We examined the mechanical strength and microscopic property effects of bottom ash(BA)recycled concrete made by partially substituting natural aggregates made from three industrial wastes,fly ash(FA),silica fume(SF),f...We examined the mechanical strength and microscopic property effects of bottom ash(BA)recycled concrete made by partially substituting natural aggregates made from three industrial wastes,fly ash(FA),silica fume(SF),furnace slag(FS),and cement after BA was treated with slurry to improve the properties of BA and increase its utilisation.The compressive,flexural,splitting tensile strengths,and drying shrinkage test of the recycled concrete from BA were tested at the macroscopic level,and the specimens were analyzed by scanning electron microscopy(SEM)at the microscopic level.The experimental results show that the slurry treatment of BA results in a corresponding improvement in the macroscopic and microscopic properties of the obtained slurry-bound BA aggregates.The synergistic effect of FA and SF can better fill the pores on the surface of BA,which in turn can better improve the properties of recycled concrete.This study provides a theoretical support for improving the properties of BA and promoting its utilisation as a resource.展开更多
The construction of coastal areas generates a substantial volume of waste marine clay(WMC),which poses environmental and safety challenges during the stockpiling process.The improved preparation of WMC as roadbed mate...The construction of coastal areas generates a substantial volume of waste marine clay(WMC),which poses environmental and safety challenges during the stockpiling process.The improved preparation of WMC as roadbed materials emerges as a crucial pathway for resource utilization.However,the engineering performance and durability of roadbed materials prepared from WMC have always been a concern for scholars and engineers.This study employs alkali-activated ground granulated blast-furnace slag(GGBFS)and municipal solid waste incineration bottom ash(MSWIBA)to solidify WMC for preparation of the roadbed materials.The results showed that the combined utilization of alkali-activated GGBFS and MSWIBA to improve WMC can meet the environmental and mechanical requirements of roadbed materials.The incorporation of 5e20%MSWIBA could improve the water stability coefficient and California bearing ratio to more than 85%and 80%,respectively.The durability of roadbed material was significantly improved by addition of MSWIBA.After 12 dryewet cycles,the strength of the material without MSWIBA and with 5%MSWIBA was 0 and 2.87 MPa,respectively.Following analysis of engineering properties and durability,the optimal dosage of MSWIBA was determined to be 5%.The enhanced durability can be attributed to the optimization of material gradation and pore structure achieved through the incorporation of a small quantity of MSWIBA.The carbon emission and normalized global warming potentials of roadbed material treated by MSWIBA and GGBFS were much lower than that of cementitious binders such as ordinary Portland cement.These findings indicate that MSWIBA has the potential to substitute natural aggregates like sand and gravel,effectively improving the durability of roadbed materials and promoting the safe and efficient recycling of solid waste resources.展开更多
Bottom ash is the major by-product of municipal solid waste incineration（MSWI）, and is often reused as an engineering material, such as road-base aggregate. However, some metals（especially aluminum） in bottom ash ...Bottom ash is the major by-product of municipal solid waste incineration（MSWI）, and is often reused as an engineering material, such as road-base aggregate. However, some metals（especially aluminum） in bottom ash can react with water and generate gas that could cause expansion and failure of products containing the ash; these metals must be removed before the ash is utilized. The size distribution and the chemical speciation of metals in the bottom ash from two Chinese MSWI plants were examined in this study, and the recovery potential of metals from the ash was evaluated. The metal concentrations in these bottom ashes were lower than that generated in other developed countries. Specifically, the contents of Al,Fe, Cu and Zn were 18.9–29.2, 25.5–32.3, 0.7–1.0 and 1.6–2.5 g/kg, respectively. Moreover,44.9–57.0 wt.% of Al and 55.6–75.4 wt.% of Fe were distributed in bottom ash particles smaller than 5 mm. Similarly, 46.6–79.7 wt.% of Cu and 42.9–74.2 wt.% of Zn were concentrated in particles smaller than 3 mm. The Fe in the bottom ash mainly existed as hematite, and its chemical speciation was considered to limit the recovery efficiency of magnetic separation.展开更多
Municipal solid waste incineration products of bottom ash(BA),fly ash(FA),and pickling sludge(PS),causing severe environ-mental pollution,were transformed into glass ceramic foams with the aid of CaCO3 as a pore-foami...Municipal solid waste incineration products of bottom ash(BA),fly ash(FA),and pickling sludge(PS),causing severe environ-mental pollution,were transformed into glass ceramic foams with the aid of CaCO3 as a pore-foaming agent during sintering.The effect of the BA/FA mass ratio on the phase composition,pore morphology,pore size distribution,physical properties,and glass structure was investigated,with results showing that with the increase in the BA/FA ratio,the content of the glass phase,Si-O-Si,and Q3Si units decrease gradually.The glass transmission temperature of the mixture was also reduced.When combined,the glass viscosity decreases,causing bubble coalescence and uneven pore distribution.Glass ceramic foams with uniform spherical pores are fabricated.When the content of BA,FA,and PS are 35wt%,45wt%,and 20wt%,respectively,contributing to high performance glass ceramic foams with a bulk density of 1.76 g/cm3,porosity of 56.01%,and compressive strength exceeding 16.23 MPa.This versatile and low-cost approach provides new insight into synergistically recycling solid wastes.展开更多
This research evaluated the use of sewage sludge and refuse incineration bottom ash to replace calcium sulfoaluminate cement （CSA） in making controlled low-strength material （CLSM）. Various properties of CLSM mixt...This research evaluated the use of sewage sludge and refuse incineration bottom ash to replace calcium sulfoaluminate cement （CSA） in making controlled low-strength material （CLSM）. Various properties of CLSM mixtures were characterized in terms of unconfined compressive strength, microstructure and leachability. It was found that the strength of tested CLSM mixtures ranged from 3.6 to 9.0 MPa, over the upper excavatable limit of 2.1 MPa. The micro-structural analysis revealed that sewage sludge and bottom ash were crystallochemically in- corporated within CLSM system_s by forming the needle-like ettringite （C3A＇3CS＇_H32） with exiguous tu.bers via the typical Pozzolanic Reaction, leading to a dense and low-porosity microst;＇ucture. Furthermore,-the toxicity characteristic leaching procedure evidenced that the cumulative leachable metals in the leachate were much below the regulatory thresholds. The potential for us!ng sewage sludge and bottom ash!n CLSM makin.g was thus confirmed.展开更多
The bottom ash and fly ash from the co-combustion of wood residues and peat at a bubbling fluidised bed boiler（296 MW） contained only quartz（SiO_2）, microcline（KAl Si_3O_8） and albite（NaAlSi_3O_8）. Thus, X-ray...The bottom ash and fly ash from the co-combustion of wood residues and peat at a bubbling fluidised bed boiler（296 MW） contained only quartz（SiO_2）, microcline（KAl Si_3O_8） and albite（NaAlSi_3O_8）. Thus, X-ray powder diffraction（XRD） was not useful for clarifying the difference in the release of associated heavy metals from ash matrices. In order to assess the release of heavy metals from ashes under changing environmental conditions, they were sequentially extracted and fractionated by the BCR-procedure into acid soluble/exchangeable（CH_3COOH）, reducible（NH_2OH-HCl） and oxidizable（H_2O_2/CH_3COONH_4） phases. The CH_3 COOH extractable fraction in conjunction with the total heavy metals concentrations were used to calculate the risk assessment code values for heavy metals leaching from the ash matrix. The leaching studies indicate that the heavy metals in the bottom ash and fly ash are bound to different fractions with different strengths. From the environmental and utilization perspectives, heavy metals in ashes posed different levels of environmental contamination risk. Only As in the bottom ash posed a very high risk. High risk metals were Cd in the bottom ash as well as As, Cd and Se in the fly ash.展开更多
