Red Mud Catalyst Research Articles

TG-FTIR-Py-GCMS analysis and catalytic pyrolysis mechanism of textile waste by red mud catalyst for liquid fuel production

The substantial generation of textile waste (TW) and red mud (RM) has resulted in significant resource wastage and environmental challenges. Co-utilization technology of solid waste is an effective approach to improve waste utilization efficiency. In this study, RM catalytic pyrolysis experiments of TW were conducted using TG-FTIR and Py-GC–MS for liquid fuel production, and TW and RM were recycled simultaneously. At the optimal experimental conditions (temperature of 600 °C and feed catalyst ratio of 2:1), the tar yield and higher heating value (HHV) of TW pyrolysis catalyzed by RM were 73.43 wt% and 32.34 kJ/g, respectively. Additionally, experiments on the pyrolysis of various TW types revealed that LDPE and PP are suitable for tar production, while cotton, nylon, and PET are more suitable as feedstock for syngas production. The RM catalytic pyrolysis mechanism of textile waste is that Fe2O3 in RM exhibits significant catalytic activity in enhancing tar and syngas yields. However, during the catalytic process, Fe2O3 undergoes reduction to Fe3O4, resulting in diminished catalytic performance of the RM. After five cycles of use, the RM essentially lost its catalytic activity due to the accumulation of char and tar. All experimental findings of this study could offer an effective guideline for TW recycle and promoting RM utilization toward the waste-to-energy circular economy.

One-Step Benzene Hydroxylation with Copper Oxide Supported on Activated Red Mud Catalyst

One-Step Benzene Hydroxylation with Copper Oxide Supported on Activated Red Mud Catalyst

Production of low-sulfur fuels from catalytic pyrolysis of waste tires using formulated red mud catalyst

Waste tires (WT) are produced in millions of tons per annum and their safe disposal is always a major environmental challenge because of fire hazards and the increasing cost of landfills. WT has high organic matter content that can be converted into fuels and chemicals if suitable technologies can be developed. Herein we report the in situ catalytic pyrolysis of WT using formulated red mud catalyst to produce low sulfur fuel that can be fractionated or can be used without fractionation. The in situ catalytic pyrolysis was conducted at 450–550 °C using formulated red mud catalyst. The yield of pyrolysis liquids ranged from 35 to 40 wt%. The liquid was very rich in limonene and long chain aliphatic hydrocarbons. The catalyst was effective in removing the sulfur compounds in the oil through reactive adsorption desulfurization mechanism. The sulfur species reacted with hematite, calcite, sodium hydroxide, and zinc oxide to form sulfides and were retained in the catalyst. The minimum sulfur content of the catalytic pyrolysis oil was 0.38 wt%. After catalyst regeneration in air through combustion, the catalyst activity was restored, and the catalyst was reused.

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.

Modification of red mud catalyst using oxalic acid-assisted UV treatment for toluene removal

An innovative simplified modification method for red mud had been proposed, which enabled its utilization as an active Fe2O3-rich component for catalytic oxidation of toluene. The Box-Behnken design, based on Response Surface Methodology (RSM), was employed to optimize the modification of bauxite residue using oxalic acid combined with UV irradiation. Based on the experimental conditions, the optimal conditions for three independent parameters were determined: acid leaching time (2 hours), UV irradiation time (1 hour), and acid dosage (150 ml),which was in order to enhance the maximum catalytic efficiency of toluene at 300 °C. Under the optimal preparation conditions provided by the Box-Behnken design, the catalytic efficiency of toluene at 300°C could reach 99.2%. In comparison to the acid-modified mud (MRM) and untreated bauxite residue (RM), the aluminum refinery residue modified with oxalic acid-assisted UV irradiation (MRM-UV) exhibited the formation of oxalate sub-iron precipitates, resulting in significantly lower catalytic temperatures (238°C). Furthermore, through XRF, XRD, XPS, O2-TPD, and H2-TPD analysis, it was discovered that a large amount of iron oxide and calcium oxide formed CaO+Fe2O3→Ca2Fe2O5, strengthening the interaction between iron and calcium, augmenting the migration rate of lattice oxygen from the bulk phase to the surface. Consequently, T50 were reduced by 20.9% and 31.8% when compared to MRM and RM. Moreover, the CO2 selectivity of MRM-UV increased from 8.6% to 70.5% compared to RM at 300°C. Using in situ DRIFTS, the reaction pathway of toluene on MRM-UV was identified as benzyl alcohol → benzaldehyde or benzoyl → benzoate→maleic anhydride→CO2 and H2O. The process refinement reduced VOCs emissions and promoted sustainable waste management by combining oxalic acid with catalytically active red mud.

