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The effects of sewage sludge phosphorus (P) content on heavy metal behavior during co-incineration of sewage sludge and municipal solid waste (MSW) were evaluated. Thermogravimetric differential thermal analysis revealed that MSW incineration was mainly caused by organic matter and fixed carbon, while sewage sludge incineration was caused by volatile matter. During co-incineration, the peak weight loss at 460 °C shifted to slightly higher temperatures and the sludge ratio increased, indicating that interaction effects during co-incineration delayed pyrolysis and polymer/fixed carbon incineration. The residual heavy metal ratios after mono-incineration of sewage sludge were higher than those after MSW mono-incineration. The Cl content of MSW (0.757%) was much higher than that of sewage sludge (0.068%), which resulted in the conversion of heavy metals into metal chlorides and then volatilized during MSW mono-incineration. A synergistic effect of co-incineration was evident for Cu, but not for lead (Pb) or cadmium (Cd). X-ray absorption fine structure (XAFS) measurement revealed that Cu in MSW ash was in the form of CuO(s), but was Cu

Japan has entered a period of depopulation and aging ahead of any other country. One concern in an aging population is increases in the generation of used disposable diapers. The use of disposable diapers, which are largely composed of plastic, can be an important issue as we work towards building a carbon-free society and break away from using fossil-derived plastics. This study aimed to develop a model to project the future generation of used disposable diapers in each municipality in Japan through 2045 and to identify the effects on municipal solid waste (MSW) management. We revealed the per capita generation of used disposable diapers, distinguishing disposable diaper products, urine and faeces in an online survey of 2000 respondents. The generation of used disposable diapers was estimated to increase in general, but the amount was projected to decrease in rural areas where the population of elderly people would decline. The proportion of used disposable diapers in combustible waste was projected to increase by 2045 in almost all municipalities of Mie Prefecture. Based on the scenario in which disposable diaper products would become lighter in the future because of technical improvements, we concluded that the impact of the decrease in the lower heating value (LHV) of used disposable diapers on the incineration process cannot be ignored in the future.

Biogas is a promising renewable biofuel, but hydrogen sulfide (H2S) and siloxanes are major obstacles in the conversion of bioenergy from biogas because they damage biogas-processing equipment. This study evaluated two biogas-purification systems for a simultaneous efficient removal of H2S and decamethylcyclopentasiloxane (D5), and compared their economic performance. An acidic biotrickling filter (BTF) was operated continuously for 90 days to investigate its performance under different H2S and D5 concentrations. Meanwhile, commercial iron-oxide-based adsorbents (IOBAs) and activated carbon (AC) were used in adsorption filters for H2S and D5, respectively. The results show that in terms of the ratio of D5 and H2S concentration (RD5:H2S) and pH of the recycling liquid, which are crucial BTF operating parameters, high elimination for both H2S (1.86 kg/(m3·d)) and D5 (0.282 kg/(m3·d)) was achieved at RD5:H2S of 3.7:16 and pH of 0.86. Economic analysis confirmed that BTF-AC was more profitable than IOBA-AC adsorption over a life span of 10 years because the pre-removal of D5 by a BTF significantly decreased the costs of IOBAs and AC, despite BTFs requiring a higher initial capital investment. In terms of the economic benefit of biogas production of 1200 Nm3/h, the competitive annual cost of 90.5 k$/year indicated that BTF was more profitable, yielding both cost saving and the benefit of providing heat. The advantage of BTF-AC adsorption was a more radical D5-abatament, enabling profit by selling the electricity produced from biogas to the grid.

