Red Mud Research Articles

Influence of red mud as a catalyst in the thermocatalytic reforming process

AbstractThis work studies red mud, a residue from the processing of bauxite, as a support catalyst in the thermocatalytic reforming (TCR) process, using wood, digestate, and straw as case studies. Thermocatalytic reforming is a thermochemical process for the conversion of biomass into biofuels, combining intermediate pyrolysis and catalytic reforming and resulting in high‐quality biofuels. The quantity and quality of the catalyst in the postreformer is vital as it influences the reactions taking place in it. Normally, nonreactive components of the char produced in the process act as the catalyst in the postreformer but adding a support catalyst may improve the products. In this work, red mud is introduced in the process by mixing it with the feedstock in a ratio of 1:3. The results, in comparison with normal TCR experiments on the same feedstock materials, show that the introduction of red mud into the process generally reduces the biochar yield and generally increases the biogas and product water yields, and the bio‐oil yield remains constant. Its introduction also increases the hydrogen fraction of the gas and tends to reduce the nitrogen and sulfur content of the products, thus improving their quality. These observations are consistent across feedstock materials and postreformer temperatures. The results therefore suggest that red mud is a good support catalyst for increasing the gas yield, increasing the hydrogen fraction of the gas, and improving the quality of the products from the TCR process.

Deformation characteristics of red-mud embankment under monotonic and cyclic loads

The rapid growth in the production of the red mud has led to the shortage of land for stockpiling in recent years. Although red mud has been considered as the filling material for embankments, the deformation characteristics of a red-mud embankment under traffic loads has not yet been clarified. To promote its application in embankment construction, a series of centrifuge model tests of red-mud embankment under monotonic and cyclic loads were conducted. The deformation and failure processes of red-mud embankment under normal and overproof traffic loads were analyzed. The results show that the deformation characteristics of red-mud embankment varied significantly depending on the value of the external load. The deformation induced by monotonic load was greater than that induced by the cyclic load of the normal traffic load. The monotonic and cyclic loads of normal traffic load induced similar influential areas, and their deformation processes can be divided into rapid and slow growth parts. Shear failure occurred in the red-mud embankment under overproof traffic load. The same load increment induced more deformation of red-mud embankment after failure. Under reasonable dry density and water content, the deformation of red mud was acceptable, thus meeting the engineering requirements of embankment construction.

Grey-Taguchi approach to optimize the tribological performance of hybrid composites

Modern manufacturing technology is evolving, necessitating the creation of materials with higher wear resistance. This research endeavors to forecast the dry sliding wear performance of AL6061-B4C-RM hybrid composites by employing Taguchi and grey relational analysis approaches. Present study applies the L16 Taguchi approach to optimize the process parameters specific wear, and coefficient of friction (COF) at four different levels. Using multiple responses for optimization for both responses, a single process parameter setting is obtained via grey relational analysis. In AL6061 composites, varying weight proportions of Boron Carbide particles (B4C) were added as reinforcements while keeping the red mud (RM) content constant at 2 %. To recognize the dominant factor, analysis of variance (ANOVA) was implemented, and the outcomes of the assessment showed speed plays a crucial role, followed by the weight percent of reinforcement and the load in determining the specific wear rate and COF. A research trial was completed to confirm the outcomes obtained from the combination of optimal parameters.

GGBFS and Red-Mud based Alkali-Activated Concrete Beams: Flexural, Shear and Pull-Out Test Behavior

