PPGEQ - Doutorado em Engenharia Química

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Cultivo de microalgas para biofixação de CO2: uma estratégia para captura e conversão de carbono em biocombustíveis e/ou bioprodutos
(Universidade Federal do Rio Grande do Norte, 2025-01-14) Calixto, Guilherme Quintela; Braga, Renata Martins; Melo, Marcus Antonio de Freitas; http://lattes.cnpq.br/2750389852125881; Oliveira, Karine Fonseca Soares de; Sassi, Cristiane Francisca da Costa; Melo, Vítor Rodrigo de Melo e
The increasing atmospheric CO₂ concentrations due to human activities have led to the search for alternative CO₂ capture sources, including microorganisms such as microalgae. Studies have shown the effect of carbon dioxide concentration on microalgae growth, even when using residual CO₂ from industries such as cement production, which accounts for more than 6% of global CO₂ emissions. The objective of this study is to evaluate the effect of different CO₂ concentrations on the cultivation of two microalgae strains: Chlorella sp and Spirulina platensis, in order to identify their CO₂ biofixation capacity, potential high-value bioproducts, and system scalability. The microalgae were cultivated in commercial culture media – BG11 (Adapted) for Chlorella and Zarrouk (Adapted) for Spirulina – under different CO₂ concentrations (v/v) (0.04%, 5%, 10%, and 15%). The microalgae were characterized through proximate analysis (ash content, moisture, volatiles, and fixed carbon), elemental analysis (CHNO), thermogravimetric analysis (TGA), X-ray fluorescence (XRF) of the ashes, lipid content, protein content, and both conventional and catalytic analytical pyrolysis. Additionally, during cultivation, daily data on dry biomass and pH were collected. The results indicate that both microalgae achieved the highest biomass yield at 10% CO₂ (v/v), reaching 1.25 g L⁻¹ for Chlorella and 2.15 g L⁻¹ for Spirulina. Despite the high ash content due to the flocculation method, Chlorella exhibited greater potential for biofuel production due to its high lipid content (21.7%) compared to Spirulina (11.2%). Conventional pyrolysis revealed a high amount of oxygenated (>25%) and nitrogenated (>20%) compounds for both microalgae, which were predominantly converted (>90%) into aromatic compounds and hydrocarbons after the use of the HZSM-5 catalyst in the thermochemical conversion process. The system scalability analysis for photobioreactors (80 L) demonstrated economic feasibility when supplemented with an external CO₂ source, making it possible to achieve a self-sufficient system considering only the raw microalgae sale price. This approach can significantly contribute to CO₂ emissions mitigation and the development of a renewable carbon-based economy.
Hidrogenação livre de solvente do ácido succínico e da butirolactona: uma abordagem sustentável para obtenção de produtos de alto valor agregado
(Universidade Federal do Rio Grande do Norte, 2025-04-10) Costa, Carolina da Silva; Courtial, Camila Gambini Pereira; Gomes, Pedro Miguel Vidinha; http://lattes.cnpq.br/1692213009194423; https://orcid.org/0000-0003-2472-9755; http://lattes.cnpq.br/8055289812908100; http://lattes.cnpq.br/3839012933524596; Nunes, Andréa Oliveira; http://lattes.cnpq.br/7620659413250570; Carvalho, Fabíola Correia de; https://orcid.org/0000-0001-6101-2441; http://lattes.cnpq.br/4759287276606267; Oliveira, Paulo Filho Marques de; Braga, Renata Martins
γ-butyrolactone (GBL) and succinic acid (SUC) are platform molecules widely used in the production of high-value compounds. For this reason, the present study aimed to evaluate the hydrogenation of these compounds in sustainable, solvent-free media, employing supercritical carbon dioxide (scCO₂) conditions, with the use of both micro and macroscale (pellet) catalytic forms of PdRe/SiO₂. The study was divided into three articles. The first article primarily aimed to evaluate the effect of solvent-free reactions with the addition of scCO₂ as a reaction medium in the hydrogenation of GBL in batch processes. These same conditions were tested for the hydrogenation of SUC in batch, including an evaluation of the effects of temperature, H₂ pressure, catalyst mass, and the Re content in the catalyst. The third article focused on the development of technical catalysts in the form of PdRe/SiO₂ pellets for the study of solvent-free hydrogenation of GBL in continuous-flow systems. For this purpose, pellets with different thermal treatments (uncalcined and calcined at 300 and 500 °C) were evaluated and compared with powdered catalysts in batch systems. In fixed-bed reactors, the effects of temperature, pressure, GBL and H₂ flow rates, and bed height were assessed. The results demonstrated that the reaction medium had a significant impact on the selectivity of GBL hydrogenation, acting as a modulating factor for selectivity. Under solvent-free conditions, 93% selectivity for tetrahydrofuran (THF) was achieved. With the addition of scCO₂ (80 bar), selectivity was completely shifted to 1,4-butanediol (BDO), reaching 100%. For SUC, the most severe conditions of temperature (280 °C), pressure (90 bar), and catalyst mass (50 mg) resulted in 75.3% selectivity for THF. In the continuous-flow reactions of GBL, excellent results were obtained with the pellets calcined at 300 °C due to their high surface area. Under the conditions of 175 °C, 50 bar of H₂, a GBL flow rate of 0.1 mL/min, an H₂ flow rate of 0.7 mL/min, and a bed height of 7 cm, 52% GBL conversion and 86% selectivity for BDO were achieved. Overall, the results obtained in this work highlight the effectiveness of solvent-free approaches and the versatility of scCO₂ as a selectivity regulator, reinforcing the potential of these systems in green and sustainable processes with unprecedented selectivities for THF and BDO. Furthermore, the study suggested the development of technical catalysts for large-scale applications.
Abrandamento de água do mar utilizando tensoativos para aplicação em processo químicos texteis
(Universidade Federal do Rio Grande do Norte, 2025-04-11) Ferreira, Iêda Leticia de Souza; Barros Neto, Eduardo Lins de; https://orcid.org/0000-0002-1310-7689; http://lattes.cnpq.br/2811639726261017; http://lattes.cnpq.br/2390918450550799; Bezerra, Clovis de Medeiros; https://orcid.org/0009-0004-7093-5028; http://lattes.cnpq.br/4188360050180967; Medeiros, José Ivan de; https://orcid.org/0000-0002-8888-4765; http://lattes.cnpq.br/0875521131771417; Nascimento, Paula Fabiane Pinheiro do; https://orcid.org/0000-0002-0930-8656; http://lattes.cnpq.br/9568438570514870; Melo, Ricardo Paulo Fonseca; https://orcid.org/0000-0001-7448-9273; http://lattes.cnpq.br/2188795979320167
The preservation of freshwater resources is a current and extremely important challenge for the sustainable development of society. In this context, the textile industry has a high impact due to the excessive water consumption inherent in its processes. To reduce freshwater consumption in the textile industry, the application of seawater in the process of dyeing cotton fabrics with reactive dye was initially investigated. The experiments were carried out by varying the concentrations of seawater in the dye solution, from 0% to 100%. The results obtained demonstrated that even under conditions of high hardness (up to 6000 mg/L of total hardness) it is possible to obtain dyed samples with good color levels, presenting color intensity only 6% lower than that obtained with fresh water. By adapting the formulation with seawater, it was concluded that it is possible to reduce the fresh water used in textile dyeing with reactive dyes by up to 70%. It was observed that the hardness level of seawater is a limiting factor for the applicability of this type of water, so a softening process was developed for seawater. Thus, in the second stage of the research, the use of two biodegradable surfactants was evaluated through the ionic flocculation methodology with subsequent filtration to reduce seawater hardness. The surfactants were synthesized from coconut oil and soybean oil, and used in concentrations ranging from 1 to 39 g/L. The efficiency of the treatment was evaluated in terms of reduction of the total hardness of the seawater. Additionally, a predictive mathematical model of the hardness of treated solutions was developed. It was possible to obtain a softening level of 86.8% by carrying out the treatment with 39 g/L of the surfactant synthesized with coconut oil. In order to investigate the applicability of softened water, its use in chemical textile processes was investigated. The results were satisfactory; in three processes analyzed, two showed equivalences to processes conducted with fresh water. And in none of the analyses was degradation observed in the materials processed with raw or treated seawater. The softening of seawater by ionic flocculation proved to be an innovative, effective, sustainable and low-cost alternative. Therefore, this research presents important contributions to alleviate the scarcity of fresh water in Brazil and in the world.