The emissions from crematoria have been identified as a source of mercury not currently being remediated. However, the effects of changing the operational conditions by installing a fabric filter (FF) to remove mercury from the flue gas of a crematorium have not been examined in detail. In this study, the mercury concentrations of crematoria flue gases before and after passing through a pre-treated FF and a selective catalytic reactor (SCR) were recorded via continuous emission monitors to examine the effect of pre-injecting a mixture of lime and 10 % activated carbon into the flue. After the filter was installed and treated, mercury concentrations at the outlet of the SCR were very low, with a maximum of less than 5 μg/Nm3. The mercury removal efficiency ranged from 87.5–99.9%. The thick layer of lime and activated carbon on the surface of the FF effectively suppressed the peak mercury concentration at the outlet of the SCR. The relationship between the average mercury concentration at the inlet of the FF and the age of the person at death indicates that the age at death could be a key factor in controlling mercury emissions from a crematorium.

Background Recent studies of lipid extraction from microalgae have focused primarily on dewatered or dried samples, and the processes are simple with high lipid yield. Yet, the dewatering with drying step is energy intensive, which makes the energy input during the lipid production more than energy output from obtained lipid. Thus, exploring an extraction technique for just a thickened sample without the dewatering, drying and auxiliary operation (such as cell disruption) is very significant. Whereas lipid extraction from the thickened microalgae is complicated by the high water content involved, and traditional solvent, hence, cannot work well. Dimethyl ether (DME), a green solvent, featuring a high affinity for both water and organic compounds with an ability to penetrate the cell walls has the potential to achieve this goal. Results This study investigated an energy-saving method for lipid extraction using DME as the solvent with an entrainer solution (ethanol and acetone) for flocculation-thickened microalgae. Extraction efficiency was evaluated in terms of extraction time, DME dosage, entrainer dosage, and ethanol:acetone ratio. Optimal extraction occurred after 30 min using 4.2 mL DME per 1 mL microalgae, with an entrainer dosage of 8% at 1:2 ethanol:acetone. Raw lipid yields and its lipid component (represented by fatty acid methyl ester) contents were compared against those of common extraction methods (Bligh and Dryer, and Soxhlet). Thermal gravimetry/differential thermal analysis, Fourier-transform infrared spectroscopy, and C/H/N elemental analyses were used to examine differences in lipids extracted using each of the evaluated methods. Considering influence of trace metals on biodiesel utilization, inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectroscopy analyses were used to quantify trace metals in the extracted raw lipids, which revealed relatively high concentrations of Mg, Na, K, and Fe. Conclusions Our DME-based method recovered 26.4% of total raw lipids and 54.4% of total fatty acid methyl esters at first extraction with remnants being recovered by a 2nd extraction. In additional, the DME-based approach was more economical than other methods, because it enabled simultaneous dewatering with lipid extraction and no cell disruption was required. The trace metals of raw lipids indicated a purification demand in subsequent refining process.

Flocculation showed the potential for harvesting microalgae at a low cost. The inorganic flocculant (AlCl3) and organic flocculant (chitosan) are two representative and common flocculants, which were suited for different conditions (pH, salinity, and cell density). To investigate the effects of the three factors on the flocculation performance of the two flocculants, especially for the interaction effects among these factors, single-factor experiments and response surface methodology (RSM) were conducted. The results indicated that AlCl3 performed better under alkaline conditions, whereas chitosan showed better performance at acidic pH. Salinity had little influence on the flocculation efficiency (FE) of AlCl3. By contrast, increasing salinity reduced the FE of chitosan, especially above 8.4 g/L. As cell density increased, the optimal dosage of AlCl3 increased to a constant ~ 26 g/L. In contrast, the optimal dosage of chitosan continuously increased within the studied range. Also, RSM revealed significant interaction effects of [salinity][cell density] for AlCl3, due to which AlCl3 showed a good flocculation performance under either high cell density or high salinity conditions but poor with both high together. Significant interaction effects of [salinity][cell density] for chitosan was observed, and one of the two factors hence alleviated the negative influence from the other. Considering their performance under the different condition and the interaction effects, dual flocculation with AlCl3 + chitosan on multiplex conditions was evaluated, and the results indicated that higher FE with wider applicability could be achieved with lower dosages of the dual flocculant compared with utilization of the two flocculants individually under most of the conditions.

