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1.
Bioresour Technol ; : 126057, 2021 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-34597808

RESUMO

Biohydrogen (BioH2) is considered as one of the most environmentally friendly fuels and a strong candidate to meet the future demand for a sustainable source of energy. Presently, the production of BioH2 from photosynthetic organisms has raised a lot of hopes in the fuel industry. Moreover, microalgal-based BioH2 synthesis not only helps to combat current global warming by capturing greenhouse gases but also plays a key role in wastewater treatment. Hence, this manuscript provides a state-of-the-art review of the upstream and downstream BioH2 production processes. Different metabolic routes such as direct and indirect photolysis, dark fermentation, photofermentation, and microbial electrolysis are covered in detail. Upstream processes (e.g. growth techniques, growth media) also have a great impact on BioH2 productivity and economics, which is also explored. Technical and scientific obstacles of microalgae BioH2 systems are finally addressed, allowing the technology to become more innovative and commercial.

2.
Bioresour Technol ; : 126096, 2021 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-34626763

RESUMO

Microalgae are the most prospective raw materials for the production of biofuels, pyrolysis is an effective method to convert biomass into bioenergy. However, biofuels derived from the pyrolysis of microalgae exhibit poor fuel properties due to high content of moisture and protein. Co-pyrolysis is a simple and efficient method to produce high-quality bio-oil from two or more materials. Tires, plastics, and bamboo waste are the optimal co-feedstocks based on the improvement of yield and quality of bio-oil. Moreover, adding catalysts, especially CaO and Cu/HZSM-5, can enhance the quality of bio-oil by increasing aromatics content and decreasing oxygenated and nitrogenous compounds. Consequently, this paper provides a critical review of the production of bio-oil from co-pyrolysis of microalgae with other biomass wastes. Meanwhile, the underlying mechanism of synergistic effects and the catalytic effect on co-pyrolysis are discussed. Finally, the economic viability and prospects of microalgae co-pyrolysis are summarized.

3.
Bioresour Technol ; : 126067, 2021 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-34601023

RESUMO

Recent studies show that fast hydropyrolysis (i.e., pyrolysis under hydrogen atmosphere operating at a rapid heating rate) is a promising technology for the conversion of biomass into liquid fuels (e.g., bio-oil and C4+ hydrocarbons). This pyrolysis approach is reported to be more effective than conventional fast pyrolysis in producing aromatic hydrocarbons and also lowering the oxygen content of the bio-oil obtained compared to hydrodeoxygenation (a common bio-oil upgrading method). Based on current literature, various non-catalytic and catalytic fast hydropyrolysis processes are reviewed and discussed. Efforts to combine fast hydropyrolysis and hydrotreatment process are also highlighted. Points to be considered for future research into fast hydropyrolysis and pending challenges are also discussed.

4.
Bioresour Technol ; : 126140, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34662739

RESUMO

Artificial neural network (ANN) is one kind of artificial intelligence in the computing system that aims to process information as the way neurons in the human brain. In this study, the combination of the Taguchi method and ANN are used to maximize and predict biofuel yield from spent mushroom substrate torrefaction and pyrolysis via microwave irradiation. The Taguchi method is utilized to design the multiple factors (particle size, catalyst, power, and magnetic agent) and levels of experiment parameters. The highest total biofuel yield (biochar + bio-oil) is 99.42%, accomplished by a combination of 355 µm particle size, 300 mg·g-SMS-1 catalyst, 900 W power, and 300 mg·g-SMS-1 magnetic agent. ANN with one hidden layer shows the outstanding linear regression predictions for the highest biofuel yields (biochar 0.9999 and bio-oil 0.9998). This high linear regression indicates that ANN with a quick propagation algorithm is an appropriate approach for predicting biofuel conversion.

