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Article

Copper from Waste Printed Circuit Boards Was Effectively Bioleached Using Newly Isolated Microorganisms and Subsequently Recovered by Microbial Fuel Cell

by
Xiafei Yin
1,†,
Xuan Shan
1,
Wei Shao
2,†,
Lixue Liu
1,
Guobin Liang
1,*,
Quanfa Zhou
3,* and
Wei Lin
1,4
1
Jiangsu Key Laboratory of E-Waste Recycling, School of Resources and Environmental Engineering, Jiangsu University of Technology, Changzhou 213001, China
2
Jiangsu Longhuan Environmental Technology Co., Ltd., Changzhou 213032, China
3
Changzhou Institute of Technology, Changzhou 213032, China
4
School of Chemistry and Chemical Engineering, Jiangsu University of Technology, Changzhou 213001, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Sustainability 2023, 15(13), 9996; https://doi.org/10.3390/su15139996
Submission received: 24 April 2023 / Revised: 16 June 2023 / Accepted: 19 June 2023 / Published: 24 June 2023
(This article belongs to the Section Waste and Recycling)
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Abstract

:
Two newly isolated bacterial strains were isolated from activated sludge and identified as Coniochaeta fodinicola (C. fodinicola) and Talaromyces barcinensis (T. barcinensis) by 16S rDNA. C. fodinicola and T. barcinensis were used to bioleach the copper from the waste printed circuit boards (WPCBs) powder, which was obtained by crushing and sorting the printed circuit board substrate after removing components. Results showed that the minimum and maximum Cu2+ leaching rates for C. fodinicola leaching were 3.9% and 89.2%, respectively. The minimum and maximum Cu2+ leaching rates for T. barcinensis leaching were 20.6% and 89.0%, respectively. The bioleaching solution was used as the cathode liquid of a dual chamber microbial fuel cell (MFC), and an X-ray diffraction (XRD) pattern displayed that the Cu2+ in the bioleaching solution was reduced to copper using biological electricity generation.

