Mixture Of Red Mud Research Articles

Development of insulating backfill materials produced from the ternary mixtures of red mud, fly ash and preformed foam

Many public utility lines to transport power, water, natural gas, water, sewer, and communication are placed beneath trafficable areas. However, insufficient or inadequate backfill induces sudden subsidence, damage, or pothole on the road. This study aims to develop lightweight controlled low-strength materials (CLSM) with low thermal conductivity using the ternary mixtures of red mud to replace aggregate sand, high carbon fly ash, and preformed foam. Changes in flow consistency, air void characteristics, bulk unit weight, unconfined compressive strength (UCS), and thermal conductivity (k) of the tested materials with varying red mud contents were investigated as a function of the foam volume ratio (FVR). The results demonstrate that the UCS and k of tested materials decreased with increasing FVR due the decrease in unit weight, and a greater UCS but smaller k was observed at a given FVR with increasing red mud content because the inclusion of red mud in the lightweight CLSM mix design helps improve the stability of air bubbles and achieve uniform distribution of air voids. In addition, the red mud can act as a NaOH supplier, leading to the developed material had additional strength gain from the alkali activation. Thus, the developed insulating backfill material showed 43 % decrease in k while maintaining UCS similar to non-foam CLSM without red mud.

Integrated use of Bayer red mud and electrolytic manganese residue in limestone calcined clay cement (LC3) via thermal treatment activation

Limestone calcined clay cement (LC3) is a crucial low-carbon alternative for the future of the cement industry. Bayer red mud (RM) and electrolytic manganese residue (EMR), byproducts of aluminum and manganese production, respectively, pose significant environmental challenges due to their high volume and hazardous components. Utilizing these materials in LC3 not only mitigates disposal issues but also leverages their rich content of Al2O3 and SiO2, which resemble the properties of calcined clay after thermal treatment. This study investigates the mixture of RM and EMR with cement clinker, limestone powder, and gypsum to create a cementitious material with low carbon emissions. It examines the impact of thermal treatment temperature on RM and EMR reactivity and determines the optimal mix design. The findings indicate that the ideal thermal treatment temperature is 600 °C, with a 1:1 RM to EMR ratio, achieving the best mechanical properties and synergistic effects. The compressive strength of the RM/EMR-based LC3 reached 43.4 MPa at 28 days with a water-to-cement ratio of 0.35. Microstructural analysis reveals that RM, EMR, and limestone powder react to form monocarboaluminate in a calcium hydroxide-induced alkaline environment. Active Al2O3 and SiO2 in the RM and calcium sulfate in the EMR facilitate a secondary hydration reaction. The cementitious material, prepared from thermally activated RM and EMR, can potentially reduce CO2 emissions by 26.2 % and energy consumption by 14.9 % per ton compared to conventional Portland cement. This study demonstrates a sustainable approach for the cement industry, offering a viable solution for waste management and carbon reduction.

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

Improving Pb(II) Removal via Ascorbic Acid-Enhanced Red Mud Adsorption: Kinetics and Isotherm Analysis

This study explored the efficacy of red mud, an aluminum production by-product, as an adsorbent for Pb(II) ion removal from contaminated water and assessed the adsorption isothermal model and kinetics. Red mud, characterized by its richness in oxide minerals with reactive surfaces, has potential for heavy metal adsorption, but its capacity for larger ions like Pb(II) is limited. This research aimed to enhance red mud’s adsorption properties through modification with ascorbic acid. The modification process involved heating a mixture of red mud and ascorbic acid to its boiling point, followed by the formation of adsorbent beads using red mud and Na-alginate mixture dropped into a 2 % CaCl2 solution at −2 °C. The beads were tested over varying durations ranging from 30 to 210 min. The results indicated that ascorbic acid modification led to the transformation of minerals in red mud, improving its pore diameter, pore volume, and specific surface area of the adsorbent. The modified and unmodified red mud adhered to both Langmuir and Freundlich isotherms, with R² values converging to one, and displayed pseudo-second-order kinetics. Notably, the introduction of ascorbic acid augments the adsorption efficacy of red mud for Pb(II) ions from 84.8 % to a compelling 99.3 %. This underscores the augmented capability of ascorbic acid-modified red mud, highlighting its prospective applicability as a potent adsorbent in the remediation of heavy metal-contaminated water. HIGHLIGHTS Innovative Use of Red Mud: Explored the potential of red mud, a by-product of aluminum production, as an adsorbent for removing Pb(II) ions from contaminated water Ascorbic Acid Modification: Developed a novel modification process using ascorbic acid, including heating the red mud and ascorbic acid, enhancing the adsorption properties of red mud as pore diameter, pore volume, and specific surface area of the adsorbent Adsorption Isotherms and Kinetics: Conducted a comprehensive assessment of adsorption isothermal models and kinetics, with modified and unmodified red mud adhering to Langmuir and Freundlich isotherms and displaying pseudo-second-order kinetics Enhanced Adsorption Efficacy: the adsorption effectiveness is enhanced from 84.8 to 99.3 %, emphasizing its potential applicability for Pb(II) GRAPHICAL ABSTRACT

