experiment showed better results of growth-characteristics in treatment than control. The analysis of heavy metals showed below standard level in both control and treatment. Conclusion Therefore, the pot experiment showed that red mud and biochar could be used to improve acid soil effectively. Key words: Red Mud, Biochar, Soil Improvement, Amendment, Acidic Soil

Evaluation of red mud as a polymetallic source – A review

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

Experimental research on magnesium phosphate cements modified by red mud

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

Utilization of red mud as a stabilization material for the preparation of clay liners