Utilization Of Red Mud Research Articles

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

Red mud, owing to its high alkalinity and presence of hazardous elements, cannot be disposed of in landfills. Sustainable use of red mud is the way to resolve the environmental concerns created by its improper disposal. This study attempts to review the overall applications of red mud as a construction material. Red mud is used in making various construction materials like mortar, bricks, concrete, ceramics, etc. The utilization of red mud in brick manufacturing is said to increase the mechanical characteristics and longevity of bricks. Red mud is also employed in various types of concrete like Lightweight concrete, Ultra high-performance concrete, pervious concrete, and geopolymer concrete. Red mud is employed as a supplementary cementitious material to replace cement because of its chemical composition. Red mud is best suited for enhancing the properties of geopolymer concrete because of its high alkalinity. Existing literature indicates that red mud can be utilized in the construction of bounded base course of pavements with acceptable unconfined compressive strength (UCS), resistance to freezing, thawing, and durability. The presence of red mud in asphaltic concrete was found to increase the stiffness parameters of the asphalt mixtures. In terms of bituminous mixes substituting limestone powder filler with red mud improved mechanical properties, bulk density, and resistance to rutting. Nevertheless, the inclusion of red mud reduced the moisture vulnerability and raveling resistance of bituminous mixtures.

Study on the effect and mechanism of cement-based material retarder on red mud-based hybrid alkali activated cement

In this paper, the effects of sodium gluconate (SG), sodium hexametaphosphate (SHMP) and sodium tripolyphosphate (STPP) on the rheological behavior and mechanical property of red mud-based hybrid alkali activated cement (RM-HAAC) were discussed, and their hydration process were analyzed. Hybrid alkali activated cement has great potential in solid waste utilization and carbon reduction. This study aims to provide valuable reference and guidance for the engineering application of red mud-based hybrid alkali activated cement, and shed light on the utilization of red mud. The results showed that: sodium gluconate could effectively delay the hydration rate of red mud-based hybrid alkali activated cement, which the initial setting time was delayed by 109.8% when the dosage was 0.5 wt%. Sodium hexametaphosphate can promote the hydration rate, which the initial setting time decreases by 25.5% when the dosage is 0.5 wt%. When the content of sodium tripolyphosphate is lower than 0.3 wt%, it has little effect on the hydration rate, while when the content is larger than 0.3 wt%, it has a certain promoting effect. The rheological property of red mud-based hybrid alkali activated cement could be represented by the H–B fluid model. Sodium gluconate increases the fluidity of the slurry, while sodium hexametaphosphate and sodium tripolyphosphate decrease the fluidity. The 28-day compressive strength of red mud-based hybrid alkali activated cement has been improved under the influence of retarder. Sodium tripolyphosphate has the largest 28-day strength with an increment of 18.8%. Microscopic analysis shows that sodium gluconate hinders the hydration process of red mud-based hybrid alkali activated cement mainly through complexation encapsulation and adsorption, and sodium hexametaphosphate and sodium tripolyphosphate promote the hydration process mainly through hydrogen bond bonding between phosphate and alkali activated cementitious materials.

Extraction of Iron and Alumina from Red Mud with a Non-Harmful Magnetization Sintering Process

Red mud, which could cause numerous problems to the environment, is a hazardous waste generated from the alumina smelting industry. In general, the storage and harmless utilization of red mud are hard to implement due to its fine particle size and high alkalinity. This study put forward a novel process to separate iron (MgFe2O4) and alumina (Al2O3) in red mud by a magnetization sintering method. The magnesium oxide was added to transform the nonmagnetic Fe2O3 into magnetic MgFe2O4 to achieve physical separation of iron-bearing minerals, and the alumina-bearing minerals were converted into dissoluble NaAlO2 minerals in a one-step reaction. The atmospheric pressure leaching process was adopted in this study for alumina resource recovery. To achieve clean alumina production, the silicate in the leaching solution was removed by adding the slightly soluble CaSO4, and the entire process becomes clean and harmless. The feasibility of the process was verified by thermodynamic analysis, and a series of experiments were performed to detect the optimum MgO/(Fe2O3 + MgO) ratio and the calcining and leaching conditions. The morphological and mineralogical characteristics of modified red mud, leaching red mud, and magnetic separation product were studied by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS). It was observed that under the optimal conditions with MgO/(Fe2O3 + MgO) of 14.89% to recover iron and aluminum, the corresponding recovery rates were 67.54% and 73.01% respectively, and the iron grade was 30.46%. The EDS results showed that the obtained Mg/Fe ratio of the magnetic separation product was 0.4677–0.528, which is slightly different from that of the standard MgFe2O4 at 0.5. This new method can promote the development of comprehensive utilization of red mud and iron production.

