Analytical and reclamation technologies for identification and recycling of precious materials from waste computer and mobile phones.

Waste electrical and electronic equipment (WEEE) is one of the world's fastest-growing class of waste. WEEE contain a large amount of precious materials that have aroused the interest to develop new recycling technologies. Hence, effective recycling strategies are extremely necessary to promote the proper handling of these materials as well as for environmentally sound recovery of secondary raw resource. This paper reviews important existing methods and emerging technologies in WEEE management, with special emphasis in characterization, extraction and reclamation of precious materials from waste computer and mobile phones. Traditional pyrometallurgical and hydrometallurgical technologies still play a central role in the recovery of metals. More recently, emerging greener recycling technologies using microorganisms (i.e. biometallurgical), plasma arc fusion method and pretreatments (i.e. ultrasound and mechanochemical technologies) combined with other recycling methods (e.g. hydrometallurgical), and using less toxic solvents such as ionic liquids (ILs) and deep eutectic solvents (DESs) have also been attempted to recycle metals from computer and mobile phone scrap. The role of analytical method development, especially using spectroanalytical methods for chemical inspection and e-waste sorting process at industrial applications is also discussed. This confirmed that most direct sampling techniques such as laser-induced breakdown spectroscopy (LIBS) and X-ray fluorescence (XFR) have several advantages over traditional sorting methods including rapid analytical response, without use of chemical reagents or waste generation, and greater reclamation of precious and critical materials in the WEEE stream.

Chemical inspection and elemental analysis of electronic waste using data fusion - Application of complementary spectroanalytical techniques.

This study is focused on the development of analytical methods for characterization of printed circuit boards (PCBs) from mobile phones by direct analysis using three complementary spectroanalytical techniques: laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), laser-induced breakdown spectroscopy (LIBS), and micro X-ray fluorescence spectroscopy (micro-XRF). These techniques were combined with principal component analysis (PCA) to investigate the chemical composition on the surface and depth profiling of PCB samples. The spatial distribution of important base metals (e.g. Al, Au, Ba, Cu, Fe, Mg, Ni, Zn), toxic elements (e.g. Cd, Cr, Pb) as well as the non-metallic fraction (e.g. P, S and Si) from conductive tracks, solder mask and integrated components were detected within the PCB samples. Univariate and multivariate approaches were also performed to obtain calibration models for Cu determination. The results were compared to reference concentrations obtained by inductively coupled plasma-optical emission spectrometry (ICP-OES) after microwave-assisted acid leaching using aqua regia. To this end, two PCB samples (50 × 34 mm2) were cut into small parts of 40 subsamples (10 × 8.5 mm2) and analyzed by ICP-OES and the Cu concentrations ranged from 13 to 45% m m-1. Partial least squares (PLS) regression was used to data fusion of analytical information from LIBS and micro-XRF analysis. The proposed calibration methods for LIBS and micro-XRF were tested for the 40 PCB subsamples, in which the best results were obtained combining both data sources though a low-level data fusion. Root mean square error of cross validation (RMSEC) and recoveries were 3.23% m m-1 and 81-119% using leave-one-out cross validation.

Investigation of pollution history in XKS mining area in China using dendrochronology and LA-ICP-MS.

