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1.
Bioresour Technol ; 302: 122850, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32007849

RESUMO

This study analyzed the chemical speciation, leaching ability, and environmental risk of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in cow manure biochar (CMBC) pyrolyzed at various temperatures. The total content, chemical speciation, and leaching ability of the heavy metals were determined through microwave digestion, modified BCR three-step sequential extraction procedure, and leaching solution systems (TCLP, distilled water, and SPLP). The risk assessment code, Muller geo-accumulation index, potential ecological risk index, and germination index were used to evaluate the environmental safety and ecotoxicity of heavy metals. Significant differences were observed in the physicochemical properties of CMBCs. The heavy metal contents in CMBCs were higher than those in CM. The bioavailable fraction of heavy metals was transformed into a relatively stable fraction with increasing pyrolysis temperature. Furthermore, the potential risks and ecotoxicity of biochar were reduced, thus improving environmental safety. The study results provide important data for biochar applications.


Assuntos
Esterco , Metais Pesados , Animais , Bovinos , Carvão Vegetal , China , Monitoramento Ambiental , Feminino , Pirólise , Medição de Risco , Temperatura Ambiente
2.
J Environ Manage ; 259: 110018, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32072959

RESUMO

In the study, the dynamics of Sr2+ and geochemically correlated elements (Ca2+, Ba2+, and Y3+) in soil with chelators in the mix (soil to chelator ratio, 1:10; matrix, H2O) were assessed to understand chemical-induced washing remediation of radiogenic waste solids. Specifically, EDTA (2,2',2″,2‴-(ethane-1,2-diyldinitrilo)tetraacetic acid), EDDS (2-[2-(1,2-dicarboxyethylamino)ethylamino]butanedioic acid), GLDA (2-[bis(carboxymethyl)amino]pentanedioic acid), and HIDS (2-(1,2-dicarboxyethylamino)-3-hydroxy-butanedioic acid) are chelators that are used as extractants. The effect of solution pH on chelator-induced extractions of the target elements (t-Es: Sr2+, Ca2+, Ba2+, or Y3+) from soil and stability constants of the t-Es complexes with chelators were used to explain the trends and magnitudes in interactions. Pre- and post-extractive solid-phase speciation was used to define the extent of the competence of each chelator in persuading dissolution of t-Es in the soil. The effects of ultrasonic energy, admixtures of biodegradable chelators, and excess chelators in solution (1:20) were also analyzed on the extractive removal of t-Es from soil. The results indicate that the Sr2+ removal with biodegradable chelators significantly exceeded (approximately 70%) when compared to that of environmentally-persistent EDTA at lower solution pHs and a higher soil to chelator ratio (GLDA > HIDS > EDDS ≈ EDTA). However, the extraction of the geochemically related element was significantly lower.


Assuntos
Recuperação e Remediação Ambiental , Metais Pesados , Poluentes do Solo , Quelantes , Ácido Edético , Solo , Estrôncio
3.
J Environ Manage ; 258: 110000, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31929048

RESUMO

Bioflocculant has been recently exploited in various research activities. In this research, we report for the first time that a novel bioflocculant can self-assemble into nanoparticles with an irregular structure in solution. Bioflocculant has been developed from novel consortium encompassing Enterococcus faecalis, Proteus mirabilis, Lysini bacillus sp., inoculated into the modified medium such as hydrolyzed wheat bran and rice bran extract. Characterization of bioflocculant shows that it is made up of mannose, fructose, raffinose, and galactose with a slightly negative charges. They are further characterized by FTIR and XPS. 3D-EEM and MALDITOF-MS are confirmed the proteoglycan nature of the bioflocculant. These bioflocculant not only exhibits greater biosorption of heavy metals by self-flocculating (or) self-aggregating activity, but also possesses mosquitocidal and anti-biofilm activity due to its cell surface modification. Further research have to be carried out regarding the mechanism of self-assembly nature of bioflocculant into nanoparticle in solution which provide a new path for bioremediation and biomedical application.


