Red Mud Research Articles

Effect of silica on the properties of red mud based geopolymer mortar for synthesis of sustainable bricks

Effect of silica on the properties of red mud based geopolymer mortar for synthesis of sustainable bricks

Analysis of mechanical properties of fly ash and bauxite residue based geopolymer concrete using ANN, Random Forest and Counter propagation neural network

Analysis of mechanical properties of fly ash and bauxite residue based geopolymer concrete using ANN, Random Forest and Counter propagation neural network

Amorphous Fe substrate enhances nitrogen and phosphorus removal in sulfur autotrophic process

The autotrophic denitrification of coupled sulfur and natural iron ore can remove nitrogen and phosphorus from wastewater with low C/N ratios. However, the low solubility of crystalline Fe limits its bioavailability and P absorption capacity. This study investigated the effects of amorphous Fe in drinking water treatment residue (DWTR) and crystalline Fe in red mud (RM) on nitrogen and phosphorus removal during sulfur autotrophic processes. Two types of S-Fe cross-linked filler particles with three-dimensional mesh structures were obtained by combining sulfur with the DWTR/RM using the hydrogel encapsulation method. Two fixed-bed reactors, sulfur-DWTR autotrophic denitrification (SDAD) and sulfur-RM autotrophic denitrification (SRAD), were constructed and stably operated for 236 d Under a 5–8-h hydraulic retention time, the average NO3−–N, TN, and phosphate removal rates of SDAD and SRAD were 99.04 %, 96.29 %, 94.03 % (SDAD) and 97.33 %, 69.97 %, 82.26 % (SRAD), respectively. It is important to note that fermentative iron-reducing bacteria, specifically Clostridium_sensu_stricto_1, were present in SDAD at an abundance of 58.17 %, but were absent from SRAD. The presence of these bacteria facilitated the reduction of Fe (III) to Fe (II), which led to the complete denitrification of the S-Fe (II) co-electron donor to produce Fe (III), completing the iron cycle in the system. This study proposes an enhancement method for sulfur autotrophic denitrification using an amorphous Fe substrate, providing a new option for the efficient treatment of low-C/N wastewater.

The Impacts of Red Mud on Road Performance and Aging Resistance of Asphalt Mixture

The Impacts of Red Mud on Road Performance and Aging Resistance of Asphalt Mixture

Collaborative separation of nickel and iron from nickel laterite ore and red mud

ABSTRACT In this study, we investigated a nickel laterite ore with Ni content of 1.56 wt% and a red mud with Fe content of 20.98 wt%, the main Ni-bearing mineral in the nickel laterite ore was nickel-lizardite, and the main Fe-bearing mineral in the red mud was hematite. A novel process of roasting and magnetic separation was purposed to extract nickel and iron from the nickel laterite ore and red mud. The nickel laterite ore, red mud, calcium chloride, and coke were mixed and put in a roaster for roasting, and the ferronickel concentrate was obtained from the roasted ore by magnetic separation. The results showed that a ferronickel concentrate with Ni content of 7.97 wt%, Fe content of 73.09 wt%, iron recovery of 76.87%, and nickel recovery of 90.28% was obtained under the optimal conditions: a mass ratio of m (nickel laterite ore): m (red mud) : m (coke) : m (calcium chloride) : of 0.6:0.4:0.2:0.1, a roasting temperature of 1373 K, a roasting time of 90 min, a grinding fineness of − 0.045 mm occupying 90%, and a magnetic field strength of 0.20 T. The main minerals in the ferronickel product were metallic Fe and FeNi.

Red mud modified phosphogypsum based self-leveling mortar: Hydration mechanism, heavy metal migration law and spatial distribution characteristics

