Treatment Of Red Mud Research Articles

Preparation of efficient adsorbent for methylene blue and Congo red by co-hydrothermal of red mud with food waste compost

Herein, a novel red mud-carbon composite (RFBC) was prepared through co-hydrothermal treatment of red mud with food waste compost, and its adsorption property was evaluated on Methylene blue (MB) and Congo red (CR), selected model dyes in aqueous solution. The adsorption process conformed to pseudo-second-order kinetic, intraparticle diffusion, and the Redlich-Peterson isotherm models. RFBC exhibited a maximum sorption of 124.06 mg·g-1 for MB and 2959.35 mg·g-1 for CR at 298 K. Isothermal and thermodynamic studies demonstrated that adsorption of MB and CR by RFBC were spontaneous and exothermic, governed by physisorption and chemisorption. Furthermore, the possible adsorption mechanisms are pore filling, electrostatic attraction, hydrogen bonding, and π-π interactions. After five consecutive adsorption-desorption cycles were completed, the RFBC demonstrated an adsorption efficiency exceeding 70 % in relation to dyes, affirming its exceptional reusability. This study suggested this red mud-carbon composite had high potential as a novel and promising adsorbent for dye removal from wastewater.

A review of the engineered treatment of red mud: Construction materials, metal recovery, and soilization revegetation

Red mud, known as bauxite residue, is an alkaline solid waste generated during alumina production. Globally, the stockpile of red mud is about 3 billion tons and is increasing at a rate of 150 million tons per year. The global production of red mud is mainly distributed in China (28.2 %), Oceania region (22.4 %), South America (14.6 %), Europe (12.9 %), and North America (8.8 %). The increasing stockpile of red mud has posed a huge challenge to safe disposal while restricting the development of the alumina industry. The comprehensive utilization of red mud still needs green, efficient, and massive consumption methods. This work gives a review of the engineered treatment of red mud, including the characteristics and threats, as well as the engineered application through construction materials, metal recovery, and soilization revegetation. For red mud with a high content of metals, resource recovery of valuable metals and rare earth elements is a preferred choice, meeting the circular economy concept. Recovery of valuable metals from red mud can be achieved by magnetic separation, hydrometallurgy, and bioleaching. Hydrometallurgy is promising for recovering valuable metals such as Fe, Al, V, Ti, and rare earth elements, and the recovery is up to 99 %. Construction materials such as cement, geopolymers, and ceramics is an efficient alternative for the massive consumption of red mud, and the high-performance concrete with the compressive strength (129.5 MPa) can be obtained. This strategy is limited by the low price of construction materials, the lowered quality by alkaline components, and potential threats of toxic elements in red mud. Soilization of red mud with ecological restoration is promising for the sustainable management of red mud dam. To accelerate the process of red mud soilization, amendments such as gypsum, organic matter, and microorganisms can be added to neutralize red mud (lowering pH from 10 to 12 to near 7), promote the formation of agglomerates, and provide nutrients, promote the conversion of red mud into soil-like substrate. The phytoremediation of red mud can be realized after effective regulation, finally realizing vegetation establishment of red mud. This work provides technological and practical guidance for the engineered disposal of red mud.

Effect of the combined treatment of red mud and gypsum on plant-available arsenic in acidic and alkaline soils

Effect of the combined treatment of red mud and gypsum on plant-available arsenic in acidic and alkaline soils

Integration of CO2 sequestration with the resource recovery of red mud and carbide slag