We investigated the distribution of 18 elements including non-volatiles (Al, P, Ca, Fe, Mg, K, Mn, Cu, Na, Cr, and Ni), semi-volatiles (Zn, Pb, Ag, As, and Cd), and volatiles (Hg and S) and compared their behaviors in two types of full-scale sewage sludge mono-incinerators, namely, a step-grate stoker (GS) and two fluidized bed incinerators (F-types), with the same feed sludge. Most of the non-volatile elements were enriched five-fold in all incinerated sewage sludge ash (ISSA), while the volatile S and Hg were barely enriched in ash due to the combustion components generated in the gas phase. While the semi-volatile elements were also enriched five-fold in the F-types, a different enrichment behavior was observed in the GS. Boiler and multi-cyclone dust in the GS showed higher enrichments of Pb and Cd compared to ash due to the combined effects of lower temperature and smaller particle size. Compared to the F-types, the GS generated ashes with lower toxicity as the major component (99.7%) and hazardous dust as the minor component. In the future, more attention should be paid to grate stokers in terms of recycling ISSA.

Liquefied dimethyl ether (DME) was used to extract lipids from sewage sludge. Factorial experimental analyses were used to evaluate the influence of different variables on raw lipid extraction and sludge drying. The DME method was compared with the Bligh and Dyer (BD) method for three undigested and two anaerobically digested dewatered sludges. The results indicate that although the raw lipid yield of the BD method was 5% higher than that of the DME method, the proportion of fatty acid methyl esters (FAMEs) in raw lipids extracted by the DME method was 14.1-33.4%, almost twice that of the BD method. The FAME composition varied according to sludge type, and the dewatered undigested sludges contained more unsaturated fatty acids (e.g. C18:1, C18:2). The lower heating value (LHV) of product by the DME method ranged from 3.74 to 5.70 MJ/kg compared with 1.21-0.39 MJ/kg for the BD method. Also, DME could be reused at least five times without significantly reducing the lipid yield and drying efficiency. Finally, an economic analysis of the DME, the conventional solvent extraction, and the heat-drying methods was conducted.

We evaluated mercury (Hg) behavior in a full-scale sewage sludge torrefaction plant with a capacity of 150 wet tons/day, which operates under a nitrogen atmosphere at a temperature range of 250–350 °C. Thermodynamic calculations and monitoring results show that elemental Hg (Hg0) was the dominant species in both the pyrolysis gas during the torrefaction stage and in the flue gas from downstream air pollution control devices. A wet scrubber (WS) effectively removed oxidized Hg from the flue gas and moved Hg to wastewater, and an electrostatic precipitator (ESP) removed significant particulate-bound Hg but showed a limited capacity for overall Hg removal. Hg bound to total suspended solids had a much higher concentration than that of dissolved Hg in wastewater. Total suspended solid removal from wastewater is therefore recommended to reduce Hg discharge. Existing air pollution control devices, which consist of a cyclone, WS, and ESP, are not sufficient for Hg removal due to the poor Hg0 removal performance of the WS and ESP; a further Hg0 removal unit is necessary. A commercial packed tower with sorbent polymer catalyst composite material was effective in removing Hg (83.3%) during sludge torrefaction.

Biological in-situ biogas upgrading is a promising approach for sustainable energy-powered technologies. This method increases the CH

To better understand the general behavior of heavy metals in semi-aerobic incinerator residue landfills, we developed a general equation for calculating the mass balance of heavy metals (cadmium, lead, copper, zinc, mercury, and chromium) based on monitoring data from incineration plants and landfill sites. The mass balance results showed that 0.0042%, 0.001%, 0.0004%, 0.0019%, 0.022%, and 0.0065% of the disposed Cd, Pb, Cu, Zn, Hg, and Cr, respectively, were washed out by rainfall from 1975 to 2015. Heavy metals (Cd, Cr, and Hg) with a lower total mass in the landfill had a relatively high total leaching rate. This may be because of the high pH of the landfill, which affected the leaching of Pb, Zn, and Cu. According to our analysis of the changes in annual leaching rates at this landfill site, there was an obvious change in those of Cu, Zn, and Pb after 1989, when the pH of the leachate increased suddenly. The overall annual leaching rate became more stable, at around 0.00002%, following closure of the landfill site, and it is believed that the dissolvable fraction and heavy metal concentration in the leachate are expected to reach a limit under the current conditions.

