Red Mud Research Articles

Exploring the impact of red mud on the mechanical, durability, and microstructure properties of concrete

Purpose This study investigated the potential of partially replacing cement with red mud (RM) in concrete and examined its effects on its mechanical properties and microstructure. This study aims to explore sustainable alternatives to traditional cement and evaluate the performance of concrete mixtures with varying percentages (%) of RM as cement replacement. Design/methodology/approach This research aims to comprehensively understand the impact of RM on concrete, aiming for both environmental sustainability and improved construction materials. Subsequently, concrete mixtures were prepared with varying RM contents, ranging from 0% to 21% in increments of 3%, replacing cement. The workability of these mixtures was evaluated using the Slump Cone Test, whereas their mechanical properties (compressive strength, flexural strength and split tensile strength) were assessed through standardized tests. The durability was further investigated via water absorption, acid attack, rapid chloride permeability tests, open porosity test and Sorptivity test. To gain deeper insights into the internal structure of concrete, microstructure analysis was conducted using X-ray diffraction and scanning electron microscopy. Finally, the results were analyzed and quantified. Findings The finding demonstrates that substituting 12% of cement with RM not only boosts the mechanical characteristics of concrete but also mitigates waste disposal. The microstructural analysis identified a denser cement matrix and improved bonding between the cement paste and the aggregates, suggesting potential improvements in strength and durability. Originality/value These results suggest that RM can be efficiently used to produce sustainable concrete with potential applications in construction projects with environmental considerations.

Properties of multi-solid waste cementitious materials for highly efficient indoor formaldehyde degradation via response surface method

The environment-friendly cementitious materials with efficient indoor formaldehyde degradation properties (PRCS) were prepared by using slag to supplement the percentage of silica and aluminium in the phosphogypsum (PG)-red mud (RM) system, cement as an activator, and activation through the sulphate component in PG. PG-MnO2, a component of PRCS, was obtained by redox of potassium permanganate with PG as the carrier. The mechanism of formaldehyde degradation on PG-MnO2 was analyzed by catalytic model fitting, the multi-objective optimization of PRCS was achieved using response surface methodology (RSM), and the hydration products and microstructure of PRCS were characterized. The results show that the maximum compressive strength of PRCS can reach 26.02 MPa (7 days) and 35.13 MPa (28 days), respectively. The response surface model can be effectively used to simulate the compressive strength of PRCS since the experimental results of the best fitting ratio are close to the predicted results. PRCS achieves an initial 84 % degradation of formaldehyde through adsorption and surface active sites, and maintains 63 % efficiency after five degradation cycles. Also, there is no risk of heavy metal ion leaching.

Solidification Mechanism of Bayer Red Mud under the Action of Calcium Hydroxide

Because of the strong alkalinity of red mud, it is difficult to recycle, and the long-term accumulation of red mud causes environmental pollution. The study shows that the solidification characteristics of bayer red mud (RM) under the action of Ca(OH)2 (CH) are obvious. The mechanical properties of Bayer RM paste with different amounts of CH at different ages were tested. The strength of RMCH gradually increases with the increase in CH content and age, reaching a turning point in strength at 26.4% content of CH, with the highest strength at 28 days, reaching 2.73 MPa. The solidification products were characterized by XRD, FTIR, TG-DTG, and SEM-EDS. The results show that under the action of CH, the main solidification products of RM are C-(A)-S-H, hemicarboaluminate, and monocarboaluminate. In the solidification process, hydroxysodalite and faujasite-Na react with CH to generate C-S-H, Al(OH)4−, and Na+, then react to generate hemicarboaluminate, monocarboaluminate and C-(A)-S-H, among which hemicarboaluminate is transformed into monocarboaluminate in the presence of calcite, and further monocarboaluminate decomposes to generate calcite. It provides a basis for the study of the interaction mechanism between a single substance and RM and provides a research basis for the sustainable utilization of red mud.