Red mud-slag blends as a sustainable road construction material

Red mud is a highly alkaline solid waste that contains significant amounts of heavy metal ions. This causes serious environmental issues if disposed of unscientifically. Thus, developing an economical and eco-friendly technique for utilization of red mud can solve the disposal problem efficiently. The present study deals with the evaluation of physical, mechanical and chemical properties of red mud treated with ground granulated blast furnace slag to assess its suitability as a construction material for highways. To accelerate the geopolymerization process, additional doses of alkali activator is used. Mineralogical and microstructural analyses have been made to identify the geopolymerization products. An optimization technique is adopted to find out the optimum slag and alkali dose to have the highest strength. The durability of stabilized red mud has been assessed under slaking fluid. Leachate analysis has been carried out on source materials and stabilized materials to examine the levels of major and trace elements. It is observed that the alkali present in red mud can initiate geopolymerization reaction upon the addition of slag. However, additional alkali is needed to accelerate the geopolymerization reaction. Stabilized red mud performed good strength and stability. The alkalinity is reduced after stabilization and the heavy metals are encapsulated by geopolymeric reaction products. Target strengths for different constructions can be achieved with appropriate combinations of slag and alkali.

Extraction of a perovskite from red mud and its photocatalytic reduction of CO2

The extensive utilization of red mud is an urgent problem for the worldwide alumina plants, and the extraction of titanium from the red mud is especially difficult. The extraction of perovskite from a red mud alkaline leaching slag (by using acid leaching), in addition to its photocatalytic reduction of CO2, have been investigated in the present study. The results showed that the photocatalytic CO2 reduction performance of the extracted perovskite was like that of pure synthesized perovskite After a reaction duration of 4 h, the yields of CO and CH4 reached 10.24 μmol·g−1, 2.85 μmol·g−1, respectively, which were 0.96 times and 0.99 times that of pure perovskite, respectively. This study provides a promising method to use the titanium, as recovered from red mud, and presents a novel idea for using hazardous waste for the photocatalytic reduction of CO2, which is beneficial for the sustainable development of the alumina industry.

Effects of Different Silicon Sources on the Properties of Geopolymer Planting Concrete Mixed with Red Mud

In order to reduce the carbon emission of planting concrete in the process of preparation, and to realize the application of large amounts of red mud in the geopolymer, in this study, high silicon source materials and blast furnace slag are added to a large content of red mud base geopolymer planting concrete, which can remove the dependence of planting concrete on ordinary Portland cement and provide a new direction for the comprehensive utilization of red mud. In the paper, the effects of different A (Alkali solid content)/P (Powder dosage) and high silica sources (silica fume and diatomite) on the microstructure and fluidity of the geopolymer, as well as the compressive strength, pore characteristics, and alkalinity of the planting concrete, are comparatively evaluated. The corresponding results showed that when A/P was 0.25, the planting performance of the planting concrete would be reduced due to its high alkalinity; when A/P was 0.15, the planting concrete would have its sedimentation and the compressive strength decreased. On the other hand, the pozzolanic reaction among the silica fume, diatomite, and Ca(OH)2 significantly weakened the alkali pan phenomenon in the later stage of planting concrete formation. The addition of an appropriate amount of silica fume and diatomite also made the structure of the geopolymer more compact with better fluidity, which yielded superior pore characteristics and planting performance for the planting concrete. For good planting concrete pore characteristics, the test results showed that the fluidity of the mortar should be 112–128 mm. Overall, the best planting concrete performance was achieved at an A/P ratio of 0.2, with the contents of silica fume and diatomite being 10% and 5%, respectively. Furthermore, the slope finite element analysis showed that planting concrete made with red mud geopolymer had better slope protection potential than ordinary Portland cement.

Recycling of red mud and flue gas residues in geopolymer aggregates (GPA) for sustainable concrete

This study proposed simultaneous utilization of red mud (RM) and flue gas residues (FGR) as a partial replacement of traditional precursors and energy-intensive activators. Reaction mechanisms of geopolymer pastes were investigated through isothermal calorimetry, X-ray diffraction, thermogravimetry and infrared spectroscopy, by varying the dosage of RM (40%) and FGR (24%, 32%). Results showed that use of RM and FGR as a replacement of FA and commercial activator had a limited influence on the compressive strength. RM and FGR participated in reaction at a slower rate. After optimization, heat-cured FGR0.32 mix was selected to manufacture geopolymer aggregates (GPA). Engineering properties, cost analysis and environmental impact of GPA were evaluated. Natural aggregates (NA) were replaced by GPA at replacement levels of 25%, 50%, 75% and 100% by volume to prepare concrete. GPA concrete with 25% and 100% replacement level could achieve the 94.6% and 86.6% of NA concrete strength respectively at 28 days age.