Red mud and carbide slag, strongly alkaline solid wastes, are produced during the manufacturing of alumina and acetylene gas, respectively. Improper management of these wastes can pose significant environmental hazards. This study proposed a novel method for the collaborative treatment of red mud and carbide slag, enabling the recovery of constituent elements with CO2 sequestration. During the hydrochloric acid leaching process, Si was reclaimed as Si-rich residue, whereas Ti, Al, Ga, Fe, and Sc were stepwise recovered as Ti-rich product, Al/Ga-rich filtrate, and Fe/Sc-rich product via the subsequent hydrolysis, co-precipitation, and alkali leaching processes, respectively. Utilizing carbide slag to replace the energy-intensive NaOH for pH adjustment in the leaching solution resulted in a Ca2+ concentration of 21,922 mg/L in the filtrate after co-precipitation. Through further mineralization process, CO2 sequestration was achieved alongside the production of CaCO3 with the content reaching 98.5 % along with a whiteness of 94.4 %. Furthermore, by adjusting the experimental parameters in the mineralization process, controlled manipulation of the phase and morphology of the CaCO3 product could be achieved to meet various industry requirements. To summarize, the complete resource recovery of red mud and carbide slag was achieved in this study, demonstrating the promising potential in practical applications.

Optimization of the treatment of red mud with sulfur dioxide

Optimization of the treatment of red mud with sulfur dioxide

Integration of lactic acid biorefinery with treatment of red mud from alumina refinery: win–win paradigm for waste valorization

The cost of detoxification and neutralization poses certain challenges to the development of an economically viable lactic acid biorefinery with lignocellulosic biomass as feedstock. Herein, red mud, an alkaline waste, was explored as both a detoxifying agent and a neutralizer. Red mud treatment of lignocellulosic hydrolysate effectively removed the inhibitors generated in dilute acid pretreatment, improving the lactic acid productivity from 1.0 g/L·h−1 to 1.9 g/L·h−1 in later fermentation. In addition, red mud could replace CaCO3 as a neutralizer in lactic acid fermentation, which in turn enabled simultaneous bioleaching of valuable metals (Sc, Y, Nd, and Al) from red mud. The neutralization of alkali in red mud by acids retained in lignocellulosic hydrolysate and lactic acid produced from fermentation led to effective dealkalization, rendering a maximum alkali removal efficiency of 92.2 %. Overall, this study offered a win–win strategy for the valorization of both lignocellulosic biomass and red mud.

Trends in research on characterization, treatment and valorization of hazardous red mud: A systematic review

Meta-analysis of red mud-related literature in English published from 1976 to 2022 and in Chinese from 1990 to 2022 was performed to support critical analysis and evaluation of the available literature based on the following aspects of red mud research: (a) characterization, (b) treatment for harmfulness minimization, (c) recovery of valuable metals, (d) environmental applications, and (e) uses as construction materials. It was found that (a) sinter red mud tended to contain more silica and calcium, and less iron, sodium and aluminium compared to Bayer red mud; (b) gypsum was the most frequently used agent for harmfulness reduction treatment of red mud, followed by flue gas/CO2; (c) the mean optimal pH for adsorption of major anionic pollutants was 8.42 ± 1.13 (arsenite), 3.73 ± 0.68 (arsenate), 3.50 ± 2.38 (phosphate), 4.43 ± 1.04 (fluoride) and 3.80 ± 1.54 (chromate); (d) wastewater treatment has attracted more attention compared to contaminated soils and waste gases; (e) recovery of iron and scandium has attracted more attention compared to other metals; (f) cement making has been the focus in construction uses. Most of the research findings were based on laboratory-scale experiments that focused on efficacy rather than efficiency. There was a lack of integrated approaches for research in red mud valorization.

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

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

Composition and Properties of Iron Oxides in the Products of Hydrothermal Treatment of Red Mud and Bauxites

Composition and Properties of Iron Oxides in the Products of Hydrothermal Treatment of Red Mud and Bauxites

Sustainable application of sodium removal from red mud: Cleaner production of silicon-potassium compound fertilizer