Scanning electron microscopy (SEM)-assisted mechanistic study: pH-driven compressive strength and setting time behavior in geopolymer concrete

This research study investigates the influence of pH on the setting time, compressive strength (CS), and surface roughness of different waste materials, namely fly ash, rice husk ash (RHA), red mud, and ground granulated blast furnace slag (GGBS). The average pH values for these waste materials were found to be 8.77, 9.3, 8.3, and 11, respectively. The initial setting time (IST) and final setting time (FST) varied among the materials, with red mud having maximum IST and FST with a value of 180 min and 24 h. CS (MPa) measurements revealed that GGBS exhibited the highest value of 36 MPa, followed by RHA (28 MPa), red mud (22 MPa), and fly ash (24 MPa). Surface roughness analysis showed that red mud had the highest roughness value of 69.71, followed by fly ash (62.81), RHA (53.14), and GGBS (49.08). The findings indicate a positive correlation between pH levels and CS of 97%, and setting time surface roughness has a negative correlation with CS when analyzed with a heatmap. Higher pH values were associated with increased CS, particularly after 28 days of curing which is shown by the heatmap and sub-plots. Additionally, microscopic analysis provided insights into particle size, orientation, and clustering, aiding in understanding the bonding and reactivity patterns contributing to the observed variations in CS.

Environmental assessment of materials in preparing alkali-activated materials using bauxite residue

Abstract Aluminum is a highly produced metal globally. In the built environments alone, aluminum is known for its light weight and anti-corrosive properties and is a common choice of material in window frames, curtain walls, and light fixtures. The metal is processed from its oxide, alumina, the production of which releases a caustic byproduct known as bauxite residue (BR). BR is stored in massive reservoirs, however, due to the sheer volume of production, industries handling the material are reaching their storage limits. It is of high importance to research methods to valorize BR. Researchers have proposed a multitude of valorization methods, which include metal recovery from the byproduct, and using BR as raw material in production of another material. However, it is counterproductive to expend considerable amounts of energy and use excessive raw materials to manage utilization of BR. This study compared a method of valorization of bauxite residue with clay bricks. The method of preparing alkali-activated materials (AAM) with bauxite residue as a precursor was semi-quantitatively analyzed to compare the raw materials in the AAM with clay bricks. The materials were analyzed for climate change, ozone depletion, human toxicity, and aquatic ecotoxicity using OpenLCA software and the ecoinvent version 3.4 database. While the alkali activators possessed high values of the environmental impact when measured by the kilogram, the impacts were greatly reduced due to their small percentage in weight contained in the AAM. This study is the first stage of analyzing the environmental costs of valorizing bauxite residue. The AAM showed low environmental impact in material use when impacts of toxicity are considered. However, it displayed a higher climate change impact than that of clay bricks. Transport of raw materials to the preparation site played a significant role in the analysis. The next step is to compare the energy used in preparing AAMs.

Development of red mud based sintered artificial aggregates with various industrial wastes

Red mud (RM) has drawn a lot of attention in the search for potential uses in the production of sintered artificial aggregate from industrial waste products. The main objective of the study is to produce an RM-based sintered artificial aggregate (SAA), with several blends (binary, ternary, and quaternary) using various industrial wastes. This study includes assessing the mechanical and physical properties of SAA as well as the sintering parameters in order to determine the appropriate material mix ratio. To achieve these objectives, a comprehensive experimental approach was adopted. A total of 35 different mixtures were formulated by incorporating various industrial wastes as binders and sintering additives. The green pellets were preheated at 105 °C for 24 h, and consecutively sintered at different temperatures, namely 700 °C, 900 °C, 1100 °C, and 1150 °C with a duration of 30 min. A compressive strength test was performed in order to find the mechanical property of SAA similarly water absorption and bulk density tests were conducted to find the physical properties of SAA. To characterize the SAA, scanning electron microscope analysis (SEM), X-ray diffraction (XRD) and energy dispersive x-ray analysis were conducted, and also data analysis was performed using Artificial Neural Network (ANN) tools, yielding accurate predictions. Successfully best compressive strength low water absorption SAA was produced. The best material weight mix ratio for the production of SAA was identified as (A18) RM: Fly Ash: Waste Glass Powder; 78:10:12. Out of all blends the ternary blend (A18) SAA exhibited impressive properties after 30 min of sintering at 1150 °C: high compressive strength of 22.92 MPa, water absorption of 4.26%, and bulk density of 1296.12 kg m−13. This was made possible by the high amount of Al2O3, SiO2, in the combination of fly ash, and waste glass powder with RM. SEM and XRD analysis also confirmed that the (A18) SAA achieved the best compressive strength, and low water absorption due to turning the surface and core area into a solid, reduced internal pores and formed quartz, and hematite phases. The findings of this study serve as a foundation for future work and pave the way for the development of sustainable construction materials.