Fly and bottom ash(FABA)produced primarily from coal combustion in a coal-fred power plant consists of fne particles of the organic and inorganic mixture and trace elements.Eight FABA samples from coal-fred power plan...Fly and bottom ash(FABA)produced primarily from coal combustion in a coal-fred power plant consists of fne particles of the organic and inorganic mixture and trace elements.Eight FABA samples from coal-fred power plants in Java,Indonesia,had been collected for composition and rare earth element and Yttrium(REY)mode of occurrence identifcation.The geochemical composition of both major and trace elements was determined by inductively coupled plasma-mass spectrometry/atomic emission spectrometry(ICP-MS/AES).Furthermore,the composition of FABA was identifed by petrography with refected light microscopy and X-ray difraction(XRD)analysis.Simultaneously,scanning electron microscope determines the mode of occurrence of REY with an energy-dispersive X-ray(SEM–EDX).The study fnds that the inorganic component of FABA consists of glass,Fe–Mg spinel,mullite,quartz,Fe-oxide mineral,and K-feldspar.In contrast,the organic component is dominated by unburned coal.Glass is the most abundant component with cenospheres as major and pleiospheres as minor constituents.Trace elements analysis indicates REY concentration with heavy REY(HREY)distribution pattern.Moreover,SEM–EDX analysis results show that Yttrium(Y)occurs in glass and has a low concentration in spinel.From the mode occurrence of REY,in particular Yttrium,it can be predicted that alkaline fusion followed by acid leaching will be the most appropriate extraction method to extract REY from Indonesian FABA.展开更多
The curing sensitivity of concrete with cement Types 1, 3, and 5 as well as multiple powders consisting of cement, fly ash, and limestone powder was studied. Bottom ash was also used in the study as an internal curing...The curing sensitivity of concrete with cement Types 1, 3, and 5 as well as multiple powders consisting of cement, fly ash, and limestone powder was studied. Bottom ash was also used in the study as an internal curing agent and a partial substi- tution of fine aggregate. The curing sensitivity index was calculated by considering the performances of compressive strength and carbonation depth. Specimens were subjected to two curing conditions： continuously water-cured and continuously air-cured. The results show that cement Type 3 has a lower curing sensitivity, while cement Type 5 increases the curing sensitivity. For the mixes without bottom ash, the use of fly ash increases the curing sensitivity, while limestone powder reduces the curing sen- sRivity of concrete. The use of bottom ash in concrete reduces the curing sensitivity, especially at a lower mass ratio of water to binder. Concrete with limestone powder, together with bottom ash, is least sensitive to curing. The curing sensitivity calculated from carbonation depth also has a similar tendency as that derived by considering compressive strength. From the test results of compressive strength and curing sensitivity, bottom ash has been proven to be an effective internal curing agent.展开更多
The radioactivity of uranium in radioactive coal bottom ash（CBA） may be a potential danger to the ambient environment and human health. Concerning the limited research on the distribution and mode of occurrence of u...The radioactivity of uranium in radioactive coal bottom ash（CBA） may be a potential danger to the ambient environment and human health. Concerning the limited research on the distribution and mode of occurrence of uranium in CBA, we herein report our investigations into this topic using a number of techniques including a five-step Tessier sequential extraction, hydrogen fluoride（HF） leaching, Siroquant（Rietveld） quantification, magnetic separation, and electron probe microanalysis（EPMA）. The Tessier sequential extraction showed that the uranium in the residual and Fe–Mn oxide fractions was dominant（59.1%and 34.9%, respectively）. The former was mainly incorporated into aluminosilicates,retained with glass and cristobalite, whereas the latter was especially enriched in the magnetic fraction, of which about 50% was present with magnetite（Fe_3O_4） and the rest in other iron oxides. In addition, the uranium in the magnetic fraction was 2.6 times that in the non-magnetic fraction. The experimental findings in this work may be important for establishing an effective strategy to reduce radioactivity from CBA for the protection of our local environment.展开更多
Similar to chromium contamination, the environmental contamination caused by uranium in radioactive coal bottom ash（CBA） is primarily dependent on the chemical speciation of uranium. However, the relationship betwee...Similar to chromium contamination, the environmental contamination caused by uranium in radioactive coal bottom ash（CBA） is primarily dependent on the chemical speciation of uranium. However, the relationship between uranium speciation and environmental contamination has not been adequately studied. To determine the relationship between uranium speciation and environmental contamination, X-ray absorption fine structure（XAFS） and X-ray photoelectron spectra（XPS） analyses were performed to determine the uranium speciation in CBA exposed to different chemical environments and simulated natural environments. The leachability of the different forms of uranium in the CBA was studied via a simulated acid rain leaching experiment, and the results showed that 57.0% of the total uranium was leached out as U（VI）. The results of a linear combination fit（LCF）of the X-ray absorption near edge structure（XANES） spectrum revealed that in the raw CBA, the uranium mainly occurred as U_3O_8（71.8%）. However, in the iron-rich particles, the uranium mainly occurred as UO_2（91.9%） after magnetic separation. Magnetite is a ubiquitous ferrousbearing oxide, and it was effective for the sorption of U（IV）. The result of FeSO_4 leaching experiment indicated that 96.57% of total uranium was reduced from U（VI） to U（IV） when infiltrated with the FeSO_4 solution for 6 months. This result clearly demonstrated the changes in chemical valence of uranium in the coal ash and provided a conceptual principle for preventing uranium migration from ash to the surrounding soil and plants.展开更多
In tropical regions,heavy rainfall induces erosion and shallow landslides on road embankments.Cement-based stabilization methods,common in these regions,contribute to climate change due to their high carbon footprint....In tropical regions,heavy rainfall induces erosion and shallow landslides on road embankments.Cement-based stabilization methods,common in these regions,contribute to climate change due to their high carbon footprint.This study explored the potential application of coir fiber-reinforced laterite soil-bottom ash mixtures as embankment materials in the tropics.The objective is to enhance engineered embankment slopes'erosion resistance and stability while offering reuse options for industrial byproducts.This study examined various mix designs for unconfined compressive strength(UCS)and permeability,utilizing 30%bottom ash(BA)and 1%coir fiber(CF)with varying sizes ranging from 10 to 40 mm,6%lime,and laterite soil(LS),followed by microstructural analyses.The results demonstrate that the compressive strength increases as the CF length increases to 25 mm.In contrast,permeability increases continuously with increasing CF length.Lime-treated mixtures exhibit superior short-and long-term strength and reduce permeability owing to the formation of cementitious materials,as confirmed by microstructural analyses.A lab-scale slope box was constructed to evaluate the surface erosion of the stabilized laterite soil embankment.Based on the rainfall simulation results,the LS-BA-CF mixtures show better resistance to erosion and deformation compared to untreated LS,especially when lime is added to the top layer.This study provides insights into a sustainable and cost-effective approach for slope stabilization using BA and CF,offering a promising solution for tropical regions susceptible to surface erosion and landslides.展开更多
The destruction of concrete building materials in severely cold regions of the north is more severely affected by freeze-thaw cycles,and the relationship between the mechanical properties and pore structure of concret...The destruction of concrete building materials in severely cold regions of the north is more severely affected by freeze-thaw cycles,and the relationship between the mechanical properties and pore structure of concrete with fine aggregate from municipal solid waste(MSW)incineration bottom ash after freeze-thaw cycles is analyzed under the degree of freeze-thaw hazard variation.In this paper,the gray correlation method is used to calculate the correlation between the relative dynamic elastic modulus,compressive strength,and microscopic porosity parameters to speculate on the most important factors affecting their changes.The GM(1,1)model was established based on the compressive strength of the waste incineration ash aggregate concrete,the relative error between the simulated and actual values in the model was less than 5%,and the accuracy of the model was level 1,indicating that the GM(1,1)model can well reflect the change in the compressive strength of the MSW incineration bottom ash aggregate concrete during freeze-thaw cycles.Using the gray correlation method,the correlation between the relative dynamic elastic modulus,compressive strength,air content,specific surface area,pore spacing coefficient,and pore average chord length was calculated,and the pore spacing coefficient and pore average chord length were determined to be highly correlated with each other.This determination can help analyze and infer the deterioration mechanism of concrete subject to freeze-thaw cycles.These results can provide a theoretical basis for guiding the engineering practice of concrete with fine aggregates of household bottom ash in the northern cold region.展开更多
