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Article

Upcycling of Cupric Chloride Waste Solution from PCB Manufacturing for Antibacterial Copper Nanoparticles

by
Tapany Patcharawit
1,*,
Chatisa Kansomket
1,
Napat Mahiwan
1,
Sumita Chailoi
1,
Thanapon Chandakhiaw
1,
Tanongsak Yingnakorn
1,
Teerawut Tunnukij
2 and
Sakhob Khumkoa
1
1
School of Metallurgical Engineering, Suranaree University of Technology, Muang, Nakhon Ratchasima 30000, Thailand
2
Department of Primary Industries and Mines, Ministry of Industry, 75/10 Rama VI Rd., Bangkok 10400, Thailand
*
Author to whom correspondence should be addressed.
Recycling 2025, 10(3), 97; https://doi.org/10.3390/recycling10030097
Submission received: 24 March 2025 / Revised: 19 April 2025 / Accepted: 7 May 2025 / Published: 14 May 2025
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Abstract

:
Issues encompassing hazardous waste management face challenges, particularly those involving the manufacture of electronic devices such as PCBs that are in high demand with continual growth. Therefore, upcycling to create new products viable for highly valued markets emphasizes alternative solutions towards the circular economy. This research highlights the advantages of copper sulfate recovery from the cupric chloride etching waste solution from PCB manufacturing, combined with the synthesis of copper nanoparticles for antibacterial application. First, aluminium cementation, sulfuric acid leaching, and crystallization were incorporated in the recovery step to ensure a high purity of 99.95% and a recovery of 94.76%. Aluminium cementation selectively offered copper-containing precipitates suitable for leaching to gain high-purity recovered products. In the second step, copper nanoparticles were synthesized using 0.01–0.20 M copper sulfate precursors via sonochemical reduction. In total, 1–5 mL of hydrazine and 5–30 mL of 0.01 M ethylene glycol were added into a 50 mL precursor as reducing and capping agents, respectively. Hydrazine addition under high pH played a key role in controlling the shape, size, and purity of the copper nanoparticles, required for their antibacterial properties. The optimum condition gave spherical or polygonal copper nanoparticles of 54.54 nm at 99.95% purity and >92% recovery. The antibacterial test of the synthesized copper nanoparticles using E. coli via agar well diffusion exhibited a zone of inhibition (ZOI) of 50 mm at 127 mg/mL, similar to the antibiotic-controlled condition, proving their antibacterial potential. Along with process effectiveness, a feasibility study of the inventing process confirmed the environmental and economic impacts of minimizing energy consumption and processing time, which are competitive with respect to the existing recycling technologies.