Assuntos
Bacillus , Metais Pesados , Biodegradação Ambiental , Floculação , Concentração de Íons de Hidrogênio , Consórcios Microbianos
4.
J Environ Manage ; 258: 110016, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31929058

RESUMO

The research was conducted to evaluate the sludge quality as fertilizer after heavy metal removal by using free nitrous acid (FNA, HNO2) solution. To meet up the Korean criteria of fertilizer, FNA treatment with the ultrasonic process was studied here. The sample was taken from a local wastewater and sewage treatment plants and FNA with FNA plus ultrasonic used to treat them. As and Cd concentrations were met the Korean criteria after FNA treatment. In contrast, Al of sludge from sewage treatment plant did not decrease down to the criteria, possibly suggesting that it may be related to the coagulants of the sludge during thickening and dewatering. FNA treatment showed satisfactory results in comparison with the other acidic treatment of citric acid, oxalic acid, HNO3 or HCl. Removal efficiency of the Fenton-like reaction was more effective than the FNA method. Despite this result, the FNA treatment may be better for sludge recycling as fertilizer because the Fenton-like process removed the necessary organic matter, nitrogen as well as metals. Moreover, the addition of ultrasound process has in conserving time and expenditure in metal removal and FNA with ultrasound became more effective in shorter reaction time. Therefore, FNA treated sludge could be a better option for sludge recycling as fertilizer. In conclusion, a proper plan of sludge management should be required for future work to use sludge as fertilizer.


Assuntos
Metais Pesados , Esgotos , Fertilizantes , Ácido Nitroso , Águas Residuárias
5.
Water Res ; 171: 115472, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31931379

RESUMO

Microbial extracellular polymeric substances (EPS) have gained increasing attention for various water treatment applications. In this study, EPS produced from nitrogen-limited glycerol/ethanol-rich wastewater were used to recover Cu2+ and Pb2+ from aqueous solutions. Continuous flow-through tests were conducted on a column packed with silica gel coated with polyethyleneimine, to which EPS were irreversibly attached as shown by optical reflectometry. These immobilised EPS excellently adsorbed Cu2+ and Pb2+, with 99.9% of influent metal adsorbed before the breakthrough points. Metal desorption was achieved with 0.1M HCl, with an average recovery of 86% for Cu2+ and 90% recovery for Pb2+. For the first time, we successfully showed the possibility to regenerate and reuse the immobilised EPS for five adsorption-desorption cycles (using Cu2+ as an example) with no reduction in the adsorbed amount at the breakthrough point (qbp). Based on the mass balance of the associated metal ions participating in the adsorption process, ion exchange was identified as the major mechanism responsible for Cu2+ and Pb2+ adsorption by EPS. The results demonstrate the potential of wastewater-produced EPS as an attractive and perhaps, cost-effective biosorbent for heavy metal removal (to trace effluent concentrations) and recovery (86-99%).


Assuntos
Metais Pesados , Poluentes Químicos da Água , Purificação da Água , Adsorção , Concentração de Íons de Hidrogênio , Polímeros
6.
J Environ Manage ; 256: 109953, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31989980

RESUMO

The study evaluated plants with phytoremediation potential that occur spontaneously in an area of copper mining tailings in Southern of Brazil. Eleven plant species were investigated for heavy metal concentrations in its biomass. All species showed copper concentrations greater than 100 mg kg-1, and seven species highlighted for copper concentrations between 321 and 586 mg kg-1 and these species showed Cr concentrations between 25 and 440 mg kg-1. The species S. viarum Dunal and B. trimera Less were highlighted showing the highest concentrations of Cr (586 mg kg-1) and Cu (440 mg kg-1), respectively. Seven species showed Pb phytoextraction potential and four species showed Cu phytostabilization potential. It was concluded that the investigated species are adapted to low nutritional conditions and showed tolerance to heavy metals, mainly Cu, Pb and Cr in its biomass.


