Slurry Electrolysis Research Articles

Effect of Membrane Pore Size on Copper Recycling from Waste Printed Circuit Boards by Slurry Electrolysis

Effect of Membrane Pore Size on Copper Recycling from Waste Printed Circuit Boards by Slurry Electrolysis

Short process for Li2CO3 synthesis and spent LiCoO2 remediation via Glycine-LiOH slurry electrolysis

Effectively recycling spent lithium-ion batteries (S-LIBs) has considerable economic and environmental benefits. In this study, a novel approach for simultaneously synthesizing Li2CO3 and remediating LiCoO2 from S-LIBs via slurry electrolysis is proposed, employing glycine-LiOH as the electrolyte. The operating conditions were optimized to a solid-to-liquid ratio of 20 g/L, slurry electrolysis time of 8 h, current density of 50 mA/cm2, reaction temperature of 80 °C, and glycine concentration of 1.0 mol/L. Li2CO3 was directly synthesized in the anode region, with a purity of up to 99.52 %. Additionally, LiCoO2 was partially remediated in the cathode, increasing Li-Co molar ratio from 0.659 to 0.93. The obtained Li2CO3 and the electrolysis residue LiCoO2 then underwent additional calcination, yielding a layered LiCoO2. At a Li-Co molar ratio of 1.1, the initial specific capacity of the calcined LiCoO2 material was 129.9 mAh/g, exhibiting a capacity retention rate of 50.48 % over 100 cycles. Therefore, a novel, cost-effective, and energy-saving strategy for recycling S-LIBs is proposed.

Rapid prediction of flow and concentration fields in solid-liquid suspensions of slurry electrolysis tanks

Rapid prediction of flow and concentration fields in solid-liquid suspensions of slurry electrolysis tanks

A cost-effective and short process for copper recovery from WPCBs of mobile phones by slurry electrolysis: Semi-scale certification

Waste printed circuit boards (WPCBs) are considered as the most complex and valuable part of the discarded mobile phone. Alkaline slurry electrolysis is certified as an effective method to recover copper from WPCBs of mobile phones (WPCB-MPs). To promote its industrial application, 5000 mL scale trials were conducted and the results show that: Electrolysis at 30 g/L WPCB-MPs, 25 g/L Cu2+(CuSO4·5H2O), 4 mol/L NH3·H2O, 0.5 mol/L NaCl, 0.5 mol/L NH4Cl, 20 mA/cm2 and 298 K for 8 h, the current efficiency is 90.47 %, the copper recovery is 92.04 %, and the purity of cathode copper is 99.79 %. Electrolyte circulation hardly affected current efficiency, copper recovery rate and copper purity, which were higher than 90 %, 90 %, and 99 %, respectively. The semi-scaled experiment demonstrates its feasibility in industrial application. Primarily cost analysis shows that producing a ton of cathode copper has a profit of about $5,144.5. Therefore, alkaline slurry electrolysis has a broad industrial prospect in WPCBs recycling.

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

A Large-Scale Electrometallurgical Treatment of Waste Printed Circuit Board (WPCB) in Ethylene Glycol for Metal Recovery

The accumulating generation of E-Waste is gaining more concern. This work reported an environmental-friendly approach, slurry electrolysis (SE), to highly effectively recover metals embedded in Waste Printed Circuit Board (WPCB). The reusable ethylene glycol (EG) is employed as the electrolyte, simple and cheap graphite rod, and copper strip function as anode and cathode, respectively. And it could operate at room temperature and pressure. EG can withstand for hours or days of electrolysis with no sign of degradation but evaporation. It has shown a good selectivity in the leaching solution with metal ions. The metals with high activity could be electrochemically oxidized but not reduced. The metals with low activity could undergo both. From the current results, the system has demonstrated a moderate faraday efficiency of the cathode of 67.7%, successfully recovered 95-97% copper from the real WPCB powder with 61% copper, 24% Al, 10% Zn, 3% Sn and some trace metals. Notably, the extracted metals are all in powder form and easily extractable, indicating that it requires only some facile treatments to make the powder eligible for replacement from mining. This study proved another novel approach to recovering metals from E-Waste on an industrial scale.

