Loading...
22 results
Search Results
Now showing 1 - 10 of 22
- Toxicity of Ashes Produced During the Combustion and Co-combustion of Coal and Meat and Bone Meal in a Fluidized- Bed ReactorPublication . Barbosa, Rui; Lapa, Nuno; Lopes, Helena; Gulyurtlu, Ibrahim; Mendes, BenildeThe replacement of fossil fuels by renewable fuels can contribute to improve the environmental performance of the power production and to move forward in the sustainability way. The experience has shown that the availability of alternative fuels can be an obstacle for its extensive use for energy production, since biomass is not always available. The use of non-hazardous wastes may be a good alternative to biomass, mainly if they are economically unattractive for recycling or if they present a high cost for land-filling. The co-firing of non-hazardous wastes with coal is, therefore, a subject of great interest for the sustainability of energy production and the reduction of the emissions of fossil greenhouse gases. The use of these wastes for energy is promising if they combine well with other fuels during the conversion process for energy production and have no negative effect on the combustion system, on the ash quality and on the gaseous emissions.
- Chemical and bioassay fractionation of chars obtained in the co-pyrolysis of different wastesPublication . Bernardo, Maria; Lapa, Nuno; Gonçalves, Maria Margarida; Mendes, Benilde; Pinto, FilomenaThe present work is devoted to the study chars obtained in the co-pyrolisis of plastics, biomass and tyres wastes. The composition of these chars is not yet well studied and only recent an attempt was made by the aithors to provide some information about the composition and risk assessment of these materials. The objectives of this work were to perform solvent extractions, using differents, in chars obtained in the co-pyrolysis process to evaluate the extraction efficiency by characterising the different solvent extracts obtained as well as the extracted chars, to perform a chemical ans bioassay franctionation in the most toxic crude extraction in order to study the chemical composition of the fractions as well as their individual contribution to the global toxicity of the crude extarct. The results will allow to conclude which solvent should be used in the decontamination of the pyrolysis chars.
- Evaluation of the environmental hazard of char residues produced in the co-pyrolysis of different wastes :chemical and ecotoxicological characterizationPublication . Bernardo, Maria; Lapa, Nuno; Gonçalves, Maria Margarida; Barbosa, Rui; Mendes, Benilde; Pinto, Filomena; Gulyurtlu, IbrahimChar residues produced in co-pyrolysis of different wastes were characterized through chemical and toxicity tests. A fraction of the solid chars was treated by extraction with dichloromethane. Different volatilit fractions present in the extracted and non extrated char were evaluated. A selected group of heavy metals was determined in both chars. Chars were subjected to the leaching test ISO/TS 21268-2 and resulting eluates were further characterized by determining a group of inorganic parameters and concentrations of several organic contaminants. An ecotoxicological characterization was performed by using the bio-indicator Vibrio fischeri. The chemical and ecotoxicological characterization led to a classification on the chars as ecotoxic
- Evaluation of the toxicity of char residues produced in the co-pyrolysis of different wastesPublication . Bernardo, Maria; Lapa, Nuno; Gonçalves, Maria Margarida; Barbosa, Rui; Mendes, Benilde; Pinto, FilomenaThe high amounts of solid waste produced in industrial installations and in urban centers is a complex problem of today's society. The traditional strategies for solid waste transformation and disposal include and filling or incineration. Other approaches are being exploited namely waste selective collection and recycling on the energetic valorization of solid wastes through pyrolysis. In the pyrolytic process, the wastes are converted into a gaseous and liquid phase that can be used in energy production or as feedstock in chemistry industries. A solid residue (char) is also produced in a proportion that depends on the pyrolysis conditions. Even when the operating condiions are optimized in order to minimize the solid fraction, a resonable amount of chars are obtained. Those chars are mainly composed of a carbon-rich matrix that contains the mineral matter initially present in the wastes as well as components of the liquid fraction. Therefore, these solid residues have a toxicity potential due to the presence of heavy metals or organic compounds that must be assessed in order to define their safe reutilization or disposal. In the present study, the chars produced in the co-pyrolysis of plastics, pine biomass and tyres were characterized through chemical and ecotoxicological tests. A fraction of the solid chars was treated by extraction with dichloromethane. Different volatibility groups of compounds present in the extracted and non extracted char were evaluated. A selected group of heavy metals was determined in both chars. Chars were subjected to the leaching test ISO/TS 21268-2 and the resulting eluates were further characterized by determining a group of inorganic and organic parameters. An ecotoxicological characterization was performed by using he bio-indicator Vibrio fischeri. The chemical and ecotoxicological results were compared and analysed according to the council Decision 2003/33/CE and the Criteria on the Evaluation Methods of Waste Ecotoxicity (CEMWE). The results of the chemical characterization indicate that the extraction of the char residues with an appropriate organic solvent allows the sufficient elimination of the volatile organic contaminants thus decreasing the potential toxicity of these chars. The semi-volatile and non-volatile fractions were not, apparently, affected by this pre-treatment. Regarding the release of heavy metals from extracted and non-extracted chars during the leaching tests, a strong contamination with Zn was found in both eluates, which contribute to a classification of the corresponding chars as hazardous and ecotoxic materials. Also the results of the ecotoxicological characterization of the eluates led to a classification of these chars as ecotoxic materials.