Graphical Abstract

1. Introduction

Global awareness of zero waste management towards the development of a circular economy has driven policies to administrate household and industrial waste generated domestically and imported. Eco-industrial towns support environmental sustainability from physical, economic, social, environmental, and management perspectives, where the industrial waste generated from one factory is used as the starting material for manufacturing other products to reduce the waste disposal, logistics, and environmental issues affecting operators. By evolving into a circular economy, waste is circulated and recaptured as a resource for possible new markets or used in various ways. According to the Printed Circuit Board Global Market Report 2025 [1], a compound annual growth rate (CAGR) of 5.9% (USD 68.75 billion in 2025 to USD 86.5 billion by the end of 2029) suggests the necessary degree of waste management. In the etching of print circuit boards (PCBs), cupric chloride (CuCl2) is common due to the high etching rate (25–50 micron/min), precision etching, and minimum undercutting. It is also environmentally acceptable and capable of regeneration [2]. The fresh green etching solution containing 125–175 g Cu/L, with its pH < 1, is generally prepared by dissolving copper chloride crystals in water with hydrochloric acid addition, producing a reaction during etching as expressed in Equations (1) and (2).
CuCl2 + Cu → 2CuCl
CuCl2 + 2HCl + Cu → 2CuCl + 2HCl
After repeated etching cycles, a dark green solution can be regenerated using chlorine, sodium chlorate, hydrogen peroxide, oxygen regeneration, or via electrolysis or electrodialysis, as well as via electrowinning, cementation, precipitation, solvent extraction, and membrane technology [2,3]. If regeneration is ineffective, proper disposal is required. Direct landfill causes serious environmental issues with respect to water resources even when diluted. This hazardous waste is monitored by the Industrial Waste Management Division of the Department of Industrial Works, Ministry of Industry, Thailand, and subjected to the Basel Convention on the control of the transboundary movements of hazardous wastes and their disposal, concerning A1130 for metal and metal-bearing wastes in Annex VIII [4]. The transboundary movement of waste copper etching solution must be reported to the Custom Pollution Control Department and the Foreign Trade Office. The waste is bound for R4 operations such as the recycling/reclamation of metals and metal compounds in Annex IV disposal operations (section B) [4]. Waste treatment via neutralization into sludges followed by incineration provides alternatives but still causes emissions. Promising waste management currently focuses on feasible upcycling to produce highly valued products with potential market uses. Copper nanoparticles are competitive with silver nanoparticles in terms of their antibacterial application when deployed to destroy bacterial cell walls. Regarding its application, most research concerns copper nanoparticles synthesized from analytical-grade copper precursors. Our research focused on the upcycling of copper etching waste solutions generated from PCB manufacturing to produce value-added copper nanoparticles, which have potential antibacterial applications in biomedical areas [5]. The key steps involve recovery and purification to ensure high-purity copper sulfate to be used in the subsequent step of copper nanoparticle synthesis. Feasibility was studied to address economic significance. The importance is twofold, involving (i) reducing hazardous waste and the disposal cost and (ii) creating a value-added product which has potential applications in healthcare to fulfill the research goal of producing green materials from waste.
Cupric chloride etching solutions are generally recovered as copper carbonate (CuCO3), copper sulfate (CuSO4), cupric (CuO) and cuprous (Cu2O) oxides, or cupric chloride concentrates to recover metal copper. Commercially, Old Bridge Chemicals currently uses copper wire as a raw material to produce certified copper sulfate pentahydrate (CuSO4·5H2O) for use in the certified organic production of food processing. Formerly, the company’s copper sulfate pentahydrate, used as a fungicide in the agricultural industry, was reported to be recovered from secondary resources in PCBs and brass semi manufacturing [6]. The process included physical separation, then leaching combined with four solvent extraction circuits, followed by surface-cooled crystallization. The ammoniacal etchant called “Ammo” (119.8–134.8 g/L or 10 wt.% Cu) and acidic copper etchant mixture of CuCl and CuCl2 (134.8–149.8 g/L or 12 wt.% Cu) were recovered as copper loaded in the organic solvent after solvent extraction. Ammo, a mixture of cuprous and cupric ammonium chloride, was added in the first cycle of extraction. Following scrubbing with weak acid and completed with heated acidified crystallizer mother liquor (~40 g/L Cu and 180–200 g/L H2SO4), the copper sulfate strip solution (~80–85 g/L Cu and 150–160 g/L H2SO4) was subject to surface-cooled crystallization to give copper sulfate pentahydrate. G. Zhao et al. [7] patented a recovery of at least 90% of precipitated copper sulfate pentahydrate and/or monohydrate from cupric etchant having at least 10 wt.% chloride and 5 wt.% of dissolved copper. This was via sulfuric acid leaching, followed by distillation at 95–135 °C, condensation, and separation by centrifugation. Y.P. Hung et al. [8] reported effective cementation of copper onto aluminium from strong chloride-based solutions, giving 94.5% purity at 99% recovery. Our research employed the recovery process through cementation, leaching, and crystallization, to ensure that a high purity of copper sulfate hydrate (CuSO4·xH2O) of >99% could be achieved.
For copper nanoparticle synthesis, chemical reduction is practical, e.g., polyol, sol-gel, microemulsion, and precipitation, electrochemical synthesis, and photochemical techniques, along with assisted techniques such as sonochemical (ultrasonic plus chemical reduction), and microwave-assisted [9,10,11]. The microwaves induce electromagnetic waves to give intense friction and collisions of the molecules, aiding the chemical reduction of copper precursors and the nucleation of copper nanoparticles. Copper nanoparticles of ~10 nm were obtained using sodium hypophosphite hydrate and ethylene glycol as the reducing and capping agents, respectively [10]. However, boiling was reported after 2 min. Electrochemical synthesis and thermal decomposition also gave advantages [12,13,14,15]. The thermal decomposition [15] involved solution-phase reduction of the metal precursor with capping ligands and reducing agent additions. When thermally activated, small-sized particles coalesce to form larger-sized particles by capping molecule desorption, nanocrystal seed coalescence, and larger-sized particles’ re-encapsulation. Therefore, temperature is a crucial parameter and sensitive to oxidation. J. Moghimi-Rad et al. [11] investigated the sonochemical synthesis of copper nanoparticles using copper sulfate solution as the precursor, at pH = 4 and 60 °C. The copper particle size obtained was 112.8 nm. Ultrasonic-assisted chemical reduction provides effective nucleation of nanoparticles via creation, growth, and collapse of minute bubbles [16]; thereby, rendering high localized pressure and temperature without external heat source supplied to facilitate the control of particle size, shape, and purity.
Reducing agents such as citric, ascorbic acid, sodium borohydride, hydrazine, sodium hypophosphite, glucose, and plant extracts are used [17]. Strong reducing agents potentially provide a short reduction time. Capping agents such as ethylene glycol (EG), polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) are utilized to control particle growth. This helps to control nanoparticles’ sizes and shapes to be globular, polygonal, triangular, flake, petal-like, rod, or hexagonal. The differences in the crystal morphologies of nanocrystals depend on preferential sites for capping agents to be absorbed on the nanocrystal planes, which affect the growth rates of various crystal facets [18].
Precursors such as cupric chloride (CuCl2), copper sulfate (CuSO4), and copper nitrate (Cu(NO3)2) fresh solutions are normally utilized [16]. Chemical reduction of the copper ions into copper metals is practical and fast. Although copper nanoparticles synthesized from cupric chloride via chemical reduction have been investigated by many researchers [11,16,19,20,21,22,23], most studies have focused on fresh cupric chloride solution prepared by using >99% purity commercial-grade materials, which are not in waste form. Research by P. Cerchier et al. [24] highlighted the green synthesis of copper nanoparticles under ultrasound using pure copper recovered from electronic scraps. The result provided dispersed copper nanoparticles of about 5 nm. However, the percentage recovery and purity were not reported.
As previous studies [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24] have focused on either the recovery of copper compounds from the etching solution or the synthesis of copper nanoparticles from fresh solutions, the completed details of copper nanoparticle synthesis from waste have not been fully addressed from the environmental and economic aspects. In addition, a study of a copper recycling flow model [25] showed that copper recycling requires 15% less energy consumption than copper production. Research by R. Panda et al. [26] recovered copper oxide nanoparticles of approximately 100 nm in size with 98% purity from end-of-life PCBs via ammonium chloride roasting. The process involved PCB delamination, roasting with ammonium chloride (NH4Cl), leaching, and copper hydroxide (Cu(OH)2) precipitation, which required calcination at 500 °C to obtain copper oxide (CuO) nanoparticles. Although it is declared as an environmentally friendly route, high energy consumption is reflected along the recovery process. Our research focused on the upcycling of the cupric chloride waste solution from PCB manufacturing. Although the waste solution is classified as hazardous waste, upcycling via recovery and nanoparticle synthesis could provide potentially high-value products to meet recent market needs. Based on economic viability and low energy consumption, our research objectives highlight dual points of waste recovery and the synthesis of copper nanoparticles for antibacterial application. This is to create commercial feasibility and to benefit health care treatments such as coatings on devices or wound dressing due to their effectiveness on skin regeneration [27,28]. To achieve good antibacterial properties [9], a high-purity product must be ensured via the recovery process, while the desired shape, size, and purity of the nanoparticles must be achieved via the synthesis method and parameters. Therefore, sonochemical reduction was selected to effectively control the particle size and shape in a short time without heat generation/consumption, as experienced by microwave irradiation, electrochemical synthesis, and thermal decomposition [10,12,13,14,15]. The effects of hydrazine addition were studied due to its potent reducing efficiency, stabilizing effect [29], and antibacterial properties [30], along with other parameters such as precursor concentration, pH, and synthesis time. Moreover, the process flow and material balance will be discussed for a larger-scale feasibility and process-cost analysis.

2. Materials and Methods

The upcycling of cupric chloride waste solution includes (i) the recovery of copper sulfate from waste solution and (ii) the synthesis of copper nanoparticles. An experiment was designed to study the effects of the process parameters on properties such as the particle size and shape and the composition, purity, and recovery of the recovered and final products. The effects of cementation time were studied in the first step using aluminium foil of higher than stoichiometry due to preliminary tests to ensure effective recovery. In the synthesis step, the effects of the synthesis technique (stirring vs. ultrasonic), synthesis time, and the amounts of reducing and capping agents (agent to copper sulfate molar ratios), along with the pH level, on the synthesized copper nanoparticles were investigated. The antibacterial activity test is included via the agar well diffusion method for the optimum condition. Details are provided as follows.

2.1. Cupric Chloride Waste Solution

The cupric chloride waste solution from the etching step was received from the PCB manufacturing company at an industrial estate in Thailand. Its composition was analyzed by ICP-OES, PerkinElmer model Optima 8000 ICP-OES Spectroscopy (PerkinElmer Inc., Waltham, MA, USA), using the Custom-Designed SolidState Detector calibration curve at 0.05, 0.1, 1, 5, 8, and 10 ppm, with an argon gas flow rate of 15 L/min. The ICP standards are Accustandard, and Single Element Standards, prepared using 5% HNO3. The green waste solution contained a copper content of 199.6 g/L, as listed in Table 1. Other elements found were sodium at 2.548 g/L and sulfur at 0.011 g/L. The pH of the original waste solution was 0.7. The waste solution was subjected to two steps of (i) copper recovery from cupric chloride waste solution and (ii) copper nanoparticle synthesis from the copper sulfate precursor as shown in Figure 1.

