Recycling Of Electronic Scrap Research Articles

Microbial Processing of Waste Shredded PCBs for Copper Extraction Cum Separation—Comparing the Efficacy of Bacterial and Fungal Leaching Kinetics and Yields

The recycling of electronic scrap is an important subject not only from an environmental aspect but also for recovering metal resources such as copper. In this work, the microbial extraction of copper and other metals (Cu, Ni, Co, Fe and Al) present in the depopulated and shredded printed circuit board (PCB) is elaborated. Bacterial strains of A. ferrooxidans, A. thiooxidans and a fungal strain, A. niger are used for copper extraction along with other metals from shredded PCBs. An optimum metal recovery of 93% Cu was obtained at 308 K, pH 2 using 8% pulp density in 10 days by a mixed culture of A. ferrooxidans and A. thiooxidans. Whereas using A. niger, a metal recovery of 66% Cu was reported using similar experimental conditions. The results show the higher potential ability of bacteria as compared to fungus to bioleach copper. Additionally, the kinetics and mechanism of copper bioleaching from this e-waste by the chemolithotrophs and heterotrophs were evaluated. The leach liquor obtained from the optimized leaching process was subjected to separation and purification of copper as >99% pure copper sulfate using Acorga M5640 by solvent extraction.

Environmental impact of high-value gold scrap recycling

PurposeThe gold routes satisfying the global gold supply are mining (74%), recycling of high-value gold (23%), and electronic scraps (3%). Besides its applications in the investment, jewelry, and industrial sector, gold also has a bad image. The gold production in industrial as well as artisanal and small-scale mines creates negative impacts such as resource depletion, extensive chemical use, toxic emissions, high energy consumption, and social concerns that are of great importance. On the other hand, almost all gold is recycled and has historically always been. In common life cycle assessment (LCA) databases, there is no data on recycling of high-value gold available. This article attempts to answer the question what the ecological benefits of this recycling are.MethodIn this study, we were able to collect process data on the most commonly used high-value gold scrap recycling process, the aqua regia method, from several state-of-the-art German refineries. With this data, life cycle inventories were created and a life cycle model was produced to finally generate life cycle impacts of high-value gold scrap recycling.ResultsThis study contains the corresponding inventories and thus enables other interested parties to use these processes for their own LCA studies. The results show that high-value gold scrap recycling has a considerably lower environmental impact than electronic gold scrap recycling and mining. For example, high-value gold scrap recycling in Germany results in a cumulative energy demand (CED) of 820 MJ and a global warming potential (GWP) of 53 kg-CO2-Eq. per kg gold. In comparison, common datasets indicate CED and GWP levels of nearly 8 GJ and 1 t-CO2-Eq. per kg gold, respectively, for electronic scrap recycling and levels of 240 GJ and 16 t-CO2-Eq. per kg gold, respectively, for mining.ConclusionThe results show that buying gold from precious metal recycling facilities with high technological standards and a reliable origin of the recycling material is about 300 times better than primary production.

Identification of peptides as alternative recycling tools via phage surface display – How biology supports Geosciences

The application of biological tools in Geosciences such as bacteria or microbial products that mobilize metallic components raises increasing interest in classical mining industries. Today, 10% of the total copper production in Chile originated from bioleaching operations (Gentina and Acevedo, 2016). However, the application of biological tools is limited due to poor specificity, complex material composition and heterogenous particle size. New studies focus on smaller biological components such as peptides with higher material specificity to mobilize and recycle materials of interest.End-of-life electronic products like smart phones or compact fluorescent lamps (CFL) contain a wide variety of precious elements in very low concentrations. Currently, no cost-efficient and environmentally friendly technology exists for the separation and recycling of the majority of high-tech industry supporting elements such as the rare earth element (REE) Lanthanum phosphate (LAP) from electronic scrap. The focus of this project was the identification of peptides with high specificity for the rare earth mineral LAP, a component of CFL, for future material recycling. By using a biological method called phage surface display and the random PVIII phage peptide library f88.4/Cys6, the phage-bound peptide TSTQCPSHIRACLKKR was identified and characterized as not only an efficient LAP binder, which is furthermore able to discriminate between LAP and other components of fluorescent lamps. The application of phage particles displaying the recombinant PVIII fused peptide TSTQCPSHIRACLKKR in recycling processes is not possible due to limited scale-up, critical public perception, low biological efficiency and fast mutation rates in phage particles. Future applications will be based on peptides that are stable under a variety of challenging conditions such as heat, varying pH or in the presence of toxic scrap components. The development of peptide-based separation tools represents a new way of recycling of electronic scrap.

