Metals In Ash Research Articles

Co-gasification of municipal sewage sludge and cotton stalk enhanced by metal-enriched texture dyeing sludge additives for syngas production

In this study, co-gasification characteristics of municipal sewage sludge (MSS) and cotton stalk (CS) for syngas production enhanced by using metal-rich texture dyeing sludge (TDS) pyrolysis residues as additives wereinvestigated in a TGA and a fixed bed reactor. Kinetic analysis results showed that the addition of TDS residue prepared at 600 °C (TDS-600) resulted in the reduction of activation energy of MSS/CS co-pyrolysis to the maximum extent. The syngas yield greatly increased with the rising temperature and steam volume fraction (fH2O). However, the excessive steam at high temperature may lead to the decrease of syngas yield due to the gas expansion effect. The maximum syngas yield of 0.808 m3/kg could be obtained at an optimal gasification temperature of 850 °C and a fH2O of 20 %. In the co-gasification of MSS and CS, the syngas yield increased from 0.683 without TDS-600 to 0.903 kJ/mol with 20 % TDS-600 and the tar content decreased from 40.15 % to 26.45 %, suggesting the outstanding catalytic effect of TDS-600 on promoting syngas yield and tar decomposition. The possible ecological risk of heavy metals in ashes after co-gasification was evaluated by the potential ecological risk index (RI). The calculated RI values of all samples were <50, demonstrating the safe application of ashes in agriculture industry.

Migration characteristics and ecological risk assessment of heavy metals in ash from sewage sludge co-combustion in coal-fired power plants

Co-combustion in coal-fired power plants is one of the main methods to dispose of municipal sewage sludge (MSS). The high heavy metals content of MSS increases the ecological risk of ash from the coal and MSS co-combustion. In response to this problem, the three types of fly ash or bottom ash from MSS co-combustion in the three coal-fired power plants were sampled. The properties of fly ash and bottom ash were analyzed in terms of ash composition, particle size distribution, heavy metals content and leaching characteristics. The potential ecological risks were evaluated using the ecological risk index assessment method. The results showed that the co-combustion of MSS had no significant effect on the ash composition order and heavy metals content order. However, the total content of Cu, Mn, Pb and Zn, Hg in the co-combustion ash was higher than that in the coal-fired ash without sludge blending but did not exceed the risk screening value for soil heavy metal contamination of residential land. Heavy metals showed significant enrichment in fly ash and dilution in bottom ash. The leaching concentrations of Cr and Ni were several times the limit value. The potential ecological risk levels of fly ash and bottom ash were moderate risk and high risk respectively. Cr and Hg were the main contributors to potential ecological risks. The contents of Cr, Hg and Ni need to be paid attention to in the subsequent utilization of coal ash mixed with co-combustion of sewage sludge.

Wood Ash Additive for Performance Improvement of Gelatin-Based Slow-Release Urea Fertilizer

Urea is a crucial nutrient for plant growth, but because of its substantial losses due to nitrification, ammonification, and subsurface leaching, there is currently a push to reduce these losses. Urea is frequently uploaded and trapped in gelatin. In this research, the improvement of urea uploading and encapsulation efficiency is investigated using wood ash made from plant biomass (Pinus roxburghii). The 8 g w/v of gelatin was mixed with various concentrations of wood ash (from 4 to 16 g w/w), urea (from 4 to 24 g w/w), and glutaraldehyde (from 0.5 to 3 mL g−1) to prepare various formulations of slow-release fertilizer (SRF). According to this study, adding wood ash to gelatin increases its ability to upload and encapsulate urea. The urea on its surface and the metal in wood ash both considerably contribute to the compositional alterations in gelatin in SRFs, which were demonstrated by IR spectroscopy. Visualization from photographs revealed that the homogenous dispersion of wood ash improved structural compatibility. The water content of the SRF formulation showed that wood ash can reduce water absorption by changing how hydrophobic gelatin is. Wood ash improves the gelatin’s ability to reduce the rapid release of urea over time, according to testing of cumulative urea release from SRF. The optimal combinations for achieving the maximum 53.43% of urea uploading were 2.44 g of urea, 2.47 mL of glutaraldehyde, and 1.50 g of wood ash, according to the Box–Behnken model. The gelatin-based SRF that had been amended with wood ash was applied to the Mentha spicata plant, and the plant’s healthy development and higher chlorophyll content revealed its agronomic potential. This study has a significant contribution to the development of an affordable and more effective wood ash-modified gelatin-based SRF.