1. Introduction

The continuous shortening of the renewal period for electronic products has caused a significant increase in the number of eliminated electrical and electronic equipment (EEE) [1,2]. It is estimated that the total consumption of global EEE will increase by approximately 2.5 million metric tons annually [3]. Accordingly, the amount of waste EEE (WEEE) has been continuously rising. Printed circuit boards (PCBs) are an indispensable and valuable component of almost all EEE. Waste PCBs (WPCBs) contained more than 40 kinds of metals, some of which (especially copper) had a much higher content than those in ores [4]. The resource attributes of WPCBs, especially metal resources, were the original driving force for the development of WPCBs treatment technology [5]. Developed countries generally follow the “3R” (reduce, reuse, recycle) principle and follow the “resource-product-renewable resource” and the “circular economy” development model, implement an “extended producer responsibility system” and form joint producer associations or authorized civil society organizations. Developed countries also implement legislation to ensure the smooth flow of WEEE logistics and finance, so as to achieve comprehensive recycling of WEEE.
Significant progress has been made in the recycling of WPCBs [6,7,8]. Generally, the recovery of metals from WPCBs can be divided into four major stages. Firstly, the mechanical cutting method, the thermal melting method and the chemical agents dissolution method is used to separate the electronic components from the base boards and sort out the valuable components [9]. Secondly, the obtained base boards are crushed and sorted (such as airflow separation, magnetic separation, pulse dust collection, and electrostatic separation) [4] to screen out pure metal powder and WPCBs powder, where a small amount of metal still exists in the WPCBs powder. Thirdly, the metal is transferred from a solid (WPCBs powder) to a solution using the leaching method. Finally, the leaching solution is further treated to recover and purify the metals through methods such as precipitation, ion exchange and electrochemistry [10].
The leaching of metals is an inevitable step. Traditional lixiviants include mineral acids and cyanide-based chemicals, which have high leaching efficiency in WPCBs powder [11,12]. However, it has the problem of high cost and serious secondary pollution. The bioleaching process, successfully used in the treatment of WPCBs powder, has been experimented by many researchers [13,14]. Li et al. evaluated the ability of Pseudomonas fluorescens to leach gold from WPCBs and results revealed that after 64 h of reaction, the leaching rate of gold could reach 42% [15]. Yuan et al.’s research also demonstrated that Pseudomonas fluorescens could effectively leach silver from WPCBs, and the Ag+ concentration in the leaching solution was 1 mg/L [16]. Currently, the most widely used microorganisms are still Acidithiobacillus ferrooxidans (A. ferrooxidans) and Acidithiobacillus thiooxidans (A. thiooxidans). Arshadi et al. used A. ferrooxidans to leach Cu and Ni from computer PCBs and nearly 100% of Cu and Ni were simultaneously recovered during the 80 days of reaction [17]. Nevertheless, the bioleaching process had the problem of long leaching time and low leaching efficiency, which limited the commercial application of bioleaching. In terms of economic feasibility, the bioleaching rate becomes increasingly important. Screening for targeted leaching of metals (such as copper) from WPCBs powders by special microorganisms is one of the key factors in improving the leaching rate.
To recover copper from a bioleaching solution, traditional technologies, especially electrochemical methods, have been widely used. However, the high cost limits their large-scale application. A microbial fuel cell (MFC) can release electrons through anodic oxidation of organic matter (electron donor) in sewage. The electrons reach the cathode through wires and then combine with an electron acceptor (i.e., oxidizing substances, such as O2, Cu2+, etc.) to produce a reduction reaction, thus generating electricity [18,19,20]. It has been proven that wastewater containing Cu2+ was used as the cathode solution (electron acceptor) of MFC, and that the biological power generation was 0.4–0.6 V. The Cu2+ was reduced to elemental copper and Cu2O [21,22]. This indicated that the bioelectricity generated by the MFC could replace the traditional power supply in the electrolytic technology and realize the electroreduction of Cu2+ at the cathode of the MFC, so as to effectively recover copper.
Consequently, the objective of this study was to screen out special microorganisms that efficiently leach copper from WPCBs powder and use an MFC to recover copper from a bioleaching solution. This method will provide an environmentally friendly and economically feasible treatment approach for the recycling of metals from WPCBs powder.

2. Materials and Methods

2.1. Experimental Materials

The main reagents used in the experiment, such as 9K medium, glucose, peptone, anhydrous sodium acetate, beef extract, NaHCO3, KH2PO4, NH4HCO3, MgCl2·6H2O, CaCl2 and FeCl3·6H2O were purchased from Sinopharm Chemical Reagent Co., Ltd., Shanghai, China.
WPCBs powder (a mesh size of 100–200 μm, copper mass fraction of 5%), obtained by crushing and sorting the printed circuit board substrate after removing electronic components, was collected from a disused electrical appliance dismantling company in Changzhou.
The activated sludge (the total suspended sludge of 3.0 g/L) was obtained from a municipal sewage treatment plant in Changzhou.

2.2. Microbial Screening and Bioleaching of WPCBs Powder

Microbial screening, isolation and purification were described in our previous study [23]. Similarly, 110 mL of activated sludge, 1 g of waste circuit board powder, and 90 mL of liquid 9K medium were evenly mixed and incubated at 30 °C at 140 r/min in an oscillatory incubator (ZHLY-300S, Shanghai Zhichu Instrument Co, LTD, Shanghai, China) for 5 days. Then, 10% of the inoculum was inoculated into fresh 9K medium and the culture was continued. After the above process was repeated 4 times, the inoculum was inoculated on 9K solid medium at 30 °C in a constant temperature incubator (DHP, Shanghai a constant scientific instrument Co., Ltd., Shanghai, China) until colonies grew. Single colonies were selected and isolated on fresh medium until pure colonies were obtained.
The purified strain was inoculated into acid liquid 9K medium and cultured until the OD600 value reached the end of the logarithmic growth period. WPCBs powder was added to the purified bacterial solution at doses of 1%, 2%, 3%, 4%, 5% (w/v), respectively, and stirred at a speed of 100 r/min.

