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Recycling of non-metallic fractions from waste electrical and electronic equipment (WEEE): A review
Abstract
The world's waste electrical and electronic equipment (WEEE) consumption has increased incredibly in recent decades, which have drawn much attention from the public. However, the major economic driving force for recycling of WEEE is the value of the metallic fractions (MFs). The non-metallic fractions (NMFs), which take up a large proportion of E-wastes, were treated by incineration or landfill in the past. NMFs from WEEE contain heavy metals, brominated flame retardant (BFRs) and other toxic and hazardous substances. Combustion as well as landfill may cause serious environmental problems. Therefore, research on resource reutilization and safe disposal of the NMFs from WEEE has a great significance from the viewpoint of environmental protection. Among the enormous variety of NMFs from WEEE, some of them are quite easy to recycle while others are difficult, such as plastics, glass and NMFs from waste printed circuit boards (WPCBs). In this paper, we mainly focus on the intractable NMFs from WEEE. Methods and technologies of recycling the two types of NMFs from WEEE, plastics, glass are reviewed in this paper. For WEEE plastics, the pyrolysis technology has the lowest energy consumption and the pyrolysis oil could be obtained, but the containing of BFRs makes the pyrolysis recycling process problematic. Supercritical fluids (SCF) and gasification technology have a potentially smaller environmental impact than pyrolysis process, but the energy consumption is higher. With regard to WEEE glass, lead removing is requisite before the reutilization of the cathode ray tube (CRT) funnel glass, and the recycling of liquid crystal display (LCD) glass is economically viable for the containing of precious metals (indium and tin). However, the environmental assessment of the recycling process is essential and important before the industrialized production stage. For example, noise and dust should be evaluated during the glass cutting process. This study could contribute significantly to understanding the recycling methods of NMFs from WEEE and serve as guidance for the future technology research and development.
... WEEE is a heterogeneous material stream, including over 1000 substances such as ferrous and non-ferrous metals, glass, hazardous substances (e.g. brominated flameretardants, mercury, lead, cadmium) and plastics (Buekens and Yang, 2014;Wang and Xu, 2014). ...
... Dust, water, and other debris are present in the industrial environment and often in contact with the waste stream (Vermeşan et al., 2020;Wang and Xu, 2014). The presence of such impurities on the surface of particles under analysis by optical sensors poses a major logistic issue, as it has direct impact on spectral shapes and intensities. ...
Polymers represent around 25% of total waste from electronic and electric equipment. Any successful recycling process must ensure that polymer-specific functionalities are preserved, to avoid downcycling. This requires a precise characterization of particle compounds moving at high speeds on conveyor belts in processing plants. We present an investigation using imaging and point measurement spectral sensors on 23 polymers including ABS, PS, PC, PE-types, PP, PVC, PET-types, PMMA, and PTFE to assess their potential to perform under the operational conditions found in recycling facilities. The techniques applied include hyperspectral imaging sensors (HSI) to map reflectance in the visible to near infrared (VNIR), short-wave (SWIR) and mid-wave infrared (MWIR) as well as point Raman, FTIR and spectroradiometer instruments. We show that none of the sensors alone can identify all the compounds while meeting the industry operational requirements. HSI sensors successfully acquired simultaneous spatial and spectral information for certain polymer types. HSI, particularly the range between (1600–1900) nm, is suitable for specific identification of transparent and light-coloured (non-black) PC, PE-types, PP, PVC and PET-types plastics; HSI in the MWIR is able to resolve specific spectral features for certain PE-types, including black HDPE, and light-coloured ABS. Fast-acquisition Raman spectroscopy (down to 500 ms) enabled the identification of all polymers regardless their composition and presence of black pigments, however, it exhibited limited capacities in mapping applications. We therefore suggest a combination of both imaging and point measurements in a sequential design for enhanced robustness on industrial polymer identification.
... Today, superheated water technology is being implanted on the pilot or commercial scale for the recycling of waste plastics [31]. Simultaneously, the economic evaluation of this technology is now being undertaken [32,33]. Wang et al. highlighted that, in the recycling of nonmetallic components from e-waste, superheated water technology and gasification technology have a lower environmental impact than pyrolysis, but their energy consumption is higher [33]. ...
... Simultaneously, the economic evaluation of this technology is now being undertaken [32,33]. Wang et al. highlighted that, in the recycling of nonmetallic components from e-waste, superheated water technology and gasification technology have a lower environmental impact than pyrolysis, but their energy consumption is higher [33]. A drawback of superheated water technology is its energy cost. ...
The mineralization of fluoroelastomers (FKMs) in superheated water in the presence of potassium hydroxide (KOH) was investigated with the aim of developing a methodology for recycling the fluorine element. Two FKMs—an “uncrosslinked FKM”, representing a poly(vinylidene fluoride-co-hexafluoropropylene) (poly(VDF-co-HFP)) copolymer with a VDF/HFP molar ratio of 78/22 and a “crosslinked FKM” consisting of this copolymer (cured by peroxide) and carbon black—were treated. The fluorine content of these FKMs was efficiently transformed into F− ions in the reaction solution using low KOH concentrations (0.10–0.50 M) at 200–250 °C. When the uncrosslinked or crosslinked FKMs reacted with aqueous KOH (0.20 M) at a rather low temperature (200 °C) for 18 h, the fluorine content of these FKMs was completely mineralized (both F− yields were 100%). Although the crosslinked FKM contained carbon black, the fluorine mineralization of the FKM was not inhibited. The addition of Ca(OH)2 to the reaction solutions after the superheated water treatment at 250 °C for 6 h with aqueous KOH (0.50 M) led to the production of pure CaF2, identified using X-ray spectroscopy, with 100% and 93% yields for the uncrosslinked and crosslinked FKMs, respectively.
... The growing consumption of durable and nondurable consumer goods and the associated production of waste materials is alarming global population for taking urgent steps towards more efficient measures in environmental protection [1]. One of the fastest growing wastes is waste electrical and electronic equipment (WEEE) [2]. According to a recent report by Shittu et al., the global WEEE production was 54 million tons (MT) in 2019 which is a rise of 45 MT since 2016 [3]. ...
... While these electronic devices have numerous advantages, they also contribute to a major problem, which is the growing pile of e-waste. According to the World Economic Forum, 50 MT of e-waste are produced each year, but only 20% is recycled, with the remainder often incinerated or dumped in landfills [2][3][4]. ...
In line with the global recognition of waste-to-wealth concept aiming for circular economy, scientific articles are published in greatly increasing number on the eco-friendly and sustainable utilization of carbon nanocomposites. However, control on the structure and properties of waste-derived carbon nanomaterials still requires substantial future research. In this review, recycling materials into nanocomposites containing graphene are narrated by overviewing all the 120 publications currently available in the literature including their pioneering study in 2012 and their recent developments until 2022, focusing on energy-related aspects of functional graphene-based nanocomposites. Interestingly, almost all currently available sources report on composites in which graphene is a high value-added filler or matrix, and only the other phase originates from wastes. Flexibility of process parameters of pyrolysis methods enables the synthesis of biomass-derived graphene composites for virtually any kind of industrial applications. Biomass often acts both as carbon and SiO2 source, while only a few percentages of graphene material induce significant changes in their physicochemical properties. Utilization of wastes for energetic composites increases abruptly due to their outstanding price-to-value ratio and reusability. Future perspectives and current green chemistry or human health related challenges are also discussed to pave ways for new developments using unexplored waste sources.
... 89 However, the content of BFRs might trigger serious environmental pollution when valorization processes require high-temperature thermal treatments. 90 Indeed, the uncontrolled combustion of organic matter may cause the emission of toxic components such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, and polychlorinated dioxins (PCDs) as BFRs degradation products. In this context, pyrolysis has been proposed as a more controlled thermal combustion carried out in the absence of oxygen, which enables materials to be decomposed into smaller molecules potentially of interest as fuels or as precursors for the petrochemical industry. ...
Waste Electrical and Electronic Equipment (WEEE or e-waste) has emerged as a formidable global waste stream, reflecting the mounting demand for technology in our interconnected world. Over the past two decades, besides a world facing a rapid digital, e-mobility, and green energy transition, there has been a growing recognition across the globe, among both society and industries, regarding the hazards and opportunities linked to e-waste management. This collective consciousness has driven the adoption of best practices, including the implementation of circular economy (CE) models, fostering environmentally sustainable production and recycling processes. With a rate of around the 72% of the global population (81 countries) reached by specific regulations by 2023, this review explores the evolving landscape of international legislation and emerging technologies designed for e-waste prevention and valorization, emphasizing low-environmental impact and sustainability. Despite a prolific scientific community (papers published on e-waste grew over 1000 times in the period 2002–2022) and the rise in good practices in different countries, the modest increase of innovation patents (rate of around 50% increase) and the limited number of industrially established innovation processes demonstrates that while the advancing technologies are promising, they remain in an early, embryonic stage. This paper offers a concise review of life cycle assessments from existing literature to underpin the technological advancements discussed. These assessments provide insights into the reduced environmental footprint of various innovative processes aimed at enhancing the circular economy and incorporating them into the emerging concept of safe- and sustainable-by-design. Meanwhile, global e-waste production rose from an estimated 34 Mt in 2010 to 62 Mt in 2022, while documented proper collection and recycling only increased from 8 Mt to 13.8 Mt over the same period. This shows that e-waste generation is growing nearly five times faster than formal recycling. Furthermore, if waste management activities remain at 2022 levels, a projected economic (benefit – costs) deficit of 40 billion USD is expected by 2030. It is time for communities to reverse the trend by expanding good practices and implementing technology-economic-environment sustainable and efficient circular economy models.
... Clean glass fractions can be used as glass cullet in glass production. Commonly, recycled glass from WEEE is used as foam glass or in other low-value applications [57]. Therefore, all glass recycling from WEEE can be considered downcycling. ...
Assessing a given product’s design and its recyclability using mass flow analysis based on the material separation and recovery rates of individual recycling processes under realistic conditions can support design decisions promoting better recyclability. EN 45555 defines the calculation of the technical recyclability of electrical and electronic equipment (EEE). However, the lack of specific recycling rates for material or processes often leads to either too small or too high recyclability values. Herein, an extensive database of such recycling rates is presented. Moreover, the quality of recycling is considered. The typical classification into “recycled” and “lost” is expanded into four categories, namely “circular”, “recycled”, “alternate material recovery” and “lost”. The recycling rate database includes yields for all four categories and covers 30 materials for 14 recycling processes relevant in waste EEE (WEEE) treatment. These data enable a detailed calculation of the recyclability of various EEE for multiple recycling scenarios covering the entire WEEE recycling chain. Fraunhofer IZM performed an internal critical review of the data. The recycling rates database can act as a solid foundation for comparing the recyclability of various electronics in different scenarios and recyclability indices. For example, the recyclability of typical smartphones is investigated comparing different dismantling and recycling scenarios highlighting the potential of both database and methodology.
