Method for removing copper ions in electroplating wastewater by high-efficiency electric adsorption based on iron-based chalcogenides

Abstract

The application provides a method for removing copper ions in electroplating wastewater by efficient electric adsorption based on iron-based chalcogenide compounds, which comprises the following steps: synthesizing FeSe2 by one-step hydrothermal method; adding pyrrole monomer and an oxidizing agent to the FeSe2 suspension to perform a polymerization reaction, so as to obtain a FeSe2@PPy composite material; and making the copper-containing electroplating wastewater pass through a CDI device, so that the copper ions are removed by electric adsorption on the surface of a cathode. 2+ The application applies FeSe2 material to the field of CDI copper removal for the first time, explains the coordination interaction mechanism between Cu 2+ and chalcogen active sites from the mechanism, reveals the internal reason for selective removal, and inhibits Fe dissolution and structure degradation by poly-pyrrole surface coating modification, so as to realize electric adsorption copper removal with high adsorption capacity and high selectivity, and the Cu 2+ removal rate of the copper-containing electroplating wastewater reaches 90.0%; and the application has a very good industrial application prospect in the field of CDI.

Description

Technical Field

[0001] This application relates to the field of electroplating wastewater treatment technology, and in particular to a method for removing copper ions from electroplating wastewater based on the efficient electroadsorption of iron-based chalcogenides. Background Technology

[0002] Industrial copper-containing wastewater mainly originates from copper mining, printed circuit board manufacturing, and electroplating industries. The wastewater from electroplating and surface treatment industries, in particular, has a more complex composition, containing not only high concentrations of heavy metal ions and various organic additives, but also high concentrations of background salt ions (such as sodium ions). + Mg 2+ K + Ca 2+ (etc.), significantly increasing the difficulty of highly selectively recovering target metals. Developing efficient and highly selective copper resource recovery technologies has significant resource and environmental value.

[0003] Traditional methods for treating electroplating wastewater mainly include chemical precipitation, ion exchange, membrane separation, and adsorption. Chemical precipitation is a widely used technology both domestically and internationally, but it is ineffective in treating low-concentration heavy metal wastewater and generates large amounts of heavy metal-containing sludge, causing secondary pollution. Ion exchange and adsorption methods are susceptible to interference from coexisting ions, resulting in decreased selectivity, and the resin / adsorbent regeneration process generates high-concentration secondary wastewater. Membrane separation technology faces problems such as membrane fouling and secondary separation of copper-containing concentrates. Furthermore, most of these methods focus on pollutant removal and are less effective in treating low-concentration Cu-containing wastewater with high salinity and multiple ion coexistence. 2+ When dealing with electroplating wastewater, there are still limitations to varying degrees, making it difficult to achieve highly selective removal of target metals in complex systems.

[0004] Capacitive deionization (CDI) is a method for ion separation that utilizes the electro-adsorption of ions in solution on an electrode surface under low voltage conditions. It offers advantages such as low energy consumption, simple operation, and no need for chemical reagents, showing promising application prospects in heavy metal wastewater treatment and resource recovery. Traditional CDI systems primarily employ carbon-based double-layer electrode materials such as activated carbon, where ion removal relies on electrostatic physical adsorption through the double layer formed at the electrode / solution interface. However, carbon-based electrodes have two inherent limitations: firstly, the adsorption capacity is limited by the physical pore volume, resulting in a relatively low theoretical upper limit; secondly, double-layer adsorption inherently lacks the ability to chemically recognize specific target ions, particularly in applications containing Na+. + Ca 2+ In complex wastewater systems with multiple coexisting ions, target heavy metal ions are easily subject to competitive adsorption interference, making selective removal difficult.

[0005] To overcome the aforementioned bottlenecks, researchers have recently introduced electrode materials exhibiting Faraday pseudocapacitive behavior into CDI systems. Faraday electrodes achieve ion storage in the bulk phase of the material through reversible redox reactions, exhibiting higher charge storage capacity and potential ion selectivity advantages compared to surface double-layer adsorption. Transition metal chalcogenides (TMCs) have attracted attention for the selective electroadsorption of heavy metal ions due to their abundant sulfur / selenium active sites, good electron transport capabilities, and relatively open ion migration channels. Existing studies have shown that, based on the hard-soft acid-base theory, the sulfur / selenium active sites on the surface of chalcogenides... 2- / Se 2- The site (soft base) can react with Cu 2+ The soft acid ions form strong coordination interactions, thereby endowing the material with the preferential adsorption capacity for target heavy metal ions.

[0006] In the field of iron-based chalcogenides, materials such as FeS2 and FeSe2 show promising applications due to their abundant iron reserves, low cost, and relatively environmentally friendly nature. However, current research on FeSe2 in the field of CDI is still lacking, and its effect on Cu during electroadsorption remains unclear. 2+ The adsorption characteristics, ion selectivity in complex multi-component systems, and adsorption mechanisms of iron-based chalcogenides lack systematic understanding. Furthermore, these compounds are prone to metal dissolution and structural degradation during electrochemical cycling, limiting their long-term operational stability.

[0007] In view of the shortcomings of the existing technology, there is an urgent need to study an electro-adsorption copper removal method that has both high adsorption capacity and high selectivity. Summary of the Invention

[0008] To address the shortcomings of the existing technologies, this application is the first to apply FeSe2 material to the field of copper removal in CDI, and modifies FeSe2 material by coating it with polypyrrole to inhibit Fe dissolution and structural degradation, thus providing an electro-adsorption copper removal method with both high adsorption capacity and high selectivity.

