Utilization Of Red Mud Research Articles

Feasibility of preparing red mud-based cementitious materials: Synergistic utilization of industrial solid waste, waste heat, and tail gas

In order to address the environmental problems caused by red mud and other industrial by-products, a new concept was proposed to use red mud to prepare cementitious materials by incorporating other solid wastes, waste heat, and tail gas. The feasibility of this synergistic concept was verified by laboratory-scale tests, and the effect of tail gas and waste heat on solid wastes was revealed by FTIR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), and SEM-EDS (Scanning electron microscopy-Energy Dispersive Spectroscopy), and the key device for carbonation disposal was developed. The results showed that the cementitious reactivity of industrial solid wastes can be improved by carbonation disposal of tail gas. The cementitious reactivity of Sintered red mud, coal gangue, fly ash, and Bayer red mud was increased by 49.8%, 4.4%, 9.5% and 18.9%, respectively. The multi-solid waste system with Bayer red mud, steel slag, carbide slag, aluminum ash, and flue gas desulfurization gypsum can generate high performance red mud-based cementitious materials (RCM) with a compressive strength of 8.8 MPa at 1 d under the circumstance of high temperature disposal. And RCM consists of 2CaO·SiO2, 3CaO·Al2O3, and CaO·(Al2O3 + Fe2O3). In addition, the mechanical strength and soundness of RCM can be improved by the carbonation of tail gas. This innovative concept provides a way for the mass utilization of red mud along with other solid wastes, waste heat and tail gas through the relevant cementitious materials for use in transportation construction, and shed light on the cleaner production of industry.

Characterization of red mud and its effects on environment due to its traditional methods of disposal

Red mud is a by product produced in the process of extraction of alumina from bauxite. The process is called Bayers Process. It is an insoluble product and is generated after bauxite digestion with sodium hydroxide at elevated temperature and pressure is known as red mud. Large quantity of red mud is generated worldwide every year posing a very serious and alarming environmental problem.This paper describes the production and characterization of red mud in view of World and Indian context. It reviews comprehensively the disposal and neutralization methods of red mud and gives the detailed assessment of the work carried until now for the utilization of red mud, pollution control, metal recovery, coagulant, adsorbent, catalyst and in soil remediation. It also reviews the work carried out for rehabilitation of red mud ponds. This paper is an effort to analyze pollution and ecological considerations in the context of environmental concerns for disposal and utilization of red mud.

Evaluation of microwave acid baking on Indian red mud sample

The present study validates the application of microwave heating for acid baking of red mud and the dissolution of metallic values during water leaching. The effect of microwave power and exposure time is evaluated on the sulfation and decomposition mechanism of the constituent phases present in the red mud. It is inferred that the processing time can be significantly reduced to less than 3 min for the enrichment of Fe (~41%) and Ti (~15%) in the residue by employing microwaves as a heating source. The low solution pH value (<2) for baking experiments with less than 90 s synergized to improve metal dissolution during the leaching stage. The metallic values in the solution were precipitated and calcined to produce a product containing refractory phases such as mullite, alumina, and hematite, which can be segregated using a conventional magnetic separation process. The dissolved titanium values interact with iron values and occur in ilmenite and pseudobrookite phases in the calcined precipitate. The microwave-assisted acid baking process is a potential first step process for the complete utilization of red mud and separation of iron and titanium values.

Preparation sequences and pretreatment optimization of alkali-activated red mud and blast furnace slag-based materials

The preparation of alkali-activated materials from red mud for building materials is a promising way to solve the environmental pollution caused by red mud. However, the low compressive strength of alkali-activated red mud-based materials is the biggest obstacle to this solution. In this paper, we illustrate that the compressive strength of alkali-activated red mud and blast furnace slag-based materials is strongly influenced by the modulus of sodium silicate, preparation sequence, and calcination pretreatment. Thus, the best sodium silicate modulus (1.0) and optimized preparation sequence that involved using a cooled sodium hydroxide solution mixed with the red mud-blast furnace slag mixture before exposure to the sodium Csilicate were adopted. Then the calcination pretreatment of the red mud, gypsum, and lime was adopted to improve the compressive strength, and the optimal calcination temperature was selected to be 700 °C. The increase in the compressive strength (up to 71.82 MPa) resulted from a large number of active particles, which were generated by the fracture of numerous Si–O bonds and Al–O bonds after the calcination pretreatment. The results support the extensive utilization of red mud in building materials to prevent environmental pollution.