5.
J Hazard Mater ; 416: 125856, 2021 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-34492805

RESUMO

Inhalation of aerosols such as pharmaceutical aerosols or virus aerosol uptake is of great concern to the human population. To elucidate the underlying aerosol dynamics, the deposition fractions (DFs) of aerosols in healthy and asthmatic human airways of generations 13-15 are predicted. The Navier-stokes equations governing the gaseous phase and the discrete phase model for particles' motion are solved using numerical methods. The main forces responsible for deposition are inertial impaction forces and complex secondary flow velocities. The curvatures and sinusoidal folds in the asthmatic geometry lead to the formation of complex secondary flows and hence higher DFs. The intensities of complex secondary flows are strongest at the generations affected by asthma. The DF in the healthy airways is 0%, and it ranges from 1.69% to 52.93% in the asthmatic ones. From this study, the effects of the pharmaceutical aerosol particle diameters in the treatment of asthma patients can be established, which is conducive to inhibiting the inflammation of asthma airways. Furthermore, with the recent development of COVID-19 which causes pneumonia, the predicted physics and effective simulation methods of bioaerosols delivery to asthma patients are vital to prevent the exacerbation of the chronic ailment and the epidemic.


Assuntos
Asma , COVID-19 , Aerossóis , Asma/tratamento farmacológico , Simulação por Computador , Humanos , Pulmão , Modelos Biológicos , Tamanho da Partícula , SARS-CoV-2
6.
J Hazard Mater ; 423(Pt A): 127032, 2021 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-34474365

RESUMO

An integrated gasification-flameless combustion-melting process was approached by a twin-cyclonic flow in a hazardous waste thermal treatment plant. A series of advanced scrubber, cyclonic demister, activated carbon adsorption, and baghouse processes were equipped for the end-of-pipe treatment. The untreated filterable particulate matter, CO, and NOx levels were only 283, 47.1, and 15.9 mg/Nm3, indicating the flameless combustion inhibited their formation by narrowing the post-combustion zone. The filterable particle mass-size distribution was equally contributed by nucleation, accumulation, and coarse formations, while their number concentration was predominated by nucleation (99.6%). That could enhance the adsorption of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) on ultrafine particles. Both total mass and toxic equivalent concentrations of PCDD/Fs were reduced 99.9% by the new air pollution control system when a slight reformation occurred during scrubbing. However, the escaped PCDD/Fs were mainly distributed on the ultrafine particles, which should be further inhibited by either increasing their sizes or equipping backup filtrations. Finally, the new process concentrates the PCDD/Fs into the scrubbing sludge, which could be recirculated back into the thermal process. This study not only reveals the emission risk of the ultrafine particle-bound PCDD/Fs, but also provides an effective process to remove them for industrial application.

7.
Sci Total Environ ; 792: 148329, 2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34465047

RESUMO

The emission factor (EF), the weight of potentially toxic elements (PTEs) per unit energy or weight of sinter produced were evaluated for coal-fired boilers and sintering furnaces integrated in a steel plant. From three coal-fired boilers, 15 samples were taken while 22 samples were taken from four sintering furnaces. Investigations were performed on the EF of lead, cadmium, mercury, arsenic and chromium (VI). The coefficient of variance for the first 3 samples from each PTE was used to decide whether 2 more samples were necessary for the investigation. Three samples were sufficient for Cr (VI), however, 5 samples were required for Pb, Cd, Hg, and As, since the variances in concentrations of the first three samples exceeded 20%. The ranges for the ratio of the laboratory-based EF to the default EF applied by the Environment Protection Administration (EPA Taiwan) for Pb, Cd, Hg, and As for the coal-fired boiler were 0.08-0.013, 0.014-0.017, 0.019-0.033, 0.047-0.066 and for the sintering furnaces were 0.059-0.232, 0.05-0.151, 0.05-0.364, and 0.067-0.824. The ratio for Cr (VI)- was constant at 0.005 for all the coal fired boilers while it ranged from 0.057-0.709 for the sintering furnaces. Whilst source identification, enrichment factors, and spatial distributions for PTEs are often studied, laboratory-based investigations on the EFs for PTEs from industrial plants are rarely performed. This study filled the information gap and compared the obtained EFs with the EPA default values. To avoid overcharging industrial plants equipped with the best available technology for emission control, the EPA should apply field investigations and laboratory-based EFs instead of the default EPA EFs to calculate air pollution fees. Insights from this investigation can be applied to promote the adoption of appropriate air pollution control devices to cut down the emission of PTEs.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Mercúrio , Poluentes Atmosféricos/análise , Carvão Mineral/análise , Centrais Elétricas , Aço
8.
Chemosphere ; 287(Pt 1): 132014, 2021 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-34523445