[0009] This application provides a method for efficiently removing copper ions from electroplating wastewater based on the electroadsorption of iron-based chalcogenides, comprising the following steps: Step A. Preparation of electrode materials (A1) Selenium powder was dissolved in hydrazine hydrate to form solution A, and ferrous sulfate heptahydrate was dissolved in deionized water to form solution B. Solution A was slowly added to solution B. After the resulting mixture underwent a hydrothermal reaction, the black precipitate was collected and then washed and dried to obtain the product FeSe2. (A2) FeSe2 was ground into powder and dispersed in deionized water. A surfactant was added and stirred until a suspension was formed. Pyrrole monomer was added to the suspension and stirred until a uniform solution was formed. Then, an oxidant was added dropwise to the suspension and stirred until the pyrrole monomer underwent polymerization. After the reaction was completed, the precipitate was separated by centrifugation, washed, and dried to obtain polypyrrole-coated FeSe2 composite material. Step B. Mix the FeSe2 prepared in step A1 or the FeSe2@PPy composite material prepared in step A2, acetylene black and polyvinylidene fluoride in N-methylpyrrolidone at a mass ratio of (7-9):1:1 to prepare a uniform slurry and coat it on the surface of a titanium plate. After drying, it is used as a cathode. Step C. Following step B, replace the FeSe2 or FeSe2@PPy composite material with activated carbon to make the anode, and then assemble the anode and cathode into a capacitor deionization device; Step D. Apply a DC voltage between the cathode and the anode to allow copper-containing electroplating wastewater to pass through a capacitor deionization device, where copper ions are electro-adsorbed and removed on the cathode surface. Step E. After adsorption saturation, the electrode is regenerated by applying a reverse voltage and short-circuiting.

[0010] Using the above technical solution, FeSe2 exhibits high theoretical capacity and certain selectivity advantages. However, experiments have shown that FeSe2 typically undergoes significant volume changes during repeated charge-discharge cycles, which may lead to structural degradation and decreased cycle performance. In CDI copper removal, electrodes often experience active component dissolution; for example, the CuFeS2 system exhibits significant Fe dissolution. To address the issues of structural instability and active component loss, this invention further employs the conductive polymer polypyrrole for surface modification to regulate the interface. Polypyrrole possesses good conductivity and film-forming properties. By constructing a coating layer on the FeSe2 material surface, interfacial charge transport can be effectively improved, and local stress caused by volume changes can be buffered to some extent, thereby inhibiting the loss of active components.

[0011] Preferably, in step A1, the molar ratio of selenium powder to ferrous sulfate heptahydrate is 2:1.

[0012] Preferably, in step A1, the hydrothermal reaction is carried out at 165-175°C for 22-26 hours.

[0013] Preferably, in step A2, the mass ratio of FeSe2 or FeSe2@PPy composite material, surfactant and pyrrole monomer is 1:0.05:(0.12-0.24).

[0014] Preferably, in step A2, the molar ratio of FeSe2 or FeSe2@PPy composite material to oxidant is 1:(1.3~2.8).

[0015] Preferably, the surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and hexadecyltrimethylammonium bromide.

[0016] Preferably, the oxidant is selected from at least one of ammonium persulfate, potassium persulfate and ferric chloride, and the concentration of the oxidant is 0.1 mol / L.

[0017] Preferably, in step D, the applied voltage is 0.4 to 1.2 V, more preferably 0.8 to 1.0 V.

[0018] Preferably, the FeSe2 has a short columnar crystal morphology with a particle size distribution of 0.5 µm to 1.0 µm.

[0019] In summary, the beneficial technical effects of this application are as follows: 1. This invention is the first to apply FeSe2 material to the field of copper removal via CDI. Short columnar FeSe2 crystals with high crystallinity and good purity were successfully synthesized via a one-step hydrothermal method. Capacitive deionization experiments were conducted using a CDI device simulation, and when Cu... 2+ The concentration is 200 mg / L -1 At that time, 329.6 mg g was achieved. -1 The adsorption capacity of FeSe2 was high; in continuous cycling tests, FeSe2 maintained a removal efficiency of up to 80% after three cycles; and in actual copper-containing electroplating wastewater, it effectively removed Cu. 2+ In the electroadsorption experiment, Cu 2+ The concentration increased from an initial 73.08 mg / L. -1 Decreased to 4.14 mg L -1 The removal rate reached 90.0%, thus proving that FeSe2 has high selectivity for removing Cu from strongly acidic actual electroplating wastewater. 2+ The ability.

[0020] 2. This invention studies the effect of FeSe2-based materials on Cu removal in CDI. 2+ The electroadsorption characteristics and Faraday reaction behavior during the process elucidate the mechanism of Cu 2+ The coordination interaction mechanism between Cu and chalcogenide active sites reveals the material realization of Cu 2+ The underlying reason for selective removal: Under cathode bias, Cu... 2+ First, Cu is enriched on the FeSe2 surface under electrostatic attraction, and then a portion of it... 2+ The reduction to Cu occurs via a pseudocapacitive reaction. +Due to the strong interaction between Cu and Se, local lattice reconstruction occurs, leading to the formation of a new Cu₂Se phase; another portion of Cu… 2+ It is then adsorbed onto the electrode surface through an electrical double layer effect.

[0021] 3. This invention addresses the potential problems of metal leaching and insufficient conductivity in the electroadsorption process of iron-based chalcogenides. It modifies FeSe2 materials by coating with polypyrrole to obtain FeSe2@PPy composite materials. Experiments were conducted to investigate the regulatory effect of polypyrrole coating on the loss of active components and structural stability. The results demonstrate that polypyrrole coating helps alleviate the Fe leaching problem of FeSe2, and Fe leaching is gradually suppressed as the coating thickness increases. This indicates that the PPy coating layer, acting as a physical barrier, can effectively reduce the direct contact between the core layer and the electrolyte and alleviate lattice strain during the electroadsorption process. Therefore, this invention has excellent industrial application prospects in the efficient treatment of heavy metal wastewater and acidic electroplating wastewater in the CDI field. Attached Figure Description

[0022] Figure 1 Figure 1 shows the morphology and crystal structure characterization of FeSe2; Figure (a) shows the scanning electron microscope and transmission electron microscope images of FeSe2, Figure (b) shows the high-resolution transmission electron microscope image of FeSe2, and Figure (ce) shows the elemental mapping of the energy dispersive X-ray spectrum of FeSe2.