... Reaction times for microbes to digest target metals is also a major barrier to commercial adoption of biohydrometallurgy. Microbes activity can change and evolve based on environmental conditions such as water purity, operating temperatures and geographic location, with changes to any of these factors making it difficult to replicate and create reproducible outcomes to design an efficient industrial process [93]. Content courtesy of Springer Nature, terms of use apply. ...
Electrical and electronic components, the silent orchestrators of our technological symphony, have been crucial for enabling societal advances. From the simple beginnings of vacuum tubes to the complex circuitry in today’s smartphones, the role and type of electronic components have continued to evolve. The components of electrical and electronic equipment once it has reached the end of its useful life as a product are called electronic waste (e-waste). The exponential growth of electronic devices has made e-waste management an important environmental issue. Improper disposal of e-waste to landfills has serious environmental consequences for the global ecosystem. The majority of discarded e-waste such as computers, mobile phones, televisions, printers, and so on, are embedded with printed circuit boards (PCBs), which are an essential and basic component. PCBs of e-waste contain many different metals including precious metals (Ag, Au, Pd, Pt, etc.), critical elements (Li, Ni, Ga, graphite, rare earth elements, etc.) and non-critical metals (Al and Fe) in varying percentages depending on the electronics. In the emerging era of circular economy recycling, waste printed circuit boards (wPCBs) of any e-waste are seen as an alternative to processing mining ores to meet future metals demand. Different recycling methods such as mechanical separation, pyrometallurgy, hydrometallurgy, biohydrometallurgy, pyrolysis, electrolysis and supercritical fluid technologies have been explored to extract the valuable metals from e-waste. This article aims to provide a critical review of the different recycling routes for e-waste, with a focus on the emerging supercritical fluid technologies (SFT), and their opportunities and challenges. This review will compare the emerging SFTs for existing processes used in industry and other alternative treatment methods. The specific areas of comparison include technical complexity and environmental impacts.
Graphical abstract
... Chemical analyses carried out in areas of inadequate WEEE processing showed the presence of As, Cd, Cr, Hg, and Pb in the soil, water, and sediments (Houessionon et al., 2021). Material recovery practices at informal WEEE recycling sites include open-air burning and acid leaching (Sepúlveda et al., 2010;Wang and Xu, 2014). Uncontrolled, these recovery practices can emit toxic compounds to the air, harming workers and residents in surrounding areas (Cesaro et al., 2019). ...
... Lead, a heavy metal, is highly toxic and can cause symptoms like abdominal pain, neurasthenia, anaemia, and toxic encephalopathy if it accumulates in the body beyond safe levels [31,32]. Recognising its danger to human and environmental health, many countries have regulated lead in electrical items [33,34]. This has spurred global research into lead-free dielectric materials, with notable progress in lead-free FEs [35][36][37], in contrast to the modest advances in leadfree AFEs [18,23,38]. ...
The burgeoning significance of antiferroelectric (AFE) materials, particularly as viable candidates for electrostatic energy storage capacitors in power electronics, has sparked substantial interest. Among these, lead-free sodium niobate (NaNbO3) AFE materials are emerging as eco-friendly and promising alternatives to lead-based materials, which pose risks to human health and the environment, attributed to their superior recoverable energy density and dielectric breakdown strength. This review offers an insightful overview of the fundamental principles underlying antiferroelectricity and the applications of AFE materials. It underscores the recent advancements in lead-free NaNbO3-based materials, focusing on their crystal structures, phase transitions, and innovative strategies devised to tailor their electrostatic energy storage performance. Finally, this review delineates the prevailing challenges and envisages future directions in the realm of NaNbO3-based electrostatic energy storage capacitors, with the goal of fostering further advancements in this pivotal field.
... Reaction using this water is recognized as an environmentally benign technique because it has been shown to have a smaller environmental impact than pyrolysis in the recycling of nonmetallic component from electronic waste. 38 In addition, it allows generating value-added compounds. 39−43 Furthermore, unlike with pyrolysis of fluorinated compounds, even if harmful COF 2 is generated during the treatment, it is easily decomposed by hydrolysis to CO 2 and HF. ...
Lithium bis(pentafluoroethanesulfonyl)imide, Li[N(SO2C2F5)2], a typical fluorochemical aimed at better electrochemical performance of battery electrolytes, in superheated water was studied for its waste treatment. When Li[N(SO2C2F5)2] was reacted in pure superheated water at 300 °C, little F– ions were produced. In contrast, complete mineralization of the fluorine, sulfur, and nitrogen atoms in Li[N(SO2C2F5)2] was achieved when the reaction was performed in the presence of KMnO4. Specifically, when Li[N(SO2C2F5)2] was treated for 18 h with 158 mM of KMnO4, the F– and SO42– yields were 101 and 99%, respectively, and the sum of the NO3– and NO2– yields was 101%. In the gas phase, trace CO2 was detected and no CHF3, which has high global warming potential, was formed. Furthermore, the fluorine, sulfur, and nitrogen atoms in the analogues K[N(SO2C4F9)2] and K[N(SO2CF2)2CF2] also underwent complete mineralization using the same approach.
... Primitive waste electrical and electronic equipment (WEEE) management activities have generated releases of POP-BFRs, elemental pollutants, and brominated dioxins and furans (Duan et al., 2016;Lopez et al., 2011;Wannomai et al., 2020;Wei et al., 2016;Zhang et al., 2017). To prevent these releases, several techniques have been researched (Lucas et al., 2018(Lucas et al., , 2017Ragaert et al., 2017;Wang and Xu, 2014). For POP-BFRs, environmentally sound management has been proposed by the Stockholm Convention (Stockholm Convention, 2021). ...
Research to prevent releases of brominated flame retardants listed as persistent organic pollutants by the Stockholm Convention (POP-BFRs) was conducted through an international cooperation project in Colombia. Six waste electrical and electronic equipment (WEEE) management facilities implemented: 1) sorting e-waste by product type and color (black, white, and other; henceforth called chromoproducts), 2) sampling test products and their plastic fraction (called sets, separated by polymer type), 3) monitoring mass, bromine and antimony contents by hand-held X-ray fluorescence (XRF) and POP-BFRs such as polybrominated diphenyl ethers (PBDEs) by gas chromatography and mass spectrometry (GC-MS), and 4) differentiated treatment according to categories that used the Restriction of Hazardous Substances in Electrical and Electronic Equipment Directive (RoHS) hazardousness threshold of 1000 mg ∑ PBDEs/kg. This scheme led to the proposal of a methodology for WEEE management called the "chromoproduct approach". 994,230 products were managed and grouped into 222 chromoproducts, from which 77 were analyzed: 50 below RoHS hazardousness (BRH), 16 above RoHS haz-ardousness (ARH), and 11 unknown RoHS hazardousness (URH). XRF indicators using bromine and antimony contents could rule out pollution in BRH chromoproducts; however, categorization still required GC-MS. One ARH plastics sample had 3620 mg ∑ PBDEs/kg, while no POP-BFRs were found in the BRH plastics sample. The implementation of the chromoproduct approach traced 153.6 tonnes of ARH plastics. BRH plastics composition was estimated and used in a pilot-scale closed-loop economic activity. The chromoproduct approach seems promising for avoiding POP-BFR releases and promoting the upcycling of recyclable e-waste plastics.
... The composition of WEEE is non-homogeneous and can contain more than 1000 different substances, in which ferrous and non-ferrous metals, plastics, glass, wood and chipboard, printed circuit boards, ceramics, rubber, and other materials can be found. As can be seen in Figure 11.1, approximately 60% of WEEE is mainly composed of metals, followed by plastics with 15%, cathode ray tubes (CRT) and LCD screens with 12%, and the remaining 13% other constituents (Wang and Xu 2014). ...
... So why are these wastes harmful? [8,9] The vast majority of electronic wastes contain substances such as brominated flame retardant, chlorinated solvents, PVC, harmful metals, lead, mercury, beryllium, and cadmium. The dispersal of these substances in the environment as waste causes serious pollution and disrupts natural habitats. ...
All of the electrical and electronic products that no longer work, are unwanted, or have expired are called electronic waste or e-waste. Computers, televisions, mobile phones, fax machines, and printers make up the majority of this waste. So why are these wastes harmful? The recycling of end-of-life products is not only an ecologically necessary issue supported by regulations but also economically interesting because of the use of raw materials and reduced costs. Therefore, electronic waste (e-waste) is now seen as a serious raw material source rather than waste, as it includes materials that have a chance of secondary use as well as recyclable materials. The problem of electronic waste in the world is not separate from the problem of electronic waste in Türkiye. The global electronic waste problem is a whole made up of parts. E-waste is a subject that needs to be read and analyzed from a holistic perspective in Türkiye and the world. In this study, what has been done about e-waste in the world and Türkiye, numerical information is given in detail. Various solution proposals have been tried to be proposed in terms of the e-waste problem in Türkiye.
... Chemical analyses carried out in areas of inadequate WEEE processing showed the presence of As, Cd, Cr, Hg, and Pb in the soil, water, and sediments (Houessionon et al., 2021). Material recovery practices at informal WEEE recycling sites include open-air burning and acid leaching (Sepúlveda et al., 2010;Wang and Xu, 2014). Uncontrolled, these recovery practices can emit toxic compounds to the air, harming workers and residents in surrounding areas (Cesaro et al., 2019). ...
... E-waste, is rapidly becoming one of the swiftest growing waste streams, characterized by its complex material composition (Vadoudi et al., 2015). While it comprises valuable elements such as nickel, gold, copper and rare earth elements (Wang and Xu, 2014;Tansel, 2017), it also contains hazardous substances that can lead to environmental and health hazards if not handled appropriately (Rucevska et al., 2015). Nevertheless, a substantial amount of e-waste is improperly collected and processed, resulting in overall collection levels far below the amount of electrical and electronic equipment leaving the market (Vidal-Legaz et al., 2016). ...
... Finally, the model efficiently removed the glass from other flows of materials (83.33% of recall). This is an important outcome, considering that glass is not a valuable material and only increases the mass of the materials needing treatment [23]. ...
The recycling of waste electrical and electronic equipment is an essential tool in allowing for a circular economy, presenting the potential for significant environmental and economic gain. However, traditional material separation techniques, based on physical and chemical processes, require substantial investment and do not apply to all cases. In this work, we investigate using an image classification neural network as a potential means to control an automated material separation process in treating smartphone waste, acting as a more efficient, less costly, and more widely applicable alternative to existing tools. We produced a dataset with 1,127 images of pyrolyzed smartphone components, which was then used to train and assess a VGG-16 image classification model. The model achieved 83.33% accuracy, lending credence to the viability of using such a neural network in material separation.