RESUMO

Biohydrogen and biosyngas are among the sustainable bioenergy products from biomass resources through gasification. Microwave-assisted gasification (MAG) is still a novel technology, but it is definitely a promising conversion technology to achieve a sustainable bioeconomy. Although this technology shows a massive potential to be fully implemented in the near future, the selectivity and efficiency of biohydrogen and syngas production still need enhancements and further research to secure a cost-effective and energy-efficient industrialization. This article comprehensively reviews the regular, microwave-induced plasma, and catalytic MAG systems in relation to their biohydrogen and biosyngas production, carbon conversion efficiency, and tar removal while discussing the significance of optimal operating conditions and considerations in the gasification system design. Several perspectives such as benefits, challenges, numerical simulations, and scalable opportunities are also explored to provide factual insights for further research and industrial application.

9.
J Hazard Mater ; 423(Pt A): 126921, 2021 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-34523506

RESUMO

Colourants, micropollutants and heavy metals are regarded as the most notorious hazardous contaminants found in rivers, oceans and sewage treatment plants, with detrimental impacts on human health and environment. In recent development, algal biomass showed great potential for the synthesis of engineered algal adsorbents suitable for the adsorptive management of various pollutants. This review presents comprehensive investigations on the engineered synthesis routes focusing mainly on mechanical, thermochemical and activation processes to produce algal adsorbents. The adsorptive performances of engineered algal adsorbents are assessed in accordance with different categories of hazardous pollutants as well as in terms of their experimental and modelled adsorption capacities. Due to the unique physicochemical properties of macroalgae and microalgae in their adsorbent forms, the adsorption of hazardous pollutants was found to be highly effective, which involved different mechanisms such as physisorption, chemisorption, ion-exchange, complexation and others depending on the types of pollutants. Overall, both macroalgae and microalgae not only can be tailored into different forms of adsorbents based on the applications, their adsorption capacities are also far more superior compared to the conventional adsorbents.

10.
Chemosphere ; 287(Pt 1): 131969, 2021 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-34450364

RESUMO

With the quick increase in industrialization and urbanization, a mass of sludge has been produced on the account of increased wastewater treatment facilities. Sewage sludge (SS) management has become one of the most crucial environmental problems because of the existence of various pollutants. However, SS is a carbon-rich material, which has favored novel technologies for biochar production, which can be utilized for dissimilar applications. This review systematically analyzes and summarizes the pretreatment, modification, and especially application of sewage sludge-derived biochar (SSBC), based on published literature. The comparative assessment of pretreatment technology such as pyrolysis, hydrothermal carbonization, combustion, deashing, and co-feeding is presented to appraise their appropriateness for SS resource availability and the production of SSBC. In addition, the authors summarize and analyze the current modification methods and divide them into two categories: physical properties and surface chemical modifications. The applications of SSBC as absorbent, catalyst and catalyst support, electrode materials, gas storage, soil amendment, and sold biofuel are reviewed in detail. Furthermore, the discussion about the existing problems and the direction of future efforts are presented at the end of each section to envisage SS as a promising opportunity for resources rather than a nuisance.

11.
J Hazard Mater ; 421: 126752, 2021 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-34352524

RESUMO

In this study, environmentally-friendly nanocomposite hydrogels were fabricated. These hydrogels consisted of semi-interpenetrating networks of carboxymethyl cellulose (CMC) molecules grafted to polyacrylic acid (PAA), as an eco-friendly and non-toxic polymer with numerous carboxyl and hydroxyl functional groups, which were reinforced with different levels of graphene oxide particles (0.5, 1.5 or 3% wt). Field-emission electron scanning microscopy (FESEM) images indicated that the pore size of the nanocomposites decreased with increasing graphic oxide concentration. The presence of the graphic oxide increased the storage modulus and thermal stability of the nanocomposite hydrogels. The hydrogels had an adsorption capacity of 138 mg/g of a model cationic dye pollutant (methylene blue) after 250 min. Moreover, a reusability test showed that the adsorption capacity remained at around 90% after 9 cycles. Density functional theory (DFT) simulations suggested that the adsorption of methylene blue was mainly a result of π-π bonds, hydrogen bonds, and electrostatic interactions with graphene oxide. Our results indicated that the nanocomposite hydrogels fabricated in this study may be eco-friendly, stable, efficient, and reusable adsorbents for ionic pollutants in wastewater treatment.

