Presence Of Red Mud Research Articles

Feasibility of using red mud as bed material for treating N2O in fluidized bed combustion

Red mud, a type of industrial waste, currently can’t be utilized effectively, and there are no efficient methods for controlling N2O emissions in circulating fluidized bed (CFB) boilers. Based on characteristics of N2O and the components of the red mud, the red mud was used in this study as bed materials of fluidized bed to treat N2O produced by coal combustion. The decomposition effect of red mud on N2O under various operating conditions during the coal combustion process was quantified in a bubbling fluidized bed, and the decomposition of N2O and NO after the flue gas passed through the bed material was investigated. In a variety of operational conditions, the presence of red mud has been observed to exert a pronounced inhibitory effect on the formation of N2O, while concurrently exhibiting the capacity to diminish the nitrogen conversion rate of N2O to varying degrees. Comparative analysis of N2O and NO emissions from char and coal revealed different levels of reduction, with the combination of CO and red mud being the most effective method. Red mud demonstrated superior N2O removal capabilities, while CO was more effective for NO removal. The issue of increasing NO can be resolved by balancing the iron-aluminum ratio of red mud, allowing the flue gas to pass through the red mud in the CFB’s low-temperature zone, and focusing on N2O removal in the furnace.

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.

Unraveling electrochemical performance of a 10CrMo steel in alkaline concrete pore solutions with red mud and ground granulated blast-furnace slag

Effect of red mud (RM) and ground granulated blast-furnace slag (GGBS) on passivation and chloride-induced corrosion of a 10CrMo steel in alkaline concrete pore solutions was studied using electrochemical measurements. Also, passive films of 10CrMo steel formed in different alkaline solutions were investigated by XPS and AFM. The addition of RM and GGBS might not change the major components of passive films, yet the redox processes and electronic properties of the passivated steel were significantly affected, which could be detrimental to its passivity. However, enhanced pitting corrosion resistance was highlighted for 10CrMo steel in the presence of RM and GGBS.

Mechanistic insight into the adsorption of mercury (II) on the surface of red mud supported nanoscale zero-valent iron composite

Recently, nanoscale zero-valent iron (nZVI) particles have been efficiently used in the remediation of many heavy metals, yet potential agglomeration and loss of nZVI remain a critical area of research. In this study, we used red mud as a stable supporting medium to develop red mud modified nZVI to form (RM-nZVI) composite. We assessed its sorptive/reductive removal of mercury (Hg2+) from aqueous solutions. The RM-nZVI was synthesized through the reduction of ferric iron by sodium borohydride (NaBH4) in the presence of red mud. Morphological characterization of RM-nZVI confirmed its diffusion state with lesser aggregation. The RM-nZVI has the BET surface area, pore diameter, and pore volume as 111.59 m2g−1, 3.82 nm, and 0.49 cm3g−1, respectively. Adsorption of mercury (Hg2+) by RM-nZVI exhibits pH-dependent behavior with increased removal of Hg2+ with the increase in pH up to 5, and the removal rate decreased gradually as the pH increased from 5 to 10. Extensive characterization of RM-nZVI corroborated the evidence that the removal of Hg2+ was initially by rapid physical adsorption, followed by a reduction of Hg2+ to Hg0. The adsorption data were best fitted with Langmuir isotherm with R2 (correlation coefficient) > 0.99 with high uptake capacity of 94.58 (mg g−1). The novel RM-nZVI composite with enhanced sorptive and reductive capacity is an ideal alternative for removing Hg2+ from contaminated water.

