Discarded Mobile Phones Research Articles

Evaluation of Metals in Printed Wiring Boards of Selected Discarded Mobile Phones in Nigeria

Obsolete mobile phones form a major component of the e-waste stream. The Printed wiring boards (PWBs) of mobile phones are packed with economic and toxic metals. Regulatory bodies such as Restriction of Hazardous Substances (RoHS) directives regulate the amount of these toxic metals in electrical and electronic equipment. This study is aimed at evaluating selected critical metals present in PWBs of three popular brands of discarded mobile phones used in Nigeria to understudy the behaviour of original equipment manufacturers (OEMs) regarding toxicity, economic potentials, and level of compliance with international initiatives by regulatory bodies to reduce the level of toxic metals in electronic equipment. PWBs obtained from 60 discarded mobile phones of 3 popular mobile phone brands used in Nigeria were chopped into smaller particles, extracted according to EPA 3050B method, and analysed using the Inductive Coupled Plasma-Optical Emission Spectrometry technique. It was observed that Mn, Fe, Zn, and Cu, had the highest concentration range across all brands studied. Notable toxic metals such as Pb, Cd, Cr, and As have mean and standard deviation values of 0.43±0.38 mg/kg, 0.62±0.160 mg/kg, 5.16±1.06 mg/kg, and 84.97±13.83 mg/kg respectively. Economic metals: Cu, Ag, and Au had mean and standard deviation values of 80.37±16.89 mg/kg, 2.12±0.43 mg/kg, and 0.95±0.19 mg/kg respectively. Results from the study indicate that PWBs of mobile phones are a perfect secondary source of a large variety of metals vital for the recycling industry. Also, the low levels of toxic metals suggest that some OEMs are already adopting the 'design-for-environment' option. Therefore, PWBs studied seem eco-friendly; however, need to be handled with care as there are still some toxic metals of concern not determined in this study.

Study of gold leaching from pre-treated waste printed circuit boards by thiosulfate‑cobalt-glycine system and separation by solvent extraction

The recovery of gold (Au) from waste printed circuit boards (WPCBs) derived from discarded mobile phones is crucial for the resource preservation and environmental protection. In this context, thiosulfate has emerged as a viable alternative to the toxic compound cyanide for Au leaching. However, the conventional thiosulfate leaching system has a main problem that is large thiosulfate consumption, which limits its commercial application. In this study, we developed a novel thiosulfate leaching system that utilizes a cobalt (Co(II))-glycine (gly) complex as the catalyst. Our findings demonstrate that the Co(II)-glycine-thiosulfate system exhibits excellent Au leaching performance coupled with low thiosulfate consumption. The effects of several parameters on Au leaching efficiencies and thiosulfate consumption were investigated. Increasing the concentrations of Co(II), thiosulfate, or glycine was beneficial to the Au leaching. However, increasing temperature promoted the oxidative decomposition of thiosulfate and reduced cobalt stability, negatively impacting Au leaching. Additionally, small amounts of base metals remained after pretreatment of WPCBs using HCl system and H2SO4-H2O2 system. Therefore, the roasting-assisted leaching process eliminated the adverse effects of these impurity metals and further improved Au leaching efficiency to 97.8% while also decreased thiosulfate consumption. The recovery of Au from the pregnant leach solution was also studied, and our findings demonstrated that N1923 can efficiently extract Au from the solution through anion exchange. Our study developed a novel and efficient Au thiosulfate leaching system catalyzed by the Co(gly)3/Co(S2O3)34− redox couple, and put forward a promising approach to enhance Au recyclability from WPCBs while significantly reducing thiosulfate consumption.