Geopolymers and antacid-enacted fasteners have accumulated critical interest as promising development and fixing materials because of their exceptional properties. Also, they bring about less contamination contrasted with regular concrete cements. Geopolymers address a clever class of suggested restricting materials blended through the basic enactment of bountiful aluminosilicate materials. The usage of geopolymer materials from side effects offers a critical decrease in carbon impression and yields positive natural effects. Geopolymer is progressively recognized as a plausible substitute for OPC concrete. In this review, sodium-based antacid activators, especially sodium metasilicate (Na2SiO3), were used for different blend extents. The boundaries researched included NaOH arrangements with a grouping of 8 M, alongside a Na2SiO3/NaOH proportion of 1. This paper evaluates the fundamental characteristics of geopolymer cement beams, employing red mud and GGBFS in powdered form as complete replacements for traditional concrete. Six bar specimens are tested under a two-point static loading condition, all cured at room temperature under ambient conditions. Of the six beams, three were exposed to flexural conduct testing with a molarity of 8 M, while the excess three beams were tried for shear conduct. The outcomes of testing geopolymer beams subjected to shear and bending loads indicated that the beams incorporating aluminum slag performed better than those incorporating blast furnace slag. Both types also demonstrated promising results compared to beams incorporating OPC, highlighting their potential environmental benefits compared to cement use. Doi: 10.28991/CEJ-2024-010-05-09 Full Text: PDF

Study on Partial Replacement of Cement with Red Mud in Mortar

Abstract: An investigation is carried out on red-mud based cement mortar to understand its mechanical property performance. A proportionate replacement of cement is done to the range of 0% to 20% with 5% intervals with red mud. The mortar was prepared with a proportion of 1:4 and the behavioral performance of mortar were studied as concern towards its compressive strength. The results we would expect that the mortar exhibited better performance at 0% to 20% replacement and as well as red mud mortar is denser than normal cement mortar.

Analysis of the efficiency of the application of natural coagulants

The object of the study is the process of purifying natural waters using coagulants of natural and industrial origin. The subject of the study is the analysis of the effectiveness of coagulants of natural and industrial origin. Today, there is great interest in finding alternative methods of water purification that would be more economical and environmentally friendly. The availability of clean and safe water is especially important during times of martial law. Coagulants of natural origin can be an affordable and effective means of water purification and disinfection. One of the important advantages is availability, which indicates the possibility of becoming an alternative to chemical coagulants. Thus, there is a need to study the possibility of using natural coagulants both on an industrial scale and in emergency conditions. This study presents a characterization of existing coagulants of natural origin, an analysis of the effectiveness of their use, comparison with chemical analogues, as well as an analysis of the effectiveness of using Moringa oleifera as a natural coagulant. During the work, two coagulants were synthesized from red mud from aluminium production. A comparative analysis of coagulants synthesized from red mud, Moringa oleifera, aquatone and aluminium sulphate was carried out. All reagents were used to remove turbidity and other impurities. The studies were carried out 3 times in different seasons of the year. All results were compared to determine the most effective coagulant and its dose. As a result, it was found that all of these coagulants can be used and reduce water treatment costs at local water treatment plants. The natural coagulant can be used in areas where there is no access to a central water supply, especially in war zones.

PYROMETALLURGICAL PROCESSING OF RED MUD

PYROMETALLURGICAL PROCESSING OF RED MUD

Improved macro-microscopic characteristic of gypsum-slag based cementitious materials by incorporating red mud/carbide slag binary alkaline waste-derived activator

The expensive cost and high carbon footprint of commercial alkaline activators hindered the promotion and industrialization of geopolymers. The rising demand for geopolymer as low carbon and excellent building materials will lead to enormous research works towards to low carbon alkaline activator. This study aimed to explore the impact of red mud (RM)/carbide slag (CS) binary alkaline wasted-derived activator (RCA) on the macroscopic and microscopic properties of RCA activated cementitious materials (RCM) prepared with titanium gypsum (TiG) and granulated blast furnace slag (GBFS). It is proposed to adjust the pH value of solid waste powder for calibrating the waste-derived activator, prepare RCM and explore the relationship between its mechanical properties and hydration products. The research showed that the highest flexural and compressive strengths at 28 days occurred with a dosage of 0.8 wt% CS, meeting the strength requirements of 52.5 R Portland cement. It is worth noting that RCM with binary alkaline waste-derived activators with appropriate pH values can exhibit excellent early mechanical properties. Raising the pH of RCA significantly improves the compressive and flexural strength, increasing them to 30.7 MPa and 6.3 MPa at 3 d, and to 60.7 MPa and 10.8 MPa at 28 d. The primary hydration products of RCM include C(N)-A-S-H gels, ettringite, and gypsum crystal phase, which contribute to the development of mechanical strength. Due to the difference in the alkaline environment required for the growth of C(N)-A-S-H gel and ettringite crystal, the increase in RCA pH value has been found to both inhibit the growth of ettringite to a certain extent and promote the precipitation of C(N)-A-S-H gels, improving the chemical structure of the hydration products and the pore distribution characteristics of the RCM. Furthermore, the research has been successfully applied in a pilot test in Jiaozuo, China. RCM introduces a novel concept for the efficient and industrial-scale utilization of solid waste. This study can provide a fundamental academic and industrialized support and a novel concept for the whole solid waste cementitious materials especially from alkaline industrial solid wastes such as RM and CS.

