Jorge Alberto Soares Tenório

Recycling of WEEE: Characterization of spent printed circuit boards from mobile phones and computers

This paper presents a comparison between printed circuit boards from computers and mobile phones. Since printed circuits boards are becoming more complex and smaller, the amount of materials is constantly changing. The main objective of this work was to characterize spent printed circuit boards from computers and mobile phones applying mineral processing technique to separate the metal, ceramic, and polymer fractions. The processing was performed by comminution in a hammer mill, followed by particle size analysis, and by magnetic and electrostatic separation. Aqua regia leaching, loss-on-ignition and chemical analysis (inductively coupled plasma atomic emission spectroscopy - ICP-OES) were carried out to determine the composition of printed circuit boards and the metal rich fraction. The composition of the studied mobile phones printed circuit boards (PCB-MP) was 63 wt.% metals; 24 wt.% ceramics and 13 wt.% polymers; and of the printed circuit boards from studied personal computers (PCB-PC) was 45 wt.% metals; 27 wt.% polymers and ceramics 28 wt.% ceramics. The chemical analysis showed that copper concentration in printed circuit boards from personal computers was 20 wt.% and in printed circuit boards from mobile phones was 34.5 wt.%. According to the characteristics of each type of printed circuit board, the recovery of precious metals may be the main goal of the recycling process of printed circuit boards from personal computers and the recovery of copper should be the main goal of the recycling process of printed circuit boards from mobile phones. Hence, these printed circuit boards would not be mixed prior treatment. The results of this paper show that copper concentration is increasing in mobile phones and remaining constant in personal computers.

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.

Metal separation from mixed types of batteries using selective precipitation and liquid-liquid extraction techniques.

The purpose of this paper is to study metal separation from a sample composed of a mixture of the main types of spent household batteries, using a hydrometallurgical route, comparing selective precipitation and liquid-liquid extraction separation techniques. The preparation of the solution consisted of: grinding the waste of mixed batteries, reduction and volatile metals elimination using electric furnace and acid leaching. From this solution two different routes were studied: selective precipitation with sodium hydroxide and liquid-liquid extraction using Cyanex 272 [bis(2,4,4-trimethylpentyl) phosphoric acid] as extracting agent. The best results were obtained from liquid-liquid extraction in which Zn had a 99% extraction rate at pH 2.5. More than 95% Fe was extracted at pH 7.0, the same pH at which more than 90% Ce was extracted. About 88% Mn, Cr and Co was extracted at this pH. At pH 3.0, more than 85% Ni was extracted, and at pH 3.5 more than 80% of Cd and La was extracted.

Characterization of used alkaline batteries powder and analysis of zinc recovery by acid leaching

This paper discusses the spent alkaline batteries characterization and leaching stage experiments results with sulfuric acid as leachant, as part of a complex system, involving purification and electrolytic stages, aiming the Zn recovery. After dismantling batteries by mineral processing techniques, the black powder sample produced was submitted to X-ray diffraction and atomic absorption spectrophotometry in order to identify its composition. Batch laboratory experiments were conducted for acid leaching procedure to determine appropriate leaching conditions from the viewpoint of maximum zinc extraction. On these tests an amount of dry powder was added to sulfuric acid at different conditions and after leaching and filtration, the aqueous solutions were submitted to atomic absorption spectrophotometry analysis to verify the Zn content.

Use of froth flotation to separate PVC/PET mixtures

Abstract Recycling is an important activity in the minimization of waste that results from human activities. The idea re-using this waste has increased during the last decades due to environmental, economics and social factors. In the United States, 75 billion pounds of plastic are produced every year. Unfortunately, the majority of this plastic ends up in landfills where its decomposition process can take anywhere from 10 to 30 years. The United States currently recycles about 5% of its post-consumer plastic waste; however, as much as 55% could be recycled if economically viable methods can be developed to collect and process waste streams that contain at least 50% thermoplastic materials. Froth flotation is the cheapest and most extensively used process for the separation of chemically similar minerals, and to concentrate ores for economical smelting. Flotation has a reduced cost compared to other separation operations. In this work, froth flotation was used to treat PVC and PET mixtures. The parameters studied are reagents, pH, conditioning time and particle size. The results show a yield of 99.3% pure PVC separated from PET.

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.

Printed circuit board recycling: Physical processing and copper extraction by selective leaching

Global generation of waste electrical and electronic equipment (WEEE) is about 40 million tons per year. Constant increase in WEEE generation added to international legislations has improved the development of processes for materials recovery and sustainability of electrical and electronic industry. This paper describes a new hydrometallurgical route (leaching process) to recycle printed circuit boards (PCBs) from printers to recover copper. Methodology included PCBs characterization and a combined route of physical and hydrometallurgical processing. Magnetic separation, acid digestion and chemical analysis by ICP-OES were performed. On leaching process were used two stages: the first one in a sulfuric media and the second in an oxidant media. The results showed that the PCBs composition was 74.6 wt.% of non-magnetic material and 25.4 wt.% of magnetic one. The metallic fraction corresponded to 44.0 wt.%, the polymeric to 28.5 wt.% and the ceramic to 27.5 wt.%. The main metal was copper and its initial content was 32.5 wt.%. On sulfuric leaching 90 wt.% of Al, 40 wt.% of Zn and 8.6 wt.% of Sn were extracted, whereas on oxidant leaching tests the extraction percentage of Cu was 100 wt.%, of Zn 60 wt.% and of Al 10 wt.%. At the end of the hydrometallurgical processing was obtained 100% of copper extraction and the recovery factor was 98.46%, which corresponds to a 32 kg of Cu in 100 kg of PCB.

Laboratory study of galvanic sludge's influence on the clinkerization process

Abstract This paper presents a laboratory scale simulation that aims to investigate the possibility of partially substituting raw meal with galvanic sludge in cement production. The galvanic sludge used in the experiments, was obtained from the chromium electroplating process; the sludge had Cr as the main heavy metal content. Differential thermal analysis tests were performed using cement raw meal and mixtures of cement raw meal and dry sludge. These mixtures contained 0.25, 0.5, 1.0, 2.0, 3.0, 5.0 and 8.0 wt.% of dry sludge. An apparatus was assembled to simulate the thermal cycle imposed to the charge during the clinker production process. A condenser was inserted into the hot chamber to capture the volatile phases produced. The charge had mixtures containing up to 3.0 wt.% of dry sludge. Samples of the different clinkers produced were submitted to leaching tests: atomic absorption chemical analysis, X-ray diffraction analysis and X-ray fluorescence chemical analysis to characterize the samples. This work showed that chromium emission is not significant during the production process of Portland cement clinker using galvanic sludge additives. The addition of dry sludge of up to 2.0 wt.% of the charge did not affect the formation temperatures of C 2 S (CaO.2SiO 2 ), C 3 S (CaO.3SiO 2 ) and liquid phase. This indicates that the galvanic sludge additions up to 2.0 wt.% did not affect the clinkerization process. The leaching tests showed that total Cr and Cr 6+ concentrations in the solution were below the limits established by Brazilian Standards.

Effect of salt/oxide interaction on the process of aluminum recycling

Abstract The goal of this work was to study the salt/oxide interactions during the process of aluminum recycling in rotary furnaces, which uses salts to protect the burden. Microstructure analysis was the main tool to analyze the morphologies of aluminum dross and its interactions with liquid salt flux; consequently the study was carried out through scanning electron microscope coupled with an energy dispersive X-ray spectrometry detector. Drosses collected from aluminum can recycling industries were used. Tests were carried out using equimolar mixtures of sodium and potassium chlorides. The results revealed that drosses are heterogeneous systems composed essentially of oxides and aluminum. The aluminum oxides develop a chain microstructure, with a high specific surface area, that traps aluminum. The molten salt corrodes this structure and breaks the oxide links, consequently liberating the retained aluminum.

High-temperature oxidation of Al-Mg alloys

The effect of the atmosphere on the oxidation rates of aluminum-can alloyswas studied using thermogravimetric methods. The atmospheres included: air,Ar+1%O2, Ar+5%O2, and CO2. Temperaturesranged from 450 to 800°C. The oxidation rate was influenced by thesurface condition and by the time elapsed after specimen preparation. Increasingtemperature increased the oxidation rate of both AA 3004 and 5182. Parabolickinetics were observed for AA 3004 and linear kinetics were observed forAA 5182 at 450 and 500°C. From 550 to 800°C, parabolic behavior wasobserved for AA 5182. The reduction of free oxygen in the atmosphere reducedthe rate of oxidation. The reactivity of the atmospheres decreased in thefollowing sequence: air, Ar+5%O2, Ar+1%O2, and CO2.