Past pollution episodes and the intensity of mining activity in a contaminated region can be unraveled, using archived elemental information in tree rings. Elemental dendrochronology can be utilized with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to make a timeline of metal(loid)s uptake in trees. In this study, six tree core samples from five tree species were collected around the XKS antimony mine region in Hunan, China, which is impacted by metal pollution: NM1 shuitong (Camptotheca acuminate L.), M1 shuitong (Camptotheca acuminate L.), G1 xiangchun (Toona sinensis L.), J2 wutong (Firmiana platanifolia L.), BSN kulian (Melia azedarach L.), and MT1 zhang (Cinnamomum camphora L.). Tree cores were dated by counting annual rings, and concentrations of As, Ca, Pb, Sb, and Zn were determined using LA-ICP-MS. Results demonstrate that the highest concentrations of Sb are present in the areas closer to mining activity: NM1 - north mine (shuitong), MT1 - mine tailing site (zhang), and BSN - between south and north mine (kulian) tree cores have average Sb concentrations of 18.8 mg/kg, 13 mg/kg, and 4.8 mg/kg, respectively. In comparison, at the village sites located farther away from the mining areas, G1 xiangchun, J2 wutong, and M1 shuitong have average Sb concentrations of 0.69 mg/kg, 0.57 mg/kg, and 0.66 mg/kg, respectively. NM1 shuitong, G1 xiangchun, and MT1 zhang all have large Sb and Zn peaks around 1986, while BSN kulian has larger Sb peaks slightly later around 1988-1990. J2 wutong has Sb peaks somewhat earlier, at 1977 and 1980. Unlike the others trees, M1 shuitong has greater Sb concentrations in more recent years (2009, 2015-2016) demonstrating Sb pollution.

Five thousand years of bellyaches: Exploring boron concentration in ancient populations of the Atacama Desert.

OBJECTIVES: This study explores whether ancient Atacama Desert populations in northern Chile were exposed to endemic boron contamination. MATERIALS AND METHODS: Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS), we studied 144 strands of ancient mummy hair, ranging from 3000 B.C. to 1500 A.D., excavated from the Lluta, Azapa, and Camarones valleys in northern Chile. We tested whether these ancient populations showed signs of significant boron concentration in hair tissue. RESULTS: On average, all individuals from these valleys showed high boron concentrations, ranging from 1.5 to 4 times above the average boron concentration in contemporary hair (baseline <0.85 µg/g). The boron concentration in mummy hair varied according to the main geographic areas mentioned above. CONCLUSIONS: The rivers of northern Chile have high geogenic boron concentrations. They contain 38 times above the recommended limit for human consumption. Geogenic boron contamination likely played a role in population morbidity and the types of crops that were cultivated in antiquity. The ancient populations were chronically affected by boron overexposure, suggesting that ancient geogenic water contamination should be considered when discussing the biocultural trajectories of ancient populations.

Tissue level distribution of toxic and essential elements during the germination stage of corn seeds (Zea mays, L.) using LA-ICP-MS.

Both essential and toxic metal contaminants impact agricultural crops by bioaccumulation in plants. The goal of this study was to evaluate the tissue-level spatial distribution of metal(loids) in corn seeds (Zea mays, L.) from contaminated corn fields near the Xikuangshan (XKS) antimony mine in Hunan, China, and compared them with corn (Zea mays everta L., popcorn) grown in a farm in Amherst, MA that practices sustainable farming as a control. How toxic and essential metals translocate through the roots and shoots during early stages of germination was also investigated. The cleaned corn seed samples were mounted in resin blocks and longitudinally dissected into thin sections. The laser ablation parameters were optimized, and the instrument was calibrated using tomato leaf standard reference material (NIST SRM 1573a) in a pellet form. Tissue level distributions of metal(loid)s As, Cd, Hg, Sb and Zn in corn seeds collected were determined using (LA-ICP-MS). Seeds from the control farm were germinated and their roots and shoots were analyzed to determine tissue level concentrations and their spatial distributions. It was found that seeds from the XKS mine region in China had higher overall concentration of all elements analyzed due to metal(loids) absorbed from contaminated mine soils. Metal(loids) concentrations were highest in the embryo (∼360 mg/kg) and pericarp (∼0.48 mg/kg) compared with the endosperm of corn seeds. Essential element Zn was found in the embryo and emerging coleoptile and radicle. Finally, in both roots and shoots, element concentrations were highest proximally to the tip cap compared to distal concentrations and later translocated to distal tissue regions. This study offers unique insights of metal(loid) bioaccumulation and translocation in corn and thus is better able to track metal(loids) contaminants trafficking in our food systems.

