Browsing by Author "Mendes, Benilde"
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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 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.
- 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.
- Hydrogenation of rapeseed oilPublication . Martins, Susana; Pinto, Filomena; Costa, Paula; Miranda, Miguel; Gonçalves, Maria Margarida; Gulyurtlu, Ibrahim; Mendes, BenildeRapeseed oil was rapeseed oil hydrogenated using a hydrogen pressure of 160psi, over a temperature range from 200ºC to 400ºC. Residence time was varied from 6 to 120 min. The reaction was performed in the absence and in the presence of specific inorganic catalyst. The gaseous liquid and solid yield were determined. The liquid phase was characterized using elemental analysis FT-IR, GC-HD (boiling point profile) and GC-MS (chemical families profile). At a temperature of 400ºC and a residence time of 120 min the yield of hydrocarbon products is 90% in the presence of catalyst and 83% in the absence of the catalyst.
- Hydrogenation of rapeseed oil for production of liquid bio-chemicalsPublication . Pinto, Filomena; Martins, Susana; Gonçalves, Maria Margarida; Costa, Paula; Gulyurtlu, Ibrahim; Alves, Andreia; Mendes, BenildeThe main objective of rapeseed oil hydrogenation tests was the production of liquid bio-chemicals to be used as renewable raw material for the production of several chemicals and in chemical synthesis to substitute petroleum derived stuff. As, hydrogenation of vegetable oils is already applied for the production of biofuels, the work done focused in producing aromatic compounds, due to their economic value. The effect of experimental conditions on rapeseed oil hydrogenation was studied, namely, reaction temperature and time with the aim of selecting the most favourable conditions to convert rapeseed oil into liquid valuable bio-chemicals. Rapeseed oil was hydrogenated at a hydrogen initial pressure of 1.10 MPa. Reaction temperature varied in the range from 200 C to 400 C, while reaction times between 6 and 180 min were tested. The performance of a commercial cobalt and molybdenum catalyst was also studied. The highest hydrocarbons yields were obtained at the highest temperature and reaction times tested. At a temperature of 400 C and at the reaction time of 120 min hydrocarbons yield was about 92% in catalyst presence, while in the absence of the catalyst this value decreased to 85%. Hydrocarbons yield was even higher when the reaction time of 180 min was used in the presence of catalyst, as the yield of 97% was observed. At these conditions hydrocarbons formed had a high content of aromatic compounds, around 50%. For this reason, the viscosity values of hydrogenated oils were lower than that established by EN590, which together with hydrogenated liquids composition prevented its use as direct liquid fuel to substitute fossil gas oil for transport sector. However, hydrocarbons analysis showed the presence of several valuable compounds that encourages their use as a raw material for the production of several chemicals and in chemical synthesis.
- 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.
- Production of bio-hydrocarbons by hydrotreating of pomace oilPublication . Pinto, Filomena; Varela, Francisco; Gonçalves, Maria Margarida; Andre, Rui N.; Costa, Paula; Mendes, BenildeOlive pomace oil is a by-product from the olive oil industry that is still being used in the food industry as a low value vegetable oil. Crude olive pomace oil needs to be refined and is blended with virgin olive oils before being used as edible oil. The detection of toxic compounds led to more restricted legislation and to the search of alternative valorisation processes, such as hydrotreating to obtain bio-hydrocarbons. Hydrotreating of olive pomace oil at moderate temperatures (from 300 to 430 C) and in presence of initial hydrogen pressure of 1.1 MPa led to triglycerides destruction and to their conversion into a large range of organic compounds with predominance to hydrocarbons. Even without any catalyst, conversions into hydrocarbons were always higher than 90% (v/v). Catalyst presence, such as: CoMo/Al2O3, FCC (fluid catalytic cracking) or HZSM-5 changed hydrogenated liquids composition. The highest content of alkanes was obtained with CoMo catalyst, while FCC and HZSM-5 led to the highest contents of aromatic compounds. The results obtained showed that olive pomace oil can be efficiently converted into bio-hydrocarbons with a wide range of applications. It was also studied the effect of pyrolysing olive pomace oil prior to its hydrotreating. Pyrolysis pre-treatment seems to have favoured hydrotreating process by promoting initial cracking reactions. Thus, it was possible to increase the production of liquid compounds with a higher content of light molecules. However, the advantages of using a more complex two steps process still need to be proven.