Andréa Moura Bernardes

Printed wiring boards for mobile phones: Characterization and recycling of copper

The popularization of mobile phones, combined with a technological evolution, means a large number of scrap and obsolete equipment are discarded every year, thereby causing economic losses and environmental pollution. In the present study, the printed wiring boards scrap of mobile phones were characterized in order to recycle some of the device components, using techniques of mechanical processing, hydrometallurgy and electrometallurgy. The use of the techniques of mechanical processing (milling, particle size classification, magnetic and electrostatic separation) was an efficient alternative to obtain a concentrated fraction (mainly iron in the magnetic fraction and copper in the conductive fraction) and another fraction containing polymers and ceramics. At the end of mechanical processing, a concentrated fraction of metals could be obtained with an average concentration of 60% copper. This concentrated fraction in metals was dissolved in aqua regia and sent to electrowinning to recover 92% of the dissolved copper. The obtained cathodes have a copper content above 95%, which demonstrates the technical feasibility of recovery of copper using the techniques of mechanical processing, hydrometallurgy and electrometallurgy.

Collection and recycling of electronic scrap: A worldwide overview and comparison with the Brazilian situation

Recycling and the related issue of sustainable development are increasing in importance around the world. In Brazil, the new National Policy on Solid Wastes has prompted discussion on the future of electronic waste (e-waste). Over the last 10 years, different e-waste collection systems and recycling processes have been applied globally. This paper presents the systems used in different countries and compares the world situation to the current Brazilian reality. To establish a recycling process, it is necessary to organize efficient collection management. The main difficulty associated with the implementation of e-waste recycling processes in Brazil is the collection system, as its efficiency depends not only on the education and cooperation of the people but also on cooperation among industrial waste generators, distributors and the government. Over half a million waste pickers have been reported in Brazil and they are responsible for the success of metal scrap collection in the country. The country also has close to 2400 companies and cooperatives involved in recycling and scrap trading. On the other hand, the collection and recycling of e-waste is still incipient because e-wastes are not seen as valuable in the informal sector. The Brazilian challenge is therefore to organize a system of e-waste management including the informal sector without neglecting environmentally sound management principles.

Environmental and technical aspects of the utilisation of tannery sludge as a raw material for clay products

This paper is a report on the results of a feasibility study on the immobilisation of tannery sludge by producing a ceramic product. The main purpose of this work was to test the clays used in the manufacture of a ceramic that could incorporate tannery sludge. The raw materials, tannery sludge and clay, were mixed together in different proportions. The ceramic specimens were characterised with respect to water absorption, porosity, linear shrinkage and transverse rupture strength. Leaching tests, in accord with the Brazilian and German regulations, were done on ceramic bodies made with different additions of sludge. In order to evaluate the possibility of air contamination during the firing process, preliminary studies of air emissions were carried out The mechanical properties of the samples evaluated were similar to those specified for ceramic bricks. All the leaching tests have shown that the main sludge contaminant i.e. chromium, could be immobilised within a finished ceramic product. The studies of air emissions have shown that zinc and chlorine are mainly collected from gas emissions and hence are not immobilised by the ceramic system. The study shows that the properties of the ceramic materials produced are acceptable for applications such as bricks for the building industry.

Using mechanical processing in recycling printed wiring boards

AbstracttAs the number of electronic products in use increases, so does the need to dispose of defective and obsolete equipment, including printed circuit boards. The utilization of mechanical processing in recycling this type of waste enables recovery of the metals and allows components to be separated for proper waste disposal. Mechanical processing allows the recovery of 80% of the metals in printed circuit boards, especially copper, which represents approximately 75% of the metallic fraction.

Collection and recycling of portable batteries: a worldwide overview compared to the Brazilian situation

Around the world there is no doubt about the increasing importance of recycling and the connected issue of sustainable development. In Brazil the new 2000 regulations have prompted society to discuss the future of spent batteries. Worldwide, different battery collection systems and recycling processes have been applied in the last 10 years. This paper presents the options applied in Europe and in the USA and compares the world situation to the current Brazilian reality.

