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1.
Environ Sci Technol ; 48(24): 14844-50, 2014 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-25402169

RESUMO

This study investigates, for the first time, the NOx, N2O, SO3, and Hg emissions from combustion of a Victorian brown coal in a 10 kWth fluidized bed unit under oxy-fuel combustion conditions. Compared to air combustion, lower NOx emissions and higher N2O formation were observed in the oxy-fuel atmosphere. These NOx reduction and N2O formations were further enhanced with steam in the combustion environment. The NOx concentration level in the flue gas was within the permissible limit in coal-fired power plants in Victoria. Therefore, an additional NOx removal system will not be required using this coal. In contrast, both SO3 and gaseous mercury concentrations were considerably higher under oxy-fuel combustion compared to that in the air combustion. Around 83% of total gaseous mercury released was Hg(0), with the rest emitted as Hg(2+). Therefore, to control harmful Hg(0), a mercury removal system may need to be considered to avoid corrosion in the boiler and CO2 separation units during the oxy-fuel fluidized-bed combustion using this coal.


Assuntos
Poluentes Atmosféricos/análise , Mercúrio/análise , Óxidos de Nitrogênio/análise , Óxidos de Enxofre/análise , Carvão Mineral , Centrais Elétricas , Vitória
2.
Sci Total Environ ; 924: 171453, 2024 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-38453089

RESUMO

Recycling e-waste is seen as a sustainable alternative to compensate for the limited natural rare earth elements (REEs) resources and the difficulty of accessing these resources. Recycling facilitates the recovery of valuable products and minimizes emissions during their transportation. Numerous studies have been reported on e-waste recycling using various techniques, including thermo-, hydro- and biometallurgical approaches. However, each approach still has technical, economic, social, or environmental limitations. This review highlights the potential of recycling e-waste, including outlining the current unutilized potential of REE recycling from different e-waste components. An in-depth analysis of e-waste generation on a global scale and Australian scenario, along with various hazardous impacts on ecosystem and human health, is reported. In addition, a comprehensive summary of various metal recovery processes and their merits and demerits is also presented. Lifecycle analysis for recovering REEs from e-waste indicate a positive environmental impact when compared to REEs produced from virgin sources. In addition, recovering REEs form secondary sources eliminated ca. 1.5 times radioactive waste, as seen in production from primary sources scenario. The review outcome demonstrates the increasing potential of REE recycling to overcome critical challenges, including issues over supply security and localized dependency.

3.
Virus Res ; 341: 199331, 2024 03.
Artigo em Inglês | MEDLINE | ID: mdl-38280436

RESUMO

Dengue virus infection in humans ranges from asymptomatic infection to severe infection, with ∼2.5 % overall disease fatality rate. Evidence of neurological manifestations is seen in the severe form of the disease, which might be due to the direct invasion of the viruses into the CNS system but is poorly understood. In this study, we demonstrated that the aged AG129 mice are highly susceptible to dengue serotypes 1-4, and following the adaptation, this resulted in the generation of neurovirulent strains that showed enhanced replication, aggravated disease severity, increased neuropathogenesis, and high lethality in both adult and aged AG129 mice. The infected mice had endothelial dysfunction, elicited pro-inflammatory cytokine responses, and exhibited 100 % mortality. Further analysis revealed that aged-adapted DENV strains induced measurable alterations in TLR expression in the aged mice as compared to the adult mice. In addition, metabolomics analysis of the serum samples from the infected adult mice revealed dysregulation of 18 metabolites and upregulation of 6-keto-prostaglandin F1 alpha, phosphocreatine, and taurocholic acid. These metabolites may serve as key biomarkers to decipher and comprehend the severity of dengue-associated severe neuro-pathogenesis.