Estudo da síntese de carvões ativados a partir do bagaço de cana-de-açúcar e análises estatísticas e termodinâmicas no processo de adsorção de corantes
(Universidade Federal do Rio Grande do Norte, 2023-12-21) Soares, Larissa Azevedo; Souza, Carlson Pereira de; Moriyama, André Luís Lopes; https://orcid.org/0000-0001-7611-2074; http://lattes.cnpq.br/5552878900145656; http://lattes.cnpq.br/1030834608582624; http://lattes.cnpq.br/8522512153728494; Araújo, Camila Pacelly Brandão de; Gomes, Mayara Feliciano; Dantas, Suylan Lourdes de Araújo
Several methodologies are found in the current literature for the synthesis of activated carbons, starting with the available varieties of precursors, the types of processes, which can be physical and/or chemical, in addition to a multitude of activating agents, which can have different chemical functions that range from chlorides, acids and hydroxides. In this context, this work's first objective is to study the influence of the process and chemical agents used in the production of activated carbon (AC), with sugarcane bagasse as a precursor, as well as to evaluate the impacts of each process on the final characteristics of this product. To this end, two activated carbon synthesis processes were used, the first using fresh sugarcane bagasse as a precursor and the second in carbonized form, also varying the chemical activation agents, one with an acidic function and the other with a basic function (H3PO4 and KOH), in the end, 4 activated carbons were obtained, which were characterized by the techniques of XRD, FRX, SEM and N2 Volumetrics, Zeta Potential and capacity to remove the methylene blue dye (AM). The best results were obtained for activated carbon CA1A (produced through process 1 using the acidic chemical agent) reaching specific surface area values of around 1200 m2.g-1. Following the work, with the second objective of optimizing the adsorption process with CA1A, a study was carried out with an anionic dye, Erionyl Yellow A-R (EY). The adsorption tests for EY were carried out by varying the pH and temperature of the medium. Through the data obtained statistically, it was verified that the studied variables had significant effects and that the test at 30°C and pH 2 obtained the highest amount of adsorbed dye (q), reaching a value of 61.1 mg/g. In the search for a process with predictive characteristics, another adsorption process was studied, this time with the cationic dye, Methylene Blue (AM). For this adsorption study, it was found that the variables studied presented significant and predictive effects, within the range of experimental levels studied for the 95% confidence interval. It was also found that the largest amount of dye adsorbed by activated carbon (q) was 288.4 mg/g, with the test using 10mg of CA, at 27°C and pH 2. Still for Methylene Blue, the equilibrium, kinetics and thermodynamic factors were studied, under the conditions optimized by the experimental design.
Síntese de nanopartículas de lignina do bagaço da cana-de açúcar para aplicação na estabilização de emulsões pickering água/água e encapsulamento de bioativos
(Universidade Federal do Rio Grande do Norte, 2024-07-30) Pedro, Marcelo da Silva; Oliveira, Jackson Araújo de; Padilha, Carlos Eduardo de Araújo; http://lattes.cnpq.br/5058617634570704; http://lattes.cnpq.br/4210209303947439; Santos, Everaldo Silvino dos; Rios, Nathalia Saraiva; Jesus, Anderson Alles de; Lira, Daniel Silveira
Lignin, despite being the second most abundant biopolymer on the planet, remains underutilized in the production of value-added products. In response to this, studies have been exploring lignin's applications in various fields, with the production of nanoparticles emerging as a promising avenue for lignin valorization. Lignin nanoparticles have already been tested for their ability to stabilize oil/water (O/W) or water/oil (W/O) Pickering emulsions, including the encapsulation of bioactives such as quercetin, a bioflavonoid with antioxidant and anticancer properties. When consumed orally, quercetin decomposes rapidly in the early stages of digestion, and encapsulation is a strategy to ensure its bioavailability. However, O/W or W/O Pickering emulsions have limitations due to the hydrophobic phase, particularly in applications like probiotic encapsulation, production of low-calorie foods, and formulation of drugs with hydrophilic properties. On the other hand, water/water (W/W) Pickering emulsions can mimic biological environments, with stability ensured by the addition of nanoparticles capable of adsorbing at liquid-liquid interfaces. This study investigated the use of lignin extracted from sugarcane bagasse as a source of nanoparticles for stabilizing W/W Pickering emulsions formed by maltodextrin (MD) and polyethylene glycol (PEG), as well as for stabilizing O/W Pickering emulsions for the encapsulation of quercetin. The MD and PEG system was chosen due to its low cost, the ability to form two phases over a wide concentration range, and its potential for food applications. The nanoparticles were prepared from lignin obtained through alkaline and alkaline oxidative pretreatment. The alkaline oxidized lignin nanoparticles (NPLOs, 327.8 nm) were smaller than the alkaline lignin nanoparticles (NPLs, 689.8 nm). The stability of W/W Pickering emulsions formed from MD and PEG was evaluated in the presence of NPLs and NPLOs at different concentrations (0%, 0.1%, 0.3%, 0.5%, and 1%, w/w). Systems with NPLOs showed better emulsification indices and smaller droplet sizes compared to systems with NPLs. The most significant stabilization results were obtained at a concentration of 1% w/w of NPLOs, with an emulsification index of up to 63% even after two weeks. NPLs and NPLOs were also applied to stabilize O/W Pickering emulsions for the encapsulation of quercetin. In this case, the results indicated a tendency for quercetin to become trapped in the oil phase droplets. At a pH below 3, both types of nanoparticles formed agglomerates in the upper phase. NPLs demonstrated better interaction with the hydrophobic phase, enhancing the encapsulation of quercetin dispersed in this phase. The encapsulated quercetin was incorporated into food systems, and after 24 hours, high-performance liquid chromatography (HPLC) analysis showed that the concentration of quercetin added to cashew juice, in the presence of NPLs, was higher than in the condition without nanoparticles. These results suggest that lignin can be an important source of nanoparticles for stabilizing W/W and O/W Pickering emulsions, with potential applications in the encapsulation of bioactives such as quercetin in O/W Pickering emulsions.