Highly-efficient process for recovering gold from discarded mobile phones using pretreatment and mild extraction

Existing methods for recovering gold from electronic waste are based on mechanical and hydrometallurgy approaches. However, these methods usually use toxic chemicals and demonstrate low gold extraction efficiency (Ge) due to the negative influence of organic materials and other industrial metals also present in the waste. In this work, a more efficient and more environmentally friendly process is proposed that can achieve a high Ge from electronic waste by pre-treatment and pre-extraction before gold extraction. The powdered waste was first pre-treated by a supercritical water oxidation (SWO) process to remove organic materials and then pre-extracted using a mixture of FeCl3 and HCl to remove industrial metals. The solid powder thus produced was then re-extracted by a DMF-CuCl2-NaCl mild extraction system to complete the recovery of the gold content. Experimental results indicated that pre-treatment temperature, pre-treatment time, and the concentration of the FeCl3 and HCl solutions all significantly influenced the amount of gold extracted. The optimal parameters for achieving the highest Ge extraction (99.6%) using the DMF-CuCl2-NaCl extraction system were determined as follows: an extraction temperature of 65 °C, an extraction time of 70 min, a stirring speed of 420 rpm, a sample size of ≤ 850 µm, a solid/liquid (S/L) ratio of 1:12 g·mL−1, a CuCl2 concentration of 0.8 mol·L−1, and a NaCl concentration of 1.6 mol·L−1. After gold extraction, water was then used to precipitate the gold in the form of nanoparticles. Under optimal conditions (70%v/v water, 80 min), over 98.4% of the gold could be recovered in this way.

Enhancement of Leaching Copper from Printed Circuit Boards of Discarded Mobile Phones Using Ultrasound–Ozone Integrated Approach

The recovery of metals from discarded mobile phones has been of interest due to its environmental and economic benefits. This work presents a simple and effective approach for leaching copper (Cu) from the printed circuit boards of discarded mobile phones by combining ultrasound and ozone approaches. The X-ray diffraction (XRD) technique and Fourier-transform infrared spectroscopy (FT-IR) were used to characterize the solid phases, and inductively coupled plasma optical emission spectrometry (ICP-OES) was utilized to determine the concentration of metals in the liquid phases. The effects of several influential parameters, including ultrasound, ozone dose, HCl concentration, liquid/solid ratio, temperature, and reaction time on the leaching efficiency were investigated. The results showed that the optimal conditions for Cu leaching included an ozone dose of 700 mg/h, HCl concentration of 3.0 M, liquid/solid ratio of 8, and temperature of 333 K. Under optimal conditions, about 99% of Cu was leached after 180 min. The shrinking core model was used to analyze the kinetics of the Cu leaching process, and the results showed that the surface chemical reaction governs this process. The activation energy of the leaching reaction, calculated using Two-Point form of the Arrhenius equation, was 10.852 kJ mol−1.

Investigating innovation diffusion, social influence, and personal inner forces to understand people's participation in online e-waste recycling

By integrating the elaboration likelihood model (ELM), innovation diffusion theory (IDT) and social cognition theory (SCT), this study constructs a research model through which to explore the key factors and their influence mechanisms to understand people's participation in online e-waste recycling. Based on the ELM, we believe that people's behavioral intention to participate in online e-waste recycling is affected by the information processing of central and peripheral routes. Based on IDT, we take the perceived innovation characteristics as the key elements of the central route and consider social influence as the key element of the peripheral route. At the same time, we consider personal inner force factors, based on SCT, as the functional condition of the information processing mode to explore the moderating effects of privacy concern, pricing fairness concern, and environmental concern on the information processing of the central and peripheral routes. By taking discarded mobile phones as an example, we collect 475 valid samples to test our research model using the structural equation modelling (SEM) approach. The results confirm that perceived innovation characteristics and social influence are two factors that motivate people to participate in online e-waste recycling and that the three kinds of inner forces have different moderating effects on perceived innovation characteristics and social influence. Based on the above findings, this study puts forward some policy proposals.