Recovering metallic lead from spent lead paste by slurry electrolysis

Spent lead paste, the most challenging component of discarded lead-acid batteries, contains approximately 70 % Pb. Improper handling of lead-acid battery waste poses severe risks to both the environment and human health. Here, we present a novel and short process for directly recycling metallic Pb from spent lead paste by chlorine slurry electrolysis and investigate the parameters that affect Pb recovery rate and cathodic current efficiency. Our experiments showed that under optimal conditions (250 g/L NaCl, 0.8 mol/L HCl, 10 g/L Pb2+, 30 A/m2, 40 g/L pulp concentration, 65 °C, and 12 h), the Pb recovery rate and cathodic current efficiency were, respectively, 90.54 and 85.25 %. During slurry electrolysis. Cl- combined with Pb in spent lead paste in the anode chamber, converting lead oxides and insoluble PbSO4 into soluble lead chloride complexes ([PbCl3]-, [PbCl4]2-). Driven by the electric field and concentration gradient, the lead chloride complex ions then migrated to the cathode region, where they were reduced to metallic Pb with a purity higher than 99 %. The application of this cost-effective and efficient novel method can contribute to the sustainable reuse of waste lead-acid batteries and other Pb-bearing scrap.

Electrochemical oscillation behaviors of gold during its recovery from waste printed circuit boards through slurry electrolysis

Slurry electrolysis is an effective technology for recovering gold from waste printed circuit boards (WPCBs). However, electrochemical oscillation during the gold recovery process is a potential factor affecting power consumption. As a result, the potential oscillation behaviors of gold dissolution at a constant current were studied. These results showed that the periodic formation and dissolution of the Au-OH passive film on the anode induced electrochemical oscillation. The amplitude and frequency of electrochemical oscillation were affected by hydrochloric acid concentration, current intensity, electrode spacing, and sodium chloride concentration, among which the concentration of sodium chloride had a significant inhibitory effect. Under the following conditions: hydrochloric acid concentration of 8 mol/L, current of 0.03 A, and electrode spacing of 1.5 cm, the obtained maximum amplitude potential and frequency were 1.17 V and 0.56 Hz, respectively. The phase space reconstruction results showed that the systems evolved between the near-linear equilibrium region and the periodic oscillation region. Different factors induced two oscillation modes: top-down and bottom-up. The top-down and bottom-up oscillations induced by current intensity, hydrochloric acid concentration, and electrode spacing reduced the relative power consumption by 11.8, 17.2, and 11.8 %, respectively, and increased the relative power consumption by 14.3, 21.2, and 30.1 %, respectively. A critical value was obtained, which varied oscillation patterns and gained a region of lower power consumption. The addition of trisodium citrate and PVP can improve gold recovery rate and current efficiency by regulating process of electrochemical oscillation. This work will provide theoretical support for recovering valuable metals from WPCBs with reduced energy consumption by controlling the external conditions to switch the oscillation mode.

Enhanced recovery of high-purity Fe powder from iron-rich electrolytic manganese residue by slurry electrolysis

Enhanced recovery of high-purity Fe powder from iron-rich electrolytic manganese residue by slurry electrolysis

Enhanced recovery of high purity Cu powder from reclaimed copper smelting fly ash by NH3·H2O–NH4Cl slurry electrolysis system

