Ash Treatment Research Articles

Immobilization mechanism of heavy metals by crystals and liquid phase during melting treatment of MSWI fly ash

Melting treatment has emerged as a promising technology for managing municipal solid waste incineration (MSWI) fly ash owing to its advantageous features of effective detoxification and volume reduction. The melting treatment of MSWI fly ash involves the immobilization of heavy metals by crystals and liquid phase. Herein, the immobilization mechanism of heavy metals (Cu, Pb and Cd) by the crystals and the liquid phase was investigated using melting experiments, thermodynamic calculations and density functional theory (DFT) calculations. Results demonstrate that the immobilization of heavy metals is influenced by a combination of factors: the reaction of heavy metals, physical encapsulation ability of the liquid phase and chemical fixation ability of both the crystals and the liquid phase. An increase in the content of SiO2 and Al2O3 promotes the conversion of heavy metals oxides into heavy metals chlorides. Furthermore, an increase in the content and polymerization degree of the liquid phase facilitates the physical encapsulation of heavy metals chlorides. The chemical fixation ability of the crystals and the liquid phase differs for Cu and Pb, while Cd cannot be immobilized through chemical fixation. To enhance the immobilization of heavy metals during melting treatment, the chemical composition of MSWI fly ash should be adjusted within the anorthite region of the ternary phase diagram. This study provides valuable insights into the immobilization mechanism of heavy metals by the crystals and the liquid phase during the melting treatment of MSWI fly ash.

Advancing bamboo fiber reinforcement: A novel approach using eco-friendly plant ash alkali treatment.

This study aimed to enhance the engineering performance of bamboo fibers for use in composite materials by employing a sustainable plant ash alkali treatment. The primary objective was to improve the tensile strength, crystallinity, and thermal stability of bamboo fibers, which are known for their high specific strength, low density, and biodegradability but suffer from poor compatibility with hydrophobic matrices. The study involved treating bamboo fibers with varying concentrations of plant ash solutions (5 %, 10 %, 20 %, and 30 % by mass fraction) and comparing the results with those from conventional NaOH treatment. The results showed that plant ash treatment at a 20 % concentration significantly improved tensile strength by 14.16 % compared to untreated fibers, increased the crystallinity index to 75.57 %, and enhanced thermal stability, retaining more residual mass at high temperatures than NaOH-treated fibers. These improvements are attributed to the reduction in fiber polarity and better preservation of fiber structure. The findings suggest that plant ash, as a cost-effective and eco-friendly alternative to NaOH, can significantly enhance the mechanical and thermal properties of bamboo fibers, making them suitable for use in environmentally sustainable composite materials in construction, and other industries.

SUGAR CANE BAGASSE ASH IN CONCRETE: A REVIEW

Sugarcane bagasse ash (SCBA), a by product of sugarcane processing, has shown great potential as a supplementary material in concrete production. A review of its application in concrete highlights its benefits, including improved mechanical properties, durability, and sustainability. SCBA contains high levels of silica, which can act as a pozzolanic material, enhancing the compressive strength and reducing the permeability of concrete. Incorporating SCBA also lowers the carbon footprint of concrete, contributing to greener construction practices by partially replacing cement. However, challenges remain, such as the variability in ash quality, proper ash treatment, and optimal blending ratios. Ongoing research focuses on refining these aspects to maximize the benefits of the SCBA in concrete, making it a promising alternative in the construction industry for sustainable development. Keyword - Sugarcane bagasse ash, Compression strength, Percentage strength, Sugarcane Workability, Slump test.

