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- Assisted hydrothermal carbonization of agroindustrial byproducts as effective step in the production of activated carbon catalysts for wet peroxide oxidation of micro-pollutantsPublication . Díaz de Tuesta, Jose Luis; Saviotti, Marcus Chamahum; Roman, Fernanda; Pantuzza, Gabriel F.; Sartori, Hiram J.F.; Shinibekova, Assem A.; Kalmakhanova, Marzhan; Massalimova, Bakytgul Kabykenovna; Pietrobelli, Juliana Martins Teixeira; Lenzi, Giane G.; Gomes, HelderThis work deals with the valorisation of bagasse of sugarcane – BC, bagasse of malt – BM and seed of chia – SC, through its transformation into pyrochars, hydrochars and activated carbons (ACs) by pyrolysis, hydrothermal carbonization (HTC) and sequential HTC and pyrolysis, respectively. The HTC process was carried out in the presence of H2O, FeCl3 and H2SO4 solutions. The materials resulting by HTC in the presence of FeCl3 revealed the highest burn-off, but the contents of carbon released into the liquid phase, measured as total organic carbon, and to the gaseous phase, determined by carbon balance, depend strongly on the carbon precursor. In this sense, BC generates more volatile organic compounds (up to 34% of the initial carbon content), followed by BM (< 15%) and SC (< 5%) in their HTC and pyrolysis (70%). The pyrochars, hydrochars and ACs prepared from BC also show the highest specific surface areas (SBET < 447 m2⋅g-1) when compared to the specific surface areas of the materials prepared from BM and SC. The carbon-based materials prepared with FeCl3 show the highest catalytic activity, but iron leaching into solution is observed. On the other hand, the materials prepared with H2SO4 show high activity, enabling its application in successive cycles and the complete degradation of caffeine in concentrations ranging from 1 to 100 mg⋅L-1, after 5–60 min of reaction.
- Selective oxidation of 4-nitrophenol with H2O2 in a biphasic system by janus-like carbon nanotubesPublication . Sanches, Flávia Kim; Roman, Fernanda; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Silva, Adrián; Faria, Joaquim; Machado, Bruno; Serp, Philippe; Marin, Pricila; Gomes, HelderThe use of petroleum-based products has increased drastically with the increase in population, resulting in the deposition of oily products in aquatic systems. It is estimated that for each ton of petroleum that undergoes refinement processes, between 0.5 and 1 ton of oily wastewaters are generated, bearing an oil concentration that may reach 40 g L-1 [1,2]. Hazardous pollutants dissolved both in oily and aqueous phases may also be found in those oily wastewaters [3], hindering their treatment through conventional processes. Furthermore, the oil phase is, in some cases, an added-value product, and its degradation results in economic losses. Thus, the development of processes that allow the removal of hazardous contaminants from oily and aqueous phases, providing an opportunity for recovering both phases, should be advantageous [3]. This work deals with the selective removal of a hazardous compound (4-nitrophenol, 4-NP) from a simulated oily wastewater (2,2,4-trimethylpentane:water = 10:90 v/v) by an oxidative process considering H2O2 as oxidant and amphiphilic Janus-like carbon nanotubes as catalysts. Amphiphilic catalysts were selected since they should present advantages in this process due to their ability to interact with both aqueous and oily compounds and phases [4]
- Remoção de metais pesados em lixiviados para uso como fertilizantesPublication . Cardoso, Jonathan; Fernández-Delgado, Marina; Vertonha, Maria Thais; Cabral, David; Silva, Adriano S.; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Arrobas, Margarida; Brito, Paulo; Gomes, HelderThe aim of this work is to offer a sequence of processes to convert leachate liquid stream with a highly variable composition, collected from the composting line of a mechanical and biological treatment facility, into commercial fertilizers, which fit the composition requirements of the European Legislation. The leachate was first characterized by total organic carbon (TOC), density, fixed and volatile solids, nutrients as organic and ammoniacal nitrogen, phosphorus, potassium, and heavy metals content, to verify the accordance with the European Legislation for fertilizers. The preliminary characterization showed that the leachate contains low levels of organic and ammoniacal nitrogen and phosphorus but high contents of potassium and TOC, which are interesting to fertilizing purposes, and chromium, which needs to be removed to fit the specifications. To chromium removal, some adsorbents materials were proposed: activated carbon produced from the compost of the referred company and acid activated clays obtained from a partnership with a Kazakhstan institution. The results after the adsorption process showed an interaction between the adsorbents and TOC, which was not intended, and a reduction in the heavy metals content, more efficient for Pb, Cd, Zn and Cu, but less for Cr removal. For future work, the study of the use of ionic resins was proposed through the development of an experimental design, in order to obtain the optimized parameters for the minimization of TOC loss, and promotion of heavy metals removal, especially chromium, using a response surface methodology.