[0023] Figure 2 Figure 1 shows the XRD pattern of FeSe2, as well as the N2 adsorption-desorption isotherm and pore size distribution. Figure 2(a) shows the X-ray diffraction pattern of FeSe2, and Figure 2(b) shows the N2 adsorption-desorption isotherm and pore size distribution of FeSe2.

[0024] Figure 3 Figure 1 shows the X-ray photoelectron spectrum of FeSe2; Figure (a) is the full spectrum, Figure (b) is the high-resolution XPS spectrum of Fe 2p, and Figure (c) is the high-resolution XPS spectrum of Se 3d.

[0025] Figure 4 The graph shows the variation of the FeSe2 water contact angle at different time points.

[0026] Figure 5 Figure 1 shows the electrochemical performance analysis of FeSe2. Among them, Figure (a) is the CV curve at different scan rates, Figure (b) is the specific capacitance at different scan rates, Figure (c) is the b-value analysis (based on log(i)-log(v)), Figure (d) is the contribution ratio of capacitance and diffusion control, Figure (e) is the GCD curve at different current densities, and Figure (f) is the Nyquist curve.

[0027] Figure 6Cu 2+ The standard curve graph.

[0028] Figure 7 Figure 1 shows the adsorption performance analysis of FeSe2; Figure 2(a) shows the adsorption kinetics curve and adsorption rate graph, and Figure 3(b) shows the adsorption performance analysis of FeSe2 with different Cu values. 2+ The adsorption capacity analysis diagrams at different concentrations are shown in Figure (c), which is the adsorption isotherm diagram of Langmuir and Freundlich, Figure (d) is the adsorption capacity analysis diagram at different voltages, Figure (e) is the adsorption capacity analysis diagram at different pH values, and Figure (f) is the adsorption capacity analysis diagram at different flow rates.

[0029] Figure 8 Cu in copper-containing electroplating wastewater 2+ and different ions (K) + Na + Ca 2+ Cr 3+ and Zn 2+ ) Concentration changes and removal rate before and after electro-adsorption.

[0030] Figure 9 Images show the morphology and crystal structure of the FeSe2 electrode after electroadsorption; Figures (a, c) are scanning electron microscope and transmission electron microscope images, Figure (b) is a high-resolution transmission electron microscope image, and Figure (dg) is an EDS elemental distribution map.

[0031] Figure 10 Figure 1 shows the X-ray diffraction pattern and Raman spectrum of the FeSe2 electrode after electroadsorption; Figure 2(a) shows the X-ray diffraction pattern of the FeSe2 electrode after electroadsorption, and Figure 2(b) shows the Raman spectrum of FeSe2 and the FeSe2 electrode after electroadsorption.

[0032] Figure 11 Figure 1 shows the X-ray photoelectron spectra of the FeSe2 electrode after electroadsorption; Figure 2 shows the full spectrum, Figure 3 shows the spectrum of Cu 2p, Figure 4 shows the spectrum of Se 3d, and Figure 5 shows the spectrum of Fe 2p.

[0033] Figure 12 Figure 1 shows scanning electron microscope (SEM) images of FeSe2@PPy composite materials; Figure 2(a) is an SEM image of FeSe2@PPy-50, Figure 2(b) is an SEM image of FeSe2@PPy-75, Figure 2(c) is an SEM image of FeSe2@PPy-100, and Figure 3(d) shows Cu content of different samples. 2+ Electroadsorption capacity diagram, Figure (e) shows the iron dissolution concentration of different samples.

[0034] Figure 13 FeSe2 and Cu (compare material) 2+Comparison chart of electroadsorption performance. Detailed Implementation

[0035] The present invention will be further described below with reference to specific embodiments. However, the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the methods used are conventional methods known in the art, and the consumables and reagents used are commercially available. Unless otherwise stated, the technical and scientific terms used herein have the same meaning as those familiar with the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be applied to the present invention.

[0036] The following are the calculation methods for key indicators in the example: Adsorption capacity (mg g) -1 ) Calculate using equation (2-1):

[0037] Wherein, C0 and C1 are the ion concentrations (mg / L) before and after adsorption, respectively. -1 V is the solution volume (L), and m is the mass of the active material (g).

[0038] Removal efficiency is calculated using equation (2-2):

[0039] Wherein, C0 and C1 are the ion concentrations (mg / L) before and after adsorption, respectively. -1 ).

[0040] The average adsorption rate is calculated using equation (2-3):

[0041] Wherein, C0 and C1 are the ion concentrations (mg / L) before and after adsorption, respectively. -1 V is the solution volume (L), and m is the mass of the active material (g). t is the adsorption time.

[0042] The Langmuir isothermal adsorption model is calculated using equation (2-4):

[0043] Among them, Q e To balance the adsorption capacity (mg g) -1 ), Q max Maximum adsorption capacity (mg g) -1 ), K L Langmuir isothermal adsorption constant (L mg) -1 ), Ce To balance the solution concentration (mg / L) -1 ).

[0044] The Freundlich isothermal adsorption model is calculated using equation (2-5):

[0045] Among them, Q e To balance the adsorption capacity (mg g) -1 ), K F C is the Freundlich isotherm adsorption constant. e To balance the solution concentration (mg / L) -1 ), where 1 / n is the adsorption strength coefficient.