... Plastics that are most frequently found in WEEE are HIPS, ABS, blends of ABS-PC, as well as polypropylene (PP), and these are the most promising fractions for plastic recycling to produce new electronics using the metals and polymers recovered from e-waste. (Wang and Xu, 2014;da Silva Müller Teixeira et al., 2021). ...
... E-waste is classified according to the manufacturing material and contains > 1000 different constituents, which fall into two categories, (i) toxic and (ii) non-toxic substances. Extensively, it incorporates ferrous/non-ferrous metals, plastics, glass, printed circuit boards (PCB), cement, ceramic, rubber, etc. (Wang and Xu 2014). E-waste includes around 50% of Fe and steel taken after plastics (21%), non-ferrous metals (13%), and different elements. ...
... E-waste is classified according to the manufacturing material and contains > 1000 different constituents, which fall into two categories, (i) toxic and (ii) non-toxic substances. Extensively, it incorporates ferrous/non-ferrous metals, plastics, glass, printed circuit boards (PCB), cement, ceramic, rubber, etc. (Wang and Xu 2014). E-waste includes around 50% of Fe and steel taken after plastics (21%), non-ferrous metals (13%), and different elements. ...
... WEEE is a heterogeneous material stream, including over 1000 38 substances such as ferrous and non-ferrous metals, glass, hazardous substances (e.g. 39 brominated flame-retardants, mercury, lead, cadmium) and plastics (Buekens and Yang,40 2014; Wang and Xu, 2014). 41 Plastics are the second largest material class in e-waste, accounting for approximately 42 25% of the total WEEE produced worldwide ( calls for the recovery of type-pure material fractions and increased recycling efficiencies, 63 both major challenges when working with diverse waste streams, such as WEEE polymers 64 (Reuter, 2016). ...
... During the melting process the plastics are utilized to produce heat with continuous monitoring of the flue gas, due to the well known issues arising during the plastics burning (Babu et al., 2006;Deuber, 2003;Wang and Xu, 2014). Zinc that originates from the brass contact blades is converted into zinc dust during smelting, and is collected in the plant filters. ...
... The mentioned issues have led to the need to develop sustainable ways of handling WEEE [3,8]. However, most recycling technologies are still at low technology readiness level (TRL) and the environmental impacts are often unknown. ...
Waste electrical and electronic equipment (WEEE) is a particularly difficult waste to manage, characterized by hazardous and valuable chemicals. Emerging chemical recycling technologies are developed to unveil the possibility of sustainable treatment providing valuable resources from WEEE. This study develops a framework for prospective life cycle assessment (LCA) to explore a range of future scenarios in which the technology can be operated with low environmental impact. This is demonstrated in a case study focusing on plastics from WEEE, which are currently predominantly incinerated. The results reveal environmental benefits by WEEE treated via chemical recycling. In terms of climate change impacts, the best‐case scenario of chemical recycling shows a reduction potential of 74 % compared to current treatment.
... Plastics are increasingly used in EEE, which has lowered production costs and resulted in lighter products that are more durable and easily molded when compared to other traditional materials (Tansel, 2017). EEE typically contain around 10 to 30% plastic (Wang and Xu, 2014). High impact polystyrene (HIPS) and acrylonitrilebutadiene-styrene copolymer (ABS) are the most representative polymers in this market (Dimitrakakis et al., 2009;Wäger and Hischier, 2015;Hirayama and Saron, 2018;Teixeira et al., 2021). ...
Introduction
Acrylonitrile-butadiene-styrene copolymer (ABS) and high impact polystyrene (HIPS) are plastics typically found in waste electrical and electronic equipment (WEEE or e-waste). As such, recycling is a beneficial method for reintroducing polymeric materials from electrical and electronic equipment to the same production cycle. This study aimed to investigate mechanical recycling of ABS and HIPS from WEEE reprocessed six times, totaling 24 cycles.
Methods
Reprocessing was performed by extrusion and test specimens were obtained by injection. The technical aspects assessed before and after reprocessing were mechanical properties (tensile, flexural and impact strength), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) and melt flow index (MFI), compared with those of reprocessed virgin polymeric materials. The environmental aspect was evaluated by monitoring energy consumption and solid waste generation during each reprocessing cycle.
Results
Average energy consumption per extrusion and injection cycle was 0.7 and 2.0 kW/kg, respectively. There was a 30% increase in MFI from the first to sixth reprocessing cycle for virgin HIPS (5.5 g/10 min in 200°C and 5 kg), the largest among the polymers. The values for virgin ABS (6.0 g/10 min in 200°C and 5 kg) and ABS and HIPS from WEE increased by 11–15% from the first to sixth cycle. Impact strength was affected from the second reprocessing cycle onwards for ABS e-waste (14% decrease) and in the fifth cycle (16% decrease) for HIPS e-waste.
Discussion
The thermal, tensile and flexural properties of the virgin and post-consumer materials remained almost unchanged as the number of reprocessing cycles increased, indicating that these materials have the potential and properties for reintroduction into the same production cycle.
... In the manufacture of electrical and electronic equipment, side connectors are used to mount the microprocessor and memory chips on the motherboard, and the plug-and-socket connectors used to attach cables contain gold. Gold from such components is generally electroplated onto other metals and alloys containing small amounts of nickel and cobalt used to increase system durability [7][8][9]. ...
Adsorption recovery of precious metals on a variety of solid substrates has steadily gained increased attention in recent years. Special attention was paid to the studies on the characterization of the adsorptive properties of materials with a high affinity for gold depending on the nature of the pendant groups present in the structure of the material. The aim of the present work was to synthesize and characterize a new material by using the sol-gel synthesis method (designated as BCb/CB). In this case, synthesis involved the following precursors: bismuth carbonate (III), carbon black, and IGEPAL surfactant (octylphenoxypolyethoxyethanol). Immobilization of the heterojunction as bismuth oxide over a flexible support such as carbon black (CB) can prevent their elution in solution and make it versatile for its use in a system. In this work, a new adsorbent material based on bismuth carbonate supported over carbon black (BCb/CB) was developed and used further for gold recovery from aqueous solutions. The required material was characterized physically/chemically by scanning electron microscopy (SEM); energy dispersive X-ray spectrometry (EDX); X-ray diffraction (XRD); thermal analysis (DTG/DTA); atomic force microscopy (AFM). The Brunauer–Emmett–Teller (BET) method was used to determine the specific surface area indicating a value of approximately 40 m2/g, higher than the surface of CB precursor (36 m2/g). The adsorptive properties and the adsorption mechanism of the materials were highlighted in order to recover Au(III). For this, static adsorption studies were carried out. The parameters that influence the adsorption process were studied, namely: the pH, the contact time, the temperature, and the initial concentration of the gold ions in the used solution. In order to establish the mechanism of the adsorption process, kinetic, thermodynamic, and equilibrium studies were carried out. Experimental data proved that the gold recovery can be conducted with maximum performance at pH 3, at room temperature. Thermodynamic studies proved that the gold adsorption on BCb/CB material is a spontaneous and endothermal process. The results indicate a total adsorption capacity of 13.1 mg Au(III)/g material. By using this material in real solutions, a recovery efficiency of 90.5% was obtained, concomitant with a higher selectivity (around 95%).
In this study, the generation of domestic waste electrical and electronic equipment (WEEE) and waste printed circuit board (WPCB) were estimated, from 2015 to 2030. Based on the number of EEE put on the Brazilian market, the possession rate in the Brazilian households and obsolescence amounts of five EEE types were estimated using time series. The results show that, between 2015 and 2030, the quantity of WEEE generated per year will increase from 131.87 kt to 195.22 kt. In this period, WPCB generation will stay around 10% of WEEE generation. Additionally, this study shows that the urban mining potential of the materials recoverable from WPCB can be an important revenue source, with environmental benefits deriving from energy savings and a reduction in CO2 emissions. The results of this study provide a quantitative basis that may help decision makers develop strategic policies for WEEE management, considering material circularity.
Graphical abstract
Despite its significance in regulating the global climate and maintaining biodiversity, the vastness of the Amazon geography imposes challenges for its residents, including limited access to electricity. The Luz para Todos Program proposes to universalize access to the public electricity service in remote regions of the Legal Amazon with renewable energy sources. From this perspective, the work assessed the ability of sector agents to meet the demand for universalization of the Luz para Todos Program, the economic aspects involved in the universalization process, and the waste management and reverse logistics of these systems. The findings indicate a demand for up to 15 million photovoltaic modules, batteries, and inverters with a maximum cost exceeding BRL 38 billion (USD 7.4 billion). Over 33 years, between 58 and 234 thousand tons of electronic waste would be generated. The program should change the panorama of installed photovoltaic capacity in the northern region of the country, thus placing considerable demand upon the solar industry to supply equipment for the installation of thousands of standalone systems across a vast territory, generating waste in places with inadequate infrastructure to manage them in an environmentally sensitive manner. The diversification of renewable energy sources could alleviate the burden on the service chain, curtail the waste generated by photovoltaic equipment, and stimulate the development of a service chain in regions gaining access to electricity services.
Economic and environmental considerations have elucidated research interests on the best approach to managing electronic waste (e-waste), which has increasing social, environmental, and economic impacts. Proper e-waste managementis essential for resource recovery, environmental sustainability, and public health protection, and effective management of e-waste necessitates analytical techniques to assess and characterize their elemental composition. Despite expansive literature published on the topic of e-waste, there is scarce coverage of the various analytical techniques employed to characterize the inorganic contents of e-waste. This review discusses the various e-waste characterization techniques used in studies published between 2013 and 2023. Specifically, this review covers the analytical approaches employed to characterize the inorganic content of e-waste, the electronic devices or their components analyzed, the elements identified, the sample preparation methods adopted, and the merits and demerits of the analytical procedures. This review highlights the disparate approaches to e-waste characterization and the need for reliable and repeatable e-waste analysis and sample preparation methods.
Keywords: Analytical characterization; E-waste recycling; Electronic waste.
Published by Elsevier Ltd.
Concrete, a widely used building material, should minimize its environmental impact to align with the construction sector’s Sustainable Development Goals. Researchers worldwide are investigating the possibility of e-waste in building materials incorporating various recyclable elements. This paper conducts a thorough review of research on e-waste as a building material. Various E-waste products are used as fine and coarse aggregate replacements in concrete. The study uses a bibliographic approach with the Scopus database to delve into the literature discussing E-waste in construction materials from 2007 to 2022. Data are extracted specifically from Scopus, which identifies 731 papers based on the keyword “Electronic waste used as building materials”. The second step involves scientometric analysis, which focuses on patterns within the articles, such as the most prolific countries, sources, frequently used keywords, and reports containing relevant research. Each research phase contains a summary of the results obtained at various stages. Detailed quantitative and qualitative discussions are also conducted to achieve the three primary goals: a summary of quantitative data, a discussion of the existing application, and identifying future research directions. These findings will be useful for subsequent academic studies on transforming e-waste into building materials. The scientometric review provides a path for researchers from various countries to share new ideas and information while encouraging research collaboration.