- Biodiesel production through esterification using ionic liquids as catalystsPublication . Tadevosyan, Arevik; Roman, Fernanda; Queiroz, Ana; Ribeiro, António E.; Brito, PauloThere is a growing interest in the development of alternative technologies to the oil economy, based on renewable energy sources. A possible solution is a biofuel usable in compression-ignition engines, produced from biomass rich in fats and oils. Biodiesel is an alternative fuel that can be produced from a wide range of raw materials such as vegetable oils and animal fats. Yet, the use of sources that do not compete with the food market, like waste cooking oils - which usually feature high levels of free fatty acids (FFA’s) -, can lead to problems in the process of biodiesel production through alkaline transesterification. Ionic liquids (ILs) could be employed in the biodiesel production to partially overcome these problems; since they are able to catalyze the esterification reaction of FFA’s to biodiesel. In this work, experimental results will be presented concerning the study of the influence of ILs in the catalysis of esterification reactions of organic acids to the corresponding methyl esters. Different imidazolium-based ILs were tested for biodiesel production through an esterification reaction of oleic acid, using a previously optimized reaction methodology [1]: 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM][HSO4]), 1-butyl-3-methylimidazolium methanesulfonate, 1-butyl-3-methylimidazolium methyl sulfate, 1-metylimidazolium hydrogen sulfate ([HMIM][HSO4]) and tributylmethylammonium methylsulfate. The experimental values obtained for the conversion of the oleic acid through an esterification reaction showed that the ionic liquid ([BMIM][HSO4]) would be one of the most promising catalysts. The recovery of the selected [BMIM][HSO4] ionic liquid was studied for different catalyst loading: 10, 15 and 20 wt% - relative to the mass of oleic acid. The reaction yield was determined by acidity using a titrimetric method (EN 14104). The composition characterization of the biodiesel samples (identification of fatty acid methyl esters) was evaluated by gas chromatography with FID detector (EN 14103). The obtained results confirm that it is possible to reuse [BMIM][HSO4] ionic liquid in successive reactions without great loss of yield and, thereafter, to significantly reduce the costs associated with the use of ILs as catalysts. Moreover, the esterification reaction with the [HMIM][HSO4] IL was also studied and further comparison of the methyl esters content obtained with each catalyst will be possible.
- Polyolefin-derived carbon nanotubes as magnetic catalysts for wet peroxide oxidation of paracetamol in aqueous solutionsPublication . Díaz de Tuesta, Jose Luis; Silva, Adriano S.; Roman, Fernanda; Sanches, Lucas Fenato; Silva, Fernando Alves; Pereira, Ana I.; Silva, Adrián; Faria, Joaquim; Gomes, HelderThis work deals with developing feasible valorization technologies to prepare carbon nanotubes (CNTs) from plastic solid waste and demonstrate their application in catalytic wet peroxide oxidation (CWPO). CNTs were synthesized by catalytic chemical vapor deposition (CCVD) at 850 oC, considering low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) as carbon precursors representative of urban plastic solid waste. Iron oxide nanoparticles supported in alumina, previously synthesized by sol-gel, were used as catalysts in the CCVD process. TEM micrographs allow us to determine 41 nm as the average outer diameter of the CNTs and to visualize magnetic iron nanoparticles (ca. 10 nm) embedded inside the CNTs (ca. 6.4 % of content measured as ashes). These magnetic nanoparticles were kept in the CNT structure even after the puri-fication of the CNTs with sulphuric acid, allowing to obtain magnetic CNTs. All purified and non-purified CNTs prepared from the polyolefins were assessed as catalysts in CWPO of paracetamol (PCM), used as a model pharmaceutical contaminant in water at CPCM,0 = 100 mu g mL-1 (CH2O2,0 = 472 mu g mL-1, CCNT = 2.5 g L-1, pH0 = 3.5 and T = 80 degrees C). The concentrations of PCM, H2O2, aromatic and total phenolic compounds were monitored for 24 h. All CNTs showed catalytic activity, allowing the complete degradation of PCM at 6 h of reaction time. The stability and reusability of materials are tested and proved in CWPO.