Biomass gasification ash reutilization: Recirculation reusability and mechanism analysis

A biomass gasification ash disposal method, recirculating it to gasification process, was proposed in this work. The recirculation reusability was analyzed via reusing corn straw (CS) gasification ash for six recirculation in a gasifier. Metals, especially K, got enriched in ash during ash recirculation. Under the 1st ash recirculation, CO content, H2 content and lower heating value of gas products increased from 16.02 to 19.97 vol%, from 11.30 to 15.72 vol%, from 5.38 to 6.47 MJ/Nm3, respectively. Moreover, it also exhibited an ability in tar decomposition, resulting in a tar reduction (4.63 g/Nm3 for raw CS gasification and 3.62 g/Nm3 for 1st ash recirculation). These positive effects gradually increased during the first four ash recirculation. The positive effects highly depended on the accumulation of metals (K, Na, Ca, Mg, and Fe) in ash. The positive effect did not increase as the fifth and sixth ash recirculation were conducted, resulting from the constant metals content in ash. Grey relational analysis showed that the total content of these metals was the most significant influencing parameter, followed by K content, water-soluble K content, Ca content, respectively. Moreover, pollutant SO2 could be captured by CaO during ash recirculation. This reaction competed with simultaneous CaO carbonation reaction, while it was inferior to the latter. Thus, only the first and second ash recirculation exhibited satisfactory ability in SO2 capture. In summary, ash recirculation in gasification process was feasible for upgrading gasification performance and its effect was persistent.

Distribution characteristics and ecological risks of heavy metals in bottom ash, fly ash, and particulate matter released from municipal solid waste incinerators in northern Vietnam.

Residue concentrations of heavy metals, including As, Cd, Cr, Cu, Ni, Pb, and Zn, were determined in bottom ash, fly ash, and particulate matter (PM10) samples collected from five municipal incinerators in northern Vietnam to assess their occurrence, distribution characteristics, and potential risks. Concentrations and profiles of heavy metals are presented, showing the dominance of Zn in all types of samples. Highly volatile elements (Cd, Pb, and Zn) were found at elevated proportions in PM10 but not fly ash. The large difference in the heavy metal profiles could be explained by the variation of input raw materials, the absence of an appropriate cycle for the material feeding process, and post-combustion technology applied. Mass balance of heavy metals in the bottom ash, fly ash, and PM10 varied significantly between the investigated incinerators, largely due to the difference in incineration technology and air pollution control system. Emission factors and annual emissions were also estimated, indicating the highest value and amount in bottom ash, followed by PM10 and fly ash. Our results are among the first studies reporting contents and emissions of toxic elements in incinerated solid wastes in Vietnam.

Investigating the Effect of Fly Ash Addition on the Metallurgical and Mechanical Behavior of Al-Si-Mg-Cu Alloy for Engine Cylinder Head Application.

The authors researched the physical, metallurgical, and mechanical characteristics of A354 alloy (Al-Si-Mg-Cu) reinforced with 5, 10, and 15 wt% of fly ash metal matrix composites. A baseline alloy and three composites were fabricated by a liquid metallurgy route and poured into a permanent mold to obtain cast rods of dimension Φ32 mm × 156 mm. The metallurgical characterization of the developed alloy and metal matrix composites was conducted using energy-dispersive spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), and X-ray diffraction. All the developed composites showed a pore-free nature, but only A354 alloy reinforced with 5 wt% of fly ash (AF5) possessed a homogeneous distribution and perfect bonding of the fly ash with the A354 matrix. Therefore, transmission electron microscopy (TEM) analysis was performed on the sample AF5. All developed alloys and metal matrix composites were subjected to hardness and mechanical property tests. It was observed that the AF5 sample had 170 ± 5.6 HV and tensile strength of 216 ± 2.3 MPa, 18.8% and 24.8% higher than the A354 matrix, but the ductility (6.5 ± 0.43%) was reduced by 23% from the baseline alloy. Finally, the fractography analysis was conducted on all the samples using FESEM to analyze the fracture mode. The fabricated 5 wt% fly ash-based metal matrix composite showed better mechanical performance than other samples. Hence, sample AF5 is suggested for manufacturing components in automotive and structural parts.