The rise of electronics inevitably induced the co-pollution of novel brominated flame retardants (NBFRs) and microplastics (MPs). However, studies on how they interact to influence their bioavailability are scarce. Here, we explored the influence mechanism of acrylonitrile butadiene styrene (ABS)-MPs on the bioaccumulation of decabromodiphenyl ethane (DBDPE) in soil-earthworm microcosms. The influence exhibited a temporal pattern characterized by short-term inhibition and long-term promotion. After 28 days of exposure, DBDPE bioaccumulation in a co-exposure (10 mg kg-1 DBDPE accompanied by 1000 mg kg-1 ABS-MPs) was 2.61 times higher than that in a separate exposure. The adsorption process in the soil, intestines, and mucus introduced DBDPE-carried MPs, which had a higher concentration of DBDPE than the surrounding soil and directly affected the bioavailability of DBDPE. MP-pre-exposure (100, 1000, and 10000 mg kg-1) reduced epidermal soundness, mucus secretion, and worm cast production. This eventually promoted the contact between earthworm and soil particles and enhanced the DBDPE of earthworm tissue by 6%-61% in the next DBDPE-postexposure period, confirming that MPs increased DBDPE bioaccumulation indirectly by impairing the earthworm health. This study indicates that MPs promoted DBDPE bioaccumulation via adsorption and self-toxicity, providing new insight into the combined risk of MPs and NBFRs.
The worldwide exponential upsurge of photovoltaic panel installations and the subsequent heights of photovoltaic waste is a matter of intense concern. There is an estimation that within next 2050 year, the worldwide generation of photovoltaic waste may rise upto 60–78 million tons. The objective of this study is to identify the crucial barriers to photovoltaic solar waste management in Canada and prioritize them. At first, the barriers to photovoltaic solar waste management were identified through literature review and expert feedback. Face-to-face interviews were conducted with the selected seven experts who have comprehensive knowledge and expertise on solar management in Saskatchewan. In this study, Analytic Hierarchy Process (AHP) is used to analyze and find prioritization among these barriers. Some crucial barriers from each category are lack of legislative framework, lack of monitoring and supervision, generation of the low volume of solar waste, low profitability in recycling, lack of consumer awareness, and lack of knowledge about business opportunities. Among the rest, lack of restriction on landfill disposal, undefined role of stakeholders, lack of subsidy and tax rebate, additional cost for consumers, lack of knowledge about business opportunities, insufficient campaigns are also worth mentionable barriers. This study is expected to contribute to the concerned government agencies to assess, evaluate, and utilize the priority of barriers to establish a sustainable and resilient solar waste management plan in Saskatchewan, Canada.KeywordsPhotovoltaic panelSolar wasteAnalytic hierarchy processWaste managementBarriers
The near-infrared spectra technique is an effective and non-destructive analysis method for polymer identification, and it has been applied in waste plastics classification. Since the near-infrared spectra are easily affected by instrumental noise, baseline drift and light scattering, spectral data preprocessing is indispensable for classification tasks. In this paper, a classification method is proposed to improve the accuracy of waste smartphone plastics classification. Savitzky–Golay smoothing, moving average smoothing, first-derivative, second-derivative, standard normal variate, and multiplicative scattering correction were used for noise reduction, baseline correction, and scattering correction. These algorithms were combined into five strategies for the spectral data preprocessing, and the optimal spectral data preprocessing strategy was selected based on the accuracy of mixed plastics classification. Successive projections algorithm and competitive adaptive reweighted sampling were used to extract the spectral feature and also the optimal spectral feature extraction algorithm was selected according to the accuracy of mixed plastics classification. The NIR spectra data of four waste smartphone plastics: polyamide, polycarbonate, acrylonitrile butadiene styrene, and polycarbonate/acrylonitrile butadiene styrene blend were analyzed to illustrate the performance of the proposed method. The results show that the accuracy of the proposed method is improved by 11.2% on average compared with the method without optimization.
In this chapter, a method for the separation of mixed polymeric waste from the automotive industry for the efficient recovery of raw materials for mechanical recycling was proposed. The topic of the study was shredded mixed polymeric waste, which was subjected to separation in several stages (for liquids of different specific densities) using the sink-float density method. In this process, the mixed plastics were separated into a heavy fraction and a light fraction, consisting of plastics of lower specific density in comparison with the medium in which the flotation process was carried out. Next, the selected separated material fractions were subjected to heat pressing to prepare standardized test samples intended to evaluate the quality of the polymer blends produced. The mechanical properties were evaluated by a static tensile test in which the tensile modulus, tensile strength, elongation at maximum tensile strength, tensile at the break, and elongation at break were determined. Microscopic evaluation of the fractured surface obtained in the static tensile test was also evaluated. The obtained test results allowed us to evaluate the efficiency of the separation process using the flotation method and allowed us to determine the most advantageous composition of the composite. The study showed that by sink-float separation it is possible to recover pure polymer fractions for industrial applications.
Bromine is an important resource that is widely used in medical, automotive, and electronic industries. Waste electronic products containing brominated flame retardants can cause serious secondary pollution, which is why catalytic cracking, adsorption, fixation, separation, and purification have gained significant attention. However, the bromine resources have not been effectively reutilized. The application of advanced pyrolysis technology could help solve this problem via converting bromine pollution into bromine resources. Coupled debromination and bromide reutilization during pyrolysis is an important field of research in the future. This prospective paper presents new insights in terms of the reorganization of different elements and adjustment of bromine phase transition. Furthermore, we proposed some research directions for efficient and environmentally friendly debromination and reutilization of bromine: 1) precise synergistic pyrolysis should be further explored for efficient debromination, such as using persistent free radicals in biomass, polymer hydrogen supply, and metal catalysis, 2) rematching of Br elements and nonmetal elements (C/H/O) will be a promising direction for synthesizing functionalized adsorption materials, 3) oriented control of the bromide migration path should be further studied to obtain different forms of bromine resources, and 4) advanced pyrolysis equipment should be well developed.
Os resíduos de equipamentos eletroeletrônicos (REEE) estão cada vez mais presentes no cotidiano. Algumas empresas brasileiras realizam apenas o pré-tratamento de REEE: triagem e desmantelamento, desconsiderando o processo de refino, que apresentaria benefícios econômicos. O artigo apresenta, através da revisão de literatura, a situação atual da reciclagem brasileira e destaca alguns metais desperdiçados das PCI e indica o processo hidrometalúrgico para recuperar estes materiais. Palavras-chave: Lixo eletrônico; Gestão de resíduos; Reciclagem de metais. INTRODUÇÃO Os resíduos de equipamento eletroeletrônicos (REEE) estão entre os fluxos de crescimento mais rápido do mundo (Li, 2017). Um relatório lançado pelas Nações Unidas em 2019 mostrou que o ritmo da taxa de crescimento anual de resíduos eletroeletrônicos subiu para 50 milhões de toneladas, com uma tendência crescente ano após ano (Bel et al., 2019). A gestão correta destes resíduos em simbiose com a reciclagem adequada pode gerar resultados significativos no âmbito econômico, uma vez que apresentam substâncias de alto valor em sua composição, como o cobre e metais nobres como a prata, ouro e paládio, sendo esse último encontrado em concentrações dez vezes maiores em PCIs (Placas de circuito impresso) do que no minério comercialmente extraído (Santos, 2012). Há uma preocupação também com os riscos à saúde e ao meio ambiente, quando associados a uma possível disposição incorreta dos REEE. Os mesmos apresentam um elevado potencial poluidor, já que cada aparelho pode conter até 12 elementos considerados altamente prejudiciais a saúde e ao meio ambiente, dentre eles cádmio, chumbo e arsênio (Wu et. al., 2008). A Política Nacional de Resíduos Sólidos (Brasil, 2010), prevê a prevenção e a redução na geração de resíduos. Podem ser realizadas alterações impostas pela política, incluindo a proibição de importação de resíduos perigosos, que podem causar danos ao ambiente ou à saúde humana, incentivos financeiros de âmbito federal a conselhos locais para a elaboração de planos de gestão de resíduos, o fim das chamadas "lixeiras" (locais impróprios onde a população se desfazia dos seus resíduos) e a implementação da logística reversa. A logística reversa (Lei 12.305/2010) pretende dar continuidade ao ciclo de vida de um material, fazendo com que os fabricantes, importadores, distribuidores e comerciantes dos produtos sejam envolvidos em um ciclo responsável. Assim, as empresas que fabricam produtos são responsáveis por encontrar alternativas para o fim da sua vida útil, e são responsáveis por desenvolver estratégias de retorno, tanto de embalagens, quanto dos eletrônicos, além de descartar corretamente os seus resíduos (Brasil, 2010; Nelen et al., 2014). A presença de metais preciosos proporciona um forte incentivo à reciclagem de resíduos de equipamentos eletroeletrônicos (REEE) (Wang e Xu, 2014). Todos REEE contêm placa de circuito impresso (PCI: peça base na qual são montados os circuitos eletrônicos) e, com os avanços tecnológicos, a concentração de metais nestas placas tem se tornado cada vez mais heterogênea, e seus componentes, compactos, dificultando os processos de reciclagem. Tais peças contém a maior quantidade de metais, cerca de 40% do total, sendo a principal parte de interesse para a recuperação (Ladou, 2006; Cucchiella et al., 2015; Gosh et al., 2015; Kumar, Holuszko, Espinosa, 2017). No entanto, infelizmente, no Brasil, mesmo com a recente implementação de políticas nacionais de gestão de resíduos, os governos federais e locais não controlam o número de REEE gerados pela sociedade. A maioria dos aparelhos eletrônicos não chegam no processo de refino e são encaminhados para empresas
There is a big waste generation nowadays due to the growing demand for innovation and the fact that more and more products have a reduced lifetime, increasing the volume of dumps and landfills. Currently, one of the segments of large volume is the technology waste, which reflects on the printed circuit boards (PCBs) that are the basis of the electronics industry. This type of waste disposal is difficult, given that recycling is complex and expensive, because of the diversity of existing materials and components, and their difficult separation process. Regarding the material involved in PCBs, there are metal fractions (MFs) and non-metallic fractions (NMFs), of which the recycling of NMFs is one of the most important and difficult processes, because they amount to about 70% of the weight of the PCB's waste. In the present paper, a literature review of the recycling of non-metallic fractions (NMFs) has been carried out, showing different studies and guidelines regarding this type of recycling, emphasizing that this type of waste still lacks for further application.
