Browsing by Author "Barbosa, Rui"
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- 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.
- Characterization of chars produced in the co-pyrolysis of different wastes: decontamination studyPublication . Bernardo, Maria; Lapa, Nuno; Gonçalves, M.; Barbosa, Rui; Mendes, Benilde; Pinto, FilomenaThe present work is devoted to the study of chars obtained in the co-pyrolysis of plastics, biomass and tyres wastes. The chars were extracted with several organic solvents in order to assess the more efficient in redicing the organic load of trhe chars and, therefore their toxicity. The ability of each selected extractant to remove toxic pollutants was evaluated by comparing the extracts yield and thoroughly characterizing the different crude extarcts obtained by combining chemical analysis and toxicity biossays. Also, the mineral composition of the treated and non treated chars was assessed. The results will allow to conclude which solvent should be used in the decontamination of the pyrolysis chars.
- 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
- 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.
- Innovative reactor prototype for Hydrogen production in a stationary application using sodium borohydridePublication . Barbosa, Rui; Ferreira, V.; Silva, D.; Condes, J.; Ramos, S.; Amaral, V.; Pinto, A. M. F. R.; Figueiredo, A.; Rangel, C. M.Hydrogen storage has proved to be the greatest obstacle preventing hydrogen from replacing fossil fuels. Hence, a safe, efficient and economical method of storing hydrogen must be available to turn viable a hydrogen economy based on renewable resources [1]. Hydrogen can be stored in chemical hydrides such as sodium borohydride (NaBH4), with large theoretical H2 content of 10,9 wt%. With the aid of catalysts, and at room temperatures, the alkaline hydrolysis of NaBH4 can be enhanced [2]. In this work, a 100 L innovative reactor for hydrogen production was designed, based on the optimized layout of a laboratorial scale reactor [3], as part of a project financed by the Portuguese financial support program NSRF. The developed system has the capability to feed a 5 kW PEM fuel cell with a maximum hydrogen consumption of 75 slpm. The NaBH4 solution is stored in a 50 L reservoir from where seven consecutive 7,0 L injections to the reactor are possible. The Ni-Ru based catalyst applied can be re-used several times without losing its performance [1] and because of this capacity its replacement will be done, manually, every seven NaBH4 solution injections (simultaneously with the residual solution removal and the reactor cleaning). The catalyst should then be recovered for further utilization. Additionally to the reactor, a 400 to 500 L reservoir was also designed to be used as the system buffer since the reactor works in batch mode and it is desired that the PEMFC operates continuously. The system was conceived for stationary applications and eventually to be installed in remote areas, reason why the systemś monitoring and control are fully automatized. Its hydropneumatic circuit layout is characterized by four parts: injection system, reactor, valves bloc and buffer. It is assumed that the designed system can operate continuously throughout 15 hours with a medium hydrogen consumption of 10 slpm, which can supply a daily household energy power demand.
- 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.