Staged leaching behavior of red mud during dealkalization with mild acid

Dealkalization is a major limiting factor for the comprehensive utilization of red mud, and acid leaching is considered an effective and promising way to achieve it. Most studies have focused on the recovery of metals in this extreme alkaline waste by strong acid leaching, ignoring the dealkalization and stabilization of red mud with low concentrations of acid. In this study, the leaching behavior of the major elements in red mud was carefully investigated by the treatment with a range of H+ concentrations from 10−6 to 1.8 mol/L. Analysis of both leachate and residue confirmed a stepwise sequential leaching behavior of Na, Al, and Ca, which was important for dealkalization of red mud. Treatment with an acidic solution at pH 1 removed 17.84% of Na, but almost no other metals. Greater than 60% Na was leached by an acidic solution with H+ concentration of 0.5 mol/L, but the dissolution efficiencies of Al, Si, and Ca were less than 10%, resulting in a relatively simple leaching liquid treatment process. And the pH of the leaching residue was 8.5 which slightly alkaline so the residual RM could be used as soil aggregates. When using an acidic solution with an H+ concentration of 1.6 mol/L, the dissolution efficiency of Na reached at 94.70%, leaving only 0.47% Na in the residue, which makes it possible to meet the demand of application for construction materials. From the results of the phase analysis, it was found that the sequential leaching behavior was due to the dissolution, decomposition, and transformation of the particles containing the main elements, and was compatible with the SEM-EDS inspection. Based on these results, a new multi-stage acid leaching dealkalization process has been proposed to provide an effective and economical way to dealkalize red mud.

Influence of Fly Ash on Geotechnical Behaviour of Red Mud: A Micro-mechanistic Study

The disposal of highly alkaline and hazardous bauxite residue mud generated from the Bayer process in the alumina industry leads to the serious environmental impact on natural resources. Effective and bulk utilization of red mud needs to be done to minimize an adverse impact on environment. The present study contracts to explore the possible utilization of red mud as a geomaterial by modifying its properties with fly ash (Class ‘F’). Detailed geotechnical properties (plasticity characteristics, compaction characteristics, swell index and Unconfined compressive strength (UCS)), physicochemical properties (pH and electrical conductivity) and micro-analyses (XRD, SEM, EDAX and FTIR) have been performed in the red mud amended with varying fly ash content up to 80%. The characterization of red mud demonstrates the higher value of specific gravity, liquid limit, optimum water content (OWC), maximum dry density (ρdmax), pH value, and electrical conductivity than that of the same of fly ash. Further, the amendment with various fly ash content has observed a significant effect on the plasticity and compaction characteristics of the red mud. The results show a significant reduction in liquid limit, plastic limit, OWC and ρdmax of red mud with an increase in fly ash content. Ultimate increase in the UCS of red mud is observed at its substitution with 15% fly ash which can be considered as an Optimum Fly Ash Content (OFC) from strength point of view. Further, experimental results are elucidated through physicochemical and microanalyses.

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.