The treatment of red mud, solid waste produced from alumina preparation, is an urgent topic for reducing environmental pollution and recycling valuable elements to comprehensively utilize secondary resources. In this study, a novel method for producing silicon-potassium compound fertilizer by KOH hydrothermal leaching in red mud is proposed to remove sodium and simultaneously obtain a high-quality mineral fertilizer containing silicon and potassium. The results reveal that potassium aluminum silicate with high crystallinity can be formed from KAlO2 solution reacting with K2SiO3 at a temperature above 80 °C. With a 360 g/L K2O hydrothermal leaching temperature of 240 °C, the Na2O content of the red mud transformation residue can be reduced to 0.5%, the full K2O content reaches 12.35%, and the effective K2O and SiO2 contents can reach 12.20% and 18.59%, respectively. When the molar ratio of Na2O to K2O is lower than 0.0625 in the sodium-potassium mixed solution, the red mud transformation residue indices obtained from hydrothermal treatment are close to the abovementioned values. All meet the market requirements of inorganic compound fertilizers and have great potential in agricultural applications, which provides a good solution for the large-scale harmless and sustainable reuse of red mud.

Efficient Selective Extraction of Scandium from Red Mud

ABSTRACT The huge reserves of red mud have a significant potential source of scandium. The scandium can be recovered from red mud by direct acid leaching but the extraction yields are generally low, and the leaching efficiency of iron and silicon is higher. Therefore, the highly selective process steps (a combined sulfation-roasting-water leaching process) were studied to extract scandium from red mud, and in order to minimize costs and waste generated. This study focuses on the phase transformation mechanism and leaching behavior of Sc, Na, Al, Fe, Ti, Ca, and Si in the red mud sulfation-roasting-water leaching process. The results show that the maximum Sc leaching efficiency of 91.98% was obtained at optimum conditions: the roasted at 1023 K for 60 min, the ratio of sulfuric acid to red mud of 0.9 mL/g, the leaching temperature is 323 K, the liquid-to-solid ratio of 5 mL/g, and stirred constantly at 200 rpm leach for 2 h. While the leaching efficiencies of Ca, Na, Fe, Al, Si, and Ti are 21.05%, 93.26%, 1.21%, 9.51%, 1.42%, and 0, respectively. The sulfation-roasting-water leaching process proves to be a promising technique and commercially viable process that allows selective extraction of scandium from red mud, which may contribute to provide options for the treatment of red mud produced continuously by the aluminum industry.

Experimental Research on Vortex Melting Reduction of High-Iron Red Mud (Bauxite Residue).

In this study, the advantages of the vortex melting reduction treatment of red mud were verified. Vortex melting reduction can improve the feeding rate, promote the reaction and the directional deposition of iron, which was conducive to the separation of slag and gold. The effects of different adding methods, stirring speed and reaction time on iron recovery were investigated by using red mud, aluminum leached slag and calcified slag as raw materials. According to the experiment, the best reaction conditions were that the raw material put into the furnace by rolling pellets, stirring speed 125 RPM, and reaction time 30min. The results provided an experimental basis for the harmless and high-value utilization of high-iron red mud treated by vortex melting reduction.

Use of red mud activated at different temperatures as a low cost adsorbent of reactive dye

ABSTRACT Red mud, a waste product generated during alumina extraction from bauxite, could be used as a low-cost adsorbent. Here, the effect of thermal treatment on the adsorption of Reactive Blue 19 (RB19) dye by red mud was compared with the adsorption capacity of untreated red mud. Thermal treatment of red mud at 500°C results in an increase in adsorption capacity from 357 mg g-1 (untreated red mud) to 416 mg g-1, under acidic conditions. Red mud samples thermally treated at 600°C and 800°C show a reduction in adsorption capacity, however, falling to 337 mg g-1, in acid medium. The change in the maximum adsorption capacity of red mud to RB19 following thermal treatment is associated with specific surface area. Red mud subjected to 500°C can be used for the treatment of water and wastewaters with a higher efficiency than untreated red mud, thus finding possible application in the textile industry.