Three fresh China coals （lignitie, bituminite and anthracite） from different geological origin and the corresponding fly and bottom ashes were studied by room temperature（RT） Mossbauer spectroscopy（MS）. The iron...Three fresh China coals （lignitie, bituminite and anthracite） from different geological origin and the corresponding fly and bottom ashes were studied by room temperature（RT） Mossbauer spectroscopy（MS）. The iron-bearing minerals were characterized to be mainly pyrite in all coal samples by the hyperfine parameters.Suphate（FeSO4·nH2O） was found in bituminite and anthracite coal.The MSssbauer spectra of the fly and bottom ashes as a result of pulverised coal combustion（PCC） in Xiaolongtan,Shuicheng and Luohuang Power Plants are comprised of superimposed sextets and doulets of oxides includes maghemite（γ-Fe2O3）, magnitite（Fe3O4）, haematite（α-Fe2O3）, magnesioferite （MgFe2O4）, Fe^3＋/Fe^2＋ -mullite, Fe^3＋ -glass silicate and metallic iron. The studies also show that iron-bearing minerals in coals are largely dependant on geological regions and coal rank, the composition of the corresponding fly and bottom ashes will not only depend on the type and mineralogy of the feed coal but also on the local nature of combustion.展开更多
Medical waste incinerators emit a wide range of pollutants like heavy metals, dioxins and furans. These include Pb （lead）, Hg （mercury）, Cd （cadmium）, fine dust particles and PICs （products of incomplete combus...Medical waste incinerators emit a wide range of pollutants like heavy metals, dioxins and furans. These include Pb （lead）, Hg （mercury）, Cd （cadmium）, fine dust particles and PICs （products of incomplete combustion）. The objective was to determine the elemental composition of medical waste residue after incineration in selected hospitals in Kiambu County, Kenya. Bottom/fly ash samples were collected from the burners/incinerators in the selected health care facilities visited. The concentrations of the metals in the fly ash and bottom ash were determined using an XRF （X-ray fluorescence） spectrometer after acid digestion. The concentrations of heavy metals in the fly and bottom ash were as follows： Ti （titanium） 62-839 mg·kg^-1 and a mean of 202 mg·kg^-1 and 344 mg·kg^-1 in fly ash and bottom ash, respectively. Ca （calcium） was 37,753-204,475 mg.kg1 with means of 27,132 mg.kg-1 in fly ash and 131,185 mgg·kg^-1 in bottom ash. Zn （zinc） was 297-6,605 mg·kg^-1 with means （2,307 mg·kg^-1 in fly ash, 4,359 mg·kg^-1 in bottom ash）, Pb （13-1,819 mg·kg^-1） had means of 280 mg·kg^-1 in fly ash and 291 mg-kg-1 in bottom ash. Cu （copper） （9.5-250 mg·kg^-1） had means of 83.47 mg·kg^-1 in fly ash and 98.8 mg·kg^-1 in bottom ash. The wide variations in results can be attributed to the different burners/incinerators used and different segregation methods of the medical waste. The results show that the reported levels of heavy metals could pose a health risk due to possible leaching after disposal.展开更多
Bottom ash. a power plant waste, was used to adsorb acid orange 7. The adsorption of acid orange 7 in aqueous solutions onto bottom ash was studied as functions of particle size. dosage, initial concentration and agit...Bottom ash. a power plant waste, was used to adsorb acid orange 7. The adsorption of acid orange 7 in aqueous solutions onto bottom ash was studied as functions of particle size. dosage, initial concentration and agitation time by batch experiments. Under conditions of bottom ash dosage of 1.5 g/50 ml and 5 g/50 ml for 〈0.074 mm and 0.074 mm-0.2 mm of bottom ash, respectively, it could achieve 99.1% and 87.6% dye removal efficiency. The adsorption isotherms for the bottom ash could be well described by both Freundlich and Langmuir isotherms. The calculated dye adsorption capacities of bottom ash for the particle size of 0.074 mm -0.2 mm and 〈0.074 mm were 2.78 mg/g and 10.21 mg/g, respectively. The results indicated that the dye uptake process fitted to the pseudo-first-order kinetic model better than the pseudo-second-order. The data were also fitted to intraparticle diffusion model by two adsorption stages, due to the difference in rate of mass transfer in the initial and final stages of adsorption. Significant variations were observed in the FTIR spectra and Stem photographs of bottom ash after adsorption. The column parameters were calculated by breakthrough curves at different flow rates and bed depths.展开更多
In this study, SCM （supplementary cementitious materials）, such as nano silica, micro silica, fly ash and bottom ash, have been evaluated for optimal level of replacement as blending material in cement and concrete....In this study, SCM （supplementary cementitious materials）, such as nano silica, micro silica, fly ash and bottom ash, have been evaluated for optimal level of replacement as blending material in cement and concrete. The physical and chemical properties of the above materials were first analyzed. This study focused on compressive strength of concrete with different mixes at different ages. In many cases, products made with fly ash, micro silica, nano silica and bottom ash perform better than products made without them. Test results obtained in this study indicate that up to 5% nano silica, 10% micro silica, 20-30% fly ash and 10% bottom ash could be advantageously blended with cement without adversely affecting the strength. However, optimum levels of these materials are 1-3% nano silica, 3-8% micro silica, 10% fly ash and 5% of bottom ash when we consider the strength of concrete. All percentages are defined by weight unless otherwise mentioned.展开更多
It is well known that the finer particle of cementing material has more pozzolanic reaction than the coarser. This paper investigates the shear properties of geocomposite soil with various particle sizes of bottom ash...It is well known that the finer particle of cementing material has more pozzolanic reaction than the coarser. This paper investigates the shear properties of geocomposite soil with various particle sizes of bottom ash. The geocomposite soil （GCS） in this study consists of dredged soil, bottom ash and cement for recycling dredged soil and bottom ash. Three different particle sizes of bottom ash passing No. 4 sieve, No. 40 sieve, and No. 140 sieve were added into soil mixtures, namely as GCS 4, GCS 40, and GCS 140, respectively. These bottom ashes have the same chemical component except for different particle sizes. Several mixtures were prepared with various contents of bottom ash ranging from 0 to 100% at 50% intervals by the weight of dry dredged soil. In this study, several series of unconfined compression test were carried out on the mixtures with various curing times. It is found that the unconfined compressive strength is a function of curing time and bottom ash content. For the curing time less than 28 days, the GCS 4 has higher unconfined compressive strength than the GCS 40 and GCS 140 due to the interlocking effect and friction between the particles with angular shape of coarse bottom ash. For the curing time larger than 28 days, the GCS 140 has higher strength due to the pozzolanic reaction. However, the ratios of secant modulus to unconfined compressive strength of three mixtures are almost the same, and in range of （46-100）, regardless of mixing condition and curing time.展开更多
In this paper, the mechanical and thermal properties of a sand-clay ceramic with additives coal bottom ash (CBA) waste from incinerator coal power plant are investigated to develop an alternative material for thermal ...In this paper, the mechanical and thermal properties of a sand-clay ceramic with additives coal bottom ash (CBA) waste from incinerator coal power plant are investigated to develop an alternative material for thermal energy storage (TES). Ceramic balls are developed at 1000°C and 1060°C using sintering or firing method. The obtained ceramics were compressed with a compression machine and thermally analyse using Decagon devise KD2 Pro thermal analyser. A muffle furnace was also used for thermal cycling at 610°C. It was found that the CBA increased the porosity, which resulted in the increase of the axial tensile strength reaching 3.5 MPa for sand-clay and ash ceramic. The ceramic balls with the required tensile strength for TES were selected. Their volumetric heat capacity, and thermal conductivity range respectively from 2.4075 MJ·m-3·°C-1 to 3.426 MJ·m-3·°C-1 and their thermal conductivity from 0.331 Wm-1·K-1, to 1.014 Wm-1·K-1 depending on sand origin, size and firing temperature. The selected formulas have good thermal stability because the most fragile specimens after 60 thermal cycles did not present any cracks. These properties allow envisioning the use of the ceramic balls developed as filler material for thermocline thermal energy storage (structured beds) in Concentrating Solar Power plants. And for other applications like solar cooker and solar dryer.展开更多
