The integrated study of the effects of infographic design on waste separation behavior and the behavioral outcome implementation on waste composting.

This study revealed the effects of designed infographics for waste separation and the implementation of behavioral outcomes using surveys and lab-scale experiments. The designed infographics improved the waste separation behaviors of the respondents in term of subject norm, perceived behavioral control, and intention. These influential factors were increased by 5.84 to 20.5%. The effects of design elements including waste separation mascots, the knowledge of waste separation, and the knowledge of waste management were dependent on the ratio of graphics and messages. Therefore, the careful attention on design elements of the infographic had to be noted. According to survey results, animal bone and shell wastes were the highest miss-sorting waste for the compostable waste bin. Although the contamination rate of these wastes did not significantly affect the decomposition of organic waste in the composting process, the quality of the product was degraded in term of toxicity. The germination index was decreased by 66.0% under a 10% contaminated condition. In contrast, the increased the total Ca of compost was increased. Furthermore, the other chemical components of final composts were similar under various conditions. It could be concluded that the mixture of animal bone and shell in compostable waste is acceptable for the purpose of waste reduction. However, the contamination rate of inappropriate wastes in the compostable waste bin should be minimized to enable effective waste composting. The significant findings of this study will be able to apply to the design of waste separation at the source and the plan of waste management.

Insight into the role of SO2 on selenium conversion during adsorption by CaO: Theoretical calculation and experimental study.

SO2 can noticeably impact the control of high toxic selenium emissions from flue gas by CaO. Surprisingly, our experiments showed that under certain conditions, SO2 can promote selenium capture by CaO, rather than hinder it. To elucidate the underlying mechanism, a combination of theoretical calculations and experiments was conducted. Thermodynamic equilibrium analysis revealed that gaseous SO2 and solid Ca-S reaction products can promote SeO2 converting to SeO/Se0. The Ca-S products facilitated greater SeO2 conversion compared to SO2. Experimental results demonstrated that selenium adsorption capacity of incompletely sulfurized CaO (CaO with pre-adsorbed SO2) was higher than that of completely sulfurized CaO (Ca-S products), highlighting the importance of adsorption sites of CaO. Density functional theory calculations showed that the pre-adsorbed SO2 hardly affected selenium adsorption energy on the SO2/CaO surface, while completely sulfurized CaO had low selenium adsorption energy, explaining the experimental phenomenon and proving necessary of CaO. Additionally, SeO/Se0 had higher adsorption energy on CaO than SeO2. Overall, the promotion of SO2 on selenium adsorption was primarily affected by two factors: 1) sulfur facilitating SeO2 conversion to SeO/Se0 which can be adsorbed more easily by CaO; 2) sufficient adsorption sites on CaO surface existing for SeO/Se0 adsorption, despite co-adsorption with sulfur.

Motivation to Decrease Discharge Cost Results in Improper Discharge of Regulated Medical Wastes from Small Clinics: Inspectional and Statistical Evidence in the Tokyo Metropolitan Area.

Introduction: Regulated medical waste (RMW) management, particularly, improper discharges of RMW from small-scale medical institutions (less than 20 sickbeds), has drawn attentions. This study investigated improper discharges of RMW containers from small clinics to analyze improper discharge mechanisms. Methods: Inspectional survey categorized improper discharges into improper sealing, container deformation, overweight, container contamination, container damaging, etc. The inspection surveys were performed from April 2018 to March 2019. In total, 2364 containers were inspected, which was equivalent to 64317 Litters in container volume and around 13.19 Mg in weight. Results: About 38% of RMW containers were categorized to improper discharges. They consist mainly of improper sealing (67.0%), container deformation (24.6%), and overweight (6.31%). It was hypothesized that frequent RMW discharges allow short interval of container discharge, which prevents clinic staff from human errors due to forgetting and might reduce improper discharges. However, the inspection results rejected this hypothesis. The survey proposes that improper discharges were likely not sporadic events, which possibly occurred in any clinics, but repeated events in certain clinics. It was also hypothesized that saving discharge cost likely induced overpacking of RMW to containers, particularly larger volume containers, and caused improper sealing, container deformation, and eventually overweight. The inspection results and statistical analyses validated this hypothesis. This study also validated one more hypothesis that large compressive force required for complete sealing might cause improper sealing. The measurement results rejected it. However, they also suggest that gender and age of clinic staff might be partially associated with improper sealing. Conclusions: Improper discharges of RMW containers seem to be non-random events. Specific clinics likely repeat improper discharges using larger volume containers. It is proposed that decreasing discharge cost induces overpacking of RMW to containers, and causes subsequent problems like container deformation.