- Kinetic modelling of the hydrothermal carbonization of compost derived from municipal solid wastePublication . Roman, Fernanda; Díaz de Tuesta, Jose Luis; Praça, Paulo; Silva, Adrián; Faria, Joaquim; Gomes, HelderNowadays, municipal solid waste (MSW) management commonly includes a mechanical and biological treatment process (MBT). The solid stream from the anaerobic digestion of the organic fraction can be processed to obtain a compost, which can be used as fertilizer. However, compost production is higher than the existing demand, and the expected developments on up-coming directives ruling “End-of-waste” criteria are leading to barriers on the use of MSW-derived fertilizers [1]. Thus, the development of new alternatives for the treatment of organic wastes and compost valorization are necessary. This work deals with the valorization of compost from MBT, through the production of catalysts by Hydrothermal Carbonization (HTC) [2]. HTC of the compost was carried out in a Teflon vessel inserted in a stainless-steel body at different operating conditions (150-230 ºC,1-5 h, 1-4 g of compost, 30 mL). A Doehlert Matrix was considered to plan the experiments. The carbon balance and the kinetic equations were evaluated from experimental data reporting the carbon content in the liquid (estimated by TOC analysis) and solid phases (estimated by elemental analysis). A lumped kinetic model based on the elemental carbon content is proposed (Fig. 1), anticipating that the compost (C) undergoes reactions that originate liquid intermediates (L), reaction 1, and sequentially results in hydrochar (HC) and gases (G), reactions 2 and 3, respectively. In addition, it was assumed that HC and G were also produced from the compost directly, reactions 4 and 5, respectively. The highest kinetic constant at 190 ºC (8.3·10-4 min-1) was found for the formation of the liquid soluble intermediates from compost (reaction 1), whereas the production of hydrochar from the liquid intermediates (reaction 2) shows the lowest kinetic constant (3.1·10-4 min-1). The lowest activation energy was estimated for reaction 1 (23 kJ·mol-1), while reactions 2 and 4, related to the formation of hydrochar, resulted in the highest values (85 and 195 kJ·mol-1, respectively), meaning that the production of hydrochar strongly depends on the temperature.
- Optimization and kinetic study of esterification reaction of oleic acid using [HMIM]HSO4 as catalystPublication . Brito, Paulo; Roman, Fernanda; Queiroz, Ana; Ribeiro, António E.Biodiesel is a promising fuel, since its similarity to petrodiesel allows the application in regular diesel engines without major changes, while still promoting a reduction in environmental impacts caused by fossil diesel. Meanwhile, the employment of high quality feedstock, for instance the usual edible oils, has disadvantages, such as competition with the food market. The replacement of those oils by waste cooking oils (WCO) brings major advantages, amongst them, the reduction of the costs associated to the feedstock and the value added to a material usually considered as waste. The current work, proposes an optimization study using a Response Surface Methodology (RSM), focusing on two responses: (i) the conversion of oleic acid (OA), used as a model compound to simulate the FFAs present in the WCO, estimated on the acid value drop between initial OA and the biodiesel samples produced, determined according to EN 14104 and (ii) the FAME content, measured according to EN 14103. The chosen design was Box-Behnken Design (BBD), with 4 variables (time, temperature, molar ratio methanol/oleic acid, and catalyst dosage) and 3 levels, leading to 27 experimental runs. The optimization was followed by a kinetics study, where time, molar ratio and catalyst dosage remained constant and set to optimal conditions, and the temperature was varied from 70 to 110°C. The acid value of the samples collected throughout the reaction was measured, and the conversion was calculated, allowing the establishment of the reaction evolution with time, which was used to predict the respective activation energy and the pre-exponential factor, according to Arrhenius theory.