This study investigated core samples from a landfill site for incinerator residue. The landfill site is one of the first monofill sites for municipal solid waste incinerator residue in the world. The concentrations of the heavy metals Cd, Cr, Cu, Pb, Zn, and Ni in the landfilled incinerator residues were 1–108, 41–926, 40–5498, 35–9806, 103–11453, and 25–719 mg/kg, respectively. Based on comparisons of heavy metal contents between raw incinerator fly ash and bottom ash reported in the literature, our samples comprised a mixture of incinerator fly ash and bottom ash. Rainfall had removed the dissolvable salts from the incinerator residues. The compositions of incinerator residues from different locations varied markedly. The vertical distribution showed a high heavy metal content in the waste layers, suggesting no vertical movement of heavy metals in this landfill site. A comparison between the experimental data and data calculated from historic records of the original metal compositions of the incinerator residues suggested high mobility of Zn, Cu, and Pb and low mobility of Cr and Cd. This trend was supported by a leaching test of waste layer samples. Zn and Cu were leached more readily at pH 9.0–10.0 and 10.5–11.5, respectively.

With the increasing production of spent bleaching clay (SBC), the recovery of the waste oil in SBC is becoming an important and urgent needs for our environment and economy. In this research, we have developed a new effective recovery technique to recover oil from SBC by use of liquefied dimethyl ether (DME). Over 65 wt% oil and 81% wt.% oil are efficiently recovered from SBC under equilibrium single-stage extraction conditions and multi-stage extraction conditions, respectively based on the systematically investigation to the effects of the DME/SBC ratio, extraction time, stirring speed and extraction stage number on oil recovery via a batch extractor. Compared with using other extraction solvents, the extraction solvent DME can be reused without heating and therefore significantly reduce the energy consumption during the oil recovery process. In addition, the quantitative oil extraction relationship is derived from the adsorption equilibrium model and is well verified by experimental results. The results show a great potential for using this oil recovery technique in SBC as well as in the large amount of oily sludge and oil sands.

Biodiesel produced from microalgae is a potential alternative due to the high growth rate of microalgae, the possibility of using nonarable land, and high lipid accumulation rate. Microalgae cultivation, cell harvesting and disruption are the important steps before lipid extraction for the biodiesel. In the co-submission article, the details of the whole process cannot be clearly explained. In this regard, we present the details of methods on parameter of photo-bioreactor for cultivating microalgae, flocculation tests to determine optimal flocculant dosage in harvesting, parameter of Dimethyl ether (DME) subcritical extraction device and full-factorial design for investigating the influence of extraction time, initial water content and DME dosage on the extraction performance. It will allow researchers to reproduce these experiments. • The method shows a cell disruption assisted lipid extraction by subcritical dimethyl ether. • Model is built from full-factorial design to investigate multi-factor influence. • Differential scanning calorimetry can be applicable to measure free water content., Graphical abstract Image, graphical abstract

Subcritical dimethyl ether, a green solvent, was used to extract lipids from microalgae. The effect of the water content on the process was firstly investigated. Secondly, microalgal samples were subjected to five cell disruptions, and the effects on raw lipid and fatty acid methyl ester, and its profile were evaluated. Among them, heating, microwave, and ultrasonic treatments greatly improved extraction. Mechanism analysis revealed the improvements by the three treatments were due to increased cell wall permeability rather than to complete cell disruption. After the extraction, microalgal cells with lipid being well-extracted were shriveled with extensive surface folds, indicating a loss of intracellular substances, but the cell structure was undamaged. As for dewatering performance, extraction process removed almost all of the free water but left bound water. Finally, the potential of the residues after lipid extraction to serve as solid fuel was evaluated by combustion characteristics and heating value calculation.