The effects of compost bin design on design preference, waste collection performance, and waste segregation behaviors for public participation.

Municipal solid waste (MSW) composting is one of the most effective strategies for MSW management but detrimental litter such as plastic and glass debris must be discarded elsewhere. Well-segregated wastes are necessary in this context. A compost bin is a waste collection tool for source separation. To date, the deployment of compost bins for source separation has received scant investigation. This study investigated the effects of compost bin design in terms of user design preferences, waste collection and sorting execution, and segregation behavior. The study comprised a survey and an on-site experiment. Design preferences of nine designed compost bins were evaluated by surveying 400 respondents using the pairwise comparison method. It was revealed that design preference was determined by bin shape and slot position. On-site experiments were conducted to establish collection rate, contamination rate, capture rate, and effective capture rate under different conditions. Under the experimental conditions, better segregation rates were observed in comparison with the control condition. The contamination rate was reduced by 55.9%. The capture rate and the effective capture rate were increased by 8.90%, and 53.4%, respectively. The significant effects of design preferences, physical designs, visual prompts, and past behavior were identified via statistical methods. Source-separated waste collection can be improved through preferred compost bin adoption, enhanced design, appropriate visual prompts, and experience in waste segregation. Therefore, the findings of this study will help to generate effective source-separated collection and allow compost bins to be placed in public areas for integrated and sustainable waste management.

Co-combustion of Oil Sludge Char with Raw/Hydrothermally Treated Biomass: Interactions, Kinetics, and Mechanism Analysis.

Comprehensive thermochemical treatment (pyrolysis and combustion) is considered to be an efficient method for treatment of oil sludge (OS) or utilization as a heat source. However, combustion of oil sludge char (OSC), the byproduct from OS pyrolysis, is difficult and energy-consuming due to the high ash content and low heating value. In this study, co-combustion of OSC with biomass is proposed, aiming at the efficient thermal treatment with heat recovery. The thermal characteristics, kinetics, and interactive mechanisms of co-combustion of OSC with raw wood (RW) or hydrothermally treated wood (HW) employing thermogravimetric analysis were investigated. The obtained results indicated that RW blending with OSC resulted in negative interactions with decreasing the apparent activation energies (E) of RW, attributed to the inhibited diffusion of volatiles. The developed porous structure in HW effectively promoted volatile matter diffusion. Coupled with the catalytic support by metal oxides in OSC, HW blending yielded positive interactions during co-combustion despite the increased E. The results showed that diffusion models were the most efficient mechanism for OSC/RW combustion. However, chemical reactions were found to be the rate-determining steps for OSC/HW combustion. The catalytic effect of inorganic elements and their physical influence on heat and mass transfer can control the co-combustion performance of OSC and biomass. The findings could offer reference information for understanding OSC co-combustion and provide a basis for implementing and optimizing the co-combustion between biomass and ash-rich waste.

Adsorptive reduction of water hardness by a highly porous and regenerative geopolymer fabricated from coal fly ash waste with low-temperature calcination.

In this research paper, potassium-activated geopolymer cubes (GeoC) fabricated from waste coal fly ash with low-temperature calcination were investigated as a water softening agent. The GeoC reduced water hardness contents by adsorbing calcium (Ca2+) and magnesium (Mg2+) ions from aqueous solutions. Batch experiments were conducted to investigate the adsorption performance for Ca2+ and Mg2+, including contact time, initial concentration of cations, and interference with competitive cations. The best performance for water hardness adsorption was found on GeoC-35, fabricated with the highest silicate ratio to hydroxide. The adsorption process reached equilibrium after a contact time of 6 h for Ca2+ and 24 h for Mg2+. The maximum adsorption capacity for Ca2+ and Mg2+ was 52.0 and 17.3 mg/g, respectively. Langmuir and pseudo-second-order models fitted the experimental data well, indicating that chemical reactions occurred on a homogeneous surface. The GeoC can also be reused for removing hardness. Furthermore, the increase in potassium and silicon concentration in solution varied directly with removal efficiency, suggesting that the aluminosilicate framework played a role in reducing water hardness via cationic exchange. The presence of competitive cations decreased adsorption ability, albeit it still exhibited an appreciable removal performance.