Reclaimed copper smelting fly ash (RCA) is a residue produced during the smelting process of waste miscellaneous copper, containing heavy metals such as Cu, Zn, and Cd. In this study, a slurry electrolysis system was used to recover Cu from RCA. The results showed that the recovery efficiency, current efficiency, and purity of Cu on cathode were 97.11 %, 91.22 %, and 98.47 %, respectively, when the concentration of NH3·H2O was 2 mol/L, the concentration of NH4Cl was 1 mol/L, the concentration of CuSO4·5H2O was 20 g/L, the solid-liquid ratio was 50 g/L, the electric current density was 30 mA/cm2 and the reaction time was 2 h. The content of Zn in the RCA decreased from 144.54 mg/g to 23.7 mg/g and Cd from 0.72 mg/g to 0.005 mg/g after slurry electrolysis, and other heavy metals in the RCA also decreased. The potential difference that occurs between the two poles under the NH3·H2O slurry electrolysis system promotes the leaching of Cu from the RCA, while the leached Cu2+ combines with NH4+ to form the Cu–NH3 complex (Cu(NH3)42+, Cu(NH3)2+), thus increasing the current efficiency and promoting the cathodic copper deposition. The high-purity Cu obtained at the cathode belongs to the face-centered cubic structure (111), (200) and (220) of the Cu crystalline surface. This study provides a new method for the resourceful recovery of copper from RCA.

Copper recovery from waste printed circuit boards by NH3−(NH4)2S2O8–CuSO4 slurry electrolysis

The recovery of waste printed circuit boards (WPCBs) is always at the center of the issue of e-waste, and even “urban mining”. Slurry electrolysis has been certified as a new and efficient approach for directly recovering copper from WPCBs, although its current efficiency is not high. Therefore, an alkaline slurry electrolysis system with NH3−(NH4)2S2O8–CuSO4 was examined to improve the current efficiency because (NH4)2S2O8 produces SO4-· or ·OH in an alkaline environment. Factors such as the current density, concentration of NH3·H2O, (NH4)2S2O8, NaCl, and Cu2+, solid/liquid (S/L) ratio, and electrolysis time are discussed. The results showed that the NH3−(NH4)2S2O8–CuSO4 electrolyte could significantly impact the current efficiency and copper recovery rate. Under optimum conditions (4 mol/L ammonium hydroxide, 1 mol/L ammonium persulfate, 20 g/L copper ion(Ⅱ), 0.5 mol/L sodium chloride, S/L ratio of 30 g/L, 20 mA/cm2, and 3 h), the copper recovery rate was 90.10%, and the copper current density was significantly improved to 83.03%, which was considerably higher than that of the acidic slurry electrolysis system (approximately 70%). Because copper in the WPCBs and Cu2+ can form [Cu(NH3)2]+ with ammonia and ammonia persulfate, it is substantially easier to electrodeposit than [Cu(NH3)4]2+. Meanwhile, the purity of the obtained copper foil was > 99.986%, meeting the standard for commercial cathodic copper, and markedly higher than that of the acidic slurry electrolysis system. Thus, alkaline slurry electrolysis shows great potential for applications in the e-waste industry.

Electrolyte circulation: Metal recovery from waste printed circuit boards of mobile phones by alkaline slurry electrolysis

Alkaline slurry electrolysis has been verified as an effective method for metal recovery from waste printed circuit boards (WPCBs). However, the electrolyte that remains after slurry electrolysis contains high concentrations of metal, which can cause pollution without suitable treatment. Most importantly, the metals in the electrolyte are not completely recovered, resulting in wasted resources and increased costs. Here, the feasibility of circulating this electrolyte and its effect on copper recovery, current efficiency, and purity, is discussed. We also describe in detail the migration and transformation of copper and other metals, such as nickel, zinc, and lead, during the preparation of high-purity cathode copper from mobile phone WPCBs (WPCB-MPs) using an ammonia-ammonium chloride slurry electrolysis system. Experimental results from 19 cycles of electrolyte reuse show that copper is mainly distributed in the cathode products, whereas other metals are mainly distributed in the electrolyte and anode residues. With an increase in the number of cycles, the concentration of other metals in the electrolyte gradually increased, showing metal enrichment. The current efficiency fluctuates but is usually >90%. In addition, the copper recovery rate and purity were essentially unaffected, being >99% and >99.9% for all 20 runs, respectively, and all the cathode copper foils were easily peeled off. This study demonstrated that electrolytes can be reused for metal recycling from WPCB-MPs by alkaline slurry electrolysis without decreasing Cu purity, Cu recovery rate, and current efficiency. Thus, this study provides a green and cost-effective process for recycling resources from e-waste.