Ultrasonic-assisted acid leaching was used to improve extraction of indium from blast furnace sludge. The effects of solid–liquid ratio, leaching temperature, and leaching time on extraction of indium were investigated and three leaching methods of high temperature acid leaching (HL), ultrasonic acid leaching (UL), and high temperature-ultrasonic acid leaching (HUL) were compared. The results show that extraction of indium increases with leaching time for all the methods. UL exhibits the lowest indium extraction. For HL, extraction of indium reaches 32.6 pct when the leaching time is 4 hours, and after 4 hours, the extraction increases slowly. Leaching temperature has a more positive effect on extraction of indium than ultrasonic. HUL can lead to a higher extraction of indium than high temperature acid leaching and UL, and extraction of indium reaches 40.4 pct when the leaching time is 2 hours. After 2 hours, no obvious increase occurs. HUL not only increases extraction of indium but also reduces the leaching time which can improve production efficiency.
Recovery of indium from LCD screen wastes, which contain indium in the form of indium tin oxide (ITO) as the electrode material, is becoming economically and environmentally justified. Indium is a valuable metal and the present work was aimed to recover indium from ITO as the starting material to study the recovery of indium from waste LCD screens by solvent extraction.The apparent rate of dissolution in acidic media is slow requiring six hours for complete dissolution of the ITO sample in 1 M of either H2SO4 or HCl. Complete dissolution in HNO3 took significantly longer. The acid concentration was found to have a major effect on both the amount and rate of leaching allowing some leaching selectivity.Three solvent systems were chosen to study their selectivity for the separation of indium from tin: TBP, D2EHPA and a mixture of both. With either 1 M of TBP or 0.2 M of D2EHPA + 0.8 M of TBP, tin could be selectively extracted from a 1.5 M HCl solution of this metal. D2EHPA extracts both indium and tin from H2SO4 media but indium could be selectively stripped with HCl from the loaded D2EHPA. Based on these results, a scheme for separating and concentrating indium from ITO by solvent extraction is proposed. The scheme includes dissolving ITO into 1 M of H2SO4, then extracting indium and tin to D2EHPA followed by selective stripping of indium into 1.5 M of HCl. With this process, HCl solution containing 12.2 g/L of indium could be achieved.
Background, Aims and Scope
The interest in recycling materials at the end of their life is growing in the industry in general. As regards the Wastes of Electrical and Electronic Equipment (WEEE), an appreciable increase of these materials has been noticed in the last decades, 117 · 103 tons of WEEE have been produced in Italy in 2002 according to Ecohitech [1] and the increase in this kind of waste is three times higher than that of the municipal waste according to the FISE ASSOAMBIENTE report [2]. Within WEEE, End-of-Life Cathode Ray Tube (EOL CRT) glass, the main part of TV sets and PC monitors, is here analysed using both a technical approach to establish a possible reuse of the glass in a open-loop recycling field (ceramic industry) and a methodology (LCA) capable of providing environmental evaluations.
Methods
The technological characterization was performed by chemical resistance tests (UNI EN ISO 10545-13), staining tests (UNI EN ISO 10545-14) with blue methylene and potassium permanganate (KMnO4), and surface abrasion tests (UNI EN ISO 10545-7). The LCA study was conducted using the SimaPro 5.0 software and Eco-Indicator 99 as an evaluation method.
Results and Discussion
The good technical results, reached by using cleaned EOL CRT panel glass inside a ceramic glaze formulation instead of a commercial frit, are supported by the environmental impact evaluation, which shows a decrease of the overall potential damage (measured in Points) of 36% and, in particular, a reduction of 53% in ‘Human health’, 31% in ‘Eco-system quality’ and 24% in ‘Resources’.
Conclusions
This study has demonstrated that this new, open-loop recycling strategy for the CRT glass significantly reduces the environmental impact of the ceramic glaze production process. In fact, in all damage categories examined in this study, there is a minor impact. An improvement is evident in the respiratory inorganics sub-category related to the lowering of dusts mainly and to a lesser amount with NOx and SOx in the climate change sub-category, due mainly to the reduction of CO2 emission correlated to the avoided combustion of the mixture which feeds melting furnaces in the frit production. Thus, the damage decrease in ‘Ecosystem quality’ is prevalently due to the lower NOx emissions by the kilns in the frit production that is evident in the acidification/eutrophication sub-category. Finally, the significant saving in the ‘Resource’ category is principally linked to the fossil fuels sub-category, thanks to the methane saving which stokes the melting furnaces.
Perspectives
Furthermore, the decrease in CO2 emission (94.4%) evident in the climate change sub-category is a very important topic because it is in line with the Kyoto protocol (1997), where significant efforts have been exerted for the reduction of the green house gases emission, notably CO2. The CO2 emission is correlated to the combustion of the mixture which feeds melting kilns in the frit production, therefore the recycling of secondary raw materials, already in a glass state, can reduce the emissions of this gas. This reduction can be termed as environmental credit and it is an example of an allocation of environmental loads in a open-loop recycling, where waste from one industrial system are used as raw materials in another product system.
Separation and concentration of indium from a liquid crystal display (LCD) was conducted using homogeneous liquid-liquid extraction (HoLLE) in order to completely recycle the LCD. First, using 2.40 M hydrochloric acid, 1.52 mg of indium was leached from the LCD of a mobile phone while keeping the amount of leached foreign metals, such as iron and aluminum, as low as possible. The ability to recycle the LCD glass is also expected because arsenic and antimony, which are used as antifoamers for the glass, were separated in the leaching residue. Next, on the basis of the metal leaching results for a mobile phone LCD, HoLLE with Zonyl FSA (CF3(CF2)nCH2CH2SCH2CH2COOH, n = 6-8, Du Pont Co.) was conducted via the formation of metal-1,10-phenanthroline chelates on a solution formulated to simulate the leachate from a mobile phone LCD. Using this technique, more than 96.7% of the indium was extracted from the simulated leaching solution into the sedimented liquid phase. After phase separation, the volume ratio (Va/Vs) of the aqueous phase (Va) and the sedimented liquid phase (Vs) was 438 (46 ml → 0.105 ml). In addition, the sedimented liquid phase was dropped on a filter and evaluated using X-ray fluorescence analysis. After determination of the elements concentrated into the sedimented liquid phase, the mass concentration of indium in the sedimented liquid phase was estimated to be 10.4 wt%. This result indicated that the mass concentration ratio was 405 because the mass concentration of indium in the mobile phone LCD was 0.0257 wt% on the basis of being determined by heating and leaching with aqua regia.
InAs/InAs1‑xSbx type-II superlattices (SLs)
have been grown on GaSb (100) substrates using molecular beam epitaxy
with different Sb/In and As/In flux ratios and growth temperatures
ranging from 400 °C to 450 °C. The change in SL microstructure
as a result of adjusting the growth conditions has been comprehensively
studied. High-resolution x-ray diffraction reveals increase in Sb
composition as either growth temperature or the ratio of As/Sb is
decreased. Cross-sectional electron micrographs show excellent
crystallinity, particularly for those samples grown close to the
strain-balanced condition at lower temperatures and those with higher
Sb/As flux ratios.
By 2013 the demand for thin-film transistor liquid-crystal display (TFT-LCD) panels will be approximately 364 million m2, or approximately 9.8 × 106 ton. According to the Waste Electrical and Electronic Equipment directive, electrical and electronic equipment waste must be reused and recycled to reduce the amount of e-waste deposited in landfills. TFT-LCD waste glass comprises mainly SiO2 and Al2O3 and can be used to produce geopolymers. This study investigates the effects of the solid/liquid and SiO2/Na2O ratios on the properties of metakaolin-based geopolymers. Recycled TFT-LCD waste glass (0–40%) replaces metakaolin, thereby reducing the amount of metakaolin produced. This study tests samples to determine their quality, including setting time and compressive strength. These tests include mercury intrusion porosimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy. Results indicate that TFT-LCD waste glass consists of SiO2 and Al2O3. The geopolymer based on 10% waste glass and 90% metakaolin had a compressive strength of 62 MPa after 60 days of curing. The geopolymerization products filled the pores, producing a denser structure. TFT-LCD waste glass has the potential to partially replace metakaolin as a geopolymer material because of its useful mechanical characteristics.
A laboratory-scale triboelectrostatic separation system in conjunction with analytical techniques was used to study fly ash beneficiation. Fly ash samples were characterized by size analysis and carbon content and then subjected to dry triboelectrostatic separation. Due to differences in the surface physical and chemical properties of the carbon and ash, particles of unburnt carbon and fly ash were triboelectrically charged to opposite polarity and then separated by passing them through a static electric field. Ash fractions deposited on the positive and negative electrodes were collected, analysed for carbon content and subjected to SEM and petrographic analyses. The results indicate that the physical and chemical properties of the ash dictate the maximum carbon-ash separation that would be possible. In addition, the potential of dry separation technology for removing unburnt carbon from coal ash was demonstrated.
In this study, an efficient rough vacuum-chlorinated separation method was developed for the recovery of indium from waste liquid crystal display (LCD) panels using NH4Cl as the chlorinating agent. High purity In2O3 and SnO2 were firstly investigated in a rough vacuum, air and nitrogen atmosphere. The results indicated that the rough vacuum atmosphere could increase the recovery ratio of indium and reduce the influence of tin simultaneously. Moreover, the indium chloride and NH4Cl can be selectively recovered under different condensing temperatures, and the thermodynamic principle of the recovery method was analyzed. Conditions of 400 °C, 10 min, rough vacuum atmosphere (0.09 MPa) and sufficient NH4Cl (molar Cl/In ratio of 6) were confirmed as the optimal conditions by pure substance experiments. The waste LCD glass powder was used to recover indium. The weight ratio of NH4Cl to glass powder and the optimum particle size were confirmed as 1:2 and less than 0.13 mm, respectively. The pure indium chloride was successfully recovered from the waste LCD panels using this method, and the recovery percentage of indium and the purity of indium chloride are 98.02 and 99.50%, respectively. This work presented a promising technology for the cyclic regeneration of the precious metal indium from waste LCD panels.
A large amount of an etching waste containing indium is wasted by plants manufacturing liquid crystal displays. In this study, the recovery of indium from the etching waste by solvent extraction and electrolytic refining was investigated. Initially, major impurities, such as aluminum and molybdenum, were removed by dissolution using sodium hydroxide. From the resulting etching cake, solvent extraction of indium was studied for the extractant of PC88A. Indium was extracted efficiently in an acidity range of 0.1 to 0.5mol/dm3 (MH+). PC88A extracts indium, aluminium, molybdenium, and iron from the HCl medium, but indium could be selectively stripped from the loaded solvent. The conditions for continuous running on a pilot scale using PC88A were obtained. The resulting indium solution was further purified to metal by electrolytic refining so that the final purity of the indium metal was 99.997%.