Enhanced degradation of sulfamethoxazole by activation of peroxodisulfate with red mud modified biochar: Synergistic effect between adsorption and nonradical activation

Since the discovery of the potential environmental risk associated with large quantities of red mud, there has been an urgent need to find a rational disposal technology for this waste. In this study, low-cost iron-based biochar catalysts (RM@BC-x) were synthesized by co-pyrolysis of waste red mud and spent coffee grounds after ball milling. RM@BC-800 exhibited remarkable adsorption capacity, reaching 4.70 mg/g in 120 min. The adsorbed SMX was degraded simultaneously after adding peroxodisulfate (PDS), and sulfamethoxazole (SMX) was completely removed from the solution in only 30 min. Correlation analysis and pre-sorption experiment proved that the adsorption of SMX significantly enhanced the oxidation effect. Moreover, the Fe0, defects and CO groups of RM@BC-800 were the main active sites. Singlet oxygen (1O2) played a dominant role in the degradation of SMX rather than the traditional radicals (•OH or SO4•−). In particular, O2•− was shown to be used mainly as a precursor for the production of 1O2 without directly oxidizing SMX. The steady state concentration of 1O2 has been calculated to be hundreds or thousands of times higher than that of other radicals. Five degradation pathways of SMX were proposed (including NS bond cleavage, hydroxylation, and –NH2 oxidation). RM@BC-800 has the advantages of strong anti-interference ability, low iron leaching based on energy calculations and environmental impact assessments. This work provides a new option for the resource utilization of red mud and designs a green material with fast adsorption and efficient catalysis for the practical treatment of antibiotic wastewater.

Innovative Applications of Red Mud: Converting an Environmental Challenge to a Drilling Asset.

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.

Alkaliphiles for comprehensive utilization of red mud (bauxite residue)—an alkaline waste from the alumina refinery

The mining industry has powered the human endeavor to make life more innovative, flexible, and comfortable. However, it has also led to concerns due to the increasing amount of mining and associated industrial waste. Special attention is highly desired for its proper management and safe disposal in the environment. The problem has only augmented with the increase in the mining costs because of the investments needed for ecological remediation after the mining operation. It is pertinent that the targeted technologies need to be developed to utilize mining and associated industrial waste as a secondary resource to ensure sustainable mining operations. Every perceived waste is a valuable resource that is needed to be utilized to create additional value. In this review, the case of alkaline bauxite residue (red mud)-alumina refinery waste has been discussed at length. The highlight of the proposed work is to understand the importance of alkaliphile-assisted biomining-a sustainable alternative to conventional metal recovery processes. Along with the recovery of metals, pH reduction of red mud is possible through biomining, which ultimately paves the way for its complete utilization. The unique adaptation strategies of alkaliphiles make them more suitable for biomining of red mud through bioleaching, biosorption, and bioaccumulation, which have been discussed here. Furthermore, we have focused on the potential of the indigenous microflora of red mud for metal recovery in addition to its neutralization. The study of indigenous alkaliphiles from red mud, including its isolation and propagation, is crucial for the industrial-scale application of alkaliphile-based technology and has been emphasized.

Resource Utilization of Red Mud from the Solid Waste of Aluminum Industry Used in Geothermal Wells

It is difficult for the commonly used Class G oil well cement to withstand the high-temperature environment of geothermal wells, and it is easy to deteriorate the mechanical properties and damage the integrity of the cement sheath. Industrial solid waste red mud can be used as supplementary cementing materials (SCMs) to improve its mechanical properties at high temperatures. In addition, compared to Class G oil well cement, high belite cement (HBC) has lower energy consumption and better mechanical properties at high temperatures. In this study, the mechanical properties of HBC as a gel material and quartz sand and red mud as SCMs were studied at high temperatures. The ratio of HBC to SCMs and the ratio of quartz sand to red mud in SCMs were optimized using the response surface method (RSM). The response surface was established using the three-level factorial design model, which fit well with the experimental data. The optimization results show that the best mass ratio of SCMs/HBC is 37.5% and that the best quality ratio of quartz sand/red mud is 9 under the curing conditions of 180 °C. However, the best mass ratio of SCMs/HBC is 49.3%, and the best quality ratio of quartz sand/red mud is 7 under 220 °C. With the addition of SCMs, the silicon-to-calcium ratio of HBC hydration products decreases, and high-temperature-stable xonotlite and tobermorite can be formed. After adding SCMs, the cement sample is denser without obvious cracks.