Health-care waste contains potentially harmful microorganisms and compounds which can infect and affect hospital patients, healthcare workers, the general public and environment. Therefore, management of health care w...Health-care waste contains potentially harmful microorganisms and compounds which can infect and affect hospital patients, healthcare workers, the general public and environment. Therefore, management of health care waste requires safe handling, treatment and disposal procedures. While incineration reduces the volume and quantity of waste for final disposal, it leads to the production of fly and bottom ashes laden with toxic incomplete combustion products such as Polycyclic Aromatic Hydrocarbons (PAHs), dioxins, furans and heavy metals. This exposes workers who handle and dispose the bottom ashes, hospital patients, the general public and environment. The goal of this study was to determine the total and individual levels of 16 most prevalent and toxic PAHs. Bottom ash samples were collected from incinerators in five county hospitals in Kenya, namely;Moi-Voi, Narok, Kitale, Makindu and Isiolo. Bottom ash samples were collected over a period of six months from the five hospitals. The samples were then sieved, homogenised and stored at 4°C in amber coloured glass containers. The PAHs were extracted using 30 ml of a hexane-acetone solvent (1:1) mixture by ultrasonication at room temperature (23°C) for 45 minutes. The PAHs were then analyzed with a GC-MS spectrophotometer model (Shimadzu GCMS-QP2010 SE) connected to a computer work station was used for the PAHs analysis. The GC-MS was equipped with an SGE BPX5 GC capillary column (30 m × 0.25 mm × 0.25 μm) for the separation of compounds. Helium was used as the carrier gas at a flow rate of 15.5 ml/minute and 14.5 psi. 1 μl of the sample was injected at 280°C, split mode (10:1). The oven programming was set for a total runtime of 40 minutes, which included: 100°C (2-minute hold);10°C /min rise to 200°C;7°C /min rise to 249°C;3°C /min rise to 300°C (2-minute hold). The interface temperature was set at 290°C. Analysis was done in Selected Ion Monitoring (SIM) mode and the peak areas of each of the PAHs were collected from the chromatograph and used for quantification of the 16 PAHs listed by the U.S. Environmental Protection Agency (EPA) which included, BaA (benz[a]anthracene: 4 rings), BaP (benzo[a]pyrene: 5 rings), BbF (benzo [b]fluoranthene: 5 rings), BkF (benzo[k]fluoranthene: 5 rings), Chr (chrysene: 4 rings), DbA (dibenz[a,h]anthracene: 5 rings), InP (indeno[1,2,3 - cd] pyrene: 6 rings) and Acp (acenaphthene: 3 rings), Acpy (acenaphthylene: 3 rings), Ant (anthracene: 3 rings), BghiP (benzo[g,h,i]perylene: 6 rings), Flu (fluorene: 3 rings), FluA (fluoranthene: 4 rings), Nap (naphthalene: 2 rings), PhA (phenanthrene: 3 rings) and Pyr (pyrene: 4 rings). Ion source-interface temperature was set at 200°C - 250°C. Internal standards from Sigma Aldrich were used in the analysis and the acquired mass spectra data were then matched against the NIST 2014 library [1] [2]. The mean PAHs concentration in the bottom ashes of each hospital varied broadly from 0.001 mg/kg to 0.4845 mg/kg, and the mean total concentration levels of individual PAHs ranged from 0.0072 mg/kg to 1.171 mg/kg. Low molecular weight PAHs (Phenanthrene, Naphthalene and Fluorene) were predominant in all the hospital wastes whereas Kitale and Narok presented the lowest PAHs concentrations and the lowest number of individual PAHs. Moi/Voi recorded the highest total PAHs concentration at 1.3129 ± 0.0023 mg/kg from a total of 11 PAHs being detected from the bottom ash samples. Narok had only three PAHs being detected at very low concentrations of 0.0041 ± 0.00 mg/kg, 0.0076 ± 0.00 mg/kg and 0.012 ± 0.00 mg/kg for phenanthrene, anthracene and chrysene respectively. This study presents hospital incinerator bottom ash as containing detectable levels of both carcinogenic and non-carcinogenic PAHs. Continued unprotected exposure of hospital workers (waste handlers) to the bottom ash PAHs could be hazardous to their health because of their cumulative effect. Preventive measures e.g. the use of Personal protective equipment (PPE) should be prioritised to minimise direct contact with the bottom ash. The study recommends an upgrade on incinerator technology for efficient combustion processes thus for better pollution control.展开更多
Healthcare wastes contain potentially harmful microorganisms, inorganic and organic compounds that pose a risk to human health and the environment. Incineration is a common method employed in healthcare waste manageme...Healthcare wastes contain potentially harmful microorganisms, inorganic and organic compounds that pose a risk to human health and the environment. Incineration is a common method employed in healthcare waste management to reduce volume, quantity, toxicity as well as elimination of microorganisms. However, some of the substances remain unchanged during incineration and become part of bottom ash, such as heavy metals and persistent organic pollutants. Monitoring of pollution by heavy metals is important since their concentrations in the environment affect public health. The goal of this study was to determine the levels of Copper (Cu), Zinc (Zn) Lead (Pb), Cadmium (Cd) and Nickel (Ni) in the incinerator bottom ash in five selected County hospitals in Kenya. Bottom ash samples were collected over a period of six months. Sample preparation and treatment were done using standard methods. Analysis of the heavy metals were done using atomic absorption spectrophotometer, model AA-6200. One-Way Analysis of Variance (ANOVA) was performed to determine whether there were significant differences on the mean levels of Cu, Zn, Pd, Cd and Ni in incinerator bottom ash from the five sampling locations. A post-hoc Tukey’s Test (HSD) was used to determine if there were significant differences between and within samples. The significant differences were accepted at p ≤ 0.05. To standardize the results, overall mean of each metal from each site was calculated. The metal mean concentration values were compared with existing permissible levels set by the WHO. The concentrations (mg/kg) were in the range of 102.27 - 192.53 for Cu, Zn (131.68 - 2840.85), Pb (41.06 - 303.96), Cd (1.92 - 20.49) whereas Ni was (13.83 - 38.27) with a mean of 150.76 ± 77.88 for Copper, 131.66 ± 1598.95 for Zinc, 234.60 ± 262.76 for Lead, 12.256 ± 10.86 for Cadmium and 29.45 ± 18.24 for Nickel across the five sampling locations. There were significant differences between levels determined by one-way ANOVA of Zn (F (4, 25) = 6.893, p = 0.001, p ≤ 0.05) and Cd (F (4, 25) = 5.641, p = 0.02) and none with Cu (F (4, 25) = 1.405, p = 0.261, p ≤ 0.05), Pb (F (4, 25) = 1.073, p = 0.391, p ≤ 0.05) and Ni (F (4, 25) = 2.492, p = 0.069). Results reveal that metal content in all samples exceed the WHO permissible levels for Cu (100 mg/kg), while those for Ni were below the WHO set standards of 50 mg/kg. Levels of Zn in three hospitals exceeded permissible level of 300 mg/kg while level of Pb exceeded WHO set standards of 100 mg/kg in two hospitals. Samples from four hospitals exceeded permissible level for Cd of 3 mg/kg. This study provides evidence that incinerator bottom ash is contaminated with toxic heavy metals to human health and the environment. This study recommends that hospitals should handle the bottom ash as hazardous wastes and there is need to train and provide appropriate personal protective equipment to healthcare workers, waste handlers, and incinerator operators and enforce compliance to existing regulation and guidelines on healthcare waste management to safeguard the environment and human health.展开更多
基金Funded by the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(No.SKLGP2022Z001)。
文摘We examined the mechanical strength and microscopic property effects of bottom ash(BA)recycled concrete made by partially substituting natural aggregates made from three industrial wastes,fly ash(FA),silica fume(SF),furnace slag(FS),and cement after BA was treated with slurry to improve the properties of BA and increase its utilisation.The compressive,flexural,splitting tensile strengths,and drying shrinkage test of the recycled concrete from BA were tested at the macroscopic level,and the specimens were analyzed by scanning electron microscopy(SEM)at the microscopic level.The experimental results show that the slurry treatment of BA results in a corresponding improvement in the macroscopic and microscopic properties of the obtained slurry-bound BA aggregates.The synergistic effect of FA and SF can better fill the pores on the surface of BA,which in turn can better improve the properties of recycled concrete.This study provides a theoretical support for improving the properties of BA and promoting its utilisation as a resource.