Pyrolysis appears to be an emerging option allowing recovery of useful products from wastes of electric and electronic equipment (WEEE) because of the high value of potentially accessible products such as precious metals or coke (in the residue), fuel and chemicals (pyrolysis oil and gases). However, contamination of oil by harmful compounds remains a severe issue and has a strong impact on material recycling and thermal treatment: Bromine-containing phenols are classic examples of harmful compounds emitted during pyrolytic recycling of printed circuit boards, and their dehalogenation is an area of continuing scientific interest. Pyrolysis of 2,4-dibromophenol (DBP) with high density polyethylene (HDPE), low density polyethylene (LDPE), polybutadiene (PBD), polystyrene (PS), polyamide 6 (PA-6), polyamide 6,6 (PA-6,6) and polyacrylonitrile (PAN) at 290–370°C for 20min results in the successive transformation of DBP to monobromophenols and further to phenol and HBr, together with small amounts of alkylphenols, depending on the reaction temperature and reactivity of polymers. The formation of PBDDs and PBDFs is strongly retarded despite of the structure of DBP, which favours their development. The rate of hydrodebromination decreased in the series LDPE>HDPE>PBD>PS≈PA-6>PA-6,6>PAN. The hydrodebromination process transforms the polymers studied in the highly polyaromatized char. The formation of the pyrolysis products is in favour of a radical hydrodebromination mechanism.
The effectiveness of supercritical water oxidation (SCWO) process for the simultaneous recovery of chromium and destruction of organics from liquid crystal display (LCD) manufacturing process wastewater was investigated. The experiments were performed in an isothermal continuous-flow tubular reactor and H2O2 was used as an oxidant. The reaction temperatures ranged from 400 to 605°C and the residence times ranged from 15 to 31s at a fixed pressure of 25MPa. The effect of temperature, oxidant concentration and residence time on chromium recovery and chemical oxygen demand (COD) conversion was investigated. The results of this study demonstrated that the SCWO process recovered chromium and decreased chemical oxygen demand up to 99.3% and 99.9%, respectively. The analyses showed that chromium are recovered as chromium oxide (α-HCrO2 and Cr2O3). The SCWO process is an effective technique for simultaneously recovering chromium and for the destruction of hazardous organics in the LCD manufacturing process wastewater. Our study showed that there are two consequent reactions, chromium recovery reaction (hydrolysis) followed by the organic decomposition reaction (oxidation). The recovery of chromium can be achieved without major organic decomposition.
Two of the most commonly used brominated plastics in electrical and electronic goods, Br-ABS and Br-HIPS have been degraded in supercritical water up to 450°C and 31MPa in a batch Hastelloy-C reactor. The plastics were reacted both in the absence and presence of alkaline additives, NaOH and Ca(OH)2. The main reaction products were oils with near-zero bromine and antimony content in the presence of NaOH additive. The compositions of the oils were similar, comprising compounds like toluene, ethylbenzene, propylbenzene, cumene, butyl benzene, acetophenone, naphthalenes, phenylnaphthalenes, diphenylpropane, diphenylcyclopropane and a variety of multi-benzene compounds. Ethylbenzene was the predominant compound in the oils from both plastics. Phenols and substituted phenols were present in the oils from Br-ABS. Sodium hydroxide was more effective than Ca(OH)2 in the removal of organobromine compounds or in suppressing their formation in the oils. Up to 99wt% of the bromine atoms in the plastics was removed into the aqueous phase. Nearly, the entire antimony in the plastics was found in the solid residues obtained after the reactions. The NH3 and HBr released during the degradation of Br-ABS, reacted together forming ammonium bromide while keeping the reaction medium almost neutral. Carbon dioxide was the major component of the gas product from Br-ABS. In addition, both plastics produced hydrogen and hydrocarbon gases of which alkane gases were predominant.
The risk of occurrence of phenomena inducing worsening of fluidisation quality and eventually leading to bed defluidisation is one of the major constraints to an easier utilisation of fluidised beds for the low-temperature pyrolysis of plastic wastes. In order to investigate these phenomena, different mixtures of plastic wastes, obtained by combination of three commercially-available recycled polymers, were fed to a laboratory-scale bubbling fluidised bed reactor. Two mechanisms of defluidisation were identified and the time at which defluidisation occurred was measured and correlated to a key variable of the process. The observed phenomenology was also simulated by means of room-temperature experiments carried out with a selected mineral oil. The results allow us to demonstrate the existence of a synergistic effect between the observed mechanisms of defluidisation.
After the first life cycle of plastics various recycling processes are available for further utilization of these valuable materials. For an ecologically and economically satisfying solution the most suitable process has to be chosen. In chemical recycling polymers are degraded to basic chemical substances which can be reused in the petrochemical industry. For soiled waste plastics or waste plastics which could not be recycled until now, chemical recycling plays a key role. The pyrolysis of acrylic polymers provides a good example for comparing a fluidized-bed reactor and a tubular reactor on the basis of reactor modelling evaluations. The used tubular reactor with internal mass transport is a simplified model for a rotary kiln. Relevant parameters for reactor design and scale-up are presented.
A non-thermal process for reducing indium(III) oxide (In2O3) and/or indium tin oxide (ITO) into indium–metal by milling with lithium nitride (Li3N) under (NH3) or nitrogen (N2) gas environment is proposed in this paper. Milling operation causes mechanochemical reaction in the systems of In2O3/ITO and Li3N, to form In and LiOH. The latter is soluble in water, so that the milled sample was subjected to washing with water, enabling us to recover indium–metal. According to the characterization of the milled products by X-ray diffraction (XRD), the reduction of In2O3/ITO can be achieved in a short period of time. Analytical data by inductively coupled plasma (ICP) from dissolution of the pellets in acidic solution clearly shows that indium–metal concentration is over 95% and the yield of In from the starting oxide sample is more than 97%, depending on the milling condition. The reaction mechanism between In2O3/Li3N and NH3/N2 is also discussed in the paper, and this could be applied to recover indium–metal from electric device wastes containing ITO.
Cathode ray tubes (CRTs) in television and computer monitors are one of the most common components of discarded electronics in the solid waste stream. CRTs present a disposal problem because of their growing magnitude in municipal solid waste (MSW) and their role as a major source of lead in MSW. Using the EPA Toxicity Characteristic Leaching Procedure (TCLP), lead leachability from CRTs was studied. Lead leached from the CRT samples at an average concentration of 18.5 mg/L. This exceeded the regulatory limit of 5.0 mg/L. Several factors affected the lead concentrations of each CRT sample. These included the sample fraction of the CRTs, the particle size used in the tests, and the CRT type. The most significant quantities of lead were obtained from the funnel portion of the CRTs at an average lead concentration of 75.3 mg/L. The major source of lead in the funnel is the frit seal of color CRTs. Samples containing the frit seal had lead leaching levels nearly 50 times those without. Samples comprised of smaller particle sizes exposed a greater surface area resulting in higher lead leaching levels. While 21 of 30 color CRTs exceeded regulatory lead limits, none of the six monochrome CRTs did. Age of the CRTs was not a significant factor for lead leaching. These results provide useful information to the regulatory and waste management community for developing policies for managing discarded CRTs.
Waste electrical and electronic equipment (WEEE) plastics are particularly problematic to recycle because they contain a variety of brominated flame retardants, some of which are extremely toxic. Pyrolysis has been proposed as a viable processing route for toxic WEEE plastics, but it has been found that the volatile pyrolysis products contain toxic brominated compounds. In this work, we have built on previous work where we reported that zeolite catalysts were capable of destroying toxic organobromines during pyrolysis (Hall, W. J.; Williams, P. T. J. Anal. Appl. Pyrolysis 2008, 81, 139−147). We have investigated the pyrolysis of brominated high-impact polystyrene and acrylonitrile−butadiene−styrene in the presence of a waste fluidized catalytic cracker (FCC) catalyst. It is reported that, unlike Y-zeolite, the FCC catalyst did not completely destroy the organobromine compounds; however, the catalyst did lower the yield of bromine found in the liquid pyrolysis products by a mechanism that is as yet unclear. The waste FCC catalyst did not greatly alter the composition of the nonbrominated pyrolysis products, and valuable single-ring aromatics were present in the pyrolysis oil.
Recycling of plastics from screen housing poly mers is considered to be helpful to fulfill the requirements of the European waste of electric and electronic equipment directive. However, brominated flame retardants (BFR) and polybrominated dioxins and furans, which are partly limited in marketable products by European and German legislation, have been identified in waste screen housings and need to be eliminated. On application to housing shredder, sink and float was investigated as sorting technology, since BFR-equipped styrene polymers exhibit higher densities compared to corres ponding non-BFR types. The feasibility of this concept was proven by database studies and density monitoring of waste screen housing. Laboratory and small-technical scale trials with different mixtures of TV-sets and PC monitor housings revealed that only 5–20% of the original bromine load remained in the target fractions, resulting in bromine levels between 0.18–1.39%. Recycled polymers from fractions rich in HIPS-based TV-set casings did not exceed given threshold limits for PBDD/F and octabromodiphenylether. They were recovered with yields of 52–63% and exhibited mostly virgin-like mechanical properties. In contrast, PC monitor housing fractions were characterized by low yield, high bromine levels in recycled products and brittle recycled polymers. Furthermore, pilot application of another separation approach, the specific swell and float technology, allowed the separation of upgraded HIPS qualities from bromine-reduced TV-set fractions. In contrast, this success has not yet been achieved with waste PC monitors. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1262–1273, 2006
The recycling of WEEE (waste electrical and electronic equipment) became a requirement in April 2001 in Japan under the Home Appliance Recycling Law. By 2008 the criterion for the recycling ratio will be raised to 80%–90%, and at that time plastic must also be recycled. For this work, gasification processes (feedstock recycling technology) were selected for plastics WEEE recycling. After high temperature treatment, at over 1200°C, shock cooling of the gases to a temperature of roughly under 200°C was done by this process. The generated ‘thin’ gas could then be used as raw materials for chemical industries or for electric power generation. The effect of the high temperature treatment and the shock cooling suppresses the emission of brominated dioxins to a very low level, just as for chlorinated dioxins. Copyright © 2003 John Wiley & Sons, Ltd.
a b s t r a c t The Taiwan production of TFT-LCD front-panels comprises a global share of 39.2%, the highest production rate in the world. Inevitably, a large amount of waste is produced in the fabrication process. The objective of this research is to recycle waste LCD glasses in the production of controlled low strength material (CLSM), which has been used extensively for pipeline refill and pavement foundations world-wide. The glass replaces sand in ratios of 0%, 10%, 20% and 30% in order to produce CLSM specimens with high sil-icon contents. The specimens are then tested for their compressive strength, supersonic strength, electri-cal resistivity, and permeability ratio. Results show a slump range up to 200 mm and a slump flow range up to 410 mm. For the general type CLSM, the setting time for the 10% glass–sand replacement is the shortest while that for the 30% replace-ment is the longest. After a 28-day aging, the compressive strength is 2.87–2.40 MPa. The ultrasonic pulse velocity is between 1267–3200 m/s and is found to be faster for the early strong type. The electrical resis-tivity after 28 days for the general type is 6.7–8.2 kX-cm and doubles for the early strong type. The per-meability ratio is 1.03–2.02% for the normal and 0.35–0.75% for the early strong type. It was observed that adding waste LCD glass into CLSM meets engineering property requirements including high fluidity, low strength, high permeability, and low electrical resistivity, ushering in a creative application of waste glass.
It is estimated that approximately 6,000,000 scrap TVs and 10,000,000 personal computers are generated each year in China. Cathode ray tubes (CRTs) from these machines consist of 85% glass (65% panel, 30% funnel and 5% neck glass). The leaded glass (funnel-24%, neck-30%) may seriously pollute the environment if it is not properly disposed of. In this paper, the past, current and future status of CRT dismantling technologies as well as the CRT glass recycling situation in China are presented and discussed. Recycling technology for waste CRTs in China is still immature. While the conventional CRT dismantling technologies have disadvantages from both economic and environmental viewpoints, some of the new and emerging treatments such as automatic optical sorting facilities that have been applied in developed countries offer advantages, and therefore should be transferred to China in the next few years to solve the CRT pre-processing problem. Meanwhile, because the demand for CRT glass closed-loop recycling is extremely limited, the authorities should take effective measures to improve CRT glass recycling rates and to facilitate a match to local conditions. Moreover, we also provide a broad review of the research developments in recycling techniques for CRT cullet. The challenge for the future is to transfer these environmentally friendly and energy-saving technologies into practice.
Over the past 30 years, China has been suffering from negative environmental impacts from distempered waste electrical and electronic equipments (WEEE) recycling activities. For the purpose of environmental protection and resource reusing, China made a great effort to improve WEEE recycling. This article reviews progresses of three major fields in the development of China's WEEE recycling industry: legal system, formal recycling system, and advanced integrated process. Related laws concerning electronic waste (e-waste) management and renewable resource recycling are analyzed from aspects of improvements and loopholes. The outcomes and challenges for existing formal recycling systems are also discussed. The advantage and deficiency related to advanced integrated recycling processes for typical e-wastes are evaluated respectively. Finally, in order to achieve high disposal rates of WEEE, high-quantify separation of different materials in WEEE and high added value final products produced by separated materials from WEEE, an idea of integrated WEEE recycling system is proposed to point future development of WEEE recycling industry.
In this present study, Hg in waste in the EU has been estimated at around 990 metric tonnes (t) (including coal combustion products, landfills, chlor-alkali waste and incinerator slag) for the year 1995, and it is suggested that if complete information was available for the 15 member states, the amount would be 2–4 times larger. During the 1990s there were 45 Hg cell chlorine facilities in the EU and the amount of Hg in chlorine (Cl2) was calculated at 95.2 t based on 14–17 g Hg t−1 of Cl2 capacity. The waste from coal-fired power plants in the EU member states contained about 16.5 t of Hg, which was transferred to products for road construction, and other industrial uses or stored in landfills. This Hg can then be exchanged between the atmospheric, aquatic and terrestrial compartments. Hg is occasionally recovered from waste, but this is often discouraged for economic reasons. Recovery units are found, for example, in Germany, France, Austria, and Sweden. The total amount of secondary Hg recovered from waste is not known. Metallic Hg and Hg-bearing waste are exported and imported from the EU member states, except for export from Sweden, which is banned by national legislation.
Electronic waste, or e-waste, is an emerging problem as well as a business opportunity of increasing significance, given the volumes of e-waste being generated and the content of both toxic and valuable materials in them. The fraction including iron, copper, aluminium, gold and other metals in e-waste is over 60%, while pollutants comprise 2.70%. Given the high toxicity of these pollutants especially when burned or recycled in uncontrolled environments, the Basel Convention has identified e-waste as hazardous, and developed a framework for controls on transboundary movement of such waste. The Basel Ban, an amendment to the Basel Convention that has not yet come into force, would go one step further by prohibiting the export of e-waste from developed to industrializing countries.
The waste electrical and electronic equipment (WEEE) directives are designed to deal with the rapidly increasing waste stream comprised of electrical and electronic equipment. Recycling electrical and electronic equipment reduces the quantity of waste going to final disposal. The demand for thin film transistor liquid crystal display (TFT-LCD) panels, commonly used in everyday electronic products, is increasing. Conventionally adopted treatments of TFT-LCD waste glass cannot meet WEEE directives. This study adopts the following operating conditions in fabricating glass–ceramics: sintering temperature of 800–950 °C; sintering time of 6 h; and, temperature increase rate of 5 °C/min. The glass–ceramic samples then underwent a series of tests, including the Vickers hardness, water absorption and porosity tests, to determine product quality. The Vickers hardness was 12.1 GPa when fired at 900 °C for 6 h, and density was 2.4 g/cm3 and water absorption was 0%. Thus, TFT-LCD waste glass can be regarded as a good glass–ceramic material.
E-waste comprises discarded electronic appliances, of which computers and mobile telephones are disproportionately abundant because of their short lifespan. The current global production of E-waste is estimated to be 20–25 million tonnes per year, with most E-waste being produced in Europe, the United States and Australasia. China, Eastern Europe and Latin America will become major E-waste producers in the next ten years. Miniaturisation and the development of more efficient cloud computing networks, where computing services are delivered over the internet from remote locations, may offset the increase in E-waste production from global economic growth and the development of pervasive new technologies. E-waste contains valuable metals (Cu, platinum group) as well as potential environmental contaminants, especially Pb, Sb, Hg, Cd, Ni, polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs). Burning E-waste may generate dioxins, furans, polycyclic aromatic hydrocarbons (PAHs), polyhalogenated aromatic hydrocarbons (PHAHs), and hydrogen chloride. The chemical composition of E-waste changes with the development of new technologies and pressure from environmental organisations on electronics companies to find alternatives to environmentally damaging materials. Most E-waste is disposed in landfills. Effective reprocessing technology, which recovers the valuable materials with minimal environmental impact, is expensive. Consequently, although illegal under the Basel Convention, rich countries export an unknown quantity of E-waste to poor countries, where recycling techniques include burning and dissolution in strong acids with few measures to protect human health and the environment. Such reprocessing initially results in extreme localised contamination followed by migration of the contaminants into receiving waters and food chains. E-waste workers suffer negative health effects through skin contact and inhalation, while the wider community are exposed to the contaminants through smoke, dust, drinking water and food. There is evidence that E-waste associated contaminants may be present in some agricultural or manufactured products for export.
The co-pyrolysis of brominated high impact polystyrene (Br-HIPS) with polyolefins using a fixed bed reactor has been investigated, in particular, the effect that different types of brominated aryl compounds and antimony trioxide have on the pyrolysis products. The pyrolysis products were analysed using FT-IR, GC–FID, GC–MS, and GC–ECD. Liquid chromatography was used to separate the oils/waxes so that a more detailed analysis of the aliphatic, aromatic, and polar fractions could be carried out. It was found that interaction occurs between Br-HIPS and polyolefins during co-pyrolysis and that the presence of antimony trioxide influences the pyrolysis mass balance. Analysis of the Br-HIPS + polyolefin co-pyrolysis products showed that the presence of polyolefins led to an increase in the concentration of alkyl and vinyl mono-substituted benzene rings in the pyrolysis oil/wax resulting from Br-HIPS pyrolysis. The presence of Br-HIPS also had an impact on the oil/wax products of polyolefin pyrolysis, particularly on the polyethylene oil/wax composition which converted from being a mixture of 1-alkenes and n-alkanes to mostly n-alkanes. Antimony trioxide had very little impact on the polyolefin wax/oil composition but it did suppress the formation of styrene and alpha-methyl styrene and increase the formation of ethylbenzene and cumene during the pyrolysis of the Br-HIPS.
The management of electrical and electronic equipment waste (WEEE) is a significant problem of industrialized countries, in the last decades it has been noticed an appreciable increase of this residue, consisting of about 80% of television sets and computers containing end of life (EOL) cathode ray tubes (CRT). Specific technologies permit to dismantle the kinescope, obtaining different glasses with high quality level and specific chemical compositions. The presence of dangerous elements makes critical the re-use in many fields of application. The present work proposes the feasibility of CRT glass recycling in ceramic field using it into a base glaze formulation as substitute of “ceramic frits”. The study was conducted in two phases, laboratory scale in order to study the suitable glaze formulation and semi-industrial scale with the technological support of an Italian ceramic glaze producer. The glazes obtained have aesthetic and mechanical properties extremely similar to the standard ones.
Plastic materials have been associated with electric and electronic applications since the early days of the electrical industry. Plastics can amount up to 30% of the scrap mass. Generally, they contains flame retardants such as halogenated compounds which can lead to the formation of different toxic products. Recycling, incineration and landfilling are the current methods used to treat these plastics. They also can be used as combustibles in some metallurgical processes. However, during their combustion, halogenated flame retardants can produce dibenzop-dioxins and dibenzo-furans.
The disposal of scrap cathode ray tube (CRT) funnel glass has become a global environmental problem due to the rapid shrinkage of new CRT monitor demand, which greatly reduces the reuse for remanufacturing. To detoxificate CRT funnel glass by lead recovery with traditional metallurgical methods, mechanical activation by ball milling was introduced to pretreat the funnel glass. As a result, substantial physicochemical changes have been observed after mechanical activation including chemical breakage and defects formation in glass inner structure. These changes contribute to the easy dissolution of the activated sample in solution. High yield of 92.5% of lead from activated CRT funnel glass by diluted nitric acid leaching and successful formation of lead sulfide by sulfur sulfidization in water have also been achieved. All the results indicate that the application of mechanical activation on recovering lead from CRT funnel glass is efficient and promising, which is also probably appropriate to detoxificate any other kind of leaded glass.
Metal-plated plastics (MPP), which are important from the standpoint of aesthetics or even performance, are increasingly employed in a wide variety of situations in the automotive industry. Serious environmental problems will be caused if they are not treated appropriately. Therefore, recycling of MPP is an important subject not only for resource recycling but also for environmental protection. This work represents a novel attempt to deal with the MPP. A self-designed hammer crusher was used to liberate coatings from the plastic substrate. The size distribution of particles was analyzed and described by the Rosin-Rammler function model. The optimum retaining time of materials in the crusher is 3 min. By this time, the liberation rate of the materials can reach 87.3%. When the density of the suspension is 31,250 g/m(3), the performance of liberation is the best. Two-step magnetic separation was adopted to avoid excessive crushing and to guarantee the quality of products. Concerning both the separation efficiency and grade of products, the optimum rotational speed of the magnetic separator is 50-70 rpm. On the basis of the above studies about the liberating and separating behavior of the materials, a continuous recycling system (the technology of crush-magnetic separation) is developed. This recycling system provides a feasible method for recycling MPP efficiently, economically, and environmentally.