Assuntos
Vírus da Dengue , Dengue , Humanos , Animais , Camundongos , Idoso , Vírus da Dengue/fisiologia , Citocinas/metabolismo , Modelos Animais de Doenças
4.
Sci Total Environ ; 913: 169436, 2024 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-38160846

RESUMO

Due to the 'forever' degrading nature of plastic waste, plastic waste management is often complicated. The applications of plastic are ubiquitous and inevitable in many scenarios. Current global waste plastics production is ca. 3.5 MMT per year, and with the current trend, plastic waste production will reach 25,000 MMT by 2040. However, the rapid growth in plastic manufacture and the material's inherent nature resulted in the accumulation of a vast amount of plastic garbage. The current recycling rate is <10 %, while the large volumes of discarded plastic waste cause environmental and ecological problems. Recycling rates for plastic vary widely by region and type of plastic. In some developed countries, the recycling rate for plastics is around 20-30 %, while in many developing nations, it is much lower. These statistics highlight the magnitude of the plastic waste problem and the urgent need for comprehensive strategies to manage plastic waste more effectively and reduce its impact on the environment. This review critically analyses past studies on the essential and efficient techniques for turning plastic trash into treasure. Additionally, an attempt has been made to provide a comprehensive understanding of the plastic upcycling process, the 3Rs policy, and the life-cycle assessment (LCA) of plastic conversion. The review advocates pyrolysis as one of the most promising methods of turning plastic trash into valuable chemicals. In addition, plastic waste management can be severely impacted due to uncontrollable events, such as Covid 19 pandemic. Recycling and chemical upcycling can certainly bring value to the end-of-life plastic. However, the LCA analysis indicated there is still a huge scope for innovation in chemical upcycling area compared to mechanical recycling. The formulation of policies and heightened public participation could play a pivotal role in reducing the environmental repercussions of plastic waste and facilitating a shift towards a more sustainable future.

5.
Environ Sci Technol ; 47(3): 1729-34, 2013 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-23301852

RESUMO

Sulfur emission from a Victorian brown coal was quantitatively determined through controlled experiments in a continuously fed drop-tube furnace under three different atmospheres: pyrolysis, oxy-fuel combustion, and carbon dioxide gasification conditions. The species measured were H(2)S, SO(2), COS, CS(2), and more importantly SO(3). The temperature (873-1273 K) and gas environment effects on the sulfur species emission were investigated. The effect of residence time on the emission of those species was also assessed under oxy-fuel condition. The emission of the sulfur species depended on the reaction environment. H(2)S, SO(2), and CS(2) are the major species during pyrolysis, oxy-fuel, and gasification. Up to 10% of coal sulfur was found to be converted to SO(3) under oxy-fuel combustion, whereas SO(3) was undetectable during pyrolysis and gasification. The trend of the experimental results was qualitatively matched by thermodynamic predictions. The residence time had little effect on the release of those species. The release of sulfur oxides, in particular both SO(2) and SO(3), is considerably high during oxy-fuel combustion even though the sulfur content in Morwell coal is only 0.80%. Therefore, for Morwell coal utilization during oxy-fuel combustion, additional sulfur removal, or polishing systems will be required in order to avoid corrosion in the boiler and in the CO(2) separation units of the CO(2) capture systems.


Assuntos
Poluentes Atmosféricos/análise , Carvão Mineral/análise , Gases/química , Temperatura Alta , Enxofre/análise , Sulfeto de Hidrogênio/análise , Dióxido de Enxofre/análise , Óxidos de Enxofre/análise
6.
JSLS ; 17(2): 330-2, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23925031

RESUMO

INTRODUCTION: Endoclip migration into the common bile duct after laparoscopic cholecystectomy is a rare complication. Very few cases have been reported in the literature, mostly in the form of case reports. CASE DESCRIPTION: We report a case of Endoclip migration into the bile duct with stone formation 6 y after laparoscopic cholecystectomy. The patient presented with recurrent abdominal pain and intermittent jaundice for 6 mo. Diagnosis was suspected when a computed tomography scan of the abdomen showed a metallic density artifact in the lower end of the bile duct. The diagnosis was confirmed by endoscopic retrograde cholangiopancreatography. The patient was successfully managed by endoscopic stone and clip removal. DISCUSSION: Endoclip migration with biliary complications should be considered in the differential diagnosis of postcholecystectomy problems. The clinical manifestations and management are similar to that of noniatrogenic choledocholithiasis.