Assuntos
Metais Pesados , Poluentes do Solo , Biodegradação Ambiental , Brasil , Cobre , Mineração , Raízes de Plantas
7.
Chemosphere ; 242: 125281, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896191

RESUMO

In this study, the potential of pulverized waste tires (PWTs), either on their own or mixed with soil (well graded sand), to act as adsorptive fill materials was evaluated by conducting laboratory tests for accessing their adsorption and geotechnical properties. PWT (0, 5, 10, 15, 25, and 100 wt%) was mixed with soil to evaluate the removal of benzene, toluene, ethylbenzene, and xylene (BTEX) components and two heavy metal ions (Pb2+ and Cu2+). Adsorption batch tests were performed to determine the equilibrium sorption capacity of each mixture. Subsequently, compaction, direct shear, and consolidation tests were performed to establish their geotechnical properties. The results showed that BTEX had the strongest affinity based on the uptake capacity by the soil-PWT mixtures. The adsorption of BTEX increased for greater PWT content, with pure PWT having the highest adsorption capacity toward BTEX removal: uptake capacities for xylene, ethylbenzene, toluene, and benzene were 526, 377, 207 and 127 µg/g sorbent, respectively. Heavy metal removal was increased by increasing the amount of PWT up to 10 wt%, and then decreased beyond this ratio. Compacted soil-PWT mixtures comprising 5-25 wt% PWT have relatively low dry unit weight, low compressibility, adequate shear capacity for many load-bearing field applications, and satisfactory adsorption of organic/inorganic contaminants, such that they could also be used as adsorptive fill materials.


Assuntos
Derivados de Benzeno/análise , Metais Pesados/análise , Poluentes do Solo/análise , Resíduos Sólidos/análise , Adsorção , Benzeno/análise , Modelos Teóricos , Eliminação de Resíduos , República da Coreia , Solo/química , Tolueno/análise , Xilenos/análise
8.
Chemosphere ; 242: 125266, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896197

RESUMO

Determining the reliable source contribution and spatial distribution of potentially toxic elements (PTEs) is a focal issue for soil regulation and remediation. For this purpose, three receptor models, US-EPA positive matrix factorization (EPAPMF), weighted alternating least squares positive matrix factorization (WALSPMF), and non-negative constrained absolutely principle analysis (NCAPCA), were used to a dataset consisting of ten PTEs (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) for source apportionment. Hazardous areas of ten PTEs were delineated using sequential indicator simulation (SIS) and uncertainty analysis. Three factors for ten PTEs were derived by three receptor models with a one-to-one correspondence between the factors. To obtain more appropriate results, the three receptor models were combined to calculate the ensemble-average source contributions. As, Co, Cr, Cu, Mn, and Ni were derived from a natural source with ensemble-average contributions higher than 85.72%. Cd, Hg, Pb, and Zn were contributed by both parent material and anthropogenic influence. More than half of Hg concentrations were associated with atmospheric deposition caused by human emissions. The concentrations of 28.04% for Cd, 20.74% for Hg, 43.49% for Pb, and 23.71% for Zn were associated with human inputs including agriculture practice, industrial activities, and vehicle emissions. The maps of spatial distribution generated by the SIS indicated that parent materials controlled the spatial distributions of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn. 27.1% and 32.1% of the total area for Cd and Hg were identified as hazardous areas exceeding 1.5 times background values of Shandong province.


Assuntos
Monitoramento Ambiental/métodos , Metais Pesados/análise , Modelos Teóricos , Poluentes do Solo/análise , Solo/química , Agricultura , China , Humanos , Indústrias , Emissões de Veículos/análise
9.
Bioresour Technol ; 302: 122797, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31981810

RESUMO

In this study, two bacteria strains (Enterobacter sp. SL and Acinetobacter sp. SL-1) and waste molasses (carbon source) were used to remove Zn(II), Cd(II), Cr(VI), and Cr(Total) in the liquid solution (87 mg·L). The results showed the removal efficiencies of Cr(Total) and Cr(VI) could reach over 98.00% after reaction, and the removal efficiencies of Zn(II) and Cd(II) were all about 90.00% by the synergistic actions of microorganisms and waste molasses. In this process, waste molasses provides nutrients for microorganisms and has the characteristics and capability of Cr, Zn, and Cd. Microorganisms mainly use biological adsorption (36.95% and 45.69%) and metabolism (24.37% and 17.05% by producing humic-acid and fulvic-acid like substances) to remove Zn(II) and Cd(II), while waste molasses could to remove Cr(Total) (81.24%) and Cr(VI) (75.90%). This study has potential application value for the treatment of wastewater containing high concentrations of heavy metals.