Recovery of nitrogen and phosphorus in wastewater by red mud-modified biochar and its potential application

A large amount of wastewater containing nitrogen, phosphorus, and fluorine produces in the production of phosphate fertilizer. In this study, to simultaneously recover nitrogen and phosphorus from phosphorus-containing wastewater and realize the resource utilization of red mud and rape straw, red mud-modified rape straw biochar (RM/RSBC) was prepared by facile one step, and the physicochemical properties were characterized by Zeta potential, SEM-EDS, BET specific surface area (SSA), FTIR, XRD, and XPS. The adsorption performance and mechanisms of ammonium and phosphate onto RM/RSBC were explored through static, fixed-bed column adsorption, and practical wastewater experiments. The results showed that pH = 3.0 and 8.0 were favorable for the removal of phosphate and ammonium, respectively. The main adsorption mechanisms of ammonium and phosphate were the interaction between ammonium and surface functional groups and surface precipitation, respectively. The removal efficiencies of ammonium and phosphate by fixed-bed column adsorption mainly depended on the addition amount of RM/RSBC, the concentration of ammonium and phosphate, and the flow rate. The results of the germination experiment showed that adding > 0.5 wt% of RM/RSBC loaded with ammonium and phosphate promoted the growth of mung beans. This study shows that RM/RSBC can not only recover ammonium and phosphate in wastewater, but also realize the resource utilization of red mud and rape straw.

Summary of research progress on separation and extraction of valuable metals from Bayer red mud.

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

Turning hazardous red mud into useful catalysts for the carbonylation of amines to N-formamides

With the rapid development of the aluminium industry, the output of waste by-products (red mud) increases over time. Although continuous efforts have been devoted to dealing with this hazardous waste, the universal utilization of red mud accounts for only 15% of the total. Therefore, development of green and sustainable technologies with which to dispose of red mud is regarded worldwide as an urgent requirement. Herein, a facile utilization of the bases in hazardous red mud to catalyze the carbonylation of amines to N-formamides is reported. This catalytic system can achieve 99% conversion of amines with 100% selectivity for N-formamides. Gram-scale preparation of useful formamides, such as N,N-dimethylformamide (DMF) and N-formylmorpholine was also successfully accomplished. Further investigation revealed that a free alkaline ingredient in red mud is the active center for this transformation. This work provides an economical and environmentally benign solution to the use of the waste red mud, and also greatly promotes the potential application to catalysis of materials derived from red mud.

Experimental Investigation on Red Mud from the Bayer Process for Cemented Paste Backfill.

Red mud is a by-product of alumina production, and its disposal can have severe environmental consequences. This study experimentally investigates the feasibility of using red mud from the Bayer process for cemented paste backfill (CPB). Different binders and activators were used to improve the mechanical properties, water resistance, and environmental behaviors of red mud-based CPB. In addition, water immersion tests were introduced, for the first time, to evaluate the water resistance of CPB. Furthermore, the environmental behaviors of red mud-based CPB were investigated by conducting leaching experiments. The results showed that the red-mud specimens had an unconfined compressive strength (UCS) of less than 0.2 MPa and disintegrated after being immersed in water. Different binders significantly improved the mechanical properties of red mud-based CPB. In addition, the specimens with different binders showed excellent water resistance, and the softening coefficient of CPB with different binders could exceed 0.7 after being cured for 28 days. The binders exhibited a substantial inhibitory effect on the leaching of hazardous substances in red mud under the solidification and stabilization effects. The leaching concentration of hexavalent chromium, selenium, fluoride, arsenic, lead, and vanadium was reduced by more than 70%. Therefore, this study provides an effective method for the environmental-friendly and large-scale utilization of red mud from the Bayer process.

