Recycling mobile phone impact on life cycle assessment

Electronic waste (e-waste) is one of the fastest growing waste streams in the world due to the rapid pace of technology enhancement and development. The exponential growth of e-waste contributes to a rapid increase in the rate of contaminants and waste entering landfills. This paper assesses the waste produced from the recycling of mobile phones in different countries highlighting the material flows and the amount of waste released to the environment. A comparison of mobile phone Printed Circuit Boards (PCBs) recycling through the formal recycling facilities in Malaysia and Australia were used as case studies. The results presented highlight the toxicity of waste and the impact to the environment. A life cycle assessment (LCA) approach was carried out focusing on the end-of-life (EOL) phase of mobile phone PCBs. The IMPACT 2002+ version 2.10 was used as the assessment tool to indicate the environmental impacts quantitatively. The results show the toxicity of the waste produced from the mobile phone PCBs recycling in Malaysia and Australia. This study identifies that the demand for recycled materials, law enforcement, and the e-waste recycling system are significant drivers to reduce the environmental impact of mobile phone recycling

Optimization of process parameters for the selective leaching of copper, nickel and isolation of gold from obsolete mobile phone PCBs

The sequential separation of base and precious metals from the end-of-life mobile phone printed circuit boards (PCBs) is a significant challenge for the development of recycling process that exhibit material circularity. In this contribution, a simple, eco-friendly, and efficient leaching process is developed for the dissolution of copper and nickel from obsolete mobile phone PCBs to facilitate the isolation of a gold-rich residue. Chemical pre-treatment of downsized PCBs produced a metallic portion for which the leaching parameters for copper and nickel were optimised, including the type of leaching reagent, temperature, time, pulp density and agitation speed. It was found that quantitative dissolution of base metals occurred using 3.0 M nitric acid at 30 °C with a 50 g/L pulp density, 2 h residence time, and 500 rpm stirring speed; under these conditions, no gold was dissolved. Design of Experiment analysis using Response Surface Methodology was also undertaken to validate the process. Finally, the kinetics of the leaching process were studied and shown to conform to the chemically controlled surface reaction model, with activation energies of 39.7 and 18.4 kJ/mol for copper and nickel. Importantly, the leaching process optimised in this work avoids the need for high temperatures and reduces energy consumption and effluent generation, leading to the cleaner processing of obsolete mobile phone PCBs for the separation of gold from the dominant base metals

Gold recovery from printed circuit boards of mobile phones scraps using a leaching solution alternative to cyanide

Currently, the printed circuit boards (PCB) of waste electrical and electronic equipment (WEEE) are attracting interest among researchers for environmental concern reasons and mainly for their content of precious metals such as gold. Thus, this study aims to characterize different types of PCBs from mobile phones in relation to the amount of gold contained, to evaluate alternative leaching agents for the gold (ammonium and sodium thiosulfate) and compare these to commercial stripping (cyanide-based) and then the recovery of gold by the electrometallurgical route. First, the amount of gold was determined. Then, alternative leaching agents were tested under different concentrations and time. A cyanide-based solution was also tested to compare the results. The results showed that the content of gold varied from 142 to 700 g/ton. The cyanide-based solution was able to extract 88% of the gold, while sodium and ammonium thiosulfate extracted 70 and 75% of the gold, respectively. The electrowinning tests showed a 94% recovery of the gold present in thiosulfate solutions

Thermodynamic Rarity Assessment of Mobile Phone PCBs: A Physical Criticality Indicator in Times of Shortage

Rising prices in energy, raw materials, and shortages of critical raw materials (CRMs) for renewable energies or electric vehicles are jeopardizing the transition to a low-carbon economy. Therefore, managing scarce resources must be a priority for governments. To that end, appropriate indicators that can identify the criticality of raw materials and products is key. Thermodynamic rarity (TR) is an exergy-based indicator that measures the scarcity of elements in the earth''s crust and the energy intensity to extract and refine them. This paper uses TR to study 70 Mobile Phone (MP) Printed Circuit Boards (PCBs) samples. Results show that an average MP PCB has a TR of 88 MJ per unit, indicating their intensive use of valuable materials. Every year the embedded TR in-creases by 36, 250 GWh worldwide-similar to the electricity consumed by Denmark in 2019-due to annual production of MP. Pd, Ta and Au embedded in MP PCBs worldwide between 2007 and 2021 contribute to 90% of the overall TR, which account for 75, 600 and 250 tones, respectively, and in-creasing by 11% annually. This, coupled with the short lifespan of MP, makes PCBs an important potential source of secondary resources. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Metal Extraction and Recovery from Mobile Phone PCBs by a Combination of Bioleaching and Precipitation Processes

