Utilization Of Industrial Solid Wastes Research Articles

Preparation and alkali excitation mechanism of coal gangue-iron ore tailings non-sintering ceramsite

Non-sintering ceramsite is known for its simplicity in preparation technology and low production costs. The efficient utilization of industrial solid waste for non-sintering ceramsite production has garnered significant attention in green building materials within the framework of low carbon and environmental protection principles. This study focuses on preparing non-sintering ceramsites using non-active solid waste materials, specifically coal gangue and iron ore tailings. Firstly, a single-factor test was conducted to determine the optimal dosage of coal gangue and iron ore tailings. Subsequently, orthogonal tests were performed to investigate the influence of fly ash, NaOH, and aluminum powder on the mechanical properties of non-sintering ceramsite. Finally, the alkali excitation mechanism was elucidated through X-ray diffraction and SEM electron microscope scanning. The results reveal that the optimal proportions for coal gangue and iron ore tailings are 10 % and 35 %, respectively. Among the factors examined, NaOH dosage exerts the most significant impact on the compression strength and bulk density of non-sintering ceramsite, while aluminum powder dosage has the greatest effect on the 1-hour water absorption of the material. The optimal mixing ratio was determined with a total solid waste dosage of 73 %, meeting the national 600-grade standard for non-sintering ceramsite across all performance criteria. Furthermore, the alkali excitation process effectively activates the reactivity of fly ash and coal gangue. This activation leads to the generation of calcium alumina and C-S-H gel, along with other hydration products, which intertwine to form a dense gel structure. This structural enhancement further contributes to the improved performance of non-sintering ceramsite.

The Role of Chemical Activation in Strengthening Iron Ore Tailings Supplementary Cementitious Materials

The preparation of iron ore tailings (IOTs) into supplementary cementitious materials (SCMs) is an effective approach to achieve value-added utilization of industrial solid waste. This study systematically investigates the hydration pattern and strength development of Portland cement systems with the incorporation of IOTs, steel slag (SS), granulated blast-furnace slag (GBFS), and fly ash (FA) under the action of different chemical additives. The hydration products, and microstructure and pore structure of the SCMs are analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and mercury intrusion porosimetry. The findings of this study demonstrate that chemical activation plays a significant role in the strength development of SCMs. Among the five chemical activators tested, Triethanolamine (TEA) had the greatest influence on mechanical properties. The maximum compressive strength of the SCMs at 28 days was 42.9 MPa at a dosage of 1%. Specifically, the addition of TEA promotes volcanic ash reactions, and the high fineness of SCM provides nucleation sites for hydration products. Interactions between the volcanic ash reaction and the complexation reaction of TEA have a positive effect on compressive strength development. This research expands the potential for IOTs SCMs through chemical activation methods for value-added applications.

Mechanical performance, impact behavior and environmental assessment of coal furnace slag based low-carbon ultra-high performance engineered cementitious composites (UHP-ECC)

This study aimed to optimize the utilization of industrial solid waste through developing a high-performance cement-based composite material (UHP-ECC), incorporating coal furnace slag (CFS) and waste rubber powder (RP). The investigation concentrated on the effects of introducing 10% RP into UHP-ECC and replacing ordinary Portland cement (OPC) with CFS at varying proportions (0%, 20%, 40%, 60%) on mechanical properties, impact resistance, and sustainability. The mixtures underwent a comprehensive characterization, including mechanical tests, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), to clarify hydration mechanisms and microstructural features. The results revealed that the addition of 10% rubber led to flaws, resulting in a minor reduction in compressive strength from 143.2 MPa to 132.2 MPa. Substituting 20% with CFS resulted in a denser matrix, raising the compressive strength to 135.5 MPa. CFS decreased the initial cracking strength and matrix fracture toughness, with tensile strain peaking at 8.05% and narrower crack widths. More CFS content yielded a slight decrease in peak impact force but induced more fine cracks and enhancing ductility. Moreover, as CFS is a waste product generated at high temperatures, the mixture demonstrated outstanding impact performance at 150 °C, absorbing rather than converting more energy into kinetic energy. Comparative analysis against similar mixtures highlighted UHP-ECC's strengths in embodied carbon, embodied energy, and material cost. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) assessment identified the CFS40-R10 as better mixture, achieving a balance between mechanical performance, cost-effectiveness, and sustainability. Microscopic analysis revealed that up to 40% CFS facilitated hydration, and the 60% CFS mixture exhibited the lowest total mass loss at high temperatures.

Micro-assessment of heavy metal immobilization within alkali-activated copper tailings-slag geopolymer

To address the challenge of mitigating heavy metal pollution stemming from the utilization of industrial solid wastes like copper tailings, this study focused on the development of copper tailings-granulated blast furnace slag (CT-GBFS) geopolymer through alkali activation. The primary objective was to effectively immobilize heavy metals, specifically copper (Cu) and zinc (Zn), within the geopolymer. This investigation encompassed an exploration of how Cu and Zn impacted the mechanical properties of CT-GBFS geopolymer, along with an analysis of the leaching behavior of these heavy metals in various environmental conditions. The study also delved into the underlying mechanisms responsible for immobilizing these heavy metals. The experimental findings revealed that the inclusion of up to 2% heavy metals could enhance the mechanical properties of geopolymer. However, as the heavy metal content increased, a detrimental effect on the mechanical properties became evident. Furthermore, CT-GBFS geopolymer exhibited excellent heavy metal immobilization capabilities across different environmental conditions. Specifically, the immobilization rate for copper exceeded 98%, while zinc exhibited an immobilization rate exceeding 93%. The geopolymer has a physical encapsulation fixation mechanism for both Cu and Zn. Additionally, copper was observed to form a covalent bond with non-bridging oxygen in the geopolymer, manifesting as a Si–O–Cu structure, thereby effectively immobilizing the metal. Conversely, zinc was immobilized within the geopolymer through ionic bonding. In conclusion, the technology proposed in this study represents a significant step toward achieving the safe and resourceful utilization of copper tailings by effectively immobilizing heavy metals, thus mitigating their environmental impact.

Microwave co-pyrolysis of industrial sludge and waste biomass: Product valorization and synergistic mechanisms

Microwave co-pyrolysis of textile dyeing sludge (TS) and furfural residue (FR) was investigated in this study. Comprehensive pyrolysis index (CPI) was employed to investigate pyrolysis performance and FR addition significantly improved co-pyrolysis. Product distribution showed that increasing FR ratio enhanced the bio-oil and gas with significant reduction in biochar. For bio-oil, FR addition neutralized the strong alkalinity and inhibited the formation of nitrogen compounds. Moreover, bio-oil maintained a very low oxygenates content (0.97–5.97%). For biochar, co-pyrolysis was favorable for the enrichment of C and H and mitigated the potential contamination. FR addition increased the calorific value and contributed to pore development of biochar. Online inspection displayed that co-pyrolysis drastically restrained the release of sulfur-compounds and nitrogenates in volatile, while enhanced the production of alkanes, aldehydes, and ketones. Moreover, the interaction between TS and FR was influenced by their major components. For heavy metals (HMs), Er was at low risk for most HMs and FR addition ratios of 40 and 80 wt% appeared to be more favorable. Principal component analysis (PCA) showed that FR addition changed the decomposition behavior and affected co-pyrolysis process. This study also evaluated the co-pyrolysis synergistic mechanisms of TS and FR. Overall, microwave co-pyrolysis is a novel and effective method to reduce environmental pollution and produce high-quality products, providing new insights for the low consumption and efficient utilization of industrial solid waste.

Feasibility of Preparing Steel Slag–Ground Granulated Blast Furnace Slag Cementitious Materials: Synergistic Hydration, Fresh, and Hardened Properties

Steel slag and GBFS are wastes generated during the steel and iron smelting process, characterized by their considerable production rates and extensive storage capacities. After grinding, they are often used as supplementary cementitious materials. However, the intrinsic slow hydration kinetics of steel slag–GBFS cementitious material (SGM) when exposed to a pure water environment result in prolonged setting times and diminished early-age strength development. The incorporation of modifiers such as gypsum, clinker, or alkaline activators can effectively improve the various properties of SGM. This comprehensive review delves into existing research on the utilization of SGM, examining their hydration mechanisms, workability, setting time, mechanical strengths, durability, and shrinkage. Critical parameters including the performance of base materials (water-to-cement ratio, fineness, and composition) and modifiers (type, alkali content, and dosage) are scrutinized to understand their effects on the final properties of the cementitious materials. The improvement mechanisms of various modifiers on properties are discussed. This promotes resource utilization of industrial solid wastes and provides theoretical support for the engineering application of SGM.

Comparative Studies of Microstructural, Mechanical and Tribological behaviour of A319 alloy cast in solid waste mold and conventional sand Mold

Abstract This study investigates the potential of utilizing industrial solid waste (blast furnace slag, ferrochrome slag, and red mud) as mold materials to improve the solidification rate and wear resistance of A319 alloy. Unlike conventional molds such as silica sand and olivine sand, industrial solid waste poses an eco-friendly alternative, contributing to waste valorization. The motivation for this research drives the need for sustainable and efficient waste management practices in the industrial sector. By exploring the utilization of industrial solid waste as a mold material, study aims to address the current challenges in disposal, reduce environmental impact, and enhance the overall performance of A319 alloy through improved solidification and wear resistance. The experimental phase involved multi-factor reciprocating sliding wear tests conducted on a sample using a linear reciprocating tribometer, employing a steel ball as a counter face. The investigation of reciprocating wear characteristics aimed to assess the correlations between solidification rate and wear properties of a specimen cast in an industrial solid waste mold as well as a sand mold. Notably, tribological test results revealed a low wear rate of 3.3 mg/Km for the blast furnace slag mold. The scanning electron microscopy (SEM) image of the wear surface showed adhesive wear mechanisms. This study contributes valuable insights into the potential environmental and performance advantages of repurposing industrial solid waste for foundry applications.

Study on preparation and activation enhancement effect of cold bonded multi-solid waste wrap-shell lightweight aggregates (SWSLAs) with low cement content

Cement production consumes large amounts of depleted resources and energy, and causes environmental pollution. In order to reduce cement consumption and realize the closed-loop recycling of solid waste, cold bonded solid waste wrap-shell lightweight aggregates (SWSLAs) with a sextuplet blended system composed of dredged sediments, mineral powder, steel slag, phosphogypsum, fly ash, and a minimal amount of cement were prepared. Through the single-factor experiment, the influences of the types and dosages of solid wastes in the nuclear phase of SWSLAs (SWSLAs-NP) and shell phase of SWSLAs (SWSLAs-SP) on the strength and water resistance were explored, and the optimum ratio was obtained. On this basis, the influence of the types and amounts of activators incorporated in SWSLAs on the physical properties of aggregates was studied, and the primary microstructure of the aggregate was characterized. Our results showed that the optimal ratio of solid waste in the SWSLAs-NP was: 40 wt% of dredged sediments, 24 wt% of mineral powder, 18 wt% of steel slag, and 18 wt% of phosphogypsum. The optimal weight ratio of cement and solid waste in the SWSLAs-SP was 5:95. The resulting aggregate had a bearing capacity of single grain of 73.83 N and a water-resistance coefficient of 0.67. After the above aggregates were treated with Na2SO4 (activator) at 2%, the bearing capacity and water-resistance coefficient of the aggregates increased by 47.00% and 11.94%, respectively. The performances were even better than that of the aggregate composed of100w cement in the shell phase. Microstructural observations demonstrated that the structure of the raw material was reconstructed under the action of Na2SO4, and the raw materials reacted with each other, and thus the densification of the aggregate and its core-shell interface structure was enhanced, which improved the comprehensive performance of the aggregate. This study represents a step toward efficient utilization of industrial solid wastes.

Synergistic treatment of blast furnace slag and basic oxygen furnace slag for efficient recovery of iron: Phase transformation and oxidation mechanisms

In light of the steel industry's rapid advancements, the availability of high-quality mineral resources is diminishing. Therefore, the recovery of iron from BOF slag is of great significance to the sustainability development. Considering the compositional characteristics of BOF slag, the transformation of the iron-containing phase into (Mn,Mg)yFe3-yO4 is the key step. Thus, a novel process for recovering iron resources by synergistic treatment of blast furnace slag (BFS) and BOF slag was proposed. This research employed FactSage thermodynamic simulation, XRD, SEM-EDS, XPS, and EPMA to analysis the impact of BFS addition (10–50 %), cooling methods (from water-cooling to furnace-cooling), and temperature (1400–1600 °C) on phase transformation and the RO oxidation mechanism, and the conditions of (Mn,Mg)yFe3-yO4 generation and enrichment was obtained. The results show that at BFS addition of 30 %, reaction temperature 1400 °C and furnace-cooling, the iron-containing phase (Ca2Fe2O5 and RO) was almost completely transformed into (Mn,Mg)yFe3-yO4. The oxidation mechanism of RO was formation of (Mn,Mg)yFe3-yO4 by cation diffusion. Under optimal conditions, the iron recovery rate and the grade reached 65.74 % and 32.07 %, respectively, which can be used as raw material for ironmaking. Meanwhile, the main phase of the tailing slag was β-Ca2SiO4, without f-CaO, which has the potential to be used in the cement and concrete industries with the advantages of both low cost and eco-friendly. Therefore, the process with green, efficient and low cost was provided, which is a feasible idea for the comprehensive utilization of industrial solid waste.

An intelligent design method for new binder material activated by solid wastes by integrating attention-based tree model and heuristic optimization algorithm

To promote the utilization of industrial solid waste, a new green binder system namely SCGF for sustainable concrete is developed, in which slag-fly ash is activated by soda residue-carbide slag. However, the mix design of the SCGF is challenging due to heavy workload and the lack of theoretical basis. The relationship between mix proportion and mechanical properties of SCGF needs to be accurately expressed. In this paper, an intelligent design method of SCGF is proposed by coupling the attention mechanism, machine learning and multi-objective heuristic optimization algorithm. After training with experimental data, the prediction performance of attention-based tree model is evaluated. Multiple Pareto optimal solutions can be obtained by the proposed intelligent mix proportion design method. The results show that attention-based tree models perform higher accuracy (accuracy > 95 %) and better measures than that of classical tree models. Compared the strength and cost of SCGF to cement mortar, the mix proportion designed in this study has obvious advantages in environmental protection and economy (>50 % cost saving). Therefore, the proposed method can provide a theoretical basis for the recycling and utilization of industrial solid wastes.

The design of ternary all-solid-waste binder for solidified soil and the mechanical properties, mechanism and environmental benefits of CGF solidified soil

Utilization of industrial solid waste to develop binder and solidified waste soil, which can achieve ‘waste control by waste’. Based on the alkali-activated mechanism and interaction mechanism of the binder-soil particles-water, the component distribution ratio design method of ternary all-solid-waste binder for solidified soil was constructed. The CGF all-solid-waste alkali-activated binders (CGF binders) are composed of general industrial solid waste, with which calcium carbide slag (CCR) as alkali activator, ground granulated blast furnace slag (GGBS) and fly ash (FA) as high and low-activity pozzolanic material respectively. Macro and microscopic tests were performed to reveal the mechanical properties and solidification mechanism as well as quantitatively evaluate the environmental and economic benefits of CGF solidified pure clay, pure silt, and pure sand (CGF solidified soils). The results revealed that the strength of CGF solidified soils was significantly affected by the alkali activator content and the activity of pozzolanic materials, and the strength of partially CGF solidified soils were higher than cement solidified soils under the same conditions. The relationship between binder-soil particles-water, viz., the alkali-activated reaction between binder and water, along with the pozzolanic reaction between the alkali activator and the clay particles jointly determined the strength and strength growth rate of the solidified soil. The strength of the optimal CGF solidified soils were 1.38–2.30 times higher than cement solidified soils, however, the carbon emission per unit strength and cost per unit strength of the cement solidified soil were 71.43–125.02 times and 3.53–5.88 times higher than the optimal CGF solidified soils, respectively. The findings can provide a reference for the design and development of solid waste-based binders suitable for solidified soils.

Comprehensive utilization of blast furnace slag, municipal sludge and kaolin clay in building brick manufacture: Crystalline transformation, morphology observation and property assessment

At present, the comprehensive utilization of bulk industrial solid waste has attracted wide attention. The recycling of industrial solid waste in building materials not only provides valuable insights for the management of solid waste, but also alleviates the over-exploitation of natural clay resources in the construction industry. In this study, municipal sludge (MS) and blast furnace slag (BFS) were incorporated into kaolin clay (KC) to synthesize sustainable composite bricks, and the sintering effects and engineering properties of bricks were adjusted by changing BFS dosages. The results indicated that the addition of BFS would promote liquid glassy phase production in bricks due to the higher content of alkali/alkaline-earth metal oxides, and the ingredient, viscosity and content of liquid glassy phases could also be regulated through varying the dosage of BFS (0-15%), thereby affecting the pore structure, particle arrangement/consolidation and performance of bricks. Among all synthesized bricks, the optimum dosages of BFS, MS and KC for satisfying the building standard thresholds were 10%, 40% and 50%, with corresponding linear shrinkage, porosity, density, water absorption, compressive and flexure strengths of 12.97%, 18.15%, 1.83 g/cm3, 0.82%, 15 MPa and 38 Mpa, respectively. Finally, mechanism analysis further demonstrated that the formation and evolution of liquid glassy phases were the key responsibility for adjusting the brick micromorphology and performance. Based on this study, using MS and BFS in brick manufacturing benefited the value-added utilization of industrial solid wastes, clean protection of environments and sustainable production of building materials, providing a reference for the process optimization and potential application of MS and BFS wastes in masonry construction.

Solar-light-driven photocatalytic conversion of monosaccharide by oxygen-doped graphitic carbon nitride/artificial steel converter slag composite

The development of high performance, low-cost and resource-efficient photocatalysts with improved solar light harvesting capabilities can significantly enhance the practicability and viability of photocatalytic conversion of biomass-based substances to value-added chemicals. This work reports the construction of heterojunction between oxygen-doped graphitic carbon nitride and artificial steel converter slag (OCN/artCS) as efficient photocatalysts for conversion of biomass-derived monosaccharide to lactic acid under the simulated solar light. The OCN/artCS composites were facilely fabricated by the thermal polymerization of the mixtures of dicyanamide (DA) and oxalic acid (OA), which are precursors of OCN. The artCS acts as photocatalyst support for OCN to grow on its surface and can provide Ca2Fe2O5 semiconductor to possibly form the OCN/Ca2Fe2O5-containing artCS heterojunction. Compared with pristine OCN, the OCN/artCS composites exhibited higher photocatalytic performance for selective production of lactic acid, possibly due to the effective separation of photogenerated charge carriers after creation of OCN/artCS heterojunction. At the optimal content of artCS in the composites, the OCN/5%artCS delivered 99% glucose conversion and 90% lactic acid yield within 60 min at 50 °C under the simulated sunlight irradiation. This work can be a platform for the efficient utilization of industrial solid wastes for production of high-performance photocatalysts, enabling their promising applications in photobiorefinery and other photocatalytic processes.

Research on the comprehensive Efficiency Evaluation and Spatial Effect of New Green Dynamic Energy in China

Due to regional differences, different parts of the country attach different importance to green development, resulting in different measures and effects. In order to comprehensively and directly evaluate the benefits of new green kinetic energy and compare and analyze between different regions, this paper studies the measurement and influencing factors of new green kinetic energy. Based on the panel data of 31 provinces in China from 2010 to 2019, this paper first uses the entropy weight method to measure the score of new green kinetic energy and discusses its spatio-temporal evolution; Then, the spatial econometric panel model is used to explore the influencing factors of the new kinetic energy effect of green development in China's provinces. The results show that: (1) The amount of comprehensive utilization of industrial solid waste per unit and the amount of completed investment in industrial pollution control per unit played an important role in the new momentum of development;(2) Different provinces have different grades of green scores, which leads to regional differences. Most of the lower scores are in northwest China;(3) The number of research and test developers per unit of GDP, the number of high-tech enterprises per unit of GDP, and the reduction rate of energy consumption per unit of GDP play a negative role in the development of new green kinetic energy scores, while the increase rate of the secondary industry plays a positive role. This paper measures the new green kinetic energy from the aspects of environmental protection and green production and consumption. On this basis, the spatial effect is included in the analysis framework of the influencing factors of the new green kinetic energy, and the spatial econometric model is used to explore the mechanism of the new green kinetic energy. There is some innovation in research perspectives and methods.

Adsorption performance of phosphate in water by mixed precursor base geopolymers

Design of low-cost and high-removal efficiency phosphate adsorbents is of great significance for the control of eutrophication. In this study, fly ash and metakaolin were used as raw materials to evaluate the capability of phosphate adsorption and to investigate the mechanism of phosphate adsorption. The results of comparing the adsorption effect of geopolymers prepared with different modulus of alkali activator showed that the removal efficiency of phosphate in water at 0.8 M was on average 30.33% higher than 1.2 M. Therefore, FA + MK-0.8 had the maximum removal efficiency of 94.21% for phosphate in water with the maximum adsorption capacity of 36.02 mg/kg. In addition, the adsorption of phosphate could be well fitted by pseudo-second-order model and the process was mainly controlled by film diffusion. The alkali activation process can destroy the octahedral structure of the raw material, so the geopolymer are mainly tetrahedral in structure. Interestingly, new zeolite structures were formed in the mineral crystal phase of FA + MK-0.8, which may facilitate the adsorption of phosphate by geopolymers. Furthermore, the combined FTIR and XRD analysis results indicated that the underlying mechanisms of phosphate adsorption were electrostatic gravitation, ligand exchange, and surface complexation. This research not only synthesizes low-cost and high removal efficiency wastewater purification materials, but also provides a promising application for the elimination and resource utilization of industrial solid waste.

Frost Resistance and Shrinkage Characteristics of Soil Stabilized by Carbide Slag and Coal Gangue Powder

With the increase of expressway construction in seasonal frozen soil region, the freeze-thaw problem of subgrade soil has attracted more and more attention. In addition, the comprehensive utilization of industrial solid waste has become an important measure to build a resource-saving and environment-friendly society. In order to improve the frost resistance of subgrade soil and realize the resource utilization of industrial solid waste, carbide slag (CS) and coal gangue powder (CG) were applied to the subgrade soil. The unconfined compressive strength (UCS) test, freeze-thaw cycle test, dry shrinkage test, temperature shrinkage test and scanning electron microscope (SEM) test were carried out on CS-CG stabilized soil with a ratio of CS:CG = 70:30 and dosages of 5%, 10% and 15%. The freeze-thaw cycle degradation model of CS-CG stabilized soil was constructed to show the freeze-thaw deterioration mechanism after the mechanical properties, pore structure, and durability characteristics of the stabilized soil were examined. The results showed that the CS-CG stabilized soil had good frost resistance. After 6 freeze-thaw cycles, the UCS at 7d and 28 d was 2.86 MPa and 3.79 MPa, respectively, which were 22.6% and 35.5% lower than in samples that underwent no freeze-thaw action. The CS-CG stabilized soil had good crack resistance, slightly better dry shrinkage strain than lime stabilized soil, and excellent temperature shrinkage performance. With the increase of CS-CG dosage, the hydration products increased continuously. After freeze-thaw cycles, however, large pores and cracks gradually appeared in the stabilized soil, which led to an increase of porosity and pore diameter, and a decrease of pore abundance. Due to the influence of hydration degree, the porosity change at 7 d was less than that at 28 d. There was a f(n)/f0=βexp−λΔh relationship between UCS residual ratio and porosity variation of the CS-CG stabilized soil, and it had a good correlation. The CS-CG stabilized soil had good frost resistance and shrinkage characteristics, and could replace traditional cementitious materials such as Portland cement (PC) and lime for subgrade soil improvement in regions with seasonal frozen soil. Future research needs to focus on the performance regulation of CS-CG stabilized soil, which can make it more widely used.

Mechanical grinding activation of modified magnesium slag and its use as backfilling cementitious material

The utilization of industrial solid waste with potential cementitious activity to prepare low carbon, economic and environmental backfilling cementitious materials is an urgent issue in cemented paste backfill (CPB). In this work, the mechanical grinding activation of modified magnesium slag (MMS), including grinding kinetics, crystallinity, and the influences on backfilling paste characteristics, have been investigated systematically. The indexes of particle size distribution (PSD), fineness, and sieve residue indicate that the grinding efficiency of MMS is high when grinding time ranges [20,80] min. The particle coarsening appears when the grinding time increases to 120 min from 100 min. A fitted grinding kinetics function of MMS has been established based on the measured PSDs with six grinding time. The XRD shows that the diffraction peak intensities of CaSO4 and SiO2 phases decreases with the increasing of grinding time, indicating the increasing of lattice defects and amorphization degree. Both of grinding dispersion refinement and amorphization increase of MMS contribute to the activation of cementitious reactivity. Grinding time has a great influence on the properties of modified magnesium slag-based (MMS-based) backfilling pastes. The fresh backfilling pastes conformed to both of the H-B model and revised Bingham model well. The critical shear rate, critical apparent viscosity, and extended degree increase with the increasing of grinding time, indicating that the fluidity decreases. The TG-DTG, SEM tests show that hydration rate of the MMS-based backfilling pastes is slow and there are many interconnected micropores when the grinding time is below 60 min. Besides, the uniaxial compressive strengths (UCS) of MMS-based backfilling mortar samples also show a similar pattern. All tests showed that grinding for 60 min could stimulate most of the potential cementitious reactivity of MMS. Meanwhile, the corresponding backfilling paste behaves good working condition. Taken together, 60 min is suggested as the optimal grinding time for MMS in consideration of energy consumed and technical benefits, and the corresponding specific surface area (SSA) and 45 µm sieve residue (SR) are 503 m2/kg and 3.83 %, respectively.

Co‐utilization of secondary aluminum dross and ferronickel slag for preparation of cordierite–mullite insulating ceramic

AbstractBecause of the low utilization rate, a large amount of metallurgical slag was piled up or buried each year, resulting in serious environmental pollution and resource waste. This study focused on the value‐add utilization of secondary aluminum dross (SAD) and ferronickel slag (FNS) by preparing porous cordierite–mullite ceramics (CMC) for thermal insulation. The detailed thermodynamic calculation of the preparing process was carried out by using the phase diagram and equilibrium component function module in FactSage 8.1 software, which provided precise theoretical guidance for the practical synthesis experiment. The phase component, microstructure, and mechanical and thermal insulation properties of the prepared CMC at an FNS addition from 5 to 30 wt% were investigated by an X‐ray diffractometer, scanning electron microscopy assembled with an energy‐dispersive spectrometer, and a laser thermal conductivity testing instrument, respectively. It was shown that the original mineral phase of the raw materials applied can be converted to cordierite, mullite, and spinel after sintering at 1350°C, which results in higher strength and lower thermal conductivity of the prepared ceramics. Moreover, the increase of FNS addition promoted the content of cordierite and the microstructure densification of CMC. With the increase of FNS addition, the apparent porosity of CMC decreased from 41.7% to 34.4%, and the average pore size varied from 46.7 to 29.0 μm. The CMC with the lowest thermal conductivity of 0.86 W/(m K) was achieved at 20 wt% of FNS addition, which also had a good compressive strength of 52.8 MPa. The results proved the feasibility of preparing high‐strength thermal insulation ceramics by recycling hazardous metallurgical slag of SAD and FNS, proposing a novel route for high value‐added utilization of industrial solid waste.

Fabrication of multifunctional carbon/clay nanocomposites by recycling oil shale semi-coke waste for coloring and enhancing mechanical and aging-resistant properties of acrylonitrile–butadiene–styrene

With the increasingly demanding of environmental regulations, the disposal and sustainable resource utilization of industrial solid waste have attracted much attention. The carbon/clay nanocomposites were successfully fabricated derived from oil shale semi-coke waste via NaOH-assisted hydrothermal technology for coloring and reinforcing of acrylonitrile–butadiene–styrene in this study. The obtained nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy dispersive spectroscopy. With the increase in the mass ratio of NaOH to oil shale semi-coke, kaolinite, quartz, and other minerals in oil shale semi-coke gradually changed to analcine-C to faujasite-Na to sodalite, while the morphologies of carbon/clay nanocomposites transformed from nanosheets to nanosheets/nanorods to nanorods. Different morphologies had different effect on the mechanical properties of ABS, and the mixed-dimensional morphologies of the nanocomposites obviously improve the mechanical performances due to their synergistic effect compared with sheet-like and rod-like carbon/clay nanocomposites, respectively. Furthermore, the incorporation of carbon/clay nanocomposites into acrylonitrile–butadiene–styrene also enhanced its aging-resistant properties compared with the pure acrylonitrile–butadiene–styrene. Therefore, this study provides a feasible approach to realize the resource and sustainable utilization of oil shale semi-coke solid waste as functional filler for polymers.

A sustainable foamed material preparation via ettringite-targeted mineral transition of industrial solid wastes

Foamed material (FM) is widely considered efficient energy-saving building insulation material. Using solid waste as raw material and removing the autoclave process will further promote the green degree of FM. This study proposes a sustainable FM preparation via ettringite-targeted mineral transition of industrial solid wastes. A solid-waste-based sulfoaluminate clinker (SSC) was prepared for the first time entirely using industrial solid waste. Then, the synergistic effect and mechanism of SSC with high-content by-product gypsum were investigated. The most suitable matching scheme for preparing FMs based on SSC and by-product gypsum was finally determined. Results revealed that the different mineral compositions of the gypsum after calcination affected the hydration process of SSC in the mixture. The occurrence of unstable expansion is a threshold effect, mainly induced by the formation of ettringite exceeding the critical amount. When SSC was blended with by-product gypsum treated at 80 or 600°C, the mixed paste showed long-term volume stability. Under the similar initial rheological properties of paste and a fixed dosage of H2O2, the specific compressive strength, pore size distribution and water absorption of FM were significantly deteriorated with the increase of gypsum content. When by-product gypsum (treated at 80°C) utilization approached 65%, the FM still exhibited good properties: 534 kg/m3 density, 2.69 MPa 7-d compressive strength, 14.4% 24-h water absorption, and 0.143 W/m·K thermal conductivity. Moreover, the synergistic complementarity of ettringite with other components enhanced the performances of FM. This study expands a novel avenue for the large-scale and high-value utilization of industrial solid waste, especially by-product gypsum.