Background: Recent studies of lipid extraction from microalgae have focused primarily on dewatered or dried samples, and the processes are simple with high lipid yield. Yet, the dewatering with drying step is energy-intensive, which makes the energy output from the extracted lipid is less than the energy needed to produce it. Thus, exploring an extraction technique for just a thickened sample without the dewatering, drying and auxiliary operation (such as cell disruption) is very significant. Whereas lipid extraction from the thickened microalgae is complicated by the high-water content involved, and traditional solvent hence cannot work well. Dimethyl ether (DME), a green solvent, featuring a high affinity for both water and organic compounds with an ability to penetrate the cell walls, has the potential to achieve this goal. Results: This study investigated an energy-saving method for lipid extraction using DME as the solvent with an entrainer solution (ethanol and acetone) for flocculation thickened microalgae. Extraction efficiency was evaluated in terms of extraction time, DME dosage, entrainer dosage, and ethanol:acetone ratio. Optimal extraction occurred after 30 minutes using 4.2 mL DME per 1 mL microalgae, with an entrainer dosage of 8% at 1:2 ethanol:acetone. Raw lipid yields and fatty acid methyl ester contents were compared against those of common extraction methods (Bligh & Dryer and Soxhlet). Thermal gravimetry/differential thermal analysis, Fourier-transform infrared spectroscopy, and C/H/N elemental analyses were used to examine differences in lipids extracted using each of the evaluated methods. Considering influence of trace metals on biodiesel utilization, inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectroscopy analyses were used to quantify trace metals in the extracted raw lipids, which revealed relatively high concentrations of Mg, Na, K, and Fe.Conclusions: Our DME-based method recovered 26.4% of total raw lipids and 54.4% of total fatty acid methyl esters at first extraction with remnants being recovered by a 2nd extraction. In additional, the DME-based approach was more economical than other methods, because it enabled simultaneous dewatering with lipid extraction and no cell disruption was required. The trace metals of raw lipids indicated a purification demand in subsequent refining process.

A response surface methodology was used to investigate the flocculation performance of an amphoteric flocculant (acrylamide-methacrylic acid ester-acrylic acid copolymer [ACPAM]) for harvesting microalgae. After three potential influencing factors (pH, dosage, and the stirring speed of an intensive mixing step ω1) passed screening in experiments using a Plackett–Burman design, steepest ascent experiments were conducted to identify the parameters for Box–Behnken assessments. In those assessments, ω1, dosage, ω12, dosage2, and ω1 ∙ dosage were identified as significant factors. This model was optimized by removing nonsignificant factors and applying Box–Cox transformation, both of which significantly improved the adequacy of the model. An optimized set of conditions (pH = 9.0, ω1 = 339.3 rpm, and dosage = 28.54 mg/L) was obtained under which flocculation efficiency (FE) was predicted to be 95.85% and 98.00% for the nonsignificant factors removed and Box–Cox transformed models, respectively, compared to an experimentally determined value of 98.06%. Thermal stability analyses showed that the ACPAM was generally stable below 100 °C with some weight loss caused by moisture evaporation. However, crosslinking of its molecules by imidization and condensation started to occur at 120 °C, resulting in a lower flocculation performance. Finally, the applicability of the ACPAM was studied by comparing its FE to those of two other flocculants (AlCl3 and chitosan) when harvesting three microalgal species. The results showed flocculation performance of ACPAM varied with microalgae species, for one species the ACPAM dosage needed was highest while for another species, the dosage was lowest.

The elemental composition of 120 dewatered sludge samples from 32 wastewater treatment plants in Japan was analyzed, and the influential factors determining sludge elemental composition were clarified. Through Hayashi's quantification method I, the relationship and influence of each element to the dominant categories were confirmed, and the correlation between the elements was also analyzed. The Van Krevelen diagram was used to determine the similarity in organic contents between sludge and biomass/fossil fuels. Principal component and cluster analyses were used to verify the identification of influential factors. Finally, a standard composition of dewatered sludge in Japan was defined based on different sewage collection systems and digestion processes, shown to have the greatest influence on sludge composition. The potential of sludge for agricultural and cement industrial recycling was also assessed.