Bearing in mind the metal rich composition of printed circuit boards (PCBs), this material represents a secondary source of valuable metals and offers an entrepreneurial opportunity in the metal sales market. Based on the ability of microorganisms to regenerate and produce the chemical oxidants that are responsible for metal leaching, bioleaching has become an efficient and affordable alternative to conventional metal recycling technologies, although further research is still necessary before industrial implementation. This study focuses on the recovery of metals contained in mobile phone PCBs through a combined process. Two different PCB pre-treatments were evaluated: grinding the whole piece and removing the epoxy cover from the piece without grinding. The benefit of A. ferrooxidans activity on the metal solubilization rate was analyzed. Additional chemical leaching assays were also conducted for comparison purposes and the reagents ferric iron (Fe3+) and sulfuric acid (H2SO4) were selected for these experiments. The copper extraction results obtained in Fe3+ experiments with and without bacteria (A. ferrooxidans) were similar after 260 h of operation, indicating the need for alternative strategies to ensure a controlled and continuous metal biodissolution rate. The contribution of H2SO4 to the leaching processes for copper and nickel was almost negligible during the first 50 h, and more significant thereafter. The recovered metals were precipitated from a synthetic solution simulating a real ferric leaching by adding sodium hydroxide (NaOH) and sodium sulfide (Na2S). The combination of both precipitants allowed an effective removal of metals from the leachate.The authors wish to acknowledge the financial support received from the State Agency for Research (AEI) of the Spanish Government and the European Regional Development Fund (ERDF, EU) [Project CTM2016-77212-P]. The University of the Basque Country UPV/EHU (Spain) [GIU18/118] is also acknowledged

Nickel ammonium thiosulphate leaching of gold from waste mobile phone printed circuit boards

Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2019Over the years, the quantity of e-waste, primarily waste mobile phone printed circuit boards (PCBs), has increased worldwide, as a result of technological advancements in the fields of electronics, telecommunications and computing. Therefore, to sustain the protection of the environment and human health, sustainable measures should be implemented. Electronic waste (e-waste) is known for its wider variety of base and precious metal content compared to naturally occurring ores. Waste mobile phone PCBs are the most attractive type of e-waste due to their higher and more structured precious metal content. Ammonium thiosulphate leaching is considered as one of the promising alternatives to cyanidation in hydrometallurgy. However, its industrial application is limited due to the high reagent consumption which has a direct impact on its cost-effectiveness. This research aimed to investigate the ammonium thiosulphate leaching of gold from waste mobile phone PCBs, with an emphasis on the thiosulphate consumption and interference of the extractable copper in the leaching process. The objectives were to study the effect of acid pre-treatment and copper replacement with nickel as the metal oxidant on gold extraction and thiosulphate consumption. The experiments in this study were all conducted in a batch setup. The PCBs were reduced to less than 3 mm particle size by cutting and crushing. In the acid pre-treatment, sulphuric acid and hydrogen peroxide concentrations were varied between two levels, namely 2 M and 3 M, to identify the optimum conditions that maximised copper extraction and minimised gold extraction. In the ammonium thiosulphate leaching, PCB pre-treatment and metal oxidant were investigated as categorical factors to establish the optimum conditions that maximised gold extraction and minimised thiosulphate consumption. The PCB pre-treatment was varied between two levels: acid-pretreated PCBs and untreated PCBs. The metal oxidant factor was varied between copper and nickel. The other leaching conditions were fixed, as prescribed in the existing literature. The mobile phone PCBs used in this study were found to contain 524 g Au/ton-PCB and 461.8 kg Cu/ton-PCB, as determined by aqua regia leaching. Copper thus contributed to more than 40% of the total PCB mass. In the acid pre-treatment, the optimum reagent combination was 2 M H2SO4 and 3 M H2O2 and resulted in 93.72% copper extraction and 8.83% gold loss in 150 minutes at a pulp density of 50 g/L, 25°C and stirring speed of 350 rpm. Furthermore, it was determined, through material balance, that the PCB mass reduction induced by the acid pre-treatment was mostly attributed to the copper extraction, evidence that the other base metals such as iron and aluminium that could have dissolved in the acid pre-treatment stage were in small quantities in the PCBs to impact the overall mass reduction significantly. The acid pre-treatment was a PCB beneficiation process with an increase in the extractable gold content from 524 to 842 g/ton-PCB and a decrease in the copper content from 461.8 to 51.1 kg/ton-PCB. The variation in H2SO4 concentration had more statistical impact on gold extraction, whereas varying H2O2 concentration had a more statistical influence on copper extraction. The analysis of the goodness of fit of the shrinking-core model to the experimental results indicated that the acid pre-treatment was chemically controlled, with moderate control due to the turbulence. In ammonium thiosulphate leaching, the optimum conditions consisted in using nickel as the oxidant in the thiosulphate leaching of acid-pretreated PCBs at a pulp density of 50g/L, 0.1 M thiosulphate, 0.2 M NH3, 0.03 M Ni2+, pH 10.5, 25°C and stirring speed of 350 rpm. The gold extraction and thiosulphate consumption were found to be 65.41% and 61.03 kg/ton-PCB in 5 hours of leaching time, a significant improvement from the conventional copper-thiosulphate leaching of untreated PCBs which resulted in gold extraction and thiosulphate consumption of 18.61% and 90.9 kg/ton-PCB, respectively. The statistical analysis of experimental results indicated that the variation of the metal oxidant had a higher significance level than the PCB pre-treatment with respect to gold extraction. The assessment of the goodness of fit of the shrinking-core model to the experimental data indicated that the copper-thiosulphate and nickel-thiosulphate leaching processes were both chemically controlled. To assess the degree of comparison between the copper-thiosulphate and nickel-thiosulphate leaching processes for gold extraction from waste PCBs, a preliminary economics assessment was performed, with emphasis on production costs. Considering a basis of 1 metric ton of processed PCB, replacing copper with nickel as the metal oxidant reduced the raw materials costs from 3,768 USD to 2,868 USD, approaching previously reported cyanidation costs closely. The revenue and gross margin were increased from 8,969 and 5,201 USD in copper-thiosulphate leaching to 16,287 and 13,419 USD in nickel-thiosulphate leaching, respectively. Therefore, the use of ammonium thiosulphate as an environment-friendly alternative lixiviant shows potential by virtue of the improved process economics