基金supported by the National Key Research and Development Program(Grant No.2023YFC3707802)National Natural Science Foundation of China(Grant No.42107185)International Partnership Program of Chinese Academy of Sciences(Grant No.115242KYSB20200002).
文摘The construction of coastal areas generates a substantial volume of waste marine clay(WMC),which poses environmental and safety challenges during the stockpiling process.The improved preparation of WMC as roadbed materials emerges as a crucial pathway for resource utilization.However,the engineering performance and durability of roadbed materials prepared from WMC have always been a concern for scholars and engineers.This study employs alkali-activated ground granulated blast-furnace slag(GGBFS)and municipal solid waste incineration bottom ash(MSWIBA)to solidify WMC for preparation of the roadbed materials.The results showed that the combined utilization of alkali-activated GGBFS and MSWIBA to improve WMC can meet the environmental and mechanical requirements of roadbed materials.The incorporation of 5e20%MSWIBA could improve the water stability coefficient and California bearing ratio to more than 85%and 80%,respectively.The durability of roadbed material was significantly improved by addition of MSWIBA.After 12 dryewet cycles,the strength of the material without MSWIBA and with 5%MSWIBA was 0 and 2.87 MPa,respectively.Following analysis of engineering properties and durability,the optimal dosage of MSWIBA was determined to be 5%.The enhanced durability can be attributed to the optimization of material gradation and pore structure achieved through the incorporation of a small quantity of MSWIBA.The carbon emission and normalized global warming potentials of roadbed material treated by MSWIBA and GGBFS were much lower than that of cementitious binders such as ordinary Portland cement.These findings indicate that MSWIBA has the potential to substitute natural aggregates like sand and gravel,effectively improving the durability of roadbed materials and promoting the safe and efficient recycling of solid waste resources.
基金supported by the National Basic Research Program(973)of China(No.2011CB201500)the National Natural Science Foundation of China(No.21277096)+1 种基金the Collaborative Innovation Center for Regional Environmental QualityShanghai Huanbao Waste Residue Treatment Co.Ltd
文摘Bottom ash is the major by-product of municipal solid waste incineration（MSWI）, and is often reused as an engineering material, such as road-base aggregate. However, some metals（especially aluminum） in bottom ash can react with water and generate gas that could cause expansion and failure of products containing the ash; these metals must be removed before the ash is utilized. The size distribution and the chemical speciation of metals in the bottom ash from two Chinese MSWI plants were examined in this study, and the recovery potential of metals from the ash was evaluated. The metal concentrations in these bottom ashes were lower than that generated in other developed countries. Specifically, the contents of Al,Fe, Cu and Zn were 18.9–29.2, 25.5–32.3, 0.7–1.0 and 1.6–2.5 g/kg, respectively. Moreover,44.9–57.0 wt.% of Al and 55.6–75.4 wt.% of Fe were distributed in bottom ash particles smaller than 5 mm. Similarly, 46.6–79.7 wt.% of Cu and 42.9–74.2 wt.% of Zn were concentrated in particles smaller than 3 mm. The Fe in the bottom ash mainly existed as hematite, and its chemical speciation was considered to limit the recovery efficiency of magnetic separation.
基金the National key R&D projects(Nos.2019YFC1907101,2019YFC1907103,2017YFB0702304)the Key R&D project in Ningxia Hui Autonomous Region(No.2020BCE01001)+5 种基金the National Natural Science Foundation of China(No.51672024)the Xijiang Innovation and Entrepreneurship Team(No.2017A0109004)the Program of China Scholarships Coun-cil(No.201806465040)the Fundamental Research Funds for the Central Universities(Nos.FRF-IC-19-007,FRF-IC-19-017Z,FRF-MP-19-002,FRF-TP-19-003B1,FRF-GF-19-032B,and 06500141)the State Key Laboratory for Ad-vanced Metals and Materials(No.2019Z-05)the Integ-ration of Green Key Process Systems MIIT.
文摘Municipal solid waste incineration products of bottom ash(BA),fly ash(FA),and pickling sludge(PS),causing severe environ-mental pollution,were transformed into glass ceramic foams with the aid of CaCO3 as a pore-foaming agent during sintering.The effect of the BA/FA mass ratio on the phase composition,pore morphology,pore size distribution,physical properties,and glass structure was investigated,with results showing that with the increase in the BA/FA ratio,the content of the glass phase,Si-O-Si,and Q3Si units decrease gradually.The glass transmission temperature of the mixture was also reduced.When combined,the glass viscosity decreases,causing bubble coalescence and uneven pore distribution.Glass ceramic foams with uniform spherical pores are fabricated.When the content of BA,FA,and PS are 35wt%,45wt%,and 20wt%,respectively,contributing to high performance glass ceramic foams with a bulk density of 1.76 g/cm3,porosity of 56.01%,and compressive strength exceeding 16.23 MPa.This versatile and low-cost approach provides new insight into synergistically recycling solid wastes.
基金Supported by the Science and Technology Commission of Shanghai Municipality (08 DZ 1202802,09 DZ 1204105,09 DZ2251700)the National Natural Science Foundation of China (51008322)
文摘This research evaluated the use of sewage sludge and refuse incineration bottom ash to replace calcium sulfoaluminate cement （CSA） in making controlled low-strength material （CLSM）. Various properties of CLSM mixtures were characterized in terms of unconfined compressive strength, microstructure and leachability. It was found that the strength of tested CLSM mixtures ranged from 3.6 to 9.0 MPa, over the upper excavatable limit of 2.1 MPa. The micro-structural analysis revealed that sewage sludge and bottom ash were crystallochemically in- corporated within CLSM system_s by forming the needle-like ettringite （C3A＇3CS＇_H32） with exiguous tu.bers via the typical Pozzolanic Reaction, leading to a dense and low-porosity microst;＇ucture. Furthermore,-the toxicity characteristic leaching procedure evidenced that the cumulative leachable metals in the leachate were much below the regulatory thresholds. The potential for us!ng sewage sludge and bottom ash!n CLSM makin.g was thus confirmed.
