ESTiG - Dissertações de Mestrado Alunos
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- Tailored polymer networks for purification of polyphenols in almond subproductsPublication . Pinto, Vítor Amaro da Costa; Dias, RolandoThe valorization of agro-industrial by-products has aroused great interest nowadays, due to their richness in phenolic compounds, including polyphenols, and their biological activities of high value for various areas. In this work, the recovery and concentration of these compounds, from hydroalcoholic extracts from hull and also blanching water, were studied, being two residues of large volume in the almond industry. The enrichment is given by sorption/desorption processes in columns packed with Molecularly Imprinted Polymers (MIPs), having used the polymers MIP-OA-3, MIPQUER-2 and MIP-QUER-3, and evaluating the enrichment efficiency against a gradient of several solvents in the elution steps. The hull extracts were obtained essentially by ultrasound, having worked with a hydroethanolic fraction 50/50 (v/v), due to their yield and equivalent favoring in the extraction of different polyphenolic families, being subsequently submitted to the sorption process. The characterization of the elutions of both by-products was mainly done by determining the total phenolic content (TPC) and the antioxidant activity by the DPPH method (EC50), and the best results were reinforced with chromatographic analyses by HPLC-DAD at 280 and 360 nm. The results show that the process allowed the selective fractionation and enrichment of phenolic compounds, observing fractions with a high degree of enrichment when compared to the initial extract, both at the TPC and EC50 levels. The intermediate hydroethanolic fractions, as well as the methanolic fractions, present the best results in terms of enrichment, as evidenced by the inverse relationship between TPC and EC50. It was also possible to verify differences in the enrichment trend between the OA3 column and the Q2 Q3 columns, revealing different affinities provided by the polymers. Chromatograms reveal significant changes in the chemical profile, both between fractions, extract and columns, suggesting and proving the enrichment of certain phenolic compounds, particularly flavonoids. In general, the results obtained indicate that the MIPs used have a high potential for phenolic enrichment from complex extracts, being able to fractionate and enrich, contributing to strategies for sustainable recovery of waste and development of processes aligned with the principles of green chemistry. Among these results, maximum TPC values of 615.66 ± 28.23 mg GAE/g Extract (hull) and 918.32 ± 34.54 mg GAE/g Extract (blanching water) were observed, together with EC50 values of 0.025 ± 0.000 and 0.028 ± 0.002 mg/mL, respectively. A value of 1135.64 ± 11.55 mg GAE/g Extract and 0.017 ± 0.000 mg/mL was also observed, indicating a high phenolic recovery.
- Surfactant removal from industrial effluents by moringa seed-assisted coagulation and photo-fenton oxidationPublication . Belgacem, Soufienne; Martins, RamiroWater pollution caused by surfactant-containing industrial effluents has become an important environmental concern due to the extensive use of detergents in domestic and industrial applications. Among these pollutants, sodium dodecyl sulfate (SDS) is one of the most widely used anionic surfactants and is frequently detected in wastewater because of its low biodegradability and adverse effects on aquatic ecosystems. Consequently, the development of efficient and sustainable treatment technologies for surfactant removal is of increasing importance. This study investigated the removal of SDS from synthetic industrial wastewater using a combined treatment consisting of Moringa oleifera seed-assisted coagulation followed by the Photo Fenton oxidation process. The coagulation stage was evaluated by studying the effects of coagulant dosage, initial surfactant concentration, and pH on SDS removal. Subsequently, the Photo Fenton process was optimized by evaluating the influence of pH, hydrogen peroxide dosage, ferrous ion concentration, and UV irradiation using Response Surface Methodology (RSM). The coagulation process achieved a maximum SDS removal efficiency of 55.6% under the optimum operating conditions. The subsequent Photo Fenton treatment significantly improved the removal efficiency, reaching 96% SDS removal. Process optimization using Response Surface Methodology predicted a maximum removal efficiency of 99.4% under the optimum conditions of pH 3, 1 mL of H₂O₂, 270 mg of FeSO₄·7H₂O, and a flow rate (Q) of 84 mL min⁻¹. The results demonstrate that combining Moringa oleifera-assisted coagulation with the Photo Fenton process is an effective and environmentally sustainable strategy for removing anionic surfactants from industrial wastewater. The integration of a natural coagulant with an advanced oxidation process provides a promising alternative for improving wastewater treatment efficiency while reducing reliance on conventional chemical treatments.