Biodiesel is a promising renewable fuel with many attractive features such as high combustion efficiency, biodegradability, and less toxic exhaust emission. This study investigated an environmentally friendly method for biodiesel production from refined rice bran oil (RRBO) using calcium oxide (CaO) from eggshell waste as a catalyst via transesterification reaction. A two-level three-factor full factorial experimental design was used to determine the effect of the impregnation of silver nanoparticles (AgNPs), calcination temperature and heating rate as independent variables on the biodiesel yield. Results showed that the calcination heating rate and the impregnation of AgNPs had significant effects on the biodiesel yield. An optimum biodiesel yield of about 92% was obtained using AgNPs impregnated CaO catalyst prepared from eggshell waste using a heating rate of $5^{\circ}\displaystyle \mathrm{C}/\min$ during calcination at temperatures in 800-$1000^{\circ}\mathrm{C}$ range.

There is an urgent need to dispose safely of the municipal solid waste incineration fly ash (MSWIFA) contaminated by cesium (Cs) released from the Fukushima Daiichi nuclear power plant accidents. This study investigated the relationship between quantitative Cs speciation and Cs immobilization in composite product from alkali-activated pyrophyllite and MSWIFA, with added stable cesium chloride and cesium carbonate. Cesium speciation was determined using X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS), while Cs immobilization was evaluated by a leaching method. Twenty-four composite products, with different Cs leaching properties, were prepared under various conditions. The XRD analysis of six composite products with different Cs leaching properties qualitatively identified a crystalline pollucite in the two products with the least Cs leaching. The quantitative speciation determined using XAFS revealed a strong negative correlation between the pollucite content in the 24 products and their Cs leaching ratio. Cesium species with a Cs O bond were found in all products. These were at least two Cs species with different leaching properties. These results indicate that the change from a Cs species to pollucite in the product increased the Cs immobilization level in the system.

Due to a decrease in phosphorus (P) and potassium (K) mining, manure is incinerated to concentrate P and K in ash. To understand the alternative use of manure-derived ash as P and K sources, laboratory and greenhouse experiments were conducted to determine the relationship between extractability and P and K uptake in cattle manure ash (CMA) and that between CMA application and a grass tetany hazard. The results showed that more P was extracted with 2% citric acid (90% of the total P) than with 2% formic acid (72–84% of the total P). Ninety-one percent of the total K was soluble in water. A greenhouse pot experiment was conducted to test P and K availability to Guinea grass (Megathyrsus maximus). Cattle manure ash or calcium dihydrogen phosphate (CF) was incorporated into sandy soil at 10, 20, and 50 g P2O5 m−2. Two combinations of CMA and CF were tested at 20 g P2O5 m−2. Potassium rates followed K content in CMA applied at different rates of P equivalent to 19, 38, or 96 g K2O m−2. In four harvest...

Environmentally sound treatments are required to dispose of municipal solid waste incineration fly ash (MSWIFA) contaminated with radioactive cesium (Cs) from the Fukushima Daiichi nuclear power plant accident in Japan. This study focuses on the stabilization of Cs using an alkali-activated MSWIFA and pyophyllite-based system. Three composite solid products were synthesized after mixtures of raw materials (dehydrated pyrophyllite, MSWIFA, 14 mol/L aqueous sodium hydroxide, and sodium silicate solution) were cured at 105 °C for 24 h. Three types of MSWIFAs were prepared as raw fly ash, raw fly ash with 0.1% CsCl, and raw fly ash with 40% CsCl to understand the stabilization mechanism of Cs. Cs stabilization in two solid products was successful, with less than 6.9% leaching observed from two types tests, and was partly successful for the solid product with the highest concentration of Cs. X-ray diffraction showed that all of the solid products produced several crystalline phases, and that pollucite was formed in the highest Cs concentration product. The X-ray absorption fine structure and scanning electron microscopy with X-ray analysis suggested that most Cs species formed pollucite in the two solid products from MSWIFA with added CsCl. This system provides a technique for the direct stabilization of Cs in MSWIFA.