- Catalytic wet peroxide oxidation of paracetamol using carbon nanotubes synthesized from low-density polyethylene as model plastic wastePublication . Roman, Fernanda; Lopes, Jéssica Paula Marim; Silva, Ana P. F.; Díaz de Tuesta, Jose Luis; Lenzi, Giane G.; Silva, Adrián; Gomes, HelderOne of the ongoing concerns related with wastewater treatment is the presence of micropollutants on water bodies, since they accumulate due to its recalcitrant behavior and its constant introduction in the system [1]. Catalytic Wet Peroxide Oxidation (CWPO) is a wastewater treatment technology based on the generation of powerful oxidants (hydroxyl radicals) from the decomposition of H2O2, providing that suitable solid catalysts are used, with promising results being reported in the removal of pharmaceuticals [2]. On the other hand, plastic waste is an actual concern in waste management, and alternatives to its post-use should be sought [3]. This study aims at the CWPO of paracetamol (PCM) as model micropollutant, using as catalysts carbon nanotubes (CNTs) synthesized from low-density polyethylene, as representative polymer found in municipal plastic solid waste streams. The CNTs were synthesized by chemical vapor deposition at 800 ºC, considering three catalyst based on Ni, Fe and Al prepared by coprecipitation and wet impregnation methods. The synthesized CNTs were further tested on the CWPO of PCM (100 mg L-1 of PCM, pH0 3.5, 474 mg L-1 H2O2, Ccatalyst = 2.5 g L-1 and 80 °C). All catalysts tested led to the complete conversion of both PCM and H2O2 after 24 h of reaction time (Figure 1(a,b)), with a contribution of 23-42% of adsorption according to pure adsorption tests performed at the same operating conditions (Figure 1(d)). The CNT synthesized on the catalyst prepared by the impregnation method shows a lower contribution of adsorption and led to a mineralization of 70% after 24 h of reaction time, with the highest efficiency of H2O2 consumption (determined as TOC conversion divided by H2O2 conversion).
- 3D tuned porous carbon monolith as catalysts in the wet peroxide oxidation of paracetamolPublication . Roman, Fernanda; Steldinger, Hendryk; Díaz de Tuesta, Jose Luis; Henrique, Adriano; Silva, José A.C.; Gläsel, Jan; Etzold, Bastian J.M.; Gomes, HelderIn recent years, many pharmaceuticals have been identified at trace levels worldwide in the aquatic environment [1]. Municipal wastewater treatment plants (WWTPs) are considered the main sources of these pollutants as they are not generally prepared to deal with such complex substances and thus, they are usually ineffective in their removal [1]. Despite the low concentration of drugs contained in those effluents, the presence of pharmaceuticals, even in trace concentrations, affects the quality of water and constitutes a risk of toxicity for the ecosystems and living organisms [1-2]. Consequently, new regulation for micropollutants discharge and monitoring has been issued in Europe (Directive 2013/39/EU). Paracetamol (PCM) deserves particular attention, since it has recently been discovered as a potential pollutant of waters, largely accumulated in the aquatic environment [3]. This work deals with the treatment of PCM, used as a model pharmaceutical contaminant of emerging concern, by catalytic wet peroxide oxidation using carbon-based monoliths (Fig. 1a) as catalysts. Monoliths were prepared by stereolithographic 3D printing of a photoresin, which was later converted into porous carbon by oxidation in air (300 °C, 6 h) and subsequent pyrolysis in N2 (900 °C, 15 min) as described elsewhere [4]. The materials revealed catalytic activity in the CWPO of PCM allowing to reach PCM conversions up to 30% with a residence time of 3.5 min (Fig. 1b).
- Valorization of compost obtained from the mechanical and biological treatment of municipal solid waste: catalysts for wet peroxide oxidation of landfill leachatesPublication . Freitas, Gabriel; Roman, Fernanda; Díaz de Tuesta, Jose Luis; Mambrini, Raquel Vieira; Gomes, HelderSince humanity started living in communities and towns, the generation of solid waste has largely increased and, in 2017, each European citizen generated 480 kg of municipal solid waste (MSW). The main concern with MSW is its management and final destination since in many cases MSW is just thrown in landfills. In mechanical and biological plants, MSW is first sorted into discarded, recyclable, and organic waste streams. This organic fraction goes to the biological treatment stage, generating biogas, and as by-products, leachate, and compost are obtained, the compost being mainly used as an agriculture fertilizer. However, the amount of compost produced is higher than its demand, resulting in an excess that is currently accumulated in landfills. This work deals with the valorization of compost to produce hydrochairs, and pyrochars, through hydrothermal carbonization (HTC) and pyrolysis, respectively, with suitable properties as catalysts for the catalytic wet peroxide oxidation of the landfill leachate. Up to seven catalysts were synthesized under several conditions, 2 from HTC and 5 from pyrolysis. The catalysts were characterized to determine the ash content and elemental analysis. All materials were assessed in the degradation of H 2 O 2 , leading to its complete degradation after 2 h of reaction time. Some selected catalysts were further tested in the CWPO of the landfill leachate (TOC = 27 g L -1 , COD = 60 g L -1 , 38.8 mS/cm, and 5 g L -1 of chloride ions) under the following operating conditions: C Catalyst = 1.8 g L -1 ; T = 80 ºC; C H2O2 = 85.7 g L -1 and pH from 3.0 to 7.3.