Fly ash red mud geopolymer with improved mechanical strength

World produces annually multimillion of tones of fly ash (FA) and red mud (RM) as industrial wastes. There is a dire need to develop a process that can potentially use these wastes as large stockpiling of these materials can lead a potential hazard to the common people. The FA is rich in silica and alumina, two major ingredients of the aluminosilicate network containing inorganic polymer called geopolymer. The present work demonstrates the geopolymer prepared from fly ash and red mud (FA-RM-geopolymer) with significant high strength of 65 MPa under optimized experimental conditions. Geopolymers were synthesized from the raw material under ambient condition of 25 °C with 28 day of curing. It was observed that after 28 days of curing maximum compressive strength of 65 MPa was achieved in presence of 10 wt percent of red mud. While fly ash based geopolymer (FA-geopolymer) showed 53 MPa compressive strength under similar experimental conditions. X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectroscopy (XRD), particle size analysis and FE-SEM were used to study the structural properties of raw material and the geopolymer. XPS studies revealed that the iron of the RM does not take part in the geopolymerization, as no change was observed for the Fe2p 3/2 peak of the RM and FA-RM-geopolymer. However significant change was observed for the Al2p 3/2 XPS peak. Further it was observed that the presence of RM resulted in increases Si/Al and Na/Al molar ratio compared to FA-geopolymer. SEM studies confirmed the formation of high dense structure for the FA-RM-geopolymer suggesting RM provides aluminum to participate in the geopolymerization and simultaneously acts as filler thereby leads to enhanced and active geopolymerization process on blending of fly ash with red mud. • Fly ash with red mud geopolymer has been studied by XPS, XRD and SEM. • Presence of 10 wt % red mud results in high compressive strength. • XPS studies revealed increase in Si/Al and Na/Al molar ratio in presence of red mud. • Red mud leads to enhanced geopolymerization process.

Mechanical strength analysis of fly-ash based concrete in presence of red mud

Sustainable construction practices require transformation in construction industry aiming at reduction of environmental pollution along with enhancement of performance and durability of cementitious structures. Application of pozzolanic materials have been proven promising in this concern as auxiliary cementitious materials for partially replacing cement in mortar and concrete with a positive impact on strength and microstructure of cement matrix. Use of industrial wastes with pozzolanic properties in this category is exceedingly required in order to abate the issue of environmental pollution. Fly ash (FA) and red mud (RM) are the two industrial wastes that pose an issue of safe disposal. Although, FA is already in use as a pozzolanic material, yet not much work is available on the use of RM in concrete. This study examines suitability of RM for use in presence of FA for strength enhancement of concrete. In this analysis, FA was utilized in a dosage of 0–24% by weight of cement while RM was varied from 0 to 24% in presence of 8% FA for partial replacement of cement in concrete. Mechanical strength analysis of concrete specimens was performed and compared with control specimen. The results show that optimized use of FA leads to strength enhancement and the effect is more pronounced in presence of optimized dosage of RM. Thus, RM in presence of FA can be used as a strength modifier and can decrease the cement demand leading to sustainable construction practices.

Pyrolysis of chlorine contaminated municipal plastic waste: In-situ upgrading of pyrolysis oils by Ni/ZSM-5, Ni/SAPO-11, red mud and Ca(OH)2 containing catalysts

This work is focussing to the thermo-catalytic batch pyrolysis of contaminated real municipal plastic waste using different catalyst mixtures in their different ratios: Ni/ZSM-5, red mud, Ca(OH)2 and Ni/SAPO-11, red mud, Ca(OH)2. The effect of the catalysts to the pyrolysis oil properties and the in-situ upgrading (especially the storage, transportation and corrosion stability) of pyrolysis oil was investigated. High concentration of Ni/ZSM-5 and Ni/SAPO-11 zeolites in catalyst mixtures can increase the yield of gases and pyrolysis oil, the concentration of aromatics or the hydrogen content in gases; however the presence of red mud in higher content can further increase the hydrogen concentration. ZSM-5 based catalysts showed higher efficiency in aromatization reactions. An accelerated aging test at 80 °C till 1 week was performed to investigate the storage and transportation stability of pyrolysis oils. Only slight increase was found in the density and viscosity, on the other hand there was a bit greater increase using SAPO-11 based catalysts than ZSM-5. The change in the olefin content was followed via bromine number and FTIR spectra of pyrolysis oil, which resulted ∼3% and ∼4% decreasing using Ni/ZSM-5 and Ni/SAPO-11 containing catalyst mixtures. Regarding acidic components, they significantly increased by aging time, while the high red mud and/or Ca(OH)2 in catalyst mixtures had notable benefit, because they can drastically decrease the concentration of chlorinated compounds, which led to less weight loss during corrosion test using copper plate till 60 days at 20 °C.