Depth-dependent variations of dissolved organic matter composition and humification in a plateau lake using fluorescence spectroscopy.

In aquatic systems, dissolved organic matter (DOM) plays an important role in regulating the reactivity and transport of environmental pollutants. Fluorescence excitation-emission matrix (EEM) analysis combined with fluorescence regional integration (FRI) and parallel factorial analysis (PARAFAC) were applied to investigate the composition, humification degree and depth-dependent variation of DOM in Lake Baihua, China. The results showed that humic-like materials with more than 60% of percentage fluorescence response (Pi,n) were dominant in DOM. The molecular complexity and structural condensation of PARAFAC components showed the order of C1 (humic-like components) > C3 (protein-like components) > C4 (fulvic-like components) > C2 (fulvic-like components). The lower maximum fluorescence intensities (Fmax) of components in surface layers were attributed to photo-oxidation of DOM by radiation. With depths less than 16 m, the Fmax increases and decreases were attributed to accumulation of recalcitrant humic substances and microbial/abiotic degradation of particulate DOM, respectively. A combination of biological and humification indices could be used as indicators for distinguishing different degrees of humification and sources of DOM. DOM from Lake Baihua mainly originated from an aquatic bacterial source that consisted of an important/intermediate autochthonous component with a weak humic character. The fluorescence indices of PI,n/PII,n, PI+II+IV,n/PIII+V,n, C2, C1/C2 and C2/(C3+C4) were more suitable to determine the humification degree. Stronger humic characters and higher humification degree for DOM were present at depths of 10-13 m. The fluorescence spectroscopy combined with fluorescence indices is convenient to investigate depth-dependent DOM characteristics and to assess water quality or pollution risk in lake systems.

Living in poisoning environments: Invisible risks and human adaptation.

This article describes the hidden natural chemical contaminants present in a unique desert environment and their health consequences on ancient populations. Currently, millions of people are affected worldwide by toxic elements such as arsenic. Using data gathered from Atacama Desert mummies, we discuss long-term exposure and biocultural adaptation to toxic elements. The rivers that bring life to the Atacama Desert are paradoxically laden with arsenic and other minerals that are invisible and tasteless. High intake of these toxic elements results in severe health and behavioral problems, and even death. We demonstrate that Inca colonies, from Camarones 9 site, were significantly affected by chemical contaminants in their food and water. It appears however, some modern-day Andean populations resist the elevated levels of arsenic exposure as a result of positive selection mediated via the arsenic methyltransferase enzyme and display more tolerance to high chemical doses. This article further debate the effects of natural pollution and biocultural adaptation of past populations.

Propellant's differentiation using FTIR-photoacoustic detection for forensic studies of improvised explosive devices.

The use of propellant for making improvised explosive devices (IED) is an incipient criminal practice. Propellant can be used as initiator in explosive mixtures along with other components such as coal, ammonium nitrate, sulfur, etc. The identification of the propellant's brand used in homemade explosives can provide additional forensic information of this evidence. In this work, four of the most common propellant brands were characterized by Fourier-transform infrared photoacoustic spectroscopy (FTIR-PAS) which is a non-destructive micro-analytical technique. Spectra shows characteristic signals of typical compounds in the propellants, such as nitrocellulose, nitroglycerin, guanidine, diphenylamine, etc. The differentiation of propellant components was achieved by using FTIR-PAS combined with chemometric methods of classification. Principal component analysis (PCA) and soft independent modelling of class analogy (SIMCA) were used to achieve an effective differentiation and classification (100%) of propellant brands. Furthermore, propellant brand differentiation was also assessed using partial least squares discriminant analyses (PLS-DA) by leave one out cross (∼97%) and external (∼100%) validation method. Our results show the ability of FTIR-PAS combined with chemometric analysis to identify and differentiate propellant brands in different explosive formulations of IED.

Biodegradation of Tributyltin (TBT) by Extremophile Bacteria from Atacama Desert and Speciation of Tin By-products.