Bipolar membrane assistant landfill leachate coagulation by bauxite tailings with oxalic acid

In this study, bauxite tailings were innovatively employed as the coagulant resource in the treatment of nanofiltration concentrated landfill leachate (NCLL) via bipolar membrane electrodialysis (BMED). The employment of H2C2O4 as the leaching acid, in lieu of HNO3, not only promoted the leaching of metal ions but also minimized the competitive migration of free H+, attributable to its chelating effect. The COD removal increased from about 40.4 % to about 49.9 %, while the energy consumption (EC) decreased to about 0.05 kWh/g COD when the acid is replaced by H2C2O4. An optimal dosage of bauxite tailing is crucial for effective COD removal. An increase in the initial concentration of H2C2O4 benefits metal leaching, while, an excessive concentration thereof augments the competition of H+ ions, thereby impeding the coagulation process. Furthermore, the current density exerted a notable impact on both COD removal and EC, with an optimal density identified at 5 mA/cm2. Connecting more treatment units still maintains COD removal efficiency at approximately 50 %, with a significant reduction in EC of about 24 %, necessitating only 0.038 kWh/g COD. Humic-like and fulvic-like acids are efficiently coagulated, which represent the principal biorefractory substances in NCLL. Consequently, this research delineates a novel approach for the utilization of bauxite tailings and the treatment of NCLL.

Film-Forming Property of Cement Paste with Red Mud as a Supplementary Cementitious Material

Film-Forming Property of Cement Paste with Red Mud as a Supplementary Cementitious Material

Simultaneous Determination of 16 Rare Earth Elements in Red Mud by Graphite Digestion-ICP-OES

Simultaneous Determination of 16 Rare Earth Elements in Red Mud by Graphite Digestion-ICP-OES

Characterisation of red mud as an embankment material for high-volume utilisations

Characterisation of red mud as an embankment material for high-volume utilisations

Optimization of the treatment of red mud with sulfur dioxide

Optimization of the treatment of red mud with sulfur dioxide

Purification of acidic wastewater containing Cd(II) using a red mud-loess mixture: Column test, breakthrough curve, and speciation of Cd.

In this study, the safety of a red mud-loess mixture (RM-L) for the remediation of groundwater polluted by acid mine drainage (AMD) containing Cd(II) in mining areas was systematically analyzed and clarified. The effects of the initial concentration, flow rate, and packing height on the breakthrough performance and longevity of RM-L as a permeable reactive barrier (PRB) packing material were explored by column tests. The results show that the breakthrough time, saturation time, and adsorption capacity of Cd(II) in RM-L increased with decreasing initial concentration and flow rate, as well as increasing packing height. Moreover, RM-L had a long-term effective acid buffering capacity for acidic wastewater containing Cd(II). An increase in the packing height led to a longer longevity of the PRB than the theoretical value. In addition, the speciation of Cd on RM-L was dominated by carbonate form and iron-manganese oxide form. The surface of the RM-L particles evolved from a dense lamellar structure to small globular clusters after purifying the acidic wastewater containing Cd(II), due to the corrosion of H+ and the reoccupation and coverage by increasingly enriched adsorbates and precipitates of heavy metal ions.

Overview on Hydrometallurgical Recovery of Rare-Earth Metals from Red Mud

Aluminum is produced from its primary bauxite ore through the Bayer process. Although Al is important nowadays in the development of humanity, its production leads to the generation of a huge amount of waste, called red mud. Globally, the estimation of the stock of red mud is about 4 billion tons, with about 10 million tons located in Turkey. The presence of rare-earth elements (REEs) in crucial materials such as red mud makes it a major source of these elements. A number of methods have been developed for treating red mud, which are employed globally to recover valuable products. The application of a suitable method for REE extraction from red mud is a way to overcome the supply risk, contributing to reducing the environmental issues linked to red mud pollution. The current review summarizes the research on red mud processing and examines the viability of recovering REEs from red mud sustainably, utilizing hydrometallurgy and biohydrometallurgy.