Assuntos
Colecistectomia Laparoscópica/efeitos adversos , Ducto Colédoco , Migração de Corpo Estranho/diagnóstico por imagem , Instrumentos Cirúrgicos , Dor Abdominal/etiologia , Ductos Biliares/patologia , Colangiopancreatografia Retrógrada Endoscópica , Colecistectomia Laparoscópica/instrumentação , Dilatação Patológica , Migração de Corpo Estranho/complicações , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X
7.
Polymers (Basel) ; 15(17)2023 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-37688277

RESUMO

This article reports the characterisation of pyrolysis of automotive shredder residue using in situ synchrotron IR, gas-phase IR, and thermal analyses to explore if the automotive shredder residue can be converted into value-added products. When heating to ~600 °C at different heating rates, thermal analyses suggested one- to two-stage pyrolysis. Transformations in the first stage, at lower temperatures, were attributed to the degradation of carbonyl, hydroxyl, or carboxyl functional stabilisers (aldehyde and ether impurities, additives, and stabilisers in the ASR). The second stage transformations, at higher temperatures, were attributed to the thermal degradation of the polymer char. Simultaneous thermal analyses and gas-phase IR spectroscopy confirmed the evolution of the gases (alkanes (CH4), CO2, and moisture). The synchrotron IR data have demonstrated that a high heating rate (such as 150 °C/min) results in an incomplete conversion of ASRs unless sufficient time is provided. The thermogravimetry data fit the linearised multistage kinetic model at different heating rates. The activation energy of reactions varied between 24.98 and 124.94 kJ/mol, indicating a surface-controlled reaction exhibiting high activation energy during the initial stages and a diffusion and mass transfer control showing lower activation energy at the final stages. The corresponding frequency factors were in the range of 3.34 × 1013-5.68 × 101 mg-1/min for different pyrolysis stages. The evolution of the functional groups decreased with an increase in the heating rate.

8.
Bioresour Technol ; 364: 128087, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36216287

RESUMO

Biomass pyrolysis has recently gained increasing attention as a thermochemical conversion process for obtaining value-added products, thanks to the development of cutting-edge, innovative and cost-effective pyrolysis processes. Over time, new and novel pyrolysis techniques have emerged, and these processes can be tuned to maximize the production of high-quality hydrogen. This review examines recent advancements in biomass pyrolysis by classifying them into conventional, advanced and emerging approaches. A comprehensive overview on the recent advancements in biomass pyrolysis, highlighting the current status for industrial applications is presented. Further, the impact of each technique under different approaches on conversion of biomass for hydrogen production is evaluated. Techniques, such as inline catalytic pyrolysis, microwave pyrolysis, etc., can be employed for the sustainable production of hydrogen. Finally, the techno-economic analysis is presented to understand the viability of pyrolysis at large scale. The outlook highlights discernments into future directions, aimed to overcome the current shortcomings.