Facile production of ethyl furfuryl ether via reductive etherification of furfural over Rh nanoparticles supported red mud as a catalyst

Reducing reliance on fossil fuels and mitigating industrial waste are two strategies for clean environmental management. An active research topic within this framework is to convert abundant bio-derived compounds, like furfural (FF), into a petroleum blend by employing industrial waste, like red mud (RM), as catalyst support. Here, we demonstrate that furfural can be chemoselectively converted in a single step into ethyl furfuryl ethers (EFE), which significantly enhance the blended petroleum's octane number. This is achieved in the presence of a recyclable Rh-impregnated RM catalyst. In this context, a range of valuable metals (M = Rh, Ir, and Ru) are impregnated into the RM (M@RM) and extensively characterized by SEM, EDS, XRD, FT-IR, TEM, and XPS. The 1% Rh@RM composite,calcined at 400 °C (1% Rh@RM-400), produced 75 % EFE selectivity with the >99 % conversion of furfural. The prepared catalyst retains its stability for the multiple cycles of the furfural hydrogenation reactions.

Efficient removal of 17α-ethinylestradiol by algae-based red mud catalyst activated persulfate: Removal mechanism and defect of quenching

The synthesis and optimization of carbon-based materials, derived from various solid waste sources to activate peroxydisulfate (PDS), offer a practical approach that addresses both the recycling of solid waste resources and the removal of recalcitrant organic pollutants. In this study, stacked algae sludge and discarded red mud solid waste were repurposed to synthesize an algae-based red mud catalyst (AR-BC) using the carbon-thermal reduction technique. The obtained AR-BC catalyst exhibited efficient adsorption and degradation capabilities for 17α-ethinylestradiol (EE2). The results showed that AR-BC can adsorb 42.67 % of EE2 at equilibrium, with a maximum capacity of 8.0 mg/g. After the activation of PDS by the AR-BC catalyst, it was observed that EE2 was completely degraded within 20 min. The superior activation ability is mainly attributed to the presence of Fe3O4 and oxygen-containing functional groups in AR-BC. Both free radicals and non-free radicals coexisted in the AR-BC/PDS system, with the former predominantly influencing the EE2 degradation process. And hydroxyl radical was identified as the primary reactive oxygen species. Moreover, AR-BC exhibited robust adaptability and reusability in real water for efficient adsorption and degradation of EE2. This study presents a viable solution by seamlessly integrating resource recycling with pollutant removal, offering an innovation approach.

Promotion of Cu/Ce supported red mud for NO removal from low and medium temperature flue gas

Red mud is a solid waste in aluminum industry and has been proven to be an efficient alternative to NOx selective catalytic reduction (SCR) catalysts. Acid washing treatment to red mud can improve its alkalinity and surface properties, and increase the conversion rate of NOx. In this paper, Cu, Ce, and Cu/Ce was supported on acid washed red mud and NOx catalytic conversion performance on metal modified red mud catalysts was studied. The research results indicate that Cu+ and Cu2+ in the Cu supported catalyst effectively promote NO conversion rate of red mud in low-temperature (200–300 °C) flue gas, reaching a maximum of 90.7%; Ce3+ and Ce4+ in Ce supported catalysts effectively promote the NO conversion rate of red mud in flue gas at 200–400 °C, reaching a maximum of 94.0%; Cu/Ce supporting exhibits better NO conversion rate than single metal supported catalysts at low-temperatures, the optimal Cu:Ce ratio for supporting is 1:1; and also exhibits better NO conversion rate than Cu supported catalysts at high-temperature (300–400 °C), reaching a maximum of 95.5%. The reason may be that under the synergistic effect of Cu/Ce, ACRM-Cu1Ce1 has stronger low-temperature redox ability, higher weak acidic peaks, higher average oxidation state of Fe ions, and higher Cu+ content.

