Waste Printed Circuit Boards Powder Research Articles

A Green Slurry Electrolysis to Recover Valuable Metals from Waste Printed Circuit Board (WPCB) in Recyclable pH-Neutral Ethylene Glycol

The continuous growth of e-waste necessitates an efficient method to recover their metal contents to improve their recycling rate. The successful recovery of the metallic component from Waste Electrical and Electronic Equipment (WEEE) can generate great economic benefits to incentivize the industrial recycling effort. In this study, we report the use of slurry electrolysis (SE) in pH-neutral ethylene glycol (EG) electrolyte to extract and recover the metallic component from waste printed circuit broad (WPCB) powder. The system operates at room temperature and atmospheric pressure, and the electrolyte can be recycled multiple times with no signs of chemical degradation. The EG electrolyte system can oxidize the metallic component without triggering anodic gas evolution, which allowed us to incorporate a reticulated vitreous carbon (RVC) foam anode to maximize the capture and oxidation of the metal content. The system demonstrated up to 99.1% Faraday efficiency for the cathodic metal deposition and could recover Cu from the WPCB powder in a selective manner of 59.7% in the presence of 12 other metals. The SE reaction system was also scalable and displayed no compromises on the Cu recovery selectivity. With the ability to leach and recover metallic content from WPCB in a mild and chemically benign condition, the SE system displayed much promise to be adapted for industrial-scale metal recovery from WPCB. Reference Liu, K., Lam, JCH. et al. "A green slurry electrolysis to recover valuable metals from waste printed circuit board (WPCB) in recyclable pH-neutral ethylene glycol." J. Hazard. Mater. 2022433: 128702.Liu, K., Lam, JCH. et al. "Teaching Electrometallurgical Recycling of Metals from Waste Printed Circuit Boards via Slurry Electrolysis Using Benign Chemicals." J. Chem. Educ. 2023 100(2): 782-790. Figure 1

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.

Facile path for copper recovery from waste printed circuit boards via mechanochemical approach

Recycling copper (Cu0) from waste printed circuit boards (PCBs) is a prevalent challenge. Here, we propose a new pathway and reveal mechanisms for recovering Cu0 from waste PCBs via a mechanochemical approach. The successful application of mechanical force avoids using inorganic acid in the Cu0 recovery process. Our work demonstrates that ferric chloride (FeCl3) was superior to ferric sulfate and ferric nitrate as a solid-phase reagent for Cu0 recovery due to chloride complexation. Under the induction of mechanical force, the Cu0 in the waste PCBs was oxidized by Fe3+ and complexed by Cl¯ to form a meta-stable cuprous chloride, which was susceptible to leaching in an acidic liquid-phase system constructed by hydrolysis of ferric salt. Further mechanism analysis reveals that in the mechanochemical solid-phase reaction, Cu0, metallic impurities, metal oxides, and carbon materials from waste PCBs could also reduce Fe3+ to Fe2+. The optimum conditions for Cu0 recovery from waste PCB powder with FeCl3 as a solid-phase reagent were: rotational speed of 500 rpm, Cu0:Fe3+ molar ratio of 1:20, and reaction time of 120 min, achieving the highest recovery of 99.6 wt%. This study presents a facile path for Cu0 recovery from waste PCBs for resource circulation.

A green slurry electrolysis to recover valuable metals from waste printed circuit board (WPCB) in recyclable pH-neutral ethylene glycol

The continuous growth of e-waste necessitates an efficient method to recover their metal contents to improve their recycling rate. The successful recovery of the metallic component from Waste Electrical and Electronic Equipment (WEEE) can generate great economic benefits to incentivize the industrial recycling effort. In this study, we report the use of slurry electrolysis (SE) in pH-neutral ethylene glycol (EG) electrolyte to extract and recover the metallic component from waste printed circuit broad (WPCB) powder. The system operates at room temperature and atmospheric pressure, and the electrolyte can be recycled multiple times with no signs of chemical degradation. The EG electrolyte system can oxidize the metallic component without triggering anodic gas evolution, which allowed us to incorporate a reticulated vitreous carbon (RVC) foam anode to maximize the capture and oxidation of the metal content. The system demonstrated up to 99.1% Faraday efficiency for the cathodic metal deposition and could recover Cu from the WPCB powder in a selective manner of 59.7% in the presence of 12 other metals. The SE reaction system was also scalable and displayed no compromises on the Cu recovery selectivity. With the ability to leach and recover metallic content from WPCB in a mild and chemically benign condition, the SE system displayed much promise to be adapted for industrial-scale metal recovery from WPCB.