Alkali-activated binder based on red mud with class F fly ash and ground granulated blast-furnace slag under ambient temperature

Abstract This study examined the fresh and hardened characteristics of alkali-activated binders (AABs) based on ternary mixtures of red mud (RM), class F fly ash (FA), and ground granulated blast-furnace slag (GGBFS). The binders were prepared by dry mixing of 50% RM, 25–50% FA, and 0–25% GGBFS. The alkali activators were prepared from sodium hydroxide solution with different concentrations (6–14 mol) and sodium silicate solution. Curing at room temperature was adopted for the preparation of all samples. The flowability, setting time, and compressive and flexural strength tests were used to examine the properties of the resulting binders. To study the microstructural characterization, the scanning electron microscope, X-ray diffraction, and Fourier transformation infrared techniques were used. The results show that the flowability of the AAB decreases with higher GGBFS content, the addition of GGBFS reduces the setting time, and the incorporation of GGBFS increases the flexural and compressive strengths of the AAB. Microstructural and chemical analysis results indicate that in addition to geopolymer gel, calcium silicate hydrate (C–S–H) is formed upon adding GGBFS, producing a denser microstructure.

Assessing the potential of red mud and dehydrated mineral mud mixtures as soil matrix for revegetation

The disposal of red mud (RM) and dehydrated mineral mud (DM) presents a significant challenge for the global alumina industry. This study proposes a novel disposal method for RM and DM, which uses mixtures of RM and DM as a soil matrix for revegetation in the mining area. RM mixed with DM effectively alleviated its salinity and alkalinity. X-ray diffraction analysis indicated that reduction of salinity and alkalinity may be due to the release of chemical alkali from sodalite and cancrinite. Applications of ferric chloride (FeCl3), gypsum, and organic fertilizer (OF) improved the physicochemical properties of the RM–DM mixtures. FeCl3 significantly reduced available Cd, As, Cr, and Pb content in the RM–DM, while OF significantly increased the cation exchange capacity, microbial carbon and nitrogen, and aggregate stability (p < 0.05). Micro-computed tomography and nuclear magnetic resonance analysis showed that amendment with OF and FeCl3 increased the porosity, pore diameter, and hydraulic conductivity in the RM–DM mixture. The RM-DM mixtures had low leaching of toxic elements, indicating low environmental risk. Ryegrass grew well in the RM–DM mixture at a ratio of 1:3. OF and FeCl3 significantly increased the ryegrass biomass (p < 0.05). These results suggested that RM–DM amended with OF and FeCl3 has a potential application in the revegetation of areas after bauxite mining.

Feasible synthesis of magnetic zeolite from red mud and coal gangue: Preparation, transformation and application

A feasible synthesis of magnetic zeolite from the mixture of industrial solid wastes (red mud and coal gangue) was proposed. The preparation conditions, formation mechanism and adsorption performance of magnetic zeolite were investigated. Magnetic zeolite with uniform distribution of zeolite and magnetite could be successfully synthesized at the alkali reducing calcination conditions of n(Na:Al:Si) = 3.6:1:1, 600 °C, 1.5 h and the hydrothermal conditions of n(Na:H2O) = 2.8:1, 90 °C, 9 h. During this process, aluminosilicates in the mixture of red mud and coal gangue could be transformed into sodium-containing phases and zeolite A in turn; meanwhile, hematite in red mud could be reduced by carbon in coal gangue to transform into magnetite. The prepared magnetic zeolite showed excellent adsorption capacity and reusability for heavy metals. The maximum adsorption capacity for Cu2+, Cd2+ and Pb2+ reached 76.2, 92.2 and 178.4 mg/g, respectively, which could be attributed to the different ionic radius of heavy metals.