文摘The bottom ash and fly ash from the co-combustion of wood residues and peat at a bubbling fluidised bed boiler（296 MW） contained only quartz（SiO_2）, microcline（KAl Si_3O_8） and albite（NaAlSi_3O_8）. Thus, X-ray powder diffraction（XRD） was not useful for clarifying the difference in the release of associated heavy metals from ash matrices. In order to assess the release of heavy metals from ashes under changing environmental conditions, they were sequentially extracted and fractionated by the BCR-procedure into acid soluble/exchangeable（CH_3COOH）, reducible（NH_2OH-HCl） and oxidizable（H_2O_2/CH_3COONH_4） phases. The CH_3 COOH extractable fraction in conjunction with the total heavy metals concentrations were used to calculate the risk assessment code values for heavy metals leaching from the ash matrix. The leaching studies indicate that the heavy metals in the bottom ash and fly ash are bound to different fractions with different strengths. From the environmental and utilization perspectives, heavy metals in ashes posed different levels of environmental contamination risk. Only As in the bottom ash posed a very high risk. High risk metals were Cd in the bottom ash as well as As, Cd and Se in the fly ash.
基金support was obtained from Universitas Gadjah Mada with funding number:828/BPP/2018。
文摘Fly and bottom ash(FABA)produced primarily from coal combustion in a coal-fred power plant consists of fne particles of the organic and inorganic mixture and trace elements.Eight FABA samples from coal-fred power plants in Java,Indonesia,had been collected for composition and rare earth element and Yttrium(REY)mode of occurrence identifcation.The geochemical composition of both major and trace elements was determined by inductively coupled plasma-mass spectrometry/atomic emission spectrometry(ICP-MS/AES).Furthermore,the composition of FABA was identifed by petrography with refected light microscopy and X-ray difraction(XRD)analysis.Simultaneously,scanning electron microscope determines the mode of occurrence of REY with an energy-dispersive X-ray(SEM–EDX).The study fnds that the inorganic component of FABA consists of glass,Fe–Mg spinel,mullite,quartz,Fe-oxide mineral,and K-feldspar.In contrast,the organic component is dominated by unburned coal.Glass is the most abundant component with cenospheres as major and pleiospheres as minor constituents.Trace elements analysis indicates REY concentration with heavy REY(HREY)distribution pattern.Moreover,SEM–EDX analysis results show that Yttrium(Y)occurs in glass and has a low concentration in spinel.From the mode occurrence of REY,in particular Yttrium,it can be predicted that alkaline fusion followed by acid leaching will be the most appropriate extraction method to extract REY from Indonesian FABA.
基金supported by the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commissionsupported by the National Metal and Materials Technology Center, National Science and Technology Development Agency, Ministry of Science and Technology, Thailand
文摘The curing sensitivity of concrete with cement Types 1, 3, and 5 as well as multiple powders consisting of cement, fly ash, and limestone powder was studied. Bottom ash was also used in the study as an internal curing agent and a partial substi- tution of fine aggregate. The curing sensitivity index was calculated by considering the performances of compressive strength and carbonation depth. Specimens were subjected to two curing conditions： continuously water-cured and continuously air-cured. The results show that cement Type 3 has a lower curing sensitivity, while cement Type 5 increases the curing sensitivity. For the mixes without bottom ash, the use of fly ash increases the curing sensitivity, while limestone powder reduces the curing sen- sRivity of concrete. The use of bottom ash in concrete reduces the curing sensitivity, especially at a lower mass ratio of water to binder. Concrete with limestone powder, together with bottom ash, is least sensitive to curing. The curing sensitivity calculated from carbonation depth also has a similar tendency as that derived by considering compressive strength. From the test results of compressive strength and curing sensitivity, bottom ash has been proven to be an effective internal curing agent.
基金financial support from the Talent Support Fund of Tsinghua University (No. 413405001)
文摘The radioactivity of uranium in radioactive coal bottom ash（CBA） may be a potential danger to the ambient environment and human health. Concerning the limited research on the distribution and mode of occurrence of uranium in CBA, we herein report our investigations into this topic using a number of techniques including a five-step Tessier sequential extraction, hydrogen fluoride（HF） leaching, Siroquant（Rietveld） quantification, magnetic separation, and electron probe microanalysis（EPMA）. The Tessier sequential extraction showed that the uranium in the residual and Fe–Mn oxide fractions was dominant（59.1%and 34.9%, respectively）. The former was mainly incorporated into aluminosilicates,retained with glass and cristobalite, whereas the latter was especially enriched in the magnetic fraction, of which about 50% was present with magnetite（Fe_3O_4） and the rest in other iron oxides. In addition, the uranium in the magnetic fraction was 2.6 times that in the non-magnetic fraction. The experimental findings in this work may be important for establishing an effective strategy to reduce radioactivity from CBA for the protection of our local environment.
基金supported by the Talent Support Fund of Tsinghua University(No.413405001)
文摘Similar to chromium contamination, the environmental contamination caused by uranium in radioactive coal bottom ash（CBA） is primarily dependent on the chemical speciation of uranium. However, the relationship between uranium speciation and environmental contamination has not been adequately studied. To determine the relationship between uranium speciation and environmental contamination, X-ray absorption fine structure（XAFS） and X-ray photoelectron spectra（XPS） analyses were performed to determine the uranium speciation in CBA exposed to different chemical environments and simulated natural environments. The leachability of the different forms of uranium in the CBA was studied via a simulated acid rain leaching experiment, and the results showed that 57.0% of the total uranium was leached out as U（VI）. The results of a linear combination fit（LCF）of the X-ray absorption near edge structure（XANES） spectrum revealed that in the raw CBA, the uranium mainly occurred as U_3O_8（71.8%）. However, in the iron-rich particles, the uranium mainly occurred as UO_2（91.9%） after magnetic separation. Magnetite is a ubiquitous ferrousbearing oxide, and it was effective for the sorption of U（IV）. The result of FeSO_4 leaching experiment indicated that 96.57% of total uranium was reduced from U（VI） to U（IV） when infiltrated with the FeSO_4 solution for 6 months. This result clearly demonstrated the changes in chemical valence of uranium in the coal ash and provided a conceptual principle for preventing uranium migration from ash to the surrounding soil and plants.
文摘In tropical regions,heavy rainfall induces erosion and shallow landslides on road embankments.Cement-based stabilization methods,common in these regions,contribute to climate change due to their high carbon footprint.This study explored the potential application of coir fiber-reinforced laterite soil-bottom ash mixtures as embankment materials in the tropics.The objective is to enhance engineered embankment slopes'erosion resistance and stability while offering reuse options for industrial byproducts.This study examined various mix designs for unconfined compressive strength(UCS)and permeability,utilizing 30%bottom ash(BA)and 1%coir fiber(CF)with varying sizes ranging from 10 to 40 mm,6%lime,and laterite soil(LS),followed by microstructural analyses.The results demonstrate that the compressive strength increases as the CF length increases to 25 mm.In contrast,permeability increases continuously with increasing CF length.Lime-treated mixtures exhibit superior short-and long-term strength and reduce permeability owing to the formation of cementitious materials,as confirmed by microstructural analyses.A lab-scale slope box was constructed to evaluate the surface erosion of the stabilized laterite soil embankment.Based on the rainfall simulation results,the LS-BA-CF mixtures show better resistance to erosion and deformation compared to untreated LS,especially when lime is added to the top layer.This study provides insights into a sustainable and cost-effective approach for slope stabilization using BA and CF,offering a promising solution for tropical regions susceptible to surface erosion and landslides.
基金supported by the National Natural Science Foundation of China Project 51868058,52068058Inner Mongolia Natural Science Foundation 2018MS05011Inner Mongolia“Grassland Talent”CYYC5039.