2.3. MFC Construction, Inoculation and Operation

The dual chamber MFC was made of plexiglass. It was equally separated by a proton exchange membrane (PEM, Nafion-117, DuPont Co., Monroe, NC, USA) into two tanks, the anode and cathode chambers (total volume of 1.0 L for each, working volume of 0.8 L for each). Two titanium plates (5 cm × 5 cm × 0.5 cm for each, Shanghai Yunzhe Metal Products Co., LTD, Shanghai, China), inserted in the anode and cathode chambers, respectively, were functioned as the electrodes. A titanium wire connected the resistance (75 Ω) to the electrodes.
An amount of 300 mL activated sludge and 500 mL simulated wastewater were added into the anode chamber. The simulated wastewater contained 230 mg/L glucose, 60 mg/L peptone, 40 mg/L anhydrous sodium acetate, 20 mg/L beef extract, 198 mg/L NaHCO3, 12 mg/L KH2PO4, 170 mg/L NH4HCO3, 2.4 mg/L MgCl2·6H2O, 1.2 mg/L CaCl2 and 1 mg/L FeCl3·6H2O [24]. In the cathode chamber, 800 mL of bioleaching solution was added. When the voltage between the anode and cathode dropped below 50 mV, 80% of anode chamber mixture and total bioleaching solution were manually removed, and fresh simulated wastewater and fresh bioleaching solution were added, respectively. A new cycle started. This procedure was repeated until the peak voltages of the MFC reached a stable performance for 4 consecutive cycles, indicating that MFC was started successfully. Once the stable operation cycle finished, the steps above were followed to replace the fresh simulated wastewater and bioleaching solution, and then, the data were recorded.

2.4. Analytical Methods

The purified strain was sent to Shanghai Shenggong Bioengineering Co., Ltd., Shanghai, China, for 16S rDNA sequencing to determine the gene sequence and microbial community structure [23]. The phylogenetic tree was established by Neighbor-Joining method of Molecular Evolutionary Genetics Analysis software (MEGA) V7.0.26 to determine the species and genera of microorganisms. A microplate reader (Infinite 200PRO, Beijing Longyue Biotechnology Development Co., Ltd., Beijing, China) was used to measure OD600 value, which indicated the growth of microorganisms. The Cu2+ concentration of the leaching solution was measured by an inductively coupled plasma-optical emission spectrometer (ICP-OES, Optima 2100 DV, Perkin Elmer, Waltham, MA, USA) [25]. Scanning electron microscopy (SEM, SU1510, Hitachi, Tokyo, Japan) was used to observe the surface morphology of the WPCBs [26]. Metabolomics was used to analyze the metabolites in the bioleaching process [23]. The voltage (U, mV) was recorded using a data acquisition system (34972A, Agilent Technologies Inc., Santa Clara, CA, USA). An electrochemical workstation (CHI600D, Shanghai Chenhua Instrument Co., Ltd., Shanghai, China) was used to test cyclic voltammetry (CV) curves [19]. X-ray diffraction (XRD, X’PERT POWDER, Panaco, Amsterdam, The Netherlands) was used to determine the material deposited on the cathode material.

3. Results

3.1. Identification of Newly Isolated Microorganisms

After repeated isolation and purification, two strains, named Y1 and Y2, were finally obtained. The sequence of the two strains of bacteria were uploaded on the NCBI website and compared using the basic local alignment search tool (BLAST), following which a phylogenetic tree (Figure 1) was established.
It could be found that strain Y1 and Coniochaeta fodinicola (C. fodinicola) were on the same branch with a similarity of 97%. Therefore, Y1 could be considered as C. fodinicola. As shown in Figure 1B, strain Y1 and Talaromyces barcinensis (T. barcinensis) were on the same branch with a similarity of 100%. Thus, Y1 could be considered as T. barcinensis. C. fodinicola and T. barcinensis were deposited into the China General Microbiological Culture Collection Center with the deposit number of CGMCC No. 21958 and No. 22430.