Estimating the Generation of Discarded Mobile Phones and Highlighting Areas for Recycling Precious Metals from Printed Circuit Boards in Thailand

Over the last decade, Thailand imported approximately 21 million units of new mobile phones every year, equivalent to 262 million. While technology changes, consumers want the newest model to serve their lifestyle. These discarded mobile phones will be a challenging issue for waste management systems because of the metals in mobile phones, especially in printed circuit boards (PCBs). Sufficient and sustainable management is needed to maximize the benefits of recycling metals and minimize potential risks to public health. This study aims to estimate the possible range of DMP generation in Thailand (2012–2021) with the Approximation 2, Simple Delay, and Time Step methods using the government published data and a literature review. The results show that the discarded mobile phones ranged from approximately 1700 to 2500 tons/year, equivalent to 0.027 to 0.038 kg/year/capita over the last ten years. In 2021, more than half of the total mobile phone waste generated in the northeastern and central areas of Thailand was around 468.73 and 325.14 tons/year, respectively. Additionally, 1.28 tons of precious metals (Ag, Au), 5.33 tons of rare earth elements, and 7.26 tons of toxic metals (As, Cd, Cr, Pb) can be found in the PCB waste of DMPs.

Fungal bioleaching of e-waste utilizing molasses as the carbon source in a bubble column bioreactor

Mobile phones are known as the most widely used electronic instruments, and an enormous number of discarded mobile phones are generated. The present work used a pure culture of Penicillium simplicissimum in a bubble column bioreactor to extract Cu and Ni from mobile phone printed circuit boards (MPPCBs) waste. Molasses was used as an efficient carbon source to enhance bioleaching efficiency and increase the cost benefits. The adaptation phase was done at Erlenmeyer flasks to reach 40 g/L of MPPCBs powder. The most significant parameters, including the mass of MPPCBs powder, aeration, molasses concentration, and their interaction, were optimized in order to leach the maximum possible Cu and Ni using central composite design in response surface methodology (RSM). The model p-values for Cu and Ni recovery were 0.0030 and 0.0348, respectively, emphasizing the model's accuracy. 96.94% of Cu was recovered under 8.8% (v/v) of molasses, aeration rate of 0.29 (l/min), and MPPCBs powder of 10 g/L. The optimized condition of Ni leaching was 1.9% (v/v) of molasses, aeration rate of 0.37 (l/min), and MPPCBs powder of 10 g/L, resulting in 71.51% recovery. The present article demonstrated the great potential of P. simplicissimum to improve metal recovery from e-waste utilizing molasses and bubble column bioreactors.

Characterization of end-of-life mobile phone printed circuit boards for its elemental composition and beneficiation analysis

ABSTRACT Globally, waste electrical and electronic equipment is one of the fastest-growing waste sectors. Mobile phones constitute the major portion of the telecommunication e-waste category. Over the years, waste mobile phones were considered as a potential source of secondary metals. This study aims to determine the physical and chemical composition of the discarded mobile phones and to evaluate its recovery potential. The printed circuit boards from the discarded (waste) mobile phones (MPCB) were collected and samples of different sizes 3 × 3 cm, 2 mm, 1 mm, 500 µm, and 150 µm were obtained after milling and sieving. Elemental composition revealed the presence of base metals, Cu, Zn, Fe, Ni, and Pb, in higher quantities with a significant amount of precious metals Au and Ag. Amount of base metals present in different MPCB size fractions was found in the order 3 × 3 cm > 2 mm > 1 mm > 500 µm >150 µm. The amount of precious metals like Ag and Au was found to be higher in large-sized MPCB fractions. FTIR studies declared the presence of polymers like ABS, PC, and HIPs in MPCB samples. TCLP tests for toxic metals revealed that MPCBs contained high concentrations of cadmium, lead, and mercury highlighting their hazardous potential. The ultimate analysis revealed that NMF has a GCV of 12.34 MJ/kg and a volatile content of 42.25%, which can be a potential source of energy that can be recovered through the gasification or pyrolysis process. Overall, the comprehensive characterization of waste MPCBs will systematically provide a better understanding of e-waste recycling processes for beneficiation purpose and sustainable resource utilization. Implications: A comprehensive characterization of waste mobile phone printed circuit boards for its elemental composition was performed. Mechanical treatment steps before MPCBs processing increased the exposure of metals resulting in a higher concentration of metals in acid-digested samples. The elemental analysis of MPCBs revealed that MPCBs possessed significant quantities of base and precious metals. The amount of precious metals like Ag and Au was also found in higher ranges in large-sized MPCB fractions, which elucidated fact to be considered in the pre-treatment process for metal recoveries. The high content of base and precious metals in waste mobile phones displayed their economic potential in the market. This new source may compensate for the escalating global demand for gold and silver. Results from the study indicated that MPCBs can serve as an excellent secondary source for various metals and as an efficient alternative fuel.