9.
Lancet Infect Dis ; 22(4): 473-482, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-34838183

RESUMO

BACKGROUND: SARS-CoV-2 variants of concern (VOCs) have threatened COVID-19 vaccine effectiveness. We aimed to assess the effectiveness of the ChAdOx1 nCoV-19 vaccine, predominantly against the delta (B.1.617.2) variant, in addition to the cellular immune response to vaccination. METHODS: We did a test-negative, case-control study at two medical research centres in Faridabad, India. All individuals who had a positive RT-PCR test for SARS-CoV-2 infection between April 1, 2021, and May 31, 2021, were included as cases and individuals who had a negative RT-PCR test were included as controls after matching with cases on calendar week of RT-PCR test. The primary outcome was effectiveness of complete vaccination with the ChAdOx1 nCoV-19 vaccine against laboratory-confirmed SARS-CoV-2 infection. The secondary outcomes were effectiveness of a single dose against SARS-CoV-2 infection and effectiveness of a single dose and complete vaccination against moderate-to-severe disease among infected individuals. Additionally, we tested in-vitro live-virus neutralisation and T-cell immune responses to the spike protein of the wild-type SARS-CoV-2 and VOCs among healthy (anti-nucleocapsid antibody negative) recipients of the ChAdOx1 nCoV-19 vaccine. FINDINGS: Of 2379 cases of confirmed SARS-CoV-2 infection, 85 (3·6%) were fully vaccinated compared with 168 (8·5%) of 1981 controls (adjusted OR [aOR] 0·37 [95% CI 0·28-0·48]), giving a vaccine effectiveness against SARS-CoV-2 infection of 63·1% (95% CI 51·5-72·1). 157 (6·4%) of 2451 of cases and 181 (9·1%) of 1994) controls had received a single dose of the ChAdOx1 nCoV-19 vaccine (aOR 0·54 [95% CI 0·42-0·68]), thus vaccine effectiveness of a single dose against SARS-CoV-2 infection was 46·2% (95% CI 31·6-57·7). One of 84 cases with moderate-to-severe COVID-19 was fully vaccinated compared with 84 of 2295 cases with mild COVID-19 (aOR 0·19 [95% CI 0·01-0·90]), giving a vaccine effectiveness of complete vaccination against moderate-to-severe disease of 81·5% (95% CI 9·9-99·0). The effectiveness of a single dose against moderate-to-severe disease was 79·2% (95% CI 46·1-94·0); four of 87 individuals with moderate-to-severe COVID-19 had received a single dose compared with 153 of 2364 participants with mild disease (aOR 0·20 [95% CI 0·06-0·54]). Among 49 healthy, fully vaccinated individuals, neutralising antibody responses were lower against the alpha (B.1.1.7; geometric mean titre 244·7 [95% CI 151·8-394·4]), beta (B.1.351; 97·6 [61·2-155·8]), kappa (B.1.617.1; 112·8 [72·7-175·0]), and delta (88·4 [61·2-127·8]) variants than against wild-type SARS-CoV-2 (599·4 [376·9-953·2]). However, the antigen-specific CD4 and CD8 T-cell responses were conserved against both the delta variant and wild-type SARS-CoV-2. INTERPRETATION: The ChAdOx1 nCoV-19 vaccine remained effective against moderate-to-severe COVID-19, even during a surge that was dominated by the highly transmissible delta variant of SARS-CoV-2. Spike-specific T-cell responses were maintained against the delta variant. Such cellular immune protection might compensate for waning humoral immunity. FUNDING: Department of Biotechnology India, Council of Scientific and Industrial Research India, and Fondation Botnar.


Assuntos
COVID-19 , SARS-CoV-2 , Formação de Anticorpos , COVID-19/epidemiologia , COVID-19/prevenção & controle , Vacinas contra COVID-19 , Estudos de Casos e Controles , ChAdOx1 nCoV-19 , Humanos , Vacinação
10.
Sci Rep ; 11(1): 11183, 2021 05 27.
Artigo em Inglês | MEDLINE | ID: mdl-34045559

RESUMO

Lignocellulosic biomass is an attractive renewable resource to produce biofuel or platform chemicals. Efficient and cost-effective conversion systems of lignocellulosic biomass depend on their appropriate pretreatment processes. Alkali or dilute acid pretreatment of biomass requires a high temperature (> 150 °C) to remove xylan (hemicellulosic sugar) and lignin partially. In this study, peracetic acid was used to pretreat biomass feedstocks, including hardwood and softwood species. It was found that the thermally-assisted dilute acid pretreatment of biomass conducted under the mild temperature of 90 °C up to 5 h resulted in the effective removal of lignin from the biomass with a negligible loss of carbohydrates. This thermally-assisted pretreatment achieved 90% of delignification, and this result was compared with the microwave-assisted pretreatment method. In addition, the crystallinity index (CrI), surface morphology, and chemical structure were significantly changed after the acid pretreatment. The biomass digestibility increased significantly with increased reaction time, by 32% and 23% for hardwood and softwood, respectively. From this study, it is clear that peracetic acid pretreatment is an effective method to enrich glucan content in biomass by delignification.