Assuntos
Metais Pesados , Poluentes Químicos da Água , Adsorção , Substâncias Húmicas , Melaço , Eliminação de Resíduos Líquidos , Águas Residuárias
10.
Waste Manag ; 104: 213-219, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31982784

RESUMO

Incineration bottom ash (IBA) of municipal solid waste is a potential construction material for civil engineering. However, the possible leaching of trace heavy metals from IBA is a concern. Water washing is a simple and economic method to remove heavy metals from IBA. In order to optimize the water washing process of IBA, this study investigated the pH evolution during washing and its effect on the removal of several heavy metals, including lead (Pb), zinc (Zn), nickel (Ni), cadmium (Cd), copper (Cu), and chromium (Cr), through a small-scale laboratory experiment. The results show that the pH of washing water increases quickly in the first 1-3 h mainly due to the dissolution of quicklime and portlandite, and then decreases with the increasing of washing time might be due to consumption of OH- by precipitation of metal hydroxides. The concentrations of Pb, Zn, and Ni in the washing water show a similar trend as that of the pH with time, whilst the concentrations of Cd, Cu, and Cr increase with the increase of washing time. Hence, the optimum washing time should be determined accordingly based on the most concerned metal(s), as well as the pH evaluation during washing.


Assuntos
Incineração , Metais Pesados , Cinza de Carvão , Concentração de Íons de Hidrogênio , Água
11.
Chemosphere ; 242: 125113, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896177

RESUMO

Health risk associated with drinking water has attracted increasing attention worldwide. Here, we conducted a survey on the main drinking water sources of Dalian in China to clarify the local human health risk associated with heavy metal and pesticide contaminants in the drinking water sources. The results showed that six heavy metals, namely, copper (Cu), zinc (Zn), cadmium (Cd), nickel (Ni), arsenic (As), and mercury (Hg), and two pesticides (atrazine and acetochlor) were detected in water samples, where the highest concentration of Hg (0.0621 µg L-1) exceeded the domestic standard only. In addition to the above-mentioned metals, Cr was also detected in the sediment/soil samples. As to the pesticides, atrazine, acetochlor, hexachlorobenzene, p,p'-DDE, and p,p'-DDD were detected in the sediment/soil samples at ng g-1 levels, and atrazine and acetochlor were found in water samples at ng L-1 levels. The human health risk assessment showed no marked difference in carcinogenic and noncarcinogenic risks from drinking water. Our study approved that hexachlorobenzene and arsenic were the main contributors to human carcinogenic risks, which were calculated at the level of 10-4. Furthermore, sediment and soil ingestion was considered as the major source of human health risk in our study area. This study revealed the current pollution status in the surrounding area of the drinking water source and the main source associated with human health risk, which established a sound basis for further decision-making to take necessary action on pollution control.


Assuntos
Água Potável/química , Exposição Ambiental/estatística & dados numéricos , Poluição Ambiental/estatística & dados numéricos , Metais Pesados/análise , Praguicidas/análise , Arsênico , Cádmio , China , Cobre/análise , Monitoramento Ambiental/métodos , Poluição Ambiental/análise , Humanos , Mercúrio/análise , Compostos Orgânicos , Medição de Risco , Solo , Poluentes do Solo/análise
12.
Environ Monit Assess ; 192(2): 83, 2020 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-31900674

RESUMO

In ecological risk assessment, sum-of-toxic-unit approaches based on measured water quality factors such as trace metals are used to infer ecological impacts in the environment. However, it is uncertain whether the use of such approaches yields accurate risk predictions. To address this issue, we investigated and compared (1) water quality, including trace metals, and (2) benthic macroinvertebrate communities in a northern Japanese river receiving treated discharge from an abandoned mine and in a nearby reference river. As a sum-of-toxic-unit approach, we employed a cumulative criterion unit (CCU), namely, the sum of the ratios of the dissolved concentrations of a metal (Cu, Zn, Cd, or Pb) divided by the US Environmental Protection Agency hardness-adjusted environmental water quality criterion for that metal. Compared with the reference sites, at the metal-contaminated sites, the richness, abundance, and structure of macroinvertebrate communities were little affected, with CCUs of 1.7 to 7.4, suggesting that CCU values exceeding 1 do not always indicate marked adverse impacts on these metrics. Further study is still required to derive a more compelling conclusion on the generally applicable relationships between CCUs and ecological impacts on river invertebrates. This would lead to better ecological risk assessments based on sum-of-toxic-unit approaches.


