Percorrer por autor "Martins, Ramiro"
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- Accumulation and release of Pb(II) in aqueous solution by aquatic mosses (Fontinalis antipyretica)Publication . Martins, Ramiro; Freitas, Olga; Vilar, Vítor J.P.; Boaventura, RuiThe uptake and release of Pb(II) by Fontinalis antipyretica was studied in laboratory, by exposing the plants to different lead concentrations for 144 h and 335 h contamination and decontamination periods, respectively. A first order kinetic model was fitted to the experimental data to determine the uptake and release constants, k1 and k2, and other relevant parameters. The metal accumulation capacity, at equilibrium, follows the order: Pb(II) > Zn(II) > Cd(II) > Cr(VI). A Bioconcentration Factor (BCF) and a Biological Elimination Factor (BEF) were also determined; for 0.9–2.2 mg Pb l–1, BCF decreases from about 30748 to 21296.
- Acumulação e libertação de metais pesados por briófitas aquáticasPublication . Martins, RamiroTradicionalmente a remoção de metais pesados de efluentes é feita usando diversas técnicas (precipitação, electrólise, permuta iónica, osmose inversa, adsorção), normalmente dispendiosas e/ou pouco eficientes para soluções diluídas. A biossorção, processo em que materiais naturais ou seus derivados são usados na remoção e recuperação de metais pesados, proporciona um tratamento alternativo competitivo, pelo que os respectivos parâmetros cinéticos e de equilíbrio devem ser bem conhecidos, de modo a prevenir fracassos na sua aplicação. Nesse contexto, este trabalho teve por objectivo estudar os processos de bioacumulação/eliminação e de biossorção de Cd(II), Cr(VI), Pb(II) e Zn(II) pelo musgo aquático Fontinalis antipyretica, espécie largamente dispersa nos lagos e rios Portugueses. Os musgos aquáticos são capazes de acumular iões metálicos em solução aquosa e de libertá-los parcialmente quando expostos em água isenta de metal. Desempenham um papel importante na avaliação e na remoção de elementos tóxicos na água. A vantagem dos musgos relativamente a uma amostragem directa da água é que o seu uso permite uma integração de variações no espaço e no tempo, favorece o nível de quantificação do contaminante por concentração dos elementos tóxicos e fornece informação acerca das espécies biodisponíveis. Foram realizadas treze experiências laboratoriais em contínuo para determinar as cinéticas de acumulação e libertação de metal pelo musgo. Um modelo cinético de transferência de massa de primeira ordem (modelo de dois compartimentos) foi ajustado aos resultados experimentais, para determinar as constantes de acumulação e de eliminação, k1 e k2, a concentração de metal nos musgos no fim do período de acumulação, Cmu, e no equilíbrio, para as fases de contaminação e descontaminação, Cme e Cmr, respectivamente. Foram determinados factores de bioconcentração, BCF = k1 / k2, e de eliminação biológica, BEF = 1 - Cmr / Cmu. Para avaliação dos mecanismos envolvidos no processo de acumulação global dos metais foram estudados o efeito da concentração do metal, do pH do meio, da temperatura, da intensidade luminosa, do estado fisiológico da biomassa (época de colheita), da natureza da biomassa (viva/morta), da dureza da água e da realização de ciclos de contaminação/descontaminação consecutivos. Foram ainda realizadas experiências cinéticas e de equilíbrio em adsorvedor fechado, para avaliar o potencial do musgo como biossorvente de metais pesados em futuras aplicações industriais. Numa avaliação preliminar deste tipo de biossorvente, foi estudada a influência de alguns parâmetros operacionais, como o tempo de contacto, a concentração inicial de metal, a concentração de musgo usada e a presença de outros iões metálicos, na cinética de acumulação de Cd(II), Cr(VI), Pb(II) e Zn(II). Ajustaram-se diferentes modelos cinéticos – Lagergren, pseudo-segunda ordem, segunda ordem modificado de Ritchie, de Elovich e Sorção Dinâmica – aos resultados experimentais obtidos em adsorvedor fechado. O modelo de pseudo-segunda ordem foi o que conduziu ao melhor ajuste. Nos ensaios de equilíbrio em sistema fechado foi avaliada a influência da concentração inicial de ião metálico, pH inicial, temperatura, dureza da água e natureza do sal de metal usado no processo de biossorção. Ajustaram-se quatro modelos de equilíbrio – Langmuir, Freundlich, Redlich-Peterson e Langmuir-Freundlich – aos resultados experimentais tendo-se obtido parâmetros estatisticamente significativos para os modelos de Langmuir e Freundlich. Para um nível de confiança de 95% qualquer dos dois modelos descreve adequadamente os resultados experimentais. A eliminação de metais pesados em solução aquosa por biossorção em musgos aquáticos revelou-se um processo interessante, podendo ser aplicado na purificação de águas residuais industriais contendo metais. A capacidade máxima de biossorção de qualquer um dos iões metálicos é elevada, apresentando valores da mesma ordem de grandeza ou mesmo superiores aos obtidos com outros biossorventes.