3.2. Bioleaching of WPCBs Powder

C. fodinicola and T. barcinensis were inoculated in 9K medium and cultured until the OD600 value reached the end of the logarithmic growth period. Then, the WPCBs powder, at an inoculation amount of 1–5% (w/v), was added to the C. fodinicola and T. barcinensis bacterial solution, respectively. The leaching rate of copper in WPCBs powder is shown in Table 1 and Table 2.
Table 1 exhibits that as the WPCBs powder was added to the C. fodinicola bacterial solution and was shook for 5 d, as the reaction time increased, the Cu2+ leaching rate also continued to increase. When the dosage of the WPCBs powder increased from 1% (w/v) to 4% (w/v), the Cu2+ leaching rate increased from 26.7% to 89.2%, after 5 days of reaction. However, with the further increase in the dosage to 5% (w/v), the Cu2+ leaching rate was 88.3% after 5 days of reaction, which was slightly lower than the leaching rate after 4 d of reaction.
As shown in Table 2, the WPCBs powder was shook in the T. barcinensis bacterial solution for 1–5 d, and with the increase in WPCBs powder dosage, the Cu2+ leaching rate continuously increased. Furthermore, it was observed that within the same WPCBs dosage, as the reaction progressed from day 1 to day 4, the Cu2+ leaching rate continued to increase. When the WPCBs powder dosage was 5% (w/v), the Cu2+ leaching rate reached a maximum of 89.0% on the 4th day. Unfortunately, on the 5th day, when the WPCBs powder dosage was 5% (w/v), the Cu2+ leaching rate significantly decreased to 60.2%.
Table 1 and Table 2 also show that in 5 days, the maximum Cu2+ leaching rates for C. fodinicola and T. barcinensis were 89.2% and 89.0%, respectively, which were higher than those of some existing reports. It was 85.88% (in 30 d) by using Aspergillus niger [27], 76% (in 21 d) by using Penicillium chrysogenum [28] and 81.43% (in 7 d) by using A. ferrooxidans [29].
After 5 days of leaching, SEM was used to observe the surface morphology of the residual WPCBs (Figure 2) and metabolomics was used to analyze the metabolites in the bioleaching process (Figure 3).
Figure 2A shows that the original surface of WPCBs was smooth. Figure 2B,C were the SEM images of WPCBs extracted by C. fodinicola and T. barcinensis bacterial solution at a dosage of 5%, respectively. Obviously, after 5 days of bioleaching, microorganisms adsorbed and aggregated on the surface of WPCBs.
After 5 days of leaching, the heatmap of the content of metabolites during the leaching process of WPCBs by C. fodinicola and T. barcinensis is shown in Figure 3. Blue indicates that the contents of metabolites were below the average level, while red indicates that the contents of metabolites were higher than the average level.
During the process of C. fodinicola leaching WPCBs, the content of metabolites such as phthalic acid, rosmarinic acid, L-Glutamic acid, glyceric acid, pyruvic acid, fumaric acid, ethylmethylacetic acid, 2-Oxo-4-methylthiobutanoic acid, tartaric acid, 4-Hydroxyphenylpyruvic acid and L-Aspartic acid were relatively high. During the process of T. barcinensis leaching WPCBs, the content of metabolites such as methylimidazoleacetic acid, homovanillic acid, pelargonic acid, suberic acid and 3-(2-Hydroxyphenyl)propanoic acid were relatively high. It indicates that both C. fodinicola and T. barcinensis secreted organic acids during the bioleaching process.

3.3. Recovery of Copper from Bioleaching Solution of WPCBs Powder

Four dual chamber MFCs were constructed. The cathode liquid was the bioleaching solution with the lowest Cu2+ concentration extracted by C. fodinicola for MFC1, the bioleaching solution with the highest Cu2+ concentration extracted by C. fodinicola for MFC2, the bioleaching solution with the lowest Cu2+ concentration extracted by T. barcinensis for MFC3 and the bioleaching solution with the highest Cu2+ concentration extracted by T. barcinensis for MFC4, respectively.
As shown in Figure 4, for the solution leached by C. fodinicola, the MFC with a lower Cu2+ concentration produced a higher output voltage. The output voltage trend of T. barcinensis is consistent with that of C. fodinicola. The maximum output voltage was 467 mV for MFC1, 284 mV for MFC2, 283 mV for MFC3 and 225 mV for MFC4, respectively. After 424 h of operation, the output voltages were decreased to 38 mV, 26 mV, 24 mV and 32 mV, respectively.
The CV curve could be used to analyze the redox reaction and the electron transfer process on the electrode surface of the electrochemical system. As shown in Figure 5, a pair of obvious redox peaks appear on the CV curves of the cathodes, respectively, indicating that electrons successfully transferred to the electrode surface and all cathodes had electrochemical activity. The oxidation peak potential and current were –0.665 mV and 0.043 mA for MFC1, 0.445 mV and 0.042 mA for MFC2, –0.945 mV and 0.043 mA for MFC3, and 0.295 mV and 0.043 mA for MFC4, respectively.
After one cycle of operation, brick red deposits were observed on the cathode surfaces of all four MFCs. The XRD spectrum of deposits are shown in Figure 6.
XRD patterns showed that the characteristic peaks of elemental copper retrieved from PDF0178-2076 by a computer were consistent, confirming that Cu2+ was reduced to copper due to the generation of biological electricity via exoelectrogens in the anode chamber [30]. One of the key factors in generating electricity by the MFC is the microorganisms in the anode chamber, especially exoelectrogens. Therefore, 6S rDNA high-throughput sequencing was used to analyze the microbial community in the anode chamber (Figure 7).
It could be observed that the anode chambers of all four reactors contained microorganisms such as Proteobacteria (48.35% in MFC1, 39.25% in MFC2, 38.88% in MFC3, 34.04% in MFC4), Firmicutes (1.93% in MFC1, 2.12% in MFC2, 1.82% in MFC3, 2.37% in MFC4), Chloroflexi (8.63% in MFC1, 15.57% in MFC2, 12.06% in MFC3, 17.53% in MFC4), Acidobacterium (8.56% in MFC1, 8% in MFC2, 9.24% in MFC3, 8.09% in MFC4), Actinobacteria (1.16% in MFC1, 1.38% in MFC2, 1.83% in MFC3, 1.48% in MFC4), Gemmatimonadetes (1.54% in MFC1, 1.67% in MFC2, 1.41% in MFC3, 1.32% in MFC4), etc., which were common phyla of exoelectrogens [31]. This proved that the exoelectrogens in the anode chamber produced electricity, and the electrons transferred to the cathode to reduce Cu2+ into elemental copper, which deposited onto the surface of the cathode.