Utilization of red mud for producing a high strength binder by composition optimization and nano strengthening

AbstractRecycling of red mud (RM) has attracted more attention in recent years due to severe environmental problems caused by landfilling. The effect of composition optimization and Nano-strengthening on the properties of a binder based on RM was studied in this paper. Results showed that modifying ratios of main oxides and adding Nano-SiO2could obviously affect the mechanical properties and microstructure of the binder. Specimens with high SiO2/Al2O3molar ratio (S/A) displayed considerable increase in compressive strength, while decreasing Na2O/Al2O3molar ratio (N/A) improved the workability of the fresh mix. The compressive strength was developed significantly to be 45 MPa at 28 days by adding Nano-SiO2with 0.4 wt.% of RM. Phase transformation and microstructure change at different stages of RM decomposition and binder geopolyerization were investigated by X-ray diffraction (XRD), Fourier transformation infrared (FTIR) and Scanning electron microscopy (SEM). The results of this study may provide a prospective method to use RM more widely in construction applications.

A Way Forward in Waste Management of Red Mud/Bauxite Residue in Building and Construction Industry

In the Bayer’s process of extracting alumina from bauxite using caustic soda, the waste generated is called as red mud/bauxite residue. About 1–2.5 tonne of bauxite residue is generated per tonne of alumina produced depending upon the bauxite and process conditions used. It is generally stockpiled into the red mud ponds situated near the industrial area and is highly alkaline which is a matter of environmental concern. Hence it becomes necessary to look upon its waste management and utilization for various applications. This paper is an endeavour to focus upon the efforts taken by the researchers worldwide to make use of red mud in building and construction industry. It projects Indian and world bauxite and alumina scenario. Chemical composition of red mud generated in different countries has been presented. Work carried out on the sub-applications of building and construction such as bricks, ceramics, cement, geopolymers, clay materials, slag treatment, road construction, and fillers has been described. Pilot plant/commercialization in this application area till date has been mentioned. Issues which are restricting use of red mud in building and construction have been discussed. Some guidelines for the appropriate management and utilization of red mud have been stated.

Study on stress-strain-resistivity and microscopic mechanism of red mud waste modified by desulphurization gypsum-fly ash under drying-wetting cycles

In order to investigate characteristics of red mud waste modified by desulfurization gypsum-fly ash, an unconfined compressive strength test and a synchronous resistivity test of solidified soil under different contents, curing time and dry-wet cycles were carried out. Moreover, the internal structure change, reaction mechanism, and the hydration characteristics of desulfurization gypsum-fly ash soil were analyzed by XRD and SEM tests. The results show that under the 77% red mud content, the unconfined compressive strength increases with the increase of age. The stress-strain-resistivity curves of the same amount in red mud at different ages are basically consistent with each other. Under different contents, in the first three-stage, stress increases with strain, and the resistivity decreases with increasing strain. In the local deformation stage, the stress decreases rapidly with the increase of strain, and the resistivity keeps decreasing until the specimen is completely destroyed. When the water content is lower, the resistivity is greater. Also, with the increase of number drying-wetting cycles, the strength of the sample mixture is gradually weakened from 1.34 MPa of one drying-wetting cycle to 0.8 MPa of nine drying-wetting cycle. The corresponding resistivity with one drying-wetting cycle continues decreasing slowly about 0.5%, and this trend of decreasing is gradually weakened. When the drying-wetting cycle is more than 5, the resistivity will increase with the increasing of the drying-wetting cycles. The microstructures of red mud waste modified by desulfurization gypsum-fly ash soil were examined by SEM analysis after a different number of dry-wet cycles. The SEM analysis has shown that the sample mixture was initially compacted with homogenous particles, because of the amorphous gel C-S-H and kotoite silicatian which are basically responsible for strength development. With the increases in drying-wetting cycle numbers, there are obvious changes in the characteristics and the structure of the mixture sample, whereas the porosity of the structure of the sample also increases, while the density and the unconfined compressive strength of the structure of the sample decreases. This paper aims to provide an important theoretical application of the comprehensive utilization of red mud as a road base material.

