MARCELO MIYADA REDÍGOLO
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Artigo IPEN-doc 27761 Simple and cost-effective method for microplastic quantification in estuarine sediment2020 - GIMILIANI, GIOVANA T.; FORNARI, MILENE; REDÍGOLO, MARCELO M.; BUSTILLOS, JOSE O.W.V.; ABESSA, DENIS M. de S.; PIRES, MARIA A.F.Sediment is a useful environmental compartment in the evaluation and monitoring of microplastics (i.e., plastic particles between 1 μm and 5 mm in length) in aquatic environments, since 70% of plastic waste is deposited on the ocean floor, in riverbeds, and on the bottom of estuaries. The techniques typically used to separate and quantify microplastics require extensive sample preparation and are often ineffective for estuarine sediment samples. In this study, we present a new method for separating and quantifying microplastics found in estuarine sediment samples. This procedure involves sediment collection, drying, sieving (2.0, 1.0, 0.5 and 0.25 mm mesh sizes), and stereomicroscopic examination of the samples retained in each sieve. The results were measured as microplastic abundance (particles g-1 of sediment). This method allows researchers to estimate total microplastic abundance and distribution at the sieve meshes tested, calculate thread/fiber and fragment proportions, and separate microplastic samples for subsequent Py-GC/MS analysis in order to identify their respective compositions. This method was found to be effective in precluding the need for solvents and reducing the amount of time required for sample preparation. For these reasons, this method is more cost-effective and generates less environmental impact than those currently available.Artigo IPEN-doc 26885 The effect of acid pickling on the corrosion behavior of a cerium conversion-coated AA2198-T851 Al-Cu-Li alloy2020 - KLUMPP, RAFAEL E.; DONATUS, UYIME; ARAUJO, JOAO V.S.; REDÍGOLO, MARCELO M.; MACHADO, CARULINE de S.C.; COSTA, ISOLDAThe effect of acid pickling pretreatments prior to cerium conversion coating process on the corrosion behavior of AA2198-T851 alloy substrates was investigated. Three acid pretreatments were employed: nitric acid (HNO3), phosphoric acid (H3PO4) and sulfuric acid (H2SO4). The cerium conversion coating process was performed using a batch solution composed of cerium nitrate and hydrogen peroxide. Microscopic techniques, electrochemical impedance spectroscopy, polarization resistance and open-circuit potential measurements were employed to investigate the effect of each acid pretreatment. The untreated and nitric acid pretreated substrates presented more defective cerium conversion layers than the substrates treated with phosphoric and sulfuric acids. Accordingly, the corrosion resistance of the untreated and nitric acid-treated substrates was very low, while that of the substrates treated with phosphoric acid and sulfuric acids were greatly improved. The sulfuric acid pickling treatment was the best pretreatment before cerium conversion coating among the investigated pretreatments on the AA2198-T851 Al-Cu-Li alloy.