Biodegradation of tributyltin (TBT) by four tin resistant Gram negative bacteria isolated from extremely contaminated river sediments in the Atacama Desert in Chile was studied. Moraxella osloensis showed the greatest resistance and degradation capability of TBT, producing less toxic by-products, such as dibutyltin (DBT) and inorganic tin. In 7 days, approximately 80 % of TBT degradation was achieved, generating close to 20 % of DBT as degradation product. The degradation rate constant (k) was 0.022 [day(-1)] and TBT half-life (t1/2) in culture was 4.3 days. Debutylation is stated a probable mechanism of TBT degradation.

Urinary arsenic speciation profile in ethnic group of the Atacama desert (Chile) exposed to variable arsenic levels in drinking water.

Ethnic groups from the Atacama Desert (known as Atacameños) have been exposed to natural arsenic pollution for over 5000 years. This work presents an integral study that characterizes arsenic species in water used for human consumption. It also describes the metabolism and arsenic elimination through urine in a chronically exposed population in northern Chile. In this region, water contained total arsenic concentrations up to 1250 µg L(-1), which was almost exclusively As(V). It is also important that this water was ingested directly from natural water sources without any treatment. The ingested arsenic was extensively methylated. In urine 93% of the arsenic was found as methylated arsenic species, such as monomethylarsonic acid [MMA(V)] and dimethylarsinic acid [DMA(V)]. The original ingested inorganic species [As(V)], represent less than 1% of the total urinary arsenic. Methylation activity among individuals can be assessed by measuring primary [inorganic As/methylated As] and secondary methylation [MMA/DMA] indexes. Both methylation indexes were 0.06, indicating a high biological converting capability of As(V) into MMA and then MMA into DMA, compared with the control population and other arsenic exposed populations previously reported.

Elemental bioimaging of tissue level trace metal distributions in rice seeds (Oryza sativa L.) from a mining area in China.

Rice is a staple food and major source of nutrients, but it also bioaccumulates toxic elements. In this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine tissue-level trace metal spatial distribution in rice (Oryza sativa) seeds from the active Xikuangshan Sb mine area in China. Whole grain quantified elemental bioimages showed the highest concentration of Zn (1755 mg/kg) in the embryo andmicro zones of elevated Sb, As, Pb, Cd as high as 280, 57, 31 and 830 mg/kg, respectively on the husk/bran/endosperm tissues. Bioimages suggest that both Sb and Cd may be competing with Zn for binding sites. Both Sb(III) and Sb(V) species were detected in seeds from upstream and downstream fields indicating the presence of toxic Sb(III). Brown rice is a good source of Zn, but white rice is a safer option if rice is grown in a polluted area.

Investigation of gold nanoparticles uptake and their tissue level distribution in rice plants by laser ablation-inductively coupled-mass spectrometry.

The tissue level uptake and spatial distribution of gold nanoparticles (AuNPs) in rice (Oryza sativa L.) roots and shoots under hydroponic conditions was investigated using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Rice plants were hydroponically exposed to positively, neutrally, and negatively charged AuNPs [AuNP1(+), AuNP2(0), AuNP3(-)] with a core diameter of 2 nm. Plants were exposed to AuNPs having 1.6 mg Au/L for 5 days or 0.14 mg Au/L for 3 months to elucidate how the surface charges of the nanoparticles affects their uptake into living plant tissues. The results demonstrate that terminal functional groups greatly affected the AuNP uptake into plant tissues. Au concentration determined by LA-ICP-MS in 5 day treated rice roots followed this order: AuNP1(+) > AuNP2(0) > AuNP3(-) but this order was reversed for rice shoots, indicating preferential translocation of AuNP3(-). Bioimages revealed distributions of mesophyll and vascular AuNP dependent on organ or AuNP concentration.

Imaging of metal bioaccumulation in hay-scented fern (Dennstaedtia punctilobula) rhizomes growing on contaminated soils by laser ablation ICP-MS.