Enhanced sludge dewaterability by Fe-rich biochar activating hydrogen peroxide: Co-hydrothermal red mud and reed straw

This study proposed Fe-rich biochar (RMRS-BC) produced by the co-hydrothermal treatment of red mud and reed straw, industrial waste and agricultural waste, as a novel sludge conditioner. It had been proven that heterogeneous and homogeneous Fenton reactions occurred during the sludge conditioning process, in which RMRS-BC activated H2O2 to improve sludge dewaterability. Results demonstrated that the optimal condition was 7.5 wt% dry solids (DS) of RMRS-BC at a mass ratio of 1:1 combined with H2O2. The corresponding water content of sludge cakes and the capillary suction time reduction efficiency were 57.88 wt% and 69.76%, respectively. The Fe3O4 supported in the RMRS-BC structure was used as a catalyst to produce heterogeneous reaction, and the Fe2+ leached from the RMRS-BC after acidification happened homogeneous reaction. Double Fenton reaction in sludge conditioning enhanced the production efficiency of ·OH, the sludge flocs were dispersed into smaller particles, more bound water from the extracellular polymeric substances (EPS) was released, and sludge dewaterability performance was improved. Another main mechanism for enhancing dewaterability was to use RMRS-BC as a skeleton builder to reduce the compressibility of sludge cakes and facilitated free water to flow out. In summary, the Fenton oxidation method activated by RMRS-BC is feasible in improving sludge dewatering.

High purity scandium extraction from red mud by novel simple technology

Storage of red mud – bauxite processing waste – leads to serious environmental problems due to its high alkalinity and particle dispersity. Full or partial utilization or recycling of red mud could reduce the harmful effect on the environment. Scandium is the most valuable ingredient of red mud, yet it's extraction is poorly commercialized due to its high cost. The new efficient extraction technologies promise an ensured supply of scandium and a significant drop in cost. Here, scandium concentrate, extracted from leachate after carbonate treatment of red mud, was subjected to sulfatisation by H2SO4 to separate silica from water-soluble sulfates. To recover and selectively separate scandium from other impurity metals, the crystallization of two complex scandium and ammonium sulfates – NH4Sc(SO4)2 and (NH4)3Sc(SO4)3 – is proposed. The solubilities of these sulfatoscandiates in water, established by isothermal method, are 33.4 and 72.4 g/L, respectively. For the less soluble NH4Sc(SO4)2 a further considerable reduction of solubility has been observed in H2SO4 solutions of concentration above 3.5 М in the presence of 0.5 М NH4Cl at 20 ± 1 °C. More than 99% of scandium in the form of micron-sized NH4Sc(SO4)2 crystals has been recovered from a multicomponent liquid at 5–6 М H2SO4 and 0.5 М NH4Cl. The product contains extremely low levels of impurities. The precipitation of NH4Sc(SO4)2 offers a much higher selectivity in separation of Sc from the other main constituents, as demonstrated by the large separation coefficients between scandium and other metals βSc/M (e.g., for the couple with aluminum βSc/Al = 4280). The recrystallization product after calcination at 1000°С contains 99% Sc2O3.

The neutralization and recycling of red mud – a review

Red mud (bauxite residue) is a highly alkaline solid waste of alumina production. The amount of red mud is huge while its alkalinity hinders the application in construction industries. Up to now, the most common treatment of red mud is disposed in man-made dams. However, the long-term storage of large-amount red mud pollutes environment and underground water, threats human life and leads to a huge waste of valuable metals resources. Recently, researchers have proposed various strategies to solve the red mud problems. In this review, the neutralization and recycling status of red mud have been systematically illustrated, their advantages and disadvantages are also discussed in detail in terms of environmental and economic benefits. Moreover, the recommendation of red mud treatment in the future is suggested, the application in road base material is highly valued because of the huge consumption.

Advanced lead free, multi-constituent-based composite materials for shielding against diagnostic X-rays

ABSTRACT We report a novel chemical method for the development of advanced lead free, multi-constituent-based composite materials for shielding against diagnostic X-rays by exploring the multi-elemental, multi-componential phases inherently present in red mud and brine sludge. The chemical treatment of red mud with citric acid and further using brine sludge leads to formation of two types of powders, tailored radiation shielding powder & advance tailored radiation shielding powder. The synthesised shielding powders were characterised by using various techniques like FTIR, TGA, DSC, FESEM, XRD and EDS. The synthesized powders have high-density, multi-layered, multicrystaland multi-shielding phases necessary for imparting radiation shielding properties. The shielding at different energies of X-ray photons for developed advanced radiation shielding panels and tiles has been calculated. The developed advanced lead free, multiconstituent-based composite materials can be used in broad application spectrum ranging from diagnostic X-ray and CT scanner room to other strategic radiation shielding installation.

