Biblioteca Digital do IPB
Repositório de Publicações do Instituto Politécnico de Bragança
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The puzzle of capital structure theories and the financial system: review
Publication . Rogão, Márcia; .
The main objective of this paper relates to conducting a synthesis of the various studies that have used country-specific factors, especially macro-financial factors related to the countries' financial system, to explain the understanding of firm's capital structure choices. Several international studies have approached the explanation of the capital structure problem by resorting to determinants related to country-specific factors and, more recently, several studies have emerged that analysed the convergence of the financing decisions of companies according to the financial system of their countries. However, in terms of literature review, it can be seen that there are no studies to make the interconnection between the explanatory theories of capital structure and the innovative character of some researchers who resorted to the characteristics of the financial system to explain the financing behaviour of companies from several countries. And, as such, the present paper consisted in summarizing the empirical literature in a non-systematic way and found that various studies indicate that the capital structure is influenced by the concept of the financial system, where financial intermediaries play a key role in reducing transaction costs and information costs, and the efficiency of capital markets contributes to reducing the information costs of the hierarchy of the firm's financing sources.
Treatment of pomace olive oil wastewater by peroxy-electrocoagulation with aluminium sheets
Publication . Martins, Ramiro; Tesuka, Leticia; Grabowski, Thais
The extraction of olive pomace oil is a significant aspect of the edible oil industry in Mediterranean regions where olives are widely cultivated. The resulting wastewater generated from this industry is known to harbor pollutants, including residual solvents, oils, and chemicals from the refining process, that can have adverse effects on the environment and public health. Peroxy-electrocoagulation (PEC) is a method that can be used to treat wastewater from the olive pomace oil extraction industry. The purpose of the work was to reduce the concentration of pollutants in the effluent through the use of PEC with aluminum electrodes as a method of treatment. The Box-Behnken Design was used to study the relationship between hydrogen peroxide dosage (10, 20, and 30 g L-1), electric current density (5, 20 and 35 mA cm-2), and the initial pH (2.5, 3.5, and 4.5), in the PEC process, and the removal of chemical oxygen demand (COD) and total phenolic compounds (TPh). The highest removal was obtained with hydrogen peroxide dosage of 30 g L-1, and 20 mA cm-2, and with 29% of TPh removal at pH 2.5, and with 84% COD removal at pH 4.5. The procedure removed an average of 22% COD and 82% TPh. The concentration of hydrogen peroxide was one of the most significant factors in the process. Pre-treatment with other techniques is necessary to reduce harmful elements in the effluent before undergoing biological treatment
Solid Dispersions as a Tool for Innovation in the Food Industry: A Path From Pharma to Food
Publication . Rezende, Stephany; Santamaria-Echart, Arantzazu; Dias, Madalena M.; Barreiro, Filomena
Solid dispersion (SD) is a technique used to improve the solubility of poorly water-soluble compounds by dispersing them in a solid water-friendly carrier. Current trends indicate that natural-based alternatives are increasingly replacing synthetic carriers, benefiting the pharmaceutical industry, where they were first adopted, and paving the way for broader use in nutraceuticals and food applications, as regulations and consumer preferences drive the adoption of eco-friendly alternatives. In the food industry, SDs can address key challenges, such as enhancing water compatibility and stabilizing sensitive compounds, thereby facilitating the effective use of natural-based ingredients. Exploring natural carriers enables SDs to align with food industry priorities, enabling the development of functional ingredients, stable natural colorants, products with increased flavor retention, innovative packaging materials, and healthier, structured food analogues through Pickering emulsion technology. In this context, the review examines the path of SDs from pharma to food, beginning with a detailed examination of SD systems using both synthetic and natural carriers across the pharmaceutical, nutraceutical, and food sectors. The review concludes with an in-depth discussion of emerging applications in the food industry, highlighting the potential of SDs to address formulation challenges and to foster sustainable, consumer-oriented innovations in modern food systems. To advance SD applications in food systems, future research should integrate sensory evaluation and address technical, regulatory, and formulation-performance gaps to ensure consumer-acceptable, high-quality innovations.