Effects of exhaust gas recirculation on emission characteristics of Mahua (Madhuca Indica) biodiesel using red mud as catalyst

ABSTRACTIn this work, Mahua vegetable oil in the presence of red mud as a catalyst for the preparation of bio-diesel is investigated. The cracking process is carried out in a reactor chamber maintained at a temperature of 65°C in order to obtain biodiesel. The product obtained after the cracking process is evaluated for physio-chemical properties such as flash point, fire point, calorific value, and specific gravity, and the obtained values were compared with neat diesel. The biodiesel is then blended with diesel fuel on volume basis such as B25, B50, B75, and B100. The experiment was carried out in a single cylinder, water cooled DI diesel engine to study the emission characteristics. The results revealed that the use of red mud as a catalyst increases the fuel property and reduces the effect of environmental pollution. This method of biodiesel preparation is very much cost effective and the use of red mud as a catalyst further decreases the cost of biodiesel compared to neat diesel.

Production of Pyrolysis Oil with Low Bromine and Antimony Contents from Plastic Material Containing Brominated Flame Retardants and Antimony Trioxide

Thermal degradation of high impact polystyrene (HIPS) containing brominated flame retardants and antimony trioxide (Sb2O3) was conducted at different temperatures with the presence of various additives (red mud, limestone and natural zeolite) in a fixed-bed reactor. The effect of the pyrolysis temperature on the product yield and the bromine content in the oil product was investigated. It was found that the maximum oil yield (84.38 wt.%) was obtained at the pyrolysis temperature of 500 ?. The pyrolysis temperature had no significant impact on the bromine reduction in the oil products. The bromine in the flame retardant was mainly transferred into the oil products, where the bromine content was in the range of 7.96-8.56 wt.%. With the aim of removing bromine and antimony from the oils, three additives (red mud, limestone and natural zeolite) was used to investigate the influence on the product yield and composition, especially on the bromine and antimony removal ability from the oil products. In this study, it was found that all of the additives could significantly lower the bromine and antimony content in the oils and the red mud was the most effective. The presence of red mud could reduce the bromine and antimony content from 8.21 and 1.84 wt.% when no additive was employed to 0.84 and 0.35 wt.%, respectively. In addition, the distribution and fate of bromine and antimony in the residues were also studied by the SEM-EDX and XRD analysis in detail.

Preparation of sodium aluminate from the leach liquor of diasporic bauxite in concentrated NaOH solution

A new process to produce monosodium aluminate hydrates (MAH) by fast crystallization from the leach liquor of a diasporic bauxite in concentrated NaOH solution is presented. The crystallization of MAH was carried out easily compared to the precipitation of gibbsite and the effect of agitation, initial concentration of sodium aluminate, seed amount and the presence of red mud were systematically studied in a batch crystallizer. The apparent kinetics of crystallization followed a second order rate law with an apparent activation energy for MAH crystallization of 38.0 kJ/mol which implies a surface-diffusion controlled mechanism. X-Ray diffraction and scanning electron microscopy identified the structure of MAH as Na 2O·Al 2O 3·2.5H 2O with a flake crystal morphology. The molar ratio α of Na 2O to Al 2O 3 in the MAH products was < 1.2 after a simple wash by dilute sodium aluminate.

Hydrogen production from methane in the presence of red mud –making mud magnetic

Red mud, a waste product of the aluminium industry, has been shown to possess significant activity for the decomposition of methane, a by-product of oil refining and landfill, generating hydrogen and a carbon containing magnetic material. It is envisaged that the latter material could be of interest in terms of downstream purification processes and that its magnetic properties may facilitate separation/handling. In this way, two valuable end products can be generated from two waste products.

