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- Biodiesel production from residual cooking oils and its purification by adsorption processes based on adsorbents of natural originPublication . Garção, Maria Isabella Lima; Gomes, Maria Carolina Sérgi; Queiroz, Ana; Ribeiro, António E.; Brito, PauloTotal global energy consumption has increased significantly in recent decades, and nowadays the main sources of world energy are oil, coal and natural gas. In addition to environmental concerns, the limited availability of fossil fuels has increased the interest in exploring alternative energy sources. In this quest, biofuel is a promising renewable energy source with low carbon emissions, also, it can be produced from a variety of resources, including waste cooking oil (WCO). Biodiesel is renewable, biodegradable, non-toxic, sulfur-free and free of aromatic carcinogens
- Purification of biodiesel using a natural based adsorbent in a packed-bed columnPublication . Smolich, Camilla Groxko; Guimarães, Miriam D.; Fabian, João Vitor; Gomes, Maria Carolina Sérgi; Queiroz, Ana; Brito, Paulo; Ribeiro, António E.In Europe, the Renewable Energy Directiva stimulates the development of renewable energy sources to reduce greenhouse gas emissions by at least 55% by the year 2030 and to become aclimate-neutral continent by 2050 [1]. Biodiesel presents advantages over diesel fuel in terms of sulfur content, biodegradability, flash point, no aromatic content, higher cetane number and miscibility in petroleum diesel in any ratio [2]. The most used feedstock is high quality vegetable oil, but the use of waste cooking oil adds to the global reduction of residue, lower costs, and competes less for vegetable oils against the food industry [3]. This biofuel is obtained through transesterification, and glycerol is formed as a coproduct. lts presence can cause damage to motors so it must be removed until its final concentration is lower than 0.02wt%. The most used method is wet washing, but the downside is the great amount of water used and long periods of time are needed to separate biodiesel from its contaminants through decantation [4]. A promising altemative is dry washing method through adsorption using biomass activated carbon. For a more practica! application, packed columns are frequently used in large scale adsorption processes. lt is one of the most efficient configurations for treating great volumes of effluent and adsorption-desorption cycles [5]. For this study, crude biodiesel was produced through transesterification from a waste cooking oil sample, using ethanol and a basic catalyst (NaOH). Afterwards the biodiesel produced was characterized in terms of glycerol content. In parallel, activated carbon materials were obtained from olive pits by physical activation at 800°C. The adsorbent materials performance for glycerol removal from crude biodiesel is assessed using a continuous system based on a packed-bed column according to the following parameters: fluid rate, removal capacity, pressure drop and adsorbent recovery.
- Production and characterization of different green adsorbents for the removal of free glycerine in the biodiesel purification processPublication . Guimarães, Miriam Domingues; De Prá, Marina Celant; Queiroz, Ana; Ribeiro, António E.; Brito, PauloThere is environmental concern due to the high use of oil as a primary fuel, which results in a significant emission of polluting gases, and one of the most promising solutions involves replacing it with biodiesel. Biodiesel is a fuel that can be produced using waste cooking oil (WCO) and has become an excellent alternative to ordinary diesel. A crucial stage in the production of biodiesel is the purification process. Among the various methods used, there are two main ones: the wet purification method, which uses water, and the dry purification method, which uses ion exchange resins or adsorbents. Dry purification using adsorbents removes contaminants such as water, soap, and traces of glycerine based on their chemical polarities and acidic and basic properties. Also, it avoids the generation of high volumes of effluents, and the adsorbents can be reused [1][2].