Fabrication and Mechanical Properties of High-Durability Polypropylene Composites via Reutilization of SiO2 In-Situ-Synthesized Waste Printed Circuit Board Powder.

This paper focuses on the characterization of the physico-chemical properties, surface modification, residual copper content and in situ hybrid inorganic particle modification of polypropylene (PP) composites reinforced by waste printed circuit board powder (WPCBP). A series of WPCBP/SiO2 hybrids (TSW) were prepared by a sol–gel method at different pH values. Characterization results revealed the in situ generation of SiO2 on the surface of WPCBP, and showed that with an increase in pH value, the size of SiO2 particles increased gradually and the copper content decreased in the TSW powder. The mechanical properties, oxidation induction time (OIT) and thermal properties of PP composites were improved by reinforcement with TSW, which might be ascribed to the formation of serrated interfaces. This work not only develops a powerful method to enhance the properties of PP/WPCBP composites, but also provides an environmentally sustainable approach to the high-added-value reutilization of WPCBP.

EFFECT OF 5 WT.% WPCB POWDER AS REDUCTANT ON INDONESIAN NICKELIFEROUS ORE PROCESSING

EFFECT OF 5 WT.% WPCB POWDER AS REDUCTANT ON INDONESIAN LIMONITICNICKEL ORE PROCESSING. Waste printed circuit boards (WPCB) are among the most valuable parts of electronic waste with one of the fastest-growing waste streams in the world. The purpose of this study is to investigate the possibility of WPCB powder as an alternative reducing agent for the carbothermic process in nickel lateritic ore processing. WPCB waste was mixed with nickel ore at 1100ÚC in inert atmosphere. In addition, a conventional reductant of coal is also utilized for comparison. Both reductant are varied in concentration of 5 wt% and 15 wt%. Based on thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTA) investigation, it is observed that there exists a difference between WPCB powder, nickeliferous ore powder, and the mixture in their decomposed levels. The decomposed gasses of WPCB produced by thermal degradation in the TGA instrument are mainly composed of reduction gas, which plays a critical role in reducing the nickeliferous ore. This study shows that WPCB powder performs comparably to sub-bituminous coal in the pyrometallurgical processing of nickel ore, which is proved by X-Ray Diffraction (XRD) test results that the carbothermic products consists of FeNi, magnetite, wustite and fayalite. It can be concluded than WPCB powder has potential to be utilize as an alternative reductant.

Utilization of waste printed circuit board powder in concrete over conventional concrete

Generating waste in the current society is an emphasis to handle and segregate the E-waste materials to avoid the environmental impact and control the pollution. From the viewpoint of the construction industry, we care about the Manufacturing of cement industries and demolition waste results in evident pollution effects. The limelight of the research is eliminating the solid waste, and to engross this waste materials in the Concrete. The Printed Circuit Board (PCB) from all the Electrical devices is crushed and converted into ash which is utilized as the replacement for the fine aggregate to a certain percentage of replacement. The presence of silicon (Si) content in the PCB helps to fulfill the requirement as similar to the fine aggregate. Today lots of electrical and electronic waste from households like motherboard from the computer peripheral, video games, damaged or crashed television, home theatres, etc., the PCB which is destroyed from those products is not reused or recycled for the new products. On focus to the dumping of such electrical waste, it is processed and converted into fine powder to utilize as fine aggregate (FA) in the concrete specimens. Natural fine aggregate can be reduced to a certain limitation by using the crushed PCB powder as a replacement with 3%,5%, 10%, 15%, 20% and, 25% by weight. It is found that the strength of the concrete is improved and PCB can be partially used as fine aggregate replacement.

