Percorrer por autor "Oliveira, Nelson S."
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- Adsorption Behavior and Mechanism of Oxytetracycline on Rice Husk Ash: Kinetics, Equilibrium, and Thermodynamics of the ProcessPublication . Andrade, Christhel A.; Zambrano-Intriago, Luis Angel; Oliveira, Nelson S.; Vieira, Judite S.; Quiroz-Fernández, Luis Santiago; Rodríguez-Díaz, Joan ManuelThe main objective of the present study is to determine the kinetics, thermodynamics, and adsorption mechanism of the oxytetracycline (OTC) on rice husk ash (RHA). The adsorbent was characterized by scanning electronic microscopy, Fourier transform infrared spectroscopy, and nitrogen physisorption. Batch studies were carried out to evaluate the influence of the adsorbent dose, initial concentration, contact time, temperature, and initial pH. RHA was characterized as having heterogeneous, fibrous, and porous particles, consisting predominantly of silica. The removal of OTC depends on the pH of the medium, which is favored at acid pH values. The kinetic data followed the Bangham model, which indicated an OTC diffusion in the pores of RHA, although this was not the only process, as demonstrated through the use of the Weber-Morris model (IPD model). The Sips isotherm best represents the experimental results of the equilibrium study. It was found that the adsorption process was spontaneous and endothermic. The highest adsorption capacity was found at a pH in the range of 4–6, when the OTC is in its zwitterion form and the surface of the RHA is positively charged, thus permitting electrostatic interactions and the formation of hydrogen bonds between the adsorbent and adsorbate molecules. These findings demonstrate the potential of rice husk ash to remove oxytetracycline from water.
- Anaerobic Mesophilic Co-Digestion of Swine Slurry and Hidrolyzate in Batch Reactors: A Case StudyPublication . Domingues, Paulo S.; Pala, Helena; Oliveira, Nelson S.The management of residual flows from swine farms, such as slurry and hydrolyzate, is a serious environmental problem in Portugal, so the search for new solutions is important, especially if they can be implemented in production sites, avoiding the transport of waste. Anaerobic co-digestion can configure a sustainable method of management and valorization of these flows in swine farms, resulting in biogas to produce energy and a digestate with agronomic value. The swine hydrolyzate is the product from the elimination of swine carcasses on the farms, through a hydrolysis process. Its use in the anaerobic process wasn’t found in the literature, identifying the need to evaluate its potential. Thus, anaerobic co-digestion of swine slurry and hydrolyzate was carried out and the main purpose of this research was to find the best feeding ratio between the two substrates in batch test, focusing on biogas production. The study was developed in two phases, both under mesophilic conditions. In the first one, using 100 ml syringes, the effect of the relative proportion of substrates on the anaerobic co-digestion potential was investigated and the effect of pressure sterilization of the substrates on biogas production was verified. In the second phase, a larger scale study was carried out in a 4,500 ml digestor, ran under the conditions identified as the most favorable in the preliminary tests. The results obtained allowed us to conclude that the largest volume of accumulated biogas was obtained with the proportion of 90.9% swine slurry: 9.1% swine hydrolyzate (v/v); and that the sterilization of the substrates doesn’t constitute an effective thermal pre-treatment. The larger scale test revealed an inefficient anaerobic process due to the inhibitory effect caused by the accumulation of ammonia and volatile organic acids. However, the production yield was 606.8 LBiogas/kgVS and 431.6 LMethane/kgVS, indicating that process allowed a production of biogas and methane higher than the values cited in literature for anaerobic digestion of swine slurry. This result showed that the use of swine hydrolyzate as a co-substrate results in a better balance of nutrients, promoting a better development of microorganisms.
- Design of Pyrolysis System to Convert Waste Plastic to FuelsPublication . Oliveira, Nelson S.; Pardo, Michael; Capela, Carlos; Gaspar, Marcelo; Vasco, Joel; Heleno, LizeteThe conventional recycling technology to process waste plastic, mechanical recycling, is not suitable to recycle waste thermoplastic with high content of contamination. Pyrolysis is a promising technology since it can convert into valuable products, such as fuels and monomers. This study focused on the design of the pyrolysis equipment for waste plastic based on polyolefins. The feeder of waste plastic is a worm screw conveyor that will be in a pre-heating system. The batch reactor has support for catalyzer and can operate between 300 up to 600 ºC with attached induction system for heating. The output flows into condenser in series to separate two liquid phases and gases, depending on its boiling point. The 3D model was done with SolidWorks, control system modelled in CADe SIMU and particle simulation with FloXpress.
- Feasibility Study of the PET Fines Incorporation into Recycling ProcessesPublication . Nascimento, Bruna Guilherme do; Bozzola, Fernando; Vasco, Joel C.; Parnigoni, Milena; Capela, Carlos; Heleno, Lizete; Gaspar, Marcelo; Oliveira, Nelson S.Circular economy principles focus on the need to preserve natural resources and foster the use of environmentally sustainable practices. Concerning the use of plastics in a circular economy, increasingly demanding solutions have to be developed towards the zero-waste goal sought after by researchers and society alike. Particular attention has been put into the recycling of PET, mainly due to its wide spectrum of use and, consequently, to large volumes of related waste. The PET mechanical recycling process requires these waste materials to be shredded into PET flakes. Following such a procedure, these flakes are pelletized to be used again as feedstock. Considering the main stages of the mechanical recycling processes, which include plastic screening, shredding and washing, significant amounts of end waste materials are generated. This end-waste integrates small scale particles that are designated by plastic fines. Concerning the PET recycling process, the PET fines resulting from its mechanical recycling are not currently valued due to several technical issues, such as their high contamination level and the complexity of sorting them from other small-size particles. Current research focuses on the feasibility of incorporating these PET fines into the film/injection extruders, avoiding this way the need for an intermediate pelletization stage. To allow for such direct incorporation of PET fines into recycling processes, different decontamination and sorting solutions were implemented and tested. The current study is based on analyzing the mechanical properties of PET fines, using laboratory tests such as FTIR, DSC, MFI, moisture content, tensile tests and bending tests. Preliminary results allow foreseeing the successful direct incorporation of PET fines into PET recycling.