Analysis of technical and economic indicators of the pyrometallurgical scheme co-processing of red mud and scale

Elaboration and implementation of effective technologies of utilization of alumina production wastes (red mud) is a rather actual task. Various variants of red mud and oiled rolling scale agglomeration considered aimed at their utilization at sinter and blast furnace plants to obtain conditional marketable cast iron. As the object of the study, red mud of OJSC RUSAL and oiled rolling scale of Sinarsky pipe manufacturing plant were used. It was shown, that their joint processing enables to obtain an agglomerated product having iron content more than 50%, which meets the modern requirements to the burden materials for blast furnaces. To determine the optimal scheme of the processing in the blast furnaces, various variants of studied materials agglomeration were calculated – an oxidizing roasting to obtain pellets and briquetting with application of burnt lime as a binder. The components interrelation in the mixture was selected to have iron content in the agglomerated product high enough at maximal possible volume of red mud utilization. The calculation analysis showed that interrelation 50% of red mud and 50% of oiled rolling scale meet the requirement. Calculated blast furnace heat indicators presented while applying briquettes and pellets from red mud and oiled rolling scale in the burden.

Effect of Freezing‐Thawing Cycle on the Mechanical Properties and Micromechanism of Red Mud‐Calcium‐Based Composite Cemented Soil

The environmental issues caused by solid waste have become increasingly serious. Adding additive is considered as an effective measure to improve the performance of the cemented soil. Therefore, the feasibility study of solid waste such as red mud and desulfurization gypsum used in composite cemented soil is in urgent demand. In this study, the mechanical properties and durability to freezing‐thawing cycle of red mud‐calcium‐based composite cemented soil (RMCC) were analyzed through compressive strength test, resistivity test, and freezing‐thawing cycle test. The action mechanism of RMCC was revealed through a series of X‐ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) test. The results show that the optimal red mud content in RMCC is 12%. As the freezing‐thawing cycle progresses, the difference in resistivity and pressure sensitivity of RMCC gradually weakens. When the freezing‐thawing cycle reaches 7, the pressure sensitivity characteristic of RMCC is lost. The change in resistivity and pressure sensitivity can be used to characterize the damage caused by the freezing‐thawing cycle. Combined with XRD and SEM analysis, the presence of minerals such as K2Ca5(SO4)6·H2O and (Ca, Na)2(Si, Al)5O10·3H2O play a key role in fixation of alkali metal elements, and the coordination of CSH gel cementation effect and AFt filling effect has a significant impact on mechanical properties. The study provides an effective way to the utilization of red mud and desulfurization gypsum in subgrade strengthening.

Utilization of red mud as an alternative mineral filler in asphalt mastics to replace natural limestone powder

With the view of reducing the consumption of non-renewable limestone resources, the waste-derived secondary resource can be considered as the limestone powder replacement for hot asphalt mixtures. This study unravels the feasibility of using a red mud-derived alternative filler aggregate to replace the commonly used limestone powder in asphalt mastics, and further improves the red-mud-modified asphalt mastic by using hydrated lime and white mud. The experimental tests, including direct tension (DT), Positest AT-A bonding strength, as well as dynamic shear rheometer (DSR), were performed to characterize the cracking resistance, the moisture damage, the fatigue behavior, as well as the rheological properties of asphalt mastic. Due to surface morphology and mineralogical composition of red mud, its replacement of limestone powder improved the elastic recovery of asphalt mastic, but it had detrimental effect on properties of the cracking resistance, the moisture damage and the fatigue life. When incorporating the hydrated lime and white mud, both materials can improve the low-temperature cracking resistance of red mud asphalt mastic. Moreover, the incorporation of the white mud into the red mud asphalt mastic can enhance its moisture resistance of aggregate-mastic bonding under both short- and long-term moisture attack as well as its fatigue resistance.