In the production processes of phosphoric acid and alumina, chemical enterprises generate solid waste such as red mud (RM), phosphogypsum (PG), and fly ash (FA). The environmentally friendly utilization of these waste materials is of crucial significance. Therefore, this study focuses on investigating the impact of collaborative modification using diverse solid wastes on the macroscopic properties and internal microstructure of self-leveling mortar. Through a careful selection process, the optimal ratio for red mud and phosphogypsum self-leveling mortar(RPSM) has been identified during the research. This study not only provides substantial support for the effective utilization of solid waste but also contributes to the improvement of overall performance and structural characteristics of the mortar. Based on this, the hydration characteristics, leaching patterns, and spatial distribution characteristics of heavy metals in RPSM were evaluated. The research revealed that the optimal ratios of RM, PG, FA, PC, river sand, and heavy calcium carbonate powder in RPSM were 20.7%, 13.8%, 17.1%, 13.8%, 17.3%, and 17.3%, respectively. Under a water-binder ratio of 0.18, the flexural and compressive strength of the mortar specimens after 14 d of curing can reach 4.3 and 31.6 MPa. Through comprehensive analysis and discussion of the performance, microstructure, and dynamics of the hydration process of RPSM, the main processes of mortar hydration were elucidated. Environmental risk assessments indicated no environmental risks from heavy metals in RPSM. Human health risk assessment suggested carcinogenic risks from Cr and Cd in RPSM through oral exposure, leading to restrictions on the content of characteristic heavy metals in different application scenarios. Furthermore, fitting results of the release kinetics of heavy metals indicated that the leaching of heavy metals in RPSM can be well fitted with kinetic models, allowing the determination of the optimal safe age of RPSM containing harmful heavy metals. Finally, using interpolation and vertical distribution simulation by software such as ArcGIS, the spatial distribution characteristics of heavy metals in RPSM during use were analyzed. The research can supply fundamental academic support for the recycling of solid wastes like RM and the control of environmental risks associated with heavy metal leaching in building materials.

Simulation study on basic road performance and modification mechanism of red mud modified asphalt mixture

Abstract In order to study the basic road performance and the mechanism of red mud modified asphalt, Marshall test, rut test, freeze-thaw splitting test, and immersion Marshall test were carried out for matrix asphalt mixture and red mud modified asphalt mixture, and molecular simulation technology was introduced to study the mechanism of red mud modified asphalt. The results showed that the penetration rate of red mud modified asphalt was lower than that of the matrix asphalt, and the softening point of asphalt was significantly improved after the addition of red mud, and the mixing of red mud reduced the asphalt ductility greatly. The intensity ratio (test strength ratio; TSR) of the freeze-thaw test of red mud modified asphalt under 3, 5, 7, 9, and 11% was increased by 13.18, 11.22, 13.54, 12.01, and 8.45%, respectively, compared with the matrix asphalt mixture, and the dynamic stability value increased by 127.23, 176.87, 200.99, 96.23, and 12.95%; the residual stability value of the immersion Marshall test increased obviously. Generally, the research of red mud modified asphalt is quite worthy, it can solve the problem of aluminum ore slag and reuse of resources, and provide a new way to extend the industrial chain.

Sonophotocatalytic Degradation of Reactive Black 5 in Simulated Dye Wastewater Using ZnO and Activated Red Mud Sonophotocatalyst

Sonophotocatalytic Degradation of Reactive Black 5 in Simulated Dye Wastewater Using ZnO and Activated Red Mud Sonophotocatalyst

Waste Management of Red Mud and Fly Ash to Utilize in Road Subgrade Material

Red mud (RM) is a waste material obtained during the production of aluminum from bauxite minerals. RM causes environmental pollution due to its high alkaline properties. Therefore, RM materials are stored in waste reservoirs. As production continues, the number of required waste reservoirs increases day by day. This study aims to utilize RM waste material in construction structures to contribute to the economy. The research investigates the potential use of RM waste material as road fill material. RM was improved using another waste material of fly ash (FA) since RM has low strength. Atterberg limit tests, compaction tests, unconfined compression tests, CBR tests, and SEM analyses were conducted on stabilized RM samples. In the physical properties of stabilized RM, Atterberg limits and optimum moisture content increase and density decreases since FA content increases. In the mechanical properties of stabilized RM, unconfined compressive strength, initial and secant modulus of elasticity, and California bearing ratio increase and maximum peak strain decreases since FA content and curing period increase. SEM images prove the increase in mechanical properties due to the cementation products (CSH and CAH gels) formed in the microstructure of stabilized RM. The results showed that RM waste stabilized with FA can be used as road subgrade material.