- Ink Removal on Plastic Films Printed by FlexographyPublication . Bozzola, Fernando; Nascimento, Bruna Guilherme do; Vasco, Joel C.; Silva, Nelson; Lagoa, Fernando; Capela, Carlos; Heleno, Lizete; Gaspar, Marcelo; Oliveira, Nelson S.Plastics are key engineering materials for our society and economy, mainly due to their multifunctionality and ease of processing. Nonetheless, their main drawback is related to the fact that when these cannot be reprocessed, they do generate waste, which leads to several environmental impacts. Therefore, considering plastics’ circularity, minimizing their waste, and the resulting impacts, stresses the need for these to be recyclable. One of the main challenges that concern their recyclability is the deinking of plastic films when printed by flexography. The current technology uses non-bio-based surfactants and non-renewable surfactants, which are harmful to the environment. Therefore, the main objective of current research is to develop an environmentally sustainable process for ink removal on printed post-industrial flexible plastic films using bio-based surfactants. This process focuses on obtaining a deinked plastic that may be reprinted, avoiding this way for inappropriate disposal or reprocessing problems. The value increase of upcycling such post-industrial waste makes it possible to match the quality of the virgin plastic, which is key to carrying out an effective cost analysis of recycled plastic when compared to the new plastic films. Dedicated laboratory deinking procedures were undertaken with transparent polyethylene films printed by flexography with different conditions. Preliminary results show the dedicated experimental ink removal procedure using bio-based surfactants to be effective and environmentally sustainable.
- Production and Material Types for Pallets: A ReviewPublication . Pulgar, Alejandro; Oliveira, Nelson S.Pallets are used extensively in the supply chain for the transportation of goods between suppliers, manufacturers, distributors, and retailers. This article reviews pallet production, its mechanical properties related to material options (according to European standards and industrial applications) and management systems. In the global supply chain, polymer, metal, and composites pallets compete in line with the concept of sustainable development. The supply chain requires pallets according to specific characteristics, such as sizing, maximum load capacity, durability (lifespan), cost and more information is needed about their environmental impacts. Some types of pallets (stringer and blocks) can have several configurations, number, width and spacing. Furthermore, the pallets management system is divided in three models; EMP (extensive management of pallets), TPO (transfer pallet’s ownership) and PR (pallet rent), where suppliers, distributors and retailers select the most suitable option. The systematic review of the literature identified 15 documents with the key methodological elements, such as, specifications, inventory data, goals, and system boundaries for a life cycle assessment of pallets.
- Sustainability Assessment of Building Rehabilitation Solutions: The Mid 70s Portuguese BuildingPublication . Reis, Alexandre; Heleno, Lizete; Monteiro, Silvia; Oliveira, Nelson S.The Energy Performance of Buildings Directive (EPBD) establishes improvements to buildings’ comfort conditions and energy performance, bringing them closer to buildings with almost zero energy needs, namely the Nearly Zero Energy Building (NZEBs). The assessment tools for sustainable construction, more recognized internationally, are LEED and BREEAM, and in Portugal is the LiderA. The application of those tools promotes energy efficiency and decarbonization of buildings, as referred to in the Portuguese Long-Term Strategy for Building Renovation (LTRS-PT) until 2050. In this case, a house representative of the construction of the period between 1971 and 1980 in Portugal was chosen to evaluate environmental sustainability using LiderA. In the current conditions, the LiderA rating class of the house was D. To improve the performance of the building were identified balanced rehabilitation solutions without excessive automation. The presented solutions should avoid transforming the house into a complicated device with operational difficulties or specialized operation. In this way, the proposed interventions in the building and systems are based on renewable sources, prioritizing energy and water efficiency. Furthermore, as a contribution to the health and well-being of the occupants, we considered measures related to indoor air quality (IAQ) and noise minimization. In addition, the encouragement of native species has contributed to ecological enhancement. With that proposals, the house rating class using LiderA improved from class D to class A+.
- Sustainability Performance of Buildings in the Project Stage—Residence StudentsPublication . Heleno, Lizete; Baptista, Pedro; Marta Gregório; Oliveira, Nelson S.; Monteiro, SilviaIn recent years, the concept of sustainable construction has been promoted by demand and by regulations. Several methodologies to assess the sustainability of the construction have been spread across the world, by several countries for almost all continents. This study focuses on the most used construction sustainability assessment methodologies, which were compared with the Portuguese methodology, LiderA. It was found that the LiderA is the sustainability system with the greatest number of relevant criteria, considering the three dimensions of sustainability, environment, economy and social. Considering the 5 phases of the construction life cycle, the importance to apply these methodologies in construction is crucial in the early phases. It can help to draft the sustainability classification of the building. To apply the LiderA was used a residence of students, a building composed of apartments, in the phase of planning. All of the 40 criteria from the LiderA were classified from F to A++, according to the project of the residence of students. The final classification, as it was projected, was A, meaning that the building has an environmental performance 50% higher than usual practice. The category of criteria with the highest contribution was the category of quality of service and resilience, with a percentage of achievement greater than 50%. The local dynamics and the resources category were the categories with the lowest contribution, and they have the potential to be reevaluated by the building promoter, since it has the potential to improve the sustainability classification of the residence of students.