12.
J Environ Manage ; 298: 113450, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34388542

RESUMO

The study deals with the pyrolysis of sewage sludge to produce eco-friendly and sustainable fuels along with value-added biochar products. The experiments were conducted in a fixed-bed cylindrical glass reactor in the temperature range of 250-700 °C and achieved the product yield of 22.4 wt% bio-oil, 18.9 wt % pyrolysis gases, and 58.7 wt% biochar at 500 °C optimum temperature. The chemical composition of bio-oil was investigated by gas chromatograph-mass spectroscopy and fourier transformation infrared techniques. The ASTM standard procedures were used to assess the fuel qualities of bio-oil, and they were found to be satisfactory. Bio-oil has a greater H/C ratio (3.49) and a lower O/C ratio (1.10), indicating that it is suitable for engine use. The gas chromatographic analysis of pyrolysis gases confirmed the presence of 41.16 wt % combustible gases, making it suitable for use in spark-ignition engines. X-ray fluorescence analysis of biochar showed that it had a good amount of carbon, nitrogen, phosphorus, and potassium along with some micro-and macro-nutrient which proves its potential to utilize as organic manure in the agriculture sector. In addition, the data obtained from the TGA analysis during the pyrolysis of sewage sludge was applied to calculate kinetic parameters via the Coats-Redfern method.


Assuntos
Pirólise , Esgotos , Biocombustíveis/análise , Carvão Vegetal
13.
Bioresour Technol ; 341: 125813, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34454233

RESUMO

Present study provides biohydrogen production methods from waste furniture via catalytic steam gasification with bio-char catalysts (raw char, KOH-activated char and steam-activated char). Total gas yield for the prepared chars was in the order of KOH-activated char > steam-activated char > raw char, whereas, H2 selectivity was in the sequence of raw char > steam-activated char > KOH-activated char. Though KOH-activated char showed the highest gas yield, highest H2 selectivity was obtained at the gasification experiment with raw char due to the large amount of Ca and K and its reasonable surface area (146.89 m2/g). Although the activation of raw biochar results in the increase of gas yield, it has the negative effect on H2 generation due to the removal of alkali and alkaline earth metals for the KOH activated char and steam-activated char. This study shows that raw bio-char could be a potential solution for eco-friendly hydrogen production.


Assuntos
Oryza , Biomassa , Catálise , Hidrogênio , Decoração de Interiores e Mobiliário , Vapor
14.
J Hazard Mater ; 418: 126381, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34329008

RESUMO

As plastics have been omnipresent in society ever since their introduction in 1907, global plastic production has ballooned in the 20th century or the Plasticene Era (Plastic Age). After their useful life span, they deliberately or accidentally, are disposed of in the environment. Influenced by different factors, plastics undergo fragmentation into microplastics (MPs) and present hazardous risks in all life forms including humans. Obliterating MPs from the environment has been a global challenge for the attainment of sustainable development goals (SDGs). This review aims to present MP degradation routes with a great focus on the thermodegradation and biodegradation routes as sustainable routes of MP degradation. These routes can achieve the reduction and obliteration of MPs in the environment, thus reducing their hazardous effects. Moreover, the thermodegradation of MPs can produce fuels that help solve the dilemma of energy security. Overall, continued research and development are still needed, however, these novel approaches and the increased awareness of the microplastics' hazards give us hope that we can achieve sustainable development in the near future.


Assuntos
Microplásticos , Poluentes Químicos da Água , Biocombustíveis , Monitoramento Ambiental , Humanos , Plásticos , Poluentes Químicos da Água/análise
15.
J Biotechnol ; 338: 81-90, 2021 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-34298023