[0046] Allocation coefficient K d (mL g) -1 ) Calculate using equation (2-6):

[0047] Wherein, C0 and C1 are the ion concentrations (mg / L) before and after adsorption, respectively. -1 V is the solution volume (mL), and m is the mass of the active material (g).

[0048] Specific capacitance C m (F g) -1 ) Calculate using equation (2-7):

[0049] Where m is the mass of the active material (g), and v is the scan rate (V s). -1 ), V = V2 - V1 is the voltage window (V), and i(V) is the response current (A).

[0050] The value of b is calculated using equation (2-8):

[0051] Where a and b are constants, and v is the scan rate (Vs). -1 ), i is the response current (A).

[0052] The ratio of capacitance control to diffusion control is calculated using equation (2-9):

[0053] Where K1 is the proportional coefficient of capacitor control (AsVt) -1 K2 is the diffusion control proportionality coefficient (As). 0.5 V -0.5 ), v is the scan rate (V s)-1 i(V) is the response current (A).

[0054] Example 1 1. Preparation of FeSe2 materials: 0.316 g of selenium powder was dissolved in 16 mL of 80% hydrazine hydrate (N₂H₄·H₂O) and sonicated for 3 minutes until completely dissolved; this solution is designated as solution A. 0.556 g of ferrous sulfate heptahydrate (FeSO₄·7H₂O) was dissolved in 44 mL of deionized water; this solution is designated as solution B. At room temperature, solution A was slowly added to solution B, and the mixture was magnetically stirred for 1 hour. The resulting mixture was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 170 °C for 24 hours. After the reaction was complete and the mixture was cooled to room temperature, the resulting black precipitate was collected and washed several times with deionized water and anhydrous ethanol. Finally, the product was vacuum dried at 60 °C for 8 hours, ground in a mortar for 10 minutes, and the FeSe₂ powder was collected for later use.

[0055] 2. Characterization of FeSe2 materials The microstructure, crystal structure, elemental composition and surface features of the sample materials were systematically characterized and analyzed by means of scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, specific surface area measurement, and water contact angle measurement.

[0056] (1) SEM and TEM micromorphology analysis The surface morphology and microstructure of the FeSe2 sample were characterized using scanning electron microscopy and transmission electron microscopy. Figure 1 As shown in (a), the material consists of short columnar particles with clear edges and smooth surfaces, exhibiting no obvious pores. The particles are randomly oriented and relatively compactly packed. Their particle size is mainly distributed between 0.5 µm and 1.0 µm, showing a relatively uniform size distribution. (High-resolution transmission electron microscopy image) Figure 1 (b) Obvious lattice fringes were observed, indicating that the material has good crystallinity. Measurements showed that the spacing of the local lattice fringes in the image was 0.177 nm, which is consistent with the (130) plane spacing of FeSe2 (PDF#04-004-2181). Energy-dispersive X-ray spectroscopy elemental mapping ( Figure 1 (ce) shows that Fe and Se elements are distributed very evenly in the material. Combined with the quantitative analysis in Table 3-1, it can be seen that the atomic percentage of Fe and Se in the material is about 29.94%:70.06%, which is close to the theoretical stoichiometric ratio of 1:2, further confirming the successful synthesis of FeSe2.

[0057] Table 1. EDS elemental analysis of FeSe2

[0058] (2) XRD crystal structure analysis The phase composition and crystallinity of FeSe2 materials were analyzed using X-ray diffraction. Figure 2 As shown in (a), the characteristic diffraction peaks at 24.1°, 31.1°, 34.8°, 36.2°, 48.2°, and 53.9° correspond to the (110), (101), (111), (120), (211), and (031) crystal planes of the Marcasite-type orthorhombic FeSe2 (PDF#04-004-2181), respectively. No diffraction peaks of elemental Fe, Se, or FeSe impurity phases were detected in the XRD pattern, indicating that the synthesized material has high phase purity and good crystallinity. The high crystallinity of FeSe2 is beneficial for constructing channels for rapid electron transport, thereby effectively improving its resistance to Cu during capacitive deionization. 2+ The adsorption kinetics performance.

[0059] (3) Specific surface area and pore size distribution analysis The pore characteristics of FeSe2 materials were analyzed using N2 adsorption-desorption isotherms. Figure 2 As shown in (b), this material exhibits type IV isothermal characteristics accompanied by a typical H3-type hysteresis loop. In the higher relative pressure region (P / P0>0.9), the adsorption capacity increases sharply without an adsorption plateau. This is likely due to the abundant slit-like interstices formed by the accumulation of FeSe2 particles. Combined with the pore size distribution curve, it can be seen that the pore sizes generated by particle accumulation are mainly distributed in the larger mesopore and macropore ranges. Although its specific surface area is relatively low (2.04 m²), it still exhibits these characteristics. 2 g -1 However, this interstitial network formed by particle accumulation can effectively promote electrolyte penetration, thereby providing Cu during the capacitor deionization process. 2+ It provides a convenient channel for rapid transmission.

[0060] (4) Analysis of valence state of XPS surface X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition and chemical valence state of FeSe2 materials. (Full spectrum) Figure 3 (a) Characteristic peaks for Fe, Se, O, and C elements were observed. The O signal detected on the sample surface is mainly attributed to surface oxidation of the material during storage. The Fe 2p high-resolution XPS spectrum is shown below. Figure 3 As shown in (b), the characteristic peaks at 706.98 eV and 719.74 eV can respectively correspond to Fe 2+ 2p 3 / 2 and 2p 1 / 2The orbitals are consistent with existing literature reports on FeSe2. The fitted peaks at 710.61 eV, 712.29 eV, and 714.20 eV are attributed to Fe. 3+ 2p 3 / 2 This can be attributed to Fe formed by slight oxidation on the material surface. 3 + Species. From Se 3d high-resolution XPS spectra ( Figure 3 (c) It can be seen that the characteristic peaks at 54.53 eV and 55.33 eV can respectively correspond to 3D 3 / 2 and 3D 5 / 2 The characteristic peak at 59.03 eV is attributed to SeO formed by oxidation on the material surface. x The peak at 53.5 eV may be related to the interaction between Fe and Se, while the peak at 56.2 eV originates from Se-Se bonds. These XPS test results further confirm the successful synthesis of FeSe2.