4. Discussion

4.1. Bioleaching of WPCBs Powder

The newly isolated microorganisms C. fodinicola and T. barcinensis could effectively leach copper from WPCBs. This might be mainly due to the following reasons. Firstly, the 9K culture medium is acidic and contains a large amount of H+, which can effectively attack WPCBs. Secondly, Fe2+ in 9K culture medium can be oxidized to Fe3+ by floating C. fodinicola and T. barcinensis with O2 in existence. Fe3+, with strong oxidizing properties, plays an important role in copper leaching. Thirdly, microorganisms aggregate on the surface of WPCBs and secrete organic acids that erode WPCBs and release metals [23].
Based on the performance of C. fodinicola leaching copper from WPCBs, it could be seen that within the same reaction time, the Cu2+ leaching rate increased continuously as the amount of the WPCBs dose increased from 1% to 4%, which implied that the bacterium accelerated the copper leaching process [32]. However, with the further increase in the dosage to 5% (w/v), the Cu2+ leaching rate slightly decreased. Interestingly, the average Cu2+ leaching rate for the 4% (w/v) dosage and the 5% (w/v) dosage was the same (16.86%/d). Marhual et al. [33] pointed out that a higher metal concentrates dosage would cause a lower copper leaching rate mainly due to the limitation in air distribution and oxygen mass transfer. Therefore, in the early stage of the reaction, a higher WPCBs powder dosage reduced the Cu2+ leaching rate.
Based on the performance of T. barcinensis leaching copper from WPCBs, it could be seen that within the same reaction time, the Cu2+ leaching rate increased with increasing dosage of WPCBs. It was believed that the concentration of metal ions also increased with the increase in the amount of metal concentrates [34]. Moreover, within the same WPCBs dosage, the Cu2+ leaching rate increased as the reaction time increased from 1 to 4 days, but decreased as the reaction time increased to the 5th day. Two reasons were speculated to cause this. On the one hand, the polysaccharides and proteins contained a generous amount of negatively charged functional groups distributed on the surfaces of microbial cells, which were beneficial for capturing metal ions, thereby being assimilated and adsorbed by microbial cells for bacterial metabolism [35,36], resulting in lower leaching rates. On the other hand, during the biodegradation process of the WPCBs powder, secondary precipitation occurred, which fixed the released elements and affected the Cu2+ leaching effect [15].

4.2. Recovery of Copper from Bioleaching Solution of WPCBs Powder

The MFC is a device that uses the metabolic action of microorganisms to convert chemical energy into electrical energy. In the anode chamber, activated sludge (containing exoelectrogens) degrades simulated wastewater to produce electrons and protons. Electrons reach the cathode via an external circuit, thus generating an external voltage. Protons cross the PEM membrane to the cathode, where they combine with the electrons transferred from the anode and the Cu2+ in the cathode chamber to carry out a reduction reaction, reducing the Cu2+ to copper [19,20].
Figure 2 reveals that for the solutions leached by C. fodinicola and T. barcinensis, the MFC with the lower Cu2+ concentration produced a higher output voltage. In the studies of Wu et al. [21] and Tao et al. [30], as the Cu2+ concentration increased, the output voltage continuously decreased. These results indicated that the inhibition of the higher Cu2+ concentration to the activity of microorganisms induced a decrease in voltage in the MFC [21,37]. Some studies suggest that the performance of the MFCs was controlled by the reduction of Cu2+ at the biocathode, rather than the microbial metabolism occurring at the anode [38]. In addition, the lower the internal resistance of the charge transfer on the electrode surface, the higher the electron transfer efficiency, which resulted in a higher output voltage [39].
Different microorganisms had different catalytic activities for Cu2+ [38]. Therefore, there is no significant comparability between the output voltage and the CV curve of MFC using the T. barcinensis bioleaching solution and those of the MFC using the C. fodinicola bioleaching solution. Figure 3 also displays that for the same bioleaching solution, as the Cu2+ concentration increased, the position of the oxidation peak shifted negatively. Mirzaie et al. has observed that the lower the oxidation potential, the higher the electrocatalytic performance of the electrode [40]. These results, in combination, demonstrated that a lower Cu2+ concentration was beneficial for improving the electron transfer rate and electrocatalytic activity, thereby increasing the output voltage.
This study screened special microorganisms and used the bioleaching method to efficiently extract copper from WPCBs. Compared with studies using other microorganisms to leach copper, the Cu2+ leaching rates of C. fodinicola and T. barcinensis were higher. This process did not require the consumption of hazardous chemicals such as sulfuric acid, and the operation process was relatively safe. The leached Cu2+ was used as the electron acceptor in the cathode chamber of the MFC, and the current generated by the MFC replaced the conventional power supply in the electrolytic method and achieved the electrical reduction of Cu2+ in the MFC cathode chamber. This process effectively recovered copper from WPCBs. As known, the copper content of the WPCBs far exceeds the metal grade of ordinary copper ores. Compared to extracting metals from metal ores, recycling metals from WPCBs not only contributed to reusing waste resources, but also protected the depleting metal mineral resources, which greatly reflected the concept of energy saving and emission reduction and advanced the process of sustainable development. This technology provided a theoretical basis for the green extraction and recycling of metals from WEEE.