- Biodiesel production from waste cooking oils catalysed by ionic liquid [BMIM][HSO4]Publication . Almeida, Fretson Micaela; Queiroz, Ana; Ribeiro, António E.; Brito, PauloThe environmental and energy problems related to the burning of fuels from fossil resources, i.e. nonrenewable fuels such as oil, natural gas or coal, leading to an increased concern about global warming, have directed the scientific community to seek sustainable and renewable energy alternatives. In this context, biofuels have emerged as a promising way to replace non-renewable fuels, including biodiesel [1]. Biodiesel is defined as a mix of monoalkyl esters of long fatty acid chains (FAMEs), and can be obtained by converting vegetable oils or animal fats through transesterification or esterification reactions. Due to its advantages, such as biodegradability, low viscosity, high flash point and low environmental impacts, it has potential to be used directly in diesel engines without any modification [2]. The raw materials used in biodiesel production can be divided into edible and inedible. However, the high cost of edible oils, which correspond to about 70% of the total value of production, as well as competition with the food market and soil degradation due to large planting scales, are disadvantages for the production and commercialization of biodiesel [3]. Inedible materials such as Waste Cooking Oils (WCOs) can also be used. The reuse of WCOs is a sustainable and environmentally friendly solution, preventing millions of tons of this raw material from being dumped into sanitation systems giving rise to serious problems in wastewater treatment. Still, one of the disadvantages of using WCOs is its high Free Fatty Acid (FFA) content that leads to saponification reactions [2]. Homogeneous alkaline catalysts are the most used in the biodiesel production industry. Compared to homogeneous acid catalysts, they have many advantages, such as high productivity, low price, allow high reaction speed, shorter reaction time, low alcohol molar ratio:oil and lower corrosiveness. However, catalysis is mainly affected by the presence of free fatty acids, leading to decreased reaction yields. In addition, when using these conventional catalysts, a high amount of clean water is used during the purification process, resulting in high flows of waste water, which is deposited in rivers, lakes, seas, contaminating the environment. To solve this problem, the possibility arises of using new catalysts, such as ionic liquids (ILs), which allow high reaction yields, and can be recovered and reused, making them greener and more economical
- Removal of naproxen from water using adsorbents obtained from low-cost materialsPublication . Milani, Eduardo C.; Reis, Vinícius de Assis; Brito, Paulo; Queiroz, Ana; Ribeiro, António E.The continuous growth of world population together with the strong urbanization has triggered an increasing demand for freshwater which has resulted in a serious deterioration of water bodies1. Water pollution with pharmaceutical drugs is becoming a relevant problem. The concentration of nonsteroidal anti-inflammatory drugs, estrogens, personal care products, among others, in waterways is reaching hazardous levels, posing a threat to the environment and human health. Moreover, conventional cleaning and degradation processes applied on wastewater treatment plants are inefficient to eliminate or remove these compounds. Adsorption is a treatment process considered as effective process used to remove micropollutants such as pharmaceutical drugs from wastewaters2,3. This work will present the main experimental results obtained for the removal of naproxen, a representative anti-inflammatory drug, from water by adsorption using activated carbon obtained from olive stone. From the raw material, four different types of activated carbon adsorbent were prepared and characterized. The equilibrium adsorption isotherms were measured using the batch method. The most significant adsorption parameters were optimized, such as the solution pH, mass of the adsorbent, contact time and temperature. The physicochemical characterization of the pyrolyzed material shows a considerable superficial area of 608 m2/g when compared with other natural biomass-based materials. The adsorbent with the better performance allowed, using a contact time of 24 hr and a solution pH of 4.5, a removal efficiency of 100%. The Langmuir model was used to better described the adsorption behavior with the highest maximum adsorption capacity value of 35.2 mg naproxen/g adsorbent. The kinetics of the adsorption is well described by a pseudo-second order model.