Heavy Metals in Honey Collected from Contaminated Locations: A Case of Lithuania

Honey, as a bioindicator, can be used to determine the level of pollution in the environment with selected pollutants, including heavy metals. Twelve locations were selected for experimental studies near the main sources of pollution: industrial sites, landfills, railways, and highways. The honey samples were burned to ash, and the heavy metals in ashes were determined using aqua regia digestion in the microwave digestion system. The concentration of heavy metals (Cd, Cr, Cu, Pb, and Ni) was determined using a Buck Scientific model 210 VGP atomic absorption spectrophotometer with a graphite furnace atomizer and an acetylene-air flame. These median amounts of heavy metals were found in the analyzed honey samples: 0.0030 mg/kg for Cd, 0.0179 mg/kg for Pb, 0.0317 mg/kg for Cr, 0.0999 mg/kg for Cu, and 0.0332 mg/kg for Ni. The obtained results were compared with honey samples research conducted in other countries. It is difficult to compare the level of heavy metal results found in honey from different countries, as the type of honey, soil composition, rainfall, air temperature, the plants from which it was harvested, its vegetation and flowering duration, and the degree of anthropogenic pollution in the area differ. The heavy metal content tested in honey was found to be low, except for the Pb content in one sample of honey, and did not pose a risk to human health. A statistical analysis including average, median, standard deviation, confidence intervals, and Spearman coefficients was performed for the evaluation of the relationships between the heavy metal quantities and the determination of the impact of pollution sources (transport and industry). The correlation analysis showed a strong negative correlation coefficient between heavy metals and distance (r = −0.593 to −0.204).

Investigation of Mechanical and Tribological Properties of LM6-Fly Ash Metal Matrix Composite

Composite materials assume a significant part in auto, aviation, marine, and defense applications due to its unique properties. Aluminum alloys have certain advantages over other alloys. In this paper, the composite material comprised of Aluminum Alloy LM6 and fly ash (150 – 175 μm) has been picked as lattice and supporting materials individually. Magnesium is added to lessen the surface pressure and evade the dismissal of the particles from the melts. Liquid state processing through stir casting procedure was adopted for fabrication of mmc into necessary shape and size according to the ASTM principles by energetically mixing at consistent speed and time. The fly ash with various syntheses (2%, 4%, 6%) were added with LM6 combination. XRD and EDAX were used to examine the structural analysis of MMC, and optical microscopy and SEM were used to investigate the microstructure on MMC. Wear test was also carried out on MMC to ascertain the wear rate and cof of different MMCs. There is substantial improvement of mechanical properties like tensile strength, micro hardness, and density of the composite.

Study on denitrifying biogrout to immobilize heavy metals in bottom ash in an anaerobic environment and its immobilization mechanism

Incineration bottom ash (IBA) is the residue of municipal solid waste (MSW) after incineration, which is often used for land backfilling (in the anaerobic environment). This study reports a method of anaerobic bacteria for IBA treatment, and the mechanism of heavy metals immobilization by anaerobic bacteria is discussed in depth. In this study, the IBA from three cities, namely Shenyang, Wuhan, and Guangzhou in China, were treated with anaerobic bacterial grouting, and the leaching concentrations of heavy metals were detected. Their IBA production ranks among the top ten cities in China. The results show that the anaerobic bacteria can reduce the leaching concentration of Zn, Cu, Cd, Cr, As, and Pb, and the immobilization ratios reach 50–90 %. Biotreatment improves the carbonate-bound form of the noted heavy metals, and the carbonate-bound form is positively correlated with bioprecipitation of calcium carbonate. It is observed by scanning electron microscope (SEM) and optical microscope that fragmentized calcium carbonate crystals are still generated when the upper surface of the sample exposes to air. The mechanism of immobilization during the biomineralization process is revealed by the fluorescence spectrum and chemical reaction. In an anaerobic environment, the anaerobic bacteria enrich calcium ions and carbonate ions to generate biogel, which can physically envelop heavy metals. The induction of anaerobic bacteria can stabilize heavy metals by changing chemical speciation. They all reach the strength limitation of land backfill. This study provides a new idea to reduce the environmental harm from the IBA and improves the sustainable utilization of IBA.