- Cr(III) dynamic removal in a fixed-bed column by using a co-gasification charPublication . Dias, Diogo; Bernardo, Maria; Pinto, Filomena; Fonseca, Isabel Maria; Lapa, NunoABSTRACT: A char (GC) obtained from the co-gasification of rice husk and polyethylene was used in a fixed-bed column with continuous flow for Cr(III) removal assays from synthetic and industrial wastewaters. For comparison purposes, a commercial activated carbon (CAC) was also used. The best experimental conditions in the continuous removal assays were the following ones: Cr(III) inflow concentration = 5 mg L-1, feed flow rate = 3 mL min(-1), mass of adsorbent in the column = 0.8 g, and inflow temperature = 50 degrees C. Under these conditions, the highest uptake capacities were 1.60 and 2.14 mg g(-1) in the synthetic solution, and 3.25 and 7.83 mg g(-1) in the industrial wastewater, for GC and CAC, respectively. These results are different from those obtained under batch conditions in which GC performed better than CAC. Cr(III) removal by both adsorbents occurred due to precipitation, but CAC presented a slightly higher amount of Cr(III) removed due to its highest porosity. The regeneration of GC and CAC was also studied, but both adsorbents showed no capacity to be used in more than one cycle. This study highlighted the importance of studying Cr(III) removal under continuous conditions, as the removal mechanisms may be completely different from the batch assays, affecting the adsorbents' performance.
- Chemical and ecotoxicological properties of ashes produced in the co-combustion of coal and sewage sludgePublication . Barbosa, Rui; Lapa, Nuno; Boavida, Dulce; Lopes, Helena; Mendes, Benilde; Gulyurtlu, Ibrahim
- Biomass fly ashes as low-cost chemical agents for Pb removal from synthetic and industrial wastewatersPublication . Barbosa, Rui; Lapa, Nuno; Lopes, Helena; Gunther, Annika; Dias, Diogo; Mendes, BenildeThe main aim of this work was to study the removal efficiency of Pb from synthetic and industrial wastewaters by using biomass fly ashes. The biomass fly ashes were produced in a biomass boiler of a pulp and paper industry. Three concentrations of Pb2+ were tested in the synthetic wastewater (1, 10 and 1000 mg Pb/L). Moreover, two different wastewaters were collected in an industrial wastewater treatment plant (IWWTP) of an industry of lead-acid batteries: (i) wastewater of the equalization tank, and (ii) IWWTP effluent. All the wastewaters were submitted to coagulation–flocculation tests with a wide range of biomass fly ashes dosage (expressed as Solid/Liquid – S/L – ratios). All supernatants were characterized for chemical and ecotoxicological parameters. The use of biomass fly ashes has reduced significantly the Pb concentration in the synthetic wastewater and in the wastewaters collected in the IWWTP. For example, the definitive coagulation–flocculation assays performed over the IWWTP effluent presented a very low concentration of Pb (0.35 mg/L) for the S/L ratio of 1.23 g/L. Globally, the ecotoxicological characterization of the supernatants resulting from the coagulation–flocculation assays of all wastewaters has indicated an overall reduction on the ecotoxicity of the crude wastewaters, due to the removal of Pb.
- Leaching behaviour and ecotoxicity evaluation of chars from the pyrolysis of forestry biomass and polymeric materialsPublication . Bernardo, Maria; Mendes, S.; Lapa, Nuno; Gonçalves, Maria Margarida; Mendes, Benilde; Pinto, Filomena; Lopes, HelenaThe main objective of this study was to assess the environmental risk of chars derived from the pyrolysis of mixtures of pine, plastics, and scrap tires, by studying their leaching potential and ecotoxicity. Relationships between chemical composition and ecotoxicity were established to identify contaminants responsible for toxicity. Since metallic contaminants were the focus of the present study, an EDTA washing step was applied to the chars to selectively remove metals that can be responsible for the observed toxicity. The results indicated that the introduction of biomass to the pyrolysis feedstock enhanced the acidity of chars and promote the mobilisation of inorganic compounds. Chars resulting from the pyrolysis of blends of pine and plastics did not produce ecotoxic eluates. A relationship between zinc concentrations in eluates and their ecotoxicity was found for chars obtained from mixtures with tires. A significant reduction in ecotoxicity was found when the chars were treated with EDTA, which was due to a significant reduction in zinc in chars after EDTA washing.
- Use of chemical fractionation to understand partitioning of biomass ash constituents during co-firing in gluidized bed combustionPublication . Teixeira, P. Alexandra; Lopes, Helena; Gulyurtlu, Ibrahim; Lapa, Nuno
- Opportunities and Constraints of the Adsorption of Rare Earth Elements onto Pyrolytic Carbon-Based Materials: A Mini-ReviewPublication . Nogueira, Miguel; Bernardo, Maria; Ventura, Márcia; Matos, Inês; Pinto, Filomena; Lapa, NunoABSTRACT: Rare earth elements (REEs), comprising seventeen metallic elements, including lanthanides, scandium, and yttrium, are indispensable for modern technological industries due to their unique properties. However, their supply is critically risky for the European Union, with 95% of global production concentrated in China, Brazil, Vietnam, Russia, India, and Australia. This mini-review examines the adsorption of REEs onto pyrolytic carbon-based materials as a sustainable recovery method from secondary raw materials. The review covers different types of carbon-based adsorbents used in several research works, such as activated carbon, chars, and biochar, and discusses their adsorption mechanisms and influencing factors. Comparative analyses of adsorption capacities highlight the significance of surface area and functionalization in enhancing adsorption efficiency. Despite promising results, the variability in adsorption performance due to experimental conditions and the scarcity of real-world application studies are noticed. This review underscores the need for further research using real e-waste leachates to validate the practical applicability of pyrolytic carbon-based adsorbents for REEs' recovery, aiming for an economically and environmentally sustainable solution.
- «
- 1 (current)
- 2
- 3
- »