11.
Microbiol Spectr ; 9(3): e0110821, 2021 12 22.
Artigo em Inglês | MEDLINE | ID: mdl-34878310

RESUMO

Equitable and timely access to COVID-19-related care has emerged as a major challenge, especially in developing and low-income countries. In India, ∼65% of the population lives in villages where infrastructural constraints limit the access to molecular diagnostics of COVID-19 infection. Especially, the requirement of a cold chain transport for sustained sample integrity and associated biosafety challenges pose major bottlenecks to the equitable access. Here, we developed an innovative clinical specimen collection medium, named SupraSens microbial transport medium (SSTM). SSTM allowed a cold chain-independent transport at a wide temperature range (15°C to 40°C) and directly inactivated SARS-CoV-2 (<15 min). Evaluation of SSTM compared to commercial viral transport medium (VTM) in field studies (n = 181 patients) highlighted that, for the samples from same patients, SSTM could capture more symptomatic (∼26.67%, 4/15) and asymptomatic (52.63%, 10/19) COVID-19 patients. Compared to VTM, SSTM yielded significantly lower quantitative PCR (qPCR) threshold cycle (Ct) values (mean ΔCt > -3.50), thereby improving diagnostic sensitivity of SSTM (18.79% [34/181]) versus that of VTM (11.05% [20/181]). Overall, SSTM had detection of COVID-19 patients 70% higher than that of VTM. Since the logistical and infrastructural constraints are not unique to India, our study highlights the invaluable global utility of SSTM as a key to accurately identify those infected and control COVID-19 transmission. Taken together, our data provide a strong justification to the adoption of SSTM for sample collection and transport during the pandemic. IMPORTANCE Approximately forty-four percent of the global population lives in villages, including 59% in Africa (https://unhabitat.org/World%20Cities%20Report%202020). The fast-evolving nature of SARS-CoV-2 and its extremely contagious nature warrant early and accurate COVID-19 diagnostics across rural and urban population as a key to prevent viral transmission. Unfortunately, lack of adequate infrastructure, including the availability of biosafety-compliant facilities and an end-to-end cold chain availability for COVID-19 molecular diagnosis, limits the accessibility of testing in these countries. Here, we fulfill this urgent unmet need by developing a sample collection and transport medium, SSTM, that does not require cold chain, neutralizes the virus quickly, and maintains the sample integrity at broad temperature range without compromising sensitivity. Further, we observed that use of SSTM in field studies during pandemic improved the diagnostic sensitivity, thereby establishing the feasibility of molecular testing even in the infrastructural constraints of remote, hilly, or rural communities in India and elsewhere.


Assuntos
COVID-19/diagnóstico , SARS-CoV-2/isolamento & purificação , Manejo de Espécimes/métodos , COVID-19/virologia , Teste para COVID-19 , Contenção de Riscos Biológicos , Meios de Cultura/química , Meios de Cultura/metabolismo , Humanos , Técnicas de Diagnóstico Molecular , Reação em Cadeia da Polimerase em Tempo Real , SARS-CoV-2/genética , SARS-CoV-2/metabolismo , Manejo de Espécimes/instrumentação
12.
Waste Manag ; 117: 179-187, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32861080