Carbonation reaction properties and reaction mechanisms of red mud under different carbon dioxide pressures

The carbonation utilization of solid waste such as red mud is an important strategy to deal with greenhouse gas emission control. To explore the carbonation reaction properties of red mud particles under different CO2 curing pressures, experiments were designed. The results show that in the range of 0–14 bar, as the CO2 curing pressure increases, the carbonate content in the carbonation product gradually increases and becomes stable. When the CO2 pressure increases to 18 bar, the amount of carbonate minerals will further increase. The pore change characteristics of red mud particles before and after carbonation are not significant, and no obvious carbon accumulation is observed on the surface of the particles. The carbonation of red mud particles is a liquid phase reaction, and the carbonation products are mainly deposited in the solution. The CaCO3 produced by carbonation is mainly calcite and aragonite types. The relevant results can provide reference for the carbonation utilization of red mud.

A Mini Review on Sewage Sludge and Red Mud Recycling for Thermal Energy Storage

Sewage sludge and red mud, as common industrial waste, have become a research hotspot in the field of achieving carbon peaking and carbon neutrality, reducing carbon emissions, and solving environmental problems. However, their treatment and disposal have always been a difficult problem in the environmental field. Utilizing these two materials for thermal energy storage can not only improve energy utilization efficiency but also further reduce carbon emissions during their treatment process, providing a new approach for sustainable development in the industrial sector. This article summarizes the research progress for the resource recovery of sewage sludge and red mud for direct thermal energy recovery and composite phase change energy storage. After proper treatment, sludge and red mud can be directly used as energy storage materials. In addition, sludge and red mud can be combined with phase change materials to prepare composite materials with an excellent energy storage performance. This composite has broad application prospects in fields such as solar energy utilization and building energy efficiency. However, there are still some challenges and issues in this resource recovery and utilization, such as potential environmental pollution during the treatment process, the long-term stability of energy storage materials, and cost-effectiveness, which require further research and resolution. The purpose of this paper is to evaluate the potential of sewage sludge and red mud as energy storage materials, to explore their feasibility and advantages in practical applications, and to reveal the research progress, technical challenges, and future development directions of these two materials in the field of thermal energy storage.

Amelioration of the physicochemical properties enhanced the resilience of bacteria in bauxite residues

Bacteria-driven strategies have gained attention because of their effectiveness, viability, and cost-efficiency in the soil formation process of bauxite residues. However, further investigation is needed to enhance the extreme environment of bauxite residues and facilitate long-term sustainable development of bacteria. Here, soil, phosphogypsum, and leaf litter were selected as amendments, and soil and leaf litter were also used as bacterial inoculants in a 12-month microcosm experiment with bauxite residues. The results showed significant improvements in physicochemical properties, including alkalinity, organic carbon content, nutrient availability, and physical structure, when bauxite residue was mixed with amendments, particularly when different amendments were combined. The diversity, structure, and function of the bacterial community were significantly enhanced with the amelioration of the physicochemical properties. In the treated samples, especially those treated with a combination of different amendments, the relative abundance (RA) of alkali-resistant bacterial taxa decreased, whereas the RA of some common taxa found in normal soil increased, and the structure of the bacterial community gradually changed towards that of normal soil. A strong correlation between physicochemical and biological properties was found. These findings suggest that rational application of soil, phosphogypsum, and leaf litter effectively improves the environmental conditions of bauxite residues and facilitate long-term sustainable bacterial communities.