Perceptive preference toward recycling bin designs: Influential design item depending on waste type, the impact of past perception experiences on design preference, and the effect of color design on waste separation.

Efficient waste separation using recycling bins designed appropriately is promising for waste recycles. This study investigated recycling bin designs, in particular color and insert slot, and quantified perceptive preferences toward designs. This study hypothesized that design preference toward recycling bins is affected by past perceptions of recycling bin designs. Design categorization survey for 240 recycling bins used in public spaces shows that popular colors depend on design items and waste types. This study found that highly preferred colors were consistent with frequently used colors in certain design items, which was slot frame color for combustible and incombustible waste bins, and body color for PET bottle bins. Color preferences had statistically significant correlations with color usage rates (p = 0.009 for combustible waste bin, p = 0.032 for incombustible waste bin, and p = 0.012 for PET bottle bin, respectively). Although insert slot shape had moderate but significant correlations between slot shape preference and usage rate of slot shape (p = 0.002 or less for all recycling bins), the preference was mainly affected by slot largeness for combustible and incombustible waste bins. According to these results, this study concludes that the hypothesis was supported in particular for color preference. On the other hand, on-site experiments showed that the effect of only "impressive" color was too weak to improve waste separation. To encourage waste sorting using well-designed recycling bins, combination of preferred design items is necessary. Intensive usage of well-designed recycling bins for frequent perception opportunities is recommended as an environmental feedback to support sufficient design preference.

Inhalation bioaccessibility and health risk assessment of flame retardants in indoor dust from Vietnamese e-waste-dismantling workshops.

Although bioaccessibility testing is applied worldwide for appropriate chemical risk assessment, few studies have focused on the bioaccessibility of flame retardants (FRs), especially inhalation exposure. This study assessed inhalation exposure to FRs in indoor dust by workers at e-waste-dismantling workshops in northern Vietnam, by using modified simulated epithelial lung fluid (SELF) and artificial lysosomal fluid (ALF). The average mass concentrations of FRs were 130,000 ng/g for workplace dust (n = 3), 140,000 ng/g for floor dust (n = 3), and 74,000 ng/g for settled dust (n = 2), whereas the average bioaccessible concentrations of FRs were 1900, 1400, and 270 ng/g in the SELF condition and 2600, 770, and 490 ng/g in the ALF condition, respectively. Results clearly indicate that the bioaccessible concentrations of FRs are markedly lower than their mass concentrations. Tris(2-chloroethyl) phosphate (TCEP, ~19%), tris(2-chloroisopropyl) phosphate (TCIPP, ~35%), and tris(1,3-dichloroisopropyl) phosphate (TDCIPP, ~22%) showed comparably high bioaccessibility in both SELF and ALF conditions. In contrast, the bioaccessibility of tetrabromobisphenol A (TBBPA, ~20%) was high in the SELF condition, but not in the ALF condition. With regard to the test compounds' physicochemical properties, the inhalation bioaccessibility of FRs in both conditions increased as molecular weight or octanol-water partition coefficient decreased, and it decreased as water solubility decreased. Health risk assessment clearly indicated that the hazard quotient of FRs via inhalation exposure for workers in the e-waste-dismantling workshops was less than 1, suggesting that the inhalation exposure to FRs during indoor dismantling of e-waste at this site was negligible based on the current methodology of non-cancer health risk assessment used in this study.

The effects of color preference and noticeability of trash bins on waste collection performance and waste-sorting behaviors.

The improvement of waste separation is of great interest in mitigating problems related to municipal solid waste (MSW) management. Trash bins are commonly used for waste separation at source. Thus, appropriate trash bin designs are promising to improve waste collection and separation performance. This study investigated the effect of trash bin design on waste collection and waste-sorting behaviors in Thailand, focusing on color preference, setting location, and perceived ease in finding a trash bin (noticeability). Trash bins to separately collect compostable waste, recyclable waste, and PET bottles were tested. Perceived preferences for colors and noticeability were evaluated using pairwise comparison by survey questionnaires with a sample size of 889 respondents. Waste collection experiments were conducted to reveal waste collection, capture, contamination, and effective capture rates in three locations for 15 weeks. The results were analyzed via statistical methods. They suggested that trash bins with the least preferred colors had the highest waste separation efficiencies. On the other hand, color preference towards trash bins had no significant impact on waste collection. In addition, lower color preference contributed to lower noticeability of trash bins. The effective capture rate had a significantly negative correlation with noticeability. Highlighting the location of less noticeable trash bins might have helped participants practice correct waste disposal. In conclusion, location, unit color, and noticeability of trash bins can affect waste collection and separation performance. Increasing human awareness through appropriate design and setting of trash bins might enable more efficient collection of segregated wastes.