Recycling metals from -0.5 mm waste printed circuit boards by flotation technology assisted by ionic renewable collector

Metals in −0.5 mm waste printed circuit boards (WPCBs) are effectively recycled by flotation technology. Ionic renewable collector was prepared from waste oils and subsequently used in flotation of −0.5 mm WPCBs. Morphology of renewable collector and WPCBs powder was detected by scanning electron microscope (SEM). Laboratory flotation tests were conducted to analyze the flotation performance. The adsorption behavior of the collector was revealed by infrared spectroscopy (FT-IR). SEM results show that the particle size of collector is in the micron scale and the impurity particles in WPCBs are in strip shape. Organic matter is proved to exist on the glass fibers surface, which helps to enhance its hydrophobicity. FT-IR analysis results indicate that both the collector and WPCBs powder contain hydrophobic and hydrophilic groups, which help to increase the attachment point of collector to strengthen the flotation process. Laboratory flotation test results show that the concentrate yield decreases with the increase of collector dosage. When the collector dosage is 2 kg/t, copper and iron grade in concentrate reaches 31.32% and 37.28% with the recovery of 65.75% and 14.55%, respectively. The study has provided an alternative method for the recycling of metals in WPCBs.

Bioleaching of gold from waste printed circuit boards by alkali-tolerant Pseudomonas fluorescens

This paper evaluated the ability of Pseudomonas fluorescens to leach gold from waste printed circuit boards (WPCBs). Gold was recovered as gold-cyanide complex and cyanide was produced by Pseudomonas fluorescens. In this paper, the effect of pH on gold leaching efficiency was studied, the P.fluorescens was domesticated to grow at higher pH (pH 8 and 9), and the concentration of cyanide ions (CN−) available for bioleaching was increased in alkaline pH. The results showed that at 0.67% w/v pulp density of pretreated waste printed circuit boards powder, mutated bacteria attained gold biorecovery of 27% at pH 9, while the unadapted bacteria only 23% of bioleaching efficiency was achieved. Results revealed that bioleaching efficiency of gold from waste printed circuit boards decreased with the increase of pulp density, and 0.33% w/v pulp density had the maxnium influence to bioleaching efficiency of gold, which could reach 42%. In the two-step bioleaching process, the initial amounts of bacteria had a certain impact on the leaching efficiency, and 3.33% v/v of the initial bacterial liquid was a suitable addition. The type of substrate also affected the leaching bioleaching efficiency. The leaching efficiency in the later stage of gold leaching will be greatly improved to 54%, when glycine and methionine were added to the medium for cyanide production. This may be due to positive effect by the methionine, which could regulate the glycine pool of the cells.

Mechano-microbial systems: An ecofriendly approach for copper bioleaching from waste printed circuit board.

Waste printed circuit board (PCB) is attracting serious concerns because the recycling of its valuable metallic portion is made difficult by the existence of hazardous substances. The objective of the present study was to develop a simplified approach for copper bioleaching from waste PCB. In this context, we intended mechano-microbial systems symbolized as SET-I (spore suspension + potato dextrose broth medium + waste PCB powder), SET-II (pre-cultured until the logarithmic phase, without waste PCB powder), and SET-III (fungal metabolites produced at stationary phase). The results of bioleaching studies showed that the developed method achieved the highest copper leaching of 85% by the SET-III approach. This study provides an insight for bioleaching copper from waste PCB. Furthermore, this approach can be established as an ecofriendly method for copper bioleaching by using an integrated system.

Facile and Cost-Effective Approach for Copper Recovery from Waste Printed Circuit Boards via a Sequential Mechanochemical/Leaching/Recrystallization Process.