- Advanced treatment of pomace olive oil wastewater through peroxy-electrocoagulationPublication . Martins, Ramiro; Grabowski, TaisThe extraction of olive pomace oil is a significant aspect of the Mediterranean edible oil industry; however, the wastewater generated contains pollutants that can harm the environment and public health. In this study, peroxi-electrocoagulation (PEC) with aluminum electrodes was used to treat wastewater and reduce pollutant concentrations. A Box-Behnken Design study was conducted to investigate the relationship between hydrogen peroxide dosage, electric current density, and initial pH in the PEC process, and the removal of chemical oxygen demand (COD) and total phenolic compounds (TPh). The study found that the PEC process could remove an average of 22% of COD and 82% of TPh, with the highest removal obtained with hydrogen peroxide dosages of 30 g L -1 and 20 mA cm -2. However, pre-treatment with other processes is necessary to reduce harmful elements in the effluent before undergoing biological treatment.
- Anaerobic digestion in the fruit waste disposal and valorizationPublication . Baumguertner, Matheus Maranho; Kreutz, Cristiane; Martins, RamiroIt is estimated that around 25% of kiwi fruit production is disposed of as waste. This problem has created an opportunity to evaluated the potential for biogas generation using kiwi waste as a substrate by the anaerobic process, a complex biologic treatment performed in the absence of oxygen, used to stabilize organic matter while producing biogas. Eight distinct assay were performed, were carried out in two batch reactors (R1 and R18). Different substrate/inocu-lum ratios, addition of NaHCO3 and with and without nutrients addition being tested. The most satisfactory results were obtained with: kiwi waste (8.4 g), anaerobic digester slurry (192 mL), sodium bicarbonate (500.4 mg), ammonium chloride (453.0 mg) and potassium phosphate mon-obasic (106.0 mg) added. In this assay, 759.1 mL biogas / g VS was produced and methane quality of 60%.
- Anaerobic digestion performance in the energy recovery of kiwi residuesPublication . Paulista, Larissa Oliveira; Boaventura, Rui; Martins, RamiroWorld production and trade of fruits generate losses in the harvest, post-harvest, handling, distribution and consumption phases, corresponding to 6.8% of total production. These residues present high potential as a substrate for the anaerobic digestion process and biogas generation. Thus, the energy valuation of the agro-industrial residues of kiwifruit production was evaluated by anaerobic digestion, aiming at optimizing the biogas production and its quality. Ten assays were carried out in a batch reactor (500 mL) under mesophilic conditions and varying a number of operational factors: different substrate/inoculum ratios; four distinct values for C: N ratio; inoculum from different digesters; and inoculum collected at different times of the year. The following parameters were used to control and monitor the process: pH, alkalinity, volatile fatty acids (VFA), volatile solids (VS) and chemical oxygen demand (COD). Among the tests performed, the best result obtained for the biogas production corresponded to the use of 2 g of substrate and 98 mL of inoculum of the anaerobic digester of the Wastewater Treatment Plant (WWTP) of Bragança, with addition of 150 mg of bicarbonate leading to a production of 1628 L biogas.kg-1 VS (57% methane). In relation to the biogas quality, the best result was obtained with 20 g of substrate and 380 mL of inoculum from the anaerobic digester sludge of Ave WWTP (plus 600 mg of sodium bicarbonate), presenting a value of 85% of CH4, with a production of 464 L biogas.kg-1 VS.
- Anaerobic digestion performance in the energy recovery of kiwi residuesPublication . Martins, Ramiro; Boaventura, Rui; Paulista, Larissa OliveiraWorld production and trade of fruits generate losses in the harvest, post-harvest, handling, distribution and consumption phases, corresponding to 6.8% of total production. These residues present high potential as a substrate for the anaerobic digestion process and biogas generation. Thus, the energy valuation of the agro-industrial residues of kiwi production was evaluated by anaerobic digestion, aiming at optimizing the biogas production and its quality. Ten assays were carried out in a batch reactor (500 mL) under mesophilic conditions and varying a number of operational factors: different substrate/inoculum ratios; four distinct values for C: N ratio; inoculum from different digesters; and inoculum collected at different times of the year. The following parameters were used to control and monitor the process: pH, alkalinity, volatile fatty acids (VFA), volatile solids (VS) and chemical oxygen demand (COD). Among the tests performed, the best result obtained for the biogas production corresponded to the use of 2 g of substrate and 98 mL of inoculum of the anaerobic digester of the Wastewater Treatment Plant (WWTP) of Bragança, with addition of 150 mg of bicarbonate leading to a production of 1628 L biogas.kg-1 VS (57% methane). In relation to the biogas quality, the best result was obtained with 20 g of substrate and 380 mL of inoculum from the anaerobic digester sludge of WWTP of Ave (with addition 600 mg of sodium bicarbonate), presenting a value of 85% of CH4, with a production of 464 L biogas.kg-1 VS.