2.2. Recovery of Copper Sulfate from Spent Copper Etching Solution

Copper sulfate was recovered from the cupric chloride waste solution via cementation, leaching, and crystallization. First, the waste solution was diluted with DI water at a 1:1 ratio prior to cementation using aluminium foil at 3 g/50 mL for 10, 15, 60, and 120 min, to give brick-red precipitates. After filtration, the solid was subjected to leaching using 5 M sulfuric acid (H2SO4), at a solid-to-liquid (S/L) ratio of 1:10, under stirring at 500 rpm for 10 min with the addition of 10 vol.% hydrogen peroxide (H2O2) of 35% analytical reagent (AR) grade (Q RëC™, Auckland, New Zealand). The solution was left to undergo crystallization for 24 h, with and without agitation, to obtain copper sulfate crystals, which were filtered, rinsed, and dried at 105 °C for 1 h. The compositions of the recovered products after cementation, leaching, and crystallization were analyzed by XRD, Bruker model: D2 PHASER X-ray generator: Cu (WL = 1.54060 Å) 30 kV. ICP-OES (Optima 8000) was used to obtain the % recovery and % purity.

2.3. Synthesis of Copper Nanoparticles from Copper Sulfate Precursor

For preliminary tests, it is important to allow chemical reduction to occur by varying the pH of 6–13 using sodium hydroxide (NaOH) in the 0.01 M copper sulfate precursor prepared at 50 mL, 1 mL of hydrazine, and 25 mL of ethylene glycol. The transparent solution suddenly turned into an opaque yellowish solution, indicating the appearance of copper nanoparticles. A suitable pH of 12–13 gave dark brown particles of 0.3–0.4 microns. Next, key parameters—(i) hydrazine addition, (ii) ethylene glycol addition, and (iii) precursor concentrations—were varied to study their effects on the size, shape, and purity of copper nanoparticles.
The precursors were prepared using the recovered copper sulfate crystals at varied concentrations of 0.01, 0.10, and 0.20 M, at a pH of 12 and 13. The effects of hydrazine addition at 1, 2, 3, 4, and 5 mL (corresponded to hydrazine to copper sulfate ([N2H4]:[CuSO4]) molar ratios of 40:1, 80:1, 120:1, 160:1, and 200:1, respectively) were studied, using the 0.01 M copper sulfate precursor. Ethylene glycol to copper sulfate ([C2H6O2]:[CuSO4]) molar ratios were investigated at 0.10:1, 0.20:1, 0.30:1, 0.40;1, and 0.50:1 in relation to ethylene glycol additions of 5, 10, 15, 20, 25, and 30 mL, respectively.
Laboratory-grade chemicals were used: 80% hydrazine hydrate (CARLO ERBA Reagents, Milan, Italy), 99.9% ethylene glycol (KEMAUS Chemicals, Cherrybrook, New South Wales, Australia), and sodium hydroxide-Micropearls (RCI Labscan Limited, Bangkok, Thailand). Synthesis via magnetic stirring at 500 rpm was compared to ultrasonic (model: GT sonic d27, GT SONIC®, Hong Kong, China) operating at 45 kHz over a synthesis time of 2, 4, 6, 8, 10, and 60 min. The synthesized copper nanoparticles were subjected to centrifugation, vortexing, and ultrasonic cleaning for morphology and phase analysis, using the SEM model JEOL/JSM-6010LV (Medance B.V., Amsterdam, The Netherlands) operating at 15 kV in SEI mode; the field emission (FE)-SEM model Carl Zeiss Auriga (Carl Zeiss AG, Oberkochen, Germany), operating at 10 kV in SEI mode, 8.5 mm WD; and the TEM model Tecnai™ G2 20 S-TWIN (FEI Company, Hillsboro, OR, USA) operating at 200 kV in bright field mode. TEM images were taken for morphology and particle size analysis via Image J software (version: 1.54K) by obtaining at least a 100-particle population per condition. ICP-OES (Optima 8000-PerkinElmer Inc., Waltham, MA, USA) was employed to determine percentage purity and percentage recovery of the synthesized copper nanoparticles. Analytical reagent (AR)-grade copper sulfate (KEMAUS Chemicals, Cherrybrook, New South Wales, Australia) was used to synthesize copper nanoparticles to compare with those obtained using recycled copper sulfate. The antibacterial test was performed via agar well diffusion [31] using “Escherichia coli (E. coli)” cultured in Luria–Bertani medium (LB agar), (Difco, BBL™, Baltimore, MD, USA) at 37 °C for 24 h to obtain 108–109 CFU (colony forming unit). Serial dilution was applied. The zone of inhibition (ZOI) was compared to controlled conditions, with and without antibiotics.

3. Results and Discussion

3.1. Copper Sulfate Recovered from the Spent Copper Etching Solution

After cementation, the aluminium foil was completely dissolved, giving a brick-red precipitate as shown in Figure 2. The optimum time was 10 min. The XRD result showed the copper chloride (CuCl) spectra, indicating it as the main phase, along with copper (Cu) and copper oxide (Cu2O) spectra (shown in Figure 3a). The copper contents in the solutions analyzed by ICP-OES before and after cementation were 99.8 g/L and 0.053 g/L, respectively, as listed in Table 2. However, a 10% volume loss of the solution during cementation by the heat generated was considered for the calculation of percentage recovery. Based on 50 mL of waste solution containing copper contents of 4.99 g/50 mL and 2.385 mg/45 mL after cementation, the process thereby gave 99.95% recovery. During sulfuric leaching, complete dissolution was observed, and the copper sulfate crystallized in a few minutes and then grew with time. After 24 h without stirring, large (10–20 mm) copper sulfate crystals were readily filtered. Stirring at 500 rpm, however, resulted in copper sulfate crystals of 1–3 mm or finer, making filtration more difficult. The XRD result confirmed the main product as copper sulfate pentahydrate (CuSO4·5H2O), as depicted in Figure 3b. The ICP-OES result as listed in Table 3 indicates the metal concentration (g/L) in the solutions before and after crystallization. It is noted that a 5% loss of solution after crystallization was observed due to water molecules in the copper sulfate pentahydrate. Based on 100 mL of leached solution before crystallization and the copper contents of 5.501 g/100 mL and 0.26885 g/95 mL after crystallization, 94.76% recovery was achieved. The contents of other elements were measured as lower than the detection limits in chemical composition data, providing the purity of the recovered copper sulfate as >99.95%, as listed in Table 4. High-purity copper sulfate crystals were subsequently used as precursors for copper nanoparticle synthesis.
As compared to copper sulfate recovery by the Old Bridge Chemicals process [6], ~85 g/L Cu in the solution was recovered (prior to surface-cooled crystallization) from the cupric and cuprous chloride etching solution of ~150 g/L Cu. From the invented process, comparable results are obtained, in which 55.01 g/L Cu in the solution (prior to crystallization) was obtained from a 99.8 g/L Cu waste solution (1:1 dilution). As the Old Bridge Chemicals process contains two types of waste, it requires more steps of physical separation, leaching, and four solvent extraction circuits followed by stripping and crystallization. The proposed technique is perchance more beneficial due to shorter steps, including cementation, leaching and crystallization, plus less expensive chemicals being used. Aluminium cementation selectively offered copper-containing precipitates suitable for leaching to gain high-purity recovered products. As compared to the process by G. Zhao et al. [7], their recovery was lower, and the process required energy resources for distillation at 95–135 °C. An alternative method to recycle acidic cupric chloride waste solution via electrowinning using composite electrolytic cell to obtain copper at the cathode was reported to gain effective results [32]. However, it might require higher energy through electricity consumption along with safety measures for chlorine gas generation. Thus, the proposed copper sulfate recovery is more practical and economical at the higher percentage recovery and percentage purity.

