Francisco Wendel Batista de Aquino

Analysis of the polymeric fractions of scrap from mobile phones using laser-induced breakdown spectroscopy: Chemometric applications for better data interpretation

Because of their short life span and high production and consumption rates, mobile phones are one of the contributors to WEEE (waste electrical and electronic equipment) growth in many countries. If incorrectly managed, the hazardous materials used in the assembly of these devices can pollute the environment and pose dangers for workers involved in the recycling of these materials. In this study, 144 polymer fragments originating from 50 broken or obsolete mobile phones were analyzed via laser-induced breakdown spectroscopy (LIBS) without previous treatment. The coated polymers were mainly characterized by the presence of Ag, whereas the uncoated polymers were related to the presence of Al, K, Na, Si and Ti. Classification models were proposed using black and white polymers separately in order to identify the manufacturer and origin using KNN (K-nearest neighbor), SIMCA (Soft Independent Modeling of Class Analogy) and PLS-DA (Partial Least Squares for Discriminant Analysis). For the black polymers the percentage of correct predictions was, in average, 58% taking into consideration the models for manufacturer and origin identification. In the case of white polymers, the percentage of correct predictions ranged from 72.8% (PLS-DA) to 100% (KNN).

Laser-induced breakdown spectroscopy (LIBS) combined with hyperspectral imaging for the evaluation of printed circuit board composition.

In this study, laser-induced breakdown spectroscopy (LIBS) was combined with chemometric strategies (PCA, Principal Component Analysis) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) to investigate the metal composition of a printed circuit board (PCB) sample from a mobile phone. Scanning electron microscopy-EDS was used for two main reasons: it was possible at the same time to visualize the sample surface, craters (made by the laser pulses) and also the chemical composition of the samples. A 30 mm×40 mm area of the mobile phone PCB sample, which was manufactured in 2011, was investigated. In this case, a matrix with 30 rows and 40 columns (1200 points) was analyzed, and 10 pulses were performed at each point. A total of 12,000 emission spectra were recorded in the wavelength range from 186 to 1040 nm. After an initial exploratory investigation using PCA, 18 emission lines were selected (representing the elements Al, Au, Ba, Ca, Co, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Sb, Si, Sn, Ti and Zn) and then normalized by the relative intensities, and a new PCA was calculated with the autoscaled data. For example, Au and Si were mainly observed in the superficial electrical contacts and in the bulk of the PCB, respectively. A second sample (a mouse PCB) was also analyzed and Pb (emission lines 357.273, 363.956, 368.346, 373.994 and 405.780 nm) was identified in the solders. In addition, this element was determined using FAAS (flame atomic absorption spectrometry) and the Pb concentration was around 25% (w/w). This study opens the possibility for improved recycling processes and the chemical investigation of solid samples measuring a few millimeters in dimension without sample preparation.

Method for the production of acrylonitrile–butadiene–styrene (ABS) and polycarbonate (PC)/ABS standards for direct Sb determination in plastics from e-waste using laser-induced breakdown spectroscopy

This study presents a procedure for direct Sb determination in solid e-waste samples (polymers). Polymer standards (acrylonitrile–butadiene–styrene (ABS) and polycarbonate (PC)/ABS) were mixed with dichloromethane solution for homogenization and then dried, milled and sieved. The obtained powder was mixed with Sb2O3 and pressed in a thermopress. A calibration curve (Sb: 0 to 2.6% w/w) was prepared and analysed using LIBS (laser-induced breakdown spectroscopy) and more than 10 000 spectra were obtained. Carbon (247.856 nm) and Sb (259.805 nm) signals were recorded and normalized by their individual norm values. The best results were obtained when using C as the internal standard and the Sb concentration observed in the samples ranged from 0.15 to 0.68% (w/w). Standard addition tests were performed and the recoveries ranged from 63 to 83%.

Obtaining information about valuable metals in computer and mobile phone scraps using laser-induced breakdown spectroscopy (LIBS)

The constant projected increase in electronic-waste (e-waste) generation coupled with the high costs of several raw materials employed by the electronics industry are factors that justify studies regarding new analytical methodologies suitable for applications in recycling centers, industrial facilities and academic laboratories. Longer preparation routines for sample analysis and the diverse physical and chemical characteristics of these materials are challenges frequently encountered during the development of analytical procedures. In this work, laser-induced breakdown spectroscopy (LIBS) was applied to the direct investigation of Au and Ag in computer scraps and in the electromagnetic shielding of mobile phone housings. The results show that this technique can be a useful tool for obtaining information regarding the profiles of these elements at the surface and in the bulk of these materials without preparation steps and for semi-quantitatively evaluating Ag in the type of samples analyzed.

Use of laser-induced breakdown spectroscopy for the determination of polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) concentrations in PC/ABS plastics from e-waste

Due to the continual increase in waste generated from electronic devices, the management of plastics, which represents between 10 and 30% by weight of waste electrical and electronic equipment (WEEE or e-waste), becomes indispensable in terms of environmental and economic impacts. Considering the importance of acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), and their blends in the electronics and other industries, this study presents a new application of laser-induced breakdown spectroscopy (LIBS) for the fast and direct determination of PC and ABS concentrations in blends of these plastics obtained from samples of e-waste. From the LIBS spectra acquired for the PC/ABS blend, multivariate calibration models were built using partial least squares (PLS) regression. In general, it was possible to infer that the relative errors between the theoretical or reference and predicted values for the spiked samples were lower than 10%.

Fast and direct detection of metal accumulation in marine sediments using laser-induced breakdown spectroscopy (LIBS): a case study from the Bay of Cienfuegos, Cuba†

Laser-induced breakdown spectroscopy (LIBS) is an emerging, multi-elemental and green technique, particularly suitable for the direct analysis of solid samples. In this study, thirty-two superficial sediments collected from Cienfuegos Bay in 2011–2013 were analyzed by LIBS without requiring sample digestion. Al, Ca, Fe, K, Mg, Mn, Na and Ti emission lines were detected in all samples. The full LIBS spectra of the samples were subjected to principal component analysis (PCA) and hierarchical cluster analysis (HCA). Most samples showed a similar emission signal pattern, whereas two samples collected in 2012 and another two in 2013 showed anomalously higher emission signals for Na, Mg and Ca, Mg, respectively. In three of the sediments, the impact of external factors on the ecosystem is the presumable cause of the observed anomalies. The combination of LIBS with multivariate data analysis demonstrated a high capacity for the fast detection of anomalous metal compositions in marine sediments.

Determination of Elemental Content in Solder Mask Samples Used in Printed Circuit Boards Using Different Spectroanalytical Techniques

Solder masks are essential materials used in the manufacture of printed circuit boards (PCB). This material protects PCBs against several types of damage and performance failure. In this study, the capabilities of laser-induced breakdown spectroscopy (LIBS) were investigated for the direct analysis of solder masks typically commercialized for homemade PCB production, and inductively coupled plasma–optical emission spectrometry (ICP-OES) was used to obtain a chemical profile for the target analytes Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sb, Sn, and Zn. Inductively coupled plasma–mass spectrometry (ICP-MS) was also employed for the determination of potentially toxic elements, such as As, Cd, Cr, Pb, and Hg. In addition to the qualitative information that may be useful for obtaining the spectral profile related to the raw materials present in solder masks formulations, LIBS was also applied for major elements (Al, Ba, Cu, Fe, Mg, and Zn) determination, but due to the low sensitivity, the obtained results were only semi-quantitative for Ba. Regarding Cd, Cr, Hg, and Pb, the samples analyzed were following the restriction of hazardous substances (RoHS) directive of the European Union.