- Aplicabilidade do musgo aquático fontinalis antipyretica na bioacumulaçãode iões metálicos (Cd2+)Publication . Martins, Ramiro; Vilar, Vítor J.P.; Boaventura, RuiCom este estudo pretende-se compreender quantitativa e qualitativamente a acumulação e a libertação de iões cádmio em solução aquosa, por uma briófita aquática - Fontinalis antipyretica – na perspectiva duma aplicação, quer na biomonitorização de cursos de água, quer na descontaminação de efluentes industriais. A acumulação de cádmio e posterior eliminação pelo musgo foi estudada em laboratório expondo as plantas a concentrações de cádmio na gama 0,5 – 2,5 mg l-1, durante um período de contaminação de 144 h, e depois a água isenta de metal durante um período de descontaminação de 192 h. Foi ajustado um modelo cinético de transferência de massa de primeira ordem aos dados experimentais.
- Application of aquatic mosses to decontaminate industrial effluentsPublication . Martins, Ramiro; Boaventura, RuiAs biosorption is a low cost and effective method for treating metal-bearing wastewaters, understanding the process kinetics is relevant for design purposes. In the present study, the performance of the aquatic moss Fontinalis antipyretica for removing cadmium and lead from simulated wastewaters has been evaluated. Five kinetic models (first-order, pseudo-first-order, Elovich, Ritchie second-order and pseudo- second-order) were fitted to the experimental data and compared. Previously, the effect of parameters such as the initial solution pH, contact time, and initial metal ion concentration on biosorption was investigated using a sorbent dose of 2 g l-1. The initial pH of the solution was found to have an optimum value in the range of 4.0-6.0. The equilibrium sorption capacity of cadmium and lead by Fontinalis antipyretica increased with the initial metal concentration. For an initial metal concentration of 10 mg l-1, the uptake capacity of the moss, at equilibrium, is the same for both metals (4.8 mg g-1). Nevertheless, when the initial concentration increases up to 100 mg l-1, the uptake of Pb(II) is higher than 78%. The pseudo-second order biosorption kinetics provided the better correlation with the experimental data .
- Assessing surface water contamination by toxic metals via bioindicators: public health implicationsPublication . Martins, RamiroThis study presents the results of heavy metal concentrations in aquatic mosses collected from the Ave River Basin during two field surveys (campaigns II and III) and a comparison with data from a field survey carried out 15 years earlier (campaign I). The findings indicated high levels of chromium in the samples from the two previous campaigns, along with aggravated contamination of cadmium, lead, and zinc compared to campaign I. The order of metal accumulation in the moss samples, from highest to lowest, was Fe > Zn > Cu > Cr > Ni > Pb > Cd > Hg. The Metal Pollution Index (MPI) revealed changes in contamination levels between campaigns. Most stations experienced a decrease in classification due to increased water flow and reduced accumulation during Campaign II. The contamination patterns suggest the influence of industrial activities, particularly metal coating facilities. Monitoring and mitigation efforts are necessary to address persistent heavy metal pollution in the Ave River Basin.
- Assessing the influence of oil and grease and salt content on fish canning wastewater biodegradation through respirometric testsPublication . Cristovão, Raquel; Pinto, Vera; Martins, Ramiro; Loureiro, José M.; Boaventura, RuiFish canning industry wastewaters have high organic matter, oil and grease and salt (NaCl) content, which make difficult a proper treatment before discharge. In this work, their treatment was evaluated via activated sludge aerobic biological process through respirometric tests. Inhibition was found to be significant for NaCl concentr ations higher than 17.5 g/L. On the other hand, the oil and grease content affects the wastewater biodegradability in the same way that the organic matter content expressed as chemical oxygen demand: the lower oil and grease and organic matter concentrations, the lower the percentage of wastewater biodegradability. As a final conclusion, the aerobic biological treatment process by activated sludge proved to be appropriate to treat fish canning industrial wastewaters, leading to high organic matter degradation rates (average value of 4900 mg O2 /g COD .d). Additionally, the experimental results achieved with the respirometric tests may be useful for the design of activated sludge plants to treat this type of wastewaters.