Waste Circuit Boards Research Articles

Electrocatalytic degradation of ofloxacin by self-doped copper/carbon cathode materials derived from waste printed circuit boards

Using residual copper metal from waste circuit boards, ordered carbon materials containing copper (PCBs-Cu-800) were synthesized by self-doping for the electrocatalytic degradation of ofloxacin (OFL). Although PCBs-Cu-800 has a smaller specific surface area, its efficiency in degrading OFL was higher than that of carbon materials without copper (PCBs-800), reaching 95.9 % within 2 h. The PCBs-Cu-800 electrode can generate a large amount of H2O2 in the initial stage of degradation, thereby increasing the amount of hydroxyl radicals (·OH) generated and removing OFL. Density functional theory simulations were used to calculate the adsorption energies of O2 on both materials, demonstrating that the self-doped copper model was more prone to O2 adsorption, and elucidating the excellent electrocatalytic performance of PCBs-Cu. The residual copper metal in the raw material is important in the electrocatalytic processes. This study presents an environmentally friendly catalytic material capable of effectively degrading OFL in solution using waste circuit boards and further expands the application scope of advanced electrochemical oxidation technology in wastewater treatment.

New insights into brominated epoxy resin type WPCBs pyrolysis mechanisms: Integrated experimental and DFT simulation studies

Pyrolysis is a recycling technology for waste circuit boards (WPCBs) with a wide range of applications. In this research, the brominated epoxy resin (BER) type WPCBs were taken as the research object, and the optimal pyrolysis process parameters were determined. Combined with experiments and density functional theory (DFT) calculations, the pyrolysis gaseous generation pattern and product distribution of BER type WPCBs were analyzed, and the generation mechanism of phenol, bromide and other pyrolysis products was investigated in depth. The results of the study showed that the pyrolysis rate of WPCBs exceeded 95 % under optimal reaction conditions. In the initial phase of the pyrolysis of WPCBs, the BER's CO bonds and a portion of Ph-Br bonds will be broken, leading to the production of intermediates such propylene oxide, bisphenol A, isopropyl alcohol, tetrabromobisphenol A and HBr. Among them, propylene oxide can generate ethylene oxide through free radical reaction. In the second stage, intermediates such as bisphenol A undergo homolytic cleavage and radical addition to form phenols, bromides, alcohols, ketones and other pyrolysis products.

A sustainable reuse of e waste as a partial replacement material for aggregate

About 10 percent of E-Waste is produced in India annually. The present study is to utilize the E-Waste or Electronic waste such as circuit board waste, wires, and cables as a substitute for Coarse Aggregate (CA) and Fine Aggregate (FA). Since much of the waste are dumped into the soil grounds causes contamination of ground water, so it disturbs the plant growth and human health cycle. The waste can be utilized as much as possible to make a sustainable environment. Different combinations of about 5, 10 and 20% of the waste were much included as the substitute for FA and 10% as for CA. The samples are tested for specific gravity, consistency, compression testing, flexural strength, and split tensile strength. The results obtained serve as a feasible solution for E-management waste. Beyond 10% replacement of both coarse and fine aggregate the strength reduces than the required strength.

Debromination of Waste Circuit Boards by Reaction in Solid and Liquid Phases: Phenomenological Behavior and Kinetics

The debromination of waste circuit boards (WCBs) used in computer motherboards and components has been studied with two different pieces of equipment. Firstly, the reaction of small particles (around one millimeter in diameter) and larger pieces obtained from WCBs was carried out with several solutions of K2CO3 in small non-stirred batch reactors at 200-225 °C. The kinetics of this heterogeneous reaction has been studied considering both the mass transfer and chemical reaction steps, concluding that the chemical step is much slower than diffusion. Additionally, similar WCBs were debrominated using a planetary ball mill and solid reactants, namely calcined CaO, marble sludge, and calcined marble sludge. A kinetic model has been applied to this reaction, finding that an exponential model is able to explain the results quite satisfactorily. The activity of the marble sludge is about 13% of that of pure CaO and is increased to 29% when slightly calcinating its calcite at only 800 °C for 2 h.

Effect of Microwave Pretreatment on the Leaching and Enrichment Effect of Copper in Waste Printed Circuit Boards.