Hydrolysis of HFC-134a using a red mud catalyst to reuse an industrial waste

Red mud obtained from industrial waste generated during the Bayer process was evaluated as a catalyst for the decomposition of hydrofluorocarbon-134a (HFC-134a), a greenhouse gas. The durability of the catalyst was evaluated through continuous operation for 66 h at 650 °C. The conversion of HFC-134a increased concurrently during the stability test, reaching ∼ 99 % after 50 h. After long-term testing, HFC-134a conversion over the red mud catalyst was evaluated as a function of temperature; an increase in the catalytic activity was observed over all temperature ranges. X-ray diffraction analysis revealed that tricalcium aluminate and gehlenite were formed during the long-term test, and the increase in the catalytic activity of the red mud could be attributed to the formation of a crystalline structure. Scanning electron microscopy/energy-disperse X-ray spectroscopy analysis confirmed that AlF3 and carbon were not generated during the durability tests with high HFC-134a decomposition yield. Based on the HFC-134a decomposition tests and catalyst analysis, we conclude that the red mud catalyst has good catalytic activity and durability when used in HFC-134a decomposition.

Study on the Degradation Effect of Tetracycline Using a Co-Catalyst Loaded on Red Mud

Red mud was modified by impregnation with Co element loading. The Co-RM catalyst was characterized using scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray fluorescence (XRF), and UV full-band scanning. The results showed that the modified Co-RM catalyst successfully loaded the Co element and formed an irregular pore structure on the surface, thereby increasing the number of active sites of the red mud catalyst and effectively improving the degradation efficiency of tetracycline. Under the optimal conditions of a catalyst dosage of 0.3 g/L, a persulfate dosage of 3 g/L, a reaction temperature of 50 °C, and a pH value of 7, a removal rate of 50 mg/L of tetracycline can be achieved: 89.5% after 90 min. The effects of common anions and humic acids in water, as well as radical quenchers (anhydrous ethanol and tert-butanol), on the degradation of tetracycline were investigated. The results showed that Cl−, CO32−, HCO3−, H2PO4−, NO32−, HPO42−, and humic acids showed inhibitory effects on the degradation of tetracycline, while SO42− showed a promoting effect on the degradation of tetracycline. The free radical quenching experiment showed that the most important free radicals that can degrade tetracycline in the system are sulfate radicals.

Efficient activation of peroxydisulfate by modified red mud biochar derived from waste corn straw for levofloxacin degradation: Efficiencies and mechanisms

As using iron-based materials and biomass to prepare effective catalyst has emerged as a hit trend in persulfate-based advanced oxidation processes (PS-AOPs), the problems associated with excessive chemical consumption, costly expenses, and complex synthetic processes have become more urgent to be addressed. Therefore, by using red mud (RM) and corn straw (CS), a modified red mud biochar catalyst (MRBC) was synthesized through acid pretreatment and pyrolysis (700 °C). MRBC presented excellently in peroxydisulfate (PDS) activation to degrade levofloxacin (LFX). Under the experimental setup involving 8 mM PDS, 10 mg L−1 LFX, and 1.6 g L−1 MRBC, 88.59% of LFX was effectively eliminated within 30 min with an exceedingly low Fe leaching rate of 0.049 mg L−1. Furthermore, even after four cycles of reuse, it was able to sustain a remarkable 61.63% efficiency in LFX degradation. The characterization of catalysts demonstrated the synergistic effect of RM and biomass could be responsible for the excellent catalytic properties of MRBC. The results of quenching experiment and the presence of DMPOX in EPR demonstrated radical pathway mainly contributed to the LFX degradation in MRBC/PDS system. Overall, PDS was activated by the active sites of MRBC such as Fe (II) and persistent free radicals (PFRs) to generate a large amount of SO4•− and •OH to remove LFX. This work investigated the synergy of RM and biomass in catalyst preparation, deepened the insights into the application of RM catalysts in PS-AOPs to degrade antibiotic, and contributed greatly to the recovery of waste resources.