Ash Treatment Promotes the Revegetation of Abandoned Extracted Peatlands

Treating peat with nutrient-rich ash significantly increases the content of different nutrients in the substrate. Such ash treatment promotes the revegetation of abandoned extracted peatlands. The aim of this study is to analyze the effect of wood ash (WA15 = 15 t ha−1 and WA10 = 10 t ha−1), oil shale ash (OSA8 = 8 t ha−1), and a mixture of wood ash and oil shale ash (WA10 + OSA8) on the revegetation (vascular plants and bryophytes) of the Puhatu abandoned extracted peatland in NE Estonia. The following results were obtained: (1) The MRPP tests indicate that there are compositional differences between the treatments. (2) Altogether, 23 vascular plant and 3 bryophyte species were recorded in the treatment areas. (3) Nine years after these ash treatments, the highest mean vascular plant species richness was recorded for WA15 (3.8 ± 0.3) and the lowest for OSA8 (2.0 ± 0.3). (4) A greater number of vascular plant species was observed in the WA15 area. (5) Mixed ash and wood ash had a significant effect on the amount of biomass in vascular plants. Treating with either wood ash or a mixture of ash ensured the rapid formation of vascular plants and bryophyte layers, contributing to the restoration of the abandoned peatland ecosystem.

Chlorellestadite-enriched waste-to-energy fly ashes in cementitious systems: Implications of ash treatment on end use

Waste-to-energy (WTE) plants generate fly ashes that are often destined for the landfill. These ashes are rich in chlorine, zinc, and various heavy metals. Here, we investigate the feasibility of their incorporation within cementitious systems in the context of a novel treatment process that chemically binds chlorines into chlorellestadite. Untreated ashes enhance the hydration kinetics and strength, likely due to excess Cl. However, the treated ashes retard the hydration because of the presence of ZnO (2–6 wt%). This retardation was successfully mitigated with up to 2 % calcium nitrate additive, resulting in cement-ash pastes that had mechanical strength comparable to 100% cement pastes. The untreated ashes leached excess Cl and led to the precipitation of hydrocalumite, whereas the treated ash–cement pastes were free from this phase. Finally, for ashes incorporated in hardened cement pastes, the leaching of heavy metals such as Pb and Cr was well under the toxicity limit, for both treated and untreated ashes. In summary, untreated ashes may find end use in unreinforced concrete applications, and treated ashes may be used within reinforced concrete, at least up to 10% cement replacement level.

The potential of seaweed biochar and fly ash amendments in enhancing vermi-degradation and the fertilizer value of cow manure, wastepaper-based vermicompost

This study evaluated the potential of amending cow manure (CM) based vermicompost with fly ash (FA) and seaweed biochar (Bio) on vermidegradation, nutrient release and early crop growth. All treatments, except CM + fly ash, resulted in a C/N ratio below 20, indicating a mature compost. The CM + Biochar treatment had the highest Olsen-P of 274.75 mg/kg whilst the CM + Fly ash treatment had the lowest concentration of 239.13 mg/kg. Only Zn showed a consistent increasing trend of 51.5 %, 45.6 %, 53.6 %, and 47.8 % for the CM + fly ash, CM + FA + Bio, CM + Bio, and CM treatments, respectively. For crop germination, the CM + fly ash compost needs to be substituted at 25 % in cocopeat, whilst 50 % substitution is suitable for seedling development. Future studies need to evaluate the potential of removing salts from seaweed-biochar, and the field soil application of seaweed and fly ash amended vermicomposts.

Modeling the effect of chemical additives on clay soil plasticity: novel analysis of oxide contributions in fly ash and cement treatments

Modeling the effect of chemical additives on clay soil plasticity: novel analysis of oxide contributions in fly ash and cement treatments

An Entrained Flow Biomass Gasification Technology with the Fluidized Bed Concept for Low-carbon Fuel Production