Bioaccessibility and exposure assessment of flame retardants via dust ingestion for workers in e-waste processing workshops in northern Vietnam.

Flame retardants (FRs) from electronic waste (e-waste) are a widespread environmental concern. In our study, in vitro physiologically based extraction tests (PBETs) for FRs were conducted in three different areas where dust remained after processing of e-waste to identify the bioaccessible FRs and quantify their bioaccessibilities of gastrointestinal tract for human as well as to assess the exposure via ingestion of workers in e-waste processing workshops. All 36 FRs were measured and detected in indoor dusts. Among the FRs, the mean concentrations of polybrominated diphenyl ethers (PBDEs) in the floor dust and settled dust were highest, 65,000 ng/g, and 31,000 ng/g, respectively. In contrast, phosphorus-containing flame retardants (PFRs) presented the highest mean concentration in the workplace dust samples, 64,000 ng/g. However, the highest bioaccessible concentrations in workplace dust, floor dust, and settled dust were observed for PFRs: 5900, 1600, and 680 ng/g, respectively. This study revealed that the higher bioaccessibility of PFRs versus other compounds was related to the negative correlation between FR concentrations and log KOW (hydrophobicity) values. The fact that hazard indices calculated using measured bioaccessibilities were less than 1 suggested that the non-cancer risk to human health by the FRs exposure via dust ingestion might be low.

Stochastic economic analysis of coal-alternative fuel production from municipal solid wastes employing hydrothermal carbonization in Zimbabwe.

Hydrothermal carbonization (HTC) is a promising technology for converting high moisture municipal solid waste (MSW) to a safe low-chlorine hydrochar. The key objective is to assess the economic viability of an HTC based MSW management system in Zimbabwe. Previous studies have only used deterministic estimates of hydrochar production costs disregarding uncertainties in their model parameters. Herein, a probabilistic economic analysis is introduced to quantify the uncertainty concerning costs. The goal is to determine factors that will consolidate the venture to achieve a certain level of return. The effectiveness of different investment strategies, namely, a government or private sector-run operation will be tested using Monte Carlo simulations. Results indicate a 55% and 18% probability for a positive Net Present Value (NPV) for a state-run and private operation respectively. A specific investment cost of US$54 - 67 per Mg of MSW treated, a return on investment (ROI) of 5.4-29.0% and internal rate of return (IRR) of 5.2-22.9% can be expected if the project is undertaken by government. The private sector can expect an ROI of -0.8-18.2% at a 90% confidence level and a lower IRR of -2.1-16.2% from US$57 - 71 per Mg of MSW invested. Contingency costs are US$25 per Mg and US$38 per Mg of MSW for the government and private sector respectively at a 100% confidence interval. A 70% rise in collection tariffs or a minimum selling price of US$91/Mg of the hydrochar would ensure a positive NPV for the government-run operation.

The effect of recycling bin design on PET bottle collection performance.

Many municipalities in Japan have collected PET bottles as recyclable waste since 1980s. When caps are removed from bottles, it reduces collection and transportation costs because bottles can be easily compressed by collection trucks. However, PET bottles collected from recycling bins are usually capped and include other materials. This study designed 10 recycling bins for PET bottle to investigate the effect of design on cap removal efficiency and recycling contamination (foreign waste mixture). Recycling bins for PET bottle were designed focusing on four design items. They are (1) individual recycling bins specifically for bottles and caps or all-in-one recycling bin for both bottle and cap collections, (2) inside-visibility (see-through), (3) signage (wording like "Bottle" and "Cap") near insert slot and (4) insert slot shape. PET bottle collection performance of designed recycling bins was monitored in Suzukakedai campus of Tokyo Tech. Perceptive preferences of recycling bin designs and insert slot shapes were measured by online surveys. Experimental results indicate that insert slot with round shape contributed to significantly lower recycling contamination than bottle-like shape although perceptive preference of insert slots with bottle-like shape was higher than that of the round shape. Signage and all-in-one design is significantly effective to promote cap removal only when it was set with other recycling bins. On the other hand, signage is effective to decrease recycling contamination in a single setting. This study found that design effect depended on the setting condition of recycling bins in terms of cap removal and foreign waste disposal.