Preparation and Characterization of Poly(2-halogenaniline) Composites with Al2O3, SiO2, and Red Mud

In-situ polymerizations were carried out in the presence of Al2O3, SiO2, and red mud (RM) (host materials) to synthesize poly(2-halogenaniline)/Al2O3, poly(2-halogenaniline)/SiO2, and poly (2-halogenaniline)/red mud composites. The 2-halogenanilines were polymerized without guest materials under the same conditions to compare the properties of the product with those of the composites. Homopolymers and composites were characterized by FT-IR and UV-vis spectroscopies, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction spectroscopy, magnetic susceptibility, and conductivity measurements. The inclusion of either of those monomer units in the resultant composites was confirmed by FT-IR analysis. The properties of the composites changed depending on the type of host materials. Thermal stability of materials follows the trend according to their residual amounts at 800°C of Al2O3 > RM > SiO2. The enhancements in thermal behaviors of poly(2-halogenanilines) were studied in the presence of host materials (RM, SiO2, Al2O3). SEM revealed interesting morphological features of the composites prepared using various inorganic materials and monomers. The analyses indicated typical structural differences between RM, SiO2, Al2O3, and poly(2-halogenanilines). Magnetic susceptibility measurements revealed that the composites with SiO2 and Al2O3 have diamagnetic properties, whereas composites in the presence of RM show paramagnetic conductivity mechanism. The conductivities of composites synthesized using three different materials were measured by a four-probe technique. The presence of Al2O3, SiO2, and RM affected the conductivities of pure polymers.

Characterization of the Liquid Phase Obtained by Copyrolysis of Mustafa Kemal Paşa (M.K.P.) Lignite (Turkey) with Low Density Polyethylene

This study describes the detailed hydrocarbon type characterization of the tar (liquid phase) obtained by copyrolysis of Mustafa Kemal Pasa (M.K.P.) lignite (Turkey) and low density polyethylene (LDPE) and by pyrolysis of coal and LDPE individually. Various spectroscopic techniques [gas chromatography−mass spectroscopy (GC-MS), nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC)] are used for characterization, and the effect of the experimental conditions [temperature, lignite:low density polyethylene (LDPE) ratio, and catalyst] on the hydrocarbon distributions is discussed. The results show that the tars obtained by copyrolysis have similar properties with commercial gasoline (especially in the presence of Red mud). Red mud and bentonite used as catalysts make a positive effect on the production of olefins instead aromatics. Polyethylene acts as a hydrogenation medium for the coal product as revealed by FTIR results.

The effect of some fillers on PVC degradation

The HCl scavenging effect of particulate fillers such as Red Mud (RM), CaCO 3 and dolomite on the thermal degradation of PVC was investigated by thermogravimetry/mass spectrometry (TG/MS). It was found that, in the presence of carbonates, the peak temperature ( T max) of dehydrochlorination was shifted to a higher temperature and the rate of mass loss was decreased, while, in the presence of RM, FeCl 3 was formed and dehydrochlorination of PVC was accelerated, but the second decomposition step of PVC has been retarded. Benzene formation has been hindered by the acid scavenger additives and retarded by RM, evolution of benzene and other aromatics being shifted to higher temperatures.

Use of red mud for toxic metals removal: The case of nickel

AbstractThe presence of red mud was found to remove effectively nickel ions from dilute aqueous solutions (50 mg dm−3). Red mud, being an industrial solid by‐product/waste from alumina production during bauxite processing, was found to act simultaneously as an alkalinity regulator, causing precipitation of nickel as the insoluble hydroxide, as an adsorbent of the formed nickel hydroxide and as a flocculant of the resultant fine particulate matter. Sedimentation was subsequently considered as a possible solid/liquid separation technique. Various parameters, such as dispersion pH, red mud and nickel concentrations and ζ‐potential, were examined and promising results were obtained.

Role of Iron in Hydrogen Sulphide Removal from Hot Gas

Yields of SO2 formed during H2S removal from N2 + H2S mixture at 800°C in the presence of Fe2O3, Mn-nodule and red mud have been determined. The largest yields were observed for Fe2O3 followed by Mn-nodule, whereas no SO2 was detected in the presence of red mud. A mechanism for H2S reaction with Fe oxides has been proposed involving the use of the component distribution in the clean gas as well as the Fe sulphides formed during adsorption. X-ray diffraction and Mossbauer spectroscopy have been used to determine the forms of Fe in the solids at the end of adsorption. FeS was the main sulphide which was always accompanied by FeS2.