For accomplishing the vision of building of a net-emission zero society, low-carbon fuels such as e-fuel, Sustainable Aviation Fuel (SAF), and chemical products generation, plays a significant role. Especially, among the low carbon fuels, SAF is the most crucial. Ammonia and electric aircraft are under way as alternatives to fossil-derived jet fuel (kerosene). However, none of these have yet found their way to commercialization. Among the SAF production technology, biomass gasification and Fischer-Tropsch (FT) synthesis technology are one of the lowest CO2 emission processes, according to Life Cycle Assessment (LCA) analysis. However, at present there are some issues about biomass grinding, tar, ash treatment, gas purification and wastewater. We, at Mitsubishi Heavy Industries (MHI) R&D laboratory have developed entrained bed gasification, adopting the fluidized bed concept in which biomass particles are recirculated in the gasifier without fluidizer. Principally desired outcomes of this development was to reduce the grinding power, simplify the structure by using atmospheric pressure process, and lower tar concentration while maintain suitable temperature to prevent ash from melting inside gasifier. Empirical and actual results showed that the developed gasifier can obtain high carbon conversion ratio and low tar as compared to the traditional gasification processes for low-carbon fuel production and produce reliably stable syngas for low-carbon fuel synthesis with single gasifier. Based on the pilot plant operation results, effectiveness of moderate (1223 – 1323 K) temperature gasification with this concept has been demonstrated too. As a conclusion, development needs and expectation of gasification technology for contributing to carbon neutral society are mentioned.

Immobilization of heavy metals with chlorine and liquid phase formation during thermal treatment of MSWI fly ash

Due to effective detoxification, thermal treatment is a preferred treatment technology of municipal solid waste incineration (MSWI) fly ash. However, immobilization behavior of heavy metals during thermal treatment is unclear. In this work, a circulated fluidized bed fly ash with SiO2 addition and a grate furnace fly ash with high silica-aluminum coal ash addition were used to investigate combined effect of active chlorine content, liquid polymerization degree, temperature of initial liquid phase formation and liquid phase formation rate on the immobilization ratios of Zn, Pb and Cd by principle component analysis (PCA). The results show that the decrease in active chlorine content favors the immobilization of Zn, Pb and Cd because chlorination volatilization is reduced. Both the increase in liquid polymerization degree and the formation of initial liquid phase at low temperature promote the immobilization of Zn, Pb and Cd for physical encapsulation. However, a rapid formation of liquid phase is not favorable for the immobilization of Zn, Pb and Cd, because transfer of heavy metals between crystals and liquid phase is impeded by high viscosity of liquid phase during fusion. The results can provide a reference for how to achieve the immobilization of heavy metals by adjusting the chemical composition of MSWI fly ash during thermal treatment.

Response of Soil, Growth, and Biomass Properties of Lupin (Lupinus albus L.) to Wood ash and Sawdust

Two organic carbon resources (wood ash and sawdust) were applied in the study site to assess their profound effects on soil properties and growth and biomass properties of lupin (Lupinus albus L.). Because of their contribution to improving soil structure, enhanced water-holding capacity, and increased carbon sequestration. The experiments were conducted in mid-November 2022 at Grdarasha Research Station, College of Agricultural Engineering Sciences, Salahaddin University-Erbil, Iraq. The experiment includes two organic amendments (wood ash and sawdust) as a treatment and Control. Results showed that the application of wood ash and sawdust improved and raised the number of essential elements and heavy metals in the soil, which in turn boosted the ability of the roots to absorb nutrients. The highest germination percentage, plant height, and leaf number were observed in the ash treatment (95.00 %, 22.00 cm, and 21.22) respectively. The great values of fresh and dry shoot weight were found in sawdust treatment 63.78 and 14 g/plant) respectively. The effects of treatments were not significant on root length and fresh and dry root weights. The final findings showed that adding various forms of organic carbon could alter the chemical characteristics of the soil. This, in turn, might have a good impact on microbes, which can subsequently help plants grow by converting, solubilizing, and mobilizing soil nutrients. Furthermore, lupin plants appeared to be a form of phytoremediation, or absorption, for certain heavy metals.