3.2. Effects of Synthesis Parameters on Size, Shape, and Composition of Copper Nanoparticles

The key synthesis parameters, including synthesis techniques (mechanical stirring and ultrasonic) and time, and hydrazine and ethylene glycol additions, along with precursor concentration and pH, showed significant effects on the copper nanoparticles. Figure 4a,b reveal additions of hydrazine and ethylene glycol that changed the precursor’s color to opaque yellow and turned dark brown when reaching 10 min, detailed as follows.

3.2.1. Effects of Synthesis Techniques and Time

Under ultrasonic, adding 1 mL of hydrazine and 25 mL of ethylene glycol resulted in smaller particle sizes of copper nanoparticles compared to those synthesized via stirring as illustrated in Figure 5a,b, respectively. Ultrasonic synthesis generally gave a more uniform nanoparticle size. Increasing the synthesis time up to 10 min did not significantly increase the copper nanoparticle size via either stirring or ultrasonic, as shown in Figure 6a–e, demonstrating comparable copper nanoparticle sizes of 100–280 nm under ultrasonic. However, synthesis at 60 min led to a notable increase in size to 360–640 nm under stirring, as illustrated in Figure 7a–d. This is consistent with research by J. Moghimi-Rad et al. [11] using ultrasonic-assisted particle size reduction, giving size reductions from 253.4 ± 74.3 nm (without ultrasonic) to 112.8 ± 19.1 nm (with ultrasonic).

3.2.2. Effects of Hydrazine and Ethylene Glycol Additions

As the hydrazine content increased from 1 to 5 mL (using 0.01 M CuSO4 precursor, 25 mL of 0.01 M ethylene glycol, and 2 min), the copper nanoparticle size reduced significantly as demonstrated by the TEM images taken at high and lower magnifications in Figure 8a–j. This emphasized the effective reducing effect of hydrazine for copper nanoparticle synthesis. Low additions (1–2 mL) generally exhibited large and small particles in agglomerated forms, while higher additions (3–5 mL) exhibited a more uniform size of the copper nanoparticles. At the optimum hydrazine addition of 5 mL, variation in ethylene glycol of 5–30 mL was subsequently carried out under the same synthesis conditions. A slight decrease in copper nanoparticle size was observed, as shown in Figure 9a–f.
Figure 10 exhibits a particle size reduction due to hydrazine and ethylene glycol addition. The particle size decreased from 114.18 ± 30.64 nm to 54.54 ± 11.04 nm as 1 to 5 mL of hydrazine was added, providing more uniform (narrow) size distribution towards 5 mL. Ethylene glycol addition (5–30 mL) slightly reduced the size of copper nanoparticles from 61.76 ± 12.40 nm to 54.85 ± 11.45 nm, respectively (at 5 mL of hydrazine addition), as illustrated in Figure 11c,d. Although the capping agents retard particle growth and coalescence [33], J. M.-Rad et al. [11] indicated increasing copper nanoparticle size with increasing ethylene glycol, due to a decreasing reduction rate. In the invented process, hydrazine might have exceeded the optimum levels and dominated particle size reduction over ethylene glycol. The addition of 4–5 mL of hydrazine was found to be effective, giving a size of 56.08 to 54.54 nm, at which 5 mL was preferred, while ethylene glycol at 25 mL was the optimal value.

3.2.3. Effects of Precursor Concentrations

Increasing the precursor concentration from 0.01 M to 0.10 M and 0.20 M (using 5 mL of hydrazine and 25 mL of ethylene glycol) resulted in increasing particle sizes from 54.54 ± 11.04 nm to 151.11 ± 41.98 nm and 173.29 ± 51.88 nm, respectively. It should be noted that percentage recovery increased slightly with increasing precursor concentration, as shown in Figure 12a–f for 15 mL of hydrazine, at pH 12 (solid symbols) and pH 13 (open symbols). The overall results showed a recovery > 92%. It could be explained that a higher precursor concentration with increased copper ions facilitates chemical reduction to a greater degree and causes more particle growth beyond the critical size, and particle coalescence might yield slightly higher recovery, with increasing particle size, however. Work by M.A. Alam et al. supported that increasing the copper precursor concentration led to a larger nanoparticle size due to more copper atoms being available to form larger particles [34]. The optimum precursor concentration is considered based on decided applications such as chemical or biomedical. Typically, particles of less than 200 nm are considered as nanoparticles, while a size of ~60 nm is reported to be preferable for antibacterial purposes [35]. Therefore, a 0.01 M precursor concentration is recommended.

3.2.4. Phase and Composition of the Synthesized Copper Nanoparticles

Comparatively, the copper nanoparticles synthesized from precursors prepared from the recycled copper sulfate and the AR-grade copper sulfate showed a similar size and shape, according to TEM images, as shown in Figure 13a,b, respectively. The commercial copper nanoparticles are compared, as illustrated in Figure 14a–d. XRD analysis confirmed that copper is the main phase and cupric oxide (CuO) was minorly detected, probably on the copper nanoparticle surfaces. Although the commercial copper nanoparticles showed similar XRD results, the agglomeration of small and much larger-sized particles is evident. For all conditions (1–5 mL of hydrazine, pH 12 and 13, 0.01–0.20 M CuSO4 precursor), a purity of >99.95% was achieved, as listed in Table 5, due to the high-purity copper sulfate recovered by the proposed technique. As high-purity copper nanoparticles with a high recovery of at least 92% were obtained in all cases, it is therefore feasible to upcycle cupric chloride waste solution to produce valuable copper nanoparticles using the invented process.