Removal of cadmium and cyanide from aqueous solutions through electrodialysis

The discharge of galvanic industry wastewaters containing heavy metals and cyanide is one of the largest sources of water pollution. The use of the electrodialysis technique for the treatment of a synthetic wastewater containing approximately 0.0089 mol L-1 cadmium and 0.081 mol L-1 cyanide was studied using a five-compartment electrodialysis cell. The results demonstrate that the removal of cadmium and cyanide depends on the applied current density and it is limited by the precipitation of cadmium on the cation-exchange membrane in the diluate central cell compartment.

Degradation of the commercial surfactant nonylphenol ethoxylate by advanced oxidation processes

Four different oxidation process, namely direct photolysis (DP) and three advanced oxidation processes (heterogeneous photocatalysis - HP, eletrochemical oxidation - EO and photo-assisted electrochemical oxidation - PEO) were applied in the treatment of wastewater containing nonylphenol ethoxylate (NPnEO). The objective of this work was to determine which treatment would be the best option in terms of degradation of NPnEO without the subsequent generation of toxic compounds. In order to investigate the degradation of the surfactant, the processes were compared in terms of UV/Vis spectrum, mineralization (total organic carbon), reaction kinetics, energy efficiency and phytotoxicity. A solution containing NPnEO was prepared as a surrogate of the degreasing wastewater, was used in the processes. The results showed that the photo-assisted processes degrade the surfactant, producing biodegradable intermediates in the reaction. On the other hand, the electrochemical process influences the mineralization of the surfactant. The process of PEO carried out with a 250W lamp and a current density of 10mA/cm(2) showed the best results in terms of degradation, mineralization, reaction kinetics and energy consumption, in addition to not presenting phytotoxicity. Based on this information, this process can be a viable alternative for treating wastewater containing NPnEO, avoiding the contamination of water resources.

Preparation and physical characterization of a sulfonated poly(styrene-co-divinylbenzene) and polypyrrole composite membrane

The properties of cation-exchange membranes based on polymeric composites of sulfonated poly(styrene-co-divinylbenzene) and polypyrrole (Ppy) are discussed. The amount of Ppy in the composites depends on the oxidant solution concentration used in the synthesis. Comparing composite membranes, the highest electronic conductivity and the best thermal stability were obtained for the composite membrane with the greatest content of Ppy. The membranes were thermally stable up to 250°C. As could be seen by SEM, Ppy is homogeneously distributed in the sulfonated poly(styrene-co-divinylbenzene) matrix. Consequently, composite membranes swell in water much less than base membrane alone. Ion-exchange capacity (IEC) does not change with pyrrole polymerization.

Influence of ligand exchange on the treatment of trivalent chromium solutions by electrodialysis

The effect of ligand type and the aging of the solution in the transport of trivalent chromium through Nafion 450 ion-exchange membranes was studied. Chromium chloride and sulfate solutions were employed in order to evaluate the transport number and the percent extraction of trivalent chromium ions. Results showed that the aging of the solution has a significant influence in the transport of chromium ions through the membrane, which is attributed to the changes observed in the chromium complexes due to the characteristic ligand exchange reactions. Higher values for the chromium transport parameters were obtained for chloride solutions.

High-impact polystyrene/polyaniline membranes for acid solution treatment by electrodialysis : Preparation, evaluation, and chemical calculation

In this study different membranes were produced, aiming to evaluate their use in electrodialysis. These membranes were produced using conventional polymer (high-impact polystyrene) and polyaniline. The membrane characterization was done by FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetry (TGA). The studies of the zinc and proton extraction ionic transport through the membranes were evaluated using a three-compartment cell. The results obtained using the produced membranes were compared to the results obtained with the commercial membrane Nafion 450. It was found that a synthesized membrane can be used to recover zinc in acid media. In addition, a preliminary computational essay about the structures of PAni and CSA is presented.