Preparation of activated red mud and its application for removal of hydrogen sulfide in air

Red mud is a highly alkaline solid waste from the Bayer process for aluminum production. Red mud reservoirs are usually considered as a potential environmental risk. The treatment of red mud is costly due to the lack of an effective and economical treatment technology. On the other hand, the main components of red mud are Fe2O3, Al2O3, SiO2, and Na2O, which could be employed as a promising precursor for the preparation of various nanomaterials. In this study, we prepared activated red mud by thermal and acid treatment method and applied it for adsorption of H2S in air. The red mud was activated under different temperatures (i.e., 200, 400, 600, and 800 oC for 4 h), types of acid (i.e., H2SO4 and HCl), and acid concentrations (i.e., 0.5, 1.5, and 2.5 M). The produced materials were then applied for H2S removal in air with concentration of 90 – 110 mg/m3 using a fix-bed adsorption column test. Results showed that red mud activated at 800 oC and with 1.5 M H2SO4 solution had the highest adsorption capacity of 29.38 mg/g with an average removal efficiency of 80.2%. The effects of gas flow rate and initial H2S concentration were also investigated, and the highest removal capacity was achieved at an inlet concentration of 100 mg/m3 and flow rate of 1 L/min. Both Langmuir and Freundlich adsorption isotherms were employed for modelling the H2S adsorption by this material and the experimental result was more fitted with the Langmuir isotherm. The thermal desorption and recyclability test were also conducted for evaluating the practical application of activated red mud material and 200 oC was the suggested desorption temperature with 81.7% adsorption capacity recovery.

The removal of phosphate by thermally treated red mud from water: The effect of surface chemistry on phosphate immobilization

This study investigated thermal treatment of red mud (RM) and its effect on phase composition, surface property, and sorption capacity exemplified by phosphate. Dehydration (∼600 °C), decomposition of carbonate minerals (700 °C–800 °C), and silicate/aluminate formation (900 °C–1000 °C) occurred upon thermal treatment of RM. Grain growth and vitrification that rendered initial morphology changes and decreased the specific surface area of RM from 26.5 to 4.1 m2/g when treated from 600 to 1000 °C, respectively. Surface acidity, i.e., intrinsic acidity constant and surface acidity density, decreased as well after thermal treatment at 600 °C due to burnouts of organics then increased upon further elevated-temperature treatment because of phase transformation. Thermal activation enhanced phosphate adsorption density (μmol/m2). Multilayer sorption aided by leached metal ions was responsible for phosphate immobilization.

Preparation of Fe–Ni Alloy Containing Low Cr and Ti from Red Mud Through Molten Salt Electrolysis

The paper reports the preparation of iron–nickel alloy with low chromium (Cr) and titanium (Ti) from pre-treated red mud through molten salt electrolysis. The pre-treatment of red mud involves the heat treatment of red mud with Na2CO3 in a graphite crucible at a temperature of 1000 °C for 1 h followed by water leaching and drying. The electrolysis of pre-treated red mud is carried out in a molten CaCl2 bath at a temperature of 1000 °C taking heat-treated red mud as cathode and graphite as anode. The electrolysis of pre-treated red mud is carried out at a constant cell voltage of 3 V for 1 h in a molten CaCl2 bath at a temperature of 1000 °C to produce the iron–nickel alloy containing low chromium and titanium. The partially metalized phases (α-Fe, CrTi and NiTi) present in the pre-treated red mud accelerate the cathodic reduction during molten salt electrolysis to produce the said alloy and ultimately decrease the time period of electrolysis.