3.3. Antibacterial Activity of the Synthesized Copper Nanoparticles

The synthesized copper nanoparticles were tested for antibacterial activity via agar well diffusion, using E. coli at 108–109 CFU. The ZOI was 50 mm at 127 mg/mL, comparable to the one tested using antibiotics, as shown in Figure 15. Since the antibacterial activity tests are varied due to the different standards and protocols employed, a comparison of the results might experience some difficulties. Research by T. Mehdizadeh et al. [36] indicated the agar well diffusion result for E. coli (105 CFU), showing a ZOI of 6.41 ± 2.27 mm at 5 mg/mL using copper nanoparticles (15–22 nm size) fixed on cellulosic walnut shell material, synthesized using sodium borohydride for 3 h. Work by G. F. Galal [37] reported the agar well diffusion result of E. coli on extracellular stable P. silesiensis strain A3 protein-coated copper nanoparticles, giving a ZOI of 40 ± 0.71 mm at 1 mg/mL, slightly higher than the ZOI of 35 ± 0.34 mm at 1 mg/mL using antibiotics, using a nanoparticle size of 30.2 nm. It provided an activity index (AI), expressed as the diameter ratio of the inhibition zone of nanoparticles to the standard antibiotics, of 1.14. The test results of copper nanoparticles synthesized by the invented process showed a comparable antibacterial activity to that of antibiotics, providing an AI of 1.0 and thereby proving the acceptable antibacterial activity. The larger surface area per unit volume of smaller nanoparticles provides better antibacterial activity to release copper ions to disrupt bacterial membranes [38]. Their spherical shape also promotes significant antibacterial activities against E. coli due to thinner cell membranes to cause the leakage of cellular contents and cell death after the attack. As Gram-negative bacteria such as E. coli are common for human infections and become more resistant to antibiotics [39], this therefore addresses the significance and benefits of copper nanoparticles in medical areas.

3.4. Process Flow and Material Balance of Copper Nanoparticles from Spent Copper Etching Solution

Copper nanoparticles were successfully synthesized via sonochemical reduction using copper sulfate recycled from cupric chloride waste solution in this research. The process flow and material balance are summarized in Figure 16. In the first step, cupric chloride waste solution (199.6 g Cu/L) was first recovered through cementation using aluminium foil at an S/L ratio of 0.06 kg/L prior to acid leaching using 5 M sulfuric acid solution at a 1:10 S/L ratio, plus 10 vol.% hydrogen peroxide added as the oxidant via 10 min stirring. Through crystallization for 24 h, followed by filtration and drying, 99.95% purity copper sulfate pentahydrate crystals at 94.76% recovery (0.362 kg) were obtained, which were used as the precursor for copper nanoparticle synthesis in the next step. The recovered copper sulfate obtained in this research offered a better percentage recovery and percentage purity than those obtained from previous work by G. Zhao et al. [7], due to aluminium cementation [8] making leaching more effective. The 0.01 M copper sulfate precursor was mixed with 1 M sodium hydroxide solution (0.35 kg NaOH and 8.71 L DI water), 98% hydrazine (8.71 L) as the reducing agent, and 0.01 M ethylene glycol (0.04 L ethylene glycol and 72.57 L DI water) as the capping agent. After sonochemical reduction at 45 Hz for 2 min, spherical copper nanoparticles (0.203 kg) of 54.54 nm were obtained at >99.95% purity. From the material balance, it follows that 1 L of cupric chloride etching waste solution, having an original copper content of 199.6 g/L, gives ~203 g copper nanoparticles from weight basis calculation on recovery. The weight of copper nanoparticles after upcycling is, however, slightly higher (~1.70%) than the original copper content in the waste solution. This might be due to remaining elements on the surfaces such as copper oxides formed during cleaning. The overall process consists of two steps of (i) copper recovery from cupric chloride waste solution and (ii) copper nanoparticle synthesis, which provided 87.22% recovery totally.

3.5. Chemical Reactions of Copper Nanoparticle Synthesis from Copper Etching Waste Solution

The chemical reactions taking place can be explained as follows. For aluminium cementation, copper metal (Cu0) was obtained according to Equation (3) [8], giving aluminium chloride (AlCl3) as a byproduct, which can be purified for further uses [3,40].
3Cu2+ + 2Al → 2Al3+ + 3Cu0, Eo = +1.997 V
Based on copper depletion from the waste solution, the metal recovery was 99.95% and the main cementation products were copper chloride and copper metal. It is plausible that an intermediate cuprous product might exist in the copper recovery pathway [8] to give copper chloride as the co-precipitate product. The subsequent sulfuric acid leaching resulted in copper sulfate solution following the expressions in Equations (4) and (5) [41]. The cuprous ions (Cu+), however, were reported to be unstable in sulfuric acid and give Cu2+ when oxidant (H2O2) is present [42]. The crystallized copper sulfate pentahydrate (CuSO4·5H2O) was therefore obtained in this case.
CuCl (s) + H2SO4 (l) → CuSO4 (aq) + H2O (l) + HCl (l) + SO2 (g)
Cu (s) + H2SO4 (l) → CuSO4 (aq) + H2O (l) + SO2 (g)
Under sonochemical synthesis, metal ion reduction by hydrazine (N2H4) in the presence of hydroxyl (OH−) via a redox reaction as described in Equation (6) [43] could lead to the formation of copper metal in Equation (7) from the copper sulfate (CuSO4) precursor.
(4/n)Mn+ + N2H4 + 4OH− → (4/n) M (s) + N2 (g) + 4H2O (l)
2CuSO4 + N2H4 +4NaOH → 2Cu + N2 + 4H2O + 2Na2SO4
N2H4 + H2O → N2H5+ + OH−
N2H4 + O2 → N2 + 2H2O
As hydrazine is a weak base according to Equation (8) [44], it gives a positive effect to the reduction reaction of metal ions (Mn+) to the metallic state (M0), in combination with pH control. However, hydrazine can react with dissolved oxygen (DO) in the solution, according to Equation (9) [45], and self-oxidation and -reduction can occur in both alkaline and acidic solutions. It might be that a greater amount of hydrazine would be required than expected by the hydrazine-to-copper-sulfate [N2H4]:[CuSO4] molar ratio in Equation (7). Nevertheless, this self-oxidation might play an important role in providing high-purity copper nanoparticles, observed as less copper oxide on the surface, detected by XRD. This, however, led to a high consumption of hydrazine, especially under sonication. An investigation by N. N. Begletsova et al. [46] indicated that low [N2H4]:[Cu(II)] = 10:1 was not feasible, while higher [N2H4]:[Cu(II)] at 100:1, 200:1, and 300:1 provided copper nanoparticles, but with an inconsistent size (30–90 nm). According to Equation (8), hydrazonium ions (N2H5+) could react with negative charges of copper nanoparticles, resulting in polydisperse nanoparticles, or cause agglomeration, which requires deagglomeration. In comparison to the invented process, hydrazine addition gave a significant size reduction from 114.18 nm ([N2H4]:[CuSO4] = 40:1) to 54.54 nm (200:1), which was found to be comparable. No agglomeration and good stability of the copper nanoparticles was observed for >2 weeks, plausibly due to sonication and an excess amount of hydrazine that was also reflected in the antibacterial test to give a good antibacterial property similar to that of antibiotics. In combination with high pH control, hydrazine offered fast kinetics, yielding a short synthesis time. Excessive amounts of hydrazine were reported to give shape variations other than spherical [47]. The invented technique employed high amounts of hydrazine ([N2H4]:[CuSO4] = 200:1) and resulted in particle shape being entirely spherical or polygonal with high purity for all conditions investigated, which allowed better control over the synthesis process and high efficiency.
The role of ethylene glycol could be explained in two aspects: (i) as the reducing agent [48] and (ii) as the capping agent for nanoparticle synthesis [33]. First, complexes of [Cu(OH)4]2− are formed in the solution as the copper sulfate precursor is in the presence of sodium hydroxide. When ethylene glycol is added to the alkaline copper sulfate solution, Cu(OH)2 [11] gives [Cu(C2H4O2)2]2− complexes as shown in Equation (10) and is subsequently reduced to give the element copper by overall reduction in Equation (11) [49]. However, increasing ethylene glycol from 5 to 30 mL ([C2H6O2]:[CuSO4] molar ratios of 0.1:1 to 0.6:1) slightly reduced the particle size from 61.67 nm to 54.85 nm. The “capping mechanism” occurs by giving the hydroxyl group of ethylene glycol a thin film coating on the copper nanoparticle surfaces to stabilize and prevent particle agglomeration [48]. In general, the ethylene-glycol-to-copper-salt solution molar ratio is found to be varied or not strictly defined for copper nanoparticle synthesis and depends on the specific synthesis method and normally gives spherical particles [49,50,51].
Cu(OH)2 + C2H6O2 → CuC2H4O2 + 2H2O
Cu(OH)2 → CuC2H4O2 → Cu2O → Cu
The effect of pH (sodium hydroxide addition) played a significant role as Cu(OH)2 in the alkaline copper sulfate solution [11] aids the copper ions’ reduction via Equations (10) and (11). It has been reported that the pH has notable impacts on the size, shape, stability, and aggregation of the synthesized nanoparticles [46,52,53,54] in that a high pH level (alkali precursor) towards pH 10–12 or >12 facilitated smaller nanoparticles and better stability. Also reported by J. Paul Chen et al. [44], the pH of the copper precursor solution should be controlled above 11 to produce effective reduction by hydrazine. It might be that the active species such as Cu(OH)2 or [Cu(C2H4O2)2]2− complexes are in deprotonated form and prone to reduction, thereby giving a greater reaction rate in reducing Cu2+ ions to Cu nuclei [11,53,54]. In comparison to work by J. Moghimi-Rad [11], relatively large copper nanoparticles of 112.8 nm average size were obtained under pH 4, which emphasizes pH’s effect on size reduction. The reduced nanoparticle size also supports antibacterial properties, and a high pH level of 12–13 was therefore preferable in this case.
The treatment of byproducts is now addressed regarding environmental concerns. For cementation, aluminium chloride could be used as a starting material to make rubber, lubricants, wood preservatives, and paints or to produce polyaluminium chlorides (PACs) for coagulation in water and wastewater treatment [3,40]. The released hydrogen gas can be recaptured. The waste solution (ineffective hydrochloric) obtained after sulfuric leaching, followed by crystallization and filtration in Equation (4), should be neutralized before disposal. Sulfur dioxide (SO2) gas must be subjected to air treatment conforming to air pollution regulations. The sonochemical synthesis for a larger scale would be equipped with an inert (argon) gas protection equipment.