Catalytic Co-Pyrolysis of Mesua ferrea L. De-Oiled Cake and Garlic Husk in the Presence of Red-Mud-Based Catalysts

Utilizing lignocellulosic biomass as a renewable energy source for the production of sustainable fuel is of paramount importance. This study focuses on the catalytic co-pyrolysis of Mesua ferrea L. de-oiled cake (MDC) and Garlic husk (GH) as potential feedstocks for bio-fuel production. The pyrolysis experiments were conducted using a semi-batch reactor under inert conditions at temperatures of 500, 550, and 600 °C, with a heating rate of 10 °C min−1, a particle size below 1 mm, and an inert gas flow rate of 80 mL min−1. The findings reveal that temperature significantly influences the yield of pyrolytic products. However, GC-MS analysis detected higher oxygenated compounds in the bio-oil, negatively impacting its heating value. To improve fuel quality, co-pyrolysis with and without a catalyst for a feedstock ratio of 1:1 w/w was performed. Red mud, an alkaline waste mainly composed of Fe2O3, Al2O3, and SiO2, is a hazardous environmental concern from aluminum production and is used as a catalyst. The red-mud catalysts reduced oxygen concentration and increased carbon content, acidity, and heating value in the pyrolytic oil. GC-MS analysis of the bio-oil confirmed that using catalysts combined with MDC and GH significantly decreased the concentration of acidic and aromatic compounds, thereby improving the pyrolytic oil’s higher heating value (HHV).

Evaluating compost for hydrogen and methane rich gas production via supercritical water gasification

The compost produced from organic wastes (MSW, city market’s wastes and wood dust) was selected to be processed via supercritical water gasification (SCWG) in order to produce gas product consisting of hydrogen and methane mainly. The effects of parameters such as temperature, reaction time and KOH as an additive were determined and around 55 vol.% of H2 and CH4 in the gas product was found after 30 min reaction time together with KOH, at 500 oC. The red mud catalysts did not improve the gasification yields even though they increased the calorific value of the product gas.

Red mud-based heterogeneous catalyst for hydrothermal resource-based degradation of norfloxacin in pharmaceutical wastewater by hydrogen peroxide

Red mud (RM) was used as a catalyst for the hydrothermal degradation of antibiotics in simulated pharmaceutical wastewater by H2O2 to produce formic acid. Formic acid could be adopted as hydrogen storage, conforming to carbon neutral strategy. When 10 mL norfloxacin (NOR) solution was used at 40 mg/L, the optimal reaction conditions were 0.02 g RM activated at 100 °C, 0.2 mL added H2O2, as well as the reaction time and temperature of 0.5 h and 90 °C, leading to NOR degradation rate of 69.26 % and a formic acid yield of 58.36 % (selectivity: 87.56 %). The RM catalyst presented good activity and stability in reuse. In this study, phase composition and structure of RM catalyst before and after the reaction were comprehensively characterized, and kinetic model was established. Moreover, the key intermediate pathway of NOR degradation was identified by LC-MS. Under the concept of “treating waste with waste”, these results suggested that wastewater-treatment technology of solid waste (Red Mud) was “Fenton-like” catalyst for resource-based degrading high-ecotoxicity antibiotic pollutants in pharmaceutical wastewater. This process could support environmental protection and green development of the pharmaceutical industry, together with hazardous waste-recycling treatment. In short, this research provides a theoretical basis for the subsequent engineering resource treatment of pharmaceutical wastewater.