Avaliação de dano em meios porosos decorrentes da reinjeção de água produzida
(Universidade Federal do Rio Grande do Norte, 2024-08-16) Araújo, Elayne Andrade; Dantas, Tereza Neuma de Castro; Aum, Pedro Tupã Pandava; http://lattes.cnpq.br/0676872399141537; https://orcid.org/0000-0002-3322-8517; http://lattes.cnpq.br/7106697546956681; Santos, Adriano dos; Deus, Katherine Carrilho de Oliveira; Sabadini, Edvaldo; Carvalho, Márcio da Silveira
The rise in oil production has led to a growth in the generation of produced water, which can be reused as an injection fluid in oil reservoirs to enhance oil recovery. However, this water contains oil droplets, dispersed and dissolved solids, bacteria, and other contaminants that can negatively affect the formation permeability near the well. Many studies report a reduction in rock permeability due to the retention of emulsified oil droplets during the reinjection of produced water, but the formation damage mechanisms caused by each contaminant are still not completely known. For an accurate analysis of these processes, it is fundamental that the emulsions maintain their stability during the injection test in porous media. Therefore, this work aimed to investigate the stability of these emulsions and propose a new approach to evaluate the impact of each component in the reduction of rock permeability. The emulsions were prepared by varying the surfactant concentration (0.0025 to 0.0100 wt%), stirring speed (9.000 to 21.000 rpm) and oil concentration (0.0050 to 0.0500 wt%). Subsequently, coreflooding tests were conducted on Berea sandstone samples with different permeabilities and emulsions with varying volumetric oil concentrations ranging from 0.01 to 0.05 wt%, evaluating the permeability drop in three stages of injection: (I) brine; (II) brine + surfactant; (III) stage II + oil. Emulsions with interfacial tensions over 10.6 mN/m remained stable and unimodal throughout the analyzed period. Coreflooding tests showed that brine injection resulted in a permeability drop of 7% to 20% in rocks with permeabilities approximately ranging from 20mD and 120 mD, respectively. Following this, surfactant injection showed a permeability decrease ranging from 30% to 37% in the first section. Tests with emulsions containing oil concentrations of 0.05 wt% and 0.01 wt% caused a reduction to around 65% of the permeability in low-permeability rocks. Damage from the retention of oil droplets was more significant in all scenarios studied, especially in rocks with low permeability. The results indicated that emulsion components contributed to the reduction of the rock permeability, highlighting the importance of considering them to enhance experimental model and mathematical modeling of damage caused by different permeability reduction mechanisms.
Energia solar térmica para fins de dessalinização: pesquisa e desenvolvimento de destiladores solares aplicáveis ao semiárido brasileiro
(Universidade Federal do Rio Grande do Norte, 2024-05-20) Leite, Wildson Ursulino; Moriyama, André Luís Lopes; https://orcid.org/0000-0001-7611-2074; http://lattes.cnpq.br/5552878900145656; http://lattes.cnpq.br/9758747023052656; Pereira, André Anderson Costa; Araújo, Camila Pacelly Brandão de; Sousa, Magna Angélica dos Santos Bezerra; Gomes, Mayara Feliciano; Melo, Raffael Andrade Costa de
In this study, a solar distiller model was developed and tested to meet the demand for desalinated water for human consumption in the Brazilian semi-arid region. The project involved analyzing mathematical models of solar incidence in the real environment and optimizing the design of the distillers to enhance radiation capture. A preliminary computational study was conducted to determine the most suitable geometry for local test conditions. To make the solar desalinator a viable technology for decentralized communities in the semi-arid region, the project prioritized system simplicity and the careful selection of construction materials that are economically accessible, chemically safe, and environmentally responsible. The proposed construction methodology aims for scalability of the distillers, utilizing a modular platform with precast lightweight expanded polystyrene concrete parts to provide adequate strength and thermal insulation. Tests using black paint as a photocollector demonstrated an accumulated distilled water production of 4.38 kg/m²/day, exceeding the reference system production by 72.1%. With only 4% commercial activated carbon as a photocollector, production reached 3.35 kg/m²/day, representing a 74.4% increase compared to the reference system. The average salt removal was approximately 99.4%. Another advantageous feature of the developed desalinator is its capability for semi-batch operation without affecting distilled water production, significantly reducing costs associated with process control systems. Due to its unique characteristics, the modular solar desalinator shows potential to become a socially relevant alternative, effective in mitigating the impacts of drought in the Brazilian semi-arid region.
Encapsulação de compostos bioativos da acerola (Malpighia emarginata DC) por spray drying e nanoprecipitação usando carreadores proteicos: avaliação das partículas de acerola, estabilidade de armazenamento e aplicação em produtos alimentares
(Universidade Federal do Rio Grande do Norte, 2024-06-27) Ribeiro, Dayene Nunes; Hoskin, Roberta Targino; https://orcid.org/0000-0003-0900-4983; http://lattes.cnpq.br/7098666299806958; http://lattes.cnpq.br/6032005266788441; Pedrini, Marcia Regina da Silva; Matsui, Katia Nicolau; Passos, Thais Souza; Silva, Flávio Luiz Honorato da; Medeiros, Fábio Gonçalves Macêdo de
Brazil is the world's largest producer and exporter of acerola (Malpighia emarginata DC.), one of the richest natural sources of ascorbic acid. However, the high perishability of the fruits and the fact that ascorbic acid is easily degraded when subjected to food processing and storage due to exposure to light, oxygen, high temperatures and extreme pH, compromise their commercial use. Therefore, processing techniques that preserve the bioactive compounds of acerola and create profitable value-added alternatives and diversification of products are of special interest to the industry. Therefore, this doctorate dissertation investigates two relevant encapsulation techniques - spray dying and organic solvente nanoprecipitation - applied to both acerola juice and pomace using protein carriers. The work was divided into two distinct approaches. Initially, spray dried acerola microparticles were produced with whey protein isolate, soy protein isolate and hydrolyzed collagen (isolated or combined) as drying carriers. Six experimental groups were investigated: acerola juice with isolated soy protein – ASP; acerola juice with isolated whey protein – AWP; acerola juice with collagen – ACO; acerola juice with a mixture of isolated soy protein/ collagen 1:1 – ASC; acerola juice with a mix of whey protein isolate/collagen 1:1 – AWC; acerola juice with a mix of whey protein isolate/soy protein isolate 1:1 – AWS. Treatments were evaluated for the process performance (solids recovery and polyphenol retention) and quality of the final product (total polyphenol content and solubility) and the best treatment was selected for the study of storage stability and subsequent incorporation into starch films produced by casting. AWC microparticles achieved good solids recovery (> 50%), polyphenol retention and total phenolic content (TPC; > 70% and 128.45 mg GAE/g, respectively), in addition to high water solubility (85.2%). AWC particles were selected to produce biodegradable cassava starch films with water vapor permeability of 0.29 g mm/m2 h kPa and antioxidant activity (measured by 2,2-diphenyl-1-picrylhydrazyl DPPH) of 6.57 μM TE/g, in addition to greater migration of polyphenol to water (6.30 mg GAE/g film) compared to acetic acetic. In the second part of this study, acerola particles were produced by spray drying and organic solvent nanoprecipitation from bioactive compounds recovered from acerola pomace (peel, seeds and pulp) using whey protein isolate. Acerola spray dried microparticles were developed using lab-scale drying with input temperature of 150 ºC. Nanoparticles were prepared by the nanoprecipitation technique using a core: encapsulating agent ratio of 1:4 (p:p), Tween 80 surfactant and stirring speed (17,000 RPM) during ethanol evaporation of. The influences of the two encapsulation processes were evaluated regarding solids recovery and encapsulation efficiency, in addition to the physicochemical characteristics (scanning electron microscopy SEM, particle size diameter, Zeta potential, infrared spectroscopy with transform Fourier analysis FTIR, solubility, and hygroscopicity) concentration of bioactives (total phenolic content and ascorbic acid) and DPPH antioxidant activity. Furthermore, the particles were evaluated for storage stability under controlled conditions and fortification in natural yogurts. Both encapsulation techniques showed solids recovery greater than 50%. The phenolic encapsulation efficiency was higher for nanoparticles (79.7 ± 4.1%) compared to spray dried microparticles (66.5 ± 2.5%). Both particles had spherical shapes, with nanoparticles showing a smooth surface in the nanometer scale (178.37 ± 39.70 nm), while spray dried microparticles showed wrinkled surfaces on the micrometer scale (1.87 ± 0.63 μm). The Zeta potential results showed moderately stable (pH < 3.5) and highly stable (pH > 6.9) nanoparticles, while spray dried particles were moderately stable (pH > 7.5). FTIR demonstrated the interactions of whey protein with acerola pomace extract through electrostatic interactions and new chemical bonds, suggesting encapsulation. The nanoparticles had higher TPC (52.24 ± 2.42 mg GAE/g) and ascorbic acid (671.3 ± 294 mg AA/100 g) compared to microparticles (TPC = 39.72 ± 0.61 mg GAE/g and AA = 358.74 ± 77.85 mg AA/100 g) (p<0.05). Yogurt fortified with acerola particles was stable for 14 days, when the TPC in yogurt with acerola microparticles (36.25± 2.96 mg GAE/100 g) was higher than yogurt with nanoparticles (22.02 ± 0.3 mg GAE/100 g). Overall, results show that encapsulation techniques are efficient strategies for producing ingredients and products with preserved phytochemical characteristics and improved attributes from acerola, both from acerola juice and pomace.