RESUMO

Microalgae are a promising feedstock for carbon-neutral biofuel production due to their superior cellular composition. Alternatively, oxidative torrefaction has been recognized as a potential thermochemical technique for microalgal solid biofuel upgrading. Herein, by using microalga N. oceanica as a feedstock, several characterizations are adopted for evaluating the potential of oxidative torrefaction towards microalgal solid biofuel production. The oxidatively torrefied microalgae can be upgraded as lignite. After in-depth analysis, significant change in the surface microstructure of oxidatively torrefied microalgae is largely changed (via wrinkle and fragmentation) The hydrophobicity, thermal decomposition, thermal stability, and aromatization of oxidatively torrefied microalgae can be largely enhanced as the oxidative torrefaction severity increase. With the increasing torrefaction temperature, the hydrophobicity of oxidative torrefied microalgae gradually improved. The decomposition of C-2/3/5, and -OCH3, the CO bonds of CH3CO-, and the aromatization occurs via oxidative torrefaction according to the NMR analysis. For XPS analysis, torrefaction operation significantly decreases the carbide carbon and enhances the graphitization. As a result, the thermal stability of oxidatively torrefied microalgae is improved. Conclusively, the information obtained in this study can provide insights into the evaluation of oxidative torrefaction performance and fuel properties of microalgal solid biofuel, which may help accelerate the advancement of oxidative torrefaction industrialization.


Assuntos
Microalgas , Estramenópilas , Biocombustíveis , Biomassa , Estresse Oxidativo , Temperatura
16.
Pain ; 2021 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-34174041

RESUMO

ABSTRACT: Chronic pain is often accompanied by anxiety and depression disorders. Amygdala nuclei play important roles in emotional responses, fear, depression, anxiety, and pain modulation. The exact mechanism of how amygdala neurons are involved in pain and anxiety is not completely understood. The central nucleus of the amygdala contains 2 major subpopulations of GABAergic neurons that express somatostatin (SOM+) or protein kinase Cδ (PKCδ+). In this study, we found about 70% of phosphorylated ERK-positive neurons colocalized with PKCδ+ neurons in the formalin-induced pain model in mice. Optogenetic activation of PKCδ+ neurons was sufficient to induce mechanical hyperalgesia without changing anxiety-like behavior in naïve mice. Conversely, chemogenetic inhibition of PKCδ+ neurons significantly reduced the mechanical hyperalgesia in the pain model. By contrast, optogenetic inhibition of SOM+ neurons induced mechanical hyperalgesia in naïve mice and increased phosphorylated ERK-positive neurons mainly in PKCδ+ neurons. Optogenetic activation of SOM+ neurons slightly reduced the mechanical hyperalgesia in the pain model but did not change the mechanical sensitivity in naïve mice. Instead, it induced anxiety-like behavior. Our results suggest that the PKCδ+ and SOM+ neurons in the central amygdala exert different functions in regulating pain-like and anxiety-like behaviors in mice.

17.
J Environ Manage ; 294: 112992, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34116302

RESUMO

Torrefaction is a thermochemical process used to convert the biomass into solid fuel. In this study, torrefaction increased the raw microalgal biomass' energy content from 20.22 MJ⋅kg-1 to 27.93 MJ⋅kg-1. To determine if more energy is produced than energy consumption from torrefaction, this study identified the energy balance of torrefied microalgal biomass production based on a life cycle approach. The energy analysis showed that, among all processes, torrefaction had the least amount of energy demand. The experimental setup, defined as scenario A, revealed that the principal source of energy demand, about 85%, was consumed on the microalgal growth using a photobioreactor system. A sensitivity analysis was also performed to determine the varying energy demand for torrefied microalgal biomass production. The different types of cultivation methods and various production scales were considered in scenarios B to D. Scenario D, which represented the commercial production-scale, the energy demand drastically decreased by 59.46% as compared to the experimental setup (scenario A). The open-pond cultivation system resulted in the least energy requirement, regardless of the production scale (scenarios B and C) among all the given scenarios. Unlike scenarios A and D, scenarios B and C identified the drying process to consume a high amount of energy. All the scenarios have shown an energy demand deficit. Therefore, efforts to decrease the energy demand on the upstream processes are needed to make the torrefied microalgal biomass a viable alternative energy source.