Progress in physicochemical properties of ash/slag from co-gasification of agroforestry waste biomass and coal

Co-gasification of agroforestry waste biomass and coal realizes energy-saving, low-carbon emission, clean and efficient raw material conversion by taking advantage of their similarities and complementarities. The physicochemical properties of ash slag for raw materials are one of the key factors affecting the stable operation of co-gasification. It is the focus of co-gasification research. This paper reviews the research status of physicochemical properties of ash slag from co-gasification of agroforestry waste biomass and coal. It mainly includes the similarity and difference between agroforestry waste biomass ash and coal ash, the fusion and viscosity-temperature characteristics of mixed ash, the effect of alkali/alkaline earth metals in mixed ash on co-gasification reactivity, and sintering behavior during the slagging process. The influence mechanism of adding agroforestry waste biomass on the melting flow and sintering behavior of mixed ash is discussed. The prediction models and methods of fusion characteristics, viscosity-temperature, and slagging characteristics of mixed ash are also summarized. Finally, the future research directions of ash slag from co-gasification of agroforestry waste biomass and coal are proposed.

Morphochemical investigation on the enrichment and transformation of hazardous elements in ash from waste incineration plants

The transformation of heavy metals in ash from waste incineration plants is significant for ash management. The migration behavior of trace elements in ash after combustion, semidry deacidification, fabric filtration, and chelating agent stabilization was investigated from one waste incineration plant. The hazardous elements Zn, Pb, and As were enriched in raw fly ash (ash produced at a combustion temperature of 850–1100 °C) due to their relatively high volatility. Mercury, Cd, and Pb were captured in fly ash2 and processed by activated carbon and fabric filters. The removal rate of As (71%) was the highest among all studied elements due to a large amount of quinquevalent As removed. However, the average removal rate of elements in fly ash was only 13%. In the finally obtained fly ash3 (after chelating agent stabilization), a larger particle size (~100 μm) was found than that of raw ash. Furthermore, fly ash3 contains HgSO4 and trivalent As, which are toxic and likely to be precipitated when the fly ash3 is next utilized or deposited in a landfill, causing environmental risks.

Study on sulfur migration and carbon consumption during regeneration of SO2-loaded activated carbon: Effect of alkali/alkaline earth metals

Activated carbon (AC) has emerged as a new technology with promising application prospects for environment friendly SO2 removal, and the thermal regeneration process of SO2-loaded AC is the key step to realize adsorbent circulation and sulfur recovery. Herein, the synergistic effects of alkali/alkaline earth metals in ash on sulfur migration and carbon consumption were studied based on fixed bed adsorption and thermal regeneration. The experimental results showed that the adsorption atmosphere has a significant effect on gas desorption. In the temperature range of 150–850 °C, SO2 was the cause of excessive CO2 release during regeneration compared with non-adsorbed AC. Among them, the carbon consumption caused by CO2 release in the relatively low temperature range (150–500 °C) was mainly due to the regeneration reaction of chemisorbed SO2. The carbon consumption in the relatively high temperature range (500–850 °C) was mainly related to the Ca-based sulfate formed in the adsorption process, which was reduced during heating to release CO2. This study elucidates the synergistic effect of ash on the sulfur migration and carbon consumption in the process of regeneration, which provides a deeper understanding of the AC flue gas desulfurization and regeneration process.

