Otávio da Fonseca Martins Gomes

Copper extraction from coarsely ground printed circuit boards using moderate thermophilic bacteria in a rotating-drum reactor

The current work reports on a new approach for copper bioleaching from Printed Circuit Board (PCB) by moderate thermophiles in a rotating-drum reactor. Initially leaching of PCB was carried out in shake flasks to assess the effects of particle size (-208μm+147μm), ferrous iron concentration (1.25-10.0g/L) and pH (1.5-2.5) on copper leaching using mesophile and moderate thermophile microorganisms. Only at a relatively low solid content (10.0g/L) complete copper extraction was achieved from the particle size investigated. Conversely, high copper extractions were possible from coarse-ground PCB (20mm-long) working with increased solids concentration (up to 25.0g/L). Because there was as the faster leaching kinetics at 50°C Sulfobacillus thermosulfidooxidans was selected for experiments in a rotating-drum reactor with the coarser-sized PCB sheets. Under optimal conditions, copper extraction reached 85%, in 8days and microscopic observations by SEM-EDS of the on non-leached and leached material suggested that metal dissolution from the internal layers was restricted by the fact that metal surface was not entirely available and accessible for the solution in the case of the 20mm-size sheets.

Magnetic properties of Fe–Cu alloys prepared by pulsed electrodeposition

FexCu100−x metastable alloys were prepared by pulsed electrodeposition for 5 50) are reminiscent of those observed in Fe–Cu alloys prepared by other methods. The Curie temperature decreases regularly with decreasing x. In the Fe-poor alloys (x≤30), the observed properties indicate that Fe-rich clusters form within a Cu-rich matrix. In the x=10 alloy, the Fe clusters are found to be superparamagnetic at room temperature, but a superferromagnetic order develops below a critical temperature of about 120 K. It is suggested that the intercluster coupling is mediated by Ruderman–Kittel–Kasuya–Yosida interactions which are predominantly positive due to the very short intercluster distances.

Influence of Recycled Aggregate on the Rheological Behavior of Cement Mortar

In this work it was studied the influence of recycled fine aggregate obtained from construction and demolition waste (CDW) on the rheological properties of Portland cement mortars. The CDW was initially separate in their main constituents (mortar, ceramic and concrete debris) at the laboratory and then grinded separately to the sand size in order to generate more homogeneous fine aggregates. The characterization of the natural and recycled sands was carried out through physical tests, X-ray diffraction, scanning electron microscopy (SEM), and image analysis (shape and texture description parameters). A conventional mortar and three mortars containing recycled sands were produced with a sand/cement ratio of 4 and consistency index of 255±5 mm. The consistency was kept constant by ranging the water-cement ratio from 0.58 to 1.14. The rheological study was performed using a rotating viscometer to obtain torque-rotation ratio and to calculate the yield stress and plastic viscosity. The results indicate that the presence of recycled aggregate causes a lowering of both yield stress and plastic viscosity with respect to the mortar containing natural aggregate.

Morphological Characterization of Natural and Artificial Sands Through Image Analysis

This article proposes a simple methodology for the morphological characterization of sand particles through scanning electron microscopy (SEM) and image analysis. It was tested on comparison of natural sands, and artificial sands composed by construction and demolition waste (CDW) from mortar, ceramic, and concrete.The samples were segregated by a sieve series, mounted with epoxy resin and subsequently ground and polished. For each sample, at least 500 particles were imaged.The particles were segmented and a morphological separation method was employed to disconnect touching particles. Then, shape and texture description parameters were measured for each particle.The samples of natural sands presented a particle shape slightly more rounded, as described in the literature. On the other hand, the textures of natural and artificial sands were clearly different. The particles of artificial sands were mainly agglomerates of particles, sometimes composed by different minerals. Besides, they exhibited much more pores.

Multimodal Microscopy for Ore Characterization

Modern microscopes of all kinds (optical, electron, scanning probe) are controlled by software and have digital image acquisition. This setup allows many integrated tasks to be run under the control of automation routines like, for instance, specimen scanning and automatic focusing. Additionally, some microscopes can be fully automated. Thus, it is possible to integrate specimen scanning, image acquisition and storage, processing, analysis and report generation in a single routine.

Characterization of iron ore pellets by multimodal microscopy and image analysis

A correlative approach employing optical microscopy and scanning electron microscopy is proposed for the quantification of phases and pores in iron ore pellets. Combining mosaic images covering the full cross-sections of pellets, obtained with both techniques, it is possible to improve the discrimination of pores, quartz and silicates. First, the images must be carefully registered to show the exact same regions. The procedure for registration, discrimination and quantification was developed with Fiji open source software. A qualitative and quantitative analysis confirmed the advantages of the correlative method as compared to the individual techniques.