A cross-linked polymer inclusion membrane for enhanced gold recovery from electronic waste

A cross-linked polymer inclusion membrane (CL-PIM) incorporating the extractant trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate (Cyphos® IL 104) was developed for the first time for the enhanced Au(III) recovery from aqua regia digests of electronic waste (discarded mobile phones). Cellulose triacetate (CTA), poly(vinyl chloride) (PVC) and poly(vinylidene fluoride-co-hexafluropropylene) (PVDF-HFP) were examined as base polymers. The suitability of poly(ethylene glycol) dimethylacrylate (PEGDMA), poly(ethylene glycol) divinyl ether (PEGDVE) and N-ethylmaleimide (NEM) as cross-linking agents, and the possibility of using triarylsulfonium hexafluorophosphate (TASHFP) and 2,2-dimethoxy-2-phenylacetophenone (DMPA) as initiators were investigated. It was demonstrated that the CL-PIMs composed of Cyphos® IL 104 (30 wt%), PVDF-HFP, PEGDMA (base polymer to cross-linking agent ratio 6:4) and DMPA (1 wt%) or TASHFP (2 wt%) transported Au(III) from 2.5 mol L−1 hydrochloric acid solutions twice as fast as their non-CL-PIM counterpart, showing excellent stability over five successive transport experiments. However, in aqua regia feed solutions (6 mol L−1 acidity) only the CL-PIM containing TASHFP was able to achieve complete Au(III) recovery. AFM studies revealed that the PVDF-HFP-based CL-PIMs had a much higher surface contact area when compared to their non-CL counterpart, and this is proposed to be the reason for their superior transport performance. The CL-PIM that showed good transport efficiency in aqua regia was also applied to aqua regia digests of electronic waste from two mobile phones, and Au(III) was selectively recovered in less than 24 h, while other metals present in significantly higher concentrations were not transported.

A Review of Harmful Aspects of Mobile on Health and Environment

Background: Cell phone based on communication and digital technology has become inseparable elementin life of users and has proved to be a panacea of all information and communication needs over the years.But as a necessary evil it may cause harm to both health and environment. Objectives: It is envisaged to beaware of the potential health hazards, dos and don’ts towards healthy use of cell phone. The aims to create abackground to find level of awareness for health aspects related to mobile phones and disposition behaviourfor discarded mobile phones based on previous studies.Methods: The study highlights the harmful aspects of mobile on health and environment from the literaturereview perspective.Results: Review of previous studies show that there is very less awareness for harmful effects of mobilephones on health and environment. Disposition of EoL mobile phones in proper manner is very limited.Conclusion: Studies indicate the risks associated with cell phone due to its electromagnetic fields (EMF)while in use and health hazards at the end-of-life or not in use or discarded mobile phones. Therefore healthydisposal methods of mobile phones in the context of sustainable electrical and electronic equipment wastemanagement have also emerged as a significant issue.