Migration characteristics of heavy metals during co-combustion of dehydrated sludge with straw

Sludge incineration technology has significant advantages such as capacity reduction and energy utilization, but it will cause heavy metal pollution. Therefore, the co-combustion of dewatered sludge with corn straw at 700–850 °C was studied in a laboratory scale internal circulating fluidized bed. The effects of different temperature, sludge mixing ratio and secondary air ratio on the NO emission and the migration of different heavy metals in bottom ash, fly ash and flue gas after co-combustion were examined. The results show that under the experimental conditions, with the increase in temperature, the NO emission concentration increases, and the concentrations of V, Cr, As, Sb and Hg first increase and then decrease in the bottom ash, while the concentrations of Zn, Cu, Se and Cd vary to the contrary. The turning point of most heavy metals concentration is at 800 °C. However, with the increase in the sludge mixing ratio, the NO emission concentration first decreases and then increases, and the Cu, Hg and Tl concentrations all increase first and then decrease in the bottom ash, while the Cr concentration change is the opposite, with turning points all at the sludge mixing ratio of 10%. Also, with the increase in the secondary air ratio, the NO emission concentration decreases, and the Zn, Cu, Se and Hg concentrations in bottom ash decrease, on the contrary, the As and Cd concentrations increase.

Investigation of Pressed Solid Biofuel Produced from Multi-Crop Biomass

The paper presents the preparation and use of pressed solid biofuel of multi-crop plants (fibrous hemp (Cannabis sativa L.), maize (Zea mays L.) and faba bean (Vicia faba L.)) as mono, binary and trinomial crops. The results of the investigation show that three main chemical elements (carbon, oxygen and hydrogen) accounted for 93.1 to 94.9% of the biomass pellet content. The moisture content varied from 3.9 to 8.8%, ash content from 4.5 to 6.8% and calorific value from 16.8 to 17.1 MJ·kg−1. It was found that the density (DM) of all variants of pellets was very similar; the faba bean biomass pellets had the highest density of 1195.8 kg·m−3 DM. The initial ash deformation temperature (DT) of burning biomass pellets was detected, which varied from 976 to 1322 °C. High potassium (K), calcium (Ca) and phosphorus (P) concentrations were found in all types of biomass ash. The quantities of heavy metals in pellet ash were not large and did not exceed the permissible values according to Lithuanian legislation. These chemical properties of multi-crop biomass ash allow them to be used in agriculture for plant fertilization.

Technogenic Influence of the Composition of Ash Waste of the Zmiiv Power Plant on the Pedosphere

Purpose. The aim of the study is to analyze the geochemical composition of ash and slag waste at the Zmiiv Thermal Power Plant (TPP) and to identify the features of migration of heavy metals (HM) from the place of storage of ash and slag waste into the ecosystem. To achieve this goal, the following tasks were solved: geochemical analysis of ash and slag waste at Zmiiv TPP; study of the reliability of HM migration into the soil in the places of ash and slag waste storage. Methods. The content of heavy metals in ash, slag and soil were investigated using atomic absorption analysis (AAA) on a spectrophotometer S-115. X-ray diffraction analysis was used to determine the solid inorganic part of ash and slag. Results. Ash and slag of Zmiiv TPP contain Cu, Cr, As, Cd, Ni, Pb in quantities that are several times higher than the maximum permissible concentration (MPC). For ash and slag waste, the total pollution index is Zc = 43, which corresponds to a high level. That is, this artificially created horizon is dangerous. HM migrate into groundwater and into the soil near the ash dump due to the infiltration of atmospheric precipitation, emissions from water pipelines, filtration of water through the base of the ash dump of the Zmiiv TPP. To determine soil contamination near the ash dump, soil analyzes were performed at a distance of 0 ... 100 meters. At a distance of up to 100 meters from the dump, there is an excess of MPC in the soil for the content of Ni, Cu, As, Cr. At a distance of up to 100 meters from the dump, an excess of the MPC in the content of Ni, Cu, As, Cr is observed. Concentration factor exceeds unity for Cr, As, Cu, Cd, Ni. The content of Pb and Zn reaches background values only at a distance of more than 100 meters. The calculation of the total soil pollution indicator allows us to classify these soils as moderately hazardous and permissible. However, there are several significant disadvantages of the Zc indicator. First of all, it does not take into account the differences in the potential hazard of chemical elements, and, most importantly, the synergistic effects of polymetallic pollution. The coefficient of the synergistic effect of heavy metals is 26.64 (in the soil of the ash dump), then it decreases, but even at a distance of 100 meters it is 11.23, that is, at a distance of 0 ... 100 m from the ash dumps, the condition of the coefficient of synergistic effect is less than one. It has been established that Cu, Ni, Zn and Cr are characterized by low mobility in the soil near the ash dump, therefore they accumulate in the ecosystem near the ash dump, which is explained by the neutral and slightly alkaline soil pH values (pH = 8.0 ... 8.5). The ratio of mineral phases to glass is unstable; however, it should be noted that aluminosilicates, calcium silicates and glass predominate in ash and slag. Сompounds with HM are confined mainly to amorphous clay aggregates and sooty-carbon formations of ash, to a lesser extent to slag glass and even less to grains of quartz sand. Conclusions. Since the ash contains such fractions that can be easily carried by wind, it should be assumed that the HM entry into the ecosystem is also by air, which also contributes to air pollution. The solution to the problem of ash and slag waste disposal should be found in the production of building materials, in road construction, but it is necessary to study the composition of ash and slag and the probability of HM migration depending on the conditions of use.