Differential response by seedlings of three sub-boreal conifer species to high- and low-carbon wood ash amendment

In Canada, there is a need to implement value-added uses for wood ash (hereafter ash) generated from bioenergy facilities as most ash is landfilled. Ash application to forests can provide benefit via nutrient supply, amelioration of soil acidity and, sometimes, increased tree growth. However, information is limited on the response of conifer species to different wood ash types applied to fine-textured soil typical of north-central B.C. We conducted a 16-month seedling pot trial that examined the response of Douglas-fir ( Pseudotsuga menziesii), lodgepole pine ( Pinus contorta var. latifolia), and hybrid white spruce ( Picea glauca × engelmannii) to high- (HCA) and low-carbon ashes (LCA) applied (up to 10 Mg mineral matter ha−1 equiv.), with and without fertilizer N (200 kg N ha−1 equiv.), to fine-textured forest soil. Pine and spruce exhibited a 1.6- and 1.4-fold increase in shoot biomass at the high rate of HCA with fertilizer N. At study end, the high rate of LCA had the greatest soil pH, EC and total K in the upper forest floor, but the HCA had greater total B, P and Zn. LCA elicited increased foliar B in pine, but HCA increased foliar Ca in spruce when co-applied with fertilizer N. In general, Douglas-fir growth did not respond to ash treatments, and seedling mortality was observed in some LCA treatments. Ash treatments helped offset some nutrient deficiencies induced by N fertilization. Ash type influenced soil chemical as well as seedling growth and nutrition responses.

Mitigation of PBDE net discharge in hazardous waste thermal treatment system through reintroducion of sludge and fly ash into GASMILD operations

The presence of polybrominated diphenyl ethers (PBDEs) in consumer products, waste treatment processes, and treated ashes poses a significant environmental threat. Due to the lack of research on the removal of PBDEs during waste incineration, this study investigated the effectiveness of a Hazardous Waste Thermal Treatment System (HAWTTS) utilizing reburning of sludge and fly ash (SFA) with gasification-moderate or intense low-oxygen dilution (GASMILD) combustion for PBDE removal. The closed-loop treatment of sludge and ash within the HAWTTS provides a potential pathway for near-zero PBDE emissions. The GASMILD combustion addresses potential combustion issues associated with fly ash recirculation. The system achieved an impressive overall removal efficiency of 98.4% for PBDEs, with minimal stack emissions (2.45 ng/Nm³) and a negative net discharge rate (−1.02 μg/h). GASMILD combustion played a crucial role (92.7%–97.6% destruction) in addressing challenges associated with high-moisture feedstocks and SFA residues. Debromination of highly brominated PBDEs occurred within the incinerator, resulting in an increased proportion of lower brominated PBDEs in the bottom slag compared to the feedstock. Air Pollution Control Devices (APCDs) achieved a total PBDE removal efficiency of 74.4%. However, the hydrophobic nature of PBDEs limited removal efficiency in scrubbers (36.0%) and cyclonic demisters (37.86%). This study demonstrates that reintroducing SFA into the GASMILD combustion process offers an effective and environmentally sustainable strategy for reducing net PBDE levels in hazardous waste. This approach also provides additional benefits such as energy conservation, reduced carbon emissions, and lower operating costs associated with secondary treatment of thermally treated byproducts.

A sustainable mineral process for silicon and quartz recovery from quartz crucible waste ash via electrical separation

Driven by the explosive development of the photovoltaic (PV) industry, the treatment of the quartz crucible waste ash (QCWA) from monocrystalline silicon rod production must be considered to combat the shortage of silicon materials and promote sustainable development. In particular, the loss of grade 4 N high-purity silicon in QCWA is a frustrating fact for the silicon supply chain. In this work, an electrical separation process is proposed for the recovery of silicon and quartz from QCWA to realize waste resource reutilization. The charging processes and forces in the feed QCWA are first analyzed. Then, the electric field distribution during electrical separation is simulated to clarify the movement models of silicon and quartz particles and formulate reasonable electrical separation parameters. After systematic theoretical analysis, calculation, and simulation, electrical separation experiments were conducted. The results prove that the content of silicon in the concentrate and the corresponding content of quartz in the tailing respectively exceeded 93 % and 61 % under a particle size of 80 ∼ 120 mesh, a voltage of 40 kV, and a roll speed of 75 r/min. This work demonstrates that electrical separation is a sustainable process that could be recommended for silicon and quartz recovery from QCWA.

