Utilization of iron tailings to prepare high-surface area mesoporous silica materials

An innovative approach to improving lactic acid production from food waste using iron tailings

In this study, the feasibility of promoting the lactic acid (LA) fermentation of food waste (FW) with iron tailings (ITs) addition was explored. The best LA yield was 0.91 g LA/g total sugar when 1 % ITs were added into the system. The mechanisms for promoting LA production were acidification alleviation effects and reduction equivalent supply of ITs. Furthermore, the addition of ITs promoted carbohydrate hydrolysis, and the carbohydrates digestibility reached 88.85 % in the 1 % ITs group. The ITs also affected the microbial communities, Lactococcus gradually replaced Streptococcus as the dominant genus, and results suggested that Lactococcus had a positive correlation with LA production and carbohydrate digestibility. Finally, the complex LAB in FW had significant effects on heavy metal removal from ITs, and the removal efficiency Cr, As, Pb, Cd, and Hg can reach 50.84 %, 26.72 %, 59.65 %, 49.75 % and 78.87 % in the 1 % ITs group, respectively.

Study on the adsorption performance of modified high silica fly ash for methylene blue

Presently, there are several issues associated with solid waste fly ash, such as its accumulation and storage, low comprehensive utilization rate, lack of high-value utilization technology, environmental risk and ecological impact. Thus, based on the high silica content and adsorption characteristics of fly ash, two novel adsorbents, namely mesoporous silica-based material (MSM) and sodium dodecyl sulfate-modified fly ash (SDS-FA), were prepared using an ultrasound-assisted alkali fusion-hydrothermal method and surface modification method. Furthermore, effects of adsorbent dosage, initial pH, contact time, and initial concentration of the solution on the adsorption of the organic pollutant methylene blue (MB) by fly ash, MSM, and SDS-FA were investigated to select the optimal modified high silica fly ash adsorbent. Based on the adsorption isotherms and adsorption kinetics, together with SEM, XRD, FTIR and BET analyses, the adsorption mechanism of MSM for MB was revealed. The results showed that under the conditions of an adsorbent dosage of 2 g L-1, initial pH of 9, contact time of 150 min, and initial concentration of 100 mg L-1, MSM and SDS-FA exhibited removal efficiencies of 92.69% and 84.64% for MB, respectively, which were significantly higher than that of fly ash alone. The adsorption of MB by MSM and SDS-FA followed the Langmuir model and pseudo-second-order kinetics, indicating monolayer adsorption with chemical adsorption as the dominant mechanism. The mechanism of the adsorption of MB by MSM is mainly the result of the synergistic effect among its increased specific surface area, hydrogen bonding, ion exchange, and electrostatic interactions. After five cycles of adsorption-desorption process, the removal efficiency of MSM for MB consistently remained above 80%. Therefore, MSM can serve as a valuable reference for the resource utilization of fly ash and remediation of dye-polluted wastewater.

Iron Tailings as Mineral Fillers and Their Effect on the Fatigue Performance of Asphalt Mastic

Incorporating iron tailings (ITs) into asphalt represents a new method for waste-to-resource conversion. The objective of this study is to evaluate the fatigue performance of ITs as fillers in asphalt mastic and investigate the interaction and interfacial adhesion energy between asphalt and ITs. To achieve that, the particle size distributions of two ITs and limestone filler (LF) were tested through a laser particle size analyzer; the morphology and structure characteristics were obtained by scanning electronic microscopy (SEM), the mineral compositions were conducted through X-ray diffraction (XRD), and the chemical compositions were tested through X-ray Fluorescence Spectrometer (XRF). Furthermore, the fatigue properties of asphalt mastic and the interaction between asphalt binder and mineral fillers (ITs and LFs) were evaluated by Dynamic Shear Rheometer (DSR). The interfacial adhesion energy between ITs and asphalt binder were calculated through molecular dynamics simulation. In the end, the correlation between the test results and the fatigue life is established based on the gray correlation analysis, the environmental and economic benefits of iron tailings asphalt pavement are further evaluated. The results show that the particle size distribution of ITs is concentrated between 30 μm and 150 μm, and the main component is quartz. ITs have rich angularity and a higher interaction ability with asphalt. The adhesion energy of iron tailings filler to asphalt is less than that of limestone. The correlation degree of the interfacial adhesion energy and interaction between asphalt and mineral filler with asphalt mastic fatigue life is close to 0.58. Under the combined action of interaction ability and interfacial adhesion energy, the fatigue life of IT asphalt mastic meets the requirements. ITs as a partial replacement for mineral fillers in asphalt pavement have great environmental and social effectiveness.