The use of efficient and clean methods for the recycling of waste circuit boards is an ongoing challenge. In this research, the effect of microwave pretreatment on the leaching and enrichment of copper from waste print circuit board (WPCB) was studied. The morphology and chemical structure of WPCB particles before and after microwave pretreatment were analyzed by SEM/EDS and Fourier infrared spectroscopy. Leaching experiments and copper enrichment tests were designed to investigate the effect of different microwave irradiation powers and microwave irradiation times on the copper leaching rate and copper enrichment rate in WPCB. The leaching experiment results showed that microwave pretreatment can effectively improve the leaching rate of WPCB. When the microwave irradiation power was 700 W, the irradiation time was 120 s, and the leaching time was 15 min, the copper leaching rate in WPCB was 57.01%, which was 24.34% higher than that in the untreated condition. The results of copper enrichment experiment show that microwave pretreatment can effectively improve the copper enrichment of WPCB. After microwave pretreatment, copper was effectively enriched in the 4-2 and 2-1 mm particle sizes. When the microwave irradiation time was 120 s, the copper enrichment rates in the 4-2 and 2-1 mm particle sizes were 1.74 and 1.66, which increased by 0.63 and 0.32, respectively, compared to the untreated condition. Microwave pretreatment enables the effective separation of metallic copper from non-metallic components in WPCB, increasing the exposure area of copper and promoting the monomer separation of copper, thus improving the leaching and enrichment of copper.

Occurrence and distribution characteristics of PCBs and PBDEs in farmland soils adjacent to electronic circuit board dismantling ruins

The Nanwan village, a green ecological village in Taizhou city, is used as a recycling area (recycling for heavy metal) for electronic circuit boards and as crushing and stacking sites of waste circuit boards for nearly 20 years from 1980s to 2000s. At present, although the e-waste recycling activities in Taizhou city have been effectively controlled, and many areas polluted by the e-dismantling activities have been gradually remediated except Nanwan village. Nanwan village seems to have been forgotten for its special geographical location, which has attracted our attention because of its ecological and food safety issues. Accordingly, the content of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the surface soil around the ruins and four edible agricultural crops were investigated. The main conclusions are as follows: among the four dismantling ruins and surrounding soil samples investigated, the content of Σ20PCBs in vegetable field topsoil of 2(20) is 1,321.3 ± 132.1 μg kg−1; the content of Σ8PBDEs in the paddy soil of 3(1S) is 7,216.9 ± 232.0 μg kg−1; biological toxicity events are likely to occur frequently in 2(20) and 3(1S). PCBs and PBDEs have both horizontal diffusion in distance and vertical diffusion in depth. The lifetime carcinogenic and non-carcinogenic risks of PCBs and PBDEs are at a low risk level, except for the non-carcinogenic risk of PCBs for children in 3(1S). The lifetime carcinogenic and non-carcinogenic risks of PCBs and PBDEs in the edible parts of garlic, ginger, mung beans, and oranges were all at acceptable or negligible levels.

Analysis of the effect of heating rate on pyrolysis kinetics and product composition of copper-containing waste circuit boards.

Pyrolysis is a cost-effective and environmentally benign method for recycling organic waste, which can be converted into high-energy gases and oils. Pyrolysis technology was employed in this study to recycle copper-containing discarded circuit board material and recover copper, glass fibers, and gases and oils with high calorific values. Thermogravimetric analyses (TGA), Fourier transform infrared spectroscopy (FTIR), and gas chromatography-mass spectrometry (GC-MS) were used to evaluate pyrolyses of copper-containing waste circuit board materials conducted at different heating rates (5, 10, 20, and 40°C/min), and the resulting volatiles were studied in detail. The effects of heating rate on the kinetics and activation energies for pyrolyses of copper-containing waste circuit boards were also investigated by using the Coats-Redfern (C-R) method. The TGA curves and FTIR spectra did not differ significantly for different heating rates, and the main functional groups identified with the FTIR results were O-H, C = C, aromatic benzene, substituted benzene, and C-Br. Additionally, GC-MS analyses showed that the heating rate had a great influence on the pyrolysis products formed; the phenol content decreased with increasing heating rate, and the highest content was realized at 5 ℃/min. Energy dispersive spectroscopy (EDS) analyses showed that bromine was removed from the solid phase products during pyrolysis, while copper was effectively enriched in the feedstock. This indicated that pyrolysis can be used to recover copper-containing waste circuit boards.