Assuntos
Biodiversidade , Monitoramento Ambiental , Invertebrados , Poluentes Químicos da Água/análise , Animais , Ecologia , Japão , Metais/toxicidade , Metais Pesados/análise , Rios/química , Qualidade da Água
13.
Environ Monit Assess ; 192(2): 91, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31902022

RESUMO

The concentration of heavy metals in the natural waters of the area surrounding Dereli (Giresun), a mineralized area, was determined. In addition, the physicochemical parameters (such as pH, Eh, and HCO3-) influencing the concentration of dissolved metals in waters were evaluated. Samples were collected from stream, spring, and main river waters, some of which are used by local residents for drinking, fish farming, and animal husbandry. The present data indicate that the water-rock interaction is the main process controlling the chemical composition of waters in the area. The waters are predominantly CaMgHCO3-type waters with alkaline pH values. Heavy metal concentrations (Pb, Zn, Cu, Fe, Mn, U, Cd, As, Hg, Sb, Ni, Co, and Ba) in waters were generally low. Relatively high values of certain metals were determined in waters of the Kotana and Kurtulmus sites of Dereli. The levels of Pb in the river, stream, and spring water samples in these sites were somewhat higher than the Pb values reported in the literature for natural waters. However, these values only slightly exceeded the Pb water limit values proposed by the USEPA and the WHO. In addition, the concentrations of other heavy metals, except Pb, were fairly similar to those of other natural waters and these values were also under the drinking water limits set by the WHO and the USEPA. This study shows that waters in the area of Dereli were not significantly affected by mineralization. This is most likely caused by the bicarbonate-rich waters affecting the dissolved metal concentrations.


Assuntos
Monitoramento Ambiental , Poluentes Químicos da Água/análise , Animais , Água Doce/química , Metais Pesados/análise , Minerais , Rios/química , Turquia
14.
Waste Manag ; 104: 51-59, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31962217

RESUMO

The generation of landfill leachate nanofiltration concentrate (LLNC) has been a dilemma for leachate treatment plants because it contains large amounts of refractory organics with low molecular weight (LMWO), as well as heavy metals (HMs), and is difficult to handle. The coagulation removal of LMWOs is a significant challenge, as is the removal of HMs bonded to LMWOs. In this study, coagulation through the dosing of FeCl3 was used to remove LMWOs and HMs from LLNC. The results interestingly demonstrated that the removal rates of dissolved organic carbon (DOC), Cr, Ni, and As reached up to 84.1% ± 3.9%, 91.0 ± 1.1%, 73.1 ± 2.2%, and 96.9 ± 1.5%, respectively. The partition of LMWO components, as well as the interactions among the LMWOs, HMs, and Fe(III) were investigated to determine the mechanism behind the LMWO and HM removal. LMWOs with a high degree of humification, including humic and fulvic acid-like components, were preferentially removed through aggregation and electrostatic attraction originating from the specialistic adsorption of Fe2(OH)24+ and Fe3(OH)45+. In addition to being removed, a portion of these two components was dissociated into aromatic protein I, aromatic protein II, and soluble microbial by-product-like materials due to an acid effect and the formation of inner-sphere complexes. A redundancy analysis revealed that As, Cr, and Ni are mainly removed through the electrostatic attraction of Fe(III), bonding to humic substances and hydrophilic organics, respectively. The outcomes provide a new understanding on the coagulation removal of LMWOs and HMs.