Removal of metformin from aquatic matrices using cork-based adsorbents
Publication . Morizaki, Gabrielle Tokawa; Gomes, Maria Carolina Sérgi; Queiroz, Ana; Brito, Paulo; Ribeiro, António E.
Metformin is considered an emerging micropollutant, belonging to the pharmaceutical class, and is widely used in the treatment of type 2 diabetes. Due to its incomplete metabolism and extensive prescription for chronic disease management, it has been frequently detected in aquatic environments. Even at trace concentrations, it may cause endocrine disruptions in aquatic biota and lead to the formation of toxic byproducts during water treatment.1,2 In this context, the present study aimed to evaluate the efficiency of metformin removal from aqueous matrices through the adsorption process, using activated carbons produced from cork residues. The methodology involved the preparation of the adsorbents via physical activation (CF) and chemical activation using potassium hydroxide (KOH) (CQ), followed by characterization in terms of carbonization yield, moisture and ash content, point of zero charge (pHPZC), presence of acidic and basic surface functional groups, and Fourier-transform infrared spectroscopy (FTIR). Metformin quantification was carried out by high-performance liquid chromatography with diode array detection (HPLC-DAD). Studies on drug removal, adsorption kinetics, activation energy estimation, and evaluation of operational parameters influencing the process, such as adsorbent dosage, pH, and initial metformin concentration, were conducted. The results demonstrated that the type of activation applied to each carbon significantly influenced the physicochemical properties of the materials, as well as their adsorption performance. According to the kinetic studies, adsorption equilibrium was reached within the first minutes for CQ, while for CF it was more gradual. In equilibrium studies, the Freundlich and Langmuir isotherm models were applied. For CF, both models showed a good fit, with a predominance of the Freundlich model, indicating a slightly heterogeneous surface and favorable adsorption. For CQ, the Langmuir model provided a better fit, with a high maximum adsorption capacity, suggesting monolayer adsorption on a more homogeneous surface.3,4
From the study carried out, the activated carbons produced from cork residues demonstrated high performance as promising materials for the removal of metformin in aqueous media, particularly those obtained through chemical activation, achieving a removal efficiency of approximately 99.0% under optimized alkaline pH conditions (pH 11). The use of this residue as a raw material highlights the potential of renewable-origin adsorbents in water treatment processes, contributing to the valorization of an abundant by-product in Portugal and to the development of more environmentally sustainable solutions, in line with the principles of a circular economy.
Uso de membranas incorporadas com cortiça para a purificação de biodiesel de óleo residual
Publication . Romansina, Bruna Clara; Brito, Paulo; Paschoal, Sirlei M.; Gomes, Maria Carolina Sérgi
O biodiesel vem ganhando destaque no mundo por possuir matéria-prima renovável, além de ser menos poluente que os combustíveis fósseis. Após a transesterificação, é necessária a separação e purificação dos ésteres, sendo empregadas lavagens aquosas para remover o glicerol. Porém, este processo convencional requer um alto volume de água. O objetivo deste trabalho foi avaliar o processo de separação utilizando membranas poliméricas funcionalizadas com cortiça como alternativa na purificação de biodiesel. O biodiesel foi produzido por transesterificação etílica utilizando óleo de algodão residual e NaOH como catalisador. As membranas foram produzidas pelo método de inversão de fases empregando polietersulfona como polímero, polivinilpirrolidona como copolímero, dimetilacinamida como solvente e cortiça como aditivo. As membranas foram caracterizadas em termos de permeabilidade hidráulica e MEV. O processo de separação foi realizado em um módulo de membranas e avaliou-se a filtração em duas fases distintas da produção do biodiesel. A primeira fase após a transesterificação e a segunda foi após a decantação da mistura reacional, utilizando a fase leve rica em ésteres. A menor concentração de glicerol obtida no permeado foi 0,097 ± 0,006%, na filtração da fase leve contendo os ésteres, representando uma retenção do glicerol pela membrana foi de 99,65%.