Abundance and fractional solubility of phosphorus and trace metals in combustion ash and desert dust: Implications for bioavailability and reactivity

Aerosol phosphorus (P) and trace metals derived from natural processes and anthropogenic emissions have considerable impacts on ocean ecosystems, human health, and atmospheric processes. However, the abundance and fractional solubility of P and trace metals in combustion ash and desert dust, which are two of the largest emission sources of aerosols, are still not well understood. In this study, the abundance and fractional solubility of P and trace metals in seven coal fly ash samples, two municipal waste fly ash samples, and three desert dust samples were experimentally examined. It was found that the abundance of aluminum (Al) in combustion ash was comparable or even higher than that in desert dust, and, therefore, care should be taken when using Al as a tracer of desert dust. The abundance and fractional solubility of P were higher in combustion ash, with a soluble P content ~4–6 times higher than that of the desert dust, indicating that combustion ash could be an important source of bioavailable P in the atmosphere. Except for Mn, the abundance and fractional solubility of other heavy metals were higher in the combustion ash compared to the desert dust, indicating the potential importance of combustion ash in ocean ecosystems, human health, and atmospheric processes. In contrast, both the abundance and solubility of Mn were highest in the desert dust, indicating a potentially important source of soluble Mn in the atmosphere. The fractional solubilities of P and trace metals are significantly affected by acidity and ions in the extraction solutions, and it is suggested that a buffer solution can better represent the acidity of the aqueous system in the true atmospheric environment. The results of this study improve our understanding of the sources of bioavailable and reactive P and trace metals in ambient aerosols.

Phosphorus Recovery from Sewage Sludge Ash Based on Cradle-to-Cradle Approach—Mini-Review

The wastewater treatment process generates large amounts of P-rich organic waste (sewage sludge (SS)). The direct application of SS in agriculture, being controversial, is gradually being replaced by incineration, leading to the concentration of both P and heavy metals in the solid residual-sewage sludge ash (SSA). The novel closed-loop, cradle-to-cradle (C2C) approach leads to maintaining P production at current levels and counteracts its depletion in the future. The aim of this review is the presentation of the implementation of the C2C approach for P recovery. The paper focuses on steps that comprise P C2C, starting from the SS properties, being a derivative of wastewater type and treatment processes, to SS pre-treatment and finally leading to certified P-fertilizers production from SSA by application thermochemical or wet chemical extraction technologies. Examples of SSA treatment technologies and the final products are provided. It has been summarized that future research should focus on the production of SSA-based fertilizers aligning with the C2C concept and determining its effect on the various agriculture and horticulture crops.