Understanding Pb removal from the translocation stream is vital to engineering Pb hyperaccumulation in above ground organs, which would enhance the economic feasibility of Pb phytoextraction technologies. We investigated Cu, Pb, Sb and Zn distributions in Hay-scented fern (Dennstaedtia punctilobula) rhizomes on shooting range soils by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), analyzing digested rhizomes, stems, and fronds using ICP-MS. Nutrients Cu and Zn concentrated in fronds while toxic elements Pb and Sb did not, showing potential Pb and Sb sequestration in the rhizome. Frond and rhizome concentration of Pb was 0.17 ± 0.10% and 0.32 ± 0.21% of dry biomass, respectively. The 208Pb/13C and 121Sb/13C determined by LA-ICP-MS increased from inner sclerotic cortex to the epidermis, while Pb concentrated in the starchy cortex only in contaminated sites. These results suggest that concentration dependent bioaccumulation in the rhizome outer cortex removes Pb from the vascular transport stream.

Antimony, arsenic and mercury in the aquatic environment and fish in a large antimony mining area in Hunan, China.

Antimony (Sb) has received increasing attention recently due to its toxicity and potential human carcinogenicity. In the present work, drinking water, fish and algae samples were collected from the Xikuangshan (XKS) Sb mine area in Hunan, China. Results show that serious Sb and moderate arsenic (As) contamination is present in the aquatic environment. The average Sb concentrations in water and fish were 53.6 + or - 46.7 microg L(-1) and 218 + or - 113 microg kg(-1) dry weight, respectively. The Sb concentration in drinking water exceeded both Chinese and WHO drinking water guidelines by 13 and 3 times, respectively. Antimony and As concentrations in water varied with seasons. Fish gills exhibited the highest Sb concentrations but the extent of accumulation varied with habitat. Antimony enrichment in fish was significantly lower than that of As and Hg.

Dual purpose secondary compounds: phytotoxin of Centaurea diffusa also facilitates nutrient uptake.

Traits that allow more efficient foraging for a deficient resource could increase the competitiveness of a species in resource-poor habitats. Considering the metal-nutrient mobilization ability of many allelochemicals, it is hypothesized that, along with the reported toxic effect on the neighbors, these compounds could be directly involved in resource acquisition by the allelopathic plant. Using nutrient manipulation treatments in hydroponic culture, this hypothesis was tested using Centaurea diffusa, an invasive species that produces the putative phytotoxin 8-hydroxyquinoline (8HQ). The exudation of 8HQ by C. diffusa was very limited and transient. It was further shown that: C. diffusa utilizes 8HQ for its own acquisition of iron, a nutrient deficient in many of its alkaline, invaded habitats; there possibly exists a unique mechanism for the uptake of the 8HQ-complexed iron (Fe) in C. diffusa, which is novel to the nongraminaceous species; although phytotoxic at very low concentrations, the toxic effect of 8HQ showed a conditional response in the presence of metals, and was significantly reduced when 8HQ was complexed with copper (Cu) and Fe. This study, in addition to elucidating one of the possible adaptive mechanisms conferring competitive advantage to C. diffusa, also outlines measures to negate the phytotoxicity of its putative allelochemical. The results indicate that the exudation of 8HQ by C. diffusa could be primarily for nutrient acquisition.

An investigation of inorganic antimony species and antimony associated with soil humic acid molar mass fractions in contaminated soils.

The presence of antimony compounds is often suspected in the soil of apple orchards contaminated with lead arsenate pesticide and in the soil of shooting ranges. Nitric acid (1M) extractable Sb from the shooting range (8300 microg kg(-1)) and the apple orchard (69 microg kg(-1)) had considerably higher surface Sb levels than the control site (<1.5 microg kg(-1)), and Sb was confined to the top approximately 30 cm soil layer. Sb(V) was the principal species in the shooting range and the apple orchard surface soils. Size exclusion chromatography-inductively coupled plasma-mass spectrometry (SEC-ICP-MS) analysis of humic acids isolated from the two contaminated soils demonstrated that Sb has complexed to humic acid molar mass fractions. The results also indicate that humic acids have the ability to arrest the mobility of Sb through soils and would be beneficial in converting Sb(III) to a less toxic species, Sb(V), in contaminated areas.

