Treatment system and method for recovering high-value metals from acidic industrial wastewater

Abstract

The present invention relates to a treatment system and method for recovering high-value metals from acidic industrial wastewater. The system comprises at least one high-value metal recovery unit comprising first housings, a first liquid inlet and a first liquid outlet, which are arranged on side walls of each first housing, and a plurality of first electrode plate sets arranged inside each first housing, wherein at least one aeration guide pipe having holes is laid at the bottom of each first housing, and the high-value metals are recovered from the wastewater by applying a current density to the first electrode plate sets; and an iron metal recovery unit comprising a second housing, a second liquid inlet and a second liquid outlet, which are arranged on side walls of the second housing, a discharging port arranged on a bottom wall of the second housing, and a plurality of second electrode plate sets arranged in the second housing, wherein the metal iron is recovered from the wastewater by applying a current density to the second electrode plate sets. By regulating and controlling the electrode potential of each unit, various high-value metals are recovered in different recovery units.

Description

A system and method for recovering and treating high-value metals from acidic industrial wastewater. Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a system and method for recovering and treating high-value metals from acidic industrial wastewater. Background Technology

[0002] With the rapid development of industrialization, industries such as mining, dyeing, and electroplating have grown rapidly, and the resulting environmental problems have attracted increasing attention. Industrial production inevitably generates large amounts of industrial wastewater. This wastewater is typically highly acidic, thus absorbing large amounts of metal ions such as iron, copper, cadmium, nickel, and zinc. Simultaneously, due to the necessity of the production process, the addition of various chemicals results in a certain amount of organic matter in the wastewater, making its composition increasingly complex. Long-term industrial activities have led to the generation of highly acidic, complex-compositioned, and difficult-to-treat acidic industrial wastewater, becoming a serious water environment problem worldwide. Currently, methods for treating acidic industrial wastewater include physicochemical and microbiological methods. The most widely used method is lime neutralization, which involves adding lime and other substances to neutralize acidic mining wastewater and precipitate metal ions. This method has advantages such as simplicity and ease of operation, but it generates a large amount of metal sludge that requires further treatment. This results in insurmountable drawbacks such as high chemical consumption, susceptibility to secondary pollution, and waste of valuable metal resources. Therefore, how to develop a new type of system for the recovery and treatment of various high-value metals in acidic industrial wastewater is an urgent problem that needs to be solved.

[0003] Summary of the Invention

[0004] To address the technical problems existing in the prior art, the first objective of this invention is to provide a system for the recovery and treatment of high-value metals in acidic industrial wastewater, comprising a high-value metal recovery unit and an iron metal recovery unit. By adjusting the electrode potential within each unit, this system can achieve efficient recovery of various high-value metals in different recovery units. This not only optimizes resource recovery efficiency but also reduces the chemical consumption and sludge production associated with traditional lime neutralization methods, effectively lowering the risk of secondary pollution.

[0005] The second objective of this invention is to provide a method for a high-value metal recovery system for acidic industrial wastewater, wherein different current densities are applied in the high-value metal recovery unit and the iron metal recovery unit to grade and recover different types of high-value metals from the wastewater.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A system for recovering high-value metals from acidic industrial wastewater includes: at least one high-value metal recovery unit, comprising a first shell with an open top, a first inlet for receiving wastewater and a first outlet for discharging wastewater after high-value metal recovery, disposed on the side wall of the first shell, and a plurality of first electrode plate assemblies disposed within the first shell and insulated from its inner wall; at least one perforated aeration conduit laid along the length of the bottom of the first shell, the aeration conduit being located below and corresponding to the first electrode plate assemblies, and high-value metals in the wastewater being recovered by applying a current density to the first electrode plate assemblies; and an iron metal recovery unit located downstream of the high-value metal recovery unit, comprising a second shell with an open top, a second inlet for receiving wastewater and a second outlet for discharging wastewater after high-value metal recovery, disposed on the side wall of the second shell, an outlet for discharging iron metal, and a plurality of second electrode plate assemblies disposed within the second shell and insulated from its inner wall, and iron metals in the wastewater being recovered by applying a current density to the second electrode plate assemblies.

[0008] Furthermore, there are two high-value metal recovery units, one of which is used to recover metal ions of high-value metals with metal activity lower than that of hydrogen ions, and the other is used to recover metal ions of high-value metals with metal activity higher than that of hydrogen ions.