- Aditivos naturais: potencial conservante na indústria alimentarPublication . Santos, Beatriz Cavalcante; Pereira, Eliana; Amaral, J.S.; Defendi, RafaelA crescente procura por alimentos mais saudáveis, sustentáveis e com rótulos mais transparentes tem impulsionado a investigação de alternativas naturais aos conservantes sintéticos utilizados pela indústria alimentar. Paralelamente, a valorização de subprodutos agroindustriais tem emergido como uma estratégia promissora para a redução do desperdício alimentar e promoção da economia circular. Neste contexto, diferentes matrizes vegetais constituem fontes relevantes de compostos bioativos com potencial aplicação como conservantes naturais. O presente trabalho teve como objetivo desenvolver e caracterizar um extrato natural rico em compostos bioativos com potencial aplicação como conservante alimentar, recorrendo à valorização de diferentes matrizes vegetais, nomeadamente urtiga (Urtica dioica), bioresíduos de romã e brócolos. Inicialmente, foram avaliadas as atividades antioxidante e antimicrobiana, bem como a toxicidade dos extratos, de forma a selecionar a matriz com maior potencial bioativo e segurança de utilização. A urtiga foi selecionada para estudos posteriores, tendo o seu processo de extração sido otimizado através da metodologia de superfície de resposta, considerando como variáveis de resposta a atividade antioxidante, o teor de massa seca e o perfil individual de compostos fenólicos. Posteriormente, o processo de extração foi otimizado através da metodologia de superfície de resposta, utilizando a extração assistida por ultrassom e considerando como variáveis independentes a potência do ultrassom, o tempo de extração e a proporção etanol/água. A otimização teve como objetivo maximizar a atividade antioxidante, o teor de massa seca e a recuperação de compostos fenólicos. As condições ótimas determinadas pelos modelos matemáticos foram posteriormente validadas experimentalmente. O extrato otimizado foi caracterizado por HPLC-DAD-ESI/MS, permitindo a identificação de sete compostos fenólicos, correspondentes a quatro ácidos fenólicos e três flavonoides, com um teor total de 19,8 mg/g de extrato seco. Os flavonoides constituíram a classe predominante (11,6 mg/g), destacando-se a quercetina-3-O-rutinosídeo (rutina) como composto maioritário, seguida da quercetina-3-O-glicosídeo. Entre os ácidos fenólicos identificados destacaram-se os ácidos cafeoilquínicos e o ácido dicafeoilmálico. Estes compostos estão associados a reconhecidas propriedades antioxidantes e anti-inflamatórias, reforçando o potencial bioativo do extrato obtido. A validação experimental das condições ótimas confirmou a adequação do processo de extração desenvolvido, sendo posteriormente realizada uma comparação com um extrato comercial de urtiga. Os resultados obtidos demonstram o potencial da urtiga como fonte de compostos fenólicos de interesse para a indústria alimentar, evidenciando a viabilidade da utilização de extratos naturais como alternativa sustentável aos conservantes sintéticos e contribuindo para o desenvolvimento de ingredientes alinhados com o conceito de clean label.
- Valorization of biomass waste for the removal of fluoxetine from aqueous matricesPublication . Mattos, Kim Nicolas; Queiroz, A.M.; Ribeiro, António E.; Brito, Paulo; Lima, Vanderlei Aparecido deThis research examines the use of olive pit waste to remove fluoxetine, a pharmaceutical drug classified as an emerging pollutant. It is an constituent that threatens the environment due to its bioaccumulation. Conventional wastewater treatment plants cannot remove it completely. The activated charcoal used was previously recovered from olive pits and chemically activated with NaOH. Kinetic tests showed that as temperature increased, the amount of removal from the material increased as well, reaching up to 98.87% at 45 degrees Celsius. Overall the pseudo second-order kinetic model fit the experimental data the best with a χ2 value equal to 0.003725 at 45 degrees Celsius. The Freundlich model fit the equilibrium study better than the Langmuir model, indicating that adsorbing compounds are done so on heterogeneous surfaces and continue through multiple layers. The maximum capacity of adsorption from Langmuir’s model was identified to be 17.07 mg g-1 with regards to olive pit adsorbent. For thermodynamic analysis, the activation energy was found to be 42.32 kJ mol-1, and the Gibbs free energy indicated a value of -0.851 kJ mol-1 supporting the conclusion that the adsorption process is both spontaneous and favourable thermodynamically. Based on these results, it can be concluded that activated carbon from olive pits is a sustainable and effective alternative for treating water with pharmaceutical micropollutants.