Distribution of soil arsenic species, lead and arsenic bound to humic acid molar mass fractions in a contaminated apple orchard.

Excessive application of lead arsenate pesticides in apple orchards during the early 1900s has led to the accumulation of lead and arsenic in these soils. Lead and arsenic bound to soil humic acids (HA) and soil arsenic species in a western Massachusetts apple orchard was investigated. The metal-humate binding profiles of Pb and As were analyzed with size exclusion chromatography-inductively coupled plasma mass spectrometry (SEC-ICP-MS). It was observed that both Pb and As bind "tightly" to soil HA molar mass fractions. The surface soils of the apple orchard contained a ratio of about 14:1 of water soluble As (V) to As (III), while mono-methyl (MMA) and di-methyl arsenic (DMA) were not detectable. The control soil contained comparatively very low levels of As (III) and As (V). The analysis of soil core samples demonstrated that As (III) and As (V) species are confined to the top 20 cm of the soil.

Variation in elemental intensities among teeth and between pre- and postnatal regions of enamel.

Microspatial analyses of the trace element composition of dental enamel are made possible using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Fine spatial resolution, multielement capabilities, and minimal sample destruction make this technique particularly well-suited for documenting the distribution of elements in sequentially calcifying layers of enamel. Because deciduous enamel forms from week 13 in utero up to 9 months postnatally (thereafter essentially becoming inert), the application of LA-ICP-MS allows for the retrospective measurement of prenatal and early postnatal trace-element uptake during a critical period of child development. In this study, we compared intra- and intertooth intensities of 25Mg, 57Fe, 66Zn, 68Zn, 88Sr, 138Ba, and 208Pb via LA-ICP-MS of 38 exfoliated deciduous incisors and canines donated by 36 participants in the Solís Valley Mexico Nutrition Collaborative Research Support Program (NCRSP). Pre- and postnatal comparisons within teeth showed significant increases (P < 0.001) and greater variation in the abundance of all isotopes in postnatal enamel, with the exception of a decrease in 25Mg (P < 0.001) and constant values for 88Sr (P = 0.681). Conversely, comparisons by tooth type and mouth quadrant revealed few significant differences between teeth of the same individual. We argue that more variation in the trace element composition of teeth occurs across developmental areas within a tooth than among different teeth of the same person. This study further demonstrates that sequentially calcifying areas of enamel have different chemical concentrations. The results support the use of microspatial analyses of enamel for understanding changes in nutrition, pollution, and residence.

Application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to investigate trace metal spatial distributions in human tooth enamel and dentine growth layers and pulp.

Human tooth enamel provides a nearly permanent and chronological record of an individual's nutritional status and anthropogenic trace metal exposure during development; it might thus provide an excellent bio archive. We investigated the micro-spatial distribution of trace metals (Cu, Fe, Mg, Sr, Pb, and Zn) in 196 x 339 microm2 raster pattern areas (6.6 x 10(4) microm2) in a deciduous tooth using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Ablated areas include prenatal and postnatal enamel, the neonatal line, the dentine-enamel junction (DEJ), dentine, and the dentine-pulp junction. Topographic variations in the surface elemental distribution of lead, zinc, strontium, and iron intensities in a deciduous tooth revealed heterogeneous distribution within and among regions. 43Ca normalized elemental intensities showed the following order: Sr>Mg>>Zn>Pb>Fe>Cu. Elevated zinc and lead levels were present in the dental pulp region and at the neonatal line. This study demonstrates the ability of LA-ICP-MS to provide unique elemental distribution information in micro spatial areas of dental hard tissues. Elemental distribution plots could be useful in decoding nutrition and pollution information embedded in their bio apatite structure.