The effects of setting conditions of trash bins on waste collection performance and waste separation behaviors; distance from walking path, separated setting, and arrangements.

This study investigated the effects of setting conditions of trash bins on waste collection, separation efficiency, and incorrect disposal. Tested trash bins are for combustible wastes, PET bottles, cans, and glass bottles. Monitoring results were analyzed by statistical tests to distinguish real effects and experimental errors. The distance to trash bins along walking path gave no significant effects on waste collection and the others. On the other hand, when the distance was out of walking path, its increase significantly decreased waste collection of combustible wastes. In contrast, the distance gave no significant effect on separation efficiency and foreign waste percentage. It was suggested that threshold distance that affects waste disposal behaviors is between 8 and 410 m. When trash bins were set separately, it affected the motivation of waste separations. Separated setting of combustible waste and PET bottle trash bins in the opposite side of the original position significantly decreased separation efficiencies of these wastes. Because no significant effect was found on separation efficiency of other wastes whose trash bins were set in the original position, additional 3 m distance to the opposite side might exceed the threshold distance and have caused low separation efficiencies. The preference of trash bin arrangement gave no significant effect on waste collection and the others excluding separation efficiency of can. These results suggest that appropriate location of trash bins can improve waste collection and waste separation. It might be useful for waste management in public areas with high population density like shopping mall.

Preparation of high surface area sludge-based activated hydrochar via hydrothermal carbonization and application in the removal of basic dye.

Conventional methods to produce sludge activated carbon require high-energy due to high moisture content and poor dewaterability of the wet sludge. Recently hydrothermal carbonization (HTC) has been emerged as a promising thermo-chemical wet biowaste conversion technology for the valorization by converting these precursors into high value-added products such as a nanostructured carbon. In this study, sludge-based activated hydrochars (SAC) were prepared from high moisture content (88.9%) wastewater sludge (without pre drying) via HTC followed by physical (P-SAC) and chemical (C-SAC) activation with CO2 and KOH, respectively. Further, the effects of HTC temperatures (170, 200, 230 and 260 °C) and the activation methods on the physicochemical characteristics of hydrochar and SACs were investigated through ultimate analysis (CHNO), SEM, BET, BJH, FT-IR, Boehm back titration and zeta potential. The result showed that KOH-activation at 700 °C could significantly enhance the surface area of hydrochars (from 6.3 to 1613.9 m2/g) compared with CO2-activation even at 900 °C (261.6 m2/g). The mesopore P-SAC prepared from hydrochar at lower HTC temperature due to the presence of ash content. While, the negatively charged microspores C-SAC (VTotal: 0.88 cm3/g and Vmicro/VTotal: 73.3%) with high SBET was synthesized at higher HTC temperature. Prepared hydrochars were applied for the removal of a basic dye (such as methylene blue, MB) from aqueous solution. Based on Langmuir isotherm model (R2>99.4%), the maximum monolayer MB adsorption capacity of hydrochar, P-SAC and C-SAC were 63.3, 122.4, and 588.2 mg/g, respectively at pH > 8.0. The MB adsorption on C-SACs followed the pseudo-second-order kinetic model and a spontaneous endothermic reaction from 298 to 328 K. The commercial ACs also was compared with our materials and found that produced activated hydrochars showed superior results for MB removal. Therefore, HTC can be the potential carbonization method for wet biomass conversion to valuable carbonaceous material in a cost-effective way.

Physio-chemical effects of freshwaters on the dissolution of elementary mercury.