Effectiveness of Agricultural Waste Ashes in Controlling Sitophilus oryzae Infestation in Stored Rice Grains

In this study, the insecticidal effectiveness of agricultural waste ashes of sawdust, rice husk, groundnut shell, maize cob, and wheat straw against Sitophilus oryzae in stored rice grains was investigated. The research, conducted to assess grain damage, weight loss, and weevil perforation index caused by S. oryzae over intervals of 30, 60 and 90 days. The ashes were applied at a rate of 2 gm per 100 gm of grains. Over a 90-day period the untreated control exhibited the highest grain damage (33.80%) and weight loss (14.23%). Among ash treatments, sawdust ash resulted in the highest grain damage (18.40%) and weight loss (12.47%), whereas groundnut shell ash was the most effective, showing the lowest grain damage (12.87%) and weight loss (8.53%). The chemical insecticide Chlorpyrifos 48EC maintained complete protection with 0% grain damage and weight loss. The Weevil Perforation Index (WPI) was significantly lower in groundnut shell ash (9.27) compared to other ash treatments, emphasizing its effectiveness in preserving rice quality.

Influence of chemical treatment of fly ash on mechanical, thermal, and water absorption characteristics of PS/SBC nanocomposite

AbstractThe purpose of this study is to investigate the effective chemical treatment of fly Ash (FA) that affects the mechanical, thermal, and water absorption capabilities of polystyrene/styrene‐butadiene‐copolymer (PS/SBC) nanocomposites. NaOH, H2SO4 and distilled water have been employed to conduct the chemical treatment. Specimens have been prepared using injection molding technique. In order to evaluate the mechanical properties of the material, tensile, flexural, impact, and hardness tests were carried out. thermo‐gravimetric analysis (TGA) and differential thermal analysis (DTA) were employed to gain an understanding of the thermal behavior of the material. Furthermore, to determine the moisture resistance, water absorption experiments were conducted. Experimental results show that, alkali‐treated FA (AL‐FA) demonstrated the maximum values with an ultimate tensile strength of 26.68 MPa, acid‐treated FA (AC‐FA) composite exhibiting the highest flexural strength at 5 MPa whereas water‐treated FA (WA‐FA) composite led to better impact strength of 17.6 kJ/m2. TGA revealed that WA‐FA and AL‐FA composites experienced an 80% reduction in weight at 500°C, while AC‐FA composites exhibited weight reductions of 90%. The significance of treatment methods in interfacial interactions between the polymer and FA has been studied through morphological analysis. These findings provide valuable insights that can be applied to future research and industrial applications in the field of sustainable materials engineering.Highlights Polystyrene/Styrene‐Butadiene‐Copolymer composites were prepared with Fly ash (FA) filler. FA pre‐treated by NaOH (AL‐FA), H2SO4 (AC‐FA) and distilled water (WA‐FA). Injection molding technique was employed to prepare the ASTM standard samples. WA‐FA composite exhibited the highest ductility but lower tensile strength. TGA revealed that AC‐FA composites exhibited weight reductions of 90%.

Below ground chemical and microbial community responses of wood ash addition to a hardwood forest in central Ontario

The use of wood ash as a soil amendment remains restricted in many parts of Canada. To better understand belowground biogeochemical responses to wood ash, soil solution chemistry was measured over 3 years following the application of wood ash (0, 2.5, 5.0, and 7.5 Mg·ha−1) at a hardwood stand in Ontario, after which soil microbial response was assessed using 16S rRNA gene and internal transcribed spacer sequencing. Metal concentrations in the locally sourced wood ash were below provincial regulatory limits. Significant increases in soil solution pH were observed within the forest floor in the first year of the trial, and significant increases in calcium and magnesium were also observed in later years of the trial. Concentrations of most metals in soil water either decreased or exhibited no significant change in response to wood ash. There was an increase in diversity and richness of soil prokaryotic groups in the FH horizon at the highest wood ash treatment that is most likely linked to the large increase in pH. This study indicates that wood ash has a strong ameliorative effect on soil and soil water chemistry without major changes to soil microbial communities and is a viable amendment to forest soils at dosages below 5 Mg·ha−1.