The degradation process of brominated flame retardant (BFR) and BFR-containing waste computer housing plastic in various supercritical fluids (water, methanol, isopropanol and acetone) was investigated. The results showed that the debromination and degradation efficiencies, final products were greatly affected by the solvent type. Among the four tested solvents, isopropanol was the most suitable solvent for the recovery of oil from BFR-containing plastic for its (1) excellent debromination effectiveness (debromination efficiency 95.7%), (2) high oil production (60.0%) and (3) mild temperature and pressure requirements. However, in this case, the removed bromine mostly existed in the oil. Introduction of KOH into the sc-isopropanol could capture almost all the inorganic bromine from the oil thus bromine-free oil could be obtained. Furthermore, KOH could enhance the depolymerization of the plastic. The obtained oil mainly consisted of single- and duplicate-ringed aromatic compounds in a carbon range of C9-C17, which had alkyl substituents or aliphatic bridges, such as butyl-benzene, (3-methylbutyl)-benzene, 1,1'-(1,3-propanediyl)bis benzene. Phenol, alkyl phenols and esters were the major oxygen-containing compounds in the oil. This study provides an efficient approach for debromination and simultaneous recovering valuable chemicals from BFR-containing plastic in e-waste.
This paper describes a direct analysis study carried out in a recycling unit for waste electrical and electronic equipment (WEEE) in Portugal to characterize the plastic constituents of WEEE. Approximately 3400 items, including cooling appliances, small WEEE, printers, copying equipment, central processing units, cathode ray tube (CRT) monitors and CRT televisions were characterized, with the analysis finding around 6000 kg of plastics with several polymer types. The most common polymers are polystyrene, acrylonitrile-butadiene-styrene, polycarbonate blends, high-impact polystyrene and polypropylene. Additives to darken color are common contaminants in these plastics when used in CRT televisions and small WEEE. These additives can make plastic identification difficult, along with missing polymer identification and flame retardant identification marks. These drawbacks contribute to the inefficiency of manual dismantling of WEEE, which is the typical recycling process in Portugal. The information found here can be used to set a baseline for the plastics recycling industry and provide information for ecodesign in electrical and electronic equipment production.
Waste electrical and electronic equipment (WEEE) contains up to 25% plastics. Extraction of higher quality fractions for recycling leaves a mix of plastic types contaminated with other materials, requiring the least environmentally harmful disposal route. Data from trials of pyrolysis, described in part 1 of this paper set, were used in a life cycle assessment of the treatment of WEEE plastics. Various levels of recycling of the sorted fraction were considered, and pyrolysis was compared with incineration (with energy recovery) and landfill for disposal of the remainder. Increased recycling gave reduced environmental impact in almost all categories considered, although inefficient recycling decreased that benefit. Significant differences between pyrolysis, incineration and landfill were seen in climate change impacts, carbon sent to landfill, resources saved, and radiation. There was no overall "best" option. Landfill had the least short-term impact on climate change so could be a temporary means of sequestering carbon. Incineration left almost no carbon to landfill, but produced the most greenhouse gases. Pyrolysis or incineration saved most resources, with the balance depending on the source of electricity replaced by incineration. Pyrolysis emerged as a strong compromise candidate since the gases and oils produced could be used as fuels and so provided significant resource saving without high impact on climate change or landfill space.
Growth in waste electrical and electronic equipment (WEEE) is posing increasing problems of waste management, partly resulting from its plastic content. WEEE plastics include a range of polymers, some of which can be sorted and extracted for recycling. However a nonrecyclable fraction remains containing a mixture of polymers contaminated with other materials, and pyrolysis is a potential means of recovering the energy content of this. In preparation for a life cycle assessment of this option, described in part 2 of this paper set, data were collected from trials using experimental pyrolysis equipment representative of a continuous commercial process operated at 800 °C. The feedstock contained acrylonitrile-butadiene-styrene and high impact polystyrene with high levels of additives, and dense polymers including polyvinylchloride, polycarbonate, polyphenylene oxide, and polymethyl methacrylate. On average 39% was converted to gases, 36% to oils, and 25% remained as residue. About 35% of the gas was methane and 42% carbon monoxide, plus other hydrocarbons, oxygen and carbon dioxide. The oils were almost all aromatic, forming a similar mixture to fuel oil. The residue was mainly carbon with inorganic compounds from the plastic additives and most of the chlorine from the feedstock. The results showed that the process produced around 70% of the original plastic weight as potential fuel.
Waste cathode ray-tube (CRT) funnel glass is classified as hazardous waste since it contains high amount of lead. In the present study, a novel process for lead nanopowder synthesis from this type of glass was developed by combining vacuum carbon-thermal reduction and inert-gas consolidation procedures. The key trait of the process was to evaporate lead out of the glass to obtain harmless glass powder and synchronously produce lead nanoparticles. In the synthesis process, lead oxide in the funnel glass was firstly reduced to elemental lead, and evaporated rapidly in vacuum circumstance, then quenched and formed nano-size particles on the surface of the cooling device. Experimental results showed that temperature, pressure and argon gas flow rate were the major parameters controlling lead evaporation ratio and the morphology of lead nanoparticles. The maximum lead evaporation ratio was 96.8% and particles of 4-34 nm were successfully obtained by controlling the temperature, holding time, process pressure, argon gas flow rate at 1000°C, 2-4h, 500-2000 Pa, 50-200 ml/min, respectively. Toxicity characteristic leaching procedure (TCLP) results showed that lead leaching from the residue glass met the USEPA threshold. Accordingly, this study developed a practical and environmental-friendly process for detoxification and reclamation of waste lead-containing glass.
In order to recover valuable materials and to minimize the adverse effects of hazardous materials contained in scrap computers, a dismantling practice is commonly adopted to treat scrap computers. By using the dismantling process, both useful and hazardous materials can be manually separated and retrieved. On the basis of the properties of the retrieved materials, they can be sent to appropriate facilities for further recycling or treatment. Among the retrieved materials, the treatment of hazardous materials from cathode ray tubes (CRT) and printed circuit boards with integrated circuits have drawn considerable attention, thus implying that the proper treatment of such materials can greatly assure the successful recycling of scrap computers. For this reason, this study reviews the available technologies which can be applied to treat and recycle cathode ray tube components and printed circuit boards with integrated circuits. Actual recycling data from a scrap computer recycling plant located in Taiwan are also introduced. The data show that this recycling plant can recover 94.75 wt. % and 45.99 wt. % of useful materials from the main machines (i.e., CPU, power supplier, fan, IC boards, DVD drive, CD drive, hard disk, soft disk, shell casing, etc.) and monitors of scrap computers, respectively.
Rapid advances in the electronic industry led to an excessive amount of early disposal of older electronic devices such as computer monitors and old televisions (TV) before the end of their useful life. The management of cathode ray tubes (CRT), which have been a key component in computer monitors and TV sets, has become a major environmental problem worldwide. Therefore, there is a pressing need to develop sustainable alternative methods to manage hazardous CRT glass waste. This study assesses the feasibility of utilizing CRT glass as a substitute for natural aggregates in cement mortar. The CRT glass investigated was an acid-washed funnel glass of dismantled CRT from computer monitors and old TV sets. The mechanical properties of mortar mixes containing 0%, 25%, 50%, 75% and 100% of CRT glass were investigated. The potential of the alkali-silica reaction (ASR) and leachability of lead were also evaluated. The results confirmed that the properties of the mortar mixes prepared with CRT glass was similar to that of the control mortar using sand as fine aggregate, and displayed innocuous behaviour in the ASR expansion test. Incorporating CRT glass in cement mortar successfully prevented the leaching of lead. We conclude that it is feasible to utilize CRT glass in cement mortar production.
This paper presents and critically analyses the current waste electrical and electronic equipment (WEEE) management practices in various countries and regions. Global trends in (i) the quantities and composition of WEEE; and (ii) the various strategies and practices adopted by selected countries to handle, regulate and prevent WEEE are comprehensively examined. The findings indicate that for (i), the quantities of WEEE generated are high and/or on the increase. IT and telecommunications equipment seem to be the dominant WEEE being generated, at least in terms of numbers, in Africa, in the poorer regions of Asia and in Latin/South America. However, the paper contends that the reported figures on quantities of WEEE generated may be grossly underestimated. For (ii), with the notable exception of Europe, many countries seem to be lacking or are slow in initiating, drafting and adopting WEEE regulations. Handling of WEEE in developing countries is typified by high rate of repair and reuse within a largely informal recycling sector. In both developed and developing nations, the landfilling of WEEE is still a concern. It has been established that stockpiling of unwanted electrical and electronic products is common in both the USA and less developed economies. The paper also identifies and discusses four common priority areas for WEEE across the globe, namely: (i) resource depletion; (ii) ethical concerns; (iii) health and environmental issues; and (iv) WEEE takeback strategies. Further, the paper discusses the future perspectives on WEEE generation, treatment, prevention and regulation. Four key conclusions are drawn from this review: global amounts of WEEE will continue unabated for some time due to emergence of new technologies and affordable electronics; informal recycling in developing nations has the potential of making a valuable contribution if their operations can be changed with strict safety standards as a priority; the pace of initiating and enacting WEEE specific legislation is very slow across the globe and in some cases non-existent; and globally, there is need for more accurate and current data on amounts and types of WEEE generated.
In view of the environmental problem involved in the management of WEEE, and then in the recycling of post-consumer plastic of WEEE there is a pressing need for rapid measurement technologies for simple identification of the various commercial plastic materials and of the several contaminants, to improve the recycling of such wastes. This research is focused on the characterization and recycling of two types of plastics, namely plastic from personal computer (grey plastic) and plastic from television (black plastic). Various analytical techniques were used to monitor the compositions of WEEE. Initially, the chemical structure of each plastic material was identified by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). Polymeric contaminants of these plastics, in particular brominated flame retardants (BFRs) were detected in grey plastics only using different techniques. These techniques are useful for a rapid, correct and economics identification of a large volumes of WEEE plastics.
A novel process for crystalline silicotitanate (CST) synthesis was developed using waste cathode ray tube (CRT) panel glass as silicon source. The key trait of the process was to extract most of the silicon out of the glass for CST preparation, but leave Ba and Sr in the residue which had the potential to be employed as raw material for metallic Ba and Sr metallurgy. In the synthesis process, waste CRT panel glass was firstly treated by supercritical water (SCW)-NaOH solution for Si extraction, then sol-gel and hydrothermal treatments were used for CST preparation. 80% of Si in the glass could be extracted into the solution, while Sr and Ba were enriched in the residue in the form of Sr(2)SiO(4) and Ba(2)Si(3)O(8), respectively. Sr and Ba contents in the residue were 2-3 times higher than those in the raw glass. SEM, XRD and TEM results indicated that CST was successfully synthesized. Ion exchanging experiments showed that the batch distribution coefficient of the synthesized CST to Cs(+) was up to 1.2x10(4) mL/g at pH 0.26.