Geração de bioenergia com captura intríseca de CO2 via processo de iG-CLC em planta piloto contínua
(Universidade Federal do Rio Grande do Norte, 2024-07-15) Oliveira, Gislane Pinho de; Braga, Renata Martins; Adánez-rubio, Iñaki; https://orcid.org/0000-0002-6232-0945; http://lattes.cnpq.br/4603529162393328; http://lattes.cnpq.br/0670520594680554; Alves, José Luiz Francisco; Melo, Marcus Antônio de Freitas; Melo, Dulce Maria de Araújo
The continuous increase in CO2 emissions and its effect on global warming imposes the need for collaborative actions between scientists and government to implement strategies aimed at reducing CO2 emissions. Among these strategies, carbon capture and storage technologies stand out that, especially when associated with the use of biofuels, as they can achieve a negative balance of CO2 emissions. Chemical looping (CL) is recognized as an energy-efficient approach to capture and store CO2 and has high technological maturity. In these processes, the search for low-cost solid oxygen carriers (OC) is motivated by the loss of OC incurred when solid biofuels are employed. In this context, this study aims to select, characterize and evaluate the energy potential of different biomasses and the reactivity of low-cost mineral materials as solid oxygen carriers for application in chemical looping combustion process with gasification in situ (iG-CLC) in pilot plant with continuous power supply with a technology readiness level (TRL) 4. The biomasses were characterized by proximate, ultimate, thermogravimetric analysis, analytical flash pyrolysis and determination of calorific value. The OCs were characterized using X-ray diffraction and fluorescence techniques, scanning electron microscopy, determination of crushing strength, and attrition rate. Their reactivities with CH4, H2 and CO were evaluated in thermobalance performing redox cycles at 900 °C and in a semi-continuous fluidized bed reactor (FBR) at 850, 900 and 950 °C. The reactivity during iG-CLC process of the selected OC was evaluated in FBR at 900°C feeding char of the selected biomass; and in a 0.5 kWh pilot plant with continuous biomass feed. The selected biomass showed high calorific value (18 MJ/kg), high volatile + fixed carbon content (67%) and ashes with high K and Ca content, which can catalyze gasification reactions. All OCs showed low friction rate and good crushing strength, except for Mn, which is why it was submitted to calcination. The OCs Fe2, Fe3 and MnT1000 (Mn calcined at 1000 °C) demonstrated favorable attributes such as adequate crushing strength (>1 N), minimum attrition rate (<7%), good oxygen transport capacity (3.3%, 1.7% and 3.4%, respectively) and high reactivity in thermobalance. They also showed excellent performance in FBR with CO and H2, without agglomeration, good reoxidation rate and lifetime ranging from 3000h to 10500 hours. Notably, due to the excellent performance of the MnT1000 with CO and H2, it is a promising candidate for application in the iGCLC process. The iG-CLC tests in FBR indicates that an oxygen-to-biomass ratio greater than 30 promotes complete combustion of the gasification products, while lower values promote incomplete combustion. The iG-CLC tests in a continuous pilot plant indicate that an increase of the temperature of the fuel reactor or a decrease in the oxygen-biomass ratio increases the CO2 capture efficiency (>87%) and the combustion efficiency (>85%) while the excess oxygen has little influence on the process. The MnT1000 stood out as an oxygen carrier, did not suffer agglomeration in any of the tests, presented high performance, high reactivity, resistance, is environmentally friendly and low-cost. The application of a highly reactive low-cost TSO in iG-CLC processes using biomass stands out as an energy-efficient alternative to produce energy with intrinsic CO2 capture with a negative CO2 emissions balance.
Argilas organofílicas aplicadas à remoção de carbamazepina visando a remediação de águas subterrâneas contaminadas
(Universidade Federal do Rio Grande do Norte, 2024-02-26) Viegas, Rayanne Macêdo Aranha; Chiavone Filho, Osvaldo; Furtini, Josy Anteveli Osajima; http://lattes.cnpq.br/2621516646153655; http://lattes.cnpq.br/8095792689248890; Silva Filho, Edson Cavalcanti da; Bezerra, Italla Medeiros; Magalhães, Vivian Maria de Arruda
In recent years there has been growing concern about the contamination of water by emerging contaminants, such as pharmaceuticals. Carbamazepine (CBZ) is a psychotropic drug widely used throughout the world and has been frequently detected in water bodies, including groundwater. Organoclays have been used as efficient adsorbents for pharmaceutical pollutants. In this study, four types of organoclays were prepared from the modification of national bentonite clay with two cationic surfactants: hexadecyltrimethylammonium bromide (HDTMA) and octadecyltrimethylammonium bromide (ODTMA). X-ray diffraction analyzes showed that the basal spacing of organoclays varied from 1.54 to 2.93 nm, suggesting the intercalation of organic cations in the interlayer space of montmorillonite. Initially, the synthesized clays were evaluated as adsorbents for the sorption of CBZ through batch equilibrium experiments, under variation of the pH, contact time, dosage of adsorbent, and initial drug concentration. pH variation showed no adsorption influence. CBZ sorption by the organoclays followed a pseudo-second-order kinetics. The best sorption performance was obtained for the BCN1-HDTMA100 clay, with a capacity of 34.34 ± 1.41 mg/g, about ten times greater than the unmodified bentonite under the same conditions. This may be attributed to the higher surfactant content. The adsorption isotherm at 25 ºC showed linear behavior. FTIR and TG analyzes on organoclay-CBZ hybrids confirmed the incorporation of the drug. Hydrophobic interaction was the dominant contribution evaluated to the adsorption of CBZ. Furthermore, toxicity tests were carried out on organoclays and the medium in the presence of CBZ before and after treatment. This is a novelty report. Most of the organoclays had no toxicity against Artemia salina. The toxicity of the medium after adsorptive treatment was eliminated. After batch study, two synthesized organoclays (BCN1-HDTMA100 and BCN1-ODTMA100) were selected for the study of continuous adsorption of CBZ through tests in a fixed bed column filled with a mixture of sand and organoclay aiming at application as a medium reactive Permeable Reactive Barriers (PRB) for groundwater remediation. At this stage, the performance of the synthesized clays was compared to that of a commercial organoclay, Spectrogel Type C. The adsorption performance was evaluated using breakthrough curves. The effects of the initial drug concentration, quantity and type of clay in the fixed bed were evaluated. In general, the synthesized clays performed better than Spectrogel Type C. The lower adsorption capacity of CBZ by commercial clay may be associated with effects related to the packing density of organic cations in the interlayer space. Under the conditions of 1.0g of clay in the bed, 95 mg/L of initial CBZ concentration and flow rate of 1.0 mL/min, the clays BCN1HDTMA100 and BCN1-ODTMA100 presented breakthrough times of 505 and 525 min and adsorption capacities of 46.6 and 50.1 mg/g, respectively. Therefore, organoclays have demonstrated promising potential for use in groundwater remediation applications.