Sustainability Potentials of Informal Gold Recovery from Discarded Mobile Phones: E-waste Management Insights for Global Business and Trade

Sustainability Potentials of Informal Gold Recovery from Discarded Mobile Phones: E-waste Management Insights for Global Business and Trade

An integrated method of environmental analysis and system dynamics for management of mobile phone waste in Colombia

Global concern about electronic waste is growing due to the awareness of the consequences of inadequate management of this waste. The relationship between the accelerated development of telecommunications, globalization, economic growth, market conditions, environmental policies, the generation of electronic waste and the negative impact on the environment are of increasing interest for specialists in environmental science. This study aims to identify the relevant variables that influence electronic waste generation from discarded mobile phones, and the environmental implications of use and disposal of mobile telephones via a case study in Colombia, using a System Dynamics Model and the analysis of several various scenarios. The main determining factors were identified as mobile telephony line acquisitions, gross domestic product per capita, and the lifespan of mobile phones. These were shown to be the determining variables in the generation of waste of electrical and electronic equipment (WEEE) in the case of mobile phones in Colombia. Secondly, the amount of carbon dioxide emissions depends on the length of usage of the phones; in 2019 the actual waste generated by the disposal of mobile phones only contributed to 10.07 CO2 tons, compared to 102,245 tons generated by their usage.

Toxicity trends in E-Waste: A comparative analysis of metals in discarded mobile phones

Mobile phones and various electronic products contribute to the world’s fastest-growing category of hazardous waste with international repercussions. We investigated the trends in potential human health impacts and ecotoxicity of waste mobile phones through quantitative life cycle impact assessment (LCIA) methods and regulatory total threshold limit concentrations. A market-dominant sample of waste basic phones and smartphones manufactured between 2001 and 2015, were analyzed for toxicity trends based on 19 chemicals. The results of the LCIA (using USEtox model) show an increase in the relative mass of toxic materials over the 15-year period. We found no significant changes in the use of toxic components in basic phones, whereas smartphones contained a statistically significant increase in the content of toxic materials from 2006 to 2015. Nickel contributed the largest risk for carcinogens in mobile phones, but the contributions of lead and beryllium were also notable. Silver, zinc and copper contents were associated with non-cancer health risks. Copper components at 45,818–77,938 PAF m3/kg dominated ecotoxicity risks in mobile phones. Overall, these results highlight the increasing importance of monitoring trends in materials use for electronic product manufacturing and electronic-waste management processes that should prevent human and environmental exposures to toxic components.

Assessment of sampling and chemical analysis of waste printed circuit boards from WEEE: gold content determination

Waste printed circuit boards (WPCBs) from discarded mobile phones and smartphones are considerably heterogeneous materials with a high gold content (approx. 490 grams per ton). The aim of our chemical analysis of samples of WPCBs was to determine the amounts of gold using open acid digestion and atomic absorption spectrometry (HR CS AAS). The test samples designated for chemical analysis must genuinely represent the bulk WPCBs from which they are taken. This study aimed to develop a correct sampling procedure to analyze the heterogeneous materials from printed circuit boards; explicitly concerning the influence of particle size on the precision of chemical analysis of WPCBs from discarded mobile phones. Chemical analysis of the representative sample of WPCBs with a grain size fraction of d ≤ 200 μm determined that the gold content was 475 g∙t-1 with a low variation coefficient and low dispersion which indicates very high accuracy of the designed sampling procedure.

Recovery of Precious Metals from Discarded Mobile Phones by Thiourea Leaching

The objective of this work was to recover gold and silver from the printed circuit board (PCB) of discarded mobile phones by thiourea leaching. Effects of thiourea concentration, leaching temperature, leaching time, and ferric ion (Fe3+) concentration on the recovery of gold and silver were investigated. The PCB was pretreated physically to reduce the thiourea consumption and enhance the leaching process. It was found that the percentage of gold leaching was higher than that of silver at different conditions studied. The highest percentages of gold (96%) and silver (90%) leachings were achieved with 20 g/L of thiourea and 8 vol% of Fe3+ at 4 h of leaching time and 25°C of leaching temperature.