Elemental mercury (Hg0) is widely used by Artisanal and small-scale gold miners (ASGMs) to extract gold from ore. Due to the unavailability of appropriate waste disposal facilities, Hg0-rich amalgamation tailings are often discharged into nearby aquatic systems where the Hg0 droplets settle in bottom sediment and sediment-water interfaces. Hg0 dissolution and following biogeochemical transformations to methylmercury (MeHg) have been concerned owing to its potential risk to human health and the ecosystem. For reliable estimates of Hg exposure to human bodies using pollutant environmental fate and transport models, knowledge of the Hg0 dissolution rate is important. However, only limited literature is available. Therefore, it was investigated in this study. Dissolution tests in a 'dark chamber' revealed that an increase in medium pH resulted in a decrease in the dissolution rate, whereas, a large Hg0 droplet surface area (SA) and high Reynolds number (Re) resulted in a faster dissolution. A multivariate first order dissolution model of the form:kˆ=-7.9×10-5[pH]+7.0×10-4[logRe]+7.9×10-4[SA]-2.5×10-3 was proposed (adjusted R2 = 0.99). The Breusch-Pagan and White heteroscedasticity tests revealed that the model residuals are homoscedastic (p-value = 0.05) at the 5% significance level. Parameter sensitivity analysis suggests that slow mercury dissolution from the Hg0 droplets to aquatic systems might mask emerging environmental risk of mercury. Even after mercury usage in ASGM is banned, mercury dissolution and following contamination will continue for about 40 years or longer owing to previously discharged Hg0 droplets.

The effect of coal alternative fuel from municipal solid wastes employing hydrothermal carbonization on atmospheric pollutant emissions in Zimbabwe.

The vast increase of municipal solid waste (MSW) generated in Zimbabwe coupled with a severe energy crisis have made waste-to-energy technology more attractive and necessary. Coal-alternative solid fuel production from MSW though hydrothermal carbonization can play a critical role to improve both waste management and energy supply. Moreover, MSW conversion to a carbon neutral solid fuel that can be burnt in existing coal-fired power stations might reduce greenhouse gas (GHG) emissions despite GHG releases from waste collection, waste conversion to fuel, and fuel transportation processes. The purpose of this paper is to investigate present MSW generation in Zimbabwe, its characteristics as a fuel source, and the impact of coal-alternative solid fuel production from MSW using hydrothermal carbonization technology on GHG and other air pollutant emissions. Four different scenarios based on the balance between fuel supply and demand were tested in this paper. The results suggest 0.54 ±â€¯0.14 kg/capita/day of MSW generation in Zimbabwe and about 1051.7 ±â€¯270.7 Gg of annual MSW generation from the current urban population. 289.3 Gg of coal-alternative solid fuel production was expected from domestic MSW collectable in urban areas. The model predicted that co-burning of alternative fuel in coal-fired power plants could reduce the methane potential of household waste from 62,200 to 15,800 Mg CH4 per year. Under the best possible scenario, it could reduce SOx emissions by 4.2%, CH4 emissions by 4.5%, CO2 emissions by 3.1%, and Global Warming Potential by 2.2%. On the other hand, NOx emissions would increase by 18%. If without additional installation of air pollutant control devices in power plants, waste-to-energy generates a trade-off between global warming and acid rain. In addition, geological locations generate a large demand/supply gap of alternative fuel and regulate maximum available consumption of alternative fuel.

Characterization and application of microalgae hydrochar as a low-cost adsorbent for Cu(II) ion removal from aqueous solutions.

Hydrochar prepared from the hydrothermal liquefaction of microalgae is characterized and investigated for copper removal from aqueous solution. Two hydrochars were prepared at 210 °C (HD210) and 250 °C (HD250). The effect of the initial solution pH, the initial Cu(II) concentration, the contact time, and the temperature will be investigated. According to the elemental analysis, the volatile matter in the hydrochars was lower and ash content was higher than those of microalgae. Also, pore characteristic analysis revealed that the surface area of the HD250 was higher than that of the HD210 suggesting a higher potential for the adsorption process. FTIR analysis and Boehm titration showed that both hydrochars contained oxygen-containing functional groups (OFG) on the surface which were effective for the copper removal. The adsorption experiments indicated that the amount of copper adsorbed reached a maximum value at the pH of 5 which was considered as the optimum solution pH. In addition, HD250 had a higher amount of copper adsorption than that of HD210 at all values of the solution pH. The adsorption data at the optimum solution pH was well fitted by the Langmuir's isotherm model and the adsorption process could be well described by the pseudo-2nd order kinetic model. Moreover, thermodynamic analysis revealed that copper adsorption onto the hydrochar was a physical endothermic process.