Produção de biodiesel em reator de atomização
(Universidade Federal do Rio Grande do Norte, 2023-10-27) Deus, Marcell Santana de; Souza, Domingos Fabiano de Santana; Oliveira, Jackson Araújo de; http://lattes.cnpq.br/5058617634570704; https://orcid.org/0000-0002-1594-6814; http://lattes.cnpq.br/7400460833577257; http://lattes.cnpq.br/0836742195451577; Jesus, Anderson Alles de; Padilha, Carlos Eduardo de Araújo; Ruiz, Juan Alberto Chavez
Biodiesel is an alternative fuel widely used for partial or total replacement of fossil fuels. Although biodiesel production is undoubtedly a mature technology, there are still ways to improve it, especially through the process intensification. So, the present study investigated the esterification of oleic acid with ethanol and the transesterification of sunflower oil with ethanol for biodiesel production in a non-conventional atomization reactor. The effects of the oleic acid and sunflower oil flow rates, atomization pressure, temperature and catalyst concentration were evaluated. A mathematical model was also developed to describe the conversion of oleic acid to ethyl ester as a function of molar concentration of components and operating conditions of the reactor. A hybrid estimation of parameters (activation energy, pre-exponential factor, equilibrium constants, and solubility) was performed. In the esterification, the Pareto analysis has shown that the increase of temperature in the reactor and the increase of atomization pressure have improved the conversion of oleic acid. Higher pressure values in the atomization vessel led to the generation of small oleic acid and sunflower oil droplets, which accelerated reagent consumption during the reaction. On the other hand, conversion values are reduced by increasing oleic acid flow rate. In the transesterification, it was observed that the flow rate had a negative effect and, the pressure had a positive effect on the conversion of sunflower oil. Droplet size distribution analysis showed that increasing pressure in the atomization chamber led to a reduction in droplet size, which explains the effects on ethyl ester conversion. The highest conversion of oleic acid was obtained under the following reaction conditions: 70 ◦C, 1.5 bar, oleic acid flow rate equal to 1.3 g/min using 0.6% catalyst, and 2 h of reaction time. In the transesterification, conversions of 98.3% were obtained with a flow rate of 3 g/min of sunflower oil at 50 ◦C, 1.5 bar and 1.0% of catalyst in 1 h. The mathematical model achieved good fit with independent experimental data and the parameters obtained from the hybrid estimation strategy were in accordance with the literature.
Modificações em espumas de poliuretano pós-comercializadas para sorção de óleos derramados em água do mar
(Universidade Federal do Rio Grande do Norte, 2024-03-14) Rocha, Keslei Rosendo da; Oliveira, Humberto Neves Maia de; Chiavone Filho, Osvaldo; http://lattes.cnpq.br/2621516646153655; http://lattes.cnpq.br/7302633941782540; http://lattes.cnpq.br/5593337707941382; Araújo, Alessandro Alisson de Lemos; Pereira, Andre Anderson Costa; Medeiros, Gilson Gomes de; Fernandes, Manoel Reginaldo
The exploration, transportation, and refining of oil are fundamental to the global economy. Occasionally, oil spills in the ocean are reported. Rapid containment and remediation are essential to prevent oil from being carried to the coasts by wind and wave action. The methods currently used to remove oils in water are not free of flaws, and because of that, constant research to develop alternative methods is necessary. In this context, this work proposed the use of post-consumer polyurethane foams to recover oils spilled in seawater. Surface modifications were carried out to increase the selectivity of foams for oils and resulted in increases up to 611% and 991% for modifications with molybdenum disulfide (MoS2) and zinc oxide (ZnO) in systems with S46 lubricating oil and 20W40 engine oil, respectively. These results show the success of hydrophobization and lipophilicity added to the foams through the modifications made. The reuse and resistance to mechanical compression tests showed that even after 10 sorption/desorption cycles, the foams kept their oil recovery capacity without a statistically significant difference. This result demonstrates the economic potential of modified foams thanks to their high reusability capacity. Kinetic studies on seawateroil systems showed that the saturation speed depends on the viscosity of the oil, but that the foam pores are saturated with fluids practically instantly and reach equilibrium in less than 40 seconds of exposure. The pseudo-second order (Ho and McKay) and logistic (Richards and Verhulst) kinetic models were those (among all kinetics models studied) that most adequately described the behavior of the experimental data in all cases. In continuous sorption, the modifications favored oil selectivity, but the vacuum pumping operating mode was the most relevant factor, achieving recovery of up to 99% of the oils initially spilled.