Potential of artificial soil preparation for vegetation restoration using red mud and phosphogypsum

Red mud and phosphogypsum have long been a focus and challenge in global industrial waste management, and their low-cost and large-scale utilization technology has always been an urgent need. This study is based on the strong acid-base neutralization reaction between red mud and phosphogypsum, which contain an elemental composition similar to that of natural soil, red mud itself has characteristic of clay minerals, and other auxiliary materials (i.e. rice husk powder, bentonite, fly ash, polyacrylamide flocculant and microbial suspension) were added, so as to explore the potential of synergistically prepared artificial soil for vegetation restoration. The results showed that the artificial soils exhibited physicochemical characteristics (e.g., pH, moisture content, cation exchange capacity) similar to those of natural soil, along with abundant organic matter, nitrogen, phosphorus, and potassium contents, meeting the growth requirements of plants. The artificial soils were able to support favorable growth of suitable plants (e.g., sunflower, wheat, rye grass), accumulating high levels of diverse enzymatic activities, comparable to those in natural soils (e.g., catalase, urease, phosphatase), or even surpassing natural soils (e.g., sucrase), and rich microorganism communities, such as Cyanobacteria, Proteobacteria, Actinobacteria in the bacteria domain, and Ascomycota in the fungi domain, were initially developed. It's suggested that preparing 1 ton of artificial soil entails synergistic consumption of 613.7 kg of red mud and 244.6 kg of phosphogypsum, accounting for mass proportions of 61.4 % and 24.5 %, respectively. In future, more evaluations on the leaching loss of nutrients and alkalinity and the environmental risks of heavy metals should be conducted to more references for the artificial soil application. In summary, the preparation of artificial soil is a very simple, efficient, scalable and low-cost collaborative resource utilization scheme of red mud and phosphogypsum, which has great potential for vegetation restoration in some places such as tailings field and soil-deficient depression.

Pengaruh Pemberian Red Mud dan Bokasi Limbah Sayur Terhadap Pertumbuhan dan Hasil Selada Hijau pada Tanah Gambut

This research aims to find the best interaction dose of red mud and vegetable waste on the growth and yield of green lettuce plants on peat soil. This research used an experimental method with a Completely Randomized Factorial Design pattern consisting of two factors, each consisting of 3 treatment levels with 3 repetitions and consisting of 4 sample plants so that the total number of plants was 108 plants. The first factor, namely red mud (A) consists of a1 = 18 tonnes/ha equivalent to 220.5 g/plant, a2 = 20 tonnes/ha equivalent to 245 g/plant and a3 = 22 tonnes/ha equivalent to 269.5 g /plant and the second factor consists of b1 = 15 tonnes/ha equivalent to 184 g/plant, b2 = 20 tonnes/ha equivalent to 245 g/plant and b3 = 25 tonnes/ha equivalent to 306 g/plant. Observation variables include: Number of leaves, root volume, plant dry weight and plant fresh weight. Apart from the variables above, observations were also made of environmental conditions which included: soil pH, air temperature, relative humidity and daily rainfall. Based on the research results, it shows that giving 18 tons/ha of red mud is the best dose in increasing the fresh weight of plants and 20 tons/ha of vegetable waste fertilizer is the best dose in providing growth in the number of leaves in the 4th week of green lettuce plants on peat soil. Keywords: vegetable waste bokasi, red mud, green lettuce, peat soil

Nickel-doped red mud-based Prussian blue analogues heterogeneous activation of H2O2 for ciprofloxacin degradation: waste control by waste.