Comparison of different routes for recovery of metals from electronic scrap

There is an exponential demand for electronic equipment but, unlike other consumer products, the useful lifetime is relatively short which calls for the recycling of electronic scrap. Considering the inflow of illegally imported discards from the West, the electronic waste is expected to reach a total of around 30 million tonnes by 2020. Waste printed circuit boards (WPCB) are valuable secondary raw material for critical and precious metal industries. In this work, WPCB of different sizes were dissolved in different lixiviants for metal dissolution. The leach solution contains different metals due to a differential solubility of metals and associated attachments. With organic solvent DMF, plastic, baseboard, and metallic values are easily detached and separated without any contamination of plastic and metal. The coarse ground PCB material subjected to dense medium separation resulted in the clear separation of plastics and metals. Further, the metal fraction is magnetically separated to recover iron-steel values. With all the three processes almost 90% of metal values are recovered from PCB’s. Based on three processes examined, it can be concluded that organic solvent processing and physical beneficiation process are better than hydrometallurgical route as the latter includes extra concentration and separation step.

A Pilot Assessment of Occupational Health Hazards in the US Electronic Scrap Recycling Industry

The National Institute for Occupational Safety and Health (NIOSH) surveyed a randomly selected sample of electronic scrap (e-scrap) recycling facilities nationwide to characterize work processes, exposures, and controls. Despite multiple attempts to contact 278 facilities, only 47 responded (17% response rate). Surveyed facilities reported recycling a wide variety of electronics. The most common recycling processes were manual dismantling and sorting. Other processes included shredding, crushing, and automated separation. Many facilities reported that they had health and safety programs in place. However, some facilities reported the use of compressed air for cleaning, a practice that can lead to increased employee dust exposures, and some facilities allowed food and drinks in the production areas, a practice that can lead to ingestion of contaminants. Although our results may not be generalizable to all US e-scrap recycling facilities, they are informative regarding health and safety programs in the industry. We concluded that e-scrap recycling has the potential for a wide variety of occupational exposures particularly because of the frequent use of manual processes. On-site evaluations of e-scrap recyclers are needed to determine if reported work processes, practices, and controls are effective and meet current standards and guidelines. Educating the e-scrap recycling industry about health and safety best practices, specifically related to safe handling of metal dust, would help protect employees.

Management and recycling of electronic waste

Waste electrical and electronic equipment (WEEE) is one of the largest growing waste streams globally. Hence, for a sustainable environment and the economic recovery of valuable material for reuse, the efficient recycling of electronic scrap has been rendered indispensable, and must still be regarded as a major challenge for today’s society. In contrast to the well-established recycling of metallic scrap, it is much more complicated to recycle electronics products which have reached the end of their life as they contain many different types of material types integrated into each other. As illustrated primarily for the recycling of mobile phones, the efficient recycling of WEEE is not only a challenge for the recycling industry; it is also often a question of as-yet insufficient collection infrastructures and poor collection efficiencies, and a considerable lack of the consumer’s awareness for the potential of recycling electronics for the benefit of the environment, as well as for savings in energy and raw materials.

Phase equilibria in the “SnO”–SiO2–“FeO” system in equilibrium with tin–iron alloy and the potential application for electronic scrap recycling

Abstract Experimental studies have been conducted to determine the primary phases and liquidus temperatures in the pseudo-binary system “SnO”–“FeO” and the pseudo-ternary system “SnO”–SiO2–“FeO” in equilibrium with tin–iron alloy between 1148 and 1673 K, using a high-temperature equilibration and quenching technique followed by electron probe X-ray microanalysis of the phase compositions in the quenched samples. The following primary phase fields were identified: wustite (FeO x ), spinel (Fe( 3 – x )Sn x O4), fayalite (Fe2SiO4), tridymite (SiO2), tin iron silicate (Fe4Si2Sn7O16), and cassiterite (SnO2). With this new information on the chemistry of the “SnO”–SiO2–“FeO” slag this system may potentially be used for the processing and recycling of electronic scrap and the recovery of valuable minor elements.