3.6. Nucleation and Growth Mechanisms of Copper Nanoparticle via Sonochemical Synthesis

According to the synthesis parameters (precursor concentration and pH, hydrazine and ethylene glycol additions, ultrasonic, and synthesis time) discussed so far, sonochemical reduction has proved effective in controlling the size and shape of the copper nanoparticles via the creation, growth, and collapse of bubbles [16] and preventing aggregation. The nucleation and growth of copper nanoparticles synthesized using hydrazine and ethylene glycol as reducing and capping agents can be explained through reduction, nucleation, growth, coalescence, and intraparticle growth as follows [55,56,57]. First, the rapid reduction of copper ions to copper atoms occurs in the presence of hydrazine under pH control. Secondly, the nucleation immediately starts as the nuclei grow by the attachment of atoms in the liquid to form dimers and trimers. Third, the growth stage is via an Oswald ripening process as smaller particles dissolve to grow larger particles to reduce the surface-to-bulk ratios. Fourth, the particles coalescence with or without preference on attachment. Fifth, the intraparticle growth is due to the diffusion-controlled aggregative growth of copper nanoparticles by monomer diffusion along the nanoparticle surfaces that affect the particle shape. The sonication helps to accelerate the chemical reaction by dispersing hydrazine in the reduction step and increasing nucleation, while the growth is interrupted by a short collapse of minute bubbles, which helps to control the copper nanoparticle size and shape [16] required for antibacterial properties.

3.7. Feasibility Studies of Copper Nanoparticle Synthesis from Copper Etching Waste Solution

A comprehensive economic assessment was conducted alongside an evaluation of the process’s profit to prove the industrial applicability of this upcycling route. A cost analysis was performed for copper nanoparticle synthesis from 1 L of cupric chloride waste solution, encompassing raw material costs, chemical consumption, wastewater treatment expenses, and electricity expenditure. The system boundary for this analysis is defined in Figure 17a, containing both copper sulfate recovery from the cupric chloride waste solution and the subsequent copper nanoparticle synthesis. The calculation is based on the domestic cost and expressed in US dollars at the exchange rate in January 2025. The detail summarizes the total consumption of each section as depicted in Figure 17b. Chemical consumption (93.23%) constitutes the most significant cost component of copper nanoparticle synthesis, with water usage for mixing and dilution constituting a significant portion, a characteristic commonly observed in chemical synthesis processes [58,59]. Electrical energy owing to the drying step constitutes a minor portion of the overall process cost. Moreover, the energy input for this sonochemical synthesis is expected to be considerably lower than for alternative approaches, such as chemical reduction [60], sol-gel [61,62], electrochemical [12,13], and thermal decomposition methods [14,15]. This is attributed to the significantly shorter time (2 min sonication) at ambient operating temperature of the invented process compared to those alternatives, which generally require longer processing times and elevated temperatures. This could help to minimize the total process time, rendering the productivity boost at lower costs. Figure 17c depicts the revenue generated from the synthesized copper nanoparticles (USD 807.94), which significantly exceeds the total operational costs (USD 14.02), resulting in a substantial net profit of USD 793.74 (per liter of initial cupric chloride waste solution). This demonstrates the economic viability and feasibility of the invented process. Note that this analysis excludes labor and equipment costs and the potential revenue from byproducts is not considered as these are expected to be reintegrated into the industrial production cycle, as discussed previously. Supplementary Materials detailing the cost calculation, electricity calculation along with the revenue, processing cost, and profit calculations for copper nanoparticle synthesizing from 1 L of CuCl2 waste solution mentioned previously can be downloaded at https://www.mdpi.com/article/10.3390/recycling10030097/s1. By considering the recovery rate of the invented process (for copper nanoparticle synthesis), the recovery rate was found to be acceptable (>92% for 0.10–0.20 M precursor concentrations) via a short synthesis time of 2 min, due plausibly to the high amount of hydrazine used. In comparison to a novel non-dispersive membrane nanoprecipitation process [30], ~100% recovery (excluding the drying process) was reported, yielding nanoparticles of 200 nm in size without indicating their purity and antibacterial activity. Although the recovery rate of the current research was lower than that of the novel non-dispersive membrane nanoprecipitation process, a smaller copper nanoparticle size with high purity obtained by the invented process was more appreciably desirable, particularly for antibacterial properties. In addition, the precursor recovered from the waste solution provided options for environmental and economic concerns, which makes the invented process more attractive in terms of sustainable materials and green processes.
The synthesis of copper nanoparticles from secondary sources (cupric chloride waste solution) aligns with circular economy concepts [63]. This invented process offers a sustainable alternative to virgin nanoparticle production materials, which might be expanded to apply to other waste sources such as e-waste, acid mine drainage, and metallurgical slag [64]. The sonochemical method minimizes energy consumption and processing time, thereby reducing the overall environmental footprint. In this way, repurposing the waste solution mitigates the environmental impact by reducing reliance on primary resources and presents significant economic potential for sustainable industry [65]. Moreover, with the synthesis parameters (precursor concentration and pH, amounts of reducing and capping agents, and synthesis time) used, it is practical to control the particle shape to be solely spherical or polygonal with a particle size of 54.54 nm suitable for antibacterial applications [37,38] via the optimum condition. This renders applications in would healing [27,28] or dentistry such as dental materials containing copper nanoparticles categorized as (i) metals and alloys, (ii) polymers and resins, (iii) restorative cements, and (iv) miscellaneous dental materials [66], which can be further explored. For synthesis using a 0.01–0.20 M copper sulfate precursor, it offers a particle size of 54.54–173.29 nm which can be used for other applications such as chemical uses. Although synthesis via plant extracts claims to be more environmentally friendly, complicated reactions can be expected and are still difficult to control due to various types of biomolecules that make stoichiometry difficult for metal reduction and still face challenges [67]. Therefore, apart from its effectiveness and low energy consumption, the invented process is feasible for domestic investment and ecosystems, as well as in line with government policy on turning waste into value.