[0009] Furthermore, in one of the high-value metal recycling units, the current density applied to its first electrode plate assembly is 1-4 mA / cm². 2 In another high-value metal recycling unit, the current density applied to its first electrode plate group is 5-10 mA / cm². 2 .

[0010] Furthermore, an inlet baffle and an overflow plate are sequentially arranged along the length of the first housing. The inlet baffle and the overflow plate divide the first housing into an inlet chamber, a recovery chamber, and an overflow chamber. The first inlet is located on the side of the inlet chamber. The inlet baffle is set on the two side walls at the top of the first housing and extends downward to a certain height, so that a communication port that allows wastewater to pass is formed between the inlet baffle and the bottom wall of the first housing. The first outlet is located on the side of the overflow chamber. The overflow plate is set on the bottom wall of the first housing and extends upward to a certain height, so that an overflow port that allows wastewater to overflow is formed at the top of the overflow plate.

[0011] Furthermore, the first electrode plate assembly includes multiple anode plates and multiple cathode plates. The multiple anode plates are connected together by wire harnesses, and the multiple cathode plates are connected together by wire harnesses. The anode plates and cathode plates are arranged alternately within the first housing and located below the liquid surface. The length direction of the anode plates and cathode plates is parallel to the length direction of the first housing.

[0012] Furthermore, the current density applied to the second electrode plate assembly in the iron metal recovery unit is greater than or equal to 20 mA / cm². 2 .

[0013] Furthermore, it also includes a flotation unit located downstream of the iron metal recovery unit. The flotation unit is used to receive iron metal from the discharge port and separate the iron metal from the wastewater by adding flotation reagents and aeration flotation to recover the iron metal.

[0014] Furthermore, it also includes a concentration and conditioning unit located downstream of the iron metal recovery unit. The concentration and conditioning unit includes a conditioning tank and a concentration sedimentation tank connected in series. The conditioning tank adds chemicals to condition the wastewater from the second discharge port to modify the wastewater. The concentration sedimentation tank uses gravity to concentrate the modified wastewater from the conditioning tank to separate the concentrated sludge by sedimentation.

[0015] Furthermore, it also includes a sludge dewatering unit located downstream of the thickening and conditioning unit. The sludge dewatering unit dewaters the thickened sludge from upstream to reduce the moisture content of the thickened sludge.

[0016] The method using the above-mentioned system for recovering and treating high-value metals from acidic industrial wastewater includes the following steps:

[0017] Wastewater is transported to a high-value metal recovery unit. In the high-value metal recovery unit, the wastewater comes into contact with the first electrode plate group. The wastewater is aerated through the aeration pipe, and at the same time, a current density is applied to the first electrode plate group to make the high-value metals adhere to the first electrode plate group, so as to recover the high-value metals in the wastewater.

[0018] The wastewater after recovering high-value metals is transported to the iron metal recovery unit. In the iron metal recovery unit, the wastewater comes into contact with the second electrode plate group, and a current density is applied to the second electrode plate group to cause the iron metal in the wastewater to settle, thereby recovering the iron metal in the wastewater.

[0019] The present invention has the following advantages:

[0020] This invention relates to a system for recovering high-value metals from acidic industrial wastewater, comprising multi-stage metal recovery units. By precisely controlling the current density applied to the electrode plates in different recovery units, the system achieves efficient recovery of various high-value metals while simultaneously utilizing an electrochemical oxidation process to effectively remove potential organic matter from the wastewater. Since the metal recovery rate reaches over 80% after treatment by the multi-stage metal recovery units, the system significantly reduces the consumption of chemical reagents in subsequent wastewater treatment processes, thereby significantly improving economic efficiency and reducing operating costs. Furthermore, the unique design of the electrode plates in the metal recovery units, parallel to the wastewater flow direction, effectively reduces the accumulation of alkali produced at the cathode in the solution, thus avoiding the formation of hydroxides and further improving the recovery efficiency of high-value elemental metals.

[0021] Compared to the traditional lime neutralization method, the metal recovery method of this invention is based on electrochemical treatment technology, featuring low energy consumption, low material consumption, easy assembly, and modularity. Utilizing the fundamental principle of simultaneous electrochemical anodic oxidation and cathodic reduction processes, and through precise control of electrode potential, it achieves the graded recovery of multiple high-value metals such as iron, copper, cadmium, and nickel under acidic conditions, while simultaneously removing organic matter. During the electrochemical treatment process, metals are recovered in the form of iron minerals and elemental metals. This not only effectively reduces the consumption of chemical reagents required for subsequent alkali precipitation but also reduces the yield of metal sludge, thereby significantly reducing the risk of secondary pollution. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the process for the recovery and treatment of high-value metals in acidic industrial wastewater according to the present invention.