Effects of waste printed circuit board powder on strength, durability and microstructure of cement-based materials

A large number of waste printed circuit boards(WPCB) have caused extremely serious pollution problems to the environment. Two different particle sizes of waste printed circuit boards powders are incorporated into the cement-based material as an admixture to study its effect on the mechanical strength and durability of the cement-based material. The results show that WPCB powder can improve the compressive strength and flexural strength of cement-based materials. At the same time, WPCB powder can improve the freeze-thaw resistance and sulfate corrosion resistance of cement-based materials. The study also finds that when the mechanical strength and durability of the mortar are optimal, the content of fibrous WPCB powder is 1%, while the content of granular WPCB powder is 2.5%. The article also analyzes the improvement mechanism of WPCB powder on the mechanical properties and durability of cement mortar through porosity test, FTIR test and SEM test. The test results provide further theoretical research on the application of waste circuit boards in cement-based materials, and provide a new solution for reducing the pollution of WPCB to the environment.

Debromination and Reusable Glass Fiber Recovery from Large Waste Circuit Board Pieces in Subcritical Water Treatment.

The great economic, social, and environmental interest that favors an effective management of the recycling of waste printed circuit boards (WCBs) encourages research on the improvement of processes capable of mitigating their harmful effects. In this work, the debromination of large WCBs was first performed through a hydrothermal process employing potassium carbonate as an additive. A total of 32 runs were carried out at 225 °C, various CO32–/Br– anionic ratios of 1:1, 2:1, 4:1, and 6:1, treatment times from 30 to 360 min, proportion of submerged WCBs in the liquid of 100, 50, and 25% that corresponded with the use of three WCB sizes of 20 mm × 16.5 mm, 20 mm × 33 mm, and 80 mm × 33 mm, respectively, and solid/liquid ratios of 1:2 and 1:1 g/mL without other metallic catalysts. A debromination efficiency of 50 wt % was reached at only 225 °C (limited by mechanical reasons) and 360 min, using a CO32–/Br– anionic ratio of 4:1 and a solid/liquid ratio of 1:2 for a large WCB with only 25% of its volume submerged in the liquid. This means conservation of water and energy compared to previous studies. A muffle furnace was used later to thermally treat a total of 101 debrominated samples, at constant temperature or following a temperature scaling program. An estimated decrease in resistance to rupture of glass fibers of only around 50% was accomplished by following a temperature scaling program up to 475 °C, obtaining clean glass fibers of large size. The simple techniques proposed to obtain reusable glass fibers from WCBs as large as the size of the reactor allows (as it might be in their original size) could significantly improve interest in the industry.

Steam gasification assisted pyrolysis directional de bromination of waste printed circuit boards and comprehensive utilization of products

Due to the large amount of brominated flame retardants contained in waste printed circuit boards, their incineration treatment has caused great harm to the environment. Conventional heat pyrolysis is used to treat used circuit boards, resulting in more contaminating waste due to the production of brominated gases and dioxins. In this paper, the steam atmosphere heating method is used to pyrolyze the crushed waste circuit board under optimized conditions (700 °C, 20 °C/min, 60 min, 2 mL/min). Pyrolysis residues, pyrolytic oils and pyrolysis gases were obtained, and the mass ratios were 65.47 wt%, 27.32 wt% and 7.21 wt% respectively. The bromine content in the residue is reduced to 0.005 wt%, and the content of metallic copper is 28.69 wt%, which can be used as a raw material for the collaborative smelting of copper. About 94 wt% of the bromine in the raw material is transferred to water, which can be effectively recovered as a raw material. These results result in a reduction in hazardous pollutants. Compared with conventional heating pyrolysis, steam atmosphere heating not only reduces energy consumption, but also reduces the production of brominated products and toxic substances, and promotes the subsequent utilization of pyrolysis products. This paper reports on the heating pyrolysis of steam atmospheres on waste printed circuit boards, and this study provides a new method for removing bromine from the pyrolysis process.