Excessive application of animal manure to farmland leads to phosphorus (P) loss into the surrounding water. Manure is incinerated to convert it to P-rich ash as a slow-release P fertilizer. However, the potential P loss and P availability for plants from cattle manure ash (CMA) have not been fully understood. The aims of this study were to determine the P release mechanism from CMA and to propose appropriate application rates that mitigate P loss and increase available P to soil in Fukushima, where the soil is deficient in nutrients after the replacement of cesium-137-contaminated soil with sandy mountain soil. Different P fractions in CMA were sequentially extracted with H2O, 0.5 M NaHCO3, 0.1 M NaOH, and 1 M HCl. Phosphorus contents in different fractions of CMA were in the order of HCl–P > NaHCO3–P > H2O–P > NaOH–P. Water-soluble P release of CMA was also determined by kinetic experiments for 120 h. Results showed that total water-soluble P accounted for a maximum of 2.9% of total P in CMA over...

We conducted in situ X-ray absorption fine structure (in situ XAFS) analysis at the Cs K-edge to investigate the chemical kinetics of Cs species during reaction in an alkali-activated municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite-based system. Understanding the kinetics of Cs is essential to the design of appropriate conditions for Cs stabilization. In situ XAFS analysis of four pastes, prepared from NaOH aq , sodium silicate solution, pyrophyllite, and MSWIFA with the addition of CsCl, was conducted in custom-built reaction cells at four curing temperatures (room temperature, 60 °C, 80 °C, 105 °C) for approximately 34 h. The results indicated that the change in Cs species during reaction at room temperature was small, while changes at higher temperatures were faster and more extreme, with the fastest conversion to pollucite occurring at 105 °C. Further analysis using a leaching test and a simple reaction model for Cs species during reaction showed that the pollucite formation rate was dependent on the curing temperature and had a significant negative correlation with Cs leaching. The activation energy of pollucite formation was estimated to be 31.5 kJ/mol. These results revealed that an important change in the chemical state of Cs occurs during reaction in the system.

Environmental pollution and human health issues due to unrestricted electronic waste (e-waste) recycling activities have been reported at a number of locations. Among different e-waste recycling techniques, open burning of e-waste releases diverse metal(loid)s into the environment, which has aroused concern worldwide. In human health risk assessments (HHRAs), oral ingestion of soil can be a major route of exposure to many immobile soil contaminants. In vitro assays are currently being developed and validated to avoid overestimation of pollutants absorbed by the human body when calculating total pollutant concentrations in HHRAs. In this study, Cu, As, Cd, Sb, and Pb bioaccessibility in polluted soils (n = 10) from e-waste open burning sites at Agbogbloshie in Accra, Ghana, was assessed using an in vitro assay, the physiologically based extraction test. A bioaccessibility-corrected HHRA was then conducted to estimate the potential health risks to local inhabitants. The in vitro results (%) varied greatly among the different metal(loid)s (Cu: 1.3–60, As: 1.3–40, Cd: 4.2–67, Sb: 0.7–85, Pb: 4.1–57), and also showed marked variance between the gastric phase and small intestinal phase. The particle sizes of soil samples and chemical forms of metal(loid)s also influenced bioaccessibility values. Using these bioaccessibility values, both the hazard index and carcinogenic risk were calculated. The hazard index was above the threshold value (>1) for 5/10 samples, indicating a potential health risk to local inhabitants. Refereed/Peer-reviewed