Estudo da otimização do processo de hidrogenação catalítica do ácido fumárico
(Universidade Federal do Rio Grande do Norte, 2022-03-25) Figueredo, Adolfo Lopes de; Courtial, Camila Gambini Pereira; Gomes, Pedro Miguel Vidinha; https://orcid.org/0000-0003-2472-9755; http://lattes.cnpq.br/8055289812908100; https://orcid.org/0000-0002-2685-2223; http://lattes.cnpq.br/2681922036812736; Braga, Tiago Pinheiro; Lopes, Francisco Wendell Bezerra; Garcia, Marco Aurélio Suller; Moura, Maria Carlenise Paiva de Alencar
The selective production of valuable products for the chemical industry such, as γ-butyrolactone (GBL), tetrahydrofuran (THF) and 1,4-butanediol (BDO) that results from the catalytic hydrogenation of fumaric acid (Ac.FUM) is a quite interesting subject in the field of biomass valorization. In fact, these products can be considered bioplatforms of molecular construction, functioning as a starting point for countless synthesis processes. From the point of view of green chemistry, water and CO2 are considered ideal solvents to drive this type of chemical transformation. Although achieving good conversion rates and selectivity in these reaction media, the catalytic performance of this hydrogenation reaction can be a challenge, even when a suitable catalyst is employed. In this context, this process was studied and optimized, firstly through experimental design using a palladium-rhenium silica-supported catalyst (Pd-Re/SiO2), and a iridium-rhenium silica-supported catalyst (Ir -Re/SiO2), as second choice, barely used in the literature for selective hydrogenation of Ac.FUM in GBL an aqueous medium. The catalysts were synthesized by sequential wet impregnation, and characterized by XRD, RTP, ICP, TEM, surface area and pore volume analysis. Reaction products were identified by GC-FID and HPLC-RI. In a second moment, supercritical CO2 was used as a reaction medium to optimize the process, varying pressure between 105-300 bar under 60-250 ºC. Finally, solvent evaluation was studied in the reaction selectivity, where methanol was also used under 60-250 ºC and 10-300 bar. The catalysts showed metal percentage of 3 % for Pd and Ir, and 6 % for Re, with a surface area of 257 and 219 m2gcat-1, pore volume of 1.31 and 1.20 cm3gcat-1 and average particle size of 2 and 1.5 nm, for Pd-Re and Ir-Re, respectively. TPR, DRX and TEM analyzes suggest that the metals are in close contact, with interaction between them. The results of Ac.FUM hydrogenation using catalysts based on palladium-rhenium and iridium-rhenium showed that GBL was produced with 91 and 90% selectivity, respectively, under the optimized conditions of pressure and temperature predicted by the empirical model of 188 °C and 41 bar of H2 for Pd-Re/SiO2 and 210 °C and 25 bar of H2 for Ir-Re/SiO2. Thus, the experimental design allowed a high selectivity to be obtained in an aqueous medium, providing better rationalization of the combined effect of the temperature and pressure variables. Furthermore, statistical analysis in experimental design showed that temperature has more signifcant effect on GBL selectivity concerning H2 pressure, being non-linear for both catalysts. In studies using supercritical CO2, it was possible to model the catalytic activity, suppressing the formation of by-products and obtaining 89 % and 64% selectivity for GBL using PdRe/SiO2 and Ir-Re/SiO2, respectively, under optimized operating conditions. The addition of methanol as solvent changed the composition of products, obtaining THF as the major product, with a maximum selectivity of 97 % under the conditions of 175 °C, 50 bar of H2 and 150 bar of total pressure for Pd-Re/SiO2, and 89 % under conditions of 175 °C, 50 bar H2 and 300 bar total pressure for Ir-Re/SiO2.
Dessulfurização de combustíveis via extração líquido-líquido em microdispositivos
(Universidade Federal do Rio Grande do Norte, 2024-03-08) Santiago, Luiz Eduardo Pereira; Souza, Domingos Fabiano de Santana; Padilha, Carlos Eduardo de Araújo; https://orcid.org/0000-0002-9532-3026; http://lattes.cnpq.br/1186888955341616; https://orcid.org/0000-0002-1594-6814; http://lattes.cnpq.br/7400460833577257; http://lattes.cnpq.br/8654979200815633; Jesus, Anderson Alles de; Vitor Sobrinho, Eledir; Ruiz, Juan Alberto Chavez
Conventional methods for removing sulfur compounds perform poorly especially when treating aromatic compounds. Current studies have directed efforts to investigate deep extractive desulfurization (EDS) using microdevices. Microdevices are units with micrometer-sized channels that enhance mass and heat transfer phenomena. For EDS in microdevices to be viable, it is essential to choose the appropriate extractor solvent used. Among the possibilities, an excellent candidate is polyethylene glycol (PEG). The present work aims to analyze the use of PEG 300 and PEG 400 in the removal of dibenzothiophene. The identification of flow patterns was carried out using digital image colorimetry, making it possible to estimate the specific interfacial area and the volumetric mass transfer coefficient. The experiments followed na experimental logic that allowed extracting insights into deep desulfurization. In addition, the mass transfer phenomena involved and the application of the best experimental conditions in a real diesel sample were evaluated. The results obtained with model fuel were able to achieve 99,36% DBT removal with 1,0 minute residence time, 1:1 volumetric ratio, and three extraction cycles, in microchannels with 0,5 mm in diameter and 1,0 m in length. Furthermore, applying the best experimental conditions to diesel, the total sulfur concentration decreased from 1646 to 312 ppm, resulting in an extractive efficiency of 81,04%.
Uso de cloreto de colina no pré-tratamento da fibra de coco verde visando à produção de etanol 2G e a valorização da lignina como agente coagulante
(Universidade Federal do Rio Grande do Norte, 2023-12-19) Rocha, Juliene da Câmara; Santos, Everaldo Silvino dos; Padilha, Carlos Eduardo de Araújo; https://orcid.org/0000-0002-9532-3026; http://lattes.cnpq.br/1186888955341616; https://orcid.org/0000-0001-7384-1140; http://lattes.cnpq.br/4330639792072559; http://lattes.cnpq.br/4060616632489375; Sousa Júnior, Francisco Canindé de; Rios, Nathalia Saraiva; Santos, Sharline Florentino de Melo; Oliveira Júnior, Sérgio Dantas de
One way for coconut companies to increase their cost-benefit and reduce the dependence on non-renewable energy sources is by using green coconut fibers (GCFs) in value-added products. In this study, GCFs were pretreated with choline chloride ([Cho][Cl]) in an acidified medium with diluted sulfuric acid to enrich cellulose on the solid fraction and lignin on the liquid fraction. The aim was to evaluate the feasibility of obtaining 2G ethanol from simultaneous (SF) and semi-simultaneous fermentation (SSFS) strategies. The study also examined the recycling of pretreatment effluents and their impact on enzymatic hydrolysis and fermentation stages. The pretreatment was conducted in an autoclave (1 atm, 121 °C) without or with diluted sulfuric acid (1.0%, w/w), using different concentrations of [Cho][Cl] (50 and 75%, w/w) and incubation times (25 and 50 min). The pretreated GCFs were then submitted to enzymatic hydrolysis (20 FPU/g), and the best condition was chosen for the SF and SSFS fermentation processes. Additionally, the research has investigated the removal of lignin from the liquid fraction for use as a coagulating agent in oil-contaminated water. The results showed that pretreatment with [Cho][Cl] at a concentration of 75% (w/w) in 50 min of reaction time and an acidified medium with 1% (w/w) of diluted sulfuric acid (C75/50m/H) as the best pretreatment to increase the conversion of cellulose into glucose, reaching 22.6 g/L of free sugar. The SSFS achieved the best efficiency of 32.43% (23.2 g/L alcoholic concentration) and a productivity of 0.483 g/L.h for the condition of 20% solid load in obtaining 2G ethanol. Furthermore, 82.6% of the lignin was recovered from the liquid fraction of this same pretreatment, wherethe application of lignin in the treatment of water contaminated with oil achieved removal of 99% of oil from the aqueous phase. Therefore, GCF pretreated with choline chloride has the potential for 2G ethanol production. Furthermore, the use of lignin generates an adsorbent with the potential to be used in different processes, including in the petroleum industry.