Classification and Positioning of Circuit Board Components Based on Improved YOLOv5

With the development of electronic technology, the amount of electronic solid waste is increasing. The waste circuit board has lost its original function, but some components have not yet reached the standard of scrapping, and can be dismantled by dismantling. Recycle it and use it on a new circuit board. Aiming at the problem of automatic dismantling and recycling of electronic components on circuit boards, a combined algorithm based on YOLOv5 and hierarchical classification algorithm is proposed. First, images of components with similar features and indistinguishable features are integrated into new category data, and a classification model is trained after cropping. Second, the output of the YOLOv5 network is subdivided into predicted categories by the classification network, and then the output of YOLOv5 is redistributed to complete the recognition. Finally, the algorithm is applied to the detection and identification of circuit board components. It can be seen from the experimental results that the combined algorithm has high recognition accuracy and accuracy in the classification and positioning of circuit board components. The algorithm effect is 38% higher than the original YOLOv5 model.

Risk Analysis and Accident Causes of Mobile Phone Charger

All kinds of mobile phone chargers in the actual use process, due to poor quality products or improper use will cause safety accidents, causing great harm, so this paper has great practical significance to study the use risk and accident causes of mobile phone chargers. First of all, through the failure of insulating materials between conductive parts of mobile phone charger, the use of substandard artificial plug-ins in the production of components, the use of waste circuit boards or circuit board aging, and the unqualified quality of high-frequency transformer, the use risk and reasons of inferior products are analyzed. Secondly, the risks and causes of improper use of mobile phone chargers are analyzed by analyzing the factors such as alternate mixing of different specifications of mobile phone chargers, using mobile phone while charging, and long-term plugging in the socket. Finally, three typical cases of accidents caused by the breakdown of the insulation between the conductive parts of the mobile phone charger, the excessive current at the output end, and the defects of the material are analyzed, which provides better technical support for better eliminating the hidden dangers of the mobile phone charger.

Selective recovery of precious metals through photocatalysis

Precious metals such as gold and platinum are valued materials for a variety of important applications, but their scarcity poses a risk of supply disruption. Recycling precious metals from waste provides a promising solution; however, conventional metallurgical methods bear high environmental costs and energy consumption. Here, we report a photocatalytic process that enables one to selectively retrieve seven precious metals—silver (Ag), gold (Au), palladium (Pd), platinum (Pt), rhodium (Rh), ruthenium (Ru) and iridium (Ir)—from waste circuit boards, ternary automotive catalysts and ores. The whole process does not involve strong acids or bases or toxic cyanide, but needs only light and photocatalysts such as titanium dioxide (TiO2). More than 99% of the targeted elements in the waste sources can be dissolved and the precious metals recovered after a simple reducing reaction that shows a high purity (≥98%). By demonstrating success at the kilogram scale and showing that the catalysts can be reused more than 100 times, we suggest that this approach might be industry compatible. This research opens up a new path in the development of sustainable technologies for recycling the Earth’s resources and contributing to a circular economy.

Study on Water Model Experimental of Waste Circuit Board Treatment by Top-Blowing Bath Smelting Method

Through the water model experiment of oxygen-enriched top-blowing bath smelting, the effects of factors such as gas flow, lance position and liquid height on the bubble size distribution and liquid splash height during top blowing process of waste circuit boards were studied. The results showed that, the mixing effect worked best when the lance blew in the center of the molten pool. With a suitable increase of the gas flow, the impact of bubble refinement in the molten pool can be optimized. At the same time, the liquid splash, slag entrapment and liquid level fluctuation were aggravated. Appropriately increasing the liquid height can inhibit liquid splash to a certain extent. Considering the effect of bubble refinement and liquid splash height, the optimal experimental conditions of this experimental system were as follows. A straight barrel lance with a diameter of 15mm was installed in the center of the furnace body, the liquid height was 80mm, the lance submersion depth was 40mm, and the gas flow was 7.48Nm3/h.

Study on Gold Extraction Process of Printed Circuit Board Based on Thiourea Method

The printed circuit board is rich in recyclable metals Cu, Au, Ag, Pt, Pb, etc. The precious metals such as gold are extracted from it, which is in line with the concept of resource recycling. In this paper, the theorem method was used to extract gold from waste circuit boards. The effects of reaction time, reaction temperature, theorem concentration, and Fe3 + mass concentration on gold leaching rate were investigated. The results showed that the pH was controlled at about 1, the theorem concentration was 0.12 mol/L, FeCl3 was 0.024 mol/L, the stirring speed was 300 r/min, and the leaching time was 2 h. Under the above conditions, the gold leaching rate reached 90.37 %. The theorem gold extraction method has certain potential application values due to its rapid gold dissolution, low toxicity during leaching, low price, high efficiency, and environmental protection.