文摘The destruction of concrete building materials in severely cold regions of the north is more severely affected by freeze-thaw cycles,and the relationship between the mechanical properties and pore structure of concrete with fine aggregate from municipal solid waste(MSW)incineration bottom ash after freeze-thaw cycles is analyzed under the degree of freeze-thaw hazard variation.In this paper,the gray correlation method is used to calculate the correlation between the relative dynamic elastic modulus,compressive strength,and microscopic porosity parameters to speculate on the most important factors affecting their changes.The GM(1,1)model was established based on the compressive strength of the waste incineration ash aggregate concrete,the relative error between the simulated and actual values in the model was less than 5%,and the accuracy of the model was level 1,indicating that the GM(1,1)model can well reflect the change in the compressive strength of the MSW incineration bottom ash aggregate concrete during freeze-thaw cycles.Using the gray correlation method,the correlation between the relative dynamic elastic modulus,compressive strength,air content,specific surface area,pore spacing coefficient,and pore average chord length was calculated,and the pore spacing coefficient and pore average chord length were determined to be highly correlated with each other.This determination can help analyze and infer the deterioration mechanism of concrete subject to freeze-thaw cycles.These results can provide a theoretical basis for guiding the engineering practice of concrete with fine aggregates of household bottom ash in the northern cold region.
文摘Three fresh China coals （lignitie, bituminite and anthracite） from different geological origin and the corresponding fly and bottom ashes were studied by room temperature（RT） Mossbauer spectroscopy（MS）. The iron-bearing minerals were characterized to be mainly pyrite in all coal samples by the hyperfine parameters.Suphate（FeSO4·nH2O） was found in bituminite and anthracite coal.The MSssbauer spectra of the fly and bottom ashes as a result of pulverised coal combustion（PCC） in Xiaolongtan,Shuicheng and Luohuang Power Plants are comprised of superimposed sextets and doulets of oxides includes maghemite（γ-Fe2O3）, magnitite（Fe3O4）, haematite（α-Fe2O3）, magnesioferite （MgFe2O4）, Fe^3＋/Fe^2＋ -mullite, Fe^3＋ -glass silicate and metallic iron. The studies also show that iron-bearing minerals in coals are largely dependant on geological regions and coal rank, the composition of the corresponding fly and bottom ashes will not only depend on the type and mineralogy of the feed coal but also on the local nature of combustion.
文摘Medical waste incinerators emit a wide range of pollutants like heavy metals, dioxins and furans. These include Pb （lead）, Hg （mercury）, Cd （cadmium）, fine dust particles and PICs （products of incomplete combustion）. The objective was to determine the elemental composition of medical waste residue after incineration in selected hospitals in Kiambu County, Kenya. Bottom/fly ash samples were collected from the burners/incinerators in the selected health care facilities visited. The concentrations of the metals in the fly ash and bottom ash were determined using an XRF （X-ray fluorescence） spectrometer after acid digestion. The concentrations of heavy metals in the fly and bottom ash were as follows： Ti （titanium） 62-839 mg·kg^-1 and a mean of 202 mg·kg^-1 and 344 mg·kg^-1 in fly ash and bottom ash, respectively. Ca （calcium） was 37,753-204,475 mg.kg1 with means of 27,132 mg.kg-1 in fly ash and 131,185 mgg·kg^-1 in bottom ash. Zn （zinc） was 297-6,605 mg·kg^-1 with means （2,307 mg·kg^-1 in fly ash, 4,359 mg·kg^-1 in bottom ash）, Pb （13-1,819 mg·kg^-1） had means of 280 mg·kg^-1 in fly ash and 291 mg-kg-1 in bottom ash. Cu （copper） （9.5-250 mg·kg^-1） had means of 83.47 mg·kg^-1 in fly ash and 98.8 mg·kg^-1 in bottom ash. The wide variations in results can be attributed to the different burners/incinerators used and different segregation methods of the medical waste. The results show that the reported levels of heavy metals could pose a health risk due to possible leaching after disposal.
基金Acknowledgements： The study was supported by the National Natural Science Foundation of China （No. 40501063）.
文摘Bottom ash. a power plant waste, was used to adsorb acid orange 7. The adsorption of acid orange 7 in aqueous solutions onto bottom ash was studied as functions of particle size. dosage, initial concentration and agitation time by batch experiments. Under conditions of bottom ash dosage of 1.5 g/50 ml and 5 g/50 ml for 〈0.074 mm and 0.074 mm-0.2 mm of bottom ash, respectively, it could achieve 99.1% and 87.6% dye removal efficiency. The adsorption isotherms for the bottom ash could be well described by both Freundlich and Langmuir isotherms. The calculated dye adsorption capacities of bottom ash for the particle size of 0.074 mm -0.2 mm and 〈0.074 mm were 2.78 mg/g and 10.21 mg/g, respectively. The results indicated that the dye uptake process fitted to the pseudo-first-order kinetic model better than the pseudo-second-order. The data were also fitted to intraparticle diffusion model by two adsorption stages, due to the difference in rate of mass transfer in the initial and final stages of adsorption. Significant variations were observed in the FTIR spectra and Stem photographs of bottom ash after adsorption. The column parameters were calculated by breakthrough curves at different flow rates and bed depths.
文摘In this study, SCM （supplementary cementitious materials）, such as nano silica, micro silica, fly ash and bottom ash, have been evaluated for optimal level of replacement as blending material in cement and concrete. The physical and chemical properties of the above materials were first analyzed. This study focused on compressive strength of concrete with different mixes at different ages. In many cases, products made with fly ash, micro silica, nano silica and bottom ash perform better than products made without them. Test results obtained in this study indicate that up to 5% nano silica, 10% micro silica, 20-30% fly ash and 10% bottom ash could be advantageously blended with cement without adversely affecting the strength. However, optimum levels of these materials are 1-3% nano silica, 3-8% micro silica, 10% fly ash and 5% of bottom ash when we consider the strength of concrete. All percentages are defined by weight unless otherwise mentioned.
文摘It is well known that the finer particle of cementing material has more pozzolanic reaction than the coarser. This paper investigates the shear properties of geocomposite soil with various particle sizes of bottom ash. The geocomposite soil （GCS） in this study consists of dredged soil, bottom ash and cement for recycling dredged soil and bottom ash. Three different particle sizes of bottom ash passing No. 4 sieve, No. 40 sieve, and No. 140 sieve were added into soil mixtures, namely as GCS 4, GCS 40, and GCS 140, respectively. These bottom ashes have the same chemical component except for different particle sizes. Several mixtures were prepared with various contents of bottom ash ranging from 0 to 100% at 50% intervals by the weight of dry dredged soil. In this study, several series of unconfined compression test were carried out on the mixtures with various curing times. It is found that the unconfined compressive strength is a function of curing time and bottom ash content. For the curing time less than 28 days, the GCS 4 has higher unconfined compressive strength than the GCS 40 and GCS 140 due to the interlocking effect and friction between the particles with angular shape of coarse bottom ash. For the curing time larger than 28 days, the GCS 140 has higher strength due to the pozzolanic reaction. However, the ratios of secant modulus to unconfined compressive strength of three mixtures are almost the same, and in range of （46-100）, regardless of mixing condition and curing time.
文摘In this paper, the mechanical and thermal properties of a sand-clay ceramic with additives coal bottom ash (CBA) waste from incinerator coal power plant are investigated to develop an alternative material for thermal energy storage (TES). Ceramic balls are developed at 1000°C and 1060°C using sintering or firing method. The obtained ceramics were compressed with a compression machine and thermally analyse using Decagon devise KD2 Pro thermal analyser. A muffle furnace was also used for thermal cycling at 610°C. It was found that the CBA increased the porosity, which resulted in the increase of the axial tensile strength reaching 3.5 MPa for sand-clay and ash ceramic. The ceramic balls with the required tensile strength for TES were selected. Their volumetric heat capacity, and thermal conductivity range respectively from 2.4075 MJ·m-3·°C-1 to 3.426 MJ·m-3·°C-1 and their thermal conductivity from 0.331 Wm-1·K-1, to 1.014 Wm-1·K-1 depending on sand origin, size and firing temperature. The selected formulas have good thermal stability because the most fragile specimens after 60 thermal cycles did not present any cracks. These properties allow envisioning the use of the ceramic balls developed as filler material for thermocline thermal energy storage (structured beds) in Concentrating Solar Power plants. And for other applications like solar cooker and solar dryer.