Red mud (RM) is a typical bulk solid waste with Fe/Al/Si/Ca-rich characteristics that has been used to prepare various heterogeneous catalysts such as iron-based catalysts and supported catalysts. Prussian blue analogues (PBA) is a low-cost, environmentally friendly, and active site rich iron-based metal organic framework, but its catalytic properties are adversely affected by their easy aggregation. In this study, nickel-doped RM-based PBA (RM-Ni PBA) was synthesized by acid dissolution-coprecipitation method for the degradation of ciprofloxacin (CIP). The characterization showed that RM-Ni PBA was a material with excellent dispersibility, large specific surface area, and abundant active sites. The degradation results showed that the removal efficiency of CIP in the RM-Ni PBA/H2O2 system was 16.63, 1.78, and 1.81 times that of RM, RM-PB, and Ni PBA, respectively. It was found that 1O2 was the main reactive oxygen species (ROS) dominated the degradation process, and its formation was accompanied by the mutual conversion of Ni(II)/Fe(II) and Ni(III)/Fe(III). Notably, the degradation process maintained a satisfactory efficiency over a wide pH range (3-9) and exhibited strong anti-interference ability against impurities such as Cl-, SO42-, and NO3-. The components and contents of RM-Ni PBA remained relatively stable during the degradation process. In addition, the degradation intermediates of CIP were identified, and possible degradation pathways were proposed. This study is expected to provide theoretical basis and technical guidance for the application of RM-based heterogeneous catalyst in the treatment of antibiotic wastewater.

Comparison of different treatment methods which are used for phenol removal: A mini review

ABSTRACT This article aims to provide a comprehensive overview of the various adsorption methods developed over time for phenol removal. Phenolic substances pose significant threats to aquatic ecosystems, wildlife, and human health. If not properly controlled and treated before discharge, industrial effluents contaminated with phenol can cause detrimental effects on surface and groundwater resources. In comparison with advanced treatments such as ozonation, UV therapy, and the Fenton process, which are associated with higher energy costs, conventional physicochemical treatment methods like adsorption, chemical treatment, membrane filtration, and distillation offer superior removal efficiencies. Pistachio nut shell ash, Moringa peregrina tree shell ash, agricultural fibres, red mud, low-cost clay, olive mill waste, natural zeolites, rubber seed coat, peat, fly ash, and bentonite are just a few examples of the adsorbents and adsorption processes that have been used in literature to remove phenol and its derivatives. For instance, biosorption has been shown to be a successful technique with room for further study in this area regarding regeneration and cost–effectiveness. As a result, numerous researchers in the field of phenolic treatment have emphasized the effectiveness of physicochemical processes over time. Furthermore, additional investigation is required to determine the practical application of inexpensive adsorbents on commercial basis.

Numerical Simulations of the Impact of CaO/Al2O3 on the Structure and Crystallization Behavior of Red Mud

Numerical Simulations of the Impact of CaO/Al2O3 on the Structure and Crystallization Behavior of Red Mud

The stepwise extraction strategy for selective recovery of scandium from hydrochloric acid leachate of bauxite residue based on reactivity of metal ions

The recovery of Sc from secondary resources such as bauxite residue has received considerable interest. As the main elements in bauxite residue, Fe and Al exhibit significant interference in the selective separation of Sc. Herein this work, a stepwise extraction strategy of Sc from the hydrochloric acid leachate of bauxite residue was proposed based on the differences in reactivity of metal ions. The results show that Fe(III) and Sc(III) can be extracted sequentially with Aliquat 336 and Cyanex 272 from hydrochloric leachate. The separation factors of Fe/Sc, Fe/Al and Sc/Al were up to 4.3 × 104, 4.1 × 104 and 2.6 × 103, respectively. The results of spectroscopic characterization indicate that a cation exchange and coordination occur during the extraction of Sc(III) with Cyanex 272. The Sc(III) complex with Cyanex 272 (H2A2) is presented as ScClA2(HA)2¯. The loaded Aliquat 336 and Cyanex 272 can be stripped with acidified sodium sulfite and oxalic acid, respectively. The extraction-stripping performance of the stepwise separation route was investigated and the extraction efficiency of Fe(III) and Sc(III) can be remained above 97 % after 5 cycles. The proposed strategy has the potential to be considered industrially for the recovery of Sc from bauxite residue and other secondary resources.

Geomechanical and Microstructural Behaviour of Expansive Soil Stabilized with Red Mud and GGBS: An Experimental Investigation

Geomechanical and Microstructural Behaviour of Expansive Soil Stabilized with Red Mud and GGBS: An Experimental Investigation