Valorização de resíduos lignocelulósicos como bioadsorventes de íons cobre e desenvolvimento de sensor colorimétrico a base de levulinato de sódio para sua detecção
(Universidade Federal do Rio Grande do Norte, 2023-12-29) Pereira, Jéssyca Emanuella Saraiva; Barros Neto, Eduardo Lins de; http://lattes.cnpq.br/2811639726261017; https://orcid.org/0000-0002-7612-0303; http://lattes.cnpq.br/1917271015016548; Duarte, Lindemberg de Jesus Nogueira; http://lattes.cnpq.br/6800188552647660; Lopes, Francisco Wendell Bezerra; Nascimento, Paula Fabiane Pinheiro do; Melo, Ricardo Paulo Fonseca
In recent years, humanity has advanced in many ways, but it has also caused serious damage to the environment. Human activities such as burning fossil fuels, deforestation and waste production have generated pollutants that affect air, water and soil quality. In this scenario, the contamination of water bodies has become a serious environmental problem due to issues related to the improper disposal of effluents contaminated by heavy metals. As a result, this heavy metal pollution has serious consequences for the health of people and ecosystems. In light of these facts, this thesis aimed to evaluate the potential of using bioadsorbents obtained from cashew leaf (CL), carnauba straw (CS) and the extraction of lignin from green coconut fiber (GCF) to remove copper ions (Cu2+) from synthetic effluents. Nevertheless, the feasibility of using an organic molecular sensor obtained from the synthesis of sodium levulinate (NaLev) for the colorimetric detection of Cu2+ was evaluated, which constitutes a simple and efficient alternative for on-site analysis of metal ions in aqueous solution. To this end, adsorption studies were carried out in a batch system and the effects of pH, adsorbent concentration, particle size and initial adsorbate concentration were evaluated. In order to extract the lignin from the GCF, an alkaline pre-treatment with 2% sodium hydroxide was carried out, followed by impregnation with sodium octanoate to improve the adsorption capacity of this bioadsorbent. NaLev was synthesized by hydrating levulinic acid with distilled water and adding 20 g of sodium hydroxide. The concentrations of copper, NaLev and then the copper-NaLev mixture were determined by molecular absorption spectroscopy in the ultraviolet and visible (UV-Vis) regions. The effects of different concentrations of Cu2+ and NaLev on the maximum absorbance and wavelength were evaluated. The experimental CS data were best fitted by the Langmuir monolayer model, while the CL data were fitted by the Freundlich model. For the same experimental conditions, the maximum adsorption capacity for Cu2+ was 9.51 mg.g-1 and 1.73 mg.g-1 for CS and CL powders, respectively. For GCF lignin impregnated with surfactant, the results of the adsorption study revealed that the adsorption capacity improved due to the increase in the number of functional groups on the bioadsorbent surface. The results of the colorimetric sensor evaluation showed that the addition of NaLev significantly increased the absorbance as the wavelength decreased from 810 to 575 nm in the samples without and with NaLev, respectively. In addition, the color intensity of the solution containing Cu2+ increased as the concentration of NaLev increased. The results showed that it is feasible to use lignocellulosic biomass to remove Cu2+ since the removal capacity is similar to other traditional sources of adsorbents. It was also observed that alkaline pre-treatment and impregnation using the surfactant carried out in the GCF was effective in obtaining a bioadsorbent with adequate Cu2+ removal capacity. Finally, the NaLev colorimetric sensor for detecting Cu2+ appears to be a promising class of biobased heavy metal-free colorimetric sensors.
Desenvolvimento de um simulador em linguagem Visual Basic for Applications para processos fotocatalíticos de transformação
(Universidade Federal do Rio Grande do Norte, 2023-07-31) Lopes, Herbert Senzano; Souza, Carlson Pereira de; Bezerra, Vanja Maria de França; http://lattes.cnpq.br/7566236243351252; http://lattes.cnpq.br/1030834608582624; http://lattes.cnpq.br/9669152092439524; Araújo, Alessandro Alisson de Lemos; Chiavone Filho, Osvaldo; Carvalho, Patrícia Cristina de Araújo Puglia de
The present work aims to apply the Excel® spreadsheet tool in the development of a simulator applied to photocatalytic reactors. Toluene degradation was selected as the study case for implementing the simulator. The Visual Basic for Applications (VBA) programming language was applied for numerical methods as well as for generating of graphics and an efficient interface. It is also worth highlighting the availability of Microsoft® programs, making the tool more accessible in solving process system engineering problems. A model system from the literature describing the kinetics of a toluene photocatalytic oxidation reaction was simulated. The contaminant concentration profile (toluene) is obtained as a function of position in the reactor and also based on input operational data, meaning that system and reaction information can be freely altered. This allowed the study of different reactor dimensions, flow rates, initial concentrations, reaction rates, and catalyst characterization parameters. The reactional system was designed so that the catalyst present in the annular fixed bed receives radiation properly. The simulation was performed considering the model as onedimensional and in a steady state. The results obtained were satisfactory for determining the toluene degradation velocity profile as well as the photoreactor sizing values. For the operational conditions of the process, simulations were conducted by varying the dimensions of the photoreactor, both length and radius, as well as the radiation intensity. The results demonstrated that the developed tool allows the simulation and analysis of the toluene photocatalytic degradation process as a function of the main involved variables and parameters.
Aplicabilidade de resíduos à base de ferro como catalisadores Fenton para degradação de fenol
(Universidade Federal do Rio Grande do Norte, 2023-08-31) Hollanda, Luana Rabelo; Chiavone Filho, Osvaldo Chiavone; Foletto, Edson Luiz; https://orcid.org/0000-0003-2443-7445; http://lattes.cnpq.br/6550340290019699; http://lattes.cnpq.br/2621516646153655; http://lattes.cnpq.br/0278440789950629; Mota, Andre Luis Novais; http://lattes.cnpq.br/6655822329418320; Silva, Douglas do Nascimento; https://orcid.org/0000-0001-5934-9491; http://lattes.cnpq.br/0841120842454720; Deus, Katherine Carrilho de Oliveira; http://lattes.cnpq.br/4261532489868408; Silva, Maitê Medeiros de Santana E; http://lattes.cnpq.br/5181350934389542
Contamination of water bodies by organic compounds has been a matter of great concern due to its impacts on the human health and the environment. Phenol is a highly toxic compound commonly found in industrial effluents due to its high use in several segments. Advanced Oxidative Processes (AOP), which encompass a wide range of techniques for generating reactive radicals, have shown satisfactory efficiencies in the degradation of recalcitrant organic compounds. The heterogeneous Fenton reaction is a type of AOP that employs hydrogen peroxide and solid catalysts containing iron for generating reactive species. This study aimed to investigate the potential application of two industrial waste materials as alternative catalysts in the Fenton reaction for the degradation of phenol in water: coal bottom ash from a thermoelectric power plant and amethyst mining residue (AMR). The materials were characterized using different techniques, such as X-ray diffraction, X-ray fluorescence, scanning electron microscopy coupled with energy dispersive spectroscopy, Fourier transform infrared spectroscopy and textural analysis. Bottom ash was applied in the Fenton reaction, while AMR was used in the photo-Fenton system. The effects of different operational parameters, including solution pH, catalyst dosage, and H2O2 concentration, were investigated. The characterization results indicated that both materials have mesoporous structures with well-distributed active iron species. Regarding the bottom ash, under optimal conditions, which involve the use of 1,0 g L-1 of catalyst, 6 mM H2O2 and pH = 3, a phenol degradation efficiency of 98.7% was observed after 60 min of reaction, along with 71.6% organic carbon removal after 150 min. The photo- Fenton reaction using AMR exhibited 96.5% degradation under optimal conditions (0.75 g L-1 of catalyst, 7.5 mM H2O2 and pH = 3) after 180 min, removing 42.3% of the organic carbon after 240 min. Through tests with the addition of isopropanol, it was verified that the hydroxyl radical is the main oxidizing agent involved in the cleavage of the phenol molecule for the two studied systems. Regarding the reuse tests, both catalysts showed stability and satisfactory catalytic activity through four consecutive cycles. Therefore, the obtained results demonstrate that the two waste materials display potential activity for application in Fenton reactions for degrading phenol.