Emission characteristics and control technology of heavy metals during collaborative treatment of municipal solid waste incineration fly ash in iron ore sintering process

Emission characteristics and control technology of heavy metals during collaborative treatment of municipal solid waste incineration fly ash in iron ore sintering process

The influence of the pre-addition of semi-dry and dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of MSWI fly ash

Incineration is a main way to dispose the municipal solid waste (MSW) in China, but municipal solid waste incineration (MSWI) fly ash will negatively impact the environment and human health as containing high content of heavy metals. This study aimed to investigate the influence of the pre-addition of dry/semi-dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of fly ash. This study has found that semi-dry slaked lime had more effect on the solidification rate of heavy metals in MSWI fly ash compared to the pre-addition of the dry slaked lime. As the dosage of semi-dry slaked lime increased, the solidification rate of Zn and Ba increased to 100 %, while the solidification rate of Cr decreased to as low as 0 %. However, the effect of the dosage of semi-dry slaked lime on the other heavy metals (Cu, Pb, Cd, Ni) showed a complex trend. This study underscores the importance of the pre-addition of slaked lime during the purification of flue gas in influencing subsequent chelation and solidification treatment of MSWI fly ash. It provides valuable insights into optimizing lime dosage to enhance heavy metal stabilization, contributing to more effective and sustainable waste management practices.

The cementitious properties of alkali-activated municipal solid waste incineration fly ash-phosphorus slag-secondary aluminum dross matrix composites and the mechanism of solidification of heavy metals

Based on the purpose of safe and resourceful disposal of hazardous waste, this paper proposes a new method for the combined treatment of municipal solid waste incineration fly ash (MSWIFA), phosphorus slag (PS), and secondary aluminum dross (SAD). A novel alkali-activated binder was synthesized by orthogonal experimental design, and the strength formation mechanism of the binder and the solidification and stabilization (S/S) mechanism of heavy metals were revealed. The results show that the maximum strength of the sample at 60 d is 22.4 MPa. The addition of SAD will affect the development of the strength of the solidified body and the types of hydration products of the gel. The hydration products of the solidified body are mainly calcium silicate hydrate (C-S-H), calcium aluminosilicate hydrate (C-A-S-H), and calcium alumina (AFt). The solidified body of alkali-activated cementitious material has a good S/S effect on heavy metals, and its solidification efficiency is Zn > Cd > Pb > Cu > Ni > As > Cr. The maximum solidification rates of Zn, Pb, and Cd were 99.97 %, 97.90 %, and 99.68 %, respectively. At the same time, the leaching concentration of various heavy metals meets the threshold requirements stipulated by relevant international norms and has good environmental safety.

Study on preparing sustainable limestone calcined clay cement (LC3) through CO2-active treatment of municipal solid waste incineration fly ash (IFA)

Municipal solid waste incineration fly ash (IFA) is theoretically more suitable for forming a composite cementitious system with cement and calcined clay compared to inert limestone due to its pozzolanic activity. In addition, IFA contains high levels of alkaline calcium compounds that have the potential for carbonation. The study examined the improvement of CaCO3 content within IFA facilitated by CO2-active (CIFA), replacing limestone in limestone calcined clay cement (LC3), and creating sustainable cementitious materials. The hydration behavior, heavy metal morphologies and mechanical properties of (C)FC3 were studied. The research indicates that introducing IFA adversely affects the initial hydration process of the system, but this inhibition is alleviated by using CIFA. This is facilitated by the reduction in sulfate dissolution rate attributed to the formation of carbonate shells. The incorporation of IFA into the system leads to the effective utilization of Ca(OH)2, thereby enhancing the pozzolanic reaction of the calcined clay. Consequently, (C)FC3 show higher compressive strength than LC3 at 56 d, with L15, F15 and CF15 achieving 29.9 MPa, 39.6 MPa and 46.8 MPa, respectively. While there is an increase in the exchangeable and acid-soluble states in CFC3, the elevation of oxidizable and residual states contributes to a reduced potential for total leaching in harsh environments. The excellent mechanical properties and environmental stability confirm the feasibility of using (C)IFA for LC3.