Recovery of battery-grade products from mixed spent LiFePO4/LiMn2O4 cathodes via slurry electrolysis

A facile and efficient of two-stage slurry electrolysis process comprising of precipitation and separation steps was proposed to recover different metals from the mixed spent LFP and LMO cathodes simultaneously. Benefitting from the presence of LFP, the leaching efficiency of LMO was enhanced in the first-stage slurry electrolysis. Fe and Li in the lixivium can then be easily recovered as pure FePO4 and battery-grade Li2CO3 in the precipitation and separation steps, respectively. Finally, the battery-grade MnO2 is produced in the second-stage slurry electrolysis. The total recovery rates of Li, Mn, and Fe are as high as 89.83 %, 88.69 % and 94.42 %, respectively. In addition, the integrated process of the two-stage slurry electrolysis is simple and easy to perform on industrial scale and introduces remarkable economic and environmental benefits.

Computational fluid dynamics study on the effect of stirring parameters on solid–liquid suspension in the slurry electrolysis square tank

As a sustainable hydrometallurgical technology, slurry electrolysis (SE) offers certain advantages in the treatment of complex ores and secondary electronic waste. It is therefore of considerable interest to understand the solid–liquid suspension in the stirred tank for overall process control. Here, a computational fluid dynamics (CFD) model based on the Eulerian-Eulerian framework combined with the kinetic theory of granular flow was employed to investigate the effects of varying the impeller speed (70–150 rpm), solids volume fraction (8–21 %), and particle specific gravity (2–6.7) on solid–liquid suspension behavior in a square tank equipped with electrodes and impeller. The results show that as the impeller rotating speed increases, turbulent kinetic energy is gradually transferred from the lower part of the electrodes to the region near the impeller shaft and between the membrane bags. The solids volume fraction was found to have little effect on the final liquid flow fields, but significantly increased the power consumption. The homogeneity and power consumption were quantified as functions of specific gravity, allowing the degree of homogeneity to be predicted under different operating conditions.

Efficient Recovery of Cu from Wasted CPU Sockets by Slurry Electrolysis

In order to maximize the reuse of used electronic component resources, while reducing environmental pollution, Cu metal was recycled from wasted CPU sockets by the reformative slurry electrolysis method. However, the influences on the regulation of the Cu recovery rate and purity from waste CPU slots, by slurry electrolysis, has not been systematically elucidated in previous studies. In this work, the effects of H2SO4 concentration, slurry density, NH4Cl concentration, current density, and reaction time, on the recovery rate and purity of Cu in slurry electrolysis, were researched by systematic experimental methods. The results showed that the recycled metal elements were mainly present as powders from the cathode, rather than in the electrolyte. Moreover, the metallic elements in the cathode powder consisted of mostly Cu and small amounts of Sn and Ni. The recovery rate and purity of Cu were up to 96.19% and 93.72%, respectively, with the optimum conditions being: an H2SO4 concentration of 2 mol/L, slurry density of 30 g/L, NH4Cl concentration of 90 g/L, current density of 80 mA/cm2, and reaction time of 7 h. Compared with previous studies, the Cu recovered in this experiment was present in the cathode powder, which was more convenient for the subsequent processing. Meanwhile, the recovery rate of Cu was effectively improved. This is an important guideline for the subsequent application of slurry electrolysis for Cu recovery.