Pré-tratamentos aplicados ao amido de arroz vermelho para a produção de nanocristais visando o uso em emulsões pickering Óleo/Água (O/A)
(Universidade Federal do Rio Grande do Norte, 2024-02-06) Almeida, Raphael Lucas Jacinto; Santos, Everaldo Silvino dos; https://orcid.org/0000-0001-7384-1140; http://lattes.cnpq.br/4330639792072559; https://orcid.org/0000-0001-7232-2373; http://lattes.cnpq.br/0056534203066666; Padilha, Carlos Eduardo de Araújo; https://orcid.org/0000-0002-9532-3026; http://lattes.cnpq.br/1186888955341616; Rios, Nathalia Saraiva; https://orcid.org/0000-0002-5104-1123; http://lattes.cnpq.br/1800467263737484; Souza Filho, Pedro Ferreira de; https://orcid.org/0000-0002-1711-7294; http://lattes.cnpq.br/3140602874903609; Oliveira Júnior, Sérgio Dantas de; https://orcid.org/0000-0001-5113-4728; http://lattes.cnpq.br/4641007172823726
Durante a produção dos nanocristais de amido (SNC), os pré-tratamentos podem ser uma alternativa promissora para quebrar os grânulos de amido e/ou criar poros e rachaduras e, assim, permitir uma melhor difusão do ácido. Esses nanocristais podem ser utilizados para aumentar a estabilidade da emulsão Pickering. Dessa forma, o presente estudo avaliou o uso dos pré-tratamentos não térmico, hidrotérmicos e enzimáticos no amido de arroz vermelho para a produção de SNC. Para isso, foi utilizado o pré-tratamento (I) não térmico com campo elétrico pulsado (PEF: 10 e 30 kV cm-1) no amido e verificado a sua ação quando combinado a α-amilase pré-tratamento (II) (PEF+α). Enquanto que para o pré-tratamento (III) hidrotérmico (HPT: autoclave e cozimento) nos grãos e no amido foi verificado a influência na cinética de secagem, onde posteriormente ambos foram combinados com a hidrólise enzimática usando a α-amilase (IV). Uma nova rota de modificação enzimática do amido foi avaliada após o tratamento com HPT para isso foi usado as enzimas α-amilase e amiloglucosidase de forma semi-simultânea (HSS) em comparação com a técnica usual que é feita de forma consecutiva (CH). Para o pré-tratamento (V) foi testado a estratégia de hidrólise semi-simultânea (HSS) visando otimizar o tempo de processo e reduzir a quantidade de solventes, quando comparado a forma consecutiva (CH) com α-amilase e amiloglucosidase, ambas com carga enzimática de 9 U mg-1. Os resultados mostraram que tanto com o uso do PEF como o do HPT apresentaram uma diminuição do tempo de secagem em até 180 min, sendo que o HPT alcançou os mais altos rendimentos (53,54%). A ordem de aplicação do PEF afetou as características estruturais do amido, sendo que PEF30+α foi mais eficaz na redução da sinérese e retrogradação, por conta do aumento de 83,30% no grau de digestão. O HPT quando aplicado no amido foi viável para modificar a estrutura e a susceptibilidade enzimática com α-amilase, resultando em mudanças na geometria dos grânulos, ruptura das moléculas de amilose e amilopectina, diminuição da cristalinidade e formação de complexos amilose-lipídeo. Destaca-se ainda que o método HSS (α-amilase e amiloglucosidase) foi mais efetivo apresentando um maior valor de grau de digestão (80,08%) e propriedades tecnológicas otimizadas em relação ao amido nativo. O HPT com autoclave (A3) permitiu a produção eficiente de SNC em apenas 1 dia de hidrólise ácida, reduzindo significativamente o tempo de processo. Quando aplicados em emulsões Pickering, os SNCs (3%) apresentaram eficácia na estabilização para as temperaturas 4, 25 e 40ºC, com tamanho máximo de partículas de 180 µm, que foi reduzido para 138 µm sem quercetina e 98 µm com quercetina (1%) no 21o dia. Apesar da hidrólise ácida, usando ácido sulfúrico, ser o método mais comum para a produção de SNC, devido ao seu baixo custo, há necessidade de melhorar o processo, por meio de pesquisa neste campo, pois o baixo rendimento e o tempo longo na produção de SNC impedem o progresso. Explorar novas rotas para modificar o amido nativo é importante, com foco em técnicas ecologicamente corretas, no qual métodos térmicos e não térmicos combinados oferecem a vantagem de alterar a estrutura do amido enquanto minimizam o uso de reagentes tóxicos. Esses métodos emergentes devem ser aplicados para verificar a estabilização das emulsões Pickering, que pode ser viável por melhorar as interações interfaciais.
Desenvolvimento e avaliação de soluções ácidas contendo Nonilfenóis Polietoxilaados e etanol para acidificação de carboidratos
(Universidade Federal do Rio Grande do Norte, 2023-10-17) Arruda, Guilherme Mentges; Wanderley Neto, Alcides de Oliveira Wanderley; Rodrigues, Marcos Allyson Felipe; https://orcid.org/0000-0002-8936-5705; http://lattes.cnpq.br/5453593230706116; http://lattes.cnpq.br/4896975705563570; http://lattes.cnpq.br/4896975705563570; Silva, Dennys Correia da; https://orcid.org/0000-0002-6280-7606; http://lattes.cnpq.br/8567051112814180; Galvão, Edney Rafael Viana Pinheiro; http://lattes.cnpq.br/3142315953748654; Pinto, Marcio Augusto Sampaio; https://orcid.org/0000-0003-1125-7218; http://lattes.cnpq.br/3705277331954152; Vale, Tulio Yterbio Fernandes; http://lattes.cnpq.br/4911813695252136
During the different stages of well development and reservoir exploitation, there is the possibility of the occurrence of unwanted phenomena that alter the permeability of the near-wellbore region (formation damage), compromising the production. The well stimulation techniques seek to bypass or reverse this damage and, consequently, increase production. Matrix acidizing in carbonates consists of injecting an acidic fluid into the well to increase its production by dissolving the rock matrix itself, creating channels known as wormholes. Hydrochloric acid (HCl) is the most used substance to stimulate both production and injection wells in carbonate reservoirs. However, the high reaction rate of HCl with carbonate reduces its penetration into the rock formation since the acid reacts excessively with the rock surface (face dissolution). Thus, to minimize acid consumption and increase the depth of wormholes, it is necessary to develop stimulation fluids containing additives that reduce the acid dissolution rate of the carbonate matrix. The present study aims to develop and evaluate new acid solutions containing nonionic surfactants and ethanol to delay the dissolution of calcium carbonate in the acidification process of carbonate rocks, providing deeper wormholes in the reservoir. To do so, characterization analyses were carried out for the developed fluids and carbonate samples. In addition, compatibility tests of the components of the developed fluids, reactive flow in porous media tests (injection of the formulations in rock samples) and computerized microtomography of acidified rocks were performed. As a result, it was found that fluids containing surfactants with a higher degree of ethoxylation promoted a more significant increase in viscosity and in the delay of the carbonate rock dissolution. In the reactive flow in porous media tests, regarding the minimum pore volume to breakthrough (optimal PVbt), the formulations obtained similar results to those of 15% HCl but at flow rates 4 to 8 times lower. These low flow rates are more consistent with those observed in field treatments. Furthermore, the formulations produced wormhole patterns that are similar to the dominant one over a broader injection rate range. Therefore, the studied formulations provided promising results in the reactive flow in porous media tests and presented some interesting characteristics for application in acid stimulation treatments

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