Ash Fluidity and Regulation Mechanism of Iron-Rich Low-Rank Coal in High-Temperature Gasification Process

ABSTRACT To realize the high-efficiency utilization of iron-rich coal, it is necessary to conduct research on ash flow characteristics and regulatory mechanisms. The ash flow test was carried out, and we introduced additives such as Huajin red mud (HJ), pipe scale (GDG), diatomite (GZT), and Naomaohu coal (NMH). The results revealed that the elevated Fe2O3 content triggers the formation of metallic iron, leading to poor high-temperature fluidity. NMH and HJ additives have the ability to depolymerize SiO2 and Al2O3 structures. This generates higher contents of anorthite and sodium nepheline. The inclusion of GDG ash promoted the formation of cordierite and forsterite, contributing to improved slag flow. Caution is warranted when using a higher proportion of GDG ash additive, as excessive MgO can combine with Al2O3 to form a high-melting-point spinel mineral. GZT ash leads to an increase in quartz content. During cooling, mullite preferentially precipitates from the liquid phase, further reducing high-temperature fluidity.

Study on the adsorption performance of Cu2+ in wastewater by red mud

The treatment of copper-nickel wastewater has consistently posed a challenging problem in the field of environmental protection. In this experimental study, the adsorbent used was prepared from Bayer's method-derived red mud (RM). The adsorption characteristics of RM adsorbent on Cu2+ in copper-nickel wastewater, as well as the impact of Ni2+ on the removal effectcy of Cu2+, were investigated. The adsorption performance of Cu2+ in copper-nickel wastewater by adsorbent dosage, adsorption time and pH were investigated, and the adsorption mechanism was discussed. The adsorption process conformed to the pseudo-second-order kinetic model (R2=0.986) and the Langmuir model (R2=0.989), indicating that it was a monolayer chemical adsorption process. The raw materials were characterized using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray fluorescence (XRF). The results indicated that the adsorption process of Cu2+ and Ni2+ on RM was primarily influenced by surface chemical groups such as O-H, C-O-C, Si-C, and Si-O, among others. The adsorption rate of Cu2+ by RM could achieve 100% when the concentration of Cu2+ solution was 100mg/L, with an optimal dosage of adsorbent at 0.20mg/L and the best adsorption effect observed after 240minutes. The adsorption of Cu2+ and Ni2+ by RM exhibits unidirectional competitive adsorption behavior. Furthermore,in competitive adsorption experiments, RM exhibits good selectivity towards Cu2+, with Ni2+ exhibiting minimal inhibitory effect on Cu2+ when the two elements coexist. Therefore, this paper offers potential research value for the large-scale application of RM in copper-nickel wastewater treatment processes.

Efficient degradation of m-cresol by MnO-doped red mud catalyst activating peroxymonosulfate process: Performance and mechanism

M-cresol, one of phenolics, is highly toxic, refractory, and threatens human health and ecological safety. The study on the efficient m-cresol degradation technologies is crucial and helpful to restrain its discharge into water body. A composite of MnO-doped red mud (RM) to activate peroxymonosulfate (PMS) for the m-cresol degradation was fabricated and employed, favorable to the recycling and utilization of RM. Considering the catalytic activity and cost, 0.1 M/RM@G exhibited an excellent degradation capacity attributing to strong Fe3O4 and MnO synergy and was considered as the best catalyst among the investigative catalysts. 100 % of m-cresol and 71.4 % of COD could be degraded within 90 min under 2 g/L catalyst, 10 mM of PMS, 3–8 of initial pH and 50 mg/L m-cresol in the 0.1 M/RM@G/PMS system. The reaction rate constant (0.045 min−1) of 0.1 M/RM@G was much larger than RM@G (0.012 min−1), ARM (0.0048 min−1) and WRM (0.0028 min−1). Main Mn and Fe active components and abundant mesoporous structures on the catalyst surface could efficiently drove electron transfers, and further accelerated the redox cycles of Mn(III)Mn(II) and Fe(III)Fe(II) for activating PMS. 1O2 played a crucial role in degrading m-cresol. Based on the experiment data, the generation mechanism of radicals and the possible pathways of m-cresol degradation were proposed in the 0.1 M/RM@G/PMS system. This finding provides a new way for the synthesis of the efficient catalyst with RM and optimal operating strategies for the treatment of m-cresol wastewater.