The recovery of copper (Cu0) from waste printed circuit boards (WPCBs) is a great challenge as a result of its heterogeneous structural properties, with a mixture of metals, epoxy resin, and fiberglass. In this study, a three-step sequential process, including mechanochemical processing, water leaching, and recrystallization, for Cu0 recovery from WPCB powder is reported. Potassium persulfate (K2S2O8), instead of acid/alkali reagents, was employed as the sole reagent in the cupric sulfate (CuSO4) regeneration process. Complete oxidation of Cu0 in the WPCBs to copper oxide (CuO) and CuSO4 was first achieved during mechanochemical processing with K2S2O8 as the solid oxidant, and the K2S2O8 was simultaneously converted to sulfate compounds [K3H(SO4)2] via a solid-solid reaction with epoxy resin (C nH mO y) as the hydrogen donator under mechanical force. The rapid leaching of Cu species in the forms of CuO and CuSO4 was therefore easily realized with pure water as a nontoxic leaching reagent. The kinetics of the leaching process of Cu species was confirmed to follow the shrinking nucleus model controlled by solid-film diffusion. Finally, CuSO4·5H2O was successfully separated by cooling crystallization of the hot saturated solution of sulfate salt [K2Cu(SO4)2·6H2O]. An efficient conversion of Cu0 to CuSO4·5H2O product, for WPCB recycling, was therefore established.

The leaching behaviour of Cu, Zn and Pb from waste printed circuit boards by [BSO<SUB align="right">4HPy]HSO<SUB align="right">4

Currently, researches are mainly focused on how to recycle valuable metals from waste printed circuit boards (WPCBs), but rarely on the toxic substances, such as zinc and lead, during the recycling process. In this research, the effect of zinc and lead during the process of leaching copper from WPCBs by an acidic ionic liquid (IL), N-sulfobutylpyridinium hydrosulphate ([BSO4HPy]HSO4), was investigated in detail. Results showed that copper and zinc could be successfully leached out by [BSO4HPy]HSO4. When 1 g of 0.1 to 0.25 mm WPCBs powder was leached by 25 mL of 80% (v/v) ionic liquid and 10 mL of 30% hydrogen peroxide at 40°C for 2 h, copper and zinc leaching rate could be up to 99.75% and 93.02%, respectively. H2O2 added amount, solid-liquid ratio and temperature could significantly impact the leaching rate of copper and zinc. On the contrary, lead leaching rate is hardly influenced by these factors, maintaining at around 2%. Thus, during the leaching process, zinc could significantly influence the leaching of copper, which was totally different for lead. Leaching kinetics analysis indicated that the leaching of copper and zinc is controlled by solid film diffusion, and the leaching of lead is controlled by chemical reaction.

A new chelating resin from waste printed circuit board powder

An aminated resin was prepared by using the waste printed circuit board(WPCB) powder-with brominated epoxy resin as the polymer matrix material- pretreated with acid and alkali- then modified using diethylenetriamine. A novel chelating resin containing a dithiocarbamate(DTC) group was synthetized with the reaction by the aminated resin- carbon disulfide and Sodium hydroxide. It was characterized by FTIR and 13C NMR. The adsorption effects of the modified materials on heavy metal ions were investigated, and the results showed that DTC-WPCB have well adsorption performance on Ag+.

Direct extraction of palladium and silver from waste printed circuit boards powder by supercritical fluids oxidation-extraction process

The current study was carried out to develop an environmental benign process for direct recovery of palladium (Pd) and silver (Ag) from waste printed circuit boards (PCBs) powder. The process ingeniously combined supercritical water oxidation (SCWO) and supercritical carbon dioxide (Sc-CO2) extraction techniques. SCWO treatment could effectively enrich Pd and Ag by degrading non-metallic component, and a precious metal concentrate (PMC) could be obtained, in which the enrichment factors of Pd and Ag reached 5.3 and 4.8, respectively. In the second stage, more than 93.7% Pd and 96.4% Ag could be extracted from PMC by Sc-CO2 modified with acetone and KI-I2 under optimum conditions. Mechanism study indicated that Pd and Ag extraction by Sc-CO2 was a complicated physiochemical process, involving oxidation, complexation, anion exchange, mass transfer and migration approaches. Accordingly, this study established a benign and effective process for selective recovery of dispersal precious metals from waste materials.

Materials Separation from Pulverized Waste Printed Circuit Boards

Pulverized waste printed circuit board powder is a complex mix of organic epoxy resin, glass fiber, and several different metals. The aim of this study was to investigate the feasibility of separating the components of the powder and then efficiently recovering the metals by magnetic separation. The organic resin was first decomposed by pyrolysis in an inert atmosphere. The pyrolysis gas was subject to chemical analysis, and the toxic components were successfully trapped. Magnetic and nonmagnetic components in the residue were then separated by magnetic force.