[0023] Figure 2 is a three-dimensional structural schematic diagram of the high-value metal recycling unit of the present invention.

[0024] Figure 3 is a perspective sectional view of the high-value metal recycling unit of the present invention.

[0025] Figure 4 is a three-dimensional structural schematic diagram of the first electrode plate assembly and aeration conduit of the present invention.

[0026] Figure 5 is a graph showing the concentrations of copper and cadmium in the wastewater from two high-value metal recovery units and one iron metal recovery unit in Embodiment 1 of the present invention.

[0027] Figure 6 is a graph showing the iron concentration in the wastewater of two high-value metal recovery units and one iron metal recovery unit in Embodiment 1 of the present invention.

[0028] Figure 7 shows the XRD characterization diagrams of copper, cadmium, and iron minerals recovered by two high-value metal recovery units and one iron metal recovery unit in Embodiment 1 of the present invention.

[0029] Figure 8 is a graph showing the total organic carbon removal rate in wastewater at different times for the iron metal recovery unit of Embodiment 1 of the present invention.

[0030] Figure 9 is a comparison chart of the amount of alkaline agent added in Example 1 and Comparative Example 1 of the present invention.

[0031] Figure 10 shows the XRD characterization of the precipitate after adding alkali to Comparative Example 1.

[0032] Wherein, 1 is a high-value metal recovery unit, 1a is one of the high-value metal recovery units, 1b is another high-value metal recovery unit, 101 is the first housing, 101a is the first liquid inlet, 101b is the first liquid outlet, 102 is the first electrode plate assembly, 102a is the cathode plate, 102b is the anode plate, 102c is the wiring harness, 102d is the transverse support rod, 103 is the aeration conduit, 103a is the aeration hole, 104 is the water inlet baffle, 10 4a is the connecting port, 105 is the overflow plate, 105a is the overflow port, 106 is the liquid inlet chamber, 107 is the recovery chamber, 108 is the overflow chamber, 2 is the iron metal recovery unit, 201 is the second shell, 201a is the second liquid inlet, 201b is the second liquid outlet, 201c is the discharge port, 202 is the second electrode plate group, 3 is the flotation unit, 4 is the concentration and conditioning unit, 401 is the conditioning tank, 402 is the concentration sedimentation tank, and 5 is the sludge dewatering unit. Detailed Implementation

[0033] The following description is merely illustrative in nature and is in no way intended to limit the invention, its application, or use. It will be further understood that the terms “comprising” and / or “including” as used herein specify the presence of the mentioned features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element, component, and / or portion is referred to as “connected to another element, component, and / or portion,” it may be directly connected to another element, component, and / or portion, or there may be intermediate elements. It will be understood that although the terms “first,” “second,” etc., may be used herein to describe various elements, components, and / or portions, these elements, components, and / or portions should not be limited by these terms. These terms are used only to distinguish one element, component, or portion from another element, component, or portion. Therefore, the first element, component, or part discussed below may be referred to as the second element, component, or part without departing from the teachings of the invention. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with their meanings in the relevant field and / or the context of this specification, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0034] It should be understood that, for clarity, the accompanying drawings are not drawn to scale, and the same or similar reference numerals indicate the same or similar parts or components. Furthermore, it should be understood that any embodiments described in this application and the technical features they include can be combined with each other.

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] As shown in Figures 1-4, a system for recovering high-value metals from acidic industrial wastewater includes: at least one high-value metal recovery unit, which comprises a first shell with an open top, a first inlet for receiving wastewater and a first outlet for discharging wastewater after high-value metal recovery, the first inlet and the first outlet being respectively located on two opposite side walls of the first shell, and a plurality of first electrode plate assemblies disposed within the first shell and insulated from its inner wall. At least one perforated aeration conduit is laid along the length of the first shell at its bottom, located below and corresponding to the first electrode plate assemblies, and the aeration conduit is activated by applying a current density... The system utilizes a first electrode plate assembly to recover high-value metals from wastewater. A downstream iron metal recovery unit comprises a second shell with an open top, a second inlet for receiving wastewater and a second outlet for discharging the recovered wastewater, both located on opposite side walls of the second shell. An outlet for discharging iron metal is located on the bottom wall of the second shell. Multiple second electrode plate assemblies, insulated and supported within the second shell, are also included. A current density is applied to the second electrode plate assemblies to recover iron metals from the wