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The electrodes of industrial electrostatic precipitators degrade as a result of two phenomena: corrosion and erosion. The first is chemical degradation by highly reactive compounds formed during combustion, in particular, during the incineration of municipal or industrial wastes or high-sulfur coal. The degradation intensity of electrostatic precipitator electrodes depends on the chemical composition of the exhaust gasses. High concentrations of chlorides, fluorides, or sulfur in the exhaust gasses cause strong corrosion of the electrostatic precipitator elements. The second mechanism is the erosion caused by solid particles conveyed by the exhaust gas stream due to their collision with the electrodes. In this study, the analysis of the degradation of electrodes of an electrostatic precipitator downstream of an industrial waste incinerator was carried out. The industrial wastes of unknown sources were subjected to thermal degradation in a rotary kiln. The aim of this study was to provide fundamental knowledge about the mechanisms of electrode degradation located on the surface of discharge electrodes of electrostatic precipitators during the combustion of industrial wastes. [ABSTRACT FROM AUTHOR]

The utilization of industrial solid waste in mines is an important approach to resource utilization. The backfill material in mines is mainly composed of solid waste, which plays a supporting role. The excitation effect of lime on phosphogypsum and fly ash in backfill was studied in this paper. The macroscopic and microscopic characteristics of the backfill material were tested using uniaxial compression, nuclear magnetic resonance, scanning electron microscopy, and electrochemical techniques, and a relationship model was established between them. Furthermore, the influence of industrial solid waste on the properties of the backfill material under the action of lime and the hydration mechanism between different industrial solid wastes were studied. The results show that (1) under the action of lime, fly ash reacts with lime to produce C-S-H and C-A-H, and then C-A-H reacts with phosphogypsum to produce AFt. (2) The excess phosphogypsum also fills the pores. Therefore, 1.8% lime reduces the porosity of the backfill by 17.88% and increases the strength by 21.57%. (3) The cross-scale relationship shows that strength is inversely proportional to each type of pore content and fractal dimension, and it logarithmically increases with impedance at different frequencies. The lower the frequency, the stronger the relationship is. (4) This study indicates that industrial solid waste is a suitable cement replacement. [ABSTRACT FROM AUTHOR]

The huge demand for sand and gravel resources in road engineering construction leads to excessive consumption of resources and environmental damage. Recycling waste concrete and industrial solid waste as a road material is a promising alternative. In order to explore the application of these solid wastes in the road base, this paper studies the effect of adding lithium slag activated by an alkaline activator, fly ash (FA) and a combination of the two on the compressive strength, splitting strength and shrinkage performance of recycled cement-stabilized macadam mixture (RCSM). The optimum content of recycled aggregate (RA), alkali-activated lithium slag (AALS) and FA in composite-improved RCSM was optimized using a response surface method (Box–Behnken), and the microscopic characteristics of the mixture were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the optimum dosage of AALS, FA and RA determined by the response surface method is 15%, 10% and 40%, respectively. Compared with the cement-stabilized macadam mixture (CSM) with 40% RA, the 28 d compressive strength and 28 d splitting strength of the composite-improved RCSM are increased by 26.8% and 22.9%, respectively, and the dry shrinkage coefficient and average temperature shrinkage coefficient are decreased by 25.8% and 14.8%, respectively. Microscopic tests show that AALS and FA participate in the hydration reaction, generate more hydrated silicate (C-S-H) and ettringite (AFt), refine pores, effectively improve the performance of the internal interface transition zone of the mixture, make the microstructure of the mixture denser, and improve the strength and shrinkage performance of RCSM. This study provides technical support for the reuse of resources and the sustainable development of road construction. [ABSTRACT FROM AUTHOR]

The utilization of carbon dioxide and combustion products in cost- and energy-efficient technologies is an important element of creating sustainable energy systems, particularly in the transition period towards carbon neutrality and in light of the latest political developments, when solid fuels are still competing for a dominant role in securing energy supplies. Within the study presented, bituminous coal-derived fluidized bed fly ash samples of high calcium content, treated using a dry carbonation method under ambient conditions, were tested in terms of their specific properties to determine their usability in the preparation of injection mixtures for the filling of voids after shallow mining activities and other selected geo-engineering techniques. The study goes beyond the existing literature in terms of the carbonation method used, alkaline earth metal source, scale of the experiment, process conditions employed and product application studied. The results showed that the bituminous coal-derived fluidized bed fly ash, carbonated using the direct method adopted, may be successfully employed as the main solid component (over 82% w/w) of the injection mixtures for filling voids after shallow mining activities. The achievable compressive strength of a few MPa makes these materials applicable also in terms of ground strengthening in case it is required in light of the expected land development options to be employed. All principal materials used in the injection mixtures developed (carbonated fluidized bed fly ash, carbon dioxide, bottom ash) are industrial waste, and the carbonation method employed is simple and performed under ambient conditions, which reduces the required energy and cost input of filling mixture production, avoids the surface waste storage requirements, and contributes to the development of low energy-intensive carbon dioxide utilization and solid waste valorization methods. [ABSTRACT FROM AUTHOR]

The recycling of hazardous industrial waste into high-tech materials with desired properties is of considerable interest since it provides optimal alternatives for its final disposal. Coal fly ash, the major waste generated by coal-fired power plants, contains significant quantities of dispersed microspheres with a diameter smaller than 10 μm, which are anthropogenic atmospheric pollutants PM10. Due to their composition and fine-grained powder morphology, they can be converted into sintered products. In this study, dispersed microspheres from class C fly ash were directly sintered without any additive to form high-strength glass-ceramics with magnetic properties. The optimum processing conditions were achieved at a temperature of 1200 °C, at which samples with a compressive strength of 100.6 MPa were obtained. Sintering reduces the quantity of the glass phase and promotes the formation of larnite, Fe-spinel, ye'elimite, and ternesite. Mössbauer measurements show that the relative concentration of the magnetic phase compared to the paramagnetic one rises almost in order. The sintered sample demonstrates a narrower distribution of the hyperfine magnetic field and a significantly lower value of the coercive field of 25 Oe, which allows proposing such materials as soft magnetic materials. The presented results demonstrate promising industrial applications of hazardous PM10 to minimize solid waste pollution. [ABSTRACT FROM AUTHOR]

To reduce the harm caused by industrial solid waste to the environment, and solve the problem of excavated soil disposal in buried pipeline management projects, this study proposes a method to produce soil-based controlled low strength materials (CLSM) by using industrial solid wastes (including fly ash and red mud) as partial replacements for cement. The properties of CLSM were characterized in terms of flowability, unconfined compressive strength, phase composition and microstructure. The test results showed that fly ash could significantly improve the flowability of CLSM, while red mud had more advantages for the strength development. When 20% fly ash and 30% red mud were combined to replace cement, the fluidity of CLSM was 248 mm, and the unconfined compressive strength (UCS) at 3, 7 and 28 days was 1.08, 1.49 and 3.77 MPa, respectively. The hydration products of CLSM were mainly calcium silicate hydrate gels, ettringite and calcite. Fly ash provided nucleation sites for cement hydration, while the alkali excitation of red mud promoted the dissolution of SiO2 and Al2O3 in fly ash. The filling and gelation of hydration products make the microstructure dense, which improves the mechanical properties of the mixture. [ABSTRACT FROM AUTHOR]

Each year, China produces a substantial amount of municipal sludge, industrial waste (slag, fly ash, and desulfurized gypsum), and construction waste, while its recycling rate is low. If not disposed in a properly and timely manner, this inequity can have serious environmental impacts. This study aimed to prepare a new type of modified sludge material with high strength, low shrinkage, and low permeability by curing municipal sludge with industrial waste (slag, desulfurized gypsum, and fly ash) and powdered construction waste. At specific maintenance ages, the modified sludge material was examined for shrinkage deformation, water content, compressive strength, and hydraulic conductivity. The modified sludge material was also tested by scanning electron microscopy (SEM + EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) tests. The hydration products, micromorphology, and elemental composition of modified sludge were also analyzed at specific maintenance ages. These analyses revealed the mechanism of solidification of municipal sludge by industrial waste and powdered construction waste and the changes in the microstructure of the sludge. The results showed that the compressive strength of the modified sludge ranged from 3.83 to 8.63 MPa, volumetric shrinkage ranged from 2.12 to 12.68%, and hydraulic conductivity ranged from 1.65 × 10−8 to 2.21 × 10−7 cm/s after 28 d of maintenance. The active substances, such as SiO2, Al2O3, and CaO, in the industrial waste, powdered construction waste, and municipal sludge were subjected to a hydration reaction in an alkaline environment to produce dense blocks, agglomerates of C-S-H, ettringite, gismondine, and other hydration products. The compressive strength of the modified sludge increased, and its internal structure was dense. [ABSTRACT FROM AUTHOR]

The high chloride content of municipal solid waste incineration (MSWI) fly ash and hazardous waste incineration (HWI) fly ash has considerably affected their disposal. This study focused on investigating the three-stage counter-current (TSC) water-washing process to reduce the chlorine content efficiently under the premise of low water consumption. The liquid–solid ratio (LSR) and washing time were investigated, a chloride migration model was established, and the characteristics of the water-washing solution (WWS) and washed fly ash were investigated. The results showed that the dechlorination effect of TSC washing could reach more than 99% in a low liquid–solid ratio (LSR) of 2–4 kg/L. The most appropriate LSR and washing time were found to be around 3:1 L/kg and 15 min per stage, respectively. The concentration of Cl− in WWS reached over 90 g/L, which is very high among industrial saline wastewater. Some heavy metals were also contained in the WWS, and lead was the main heavy metal, followed by zinc, copper, and arsenic. The concentration of WWS of different stages was calculated by a model, and the transfer characteristic of chloride was strongly related to the mass balance between the liquid contained in the solid–liquid separation residue (SR) and the separated liquid. After washing, due to the dissolution of soluble salt, the specific surface area of fly ash increased, and thus the absorption ability of the washed fly ash was greater than the raw one. This study provides a washing condition reference for highly chlorinated fly ash, the basic data of WWS, and the chloride migration model that is a preliminary calculation method to improve the water-washing process. [ABSTRACT FROM AUTHOR]

Magnesium oxychloride cement (MOC), a type of special construction material, has drawn much research attention in solid waste utilization and environmental protection due to its eco-friendly production. Ammonia soda residue (ASR), a by-product generated from sodium carbonate manufacturing, is one of the industrial wastes that can be recycled in MOC systems. However, ASR exhibits adverse effects on the fresh performance and volume stability of MOC pastes. This paper aims at improving the properties of ASR-MOC by introducing fly ash (FA), solid waste from the power industry. Firstly, the roles of FA in MOC pastes are evaluated and analyzed. Then, three substitution ratios of FA (33.3%, 50% and 66.7% in weight) for ASR are designed for MOC pastes with 10% to 40% industrial wastes. Flowability, setting, strength and expansion of all mixtures were experimentally studied. Furthermore, X-ray diffraction (XRD) and scanning electron microscope (SEM) approaches were adopted to illustrate the microstructure changes. Results show that by adding different amounts of FA, the inferior flowability of MOC caused by ASR can be improved by 6–23%, the setting process can be prolonged by 30–55% and the expansion ratio can be reduced by 14–66%. The intensity of characteristic peaks of 5-phase and Mg(OH)2, together with the degrees of crystallization in XRD curves, well explain the strength variation and volume stability of ASR-MOC pastes. According to the regulation of relative specification, up to 20% of solid wastes in weight (10% FA + 10% ASR) can be consumed, contributing greatly to the greener sustainable development of construction materials. [ABSTRACT FROM AUTHOR]

Four industrial wastes, i.e., blast furnace slag, steel slag, desulfurization ash, and phosphoric acid sludge, were used to prepare a low-carbon binder, metallurgical slag-based cementitious material (MSCM). The feasibility of solidification/stabilization of municipal solid waste incineration (MSWI) fly ashes by MSCM were evaluated, and the immobilization mechanisms of heavy metals were proposed. The MSCM paste achieved 28-day strength of 35.2 MPa, showing its high-hydration reactivity. While the fly ash content was as high as 80 wt.%, the 28-day strength of MSCM-fly ash blocks reached 2.2 MPa, and the leaching concentrations of Pb, Zn, Cr, and Hg were much lower than the limit values of the Chinese landfill standard (GB 16889-2008). The immobilization rates of each heavy metal reached 98.75–99.99%, while four kinds of MSWI fly ashes were solidified by MSWI at fly ash content of 60 wt.%. The 28-day strength of binder-fly ash blocks had an increase of 104.92–127.96% by using MSCM to replace ordinary Portland cement (OPC). Correspondingly, the lower leachability of heavy metals was achieved by using MSCM compared to OPC. The mechanisms of solidification/stabilization treatment of MSWI fly ash by MSCM were investigated by XRD, SEM, and TG-DSC. Numerous hydrates, such as calcium silicate hydrate (C-S-H), ettringite (AFt), and Friedel's salt, were observed in hardened MSCM-fly ash pastes. Heavy metals from both MSWI fly ash and MSCM could be effectively immobilized via adsorption, cation exchange, precipitation, and physical encapsulation. [ABSTRACT FROM AUTHOR]

Featured Application: This work aims to further decrease the environmental footprint of alkali-activated materials by using an industrial wastewater to partially replace a commercial activator. Alkali-activated materials are generally considered a more sustainable alternative to Portland cement binders. This derives not only from the use of solid wastes as precursors, but also from the low temperatures required for their synthesis. However, to increase the environmental advantages of these materials, alternative activators should be explored, as the common route involves the use of commercial activators such as sodium silicate or sodium hydroxide solutions. In this work, the possibility of using an alkaline industrial wastewater, coming from a Portuguese paper and pulp industry, as a partial replacement of the commercial sodium hydroxide solution was studied. The results show that the use of the industrial wastewater decreased the workability of the pastes and their setting times, higher incorporations inducing a stronger reduction. Despite this, the results demonstrate the feasibility of replacing up to 25 vol.% of the sodium hydroxide solution with the industrial wastewater without compromising the mechanical performance of the binder. The compressive strength of this composition reached 22.7 MPa, this being slightly higher than the value seen in the reference (20.0 MPa). The use of a waste-containing activator, as reported here, might be a key driver to foster the wider use of this technology. [ABSTRACT FROM AUTHOR]

Traffic noise and solid waste pollution are two major problems that restrict urban development and affect urban environments. In this study, a new kind of cement-based material for sound barriers was prepared using industrial waste fly ash cenosphere to explore the material ratio of the sound absorption, sound insulation, and composite layers and to optimize the material's properties. The research findings showed that the compressive strength had significant effects on the material properties of the sound absorption layer, with the optimal compressive strength range being 0.2–0.4 MPa. At 0.4 MPa, the material with an aggregate-to-binder ratio of 1.0 had the best comprehensive properties. The sound insulation layer had the best compressive strength of 29.00 MPa at a 45% fiber admixture. The composite had the best sound insulation when the thickness ratio of the sound absorption and insulation layers was 60:40, and the sound transmission loss was 38 dB. The embodied carbon (EC) and embodied energy (EE) of the new fly ash cenosphere across the whole life cycle were 57.57 kgCO2e and 477.08 MJ, respectively, which were 4.8−52.9% and 53.2−82.3% lower than other traditional sound barriers, respectively. Thus, they were environmentally friendly and had satisfactory energy-saving and environmental protection values. [ABSTRACT FROM AUTHOR]

In order to prepare a new type of landfill covering material for closure, we used industrial calcium-containing waste (construction rubbish, slag, desulfurized gypsum and fly ash) to modify the dredged urban sludge. Shrink, unconfined compression, shear and infiltration tests were performed to obtain the volume shrinkage, compressive strength, shear strength and permeability coefficient of the modified sludge, as well as the permeability coefficient under the action of wet and dry cycles. Comprehensive characterization of the modified sludge using X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy with energy dispersive spectroscopy detection methods, resulted in the hydration products, molecular groups and microstructure characteristics of the modified sludge and revealed the modification mechanism of calcium-containing waste to sludge. After natural curing for 28 d, the volume shrinkage rate of the modified sludge sample was 2.6~8.3%, the unconfined compressive strength was 7.9~14.5 MPa, the cohesion force c was 179~329 kPa, and the internal friction angle φ was 42.59~53.60°. After six wet and dry cycles, there were no cracks in the modified sludge; the permeability coefficient of the modified sludge reached stability at 0.84–11.1 × 10−7 cm/s; and the permeability coefficient of MS7 sample was less than 1 × 10−7 cm/s, which met the engineering anti-seepage requirements of the landfill closure cover. The industrial calcium-containing waste by alkali formed C–S–H and C–A–S–H gelled geopolymer, which filled the gaps between soil particles to form a strong soil cement skeleton. Therefore, the mix ratio of sludge:construction waste:slag:fly ash:desulfurized gypsum was 50:22:15:8:5. Calcium-containing solid waste modified sludge can be used as a cover material for landfill closure. [ABSTRACT FROM AUTHOR]

At present, the world is committed to the development of environmentally friendly, sustainable and industrial safety. The effective treatment of industrial solid waste can be applied in the field of industrial safety. It is one of the ways to apply industrial solid waste to industrial safety to modify industrial solid waste and combine active powder to prepare industrial solid waste-based composite powder explosion inhibitors and apply it to underground coal dust explosion. This paper introduces the modification and preparation methods of industrial solid waste, and analyzes the good explosion suppression effect and good economic benefit of industrial solid waste-based composite powder explosion inhibitors on coal dust explosion. In this paper, four kinds of industrial solid wastes (red mud, slag, fly ash and sludge) were modified, and the modified solid waste materials with good carrier characteristics were obtained. Combined with a variety of active powders (NaHCO3, KH2PO4 and Al(OH)3), the industrial solid waste-based composite powder explosion inhibitors were obtained by solvent-crystallization (WCSC) and dry coating by ball milling (DCBM). Those kinds of explosion inhibitors can suppress the explosion of pulverized coal in 40–50% of cases. Compared with the powder explosion inhibitor commonly used in industry, it has a lower production cost and better explosion suppression effect. Those kinds of explosion inhibitors have a good industrial application prospect. [ABSTRACT FROM AUTHOR]

The potential of applying geopolymerization to a wide range of solid industrial waste and by-products is of great interest. In this research, the physical and mechanical properties of fly ash (FA)-based geopolymer concrete (GC), compared to those of cement concrete (CC), were studied. Three GCs with different content of FA and three appropriate CCs were designed, prepared, tested and evaluated. The results were compared with the requirements of Standards EN 206-1 and EN 1992-1-1. It was shown that in some cases minor adjustments of the regulations are needed, while in other cases complete revision is required. GC indicated competitive compressive strength compared to CC, tensile strength within the limits specified by Eurocode 2 for CC and modulus of elasticity about 50% less than that of CC. The ratio of binder (FA) to aggregates seems to have a significant effect on the properties of GC. The concrete with 750 kg/m3 FA seems to be the best choice taking into consideration both engineering and environmental criteria. [ABSTRACT FROM AUTHOR]

CO2 mineralization (aka mineral carbonation) is a promising method for the chemical sequestration of CO2 via reaction with oxides of alkaline or alkaline-earth metals to form carbonates. It has documented advantages over similar technological solutions to climate change. The huge amount of industrial solid waste, as a serious environmental issue confronted by China, can provide additional alkalinity sources for CO2 mineralization. In this study, we present an overview of the latest advances in the emerging technologies of CO2-mineralization via industrial solid waste in China, from the perspective of both theoretical and practical considerations. We summarize the types of industrial solid waste that are used (mainly coal fly ash, steel slag, phosphogypsum, and blast furnace slag) and the technological options available in the literature, with an emphasis on the discussion of the involved process-intensification methods and valuable chemicals produced. Furthermore, we illustrate the current status of pertinent policies, and research and development activities in China. Finally, we identify the current knowledge gaps, particularly in understanding the overall sustainability performance of these CO2-mineralization technologies, and indicate that the technical, economic, and environmental challenges of promoting and commercializing these technologies for the co-utilization of industrial solid waste and carbon resources call for, amongst other things, more joint efforts by chemists, chemical engineers, and environmental scientists, and more feedback from the energy and industrial sectors. [ABSTRACT FROM AUTHOR]

Buried pipe design requires knowledge about the fill to design the backfill structure. The interaction between the backfill envelope and the pipe impacts the structural performance of the buried pipe. The backfill material and compaction level respond to the backfill's overall strength and, therefore, for pipe-soil interaction. The strength of backfill material is described in terms of modulus of soil reaction E' and constrained modulus Eode. As the E' is an empirical parameter, the Eode can be measured in the laboratory by performing the oedometer tests. In this study, we have performed extensive oedometric tests on five types of anthropogenic materials (AM). Three of them are construction and demolition materials (C–D materials) namely, recycled concrete aggregate (RCA), crushed brick (CB), and recycled asphalt pavement (RAP). Two of them are industrial solid wastes (ISW) namely, fly ash and bottom slag mix (FA + BS) and blast furnace slag (BFS). The results of the tests revealed that AM behaves differently from natural aggregates (NA). In general, the Eode value for AM is lower than for NA with the same gradation. Despite that, some of AM may be used as NA substitute directly (RCA or BFS), some with special treatment like CB and some with extra compaction efforts like RAP or FA + BS. [ABSTRACT FROM AUTHOR]

Worldwide disposal of multi-tonnage solid waste from coal-burning thermal power plants (TPPs) creates serious environmental and economic problems, which necessitate the recovery of industrial waste in large quantities and at commercial prices. Fly ashes (FAs) and slag from seven Bulgarian TPPs have been successfully converted into valuable zeolite-like composites with various applications, including as adsorbents for capturing CO2 from gases and for removal of contaminants from water. The starting materials generated from different types of coal are characterized by a wide range of SiO2/Al2O3 ratio, heterogeneous structure and a complex chemical composition. The applied synthesis procedure resembles the formation of natural zeolites, as the raw FAs undergo long-term self-crystallization in an alkaline aqueous solution at ambient temperature. The phase and chemical composition, morphology and N2 adsorption of the final zeolite products were studied by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-Ray Diffraction (XRD) and Brunauer–Emmett–Teller (BET) analyses. The growth of faujasite (FAU) crystals as the main zeolite phase was established in all samples after 7 and 14 months of alkaline treatment. Phillipsite (PHI) crystals were also observed in several samples as an accompanying phase. The final products possess specific surface area over 400 m2/g. The relationships between the surface properties of the investigated samples and the characteristics of the raw FAs were discussed. All of the obtained zeolite-like composites were able to remove the highly toxic dye (malachite green, MG) from water solutions with efficiency over 96%. The experimental data were fitted with high correlation to the second-order kinetics. [ABSTRACT FROM AUTHOR]

High-density polyethylene (HDPE) geomembrane is often used as an anti-seepage material in domestic and industrial solid waste landfills. To study the interfacial shear strength between the HDPE anti-seepage geomembrane and various solid wastes, we performed direct shear tests on the contact interface between nine types of industrial solid waste or soil (desulfurization gypsum, fly ash, red mud, mercury slag, lead-zinc slag, manganese slag, silica fume, clay and sand) and a geomembrane with a smooth or rough surface in Guizhou Province, China. Friction strength parameters like the interfacial friction angle and the apparent cohesion between the HDPE geomembrane and various solid wastes were measured to analyze the shear strength of the interface between a geomembrane with either a smooth or a rough surface and various solid wastes. The interfacial shear stress between the HDPE geomembrane and the industrial solid waste increased with shear displacement and the slope of the stress-displacement curve decreased gradually. When shear displacement increased to a certain range, the shear stress at the interface remained unchanged. The interfacial shear strength between the geomembrane with a rough surface and the solid waste was higher than for the geomembrane with a smooth surface. Consequentially, the interfacial friction angle for the geomembrane with a rough surface was larger. The geomembrane with a rough surface had a better shear resistance and the shear characteristics fully developed when it was in full contact with the solid waste. [ABSTRACT FROM AUTHOR]