Synergistic catalytic mechanism of red mud in the co-gasification of spirit-based distillers’ grains and sewage sludge

Experiments of co-gasification of spirit-based distillers’ grains (SDG) and sewage sludge (SS) were carried out with red mud (RM) by using a self-designed fixed-bed gasifier. The effects of RM addition, gasification reaction temperature, SS and SDG blending ratio and other factors on the gasification reaction characteristics and synergism were investigated. The results are as follow: RM had catalytic effect on SS and SDG co-gasification, which can enhance the gasification reaction and H2 yield; increasing the temperature can enhance the gasification reaction and reduce the syngas H2/CO; with the increase of SDG, the H2 yield gradually grew; with the rise of SS, the gasification reaction gradually augmented. The catalytic mechanism was mainly due to the redox cycle of Fe2O3 in RM, which can promote the water transfer reaction. At the same time, the eutectic mixture of K, Na, Ca, Fe and other metal elements at high temperatures was the main reason for the synergistic effect.

Integration of lactic acid biorefinery with treatment of red mud from alumina refinery: win–win paradigm for waste valorization

The cost of detoxification and neutralization poses certain challenges to the development of an economically viable lactic acid biorefinery with lignocellulosic biomass as feedstock. Herein, red mud, an alkaline waste, was explored as both a detoxifying agent and a neutralizer. Red mud treatment of lignocellulosic hydrolysate effectively removed the inhibitors generated in dilute acid pretreatment, improving the lactic acid productivity from 1.0 g/L·h−1 to 1.9 g/L·h−1 in later fermentation. In addition, red mud could replace CaCO3 as a neutralizer in lactic acid fermentation, which in turn enabled simultaneous bioleaching of valuable metals (Sc, Y, Nd, and Al) from red mud. The neutralization of alkali in red mud by acids retained in lignocellulosic hydrolysate and lactic acid produced from fermentation led to effective dealkalization, rendering a maximum alkali removal efficiency of 92.2 %. Overall, this study offered a win–win strategy for the valorization of both lignocellulosic biomass and red mud.

Collaborative effects of red mud and phosphogypsum on geotechnical behavior of cement-stabilized dredged clay

Collaborative effects of red mud and phosphogypsum on geotechnical behavior of cement-stabilized dredged clay

A systematic characterization of the mixture of red mud and bottom ash as a geomaterial: an efficient utilization in subgrade pavement

A systematic characterization of the mixture of red mud and bottom ash as a geomaterial: an efficient utilization in subgrade pavement

Mechanical and microstructural analysis of cemented tailings backfill by copper slag through alkaline activation emphasizing red mud

Copper slag (CS) exhibits pozzolanic activity in alkaline cementitious systems, making it a suitable supplementary cementing material for cemented tailings backfill (CTB) with reduced carbon emissions. However, its utilization is constrained by the unacceptable cost of alkaline materials, e.g., NaOH and CaO. In this paper, the CTB bound by CS activated using red mud (RM) has been investigated through mechanical and microstructural analysis. The results show that RM content and curing time significantly affect UCS development throughout the CTB life cycle. The CTB containing 1.5 % RM and 3 % RM exhibit lower strength values at 28 d compared to the control group without RM, measuring 3.07 MPa and 2.65 MPa, respectively. Despite this reduction, the cost calculation confirms that using RM as a partial substitute for NaOH reduces the CTB cost by approximately 50 %. Microstructural analysis reveals that the RM particles in CTB were bonded together by gels, and the amounts of gels on the surface of the aggregated particles and other crystals increased with the increasing RM contents. Further, its strong alkalinity facilitates the decomposition of Al monomers from RM and partially replaces Si in the C-S-H gel to form C-A-S-H gel. This study corroborates the feasibility of preparing CTB bound by CS activated using RM, providing new insights into the application of RM and CS.