RESUMO

Steel slags are generally alkaline with a high calcium content and are viewed as a potential feedstock for carbon dioxide sequestration and utilization, mostly through aqueous mineral carbonation routes. For recovery of multiple metals such as Ca, Fe, Mg, and Si, and generation of value-added products by dissolution and precipitation reactions in aqueous media, enhancing the metal selectivity and extraction efficiency are important. However, there is limited understanding of independent parameters that influence these important characteristics. In this work, a systematic attempt was made to correlate these key dissolution characteristics of basic oxygen furnace slag in acidic media with its mineralogical and physical characteristics, the changes in aqueous chemistry, and the role of potential secondary precipitates. The findings from this study substantiate that steel slag is a potential feedstock because of the calcium being mainly present as orthosilicates, which were found to leach congruently without forming a leached layer that might hinder calcium extraction. The leaching of Fe(II) from the slag is the main source of impurity and its slow oxidation-precipitation leads to a pH plateau at the end of the dissolution step. Oxidation-precipitation of Fe(II) is controlled by hydroxyl concentration in the aqueous solution, which necessitates a pH-swing step by addition of a base after dissolution. Use of surface complexing agents, such as sodium molybdate, can significantly reduce iron impurity in the leachate and obtain an iron-rich slag residue for recycle to iron and steel industry.


Assuntos
Resíduos Industriais/análise , Aço , Dióxido de Carbono , Metais , Solubilidade
13.
J Biomol Struct Dyn ; 38(6): 1612-1625, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31057089

RESUMO

Inhibition of the viral RNA-dependent RNA polymerase (RdRp) to resolve chronic infection is a useful therapeutic strategy against Hepatitis C virus (HCV). Non-nucleoside inhibitors (NNIs) of RdRp are small molecules that bind tightly with allosteric sites on the enzyme, thereby inhibiting polymerase activity. A large number of crystal structures (176) were studied to establish the structure-activity relationship along with the mechanism of inhibition and resistance between HCV RdRp and NNIs at different allosteric sites. The structure and the associated dynamics are the blueprint to understand the function of the protein. We have implemented the ligand-based pharmacophore and molecular dynamic simulations to extract the possible local and global characteristics of RdRp upon NNI binding and the structural-dynamical features possessed by the known actives. Our results suggest that the NNI binding induces significant fluctuations at the atomic level which are critical for enzymatic activity, with minimal global structural alterations. Residue-wise mapping of interactions of NNIs at different sites exhibited some conserved interaction patterns of key amino acids and water molecules. Here, the structural insights are explored to understand the correlation between the dynamics of protein's subdomains and function at the molecular level, useful for genotype-specific rational designing of NNIs.Communicated by Ramaswamy H. Sarma.


Assuntos
Inibidores Enzimáticos/química , Hepacivirus , RNA Polimerase Dependente de RNA/química , Proteínas não Estruturais Virais/química , Sítio Alostérico , Antivirais/química , Sítios de Ligação , Hepacivirus/enzimologia , Hepacivirus/genética
14.
Waste Manag ; 102: 139-148, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31677521

RESUMO

Catalytic pyrolysis is a useful technique for the conversion of scrap tyres into liquid fuels. Zeolite catalysts were employed in the pyrolysis of scrap tyres for the production of aromatic rich fuel. Deactivation of zeolite catalysts during pyrolysis reaction was investigated which played an important role in the product quality and composition. Herein, the performance of microporous zeolite catalysts and mesoporous MCM-41 catalyst was evaluated in a two-stage fixed bed reactor for the pyrolysis of scrap tyres. Comparative studies showed the increase in the production of aromatic compounds up to 23.7% over zeolite catalyst as compared to 18.7% over MCM-41 catalyst. However, Zeolite Y catalyst exhibited higher coke formation led to the rapid deactivation. The stability of zeolite catalysts is addressed by the incorporation of Cerium metal within the framework of two zeolite catalysts namely Zeolite Y and ZSM-5 through the ion-exchange technique. Parent and spent catalysts were characterised using synchrotron FT-IR spectroscopy, temperature-programmed desorption of ammonia (NH3-TPD), N2 Physisorption, scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), energy-dispersive X-ray spectroscopy (EDX), and hydrogen temperature-programmed reduction (H2-TPD). A higher percentage of aromatics were produced over the large pore Zeolite Y. Cerium ion-exchange decreased the formation of coke from 8.1% to 5.7% over submicron and large pore Zeolite Y catalyst. Moreover, naphthalene production decreased over both Ce-Zeolite Y and Ce-ZSM-5.