- Development of multifunctional emulsions based on lignin and cellulose for cosmetic applicationPublication . Domingos, Giovanna Martins; Barreiro, Filomena; Sipoli, Caroline CasagrandeThe growing consumer demand for safer, more natural, and environmentally sustainable cosmetic products has driven the development of alternative formulation strategies. One promising approach involves emulsion systems stabilized by solid particles, rather than molecular surfactants, known as Pickering emulsions. These systems offer improved biocompatibility, enhanced stability, and eco-friendly character. Microcrystalline cellulose (MCC) containing residual lignin is an innovative material that has attracted industrial interest for high-value-added applications. In this context, the present work investigated the use of MCC at different lignin contents as a stabilizing agent in the development of multifunctional Pickering emulsions for cosmetic applications. The influence of lignin content on particle wettability and interfacial behavior was evaluated, as well as the effect of physical modification through high-pressure homogenization (HPH) and lignin particle precipitation within MCC samples. The MCC properties, including size distribution and wettability, were analyzed to correlate structural characteristics with emulsion performance. HPH modified the MCC structure and size, improving its dispersion behavior and Pickering-stabilizing performance. However, the processed samples also exhibited greater heterogeneity, and the significant increase in average particle diameter observed suggests the formation of fibrillar structures, particle aggregation, and/or re-agglomeration after processing. Pickering emulsions were successfully produced using MCC dispersions and Miglyol 812 as the oil phase under a 1:1 oil-to-water volume ratio. The resulting systems were characterized in terms of morphology, droplet size, emulsified layer formation, rheological behavior, and storage stability over time. The results showed that lignin content is a critical parameter governing the performance of MCC-based Pickering stabilizers, with small variations in residual lignin content significantly influencing particle hydrophobicity and emulsion stabilization efficiency. MCC Crude (18.7%) showed the highest stabilizing performance, indicating that the higher residual lignin content favored particle hydrophobicity and interfacial adsorption. In contrast, MCC White (4.0%) exhibited poor stabilization due to its highly hydrophilic nature, even after processing. MCC Blond (6.5%) provided intermediate stability while producing light-colored emulsions, a particular advantage for cosmetic applications. For the MCC Crude sample, the lignin particle precipitation approach altered the interfacial properties of the material; however, the results indicated that HPH processing was more advantageous for improving Pickering stabilization performance. Overall, this work demonstrated the innovative use of MCC samples containing residual lignin as Pickering stabilizers, advancing understanding of, and strategies to improve, their interfacial properties and stabilization mechanisms in high-value Pickering emulsions.
- Natural-based coagulants from chestnut shells for turbidity and color removal: toward sustainable wastewater treatmentPublication . Vieira, Juliana Akemy Inamine; Martins, Ramiro; Pietrobelli, Juliana MartinsTurbidity and color are critical parameters in industrial wastewater treatment, particularly in textile effluents containing suspended particles and dyes. Conventional coagulation methods are effective but have significant drawbacks. In this context, the development of natural coagulants has emerged as a promising alternative method. This study investigated the production of a natural-based coagulant from chestnut shells (Castanea sativa), an abundant agro-industrial residue in Portugal, through tannin extraction followed by chemical modification via the Mannich reaction. The tannin extraction process was statistically optimized using a Box-Behnken Design to evaluate the effects of pH, extraction time, and biomass dosage. The coagulant performance was evaluated using Jar Test assays for turbidity (kaolin) and color (methylene blue) removal. Statistical analysis showed that these factors affected turbidity and color removal differently, with higher extraction times and biomass dosage generally favoring turbidity removal. The results showed high turbidity removal efficiencies, reaching up to 96%, whereas color removal efficiencies were lower, reaching approximately 26%, suggesting that dye removal depends not only on coagulation mechanisms but also on specific interactions between the dye and the coagulant. Overall, the results demonstrate the potential of chestnut shell residues as a sustainable source of natural-based coagulants for wastewater treatment.