Halloysite-derived mesoporous silica with high ionic conductivity improves Li-S battery performance

The slow Li+ transport rate in the thick sulfur cathode of the Li-S battery affects its capacity and cycling performance. Herein, Fe-doped highly ordered mesoporous silica material (Fe-HSBA-15) as a sulfur carrier of the Li-S battery shows high ion conductivity (1.10 mS cm-1) and Li+ transference number (0.77). The Fe-HSBA-15/S cell has an initial capacity of up to 1216.7 mA h g-1 at 0.2C and good stability. Impressively, at a high sulfur load of 4.34 mg cm-2, the Fe-HSBA-15/S cell still maintains an area specific capacity of 4.47 mA h cm-2 after 100 cycles. This is because Fe-HSBA-15 improves the Li+ diffusion behavior through the ordered mesoporous structure. Theoretical calculations also confirmed that the doping of iron enhances the adsorption of polysulfides, reduces the band gap and makes the catalytic activity stronger.

Hydration and properties of hydrogen-based mineral phase transformation iron ore tailings as supplementary cementitious material

Almost all iron ore tailings (IOTs) required activation prior to use as SCMs, which limited their application in building materials. This study investigated HMPT-IOTs and discovered that they possess latent hydraulic and pozzolanic properties. In order to better utilize as SCM, mechanical properties, hydration reactions, hydration products, microstructure, and pores were comprehensively studied through mechanical tests, hydration heat tests, XRD, SEM, TG, and MIP. The results show that when HMPT-IOTs replace cement at 10 wt%, 20 wt% and 30 wt%, the compressive strength at 28 days is 41.9 MPa, 47.9 MPa and 37.5 MPa, respectively. When the substitution amount reaches 30 wt%, it will reduce the cumulative heat of hydration and promote early hydration reactions. The main hydration products are ettringite and Ca(OH)2. As the nucleation site of C-S-H, hydration products are interconnected, making the microstructure denser. At this substitution level, Ca(OH)2 consumption was about 2% at 28 days of age. Simultaneously, the total pore volume was only 0.01 mL/g greater than that of the control group, and the number of micropores and transition pores decreased by approximately 3%.

Sustainable assessment and synergism of ceramic powder and steel slag in iron ore tailings-based concrete

Solid waste management is a critical issue worldwide. Effectively utilizing these solid waste resources presents a viable solution. This study focuses on Iron ore tailings (IOTs), a solid waste generated during iron ore processing, which can be used as supplementary cementitious materials (SCMs) but have low reactivity, hindering their large-scale application in concrete production. To address this, ternary SCMs were prepared using ceramic powder (CP) and steel slag (SS) to enhance the performance of concrete incorporating IOTs. The study found that the synergistic effect of CP and SS significantly improved the compressive strength of concrete, with a notable increase of up to 21% compared to concrete with IOTs alone. Mercury intrusion porosimetry (MIP) and backscattering electron (BSE) analyses revealed that the ternary SCMs significantly optimized the characteristics of the interfacial transition zone (ITZ), which in turn enhanced the compressive properties of the concrete. This contributed to maintaining the structural integrity of the concrete, even amidst variations in the pore structure. Importantly, the incorporation of ternary SCMs led to a 23% reduction in carbon emissions, from 400.01 kg CO2/m3 to 307.48 kg CO2/m3, and elevated eco-strength efficiency from 0.1 to 0.14. The study highlights the role of multi-material synergy in developing composite SCMs systems, fostering the sustainable advancement of green building materials.

Co-utilization of iron ore tailings and coal fly ash for porous ceramsite preparation: Optimization, mechanism, and assessment

Maximizing the utilization of industrial by-products, such as iron ore tailings (IOTs) and coal fly ash (CFA), is crucial toward sustainable development. This study provides a meticulous insight into the optimization, mechanism, and assessment of the co-utilization of IOTs and CFA for the preparation of porous ceramsite. Micro-CT results revealed that the prepared ceramsite exhibited an exceptional porosity, peaking at 56.98%, with a wide range of pore diameters (3.55-959.10 μm) under optimal conditions (IOTs content at 76%, preheating at 550 °C for 15 min, and sintering at 1177 °C for 14 min), while maintaining good mechanical properties (water adsorption of 1.28%, comprehensive strength of 8.75 MPa, apparent density of 1.37 g/cm3, and bulk density of 0.62 g/cm3). The primary parameters affecting the porosity were identified and ranked as follows: sintering temperature > IOTs content > sintering time. The formation and growth of pores could be attributed to the equilibrium relationship between the liquid-phase surface tension and the gas expansion force, accompanied by pore wall thinning and pore merging. Notably, the prepared ceramsite is both ecologically feasible and economically rewarding, boasting a profit margin of 9.47 $/ton. The comprehensive life cycle assessment (LCA) conducted further highlights the potential of its large-scale implementation for promoting sustainable development. This study provides an innovative strategy for the co-utilization of IOTs and CFA, with advantages such as cost-effectiveness, ecological feasibility and scalability of production.

Recent Advances on Porous Siliceous Materials Derived from Waste

In recent years, significant efforts have been made in view of a transition from a linear to a circular economy, where the value of products, materials, resources, and waste is maintained as long as possible in the economy. The re-utilization of industrial and agricultural waste into value-added products, such as nanostructured siliceous materials, has become a challenging topic as an effective strategy in waste management and a sustainable model aimed to limit the use of landfill, conserve natural resources, and reduce the use of harmful substances. In light of these considerations, nanoporous silica has attracted attention in various applications owing to the tunable pore dimensions, high specific surface areas, tailorable structure, and facile post-functionalization. In this review, recent progress on the synthesis of siliceous materials from different types of waste is presented, analyzing the factors influencing the size and morphology of the final product, alongside different synthetic methods used to impart specific porosity. Applications in the fields of wastewater/gas treatment and catalysis are discussed, focusing on process feasibility in large-scale productions.

Eco-friendly strategy for preparation of high-purity silica from high-silica IOTs using S-HGMS coupling with ultrasound-assisted fluorine-free acid leaching technology

Iron ore tailings (IOTs), a typical hazardous solid waste, seriously threaten human health and the ecological environment. However, the abundance of quartz, particularly in high-silica IOTs, renders them useful. Yet, state-of-the-art technologies have rarely reported the preparation of high-purity silica from high-silicon IOTs. Thus, this study proposed an eco-friendly technology for producing high-purity silica from high-silica IOTs through the coupling of superconducting high gradient magnetic separation (S-HGMS) preconcentration with leaching followed by the use of ultrasound-assisted fluorine-free acid solution. Following an analysis of the separation index and chemical composition, the optimum conditions for the quartz preconcentration were determined as a magnetic flow ratio of 0.068 T s/m, a slurry flow velocity of 500 mL/min, and a pulp concentration of 40 g/L. Consequently, the SiO₂ grade increased from 69.32% in the raw sample to 93.12% in quartz concentrate following the application of S-HGMS, with the recovery reaching 45.24%. X-ray diffraction, vibrating sample magnetometer, and scanning electron microscope analyses indicated that quartz was effectively preconcentrated from the tailings by S-HGMS. Subsequently, employing the "ultrasound-assisted fluorine-free acid leaching process," impurity elements were removed and high-purity silica was produced. Under optimal leaching conditions, the SiO₂ purity of silica sand increased to 97.42%. Following a three-stage acid leaching process with 4 mol/LHCl +2 mol/LH₂C₂O₄, the removal efficiency of Al, Ca, Fe, and Mg exceeded 97% for all cases, and the SiO₂ purity in high-purity silica reached 99.93%. Thus, this study proposes a new strategy for the preparation of high-purity quartz from IOTs, which facilitated the effective realization of the high-value utility of the tailings. Furthermore, it provides a theoretical basis for the industrial application of IOTs, which is of great scientific significance and practical application value.

Infrared-Activated Bactericide: Rhenium Disulfide (ReS2)-Functionalized Mesoporous Silica Nanoparticles

An attractive strategy for treating bacterial infection is the combination of antibiotic chemotherapy with photothermal therapy (PTT), which could be implemented using multifunctional nanomaterials. In this work, the intrinsic photothermal efficiency of two-dimensional (2D) rhenium disulfide (ReS₂) nanosheets is enhanced by their coating on mesoporous silica nanoparticles (MSNs) to realize a highly efficient light-responsive nanoparticle endowed with controlled-release drug delivery capability, denoted as MSN-ReS₂. The MSN component of the hybrid nanoparticle features augmented pore size toward facilitating increased loading of antibacterial drugs. The ReS₂ synthesis is conducted in the presence of MSNs through an in situ hydrothermal reaction and leads to a uniform surface coating of the nanosphere. The MSN-ReS₂ bactericide testing showed more than 99% bacterial killing efficiency in both Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) upon laser irradiation. A cooperative effect that led to a 100% bactericide effect on Gram-negative bacteria (E. coli) was observed when tetracycline hydrochloride was loaded in the carrier. The results show the potential of MSN-ReS₂ to be used as a wound-healing therapeutic with a synergistic bactericide role.

Photo-induced reduction of vanadium in vanadium-containing iron/manganese oxide agglomerates by oxalic acid

The stockpiling of vanadium-containing tailings allows vanadium to migrate into the surrounding area, resulting in toxic metal contamination. By using the vanadium-bearing iron/manganese (Fe/Mn) oxide agglomerates as the simulated tailings, the feasibility of photo-induced reduction of vanadium by oxalic acid was investigated. Batch effects of the available light and the reducing agents on agglomerates were investigated. Results showed that oxalic acid (5 mmol L^-1) can convert V(V) to V(IV) and convert Fe(III) released from the Fe/Mn oxide agglomerates to Fe(II) under both light and dark conditions. After 45 d of reaction in the dark, oxalic acid converted 33.54% Fe(III) and 100% V(V) in the leachate into Fe(II) and V(IV). The Fenton reaction occurred by light irradiation significantly increased the redox potential in the solution, and also caused V(IV) to be oxidized. Overall, oxalic acid can rapidly reduce V(V) to V(IV), but sunlight may have an inhibitory effect on the reduction reaction. Present study can deepen the understanding of the mechanism for valence transformation of elements in minerals by sunlight, and can help in implementing tailings treatment and environmental remediation by using oxalic acid and avoiding light.

Highly Active Ni-Ru Bimetallic Catalyst Integrated with MFI Zeolite-Loaded Cerium Zirconium Oxide for Dry Reforming of Methane

The dry reforming of methane (DRM) is a new potential technology that converts two major greenhouse gases into useful chemical feedstocks. The main challenge faced by this process is maintaining the catalyst with high catalytic activity and long-term stability. Here, a simple and effective preparation route for the synthesis of functional nanomolecular sieve catalysts (NiRu_xCZZ5) from kaolinite tailings was developed for dry reforming of methane with CO₂. The silica monoliths with flower-like spherical and micropore structures (ZSM-5) were prepared by crystal growth method, and the metal components were loaded by ultrasonic-assisted impregnation method. The NiRu_0.5CZZ5 catalyst exhibited excellent catalytic performance (maxmium CO₂ and CH₄ conversions up to 100 and 95.6%, respectively) and very good stability (up to 100h). The interfacial confinement and the strong support interaction are principally responsible for the excellent catalytic activity of the catalyst. The in situ DRIFTS was used to elucidate the possible carbon conversion steps, and stable surface intermediates were also identified.