Comparison of mechanical and durability properties of treated and untreated red mud concrete

Red mud is a residue of alumina refinery process, every year throughout world more than 300millions tonnes of red mud is comes out as a waste material. The discharge of this large amount of red mud creates harm to nearby living bodies. For the above reason present work focuses on the optimum utilization of red mud as a constructional raw material. In the present work compared the both treated and untreated red mud behaviour in concrete as a concern of mechanical as well as durability properties. Treated and untreated red mud is partially replaced to the cement of 0%–15% with an interval of 2.5%. Both the red mud chemical composition was evaluated by X-Ray Fluorescence (XRF) analysis. Compressive, flexural and split tensile strength are conducted to compute the mechanical properties. Rapid chloride penetration test and water absorption test conducted to know the concrete durability properties. From the results analysis, the optimum replacement of untreated red mud is 5% and treated red mud is 10% as a concern of mechanical properties. Increases the replacement of red mud in cement, increases the durability of concrete showed by the both treated and untreated red mud. There is no much difference observed between treated and untreated red mud in concrete durability properties.

Application of modified red mud in environmentally-benign applications: A review paper

Red mud (RM) is a waste product that results from bauxite refining via the Bayer process. Its disposal remains an issue which raises significant environmental concerns, particularly if disposed on land or water bodies. Much research has been done on the use of red mud for environmentally-benign applications such as wastewater treatment, catalysis, the production of construction materials and glass ceramics, and for the recovery of metals. This paper reviews the current efforts made in the utilization of red mud as a valuable industrial by-product, which in turn should minimize its harmful impact on the environment. This detailed review compiles and highlights a variety of novel applications of modified red mud as a coagulant, an adsorbent for wastewater treatment, as well as, its use in catalytic processes and in building materials. The physico-chemical properties of red mud can be tuned by a range of treatment methods include acidification, neutralization and heat treatment. As revealed from the literature reviewed, modifications on red mud for the removal of various types of contaminants have shown promising results. However, further amendment and modifications on red mud are needed to utilize this industrial waste in many other industrial applications.

The utilization of red mud waste as industrial honeycomb catalyst for selective catalytic reduction of NO.

As a new way for the high-value utilization of red mud (RM) waste, we proposed an improved approach to prepare the RM-based sludge/powder via the sulfuric acid hydrothermal dissolution and NH3 aqueous precipitation route and then the RM-based industrial-sized honeycomb (150 × 150 × 600 mm) was successfully produced by the extrusion moulding method in pilot scale. The synthesized RM-based powdery/honeycomb catalyst exhibited more than 80% deNOx activity and good durability of H2O and SO2 above 350°C. But the decline of NO conversion was also observed above 350°C, which was confirmed to result from the increased oxygenation of NH3 at high temperature. To improve the NO conversion at high temperature, NH3 was shunted and injected into the catalyst bed at two different places (entrance and centre) to facilitate its uniform distribution, which relieved the oxidation of NH3 and increased deNOx efficiency with 98% NO conversion at 400°C. This work explored the industrial application feasibility for the RM-based honeycomb catalyst as well as the possible solution to decrease the oxygenation of NH3 at high temperature, which presented a valuable reference for the further pilot tests of RM catalyst in industry.

Rheological and mechanical properties of bauxite residue as hot mix asphalt filler

Bauxite residue (red mud) is a highly alkaline solid waste generated in the process of production of aluminium metal from bauxite ore. More than 5.5 million tons of red mud is generated in India. The aluminium industries, worldwide and in India, have expressed strong need for dedicated research to explore large-scale utilization of red mud. Towards this end, the objective of this study is to investigate the use of red mud as a filler in hot mix asphalt (HMA). Stone dust, a traditionally used filler material, is used as the control filler. For a comprehensive evaluation approach, the present investigation is conducted at three levels: filler, mastic and mixture characterisation. Red mud and stone dust fillers are characterised using scanning electron microscopy (SEM), pH, Rigden voids, methylene blue value, particle size analysis, and specific surface measurement. Mastic rheology is studied using the dynamic shear rheometer by temperature sweep and multiple stress creep and recovery (MSCR) tests. Finally, dense-graded bituminous concrete (BC) mixes are designed by the Marshall method followed in India, at different filler contents of both filler types. Mixture performance is investigated in terms of indirect tensile strength and Cantabro abrasion loss. Results show that addition of both fillers improved the viscoelastic response of the base binder. Red mud mixes showed higher resistance to disintegration and higher tensile strength than the control mixes with stone dust filler. Based on the findings of this study, red mud showed good potential for use as a filler in dense graded bituminous mixes.