Impact of secondary generated minerals on toxic element immobilization for air pollution control fly ash of a municipal solid waste incinerator.

Impacts of secondary generated minerals on mineralogical and physical immobilization of toxic elements were investigated for chelate-treated air pollution control (APC) fly ash of a municipal solid waste incinerator. Scanning electron microscope (SEM) observation showed that ettringite was generated after the moistening treatment with/without chelate. Although ettringite can incorporate toxic elements into its structure, elemental analysis by energy dispersive X-ray could not find concentrated points of toxic elements in ettringite structure. This implies that mineralogical immobilization of toxic element by the encapsulation to ettringite structure seems to be limited. Physical immobilization was also investigated by SEM observation of the same APC fly ash particles before and after the moistening treatment. The transfer of soluble elements was inhibited only when insoluble minerals such as gypsum were generated and covered the surface of fly ash particles. Neoformed insoluble minerals prevented soluble elements from leaching and transfer. However, such physical immobilization seems to be limited because insoluble mineral formation with surface coverage was monitored only one time of more than 20 observations. Although uncertainty owing to limited samples with limited observations should be considered, this study concludes that mineralogical and physical immobilization of toxic elements by secondary minerals is limited although secondary minerals are always generated on the surface of APC fly ash particles during chelate treatment.

Geochemically structural characteristics of municipal solid waste incineration fly ash particles and mineralogical surface conversions by chelate treatment.

Leaching behaviors of heavy metals contained in municipal solid waste incineration (MSWI) fly ash have been studied well. However, micro-characteristics of MSWI fly ash particles are still uncertain and might be non-negligible to describe their leaching behaviors. Therefore, this study investigated micro-characteristics of MSWI fly ash particles, especially their structural properties and impacts of chelate treatment on surface characteristics. According to SEM observations, raw fly ash particles could be categorized into four types based on their shapes. Because chelate treatment changed the surface of fly ash particles dramatically owing to secondary mineral formations like ettringite, two more types could be categorized for chelate-treated fly ash particles. Acid extraction experiments suggest that fly ash particles, tested in this study, consist of Si-base insoluble core structure, Al/Ca/Si-base semi-soluble matrices inside the body, and KCl/NaCl-base soluble aggregates on the surface. Scanning electron microscope (SEM) observations of the same fly ash particles during twice moistening treatments showed that KCl/NaCl moved under wet condition and concentrated at different places on the particle surface. However, element mobility depended on secondary mineral formations. When insoluble mineral like gypsum was generated and covered the particle surface, it inhibited element transfer under wet condition. Surface characteristics including secondary mineral formation of MSWI fly ash particles are likely non-negligible to describe trace element leaching behaviors.

Atmospheric mercury emissions from waste combustions measured by continuous monitoring devices.

Atmospheric mercury emissions have attracted great attention owing to adverse impact of mercury on human health and the ecosystem. Although waste combustion is one of major anthropogenic sources, estimated emission might have large uncertainty due to great heterogeneity of wastes. This study investigated atmospheric emissions of speciated mercury from the combustions of municipal solid wastes (MSW), sewage treatment sludge (STS), STS with waste plastics, industrial waste mixtures (IWM), waste plastics from construction demolition, and woody wastes using continuous monitoring devices. Reactive gaseous mercury was the major form at the inlet side of air pollution control devices in all combustion cases. Its concentration was 2.0-70.6 times larger than elemental mercury concentration. In particular, MSW, STS, and IWM combustions emitted higher concentration of reactive gaseous mercury. Concentrations of both gaseous mercury species varied greatly for all waste combustions excluding woody waste. Variation coefficients of measured data were nearly equal to or more than 1.0. Emission factors of gaseous elemental mercury, reactive gaseous mercury, and total mercury were calculated using continuous monitoring data. Total mercury emission factors are 0.30 g-Hg/Mg for MSW combustion, 0.21 g-Hg/Mg for STS combustion, 0.077 g-Hg/Mg for STS with waste plastics, 0.724 g-Hg/Mg for industrial waste mixtures, 0.028 g-Hg/Mg for waste plastic combustion, and 0.0026 g-Hg/Mg for woody waste combustion. All emission factors evaluated in this study were comparable or lower than other reported data. Emission inventory using old emission factors likely causes an overestimation.