Passivation of heavy metals in copper-nickel tailings by in-situ bio-mineralization: A pilot trial and mechanistic analysis

Metal tailings contain a variety of toxic heavy metals and have potential environmental risks owing to long-term open piling. In the present study, a strain of ureolytic bacteria with bio-mineralization ability, Lysinibacillus fusiformis strain Lf, was isolated from copper-nickel mine tailings in Xinjiang and applied to a pilot trial of tailings solidification under field conditions. The results of the pilot trial (0.5 m³ in scale) showed that strain Lf effectively solidified the tailings. The compressive strength of the solidified tailings increased by 121 ± 9 % and the permeability coefficient decreased by 68 ± 3 %. Compared to the control, the leaching reduction of the solidified tailings of Cu and Ni was >98 %, and that of As was 92.5 ± 1.7 %. Two mechanisms of tailings solidification and heavy metal passivation were proposed based on the findings of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and energy-dispersive X-ray spectroscopy (EDS) mapping. Biogenic calcite filled the interstices of the tailings particles and cemented the adjacent particles. This improved the mechanical properties and reduced permeability. Moreover, heavy metal colloids were incorporated into large-sized calcite crystals, and heavy metal ions were sequestered within the calcite lattice. This method of using indigenous ureolytic bacteria to solidify tailings was successful in this work and may be replicated to remediate other tailings.

A review on the industrial solid waste application in pelletizing additives: Composition, mechanism and process characteristics

Reducing the cost of pellet additives as a substitute for reducing bentonite binder is an important research direction of new pellet additives. There are some industrial solid wastes that have the similar physical and chemical properties to bentonite, and SiO₂ content of them may be much lower than bentonite, but also contains a lot of Fe₂O₃, Al₂O₃, MgO, B₂O₃ and other components beneficial to the quality of pellets, which have been paid more attention by many pellet workers. In this review, the effect mechanism of Fe₂O₃, Na₂O/K₂O, Al₂O₃, SiO₂, CaO, MgO and B₂O₃ in the industrial solid wastes on the fired strength and reduction expansion of pellets were systematically summarized. At the same time, the influences of five representative large scale modified industrial solid waste additives including iron tailings, bauxite tailings, fly ash, red mud and boron sludge on the properties of green pellets and finished pellets were described in detail. It can be seen that the applications of industrial solid waste in pellet additives can partially or completely replace bentonite binder, especially fly ash, red mud and boron sludge, which can not only improve the quality of pellets, but also decrease the cost, save energy and reduce pollution, with significant economic benefits.

Phosphate Removal from Wastewater by Magnetic Amorphous Lanthanum Silicate Alginate Hydrogel Beads

It is of both fundamental and practical importance to develop effective adsorbents for removing phosphate from aqueous solutions continuously. In this study, magnetic amorphous lanthanum silicate alginate hydrogel beads (MALS-B) were prepared and used for phosphate removal. Mesoporous silica materials with highly ordered and hexagonal channel structures were synthesized from natural mineral rectorite (REC) at room temperature. On this basis, amorphous lanthanum silicate (ALS) was synthesized by theone-pot method using a silicon source from REC and a commercial lanthanum source. Further, MALS-B were synthesized from sodium alginate (SA) with ALS and Fe3O4 as the incorporated adsorbable and magnetic nanoparticles via a simple cross-linking method in CaCl2 solution. The synthesized hydrogel beads were characterized by various techniques. ALS and Fe3O4 existed relatively independently in MALS-B, where ALS provided adsorption sites and Fe3O4 provided magnetism. They played a synergistic role in phosphate removal. The saturation magnetization value of MALS-B was 17.38 emu/g, enabling theirfacile separation from aqueous solutions after phosphate adsorption. MALS-B exhibited a preferable adsorption capacity of 40.14 mg P/g for phosphorus compared to other hydrogel beads based on adsorption experiments. More significantly, MALS-B exhibited excellent selectivity for phosphate in aqueous solutions with various interfering ions and possessed a high affinity to phosphate in a wide pH range. MALS-B showed the treatment volume of 480 BV when effluent phosphate concentration was below 0.5 mg/L in fixed-bed column adsorption. The adsorption mechanism was also revealed. Our work demonstrates that MALS-B can serve as a promising adsorbent for continuous phosphate adsorption.