Environmentally sound system for E-waste: Biotechnological perspectives

The rapid e-waste volume is generating globally. At the same time, different recycling technologies, mainly the mechanical and chemical methods well studied, while the biological method is the most promising approach. Therefore, this article provides a comprehensive information about extracting valuable metals from e-waste. In addition, this article outlines the process and key opportunity for extraction of metals, identifies some of the most critical challenges for e-waste environmentally sound management practices, and opinions on possible solutions for exiting challenges, and emphasis on importance of advanced recycling technologies that can be utilized, in order to minimize the environmental impact causes due to improper recycling of e-waste

A Novel Process for Extracting Precious Metals from Spent Mobile Phone PCBs and Automobile Catalysts

A novel process to simultaneously extract the precious metals such as gold, silver, platinum, palladium and rhodium from spent mobile phone printed circuit boards (PCBs) and honeycomb-type auto catalysts by smelting using waste-copper slag without adding any collector metals or by-products such as dross, matte and slime has been developed. In the process, waste-copper slag which is an industrial waste discharged from copper smelter is used not only as a flux for controlling slag composition, but also as a collector metal for capturing precious metals, and a plastic component contained in spent mobile phone PCBs is done as a reducing agent of iron oxides contained in the waste-copper slag. Using the developed process, up to 95% of gold, silver, platinum, palladium and rhodium contained in the raw materials were extracted in a CuFeSn alloy phase, respectively

Evaluation of elements distribution in printed circuit boards from mobile phones by micro x-ray fluorescence

A micro X-ray fluorescence-based approach for the chemical characterization of spent printed circuit boards (PCBSPCBSS) from mobile phones was applied. More in detail, twelve spent mobile phones were grouped into three clusters according to brands, models and year of release, and a study to evaluate the technological evolution of PCBSs over time was carried out. Precious metals and hazardous elements were investigated, revealing a few differences between samples from the different groups. For instance, the distribution of gold on PCBS layers was more widespread for the older analyzed samples, and smaller quantities of bromine and lead were detected in the more recent models in accordance with the Restriction of Hazardous Substances Directive 2002/95/EC. Analysis of PCBS composition should contribute towards correctly managing such a complex waste, maximizing the recovery of base, critical and precious metals and considering the possible presence of harmful elements requiring careful management. The experimental results showed how, using the proposed approach, distribution maps for chemical elements present in PCBSs could be obtained, thus allowing the definition of optimal strategies for further handling (i.e. classification) and processing (i.e. critical/precious metal recovery)