Ilmenite as alternative bed material for the combustion of coal and biomass blends in a fluidised bed combustor to improve combustion performance and reduce agglomeration tendency

Co-firing coal and biomass has the potential to reduce GHG emissions. However, high levels of alkali and alkaline metals in biomass ash can bring additional issues to the operation of coal-fired boilers. This study investigates the effects of ilmenite as the bed material on CO and NOx emissions and combustion efficiency of a coal and biomass blend, and the agglomeration tendency of the bed material with a pilot-scale (30 kWth) bubbling fluidised bed combustor. The experiments were carried out at 900 °C using a bituminous coal blended with wheat straw pellets at 40 wt% as the fuel and silica sand as the baseline bed material. Samples of agglomerates collected from the combustor and cyclone ash were characterised by SEM-EDS, XRD, and XRF. The results revealed that ilmenite could reduce the level of excess air required to achieve complete combustion due to lower CO emissions and less efficiency loss compared to silica sand. However, ilmenite increased NOx emissions. Furthermore, the characterisation of the obtained agglomerates and cyclone ash showed that ilmenite could hinder the K-rich molten substance attachment to the bed material, leading to significantly smaller agglomerates and hence less tendency towards defluidisation in comparison to silica sand.

Implementation effect of municipal solid waste mandatory sorting policy in Shanghai

In Shanghai, the biggest metropolis in China, the source classification of domestic waste began in the 1990s but achieved little success over the past thirty years. Surprisingly, the compulsory classification provision of Shanghai residents' domestic waste since 2019 has been successful. In this work, the overall status, and challenges of municipal solid waste (MSW) management in Shanghai under compulsory waste sorting rules are investigated. We tracked the classification efficiency of municipal solid waste, physicochemical characteristics of separated waste, and the carbon emissions arising from waste disposal system. It was found that almost 83.62 % of household food waste has been effectively separated with high purity of 99.50 %, while the lower heating value (LHV) of residual waste was increased by 96.4 % compared to previous years. With effective waste classification, the net carbon emission of separated processing was reduced to 0.11 ton CE/ton waste. However, this system generated some negative outcomes as well such as the lower recovery value of metal in bottom ash and the higher chloride content in fly ash. Moreover, we have documented and discussed several challenges of sustainable waste management system in Shanghai in the text. In order to overcome those challenges, we recommend to: (i) establish a finer source separation and recycling system; (ii) develop highly-efficient resource recovery technologies of byproducts from waste disposal system; and (iii) propose optimization adjustment strategy for overcapacity in incineration facilities.

Evaluation of particle size distribution, mechanical properties, microstructure and electrochemical studies of AA1050/fly ash metal matrix composite

ABSTRACT The mechanical properties and corrosion studies of AA 1050 metal matrix composite reinforced with varying weight fractions of fly ash were investigated. The fly ash weight fractions selected for this study were 2.5 wt%, 5 wt%, 7.5 wt%, and 10 wt%. This research was undertaken to investigate the effect of fly ash particulates on cast AA 1050 matrix composite. The cast samples’ microstructural analysis showed uniform dispersion of the fly ash particles in the 7.5 wt% samples and fairly uniform distribution of the fly ash particles in both the 2.5 wt% and 5 wt% samples. The investigation into the mechanical properties of the samples showed that the ultimate tensile strengths were 75.94 Mpa, 86.35 Mpa, 89.75 Mpa, 92.5 Mpa, and 86.14 Mpa for the base metal, 2.5 wt%, 5 wt%, 7.5 wt%, and 10 wt% composites, respectively. The microhardness analysis revealed an increase in the microhardness values, which was highest for the 7.5 wt% sample. The corrosion studies showed that the corrosion rate was 0.039 mm/yr, 0.013 mm/yr, 0.071 mm/yr, 0.021 mm/yr, 0.051 mm/yr for the base metal, 2.5 wt%, 5 wt%, 7.5 wt%, and 10 wt% composites, respectively. The SEM micrographs revealed pitting as the predominant corrosion mechanism.