Investigation and analysis of occupational exposure factors in an enterprise processing waste electronic products

Objective: To identify and to analyze occupational exposure factors generating from production process in an enterprise processing waste electronic products, to provide scientific evidences for protection measures. Methods: From June to October 2017, seven waste electrical and electronic product processing enterprises in a province were selected as the research objects. These seven enterprises all include refrigerator dismantling line, washing machine dismantling line, air conditioning dismantling line, TV/computer dismantling line, CRT cutting line. Some enterprises also have circuit board line, wet precious metal recycling line, plastic crushing line, plastic granulating line and other deep processing operations such as precious metal recycling of waste circuit board, waste plastic crushing and recycling. The data were collected by the methods of occupational health field investigation and occupational health testing, and the exposure level of occupational hazard factors was evaluated by combining the effect of the protective facilities of occupational health engineering. Results: the main occupational hazard factors of waste electrical and electronic products treatment enterprises were dust, noise, heavy metal, flame retardant, mercury, fluoride, cyanide, sodium hydroxide, hydrochloric acid and nitric acid. 145 effective samples were obtained from heavy metal sampling, including 102 individual samples and 43 fixed-point long-term samples. Among them, 8 samples lead exceeded the standard, all occurred in the TV dismantling line. In addition to flame retardants, plasticizers, insecticides and other components can be detected by high-throughput qualitative analysis using liquid chromatography-time-of-flight mass spectrometry. Finally, 123 effective 8-h equivalent sound level values were obtained by individual noise detection, 86 of which exceeded the standard, with a rate of 69.9%. Conclusion: there are potential occupational hazards in the process of dismantling waste electrical and electronic products.

Bromine removal from resin particles of crushed waste printed circuit boards by vacuum low-temperature heating

Uncontrolled dumping and incineration of resin particles of waste printed circuit boards had caused serious pollution due to the contained brominated flame retardants. High-temperature vacuum pyrolysis was proposed to treat the resin particles. However, due to the generation of brominated gases and solid floc, high-temperature vacuum pyrolysis reproduced more hazardous wastes. In this paper, resin particles of crushed waste circuit board were processed by vacuum heating at the temperature of 300 °C and condensation at 180 °C. Resin particles were converted into residue and oil with the mass ratios 84.0 wt% and 16.0 wt% respectively. Content of organic bromine in residue was reduced to 0.082 wt%. Meanwhile, morphology of resin in residue was basically unchanged, which could be directly recycled as the filler for building materials. About 95.4 wt% of bromine in resin particles was transferred to oil. These results achieved the reduction of the hazardous wastes. Compared with the high-temperature vacuum pyrolysis, low-temperature heating not only reduce energy consumption, but also reduce the generation of toxic products. This paper might be the first time to report low-temperature heating of resin particles of waste printed circuit boards. This study contributed a novel technology to remove bromine from brominated substrates.

Recycling Waste Circuit Board Efficiently and Environmentally Friendly through Small-Molecule Assisted Dissolution

With the increasing amount of electronic waste (e-waste) generated globally, it is an enormous challenge to recycle printed circuit boards (PCBs) efficiently and environmentally friendly. However, conventional recycling technologies have low efficiency and require tough treatment such as high temperature (>200 °C) and high pressure. In this paper, a small-molecule assisted approach based on dynamic reaction was proposed to dissolve thermosetting polymers containing ester groups and recycle electronic components from PCBs. This effective approach operates below 200 °C and the polymer could be dissolved in a short time. It has a remarkable ability to recycle a wide range of commercial PCBs, including boards made of typical anhydride epoxy or polyester substrate. Besides, it is environmentally friendly as even the recycling solution could be reused multiple times. In addition, the wasted solution after recycling could be used for board bonding and damage repair. This work also demonstrates the advantage of using polymers containing ester groups as the PCB substrate in consideration of eco-friendly and efficient recycling.

Ball milling recovers copper from old circuit boards

A new method for extracting copper from waste circuit boards takes advantage of ball milling, a brute-force means of jump-starting chemical reactions (Environ. Sci. Technol. 2019, DOI: 10.1021/acs....

Separation and Recovery of Metallic foil from Waste Circuit Boards Using Induction Heating

Separation and Recovery of Metallic foil from Waste Circuit Boards Using Induction Heating