5. Conclusions

In this study, two newly isolated microorganisms, identified as C. fodinicola and T. barcinensis, were screened from sludge. Both microorganisms could effectively leach copper, with a maximum leaching rate of approximately 89%. The bioleaching solution containing Cu2+ was used as the cathode solution of the dual chamber MFC to reduce Cu2+ to copper via bioelectricity. The process did not require the consumption of hazardous chemicals such as sulfuric acid, and the leaching process did not produce any secondary pollution, which effectively reduces environmental pollution. In addition, the current generated by the MFC replaces the conventional power supply in the electrolytic process for the reduction of Cu2+, which effectively reduces treatment costs. The successful implementation of this project will achieve efficient and clean production of metal recovery from a WPCBs powder through a biological treatment, which is of great significance for the treatment and disposal of WEEE.

Author Contributions

Conceptualization, Q.Z.; investigation, X.S. and W.L.; project administration, X.Y.; software, X.Y., X.S. and W.S.; writing—original draft, X.Y., X.S. and L.L.; writing—review and editing, X.Y. and G.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by The Natural Science Foundation of the Jiangsu Higher Education Institutions of China, grant number 21KJB610010, The Natural Science Foundation of the Jiangsu Higher Education Institutions of China, grant number 20KJA610005, Changzhou Longcheng Talent Program, grant number CQ20210092 and Changzhou Science and Technology Bureau, grant number CM20223017. The APC was funded by The Natural Science Foundation of the Jiangsu Higher Education Institutions of China, grant number 20KJA610005.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data is contained within the article.

Acknowledgments

This work was supported by a grant from The Natural Science Foundation of the Jiangsu Higher Education Institutions of China (21KJB610010 and 20KJA610005), Changzhou Longcheng Talent Program (CQ20210092) and Changzhou Science and Technology Bureau (CM20223017).