Teaching Electrometallurgical Recycling of Metals from Waste Printed Circuit Boards via Slurry Electrolysis Using Benign Chemicals

The rapid growth of personal electronics has promoted a surge of e-waste worldwide. Among the e-waste stream, waste printed circuit boards (WPCBs) contain a lot of recyclable valuable metals that can incentivize the recycling operation when recovered. This pedagogical exercise demonstrates a simple electrocatalytic metal recovery strategy that works at room temperature and atmospheric pressure. Students can complete the exercise within 1.5–2 h and get to learn about electrocatalytic reactions and their parameters. The reaction can be powered by a couple of 1.5 V AA batteries and an electrolyte chemically similar to automobile antifreeze. Using quotidian objects can help students connect their laboratory learning with their daily lives. In addition to teaching electrochemistry concepts, we hope this exercise can raise awareness of the substantial increase of e-waste in recent years.

Numerical simulation of solid-liquid suspension in a slurry electrolysis stirred tank

Slurry electrolysis (SE) is a hydrometallurgical process that has a good potential for application in the extraction of metals from polymetallic complex mines. The particle size (d), impeller diameter (D) and liquid level (H) on the effect of solid-liquid suspension characteristics were investigated numerically, which has been verified by experiments. The results showed that the homogeneity decreased significantly with the increase of particle size. When the homogeneity was ≥ 0.9, the particles reached uniform suspension. The impeller diameter had a great influence on the liquid flow at the upper end of the tank, whereas the homogeneity first increased, and then, tended to be stabilized with the increase of power. When D= T/3, the power required to meet uniform suspension was the smallest, and had the value of 6.28 kW. The higher the liquid level, the worse the homogeneity of the particles, and the lower the power consumption.

Research on Bayer Red Mud Slurry Electrolysis.

The Bayer red mud is the solid waste generated during the production of alumina by the Bayer process. At present, the stock of red mud in China exceeds 1.1billion tons, covering an area of more than 120,000 mu, and the annual production volume is increasing by 100million tons. The comprehensive utilization of red mud is still a difficult problem. Therefore, it is of great significance to actively explore new methods for removing sodium from red mud. In this study, the traditional red mud desalination process and the slurry electrolysis process are combined, and the influence of three different leaching agents on the leaching and sodium removal of red mud slurry in the presence of an electric field is explored. In the slurry electrolysis experiment, it was found that the sodium removal rate obtained by different leaching agents was CaO > CaCl2 > HCl. The red mud leached with pure dilute hydrochloric acid has the highest Na removal rate, which is 93.11%. In view of this situation, a pre-slurry-electrolysis cycle process with HCl as leaching agent was proposed. The core of slurry electrolysis is electrolyzing NaCl solution, and HCl only participates in the process as circulating medium. The design of this process reduces cost and increases efficiency.

Gold Fractal Growth during Its Recycling from Waste Printed Circuit Boards by Slurry Electrolysis

Gold Fractal Growth during Its Recycling from Waste Printed Circuit Boards by Slurry Electrolysis

Evolution of coal molecular structure during constant current electro-oxidation of coal–water slurry in alkaline media

Compared to the oxygen evolution reaction, coal–water slurry electrolysis as an anodic reaction can significantly reduce the cell voltage of the cathodic hydrogen evolution reaction or cathodic carbon dioxide reduction reaction. However, because the polarization curves of cathode and anode are different and vary with time, it is difficult to control the cell voltage and operation time so that the cathode and anode operate effectively under their respective optimum conditions at the same time. We investigated the evolution of coal during constant current electrolysis, where the reactions at the cathode and anode were simultaneously controlled by the circuit current. Constant current electrolysis was performed on coal–water slurries (CWS). The alkali-soluble matter separated from the CWS was subjected to constant current electrolysis and constant potential electrolysis. The results showed that constant current electrolysis was dominated by the oxidation of alkali-soluble matter, followed by the combination of alkali-soluble matter and residual coal, and finally the residual coal. The molar fraction of the aromatic bridgehead carbon in the residual coal increased from 0.132 to 0.214, which is close to that of the bicyclic structure of naphthalene (0.2). The aromatics in the alkali-soluble matter underwent a ring-opening reaction, the degree of condensation decreased from 0.08 to 0.03, and the aliphatic chain length increased from 1.77 to 2.38. The results provide a reference for simultaneously controlling the cathodic and anodic reactions using circuit current and time.