文摘Health-care waste contains potentially harmful microorganisms and compounds which can infect and affect hospital patients, healthcare workers, the general public and environment. Therefore, management of health care waste requires safe handling, treatment and disposal procedures. While incineration reduces the volume and quantity of waste for final disposal, it leads to the production of fly and bottom ashes laden with toxic incomplete combustion products such as Polycyclic Aromatic Hydrocarbons (PAHs), dioxins, furans and heavy metals. This exposes workers who handle and dispose the bottom ashes, hospital patients, the general public and environment. The goal of this study was to determine the total and individual levels of 16 most prevalent and toxic PAHs. Bottom ash samples were collected from incinerators in five county hospitals in Kenya, namely;Moi-Voi, Narok, Kitale, Makindu and Isiolo. Bottom ash samples were collected over a period of six months from the five hospitals. The samples were then sieved, homogenised and stored at 4°C in amber coloured glass containers. The PAHs were extracted using 30 ml of a hexane-acetone solvent (1:1) mixture by ultrasonication at room temperature (23°C) for 45 minutes. The PAHs were then analyzed with a GC-MS spectrophotometer model (Shimadzu GCMS-QP2010 SE) connected to a computer work station was used for the PAHs analysis. The GC-MS was equipped with an SGE BPX5 GC capillary column (30 m × 0.25 mm × 0.25 μm) for the separation of compounds. Helium was used as the carrier gas at a flow rate of 15.5 ml/minute and 14.5 psi. 1 μl of the sample was injected at 280°C, split mode (10:1). The oven programming was set for a total runtime of 40 minutes, which included: 100°C (2-minute hold);10°C /min rise to 200°C;7°C /min rise to 249°C;3°C /min rise to 300°C (2-minute hold). The interface temperature was set at 290°C. Analysis was done in Selected Ion Monitoring (SIM) mode and the peak areas of each of the PAHs were collected from the chromatograph and used for quantification of the 16 PAHs listed by the U.S. Environmental Protection Agency (EPA) which included, BaA (benz[a]anthracene: 4 rings), BaP (benzo[a]pyrene: 5 rings), BbF (benzo [b]fluoranthene: 5 rings), BkF (benzo[k]fluoranthene: 5 rings), Chr (chrysene: 4 rings), DbA (dibenz[a,h]anthracene: 5 rings), InP (indeno[1,2,3 - cd] pyrene: 6 rings) and Acp (acenaphthene: 3 rings), Acpy (acenaphthylene: 3 rings), Ant (anthracene: 3 rings), BghiP (benzo[g,h,i]perylene: 6 rings), Flu (fluorene: 3 rings), FluA (fluoranthene: 4 rings), Nap (naphthalene: 2 rings), PhA (phenanthrene: 3 rings) and Pyr (pyrene: 4 rings). Ion source-interface temperature was set at 200°C - 250°C. Internal standards from Sigma Aldrich were used in the analysis and the acquired mass spectra data were then matched against the NIST 2014 library [1] [2]. The mean PAHs concentration in the bottom ashes of each hospital varied broadly from 0.001 mg/kg to 0.4845 mg/kg, and the mean total concentration levels of individual PAHs ranged from 0.0072 mg/kg to 1.171 mg/kg. Low molecular weight PAHs (Phenanthrene, Naphthalene and Fluorene) were predominant in all the hospital wastes whereas Kitale and Narok presented the lowest PAHs concentrations and the lowest number of individual PAHs. Moi/Voi recorded the highest total PAHs concentration at 1.3129 ± 0.0023 mg/kg from a total of 11 PAHs being detected from the bottom ash samples. Narok had only three PAHs being detected at very low concentrations of 0.0041 ± 0.00 mg/kg, 0.0076 ± 0.00 mg/kg and 0.012 ± 0.00 mg/kg for phenanthrene, anthracene and chrysene respectively. This study presents hospital incinerator bottom ash as containing detectable levels of both carcinogenic and non-carcinogenic PAHs. Continued unprotected exposure of hospital workers (waste handlers) to the bottom ash PAHs could be hazardous to their health because of their cumulative effect. Preventive measures e.g. the use of Personal protective equipment (PPE) should be prioritised to minimise direct contact with the bottom ash. The study recommends an upgrade on incinerator technology for efficient combustion processes thus for better pollution control.
文摘Healthcare wastes contain potentially harmful microorganisms, inorganic and organic compounds that pose a risk to human health and the environment. Incineration is a common method employed in healthcare waste management to reduce volume, quantity, toxicity as well as elimination of microorganisms. However, some of the substances remain unchanged during incineration and become part of bottom ash, such as heavy metals and persistent organic pollutants. Monitoring of pollution by heavy metals is important since their concentrations in the environment affect public health. The goal of this study was to determine the levels of Copper (Cu), Zinc (Zn) Lead (Pb), Cadmium (Cd) and Nickel (Ni) in the incinerator bottom ash in five selected County hospitals in Kenya. Bottom ash samples were collected over a period of six months. Sample preparation and treatment were done using standard methods. Analysis of the heavy metals were done using atomic absorption spectrophotometer, model AA-6200. One-Way Analysis of Variance (ANOVA) was performed to determine whether there were significant differences on the mean levels of Cu, Zn, Pd, Cd and Ni in incinerator bottom ash from the five sampling locations. A post-hoc Tukey’s Test (HSD) was used to determine if there were significant differences between and within samples. The significant differences were accepted at p ≤ 0.05. To standardize the results, overall mean of each metal from each site was calculated. The metal mean concentration values were compared with existing permissible levels set by the WHO. The concentrations (mg/kg) were in the range of 102.27 - 192.53 for Cu, Zn (131.68 - 2840.85), Pb (41.06 - 303.96), Cd (1.92 - 20.49) whereas Ni was (13.83 - 38.27) with a mean of 150.76 ± 77.88 for Copper, 131.66 ± 1598.95 for Zinc, 234.60 ± 262.76 for Lead, 12.256 ± 10.86 for Cadmium and 29.45 ± 18.24 for Nickel across the five sampling locations. There were significant differences between levels determined by one-way ANOVA of Zn (F (4, 25) = 6.893, p = 0.001, p ≤ 0.05) and Cd (F (4, 25) = 5.641, p = 0.02) and none with Cu (F (4, 25) = 1.405, p = 0.261, p ≤ 0.05), Pb (F (4, 25) = 1.073, p = 0.391, p ≤ 0.05) and Ni (F (4, 25) = 2.492, p = 0.069). Results reveal that metal content in all samples exceed the WHO permissible levels for Cu (100 mg/kg), while those for Ni were below the WHO set standards of 50 mg/kg. Levels of Zn in three hospitals exceeded permissible level of 300 mg/kg while level of Pb exceeded WHO set standards of 100 mg/kg in two hospitals. Samples from four hospitals exceeded permissible level for Cd of 3 mg/kg. This study provides evidence that incinerator bottom ash is contaminated with toxic heavy metals to human health and the environment. This study recommends that hospitals should handle the bottom ash as hazardous wastes and there is need to train and provide appropriate personal protective equipment to healthcare workers, waste handlers, and incinerator operators and enforce compliance to existing regulation and guidelines on healthcare waste management to safeguard the environment and human health.