Toward broader applications of iron ore waste in pollution control: Adsorption of norfloxacin

Norfloxacin, a kind of antibiotic frequently detected in environments, represents a group of non-persistent organic pollutants with latent risks to the ecosystem. Iron ore waste, generated and accumulated in large quantities from the iron/steel industry, was evaluated as a potential sorbent for norfloxacin removal. Kinetics analysis showed that the adsorption process reached equilibrium at 72 h, and the adsorption process could be best defined by the pseudo-second-order kinetics with the primary mechanism of norfloxacin adsorption suggested to be cation exchange. Further, adsorption of norfloxacin to iron ore waste was shown to be facilitated by the pH range of 2-10, low cation concentration, and low temperature, which are characteristic of natural surface waters, suggesting the potential of practical applications in aquatic environments. These findings provide new insight into the potentials of beneficial reuse for iron ore waste in the adsorptive removal of environmental pollutants.

Mullite-Based Ceramics from Mining Waste: A Review

Mullite (3Al2O3·2SiO2) is an aluminosilicate characterized by excellent physical properties, which makes it an important ceramic material. In this way, ceramics based on mullite find applications in different technological fields as refractory material (metallurgy, glass, ceramics, etc.), matrix in composite materials for high temperature applications, substrate in multilayer packaging, protective coatings, components of turbine engines, windows transparent to infrared radiation, etc. However, mullite is scarce in nature so it has to be manufactured through different synthesis methods, such as sintering, melting-crystallization or through a sol-gel route. Commonly, mullite is fabricated from pure technical grade raw materials, making the manufacturing process expensive. An alternative to lowering the cost is the use of mining waste as silica (SiO2) and alumina (Al2O3) feedstock, which are the necessary chemical compounds required to manufacture mullite ceramics. In addition to the economic benefits, the use of mining waste brings out environmental benefits as it prevents the over-exploitation of natural resources and reduces the volume of mining waste that needs to be managed. This article reviews the scientific studies carried out in order to use waste (steriles and tailings) generated in mining activities for the manufacture of clay-based ceramic materials containing mullite as a main crystalline phase.

Effects of Curing Conditions on the MECHANICAL and Microstructural Properties of Ultra-High-Performance Concrete (UHPC) Incorporating Iron Tailing Powder

It has been reported that iron tailing powder (ITP) has the potential to partially replace cement to prepare ultra-high-performance concrete (UHPC). However, the reactivity of ITP particles in concrete largely depends on the curing method. This study investigates the effects of curing conditions on the mechanical and microstructural properties of UHPC containing ITP. To achieve this objective, three research tasks are conducted, including (1) preparing seven concrete formulations by introducing ITP; (2) characterizing their mechanical performance under different curing regimes; and (3) analyzing their microstructure by XRD patterns, FTIR analysis, and SEM observation. The experimental results show that there is an optimum ITP dosage (15%) for their application. The concrete with 15% ITP under standard curing obtains 94.3 MPa at 7 days, their early-age strength could be even further increased by ~30% (warm-water curing) and ~35% (steamed curing). The steam curing regime stimulates the activity of ITP and refines the microstructure. This study demonstrates the potential of replacing Portland cement with ITP in UHPC production.