Assuntos
Cério , Coque , Zeolitas , Catálise , Pirólise , Espectroscopia de Infravermelho com Transformada de Fourier
15.
ACS Omega ; 4(5): 8747-8757, 2019 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-31459964

RESUMO

Thermo-catalytic conversion of cellulosic feedstock, such as lignocellulose, to platform chemicals offers a renewable alternative to fossil-based chemicals. Mechanistic insights behind thermochemical conversion of lignocellulose would facilitate thermo-catalytic process development for bio-based chemicals. This study employed synchrotron-based Fourier transform infrared (FTIR) microspectroscopy to investigate chemical changes in acid-catalyzed cellulose and lignocellulose and glucose during pyrolysis. Major changes in glucose occurred at 200 °C, where it underwent reactions including ring opening and tautomerization. Acid treatment did not change the molecular structure of cellulose but disrupted the lignocellulose network. The observed synchrotron FTIR spectral features provided evidence for acceleration of catalytic dehydration of cellulose and lignocellulose to levoglucosenone and furans. Catalytic passivation of alkali and alkaline earth metals in lignocellulose was also observed at low acid concentration.

16.
Waste Manag ; 90: 152-167, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30935785

RESUMO

Mixed municipal solid waste, consisting of ten major components such as yard waste, food waste, textile, paper, rubber, low-density polyethylene, high-density polyethylene, polypropylene, poly-(ethylene terephthalate) and polystyrene, is studied for performing thermal pyrolysis. Thermogravimetric analysis is utilised to quantify the interactions amongst these components, and also to compute the kinetic parameters of mixed municipal solid waste pyrolysis. The change in kinetic parameters, which is caused by interaction between components, has also been modelled. The calculated ratio of activation energy to the logarithm of the pre-exponential factor (E/logA) predicts the change in stability of the compounds during pyrolysis. For pyrolysis of individual compounds, the pyrolytic range of compounds is found to be 170-490 °C, with E/logA ranges between 10.54 and 13.9. However, considering all the binary interactions and the complex municipal solid waste matrix, the temperature range of pyrolysis expands to 170-520 °C, with stability ranges varying from 9.98 to 15.32. Furthermore, overlap ratio is calculated to quantify the intensity of these interactions. Rubber is found to cause maximum interactions which impose a negative synergistic effect on the pyrolytic decomposition behaviours of biomass and plastic mixtures, resulting in an overlap ratio of 0.9 and 0.95, respectively, for these mixtures.


Assuntos
Pirólise , Resíduos Sólidos , Biomassa , Cinética , Termogravimetria
17.
Proc Math Phys Eng Sci ; 475(2224): 20180830, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31105457

RESUMO

Carbon dioxide sequestration via carbonation of steel slags is a promising way of combining two waste products to create value. Understanding the dissolution kinetics of steel slags, which are alkaline and rich in calcium, in acidic media is essential to configure such a process. In this study, we seek to analyse the dissolution mechanism from experimental studies and develop a mathematical model considering the heterogeneous characteristics of slag. We found that the reduction in calcium extraction efficiency with an increase in particle size, which is normally associated with surface passivation or non-uniformity of samples, can be explained by considering the morphological features associated with the distribution of MgO-FeO (RO) phase in the calcium silicate matrix. We present a population balance model and show that the reduction in calcium extraction efficiency in coarse particle fractions is due to increased sporulation of the RO phase. The findings in the study suggest that the leaching of metal ions from slag is controlled by proton-promoted surface dissolution reaction, where the dependence of acid concentration follows the Langmuir-Hinshelwood adsorption isotherm. The model shows good agreement with a large set of parametric studies and demonstrates the importance of considering morphological features, as we progress towards development of a priori dissolution models for multi-mineral oxides and silicates.