[0061] (5) Surface wettability analysis The wettability of the material was evaluated using a water contact angle test. Figure 4 As shown, after 3 seconds of contact with the material surface, the water contact angle of FeSe2 is 39.0°, indicating that FeSe2 possesses excellent hydrophilicity and high surface free energy. The excellent hydrophilicity of FeSe2 may be related to its surface chemical properties, particularly the presence of SeO2 on its surface. x FeO x It is an oxide species. This hydrophilicity helps the electrode surface to be fully wetted by the electrolyte, thereby reducing interfacial mass transfer resistance, which is beneficial to Cu in the CDI process. 2+ Electroadsorption and related reactions occur.

[0062] 3. Electrochemical testing and analysis of FeSe2 materials Electrochemical tests were performed using a CS350 electrochemical workstation from Wuhan KOST. A three-electrode system was used: a platinum sheet as the counter electrode and a saturated Ag / AgCl reference electrode as the reference electrode. The working electrode slurry was prepared with FeSe2, acetylene black, and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1. The prepared slurry was coated onto a 1 cm² area... 2 On the titanium plate, then in 0.1 mol L -1 Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed in a Na2SO4 (pH=8.5) solution.

[0063] The results are as follows Figure 5As shown in (a–c), the prominent redox peaks of FeSe2 in the cyclic voltammograms indicate that its behavior is mainly controlled by surface Faraday reactions. The large oxidation peak of FeSe2 may be related to Fe... 2+ To Fe 3+ The oxidation transformation is related. The weak reduction peak indicates that the reverse reaction is incomplete. With increasing scan rate, the specific capacitance of the material increases from 5 mV / s. -1 22.42 Fg -1 Decreased to 50 mV s -1 14.28 F g at that time -1 This is mainly due to the limitation of ion diffusion at high scan rates.

[0064] Further analysis using b-values ​​determined the kinetic characteristics of the reaction. b=1 indicates that the reaction is mainly controlled by pseudocapacitance, while b=0.5 indicates that the reaction is mainly controlled by diffusion. Using equation (2-8), b=0.80 was calculated, indicating that the reaction is mainly controlled by pseudocapacitance, and the kinetic behavior of FeSe2 is dominated by surface processes. The ratio of pseudocapacitance control to diffusion control was quantitatively calculated using Dunn analysis. Figure 5 As shown in (d), the proportional gain controlled by the pseudocapacitor starts from 5 mV s -1 The percentage increased from 47% to 50 mV s -1 At 74%, pseudocapacitive control gradually becomes dominant, while the proportion of diffusion control gradually decreases. This is due to the limited ion diffusion at high scan rates. The galvanostatic charge-discharge curves of FeSe2 ( Figure 5 (e) exhibits a typical asymmetric triangle and a distinct charging plateau, indicating that it possesses pseudocapacitive behavior dominated by the Faraday reaction. The electrochemical impedance spectroscopy of FeSe2 was fitted using an equivalent circuit ( Figure 5 (f)). Charge transfer resistance (R) of FeSe2 ct The impedance is relatively small, only 29.62 Ω, indicating that FeSe2 has a rapid interfacial charge transport capability. Meanwhile, the impedance curve in the low-frequency region is steep, with a slope much greater than 45°. This suggests that the system has low diffusion resistance, mainly controlled by capacitive reactions, which is consistent with CV and GCD analyses. FeSe2 exhibits good electron transport capabilities and rapid surface pseudocapacitive behavior, which contributes to improving electroadsorption capacity and adsorption rate.

[0065] Example 2 In this embodiment, a capacitive deionization experiment was conducted in a CDI device to investigate the effects of voltage, concentration, flow rate, and pH on the adsorption capacity of the electrode material, in order to evaluate the capacitive deionization performance of the FeSe2 electrode material in Example 1.

[0066] 1. Preparation of CDI device: The CDI device used in this embodiment is existing technology, mainly consisting of a pair of electrodes, an insulated flow channel, a power supply system, and an inlet / outlet water system. Wherein: Cathode preparation: FeSe2, acetylene black, and polyvinylidene fluoride (PVDF) from Example 1 were added to N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1, followed by ultrasonic treatment for 20 minutes to prepare a uniform slurry. The resulting slurry was then uniformly coated onto a 4×4 cm cathode. 2 The titanium plates were dried in a 60 °C oven for later use.

[0067] Cathode preparation: The FeSe2 material was replaced with activated carbon, and the remaining steps were the same as those for the cathode.

[0068] The dried cathode and anode were assembled in a CDI device, and the flow rate and operating voltage of the peristaltic pump were set to conduct an electroadsorption experiment.

[0069] 2. Evaluation of the capacitive deionization performance of the FeSe2 electrode 50 mL of Cu-containing solution was pumped using a peristaltic pump. 2+ The solution is pumped into the CDI unit, where a DC power supply provides voltage, and the Cu in the water is adsorbed by cathodic electroadsorption. 2+ During the experiment, small amounts of solution were periodically sampled and Cu was analyzed at 461 nm using a UV-Vis spectrophotometer. 2+ The concentration.

[0070] Test method: First, prepare a stock solution of a certain concentration, then take an appropriate amount of the stock solution and dilute it to 0.2, 0.4, 0.8, 1.6 and 2.0 mg / L, respectively. -1 Cu was determined by sodium diethyldithiocarbamate spectrophotometry. 2+ The concentration was measured at a wavelength of 461 nm. Each sample group underwent three parallel tests to plot a standard curve (e.g., ...). Figure 6 (As shown). After linear fitting, the linear regression equation of the standard curve is y = 0.1612x - 3×10 5 Correlation coefficient R 2 = 0.9997, indicating that Cu in this concentration range 2 + There is a good linear relationship between concentration and absorbance.