A Concept Scheme for the Joint Processing of Red Sludge and Largetonnage Waste from the Oil and Petrochemical Industries

It has been established that in the process of joint heat treatment of a mixture of red mud – quartz-leucoxene concentrate, a change in the chemical composition occurs with the formation of pseudobrookite, which has an increased chemical activity compared to the original quartzleucoxene concentrate. It has been established that the product of the combined heat treatment of red mud and acid tar consists of a mixture of aluminum, iron, and titanium sulfates that are readily soluble in water. Calcium sulfate and silicon compounds have been isolated as insoluble impurities. It is confirmed that in order to achieve the maximum degree of interaction, the mixture of red mud and acid tar must be heated at a rate of no more than 1–2 °C/min until 550 °C and time 60 min.

Red mud industrial waste translated into green electricity production by innovating an ingenious process based on Hydroelectric Cell

Globally a prominent hazardous industrial waste red mud (RM) residue is released in million tons everyday from alumina refinery. One of the best options to utilize red mud is the fabrication of Hydroelectric Cell (HEC) to produce green electricity, has been reported. Hydroelectric Cell is a 21st century phenomenal revolutionary invention to produce green electricity by water splitting at room temperature by oxygen-defects and nanopores deliberately created in metal oxides. HECs have been fabricated to produce green electricity by using mixture of red mud and iron oxide (RMFe). Splitting of water molecule heterolytically takes place on the cation-oxygen vacancy pair (Mδ+-Voδ−) present on the surface of RM and RMFe pellets. It has been observed from the Williamson-Hall, plots and Photoluminescence analysis that RMFe particles exhibit large strain and defects due to inter-ionic diffusivity of different metal cations. More hetero-ionic pairs of Fe3+-Voδ-, Ca2+-Voδ- and Al3+-Voδ- present on the RMFe surface increase the adsorption and chemidissociation of water. The RM and RMFe based HECs have delivered 7 mA and 17 mA peak current and voltage 0.8 V and 1.02 V. Red mud utilization in the fabrication of Hydroelectric Cell is a significant step towards waste management and wealth creation.

Preparation of a Novel Cement from Red Mud and Limestone

Red mud (RM) is an industrial waste obtained from the Bayer process which is usually discharged into marine or disposed into a landfill causing pollution for the surrounding water, air, and soils. Thus, disposal of RM is an environmental concern, and it should be recycled effectively. Because RM consists of iron- and aluminum-rich phases, it is possible to be processed into cementitious material and utilized for construction purposes. This research fabricated a type of cement from the mixture of RM and limestone. The mixture was sintered at temperature of 1180 °C to obtain the clinker of the novel hydraulic cement with C2S, C3A, and C4AF minerals. In which, C2S, C3A, and C4AF are respectively belite, alite, and tetra-calcium aluminoferrite compounds that are characteristic hydraulic minerals of Portland cement clinker. The specifications of this cement were tested and evaluated in this study such as chemical and mineralogical compositions, fineness, specific surface area, mechanical strength after 3, 7, and 28 days.

The use of red mud and kaolin waste in the production of a new building material: Pozzolanic pigment for colored concrete and mortar

The state of Para is one of the greatest producers of mineral substances in Brazil. Kaolin for paper coating industry and bauxite for alumina and aluminium production are amongst the most important commodities. The latter is responsible for the generation of red mud, a well-known residue from Bayer process. The kaolin processing plants are also responsible for the generation of large amounts of wastes, in this case, very fine-grained kaolinite (white mud). The research aimed to find a final destination for such residues by developing new building materials. The proposed material is a pozzolanic pigment produced through calcination and grinding of mixtures of red mud and kaolin waste. The pozzolanic pigments provided increased mechanical strength and color stability of the colored mortars relative to the inert pigment. The pozzolanic characteristics of the pigments reduced the leaching of the mortars. The new material has proven to be promising in its application as an innovative construction material, with the possibility of using these residues in a market that is little explored in Brazilian civil construction: colored mortars and concrete.

Modeling and Optimization of Gas-Solid Fluidization of Binary Mixtures using Box-Behnken Experimental Design

The influence of different factors on the fluidization of a binary mixture of red mud and aluminum was investigated. A new model was developed for predicting pressure drop through the solid bed using experimental data of other work. Statistical analysis based on response surface methodology has been used to develop correlations for bed pressure drop with three independent factors, minimum fluidization velocity (Umf), red mud to aluminum ratio (R/A), and static head (Hs). The design of experiments offers a best alternative to study the effect of factors and their response with the minimum number of experiments. The hydrodynamic characteristics of fluidization, bed pressure drop, superficial gas velocity (Umf), red mud to aluminum ratio (R/A), and initial static bed height (Hs) were modeled and optimized. ANOVA has been used to analyze the system parameters on bed pressure drop. A model of bed pressure drop was found to have a correlation coefficient of 0.98. The measured values of bed pressure drop from RSM were found to match the experimental values very well.

Evaluation of the performance of bentonite and red mud mixture as a shield in radioactive waste landfills

In the present era, due to various industrial developments, there is a need to use different applications of nuclear energy. But the leading challenge is the management of nuclear waste, which emits dangerous rays such as gamma rays. This research aim is to create a layer to be used as a protective coating against radiation in low-level waste landfills. In this paper, bentonite is used as a base material and red mud as an additive. Also, to determine the linear attenuation coefficient (µ), a combination of bentonite with 0, 15, 30, and 45% red mud with bentonite was used. To perform a linear attenuation coefficient test, the NaI (Tl) detector and the source of Co 60 were used at two energy levels of 1173 and 1332 keV. The results of laboratory tests show that the addition of red mud has improved the parameter of the linear attenuation coefficient of radiation at both energy levels so that the energy level of 1173 keV and 1332 keV with the addition of 45% red mud has improved by 16 and 12%, respectively.

Evaluation on Microstructure Stability and Thermal Resistant Ability at High Temperature of Ternary-Blended Geopolymer

Stability of microstructure and heat resistant ability at high temperature is one of the important properties in ceramics or silicate materials which are normally exposed with fire such as refractories and insulation or other materials used in furnaces. This study used a ternary-blended geopolymer which was synthesized from an optimized mixture of red mud (RM), rice husk ash (RHA), diatomaceous earth (DE), and water glass solution (WGS) with silica modulus of 2.5. The geopolymer samples were tested thermal properties of heat resistance (%), volumetric shrinkage (%), mass loss (%) at 1000°C to evaluate thermal resistant ability. Changes of microstructure of the ternary-blended geopolymer samples were also characterized before and after exposed at high temperature using methods of X-ray diffraction (XRD), Thermogravimetric analysis or thermal gravimetric analysis (DTA-TGA), and Scanning electron microscope (SEM). The experimental results showed the ternary-blended geopolymer has high thermal stability and unchanged microstructure even at high temperatures. Hence, the geopolymer in this study is suggested to apply as an insolation with the upper limit of temperature to work at 1000°C.

Hemp Fiber Reinforced Red Mud/Fly Ash Geopolymer Composite Materials: Effect of Fiber Content on Mechanical Strength.

Novel hemp fiber reinforced geopolymer composites were fabricated. The matrix was a new geopolymer based on a mixture of red mud and fly ash. Chopped, randomly oriented hemp fibers were used as reinforcement. The mechanical properties of the geopolymer composite, such as diametral tensile (DTS) (or Brazilian tensile) strength and compressive strength (CS), were measured. The geopolymer composites reinforced with 9 vol.% and 3 vol.% hemp fiber yielded average DTS values of 5.5 MPa and average CS values of 40 MPa. Scanning electron microscopy (SEM) studies were carried out to evaluate the microstructure and fracture surfaces of the composites. The results indicated that the addition of hemp fiber is a promising approach to improve the mechanical strength as well as to modify the failure mechanism of the geopolymer, which changed from brittle to “pseudo-ductile”.

Technological modeling of joint leaching of oily rolling scale and red mud

From the analysis of data on beneficial use of red mud and oily mill scale, a new direction of recycling has been formulated: the joint processing of these wastes to produce liquid products. Technological modeling of the stage of joint water treatment of a mixture of red mud and oily mill scale was performed at an enlarged laboratory unit. The yields and compositions of the products were determined. A batch of washed sludge was sent for research on obtaining ironcontaining raw materials for subsequent pyrometallurgical processing. With component ratio of 1:1, solid to liquid ratio of 4, temperature of 95 °C and duration of 2 hours, 6.3 kg of the mixture were processed, 6.58 kg of washed precipitate with a moisture content of 21.3 % and 12.6 dm3 of the final solution were obtained. The specific volume of water evaporation was determined to be 31.3 dm3/h per 1 m2 of pulp surface. Compositions of the precipitate iron (54.4 %) and the final solution (1.1 – 1.3 mg/dm3) were established, which indicates an almost complete accumulation of iron in the precipitate. Concentrations in the products of processing impurities were determined: silicon, aluminum, phosphorus, sulfur, sodium oxide and organics. According to the results, a technological scheme for the joint processing of red mud and oily mill scale was developed and ways of using the process products were outlined: sludge – for iron, filtrate – for industrial treatment, evaporated and wash water – for leaching. Using the example of cooperation between enterprises of the Kamensk-Uralsky Industrial Unit, the hardware process diagram is considered. It is advisable to use the data obtained to implement the technology, in particular, to develop technological regulations for the design of a pilot installation.