Recovery of gold ions from discarded mobile phone leachate by solvent extraction and polymer inclusion membrane (PIM) based separation using an amic acid extractant

This paper reports on the selective separation and recovery of gold ions from leachates of discarded mobile phones using liquid-liquid extraction and a polymer inclusion membrane (PIM) transport system. The collected mobile phones were crushed by a mill and the obtained powder was calcinated. After leaching with aqua regia, the metal composition of the leachate was analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). The analysis results confirmed that the mobile phone waste contained 397 g/ton of gold. Liquid-liquid extraction and PIM-based separation procedures for the selective recovery of gold(III) from synthetic and actual leachates were developed. The extracting organic solution and the PIM incorporated the newly synthesized extractant N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]glycine (D2EHAG) which exhibited high selectivity for the gold(III) ion over the other metal ions present in much higher concentrations in the leachates. The compositions of the feed and receiving solutions in both the liquid-liquid and PIM based extraction and back-extraction of the gold(III) ions were optimized. It was established that optimal extraction required a HCl concentration in the feed solution of 2 mol/L and that a receiving solution containing 0.1 M thiourea in 1 M HCl was capable of back-extracting gold(III) quantitatively. Membrane transport experiments with a synthetic leachate as the feed solution demonstrated that 96% of the gold(III) ions was selectively transported into the receiving solution of the transport cell thus leaving all other metal ions in the leachate.

Recovery of indium from liquid crystal displays of discarded mobile phones using solvent extraction

One of the greatest challenges in the development of hydrometallurgical processes for the recovery of indium from secondary sources is the fact that the leaching step generally results in very dilute solutions. Therefore, this diluted indium solution must be concentrated before being sent to a subsequent step such as recovery of the metal by electrowinning. The aim of the present work was to apply solvent extraction using bis(2-ethylhexyl) phosphate (D2EHPA) in order to maximize the indium concentration in the solution. Firstly, the extraction and stripping steps were investigated using a synthetic solution. After definition of the best conditions using a synthetic solution, a real solution obtained from the leaching of discarded LCDs was employed.

Supercritical extraction of polymers from printed circuit boards using CO2 and ethanol

The printed circuit boards are the fundamental components of waste electrical and electronic equipment (WEEE). The PCBs stand out due to the amount of metals in their composition as well for their complex and heterogeneous constitution that make their recycling difficult. In this context, the aims of the study was to evaluate the application of supercritical CO2 modified with ethanol in order to remove the polymers contained in PCBs from discarded mobile phones. The PCBs were characterized and an evaluation of the supercritical extraction was performed through experimental design. The characterization showed that PCBs contained 64.02wt% of metals, 20.51wt% of ceramics and 15.47wt% of polymers. The fractional factorial experimental design showed that 69.53wt% of the polymers present in the PCBs were extracted, at 170°C and 7.5MPa. As the remaining polymers are no longer covering the metals, they could be more easily leached and therefore more effectively recovered.

Characterisation of Printed Circuit Boards of Mobile Phones Discarded in Brazil

The characterisation of printed circuit boards (PCB) removed from discarded mobile phones in Brazil and an inventory of data of the components in PCB were accomplished in this paper. Data of chemical composition of PCB were obtained from the physicochemical characterisation of their components through the analysis of granulometry, scanning electron microscopy with energy dispersive x-ray detector (SEM/EDS), infrared spectroscopy (FT-IR) and inductively coupled plasma optical emission spectrometry (ICP-OES). The analysis allowed a broad view and a highlight for the wide variety of elements and heterogeneity of the material. It can be also highlighted the high amount of copper, lead and other high-value metals in the PCB. This study is relevant for the development of new recycling technologies, once this material has been discarded incorrectly in Brazil. Based on the percentage of mobile phones recycled and disposed in Brazil, it is possible to quantify financial loss resulting from incorrect disposal.

Research on the Influencing Factors of Beijing Residents’ Used Mobile Phones Network Recycling Willingness

The rapid replacement of mobile phones make our country faces serious recycling situation. How to drive residents to actively participate in the regular network recovery, it is worth exploring. Aiming at this problem, this paper use the TPB theory as the instruction and structural equation model for research method. In-depth analysis of the influence factors of Beijing residents to participate in the discarded mobile phones will, in order to put forward suggestions for improvement, enhance the residents' participation.