Collection and recycling of electronic scrap: A worldwide overview and comparison with the Brazilian situation

Recycling and the related issue of sustainable development are increasing in importance around the world. In Brazil, the new National Policy on Solid Wastes has prompted discussion on the future of electronic waste (e-waste). Over the last 10years, different e-waste collection systems and recycling processes have been applied globally. This paper presents the systems used in different countries and compares the world situation to the current Brazilian reality. To establish a recycling process, it is necessary to organize efficient collection management. The main difficulty associated with the implementation of e-waste recycling processes in Brazil is the collection system, as its efficiency depends not only on the education and cooperation of the people but also on cooperation among industrial waste generators, distributors and the government. Over half a million waste pickers have been reported in Brazil and they are responsible for the success of metal scrap collection in the country. The country also has close to 2400 companies and cooperatives involved in recycling and scrap trading. On the other hand, the collection and recycling of e-waste is still incipient because e-wastes are not seen as valuable in the informal sector. The Brazilian challenge is therefore to organize a system of e-waste management including the informal sector without neglecting environmentally sound management principles.

Planning models for the dismantling of electrical and electronic equipment under consideration of uncertainties

In this paper, an approach is presented for short-term dismantling planning, including process-induced uncertainty modelled with fuzzy techniques. Weak data resulting from uncertain dismantling time parameters are modelled as fuzzy sets and integrated into a scheduling model that allows the derivation of optimal dismantling procedures. A case study from electronic scrap recycling shows the application of the approach.

Classification of metals and plastics from printed circuit boards (PCB) using air classifier

With the mandatory requirement of recycling and reuse of electronic scraps arising from printed circuit boards (PCB), the non-polluting separation methods to separate metals and plastics are of growing importance nowadays. Mechanical recycling of electronic scrap oriented towards the overall materials recovery from obsolete electronics is being implemented worldwide. Air classification is one among the clean mechanical separation methods that can achieve reasonably good separation of metals and plastics from the PCB stuff. In the present investigation, the separation of metals and plastics from the milled PCB using a column air classifier has been studied in detail. A detailed study on the separation of species in the air classification system was analysed by using the efficiency curve approach and the classifier model parameters such as the reduced efficiency curve parameter ( α), corrected cut size ( V a/ V t) 50c and the size selectivity increment (Δ S) with respect to the process variables. The reduced efficiency relationship for the plastics and metals for all the experimental data were analysed using one parameter ( α). The accuracy of the developed model was checked with the predicted values with all the observed values. The results showed that the simulation model is able to predict the experimental results satisfactorily.

Intelligent Liberation and classification of electronic scrap

Mechanical recycling of electronic scrap oriented towards overall materials recovery from obsolete electronics is being implemented worldwide. The main reason is that the amount of electronic scrap is increasing and that the content of the precious metals present is decreasing. In this context, an effective liberation of various materials like metals and plastics is a crucial step towards mechanical separation. In addition, classification of electronic scrap is also important to be able to provide an appropriate feed material for the subsequent separation process. In the present study, liberation and its impact on the separation of personal computer (PC) scrap and printed circuit board (PCB) scrap has been investigated in detail. A special equipment functioning as a shape separator and an aspirator was used for the classification of electronic scrap.

Pyrolysis and combustion of polymer wastes in combination with metallurgical processes and the cement industry

Various industrial metallurgical processes in which polymer wastes occur, either as undesired impurities or which are added purposely as fuel or as reduction agents are summarized. At the moment, a major route for the use of polymer wastes is in the blast furnace for steel-making. Here, the plastics are substituted for some of the coke, coal, or oil that is used for reduction of the ore and for heating. Other processes in iron-making where the use of polymer wastes has been proposed are based on several varieties of the electric-arc furnace technology. In non-ferrous metallurgy, polymer wastes disturb the secondary melting and, if non-ferrous metals are contaminated with polymer wastes, special precautions must be taken. The recycling of electronic scrap is particularly problematic. Polymer wastes also find use in cement industries, but exclusively as a fuel.

The recovery of metals from electronic scrap

Most of the published literature on the recycling of scrapped electronic devices is listed in chronological order in Table I. In the 1970s and early to mid-1980s, the predominant method of recycling was blast furnace smelting in conjunction with secondary copper or lead smelters. Since the mid-1980s, the trend has shifted toward the hydrometallurgical processing of scrap. The emphasis has always been on the recovery of precious metals, namely gold, silver, platinum and palladium, from electronic scrap for their obvious economic values. In recent years, greater importance has been placed on the recovery of all metals, including low-concentration metals such as cadmium, because of increasingly strict environmental controls. The electronic scrap recycling program of the 1990s will ha ve to meet many objectives—efficient recovery of all metals, strict effluent and emission controls, the use of nontoxic reagents, maximum recycling of chemical reagents, and minimum energy requirements—in an economical and environmentally safe manner.