Red mud catalysts for hydrothermal liquefaction of alkali lignin: Optimization of reaction parameters

The aromatic enrichment structure of lignin shows its great potential for valuable chemicals, which could be a substitution for petrochemical raw materials. However, the selective breaking of its macromolecular structure is a key challenge in lignin valorization. This study examined hydrothermal liquefaction of alkali lignin with Zr, Mo, and Ce-impregnated red mud catalysts to achieve the maximum liquefaction and break down the sub-aromatic units into selective phenolics. 10 wt% Mo and 10 wt% Ce/RM exhibited the effective liquefaction tendency in ethanol solvent. With a C/F ratio of 1:5, the maximum bio-oil yield (81.8 wt%) was obtained with (5 wt%) Mo–Ce/RM catalyst, and maximum conversion (91.6%) was achieved with a 1:2 C/F ratio in 50E: 50W co-solvent. However, the C/F (1: 10) was found to be efficient towards the selective breaking of alkali lignin into guaiacol compounds with 65.4 area% selectivity of vanillin. The FTIR and 1H NMR analysis showed the actual breaking of lignin sub-aromatic structure into monomeric compounds. The results of GPC analysis validate the cleavage of lignin's structure with a significant reduction in the molecular weight of lignin from ∼28400 gm/mol to ∼485 gm/mol. The catalyst was highly recyclable as it maintained remarkable activity up to two successive catalytic cycles.

Modi-Red Mud Loaded CoCatalyst Activated Persulfate Degradation of Ofloxacin

As an abundant potentially dangerous waste, red mud (RM) requires a straightforward method of resource management. In this paper, an RM catalyst loaded with cobalt (Co-RM) was prepared by the coprecipitation method for the efficient activation of persulfate (PS). Its degradation performance and mechanism of ofloxacin (OFL) were investigated. The characterization results of scanning electron microscopy, X-ray diffractometer, and energy dispersive spectrometer showed cobalt was successfully loaded onto the surface of RM, and the catalyst produced could effectively activate PS. Under the conditions of 15 mg/L OFL, 0.4 g/L Co-RM, 4 g/L PDS, 3.0 pH, and 40 °C temperature, the maximum removal rate of OFL by the Co-RM/PDS system was 80.06%. Free radical scavenging experiments confirmed sulfate radicals were the main active substances in the reaction system. The intermediates in OFL degradation were further identified by gas chromatography-mass spectrometry, and a possible degradation pathway was proposed. Finally, the relationship between defluorination rate and time in the Co-RM/PDS degradation OFL system was described by the first-order kinetic equation. This work reports an economical, environmental solution to the use of waste RM and provides a research basis for the further exploration of RM-based catalysts.

Determination of Optimum Conditions for Synthesis of Methyl Ester from Bleached Crude Palm Oil Using Sn-Zeolite and Red Mud Catalysts

Methyl esters synthesis from bleached crude palm oil (BCPO) containing 0.36 and 20.86% of free fatty acids using Sn-zeolite and red mud has been done. This study aims to determine the esterification, transesterification, and transesterification-esterification simultaneous reactions optimum conditions when using Sn-zeolite, red mud, and Sn-zeolite-red mud mixture catalysts. The X-ray diffraction and Fourier transform infrared analysis results show that Sn has been impregnated on zeolite, indicated by cassiterite and Sn-O-Sn vibrational peaks in Sn-zeolite. The main component of red mud is NaCO3, indicated by analcite and carbonate peaks. Thin-layer chromatography results in the transesterification showed that red mud catalyst could totally convert triglycerides from BCPO to methyl ester when 5% catalyst, 3 hours, and CPO:methanol mole ratio 1:20 were used. In esterification, Sn-zeolite can synthesize methyl ester from low-quality CPO when using CPO:methanol mole ratio 1:20 for 3 hours, however, the conversion was not total. In the transesterification-esterification simultaneous, the conversion was also not total which the best reaction conditions at mixing Sn-zeolite:red mud 1.5:1 (w/w), 7% catalyst, and CPO:methanol mole ratio 1:20 for 3 hours. This study shows that esterification and transesterification processes can be carried out simultaneously at a particular mass ratio of Sn-zeolite and red mud.