Experimental research on magnesium phosphate cements modified by red mud

The main concern of this article is to understand the influences of red mud on the properties of magnesium phosphate cement (MPC), which were determined in terms of the fluidity, setting characteristic, temperature evolution during the hardening stage, mechanical properties, water resistance, hydration products, pore structure and microstructure. The results showed that the fluidity can increase to a value of 272.5 mm at a level of 20% red mud, and red mud was found to decrease the exothermic reaction intensity of the fresh mortar and to prolong the setting time to 25 min during the hardening stage. The mortar prepared with suitable addition of red mud presented with improved mechanical properties and enhanced water resistance during the whole ageing period, and the group containing 20% red mud yielded the highest compressive strength of 90.2 MPa at 28 days. Then, the pore structure was measured by low-field nuclear magnetic resonance (LF-NMR), which was found that adding red mud can reduce the total porosity and form more small pores. Moreover, the microstructure and the hydration products of the samples were tested by X-ray diffraction (XRD), scanning electron microscopy (SEM) along with energy dispersive spectrometer (EDS). The obtained results illustrated that red mud can fill in the microcracks, making the structure denser, and also formed with some new hydrates. The present work aimed at the utilization of red mud and the results illustrated that MPC can be modified by red mud significantly.

Disposal Practices and Utilization of Red Mud (Bauxite Residue): A Review in Indian Context and Abroad

The insoluble product generated during bauxite digestion with sodium hydroxide at elevated temperature and pressure is known as ‘bauxite residue’ or ‘red mud.’ Due to its high alkalinity (pH ranges between 11.50 and 13), its storage and disposal become a major issue. It can cause problems such as contamination of groundwater due to alkali seepage, impacting air quality with alkaline dust which has its effect on plant life, and a large area of land required for its disposal. This paper critically reviews the disposal practices and utilization of bauxite residue in India and abroad. It assesses the data of Indian alumina refineries regarding bauxite residue generation and utilization in the year 2017. The application areas of bauxite residue utilization in building and construction and metal recovery by these refineries have been reported. Other areas of red mud utilization can be in vegetation, pollution control and as catalysts. This paper is an effort with the aim to review the contributions of India and other countries of the world to resolving the problems associated with bauxite residue from the twentieth century onward up to the year 2018.

Utilization of red mud, slag and waste drilling fluid for the synthesis of slag-red mud cementitious material

Abstract Waste drilling fluid is a kind of residue generated in the drilling process. The traditional treatment of waste drilling fluid, such as solid-liquid separation, chemical degradation, heat treatment, solidification treatment and biochemical degradation, is expensive and complicated. Red mud, which is an industrial by-product produced during the extraction of bauxite, also has problems such as excessive accumulation and difficult to deal with. In this study, a new cementitious material was prepared by using waste drilling fluid, blast furnace slag and red mud for the purpose of environmentally efficient solutions for wastes recycling. The physical and chemical properties of blast furnace slag-red mud cementitious material (SRCM) are evaluated by compressive strength, X-ray diffraction (XRD) analysis and mercury intrusion porosimetry (MIP). The compressive strength results show that the samples can achieve 16.7 MPa. The hydration mechanism of the SRCM is studied by hydration heat analysis and scanning electron microscopy (SEM). The results show that the structure formation of the material is mainly formed by the new amorphous structure. The structure of the SRCM is denser with respect to blank sample without red mud. Toxicity leaching result shows the heavy metal ion content meet the criteria in standard, indicating the new cementitious material is environmental friendly.