18.
Materials (Basel) ; 12(4)2019 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-30795608

RESUMO

This review focusses on the use of recycled and virgin polymers in mineral and metallurgical processing, both high and ambient temperature processes, including novel applications. End of life applications of polymers as well as the utilisation of polymers during its life time in various applications are explored. The discussion includes applications in cleaner coal production, iron and steel production, iron ore palletisation, iron alloy manufacturing, manganese processing, E-wastes processing and carbon sequestration. The underlying principles of these applications are also explained. Advantages and disadvantages of using these polymers in terms of energy and emission reductions, reduction in non-renewables and dematerialisation are discussed. Influence of the polymers on controlling the evolution of micro and nanostructures in alloys and advanced materials is also considered.

19.
Sci Rep ; 8(1): 7484, 2018 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-29749394

RESUMO

Direct C-O hydrogenolysis of bioglycerine to produce 1,3-propanediol selectively is a vital technology that can expand the scope of biodiesel industry and green chemical production from biomass. Herein we report sulphuric acid-activated montmorillonite clay supported platinum nanoparticles as highly effective solid acid catalysts for the selective production of 1,3-propanediol from glycerol. The catalytic performances of the catalysts were investigated in the hydrogenolysis of glycerol with a fixed bed reactor under ambient pressure. The results were found promising and showed that the activation of montmorillonite by sulphuric acid incorporated Brønsted acidity in the catalyst and significantly improved the selectivity to 1,3-propanediol. The catalytic performance of different platinum loaded catalysts was examined and 2 wt% Pt/S-MMT catalyst presented superior activity among others validating 62% 1,3-propanediol selectivity at 94% glycerol conversion. The catalytic activity of 2Pt/S-MMT was systematically investigated under varying reaction parameters including reaction temperature, hydrogen flow rate, glycerol concentration, weight hourly space velocity, and contact time to derive the optimum conditions for the reaction. The catalyst stability, reusability and structure-activity correlation were also elucidated. The high performance of the catalyst could be ascribed to well disperse Pt nanoparticles immobilized on acid-activated montmorillonite, wider pore-structure and appropriate acid sites of the catalyst.

20.
Bioresour Technol ; 229: 1-10, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28088575

RESUMO

This two-part study firstly investigated Tetraselmis suecica grown in different CO2 (0.04-15%v/v) concentration through indoor and outdoor cultivation systems. A high CO2 concentration led to a high lipid content, and low nitrogen and oxygen content, which are desirable for transport fuel production. Pyrolysis characteristics were investigated by TG-IR and synchrotron IR microscopy. The results show Tetraselmis suecica grown in 10%CO2 had the highest decomposition rate corresponding to more volatile products produced during the main thermal cracking stage and derived from protein-and lipid-corresponding functional groups. Moreover, a high reaction temperature and CO2 concentration resulted in a low retention of surface functional groups. The nitrogen functional groups initially decomposed at a temperature range of 250-300°C and still remained at 550°C, while the lipid-corresponding functional groups completely disappeared at a temperature range of 400-500°C. Besides, the decomposition of chemical components followed the order of carbohydrate, protein and lipid.


Assuntos
Biotecnologia/métodos , Microalgas/crescimento & desenvolvimento , Síncrotrons , Temperatura , Termogravimetria/métodos , Dióxido de Carbono/farmacologia , Concentração de Íons de Hidrogênio , Luz , Microalgas/efeitos dos fármacos , Microalgas/efeitos da radiação , Espectroscopia de Infravermelho com Transformada de Fourier , Volatilização
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