- Síntese e caracterização de poliuretanos produzidos com monómeros resultantes da despolimerização de polihidroxialcanoatos (PHB)Publication . Guerra, Diana Marques Da Costa; Dias, RolandoO elevado consumo de plásticos petroquímicos e a acumulação de resíduos impulsionam soluções alinhadas com a economia circular, nomeadamente através da utilização de biopolímeros, como o poli(3-hidroxibutirato) (PHB). Embora seja uma alternativa promissora aos plásticos convencionais, pelas suas propriedades comparáveis às do polipropileno, a sua baixa estabilidade térmica limita a reciclagem mecânica. Este trabalho focou-se na valorização química de monómeros e oligómeros de origem biológica obtidos por despolimerização do PHB, como polióis na síntese de novos poliuretanos sustentáveis. A metodologia iniciou-se com a determinação do índice de hidroxilo por titulação para estabelecer as proporções estequiométricas. Realizou-se uma triagem preliminar por polimerização em massa (bulk) de quatro monómeros com diisocianatos aromáticos (MDI) e alifáticos (HDI), selecionando-se os sistemas promissores por testes de solubilidade em dimetilformamida (DMF). Posteriormente, a síntese em solução foi otimizada em uma e duas etapas, e os materiais foram caracterizados quanto à sua estrutura química e massa molecular através de Espetroscopia de Infravermelho por Transformada de Fourier (FTIR-ATR) e Cromatografia de Permeação em Gel (GPC), respetivamente. Os resultados confirmaram a formação das ligações uretano e o forte impacto das condições reacionais e da estrutura dos monómeros no crescimento das cadeias. Na síntese de uma etapa, a comparação com o oligómero mostrou que o seu elevado volume e impedimento de tamanho limitam as massas moleculares finais com os monómeros obtidos por despolimerização do PHB, apenas o etilenoglicol, por ser pequeno e linear, conseguiu ultrapassar estas limitações. Verificou-se que o monómero 4HB-3HB originou poliuretanos com massas moleculares superiores, com uma massa molecular média em massa (𝑀𝑤) entre 8,7×103 e 1,5×104 g/mol, embora com uma distribuição mais heterogénea, enquanto o monómero 2HE-3HB originou um crescimento molecular mais moderado, 𝑀𝑤 entre 7,4×103 e 7,9×103 g/mol, mas com uma distribuição mais uniforme e controlada. Nas sínteses em duas etapas, a rota com DBTDL promoveu uma conversão inicial do oligómero altamente eficiente logo nas primeiras 24 horas. Como perspetiva futura, as amostras foram enviadas para análise por RMN de 1H na Hanze University of Applied Sciences, para validação estrutural.
- Short-term responses of mediterranean forest leptosols to organic amendments: effects on soil physicochemical properties and carbon storagePublication . Moura, Fernanda Roverato; Fonseca, Felícia; Conceição, Paulo CésarClimate change and soil degradation have intensified the need for sustainable management strategies capable of improving soil quality and enhancing carbon sequestration in terrestrial ecosystems. The present study evaluated the effects of different organic amendments on the physicochemical properties and soil organic carbon dynamics of a Mediterranean forest soil located in northeastern Portugal, one year after the establishment of a permanent experimental field. The experimental design consisted of six treatments: green waste (RV), stabilized compost (CE), and donkey manure (EB), applied at 5 and 10 Mg ha⁻¹, in addition to an untreated control (SO). Soil samples were collected at depths of 0–5 cm, 5–10 cm, and 10–20 cm to evaluate physical and chemical properties, including bulk density, permeability, porosity, soil organic matter, pH, total nitrogen, extractable phosphorus and potassium, soil organic carbon concentration, and soil organic carbon stock. Most soil physical properties remained relatively stable across treatments, although donkey manure and stabilized compost tended to promote lower bulk density and higher porosity and water retention. Significant increases in soil pH were mainly observed under CE10 (Stabilized Compost at 10 Mg ha⁻¹) and EB10 (Donkey Manure at 10 Mg ha⁻¹), indicating reduced soil acidity. Organic amendments also promoted higher trends of soil organic matter, total nitrogen, soil organic carbon, extractable phosphorus, and potassium, particularly in surface layers. EB5 (Donkey Manure at 5 Mg ha⁻¹) and CE10 (Stabilized Compost at 10 Mg ha⁻¹) showed the highest trends for soil organic carbon accumulation in the 0–5 cm layer. Overall, the results suggest that organic amendments, particularly donkey manure and stabilized compost, may contribute to improving soil quality and promoting carbon accumulation in Mediterranean forest soils undergoing ecological restoration.