Assuntos
Metais Pesados , Poluentes Químicos da Água , Compostos Férricos , Substâncias Húmicas , Peso Molecular
15.
Environ Technol ; 41(4): 498-510, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30028646

RESUMO

The possibility of a landfill leachate pre-treatment, aiming at heavy metals removal, by means of either zero valent iron (ZVI), or granular activated carbon (GAC) or by a mixture of the two materials, was investigated in this paper through batch and column tests. For this purpose, a synthetic landfill leachate containing heavy metals (i.e. Cu, Ni, Zn), chloride, sulphates, ammonium and organic matter was prepared. Batch tests results demonstrated the efficiency of ZVI, GAC and ZVI/GAC mixture in heavy metals removal (efficiency > 90%) and their negligible effect on the other contaminants. Column tests showed as pure ZVI is by far more efficient than pure GAC in the long term. The influence of humic acids (HA) on the reactive and hydraulic behaviour of ZVI was also studied through column tests. The presence of HA in the leachate caused a reduction of ZVI removal efficiency and a considerable decrease in its hydraulic conductivity. Results of a column test carried out using the ZVI/GAC granular mixture showed as the removal efficiency over time ranges from 100% to 89% for Cu, from 93% to 80% for Ni and from 98% to 95% for Zn. The use of a filter filled with the ZVI/GAC mixture could find application for leachate pre-treatment having the objective of removing heavy metals prior the final co-treatment with municipal wastewater minimizing adverse side effect on the process (e.g. transfer of heavy metals in the excess sludge to be used in agriculture).


Assuntos
Metais Pesados , Poluentes Químicos da Água , Carvão Vegetal , Substâncias Húmicas , Ferro
16.
Waste Manag ; 102: 645-654, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31785524

RESUMO

Incineration of sludge in waste incinerators is a trend of sludge disposal, and the problem of heavy metal in horizontal flue ash is a concern. Horizontal flue ash in waste incinerator was collected before and after the sludge was co-combusted. XRF, SEM-DES, and ICP were used to characterize the effect of sludge on the distribution of heavy metals on different heated surfaces. Potential ecological risk index of all horizontal flue ash was higher than 600, indicating the high ecological risk. After adding sludge for co-combustion, heavy metals content in all ash sample increased. As for chemical speciation of heavy metals, the addition of sludge increased the content of mild acid-soluble fraction, reducible fraction and oxidizable fraction of heavy metals, while decreased that of the residual fraction. Environmental pollution and potential ecological risks of heavy metals were increased when sludge was co-combusted. The fitting relation between the heavy metals content of each speciation and the gas temperature and the sludge mixing amount was given, which could be used to predict the heavy metal content in horizontal flue ash.


Assuntos
Incineração , Metais Pesados , Carbono , Cinza de Carvão , Esgotos
17.
Waste Manag Res ; 38(2): 122-133, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31793381

RESUMO

Agglomeration that occurs during municipal sewage sludge (MSS) fluidized bed co-combustion might affect heavy metal distribution and the transformation of bottom ash. A study on the mobility and speciation of heavy metals that accompanies agglomeration behavior and phosphorus addition should be examined during MSS co-combustion. Meanwhile, the aim of this study was to evaluate the total content and speciation of heavy metals during the MSS fluidized bed co-combustion by the chemical sequential extraction procedure (SEP). The risk assessment code (RAC) and individual contamination factor (ICF) are calculated to evaluate the mobility of heavy metals and their environmental risks in agglomerates. Moreover, identification of agglomerates is established by both characterization (scanning electron microscopy/energy-dispersive spectroscopy, X-ray photoelectron spectroscopy) and thermodynamic simulation (HSC chemistry software). The experimental results indicated that P and Na would form the lower melting-point compounds such as NaPO3 and Na2O in the bottom ash, which promoted agglomeration during MSS fluidized bed co-combustion. According to the simulation, Na and P have a stronger affinity than Si and Cr, and this reaction is not only influenced by particle agglomeration, but also by heavy metal distribution during modified MSS co-combustion. Nevertheless, the results of ICFs and RACs obtained from the SEP indicated that for heavy metals trapped in agglomerates, a weaker binding such as physical covering by eutectics might be considered as the dominant reaction compared with chemical binding to form a metal complex.