Phosphorus adsorbed by HCl desorption–activated red mud adsorbents: a molecular dynamics studys

In this study, modified red mud after phosphorus adsorption was used as the adsorbent, and HCl and deionized water were used as desorbents to desorb phosphorus. The components in the adsorbent were optimized based on density functional theory, and adsorbent and desorbent models were established. Molecular dynamics simulation was performed to determine the phosphorus concentration before and after desorption, interaction energies, radial distribution function(RDF), mean-square displacement(MSD), and diffusion coefficient. The Monte Carlo method was used to simulate the desorption isotherm, desorption site, heat of desorption, and desorption energy. Simulation results showed that deionized water could only desorb phosphorus on the adsorbent surface, and the stability of the system deteriorated upon adding HCl. HCl destroyed the ionic and hydrogen bonding between the O atoms in H2PO4 − and reactive metal and oxygen atoms in the activated red mud particles. Moreover, the van der Waals force decreased considerably. The ionic and hydrogen bonds between H2PO4 − and the surface of activated red mud particles were broken by HCl, which accelerated the desorption of phosphorus from the adsorbent surface. The interaction between HCl and phosphorus accelerated the diffusion, which decreased the adsorption capacity. Moreover, the desorption capacity increased with increasing temperature.

Rapid wet grinding carbonation of sintering red mud for highly efficient CO2 sequestration and Cr solidification

Sintering red mud (SRM) is an alkaline and aqueous solid waste from bauxite sintering for alumina production. The challenges in the effective utilization of SRM are strong alkalinity, aqueous state and leaching toxicity of the heavy metals. Herein, a rapid wet grinding carbonation technique of simultaneous injection of CO2 in wet grinding process was proposed. The rapid carbonation of alkaline metal ions and the efficient solidification of heavy metal ions were achieved in the wet grinding carbonation. After 40 min of short-term carbonation, the CO2 uptake and carbonation degree of SRM reached 30.25 g CO2/100 g SRM and 79.31 % respectively. The high-efficiency CO2 uptake of SRM was attributed to the continuous stripping of the attached surface CaCO3 layer by wet grinding, the constantly exposed new surface area after refinement and the largely increased Ca2+ concentration, which was 12.5 times the initial value at 10 min. Furthermore, the simultaneous carbonation realized the solidification of dissolved chromium ion (Cr(III)/Cr(VI)), which was transformed into CaCrO4, Ca3Cr2(OH)12 or Cr(OH)n(CO3)n(3n-3)- complexes under the weak acid environment of CO2. After 40 min of wet grinding carbonation, the Cr concentration was notably decreased by 85.71 %, which was lower than the limit of groundwater standard requirement.

Utilization of red mud in high-performance grouting material for semi-flexible pavement

Utilization of red mud in high-performance grouting material for semi-flexible pavement

Synthesis of BiOX-Red Mud/Granulated Blast Furnace Slag Geopolymer Microspheres for Photocatalytic Degradation of Formaldehyde.

Release of formaldehyde gas indoors is a serious threat to human health. The traditional adsorption method is not stable enough for formaldehyde removal. Photocatalytic degradation of formaldehyde is effective and rapid, but photocatalysts are generally expensive and not easy to recycle. In this paper, geopolymer microspheres were applied as matrix materials for photocatalysts loading to degrade formaldehyde. Geopolymer microspheres were prepared from red mud and granulated blast furnace slag as raw materials by alkali activation. When the red mud doping was 50%, the concentration of NaOH solution was 6 mol/L, and the additive amount was 30 mL, the prepared geopolymer microspheres possessed good morphological characteristics and a large specific surface area of 38.80 m2/g. With the loading of BiOX (X = Cl, Br, I) photocatalysts on the surface of geopolymer microspheres, 85.71% of formaldehyde gas were adsorbed within 60 min. The formaldehyde degradation rate of the geopolymer microspheres loaded with BiOI reached 87.46% within 180 min, which was 23.07% higher than that of the microspheres loaded with BiOBr, and 50.50% higher than that of the microspheres loaded with BiOCl. While ensuring the efficient degradation of formaldehyde, the BiOX (X = Cl, Br, I)-loaded geopolymer microspheres are easy to recycle and can save space. This work not only promotes the resource utilization of red mud and granulated blast furnace slag, but also provides a new idea on the formation of catalysts in the process of photocatalytic degradation of formaldehyde.