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The phylogenetic tree. (A) Strain Y1. (B) Strain Y2.
Figure 1. The phylogenetic tree. (A) Strain Y1. (B) Strain Y2.
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Figure 2. SEM images of WPCBs. (A) Original WPCBs. (B) An amount of 5% (w/v) of WPCBs dosage was added to the C. fodinicola bacterial solution. (C) An amount of 5% (w/v) of WPCBs dosage was added to the T. barcinensis bacterial solution.
Figure 2. SEM images of WPCBs. (A) Original WPCBs. (B) An amount of 5% (w/v) of WPCBs dosage was added to the C. fodinicola bacterial solution. (C) An amount of 5% (w/v) of WPCBs dosage was added to the T. barcinensis bacterial solution.
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Figure 3. The heatmap of differential metabolites. (A) An amount of 5% (w/v) of WPCBs dosage was added to the C. fodinicola bacterial solution ((C1): before bioleaching reaction, (C2): after bioleaching reaction). (B) An amount of 5% (w/v) of WPCBs dosage was added to the T. barcinensis bacterial solution ((T1): before bioleaching reaction, (T2): after bioleaching reaction).
Figure 3. The heatmap of differential metabolites. (A) An amount of 5% (w/v) of WPCBs dosage was added to the C. fodinicola bacterial solution ((C1): before bioleaching reaction, (C2): after bioleaching reaction). (B) An amount of 5% (w/v) of WPCBs dosage was added to the T. barcinensis bacterial solution ((T1): before bioleaching reaction, (T2): after bioleaching reaction).
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Figure 4. The voltages of MFCs.
Figure 4. The voltages of MFCs.
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Figure 5. The cyclic voltammetry curves of cathodes. (A) MFC1. (B) MFC2. (C) MFC3. (D) MFC4.
Figure 5. The cyclic voltammetry curves of cathodes. (A) MFC1. (B) MFC2. (C) MFC3. (D) MFC4.
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Figure 6. XRD patterns of WPCBs residues. (A) MFC1. (B) MFC2. (C) MFC3. (D) MFC4.
Figure 6. XRD patterns of WPCBs residues. (A) MFC1. (B) MFC2. (C) MFC3. (D) MFC4.
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Figure 7. Phylum-level abundance of microorganisms in anode chamber. (A) MFC1. (B) MFC2. (C) MFC3. (D) MFC4.
Figure 7. Phylum-level abundance of microorganisms in anode chamber. (A) MFC1. (B) MFC2. (C) MFC3. (D) MFC4.
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Table
Table 1. Copper leaching rate by C. fodinicola.
Table 1. Copper leaching rate by C. fodinicola.
MicroorganismsLeaching Time (d)Copper Leaching Rate (%)
1% (w/v)2% (w/v)3% (w/v)4% (w/v)5% (w/v)
C. fodinicola13.9 ± 0.24.1 ± 0.24.3 ± 0.44.9 ± 0.34.0 ± 0.1
24.1 ± 0.35.0 ± 0.25.1 ± 0.35.6 ± 0.24.7 ± 0.3
38.8 ± 0.321.28 ± 0.135.3 ± 0.186.4 ± 0.275.5 ± 0.3
420.0 ± 0.127.28 ± 0.264.5 ± 0.288.8 ± 0.181.9 ± 0.3
526.7 ± 0.436.9 ± 0.267.6 ± 0.289.2 ± 0.388.3 ± 0.3
Table
Table 2. Copper leaching rate by T. barcinensis.
Table 2. Copper leaching rate by T. barcinensis.
MicroorganismsLeaching Time (d)Copper Leaching Rate (%)
1% (w/v)2% (w/v)3% (w/v)4% (w/v)5% (w/v)
T. barcinensis120.6 ± 0.132.32 ± 0.334.0 ± 0.244.0 ± 0.345.0 ± 0.3
232.0 ± 0.240.0 ± 0.445.1 ± 0.347.0 ± 0.250.2 ± 0.3
336.8 ± 0.348.0 ± 0.155.0 ± 0.460.0 ± 0.378.0 ± 0.1
444.2 ± 0.255.0 ± 0.260.0 ± 0.367.0 ± 0.189.0 ± 0.3
524.1 ± 0.344.64 ± 0.345.2 ± 0.154.0 ± 0.260.2 ± 0.4
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Yin, X.; Shan, X.; Shao, W.; Liu, L.; Liang, G.; Zhou, Q.; Lin, W. Copper from Waste Printed Circuit Boards Was Effectively Bioleached Using Newly Isolated Microorganisms and Subsequently Recovered by Microbial Fuel Cell. Sustainability 2023, 15, 9996. https://doi.org/10.3390/su15139996

AMA Style

Yin X, Shan X, Shao W, Liu L, Liang G, Zhou Q, Lin W. Copper from Waste Printed Circuit Boards Was Effectively Bioleached Using Newly Isolated Microorganisms and Subsequently Recovered by Microbial Fuel Cell. Sustainability. 2023; 15(13):9996. https://doi.org/10.3390/su15139996

Chicago/Turabian Style

Yin, Xiafei, Xuan Shan, Wei Shao, Lixue Liu, Guobin Liang, Quanfa Zhou, and Wei Lin. 2023. "Copper from Waste Printed Circuit Boards Was Effectively Bioleached Using Newly Isolated Microorganisms and Subsequently Recovered by Microbial Fuel Cell" Sustainability 15, no. 13: 9996. https://doi.org/10.3390/su15139996

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