Study on the synergistic effects and eco-friendly performance of red mud-based quaternary cementitious materials

Red mud, as the primary byproduct of processing bauxite into aluminum, raises environmental concerns due to its significant alkalinity and substantial heavy metal content. Addressing the limitations of traditional methods, this study proposes an innovative solution to utilize red mud, steel slag, fly ash, and phosphogypsum together to produce a new type of low-carbon, environmentally friendly cementitious material. Utilizing advanced techniques such as X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, mercury intrusion porosimetry, and scanning electron microscopy with energy-dispersive spectroscopy, this study conducted a comprehensive evaluation of cementitious materials, revealing their synergistic mechanisms. Furthermore, artificial neural networks and genetic algorithms were employed to optimize the mix ratio of the quaternary binder, aiming to predict and enhance the material's mechanical strength. Research shows that quaternary cementitious materials outperform traditional binary and ternary materials in compressive strength, hydration properties, microstructure, and environmental performance. Particularly, the increased content of calcium-aluminate-silicate-hydrate and sodium-calcium-silicate-aluminate-hydrate gels and a denser matrix structure highlight the synergistic effect in the hydration reaction of the quaternary system. Through mix proportion optimization, a significant enhancement in compressive strength up to 21.4 MPa is achieved. Environmental assessment shows that the composite material effectively solidifies Na+, with non-renewable resource and energy consumption reduced by 84.7% and 83.8%, respectively, compared to traditional cement, highlighting its environmental and energy-saving advantages. This approach addresses red mud storage, produces green building materials that meet standards, and fulfills resource and environmental goals.

Red mud in high-strength ceramics production

The work is devoted to the creation of high-strength ceramic materials with technogenic waste fillers.Purpose: Investigation of the ceramic and composite production based on chemical and metallurgical wastes to create new types of high quality constructional ceramics.Methodology/approach: The use of refractory clay with the addition of high-iron bauxite sludge as the main raw material. Bauxite sludge functions in compositions with aluminosilicate raw materials at burning at 1100 to 1200 °С, reduce to sintering due to its melting at 1150 °С.Research findings: Refractory clay compositions with red mud in the amount of 20 to 50 % at the burning temperature of 1050 °С, provide the ceramic formation possessing the compressive strength 1.3 to 1.5 times higher than that of clay samples without additives, i.e., 91 and 122–132 MPa, respectively.Value: The obtained ceramic compositions based on red mud determine a production of high-strength anorthite and anorthite-helenite ceramics using dry pressing.

Evaluation on performances of cold asphalt mixture containing recycled waste glass and red mud

The current study aims to assess the performance of cold asphalt mixture by incorporating recycled waste glass (e.g., 20% and 30% by weight of total mixture), and red mud, as substitutes for conventional aggregates. Laboratory tests were conducted to analyze the influence of waste glass on the workability energy index and compactability energy index. The resistance to cracking of asphalt mixture was evaluated using the indirect tensile asphalt cracking test, while assessments of rutting and moisture vulnerability were performed via the Hamburg wheel tracking test. Dynamic modulus test was also conducted to examine the response of the waste glass-modified asphalt mixture under dynamic loading and different temperatures. In addition, a 400-meter pedestrian road was constructed to evaluate the practical utilization of waste glass in real-world conditions. Results indicated that the addition of higher waste glass content reduced the theoretical maximum specific gravity due to density differences between waste glass and recycled asphalt. Increase in waste glass content led to a higher demand for compaction energy. The mixture containing 30% waste glass required over 22% more compaction energy compared to control mixture. While the 20% waste glass mix showed similar characteristics to conventional asphalt in terms of indirect tensile strength and rutting resistance. In contrast, the 30% mix exhibited notably weaker properties, which were 12% lower in CTindex and three times lower in stripping resistance. Dynamic modulus results showed that with 30% waste glass, the elastic behavior of asphalt mixture was strongly reduced. In general, the study recommended that the optimal utilization of waste glass in cold asphalt mixtures containing recycled asphalt and red mud appears to be at the 20% level, based on comprehensive laboratory and testbed results.

Waste Treatment by Waste: Study on Iron Recovery from High-Iron Red Mud by Spent Cathode Carbon Block as Reductant and the Behavior of Na/F

Waste Treatment by Waste: Study on Iron Recovery from High-Iron Red Mud by Spent Cathode Carbon Block as Reductant and the Behavior of Na/F