Desilication and recycling of alkali-silicate solution seeded with red mud for low-grade bauxite utilization

When low-grade high-silica bauxite undergoes desilication by alkaline leaching, a large amount of alkali-silicate solution will be produced. To realize its recycling, the alkali-silicate solution needs to be desiliconized. In this study, the effectiveness of red mud and a mixture of red mud and CaO as desilication reagents of the alkali-silicate solution are compared and the desilication mechanisms were analyzed. Results show that when adding 30–50g/L of red mud, the desilication rate is only 36–38% while adding 30g/L of red mud and CaO mixture with a calcium-silicon ratio of 1 reaches a desilication rate of ∼89%. Analyses by SEM-EDS and other mean show that this is mainly due to the growth of sodalite seed crystals in red mud and its synergistic desilication with CaO. Bauxite underwent cyclic desilication and the alumina/silica ratio was increased from ∼4.1 to >7.5. Effective utilization of red mud and alkali-silicate solution greatly reduces the cost of the desilication process, thereby making it applicable to low-grade bauxite in the Bayer process.

Evaluation on Formation of Aluminosilicate Network in Ternary-Blended Geopolymer Using Infrared Spectroscopy

This study used an optimized mixture of red mud (RM), rice husk ash (RHA), diatomaceous earth (DE), and water glass solution (WGS) with silica modulus of 2.5 to produce geopolymer-based material. The geopolymer product was tested engineering properties which are in good agreement of ASTM requirements for building materials. For microstructure, the geopolymer samples were characterized by using Fourier-transform infrared spectroscopy (FTIR) and focused on evaluation on formation of aluminosilicate network in the ternary-blended geopolymer. The results showed that tetra-silicates or acid silicic (Si (OH)4 or H4SiO4) dissolved and reacted with the iron oxide (Fe2O3) in RM and DE to form the oligomer precursors of sialate-O-Si-O-Al-O-, sialate-siloxo-O-Si-O-Al-O-Si-O-, sialate-disiloxo-O-Si-O-Al-O-Si-O-Si-O-, tetra-silicate [SiO4]4-, and tetra-aluminate [AlO4]4-. The formation of sodium alumino-silicate iron hydroxide polymeric network were easily detected by vibrational modes of –T–O–T– and –T–O–Na units (T refers to tetrahedral such as that of Si or Al) and of –OH and H–O–H. As well as, there were appearances of the membered ring or chain structural units of geopolymers.

Effect of industrial sludge-soil mixtures on germination of white mustard and wheat

Many industrial process produce different kind of sludge as by-product. Those various sludge-types can contain heavy metals or other valuable or reusable elements (as rare-earth metals). Our aim is to determine the accumulation rate of these elements in the plant-tissues and establish the phytoremediaton potential of the plants. Laboratory experiment was conducted in seedling growth tests with various mixtures of red mud, converter sludge and different soil-type-peat mixtures. White mustard (Sinapis alba) and wheat (Triticum aestivum) seeds were applied for the experiments. According to these tests we determined that among the mixtures the most capable ones were the red mud mixed with slightly saline or slightly acidic brown forest soils. In case of the converter sludge, mixtures with chernozem and loess soil showed the best results for germination. The presence of the used sludge-types could stimulate the germination of seeds and the growth of plumules of plants, however the results are highly depends on the type of the soils. The results highlight the importance of seedling tests in determining the phytoextraction possibility when using industrial waste materials, such as the tested sludge-types.

Innovative application for bauxite residue: Red mud-based inorganic polymer spheres as pH regulators

In this study, and for the first time, red mud (RM)-based geopolymer spheres were synthesised, with varying porosity and RM content, and then their use as pH regulators was evaluated. The aluminosilicate sources of these inorganic polymers were 100% waste-based, consisting of a mixture of RM and fly ash wastes. Geopolymer spheres containing up to 60 wt.% RM were successfully produced, while higher RM contents distorted the specimens’ spherical shape. Results showed that alkalis leaching from the spheres over time can be controlled by their porosity, while the RM content induces only minor changes to leaching. The RM-based spheres leached up to 0.0237 mol/dm3g of OH− ions from their structure, this being among the highest values ever reported for geopolymers. This allowed a continuous and prolonged pH buffer capacity with narrow pH decay over the 28 days (2.4 pH units), suggesting the use of the RM-based spheres as pH buffering materials in wastewater treatment and anaerobic digestion systems.