Assuntos
Cinza de Carvão , Metais Pesados , Incineração , Fósforo , Esgotos
18.
Waste Manag ; 102: 698-709, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31794929

RESUMO

This study assesses the volatility of 15 elements (As, Bi, C, Cd, Cl, Cu, K, Mn, Na, P, Pb, S, Sb, Sn, and Zn) during thermal processing of fly ashes obtained from four waste-to-energy plants and one wood-combustion plant. Differences in volatility in oxidising and reducing atmospheres (air and 10% H2/90% N2) were assessed at two temperatures, 700 and 1000 °C. P and Mn were predominately retained in all ashes regardless of the operating atmosphere and temperature. Other elements showed significant variation in volatility depending on the type of fly ash, atmosphere, and temperature. Heat-treatment of the wood-combustion fly ash in the air atmosphere resulted in low release of K, Na, and all investigated heavy metals and metalloids. Several valuable elements, including Zn, Sb, Sn, and Bi, were significantly more volatile in the reducing atmosphere than in the oxidising atmosphere, particularly at 1000 °C. Other elements were either less volatile, equally volatile, or only marginally more volatile when the ashes were heated at 1000 °C in the reducing atmosphere. These elements include C, Cl, Cu, and, in the case of fly ashes derived from municipal solid waste, Cd and Pb. A two-step process, in which municipal solid waste incineration fly ash is first heated in an oxidising atmosphere and then in a reducing atmosphere, is proposed for production of a chloride-free zinc concentrate. Evaluation of the two-step process at 880 °C shows good potential for selective volatilisation of Zn with other valuable elements, including Sn, Sb, and Bi.


Assuntos
Metais Pesados , Oligoelementos , Cinza de Carvão , Incineração , Centrais Elétricas , Resíduos Sólidos , Volatilização , Madeira
19.
Bioresour Technol ; 298: 122421, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31767428

RESUMO

Coupling algae growth on wastewater with hydrothermal liquefaction (HTL) is regarded as an environment-enhancing pathway for wastewater management, biomass amplification, sustainable energy generation and value-added products generation. Through this integrated pathway, microalgae can not only recover nitrogen and phosphorus, but also absorb heavy metals from the wastewater. The migration and transformation of heavy metals need to be specifically assessed and considered due to the environmental concerns associated with metal toxicity. This work reviewed recent advances with respect to bioremediation mechanisms. Particular emphasis was placed on the heavy metal migration, transformation, and the key factors involved in algal wastewater treatment and biomass conversion. Additionally, the challenges of coupling algae wastewater treatment, hydrothermal conversion, and heavy metal control were addressed. Finally, a paradigm involving enhanced algal wastewater treatment and bioenergy production for field application was proposed.


Assuntos
Metais Pesados , Microalgas , Biocombustíveis , Biomassa , Águas Residuárias
20.
Waste Manag Res ; 38(2): 142-155, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31755825

RESUMO

The use of accelerated carbonation technology in combination with a granulation process was employed to produce aggregates from a variety of industrial wastes, which included municipal solid waste incineration fly ash and air pollution control residue, oil shale ash, cement kiln dust, and quarry fines that have been produced in Estonia. Focusing mainly on the effects produced by the content of municipal solid waste incineration ash in the admixtures, the granule compositions were varied in order to tailor granule properties on the basis of CO2 uptake, strength development, leaching behaviour, microstructure, and morphology. All the steps involved in the accelerated carbonation technology granulation process, from mixing with additives to granulation and carbonation treatment, were carried out in the same apparatus - an Eirich EL1 intensive mixer/granulator. The amount of CO2 that was bound ranged from 23 to 108 kg per tonne of waste. The granules that included the optimised mixture of municipal solid waste incineration air pollution control residue, oil shale ash, cement kiln dust, and ordinary Portland cement were characterised by the highest compressive strength (4.03 MPa) and water durability for the size range of 4-10 mm. In addition, the process was found to be effective in reducing alkalinity (pH < 11.5) and immobilising heavy metals (especially zinc) and chloride. The composition and properties of the respective waste materials and mechanisms associated with the characteristics of the resulting granules were also addressed.


Assuntos
Resíduos Industriais , Metais Pesados , Cinza de Carvão , Estônia , Incineração , Resíduos Sólidos
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