- Walnut shells and eucalyptus bark as green alternatives to chemical coagulants in water treatmentPublication . Aires, Isabella Kaminski; Martins, Ramiro; Pietrobelli, Juliana MartinsWater resource management has become a major technical and environmental challenge of the 21st century, largely driven by the intensification of industrial activities and the resulting generation of increasingly complex wastewater. Conventional coagulation–flocculation processes, widely used in wastewater treatment plants, mainly rely on inorganic chemical coagulants, such as aluminum and iron salts. Although effective, these chemicals have notable environmental and operational limitations. In response to these challenges, growing attention has been given to developing of more sustainable alternatives aligned with the principles of green chemistry. In this context, this study investigated the potential of natural coagulants derived from walnut shells (Juglans regia) and eucalyptus bark (Eucalyptus spp.) as environmentally friendly alternatives to conventional chemical coagulants. These lignocellulosic materials are rich in tannins, polyphenols, and other bioactive functional groups that promote coagulation primarily through charge neutralization and polymer bridging mechanisms. Unlike many approaches reported in the literature, which rely on raw powders or chemically activated adsorbents, this study employed saline-assisted liquid extracts, providing a milder, more more sustainable extraction route. The results demonstrated that eucalyptus bark exhibited superior turbidity removal performance, reaching 91%, while walnut shell achieved a maximum of 80%. For color removal using methylene blue, both biomaterials showed comparable performance, with maximum efficiencies of 48% for eucalyptus bark and 47% for walnut bark. A comparative analysis with the literature confirmed that the observed efficiencies were lower than those reported for chemically activated or highly optimized systems; however, they remained relevant within the context of green, low-cost, and minimally processed treatment strategies. This study advances environmentally friendly water treatment technologies by systematically comparing two forest residues under mild extraction conditions, supporting their potential application as scalable alternatives to conventional coagulants.
- Advances in fenton and photo-fenton degradation of anionic surfactant SDBSPublication . Silva, Arthur Mariani; Martins, Artur; Pietrobelli, JulianaSurfactants are widely used in hygiene and cleaning products; however, their persistence in aquatic environments classifies them as emerging contaminants. This study aimed to evaluate the behavior and degradation efficiency of the anionic surfactant Sodium Dodecyl Benzene Sulfonate (SDBS) using Fenton and photo-Fenton Advanced Oxidation Processes (AOPs). Analytical monitoring of pollutant removal was performed using High-Performance Liquid Chromatography (HPLC). To optimize the operational variables – namely reaction time, pH, H2O2 and Fe2+ concentrations – Response Surface Methodology (RSM) and Analysis of Variance (ANOVA) were applied using Jamovi and RStudio software. The experimental results demonstrated that the photo-Fenton process significantly outperformed the conventional Fenton process, which was driven by UV radiation, promoting the continuous regeneration of Fe2+ ions and maximizing the generation of hydroxyl radicals (HO•). The reduced quadratic model for the photo-Fenton system was statistically significant (p = 0.013), highlighting reaction time as a critical factor (p = 0.024) and indicating a strong negative quadratic effect of iron concentration. The 3D response surfaces confirmed the presence of an optimal intermediate operation region, proving that excessive reagent dosages trigger scavenging effects, which limit further removal efficiency. The Fenton process achieved SDBS removal ranging from 22% to 52%, whereas the photo-Fenton process achieved SDBS removal ranging from 50% to 76%, demonstrating that both processes were effective and that UV irradiation enhanced the oxidative efficiency of the system. Ultimately, this study provides a robust technical framework aligned with the United Nations 2030 Agenda, directly contributing to Sustainable Development Goal 6 (Clean Water and Sanitation) by engineering efficient pathways for the removal of persistent surfactants from wastewater, while also aligning with SDG 12 (Responsible Consumption and Production) and SDG 14 (Life Below Water).