Assuntos
Microalgas , Animais , Biocombustíveis , Biomassa , Estágios do Ciclo de Vida
18.
J Hazard Mater ; 418: 126278, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34098259

RESUMO

Phycoremediation is an emerging technology, where algae-based processes were used to effectively remove nutrients, organic wastes, and toxic heavy metals from the polluted environment. The waste algal biomass obtained after phycoremediation, which may contain residual hazardous materials, could still be used as feedstock to produce biofuels/bioenergy preferably through thermochemical conversion technology. This review proposes a synergistic approach by utilizing the phycoremediation-derived algal biomass (PCDA) as feedstock for efficient hazardous waste treatment and clean energy generation via supercritical water gasification (SCWG). The review provides an in-depth study of catalytic, non-catalytic, and continuous SCWG of algal biomass, aiming to lay out the foundations for future study. In addition, the concepts of heat integration as well as water, nutrient, and CO2 recycling were introduced for a sustainable algae-to-biofuel process, which significantly enhances the overall energy and material efficiency of SCWG. The production of biofuel from algal biomass via other advanced gasification technologies, such as integration with other thermochemical conversion techniques, co-gasification, chemical looping gasification (CLG), and integrated gasification and combined cycle (IGCC) were also discussed. Furthermore, the discussion of kinetics and thermodynamics models, as well as life cycle and techno-economic assessments, appear to provide insights for future commercial applications.


Assuntos
Biocombustíveis , Água , Biomassa , Catálise , Plantas , Águas Residuárias
19.
Environ Pollut ; 285: 117196, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-33962308

RESUMO

This research aims to study the wet torrefaction (WT) and saccharification of sorghum distillery residue (SDR) towards hydrochar and bioethanol production. The experiments are designed by Box-Behnken design from response surface methodology where the operating conditions include sulfuric acid concentration (0, 0.01, and 0.02 M), amyloglucosidase concentration (36, 51, and 66 IU), and saccharification time (120, 180, and 240 min). Compared to conventional dry torrefaction, the hydrochar yield is between 13.24 and 14.73%, which is much lower than dry torrefaction biochar (yield >50%). The calorific value of the raw SDR is 17.15 MJ/kg, which is significantly enhanced to 22.36-23.37 MJ/kg after WT. When the sulfuric acid concentration increases from 0 to 0.02 M, the glucose concentration in the product increases from 5.59 g/L to 13.05 g/L. The prediction of analysis of variance suggests that the best combination to maximum glucose production is 0.02 M H2SO4, 66 IU enzyme concentration, and 120 min saccharification time, and the glucose concentration is 30.85 g/L. The maximum bioethanol concentration of 19.21 g/L is obtained, which is higher than those from wheat straw (18.1 g/L) and sweet sorghum residue (16.2 g/L). A large amount of SDR is generated in the kaoliang liquor production process, which may cause environmental problems if it is not appropriately treated. This study fulfills SDR valorization for hydrochar and bioenergy to lower environmental pollution and even achieve a circular economy.


Assuntos
Sorghum , Grão Comestível , Poluição Ambiental , Triticum
20.
Environ Pollut ; 285: 117244, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-33965857

RESUMO

A green approach using hydrogen peroxide (H2O2) to intensify the fuel properties of spent coffee grounds (SCGs) through torrefaction is developed in this study to minimize environmental pollution. Meanwhile, a neural network (NN) is used to minimize bulk density at different combinations of operating conditions to show the accurate and reliable model of NN (R2 = 0.9994). The biochar produced from SCGs torrefied at temperatures of 200-300 °C, duration of 30-60 min, and H2O2 concentrations of 0-100 wt% is examined. The results reveal that the higher heating value (HHV) of biochar increases with rising temperature, duration, or H2O2 concentration, whereas the bulk density has an opposite trend. The HHV, ignition temperature, and bulk density of biochar from torrefaction at 230 °C for 30 min with a 100 wt% H2O2 solution (230-100%-TSCG) are 27.00 MJ∙kg-1, 292 °C, and 120 kg∙m-3, respectively. This HHV accounts for a 29% improvement compared to that of untorrefied SCG. The contact angle (126°), water activity (0.51 aw), and moisture content (7.69%) of the optimized biochar indicate that it has higher resistance against biodegradation, and thereby can be stored longer. Overall, H2O2 is a green treatment additive for SCGs solid fuel. This study has successfully produced biochar with greater HHV and low bulk density at low temperatures. The green additive development can effectively reduce environmental pollutants and upgrade wastes into resources, and achieve "3E", namely, environmental (non-polluting green additives), energy (biofuel), and circular economy (waste upgrade). In addition, the produced biochar has great potential in the fields of bioadsorbents and soil amendments.


Assuntos
Café , Peróxido de Hidrogênio , Carvão Vegetal , Poluição Ambiental
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