Experimental study on performance, hydration, and sustainability of coal gasification coarse slag based geopolymers for sustainable environment

The large-scale application of coal gasification technology generates a large amount of coal gasification coarse slag (CGCS) difficult to treat. In this study, low-carbon geopolymers (CGRC) were produced using CGCS and ground granulated blast furnace slag (GGBS) as precursors, whereas red mud (RM) and carbide slag (CS) served as solid waste activators. The effects of the binder/activator, RM/CS and CGCS/GGBS ratios and the curing age on the compressive strength, setting time, heavy metal leaching, XRD, SEM-EDS, TG-DTG, FTIR, and LF NMR of CGCS-based geopolymers were investigated, and the hydration mechanism of CGRC geopolymer was disclosed. The results showed that the binder/activator ratio had a negligible effect on the ultimate compressive strength (UCS), the RM/CS ratio had a noticeable impact on the compressive strength and setting time, and increasing the GGBS content significantly improved the performance of CGCS-based geopolymers. Therefore, the synergistic effect of RM and CS led to the activation of CGCS and GGBS. The main hydration products were N-A-S-H, N/C-A-S-H, C-A-S-H gel, CH, and CaCO3. Furthermore, the decrease of the RM/CS ratio which promoted the gel transformation from metastable N-A-S-H to N/C-A-S-H configuration and then to stable C-A-S-H state, finally forming a denser gel matrix. The amounts of various heavy metals leached from CGCS-based geopolymers were even lower than those required by the national standards; therefore the material met the requirements for environmental protection. Furthermore, all raw materials belong to solid waste, which reduces carbon emissions.

The Study of Acid Leaching on the Mineralogical and Microscopic Changes of Red Mud

The Study of Acid Leaching on the Mineralogical and Microscopic Changes of Red Mud

Construction of a Visible-Light-Response Photocatalysis-Self-Fenton Degradation System of Coupling Industrial Waste Red Mud to Resorcinol-Formaldehyde Resin.

Heterogeneous photocatalysis-self-Fenton technology is a sustainable strategy for treating organic pollutants in actual water bodies with high-fluent degradation and high mineralization capacity, overcoming the limitations of the safety risks caused by adding external iron sources and hazardous chemicals in the homogeneous Fenton reaction and injecting high-intensity energy fields in photo-Fenton reaction. Herein, a photo-self-Fenton system based on resorcinol-formaldehyde (RF) resin and red mud (RM) was established to generate hydrogen peroxide (H2O2) in situ and transform into hydroxy radical (•OH) for efficient degradation of tetracycline (TC) under visible light irradiation. The capturing experiments and electron spin resonance (ESR) confirmed that the hinge for the enhanced performance of this system is the superior H2O2 yield (499 μM) through the oxygen reduction process (ORR) of the two-step single-electron over the resin and the high concentration of •OH due to activation effect of RM. In addition, the Fe2+/Fe3+ cycles are accelerated by photoelectrons to effectively initiate the photo-self-Fenton reaction. Finally, the possible degradation pathways were proposed via liquid chromatography-mass spectrometry (LC-MS). This study provides a new idea for environmental recovery in a waste-based heterogeneous photocatalytic self-Fenton system.

Red-mud additive geopolymer composites with eco-friendly aggregates

Geopolymers have an increasing importance and a crucial task in engineering, especially structural engineering. Geopolymers are sustainable composites with low carbon emissions rather than cement composites. It leads to be an alternative to cement composites and the structure of geopolymer composites can allow to utilize various industrial and non-industrial wastes and by-products. In this point, there is an unclarity of waste material contributions to the geopolymeric composites and this issue is worth to study and an area of ongoing research. In this paper, it is aimed to produce red mud additive sustainable geopolymer composites with various eco-friendly fillers (brick powder, waste marble powder, glass powder, ceramic powder, and rice husk ash). 28 mixtures were designed, many specimens produced, and tested. In the first step of the experimental stage, the physical, the mechanical and the durability properties were determined and evaluated. At second, the best geopolymer composites were determined with a multi-criteria decision-making method (MCDM). 22 geopolymer parameters were employed in MCDM. As a results, 25% marble dust, 25% brick powder, 75% ceramic powder, 50% rice husk ash and 50% glass powder were the optimum ratios to obtain maximum compressive strength in terms of waste types and the highest compressive strength is obtained for 25% brick powder among the results. The best geopolymer composite was determined as GWGP50 with 50% glass powder + 50% recycled aggregate in a holistic manner with TOPSIS. Results showed that geopolymer GWGP50 had aspects that were open to development.