4. Conclusions

The upcycling of cupric chloride waste solution from PCB manufacturing could be effectively achieved via two steps of (i) copper recovery from the waste etching solution and (ii) the synthesis of copper nanoparticles via sonochemical reduction. The first step involved aluminium cementation followed by sulfuric leaching and crystallization to give a 94.76% recovery of copper sulfate pentahydrate at 99.95% purity. The incorporation of aluminium cementation selectively provided copper-containing precipitates suitable for effective leaching to gain recovered products of high purity, which is greater than that obtained by previous processes involving leaching and crystallization alone. The high purity of the recovered copper sulfate product also ensured the high purity of the copper nanoparticles to be synthesized in the second step. Via sonochemical reduction, 0.01 M copper sulfate precursor of 50 mL at pH 12–13 was synthesized for 2 min using hydrazine and ethylene glycol as the reducing and capping agents, respectively. A high [N2H4]:[CuSO4] = 200:1 was considered as the optimum condition to give spherical or polygonal copper nanoparticles of 54.54 nm. Hydrazine addition under high pH control played a key role in efficiently giving fast kinetics for the reduction of copper nanoparticles. All synthesis conditions investigated could provide copper nanoparticles with a purity >99.95% and >92% recovery. Small spherical nanoparticles of high purity are favorable for antibacterial activity, which shows a ZOI of 50 mm at 127 mg/mL, comparable to the results obtained from the controlled condition using antibiotics. From economic assessment of the process and cost analyses that benefit both environmental and economic impacts in minimizing energy consumption with a short recovery route, along with a reduced processing time and operating temperature, upcycling is therefore potentially commercial for green material production from industrial waste. Based on the economic viability and energy consumption aspects, the invented process provides an excellent alternative solution competitive with the existing recycling technologies in that it combines waste recovery and copper nanoparticle synthesis aiming for high-value-added products potentially for medical applications.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/recycling10030097/s1, Table S1: Cost calculation for Cu nanoparticle synthesizing from 1 L of CuCl2 waste solution; Table S2: Electricity calculation for Cu nanoparticle synthesizing from 1 L of CuCl2 waste solution; Table S3: Revenue, processing cost, and profit calculations for Cu nanoparticle synthesizing from 1 L of CuCl2 waste solution.

Author Contributions

Conceptualization, S.K. and T.T.; methodology, T.P., C.K. and T.C.; validation, S.K. and T.T.; formal analysis, T.P., C.K., N.M., S.C. and T.C.; writing—original draft preparation, T.P.; writing—review and editing, S.K. and T.Y.; funding acquisition, T.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Department of Primary Industries and Mines, Ministry of Industry, Thailand, grant number: 17/2023. 25 January 2023–19 November 2023.

Data Availability Statement

The data presented in this study are available in Supplementary Material.