- Biomass-based residues valorization for the removal of sertraline from waters by adsorptionPublication . Ribeiro, António E.; Belgacem, Mohamed Ben; Queiroz, Ana; Brito, PauloPharmaceutical drug reach the environment through several anthropogenic sources being scattered and accumulated
- Removal of estrogens from water using activated carbon from olive stonePublication . Milani, Eduardo C.; Menezes, Maraísa L.; Díaz de Tuesta, Jose Luis; Ribeiro, António E.; Brito, Paulo; Queiroz, AnaMicropollutants are substances that are continuously released to environments and can present adverse effects to the environment, even when present at very low concentrations (trace levels). Among these compounds are the estrogens pharmaceutical drugs, since traditional sewage and drinking water treatment plants are not able to remove or degrade them1,2. Thus, new and more efficient treatments are required, such advanced oxidation processes or adsorption. Activated carbons (ACs) are known as low-cost carbonaceous materials used for removal of pollutants using adsorption processes3,4. This work aims to produce ACs from olive stone and to evaluate the simultaneous removal of four different estrogens by adsorption with the produced materials. From the olive stone by product generated in the olive oil extraction, five different materials were produced, namely (i) powdered olive stone, (ii) physical activated at 800°C (iii) carbonized at 500°C, (iv) chemical activated using phosphoric acid and (v) chemical activated with sodium hydroxide. The carbonization yield was calculated and the pH at point of zero charge (pHPZC) of the carbonaceous materials determined. The simultaneous quantification of estriol, estrone, 17 -estradiol and 17 - ethinylestradiol in aqueous solution was performed by high performance liquid chromatography with diode array detector (HPLC-DAD). The highest carbonization yield (57.5%) was observed using acid activation. The adsorbents production method also influences the pHPZC of the adsorbents, being more expressive by the acid activation with the lowest pHPZC (3.84). The olive stone raw-material shows an important potential to be used on the production of activated carbons with high carbonization yields
- Produção de biodiesel através de esterificação catalisada por líquidos iónicosPublication . Brito, Stefano; Neves, Verónica; Ribeiro, António E.; Brito, Paulo; Queiroz, AnaA contribuição dos combustíveis fósseis para o aumento da poluição ambiental, nomeadamente no que diz respeito à emissão de gases com efeito de estufa, o constante aumento dos preços do petróleo e a limitação das reservas destes combustíveis, têm incentivado a investigação de fontes alternativas de energia. No setor dos transportes, os biocombustíveis são uma das respostas ao problema energético e ambiental. O biodiesel, constituído por uma mistura de ésteres metílicos de ácidos gordos (FAME), é utilizado como substituto do diesel convencional, constituindo uma forma de independência para os países que não possuem reservas de petróleo, podendo ser produzido a partir de matérias-primas variadas, como óleos vegetais, gorduras animais, óleos alimentares usados e algas. Neste trabalho estuda-se a utilização de novos catalisadores, nomeadamente os Líquidos Iónicos (LI), como alternativa aos catalisadores tradicionais no processo de esterificação de ácidos gordos livres. A influência da utilização dos LI no processo de esterificação é estudada através da monitorização das propriedades do biodiesel produzido, pela determinação do índice de acidez por titulação ácido-base, e do teor de FAME através de cromatografia gasosa (GC-FID). Apresentam-se resultados experimentais obtidos com Metanossulfonato de 1-butil-3-metilimidazólio ([BMIM][CH3SO3]) e Cloreto de 1-butil-3-metilimidazólio ([BMIM][Cl]), modificados por incorporação de cloreto férrico, e utilizando diferentes proporções ácido oleico(AO)/metanol(M), 1/5, 1/10 e 1/15. Para ambos os LI estudados, verifica-se um aumento do rendimento da reação com o aumento da razão AO/M. Os valores dos rendimentos obtidos, variam entre 86.6% e 94.4% para o [BMIM][Cl] e entre 87.2% e 98.8% para o [BMIM][CH3SO3].
- Determination of sertraline antidepressant drug in aqueous effluents by SPE/HPLC-DADPublication . Machado, Verónica; Queiroz, Ana; Brito, Paulo; Ribeiro, António E.The presence of pharmaceutical drugs, their metabolites and degradation products in the environment requires research and moonotoring studies to assess the potential risks to human health and to the ecosystem
- Acid leaching of alloys within the quaternary system Fe-Si-Ca-AlPublication . Margarido, Fernanda; Figueiredo, Maria Ondina; Queiroz, Ana; Martins, João Pedro de AlmeidaSilicon with high purity and fine particle size can be produced by acid leaching of Fe-Si industrial alloys under the condition that they have adequate chemical composition and structural constitution. Such alloys contain phases that fall within the system Fe-Si-Ca-Al, where the quaternary phase Caalsifer, with aproximate formula (Fe0.8Al0.1 0.1) (Si0.8Ca0.2)2, is found along with several binary and ternary phases (Fe-Si, Ca-Si, Al-Fe-Si, Ca-Al-Si). With the purpose of optimizing the phase, constitution alloys were synthesized within the system Fe-Si-Ca-Al. The results of leaching experiments performed using HCl (150 and 220g/L) at constant temperature (T=102 1 C) and ordinary atmosphere indicate that the Caalsifer plus Al-Fe-Si phases should be maximized whereas the FeSi2 phases should be minimized, by controlling Al/Ca and Fe/Si concentration ratios in the synthesis process.