Enhancing catalytic performance of red mud for palmitic acid hydrodeoxygenation by acid pretreatment-induced structural modification

Red mud (RM) is a metal oxide-enriched solid waste material that was subjected to various acid treatments to assess their effect on catalytic performance for hydrodeoxygenation (HDO). Acid pretreatment induces structural changes in RM, which enhances its stability and catalytic performance for HDO. Among the different acid treatments, acetic acid-treated RM catalyst (Ni/RM-HAC) exhibited superior catalytic performance and stability, yielding 81% cetane selectivity and maintaining efficient conversion for up to 400 h. The acetic acid treatment increased the Fe2O3 content in the catalyst, removed inert components such as Na2O and CaO that block pore channels, and greatly improved specific surface area and pore size. Moreover, the acetic acid treatment increased medium acid sites and oxygen vacancy in the catalyst, enhancing its catalytic performance. The increase of Fe3+ makes the catalyst have better stability. These results are expected to aid in the development of efficient, sustainable, and cost-effective catalysts for the production of the second-generation biodiesel.

Nickel-loaded red mud catalyst for steam gasification of bamboo sawdust to produce hydrogen-rich syngas

Ni/red mud (RM) catalysts were prepared by wet impregnation and used in the catalytic steam gasification of bamboo sawdust (BS) to produce hydrogen-rich syngas. The system was optimized in terms of the amount of added nickel (10%), reaction temperature (800 °C), and catalyst placement (separately behind the BS). The maximum H2 yield was 17.3% higher than that using pure RM catalyst and 43.8% higher than that of BS gasification alone, and the H2/CO ratio in the syngas reached 7.82. This Ni/RM catalyst also retained good activity after six cycles in a double-stage fixed bed reactor. Analysis using X-ray fluorescence, X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, and other methods revealed that the interaction of Ni, Fe, and Mg in Ni/RM produced bimetallic compounds containing active sites, such as NiFe2O4, MgNiO2, and NiO. This explains the good catalytic performance in the tar conversion during the gasification process.

Catalytic pyrolysis of biomass to produce aromatic hydrocarbons in a cascade dual-catalyst system: Design of red mud based catalyst assisted by the analysis of variance

Theoretical and experimental study on the catalytic pyrolysis of rape straw was carried out for the production of aromatic hydrocarbons using the composite red mud (RM) and zeolite HZSM-5 catalyst as the combined catalysts. In the orthogonal tests and analysis of variance (ANOVA), it was originally established that Fe2O3 and CaO acted as the active metal oxides in the red mud, which played the notable role in the production of benzene, toluene and xylene (BTX) as hydrocarbon fuels. Subsequently, the physicochemical property of the Fe2O3 and CaO loaded red mud (Fe2O3-RM and CaO-RM) was investigated and their performance in the catalytic pyrolysis of rape straw combined with HZSM-5 were investigated. It was revealed that the further cracking of the primary pyrolysis gas was promoted with more active Fe2O3 involved, and the heavy component was converted into the light fraction entering HZSM-5 for deoxygenation and aromatization to produce aromatic hydrocarbons. The yield of BTX over Fe2O3-RM was boosted by 10.15 wt% compared with the original red mud catalyst, while that of BTX was further promoted to 11.37 wt% over the composite red mud catalyst with 6% CaO loading. In addition to the strong bond-breaking performance of CaO, calcium carboxylate was easily generated and then decomposed to form CaCO3 and ketones, and then BTX were produced from ketones over HZSM-5 by deoxygenation and aromatization. In this study, the high-performance red mud-based catalysts was designed and utilized in the thermochemical conversion of biomass, providing a potential way for the utilization of two solid wastes, rape straw and red mud to produce hydrocarbon fuels in a high-valued way.