The feasibility of simultaneous removal of siloxane and H

We explored the effects of gas emission by mixtures undergoing alkali-activation of municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite (the mixtures included dehydrated pyrophyllite, MSWIFA, 14 mol/L aqueous sodium hydroxide, and sodium silicate; curing proceed at 105 °C for 24 h). We measured the compressive strengths of the derived solid composites. The causes of gas emission, and the physical and chemical properties of products created under controlled gas emission, were investigated. Hydrogen was emitted after mixing MSWIFA and alkali. The compressive strength of products prepared when gas emission was complete was 2–3.4-fold greater than that of products prepared when gas emission was incomplete. X-ray micro-tomography and mercury intrusion porosimetry showed that products formed during complete gas emission tended to have smaller pores. X-ray diffraction and nuclear magnetic resonance (27Al and 29Si) indicated that the aluminum substitution levels in tectosilicate differed under such conditions, although the minerals were identical. Thus, complete gas emission after mixing improved ultimate products.

The flocculation performances of AlCl3, chitosan, amphoteric polyacrylamide (acrylamide-methacrylic acid ester-acrylic acid copolymer [ACPAM]), and NaOH for eight microalga species were investigated. AlCl3 had wide application for both freshwater and marine microalgae while NaOH could only flocculate marine microalgae. By contrast, chitosan was very effective to freshwater species with low dosage demand; ACPAM was only valid for three freshwater species. The settling times, concentration factors (CF), and capillary suction times (CST) were measured. The settling times with ACPAM (0.5–0.6 min) were the shortest while flocculation by NaOH had the longest settling times (13–40 min). The CF determined the volume of microalgae slurry, which in turn affected dewatering. The CST was used to evaluate polyacrylamide (PAM) demand in dewatering (filter press) using a model developed in this study. Life-cycle assessment identified the optimal harvesting methods for the eight species using data from this study and the literature. The analyses revealed that chitosan flocculation + filter press was the best approach for five species and AlCl3 flocculation + filter press or two-step centrifugation was optimal for the remaining three species. Coccomyxa sp. K.J., Chlorella vulgaris, and Tetradesmus obliquus were screened for biodiesel production in consideration of the environmental impact and their lipid contents.

This paper studies the synergism between transition metals (TMs) and activated carbon (AC) as a catalyst support used in the catalytic decomposition of PCBs. A series of AC-supported TM catalysts was prepared according to two distinct methods: impregnation and ion exchange which were defined as LaTM-C and IRTM-C, respectively. The catalytic reactions between 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153) and AC-supported Fe, Ni, Cu and Zn catalysts were conducted under N2 atmosphere. Changes in the nature of the catalysts as well as the decomposition mechanism of PCB-153 are discussed. Important findings include: (i) a higher metal concentration and a better metal distribution on AC is realized using ion-exchange, despite a lower AC specific surface area, (ii) IRTM-C had better effects on the decomposition of PCB-153 than LaTM-C, (iii) the role of Ni, Cu, and Fe as electron donors in PCB dechlorination was evaluated vs. the stability of Zn, and (iv) both temperature and chemical composition of TM catalysts influenced the decomposition efficiency of PCBs.

Ash produced from the combustion of livestock manure contains large amounts of phosphorus (P), which is an important resource as a fertilizer. Some studies have extracted and recovered P from incinerated biomass ash using inorganic acid or alkaline agents, which produce wastewater that requires treatment and is expensive due to the cost of chemicals. Livestock manure ash contains not only P, but also water soluble salts, which could be a negative influence on plant growth and shall be preferably removed from the recovered fertilizer. In this study, we removed salinity from cattle manure incineration ash by simple aqueous leaching, while retaining the P content. The optimal condition was a 20 min leaching time at a liquid/solid (L/S) ratio of 10 mL g-ash−1. Under this condition, over 90 % of Cl and 20 % of Na in the original ash was removed, while over 99 % of the P was retained in the leached residue. The leached residue met the fertilizer standard in Japan in terms of citrate soluble fertilizer components and contained few heavy metals. X-ray analyses of the ash indicated that Cl was mainly present as KCl in the original ash, while P was mainly present as Ca compounds in the ash.