Acknowledgments

Thanks are due to the Innovative Processing and Recycling of Metals Research Center (IPRMRC), School of Metallurgical Engineering, Suranaree University of Technology (SUT), the students and research team for their strenuous work, and the technicians at the Center for Scientific and Technological Equipment (CSTE) at SUT for generous equipment training and advice. The authors would like to acknowledge the PCB manufacturing plant for providing industrial waste to this research.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Experimental diagram. Step I: Copper recovery from cupric chloride waste solution. Step II: Copper nanoparticle synthesis.
Figure 1. Experimental diagram. Step I: Copper recovery from cupric chloride waste solution. Step II: Copper nanoparticle synthesis.
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Figure 2. Cementation using aluminium foil followed by sulfuric acid leaching and crystallization.
Figure 2. Cementation using aluminium foil followed by sulfuric acid leaching and crystallization.
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Figure 3. XRD spectra of products: (a) after cementation, (b) after crystallization.
Figure 3. XRD spectra of products: (a) after cementation, (b) after crystallization.
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Figure 4. Synthesis of copper nanoparticles via (a) stirring at 500 rpm and (b) ultrasonic at 45 kHz (1 mL of hydrazine and 25 mL of ethylene glycol).
Figure 4. Synthesis of copper nanoparticles via (a) stirring at 500 rpm and (b) ultrasonic at 45 kHz (1 mL of hydrazine and 25 mL of ethylene glycol).
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Figure 5. Effects of stirring at 500 rpm and ultrasonic (45 kHz) on size of copper nanoparticles, synthesized for 2 min (1 mL of hydrazine and 25 mL of ethylene glycol).
Figure 5. Effects of stirring at 500 rpm and ultrasonic (45 kHz) on size of copper nanoparticles, synthesized for 2 min (1 mL of hydrazine and 25 mL of ethylene glycol).
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Figure 6. Effects of synthesis time (2–10 min) on size of copper nanoparticles (1 mL of hydrazine, 25 mL of ethylene glycol).
Figure 6. Effects of synthesis time (2–10 min) on size of copper nanoparticles (1 mL of hydrazine, 25 mL of ethylene glycol).
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Figure 7. Copper nanoparticles synthesized for 10 and 60 min using stirring at 500 rpm and ultrasonic at 45 kHz (1 mL of hydrazine, 25 mL of ethylene glycol).
Figure 7. Copper nanoparticles synthesized for 10 and 60 min using stirring at 500 rpm and ultrasonic at 45 kHz (1 mL of hydrazine, 25 mL of ethylene glycol).
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Figure 8. TEM images showing effect of hydrazine addition (1–5 mL) on size of copper nanoparticles at high and lower magnifications. (25 mL of ethylene glycol).
Figure 8. TEM images showing effect of hydrazine addition (1–5 mL) on size of copper nanoparticles at high and lower magnifications. (25 mL of ethylene glycol).
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Figure 9. TEM images showing effect of ethylene glycol addition (5–30 mL) on size of copper nanoparticles (1 mL of hydrazine).
Figure 9. TEM images showing effect of ethylene glycol addition (5–30 mL) on size of copper nanoparticles (1 mL of hydrazine).
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Figure 10. Effects of hydrazine and ethylene glycol additions on copper nanoparticle size.
Figure 10. Effects of hydrazine and ethylene glycol additions on copper nanoparticle size.
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Figure 11. Effects of hydrazine and ethylene glycol additions on size and size distribution of copper nanoparticles.
Figure 11. Effects of hydrazine and ethylene glycol additions on size and size distribution of copper nanoparticles.
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Figure 12. Effect of precursor concentration on percentage recovery of copper nanoparticles.
Figure 12. Effect of precursor concentration on percentage recovery of copper nanoparticles.
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Figure 13. Copper nanoparticles synthesized from (a) recycled and (b) AR-grade copper sulfate.
Figure 13. Copper nanoparticles synthesized from (a) recycled and (b) AR-grade copper sulfate.
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Figure 14. XRD and SEM analysis of synthesized and commercial copper nanoparticles.
Figure 14. XRD and SEM analysis of synthesized and commercial copper nanoparticles.
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Figure 15. Zone of inhibition (ZOI) for antibacterial activity test of the synthesized copper nanoparticles.
Figure 15. Zone of inhibition (ZOI) for antibacterial activity test of the synthesized copper nanoparticles.
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Figure 16. Process flow and material balance of copper sulfate recovery and copper nanoparticle synthesis.
Figure 16. Process flow and material balance of copper sulfate recovery and copper nanoparticle synthesis.
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Figure 17. (a) System boundary economic assessment, (b) cost distribution diagrams, (c) revenue, cost, and profit for copper nanoparticle synthesis from 1 L of cupric chloride waste solution. (*By-product can be use as a starting materials for other processes such as making rubber).
Figure 17. (a) System boundary economic assessment, (b) cost distribution diagrams, (c) revenue, cost, and profit for copper nanoparticle synthesis from 1 L of cupric chloride waste solution. (*By-product can be use as a starting materials for other processes such as making rubber).
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Table 1. Chemical composition of cupric chloride waste solution (by ICP-OES).
Table 1. Chemical composition of cupric chloride waste solution (by ICP-OES).
WasteMetal Concentration (g/L)
CuPbSnAgFeNiMnSNa
CuCl2 solution199.6n/an/an/an/an/an/a0.0112.548
Table 2. Chemical composition of solutions before and after cementation (by ICP-OES).
Table 2. Chemical composition of solutions before and after cementation (by ICP-OES).
SolutionMetal Concentration (g/L) in Solution% Recovery
CuSnPbAlFeNaNiS
Before99.80<limit<limit<limit<limit0.013<limit<limit99.95 *
After0.053<limit<limit92.55<limit0.005<limit<limit
Note: * the calculation includes 10% volume loss of the solution due to heat generation during cementation.
Table 3. Chemical composition of solutions before and after crystallization (by ICP-OES).
Table 3. Chemical composition of solutions before and after crystallization (by ICP-OES).
SolutionMetal Concentration (g/L) in Solution% Recovery
CuSnPbAlFeNaNiS
Before55.010<limit<limit1.840<limit<limit<limit<limit94.76 **
After2.830<limit<limit0.167<limit<limit<limit<limit
Note: ** the calculation includes 5% volume loss of the solution due to water molecules in copper sulfate pentahydrate during crystallization.
Table 4. Chemical composition of recovered copper sulfate pentahydrate (by ICP-OES).
Table 4. Chemical composition of recovered copper sulfate pentahydrate (by ICP-OES).
SolutionMetal Concentration (g/L) in Solution% Purity
SnPbAgFeNiNaMnAlS
CuSO4·5H2O<limit<limit<limit<limit<limit<limit<limit<limit<limit>99.95
Table 5. Purity of commercial and synthesized copper nanoparticles (by ICP-OES).
Table 5. Purity of commercial and synthesized copper nanoparticles (by ICP-OES).
Cu Nanoparticles (Cu NPs)Hydrazine (mL)pHMetal Concentration (mg/L)% Purity
NaS
Commercial--<limit<limit>99.95
0.01 M CuSO4 precursor512<limit<limit>99.95
0.01 M CuSO4 precursor513<limit<limit>99.95
0.10 M CuSO4 precursor512<limit<limit>99.95
0.10 M CuSO4 precursor513<limit<limit>99.95
0.20 M CuSO4 precursor512<limit<limit>99.95
0.20 M CuSO4 precursor513<limit<limit>99.95
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MDPI and ACS Style

Patcharawit, T.; Kansomket, C.; Mahiwan, N.; Chailoi, S.; Chandakhiaw, T.; Yingnakorn, T.; Tunnukij, T.; Khumkoa, S. Upcycling of Cupric Chloride Waste Solution from PCB Manufacturing for Antibacterial Copper Nanoparticles. Recycling 2025, 10, 97. https://doi.org/10.3390/recycling10030097

AMA Style

Patcharawit T, Kansomket C, Mahiwan N, Chailoi S, Chandakhiaw T, Yingnakorn T, Tunnukij T, Khumkoa S. Upcycling of Cupric Chloride Waste Solution from PCB Manufacturing for Antibacterial Copper Nanoparticles. Recycling. 2025; 10(3):97. https://doi.org/10.3390/recycling10030097

Chicago/Turabian Style

Patcharawit, Tapany, Chatisa Kansomket, Napat Mahiwan, Sumita Chailoi, Thanapon Chandakhiaw, Tanongsak Yingnakorn, Teerawut Tunnukij, and Sakhob Khumkoa. 2025. "Upcycling of Cupric Chloride Waste Solution from PCB Manufacturing for Antibacterial Copper Nanoparticles" Recycling 10, no. 3: 97. https://doi.org/10.3390/recycling10030097

APA Style

Patcharawit, T., Kansomket, C., Mahiwan, N., Chailoi, S., Chandakhiaw, T., Yingnakorn, T., Tunnukij, T., & Khumkoa, S. (2025). Upcycling of Cupric Chloride Waste Solution from PCB Manufacturing for Antibacterial Copper Nanoparticles. Recycling, 10(3), 97. https://doi.org/10.3390/recycling10030097

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