A novel process for one-step preparing potassium-containing fertilizer using red mud or CFA synergistic extraction of alumina

Red mud and coal fly ash (CFA) are bulk aluminum-containing solid waste in the industrial production process, posing a great threat to the environment and ecological security. The present paper proposes a novel method for one-step producing potassium-containing fertilizer synergistically extracting Al2O3 by KOH hydrothermally treating red mud or CFA. In this paper, the dissolving ratio of Al2O3 in the K2O-Al2O3-H2O ternary system and the extraction of Al2O3 from red mud or CFA after hydrothermal treatment with KOH were investigated. The phase structure transformation of leaching residue obtained under various conditions was analyzed by X-ray diffraction and scanning electron microscopy, and the fertilization efficiency of the products was verified by potting experiments. The results show that the dissolving ratio of Al2O3 can reach the highest value of 85.04% at 120 °C with the K2O mass fraction of 24.90% in the ternary system. When red mud or CFA was hydrothermally leached with 240 g/L K2O at 240 ℃, the Al2O3 extraction rates of 25.50% and 31.42% could be separately obtained, and the leachate could be reused. The main phases of the leaching residue were kaliophilite, illite, and megakalsilite, and the content of K2O was 7.83% and 26.89%, which can be applied as potassium-containing fertilizer to improve soil fertility and effectively promote the growth of pakchoi. The process improves the comprehensive utilization of red mud and CFA without secondary pollution, reduces the negative impact on the environment, and opens up a new way to apply bulk solid waste in the agricultural field.

A novel humidity self-regulating interior wall coating composite based on red mud derived from alumina production

Aimed to resolve the problem of excessively high indoor humidity in subtropical areas and develop a new resource disposal technique for red mud, a novel humidity self-regulating interior wall coating composite based on red mud (HRCRM) was successfully prepared using red mud as a matrix material and vermiculite as a humidity regulator. The effects of component proportion, ambient humidity, exposure time on hygroscopicity of this composite were systematically investigated. This composite exhibited good humidity regulating ability with the largest water absorption rate of 16.38% under experimental conditions. Moreover, various properties were tested including surface drying time, hardness, adhesion, coating appearance, water resistance and reusability, meeting the national standard requirements well. The mechanism was comprehensively analyzed by XRD, TG-DTG, FESEM, and FTIR, indicating that the humidity self-adjusting function of HRCRM was realized by regulating the interlayer water storage of vermiculite. This study can provide theoretical and technical guidance for residential environment improvement in subtropical areas and comprehensive utilization of red mud.

Effects of NaOH Content on the Reduction Kinetics of Hematite by Using Suspension Magnetization Roasting Technology

Red mud is a potential iron resource that needs to be urgently exploited and utilized. However, due to the properties of high alkalinity, fine particle size and complex mineral composition, the utilization of red mud is difficult. Focusing on red mud’s prominent feature of high alkalinity, this paper studies the influence of NaOH content on the reduction kinetics of hematite, which is the main component of red mud. The results show that the conversion degree of hematite was strongly inhibited by NaOH, and the magnetization and specific magnetic susceptibility of reduction products was significantly decreased with the increase in NaOH content. Meanwhile, the results of the calculation of kinetics parameters demonstrate that the addition of NaOH did not affect the control step of the reduction of hematite, while it dramatically decreased the reduction rate of hematite. Moreover, thermodynamic analysis and SEM-EDS detection were conducted to uncover the inhibited mechanism of NaOH on the reduction of hematite, which indicated that sodium ferrite could be produced spontaneously under the experimental conditions and that it is hard for it to be further reduced by CO. Furthermore, the produced sodium ferrite formed a dense film, which covered the surface of the hematite particles, inhibiting the diffusion of CO and thereby hindering the reduction of the interior hematite.

Reclamation of Red Mud for the TiO2 Production by Ilmenite Smelting at Lower Temperature

ABSTRACT Red mud produced from the Bayer process was used for the high temperature metallurgical processing of ilmenite. The major components of the red mud were Fe2O3, Al2O3, Na2O, and TiO2, which play important roles in the flux material. The process temperature of ilmenite slag was lowered from 1794 K (1521°C) to 1687 K (1414°C), as a preliminary study by a high-temperature microscope. Thermochemical calculations using FactSageTM 7.0 confirmed the effect of red mud on the lowered melting temperature of ilmenite slag. The discrepancy between the observed results of the microscope and the calculated phase diagram was due to the slag viscosity, which was significantly affected by Al2O3 in red mud. The reduction of ilmenite at lower temperatures by the addition of red mud was investigated at 1723 K (1450°C). Ilmenite, pseudobrookite, and associated clay minerals were the major phases in the reduced ilmenites which was confirmed by X-ray diffraction (×RD) analysis. Microscopic images obtained by scanning electron microscopy (SEM) showed variations in the pseudobrookite phases according to the amount of fluxed red mud. The benefits of red mud utilization are discussed with regard to the lower energy consumption and recovery of resources.

A New Strategy for Collaborative Utilization of Red Mud and Coal Fly Ash via Vacuum Reduction Technology

A New Strategy for Collaborative Utilization of Red Mud and Coal Fly Ash via Vacuum Reduction Technology