[0071] This embodiment investigated the effects of voltage, concentration, flow rate, and pH on the adsorption capacity of the material. The specific parameters of the CDI device were set as follows: operating voltage: 0, 0.4, 0.8, 1.0, 1.2, 1.4 V; initial concentration: 25, 50, 100, 200, 400, 800 mg / L. -1Flow rates of 5, 10, 15, 20, and 25 mL / min were used. -1 pH was set to 1, 2, 3, 4 and unadjusted (pH=4.86).

[0072] First, by recording the Cu in the solution at different adsorption times... 2+ By varying the concentration, the adsorption kinetics curve of the material can be obtained, such as... Figure 7 As shown in (a), the system exhibits a relatively fast adsorption rate in the initial stage of adsorption, reaching 2.37 mg g. -1 min -1 As the reaction proceeds, the adsorption rate gradually decreases due to the gradual saturation of active sites and the increase in diffusion resistance. The system reaches adsorption equilibrium after 12 hours of adsorption.

[0073] Figure 7 (b) The effect of initial concentration on adsorption performance was investigated. With Cu 2+ The initial concentration was 12.5 mg L. -1 Increase to 800 mg L -1 Its equilibrium adsorption capacity is 22.43 mg g. -1 Significantly increased to 732.30 mg g -1 This is attributed to the strong mass transfer driving force generated under high concentration gradients. The adsorption isotherm data were fitted and analyzed using the Langmuir and Freundlich models. Figure 7 (c)) The results show that the Langmuir model has a good fit (R0). 2 = 0.979) is higher than the Freundlich model (R 2 =0.928). This indicates that Cu 2+ Adsorption on the FeSe2 surface mainly occurs at a limited number of active sites. Based on the Langmuir model, Cu... 2+ The theoretical maximum adsorption capacity is 838.75 mg g. -1 .

[0074] Figure 7 (d) The effect of operating voltage on electroadsorption capacity was investigated. At 0 V (open circuit), only weak physical adsorption (3.21 mg g) was observed. -1 When the applied voltage is increased from 0.4 V to 1.0 V, Cu 2+ The adsorption capacity is 25.99 mg g. -1 Significantly increased to 663.18 mg g -1 This phenomenon can be attributed to the increased voltage enhancing the effect on Cu. 2+ The electrostatic attraction of Cu promotes the production of more Cu 2+The copper migrates to the electrode surface and achieves interface trapping. It is worth noting that numerous CDI studies have shown that when the applied voltage exceeds 1.2 V, Faraday side reactions are easily induced, including copper deposition and water splitting reactions such as oxygen evolution and hydrogen peroxide generation. These side reactions can lead to electrode surface contamination, pore blockage, and further degrade electrode performance. In this experiment, obvious brownish-red metallic deposits were also observed on the electrode surface at 1.2 V and 1.4 V, presumably due to copper precipitation. Considering energy consumption and stability, 1.0 V was selected as the standard operating voltage for this experiment.

[0075] Figure 7 (e) The pH adaptability of the system was investigated. The system remained stable over a wide range, with a significant decrease in electroadsorption capacity only observed in strongly acidic environments (pH 1–2). This is mainly attributed to high H+ concentrations. + With Cu 2+ Competitive adsorption occurred at the active site.

[0076] Figure 7 (f) The effect of different flow rates on Cu was investigated. 2+ The effect of flow rate on the electroadsorption capacity of ions. Within the experimental range investigated, the flow rate generally had a small effect on the electroadsorption capacity. The effect was only noticeable at flow rates of 20–25 mL / min. -1 At high flow rates, the electroadsorption capacity decreases slightly, which can be attributed to the fact that high flow rates shorten the residence time of the solute on the material surface.

[0077] Example 3 This embodiment uses the CDI device from Example 2 to evaluate the electroadsorption of Cu by the FeSe2 electrode material from Example 1 using actual industrial copper-containing electroplating wastewater (diluted 10 times, pH approximately 2.16). 2+ The ability.

[0078] The copper-containing electroplating wastewater sample was taken from an electroplating industrial park in Nansha, Guangzhou. Figure 8 As shown, copper-containing electroplating wastewater contains multiple coexisting cations (K... + 12.94, Na + 29.67, Ca 2+ 11.41, Cr 3+ 0.34, Zn 2+ 10.84 mg L -1 In actual electroplating wastewater, copper ions may exist in the form of copper-ammonia complexes. To avoid changes in the form of copper ions during the experiment, this embodiment performed preliminary denitrification treatment on the electroplating wastewater before testing. Water quality testing showed that the COD value of the actual electroplating wastewater after denitrification treatment was 0.593 g / L. -1 The ammonia nitrogen value was 22.74 mg / L. -1The pH value is 1.50.

[0079] Adsorption tests were conducted under an applied voltage of 1 V, and each experiment was performed in triplicate.

[0080] Experimental results show that, despite the low initial pH, FeSe2 still has an effect on Cu 2+ It exhibits excellent capture capabilities. 2+ The concentration increased from an initial 73.08 mg / L. -1 Decreased to 4.14 mg L -1 The removal rate reached 90.0%. In contrast, the concentrations of other cations did not change significantly before and after electroadsorption. This result demonstrates that FeSe2 exhibits high selectivity for removing Cu from strongly acidic real-world electroplating wastewater. 2+ The ability.

[0081] Electroadsorption mechanism analysis 1. The morphology and crystal structure of the electroadsorption samples were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 9 (a)). The results show that the electroadsorbed material retains its original short columnar morphology, indicating that its structural framework has good stability. High-resolution transmission electron microscopy (HRTEM) analysis shows ( Figure 9 (b) Stripes with lattice spacings of 0.33 nm and 0.36 nm appeared on the material surface, corresponding to the (111) crystal plane of Cu₂Se and the (110) crystal plane of FeSe₂, respectively, preliminarily confirming that a phase transformation occurred during the electroadsorption process. Energy Dispersive Spectroscopy (EDS) Figure 9 (dg) The results show that Cu is uniformly distributed in the bulk phase of the particles, rather than being limited to local areas, suggesting that Cu has been embedded in the crystal lattice.

[0082] 2. XRD patterns ( Figure 10 (a) Further confirmation revealed the presence of distinct Cu₂Se characteristic peaks after electroadsorption, corresponding to the Cu₂Se standard card (PDF 97-063-3479), thus confirming the formation of the new phase. Furthermore, Raman spectroscopy was used to analyze the changes in chemical bonds before and after adsorption. Figure 10 (b)). FeSe2 at 210 cm -1 and 268 cm -1 The distinct Raman peaks appearing at the points can be attributed to the A atoms of the Se-Se bonds. g Vibration and B 1g vibration

[131] After electroadsorption, the intensity of the Raman peak associated with the Se–Se bond significantly decreased, indicating a local structural rearrangement in the material. This change may be related to Cu. 2+This is related to the interaction with FeSe2. Simultaneously, the Raman peak of FeSe2 exhibits a blue shift after electroadsorption, possibly related to Cu. 2+ It is related to the local compressive strain caused by embedding.

[0083] The elemental valence states and chemical environment of the FeSe2 electrode surface after electroadsorption were investigated using XPS. In the high-resolution Cu 2p spectrum (… Figure 11 (b) The characteristic peaks at 932.7 eV and 952.48 eV correspond to Cu, respectively. + 2p 3 / 2 and 2p 1 / 2 The peaks at 933.7 eV and 954.0 eV are attributed to Cu orbitals, while the peaks at 933.7 eV and 954.0 eV are attributed to Cu orbitals. 2+ 2p 3 / 2 and 2p 1 / 2 Track. Cu + The presence of the signal indicates that some Cu is electroadsorbed. 2+ It is reduced to Cu via a pseudocapacitive reaction. + And Cu 2+ The presence of Cu indicates that there is still some Cu. 2+ Electrostatic adsorption occurs on the electrode surface. In the Fe 2p spectrum ( Figure 11 In (d), compared to the original electrode, the Fe in the adsorbed electrode is... 3+ The increased contribution suggests that Fe may have participated in Cu. 2+ Electron transfer during the trapping process. In Se 3d spectra ( Figure 11 In (c)), the peaks at 54.17 eV and 54.97 eV correspond to Se 3d, respectively. 5 / 2 and Se 3d 3 / 2 Compared to the original sample, the Se 3d peak shifted by 0.82 eV towards higher binding energies, indicating a change in the local chemical environment of Se, which may be related to Cu. 2+ It is related to the local lattice strain caused by embedding.

[0084] Based on the above characterization analysis, it can be seen that the FeSe2 electrode is effective for Cu... 2+ Electroadsorption follows a dual mechanism of Faraday reaction and electrobilayer adsorption. Under negative bias at the cathode, Cu... 2+ First, Cu is enriched on the electrode surface under electrostatic attraction, and then a portion of it... 2+ It is reduced to Cu through a pseudocapacitive process. + Driven by the strong chemical affinity between Se and Cu, a new Cu₂Se phase is eventually formed; the remaining Cu... 2+ It is then adsorbed onto the electrode surface through an electrical double layer effect.

[0085] Example 4 Preparation of FeSe2@PPy composite material: 0.4 g of FeSe2 powder from Example 1 was dispersed in 200 mL of deionized water and sonicated for 20 minutes. Then, 20 mg of sodium dodecyl sulfate was added, and the mixture was magnetically stirred for 20 minutes. Pyrrole monomers (50, 75, and 100 μL) were then added to the suspension, and magnetic stirring continued for 1 hour. 20 mL of 0.1 mol / L... -1 Ammonium persulfate was added dropwise to the above suspension, and magnetic stirring was continued for 4 hours to initiate the polymerization of pyrrole monomers. After the reaction was completed, the precipitate was separated by centrifugation and collected, washed several times with ethanol and deionized water, and then vacuum dried at 60 °C for 8 hours. The obtained samples were named FeSe2@PPy-50, FeSe2@PPy-75, and FeSe2@PPy-100 according to the amount of pyrrole monomer added.

[0086] Microscopic morphology analysis via SEM, such as Figure 12 The SEM images (ac) show that a continuous PPy layer was successfully coated on the FeSe2 surface, and the thickness of the coating layer increased with the increase of pyrrole dosage. Specifically, when the pyrrole dosage was 50, 75, and 100 µL, the corresponding coating layer thicknesses were 34.9, 50.5, and 78.6 nm, respectively.

[0087] Example 5 This embodiment selects samples FeSe2@PPy-50, FeSe2@PPy-75, and FeSe2@PPy-100 from Example 4 to experiment on the surface modification of polypyrrole and its effect on inhibiting Fe leaching. The experiment uses the CDI apparatus and testing method from Example 2, with the difference that the FeSe2 material is replaced with FeSe2@PPy-50, FeSe2@PPy-75, and FeSe2@PPy-100, respectively. 50 mL of Cu-containing... 2+ The solution is pumped into the CDI unit, where a DC power supply provides voltage, and the Cu in the water is adsorbed by cathodic electroadsorption. 2+ .

[0088] Experimental conditions: Applied voltage 1 V, Cu 2+ The concentration is 400 mg / L -1 Flow rate 15 ml / min -1 pH was not adjusted; each experiment was performed in triplicate.

[0089] To evaluate the effect of PPy shell thickness on Fe dissolution, a comparative CDI test was performed, and the Fe dissolution concentration in the treated solution was measured. Figure 12 As shown in (d, e), the Fe dissolution concentration of the original FeSe2 was 67.40 mg L. -1In comparison, the Fe dissolution concentrations of FeSe2@PPy-50, FeSe2@PPy-75, and FeSe2@PPy-100 were 56.13, 33.96, and 23.95 mg / L, respectively. -1 The results showed that Fe dissolution was gradually suppressed with increasing coating thickness. This indicates that the PPy coating, acting as a physical barrier, can effectively reduce the direct contact between the core layer and the electrolyte, and alleviate lattice strain during electroadsorption. However, with increasing coating thickness, Cu... 2+ The electroadsorption capacity gradually decreased, which was due to the reduction of active site exposure caused by PPy coating.

[0090] Comparative Example To further illustrate the role of FeSe2 in Cu 2+ The performance of the electroadsorption process was compared and analyzed with other representative materials reported in relevant literature (ZnO-PC, Fe-NC, CuS, CuS@CuSe, Fe-Co-C, FeSe2@NSC, etc.). Figure 13 As shown, in the initial Cu 2+ Under conditions of similar or comparable concentrations and applied voltages, FeSe2 exhibits a higher electroadsorption capacity. When the initial Cu... 2+ The concentration is approximately 400 mg / L -1 At this time, the electroadsorption capacity of FeSe2 can reach approximately 663.18 mg g. -1 The concentration was significantly higher than that of known materials such as ZnO-PC, Fe-NC, CuS, and Fe-Co-C. The initial concentration was further increased to approximately 800 mg / L. -1 At that time, the electroadsorption capacity of FeSe2 can still reach approximately 732.30 mg g. -1 The value is higher than that of materials such as CuS@CuSe and CuSe, indicating that it performs well in high concentrations of Cu. 2 + It still has a strong ability to capture metal ions in the wastewater system.

[0091] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for efficiently removing copper ions from electroplating wastewater based on the electroadsorption of iron-based chalcogenides, characterized in that: Includes the following steps: Step A. Preparation of electrode materials (A1) Selenium powder was dissolved in hydrazine hydrate to form solution A, and ferrous sulfate heptahydrate was dissolved in deionized water to form solution B. Solution A was slowly added to solution B. After the resulting mixture underwent a hydrothermal reaction, the black precipitate was collected and then washed and dried to obtain the product FeSe2. (A2) FeSe2 was ground into powder and dispersed in deionized water. A surfactant was added and stirred until a suspension was formed. Pyrrole monomer was added to the suspension and stirred until a uniform solution was formed. Then, an oxidant was added dropwise to the suspension and stirred until the pyrrole monomer underwent polymerization. After the reaction was completed, the precipitate was collected by centrifugation, washed, and dried to obtain polypyrrole-coated FeSe2@PPy composite material. Step B. Mix the FeSe2 prepared in step A1 or the FeSe2@PPy composite material prepared in step A2, acetylene black and polyvinylidene fluoride in N-methylpyrrolidone at a mass ratio of (7-9):1:1 to prepare a uniform slurry and coat it on the surface of a titanium plate. After drying, it is used as a cathode. Step C. Following step B, replace the FeSe2 or FeSe2@PPy composite material with activated carbon to fabricate the anode, and then assemble the anode and cathode into a capacitor deionization device; Step D. Apply a DC voltage between the cathode and the anode to allow copper-containing electroplating wastewater to pass through a capacitor deionization device, where copper ions are electro-adsorbed and removed on the cathode surface. Step E. After adsorption saturation, the electrode is regenerated by short-circuiting or applying a reverse voltage.

2. The method for removing copper ions from electroplating wastewater based on the efficient electroadsorption of iron-based chalcogenides according to claim 1, characterized in that: In step A1, the molar ratio of selenium powder to ferrous sulfate heptahydrate is 2:

1.

3. The method for removing copper ions from electroplating wastewater based on the efficient electroadsorption of iron-based chalcogenides according to claim 1, characterized in that: In step A1, the hydrothermal reaction is carried out at 165-175°C for 22-26 hours.

4. The method for removing copper ions from electroplating wastewater based on the efficient electroadsorption of iron-based chalcogenides according to claim 1, characterized in that: In step A2, the mass ratio of FeSe2 or FeSe2@PPy composite material, surfactant and pyrrole monomer is 1:0.05:(0.12-0.24).

5. The method for removing copper ions from electroplating wastewater based on the efficient electroadsorption of iron-based chalcogenides according to claim 1, characterized in that: In step A2, the molar ratio of FeSe2 or FeSe2@PPy composite material to oxidant is 1: (1.3~2.8).

6. The method for removing copper ions from electroplating wastewater based on the efficient electroadsorption of iron-based chalcogenides according to claim 1, characterized in that: The surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and hexadecyltrimethylammonium bromide.

7. The method for efficiently removing copper ions from electroplating wastewater based on the electroadsorption of iron-based chalcogenides according to claim 1 or 6, characterized in that: The oxidant is selected from at least one of ammonium persulfate, potassium persulfate, and ferric chloride, and the concentration of the oxidant is 0.1 mol / L.

8. The method for removing copper ions from electroplating wastewater based on the efficient electroadsorption of iron-based chalcogenides according to claim 1, characterized in that: In step D, a voltage of 0.4–1.2 V is applied.

9. The method for removing copper ions from electroplating wastewater based on the efficient electroadsorption of iron-based chalcogenides according to claim 1, characterized in that: The FeSe2 exhibits a short columnar crystal morphology with a particle size distribution of 0.5 µm to 1.0 µm.

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