Denise Crocce Romano Espinosa

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.

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.

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.

Determination of Cu and Ni incorporation ratios in Portland cement clinker

Cu and Ni are metals found in galvanic sludges; these sludges are considered hazardous due to their heavy metal content. The main objective of this work is to determine the incorporation amount of Cu and Ni in Portland clinker when a galvanic sludge containing these metals is added to the clinker raw-material. The influence of this addition on the clinkering reactions is evaluated as well as the possibility of co-incinerating galvanic sludges containing Cu and Ni in rotary cement kilns. This study also characterizes the galvanic sludge. Samples were prepared by additions from 0.25 to 5 wt.% of a galvanic sludge to an industrial clinker raw-material. The clinkering process was simulated in a laboratory device. The following techniques were applied to characterize the raw materials and the products of the tests: chemical analysis, differential thermal analysis (DTA) and thermogravimetric analysis (TG). Leaching tests were performed in the produced clinker samples in order to verify the incorporation of the studied metals in the clinker structure. The results led to the conclusion that additions of up to 2 wt.% of a galvanic sludge containing 2.4 wt.%Cu and 1.2 wt.% Ni to clinker raw-material do not affect the clinkering reactions and that these metals are totally incorporated into the clinker.

Characterisation of dusts and sludges generated during stainless steel production in Brazilian industries

Abstract During the stainless steel production process, wastes are generated at the electric arc furnace (EAF) and at the converters. These wastes are a problem for stainless steel industries, for they must be disposed of in controlled landfills. Finding areas to make more landfills is becoming difficult, and new landfills are being placed far from the industries. This leads to an increase in disposal prices and, furthermore, in production prices. Recycling of these wastes, besides solving the disposal and environmental problems, makes it possible to recover valuable metals such as iron, chromium, and nickel. These three metals are needed in stainless steel manufacture and could be returned to the production procedure, hence bringing profit to the industry. It is important, therefore, to develop a recycling process. Waste characterisation is an essential step in the definition of such a process. Four kinds of dust and two kinds of sludge, generated in stainless steel production, were characterised in the present work. The techniques used to characterise the waste were chemical analysis, size separation, density measurement, X-ray diffraction analysis, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) microanalysis. The largest proportion of the dust and sludge particles was of spherical shape. This kind of particle was composed mainly of iron and chromium in the form of a spinel, or of oxides. Precipitation of a secondary phase was identified in some particles.

Thermal behavior of chromium electroplating sludge

Galvanic sludge is classified as a hazardous waste and incineration is one of the techniques used for its treatment. The aim of this work is to study the thermal behavior of a galvanic sludge which contains only chromium as a restriction metal. Simultaneous DTA/TG coupled with mass spectrometer tests were performed to characterize the thermal behavior of the sludge. Besides thermal analysis, sludge samples were heated in a specially designed furnace and these samples were submitted to X-ray diffraction. Vapor from the heated sludge was condensed and the particles were analyzed by EDS microprobe coupled in a scanning electron microscope. The slag formed after the calcination of the galvanic sludge was mainly composed of a mixture of calcium phosphate and fluoride. and minor concentrations of metals. A total weight loss of 34% was observed. The greatest part of this weight loss corresponds to CO2, H2O and SO2. H2O is liberated in the temperature range of 500-1,250 degrees C. CO2 in the range of 500-750 degrees C and SO2 near 1,000 degrees C. Chromium evaporation was not observed in relevant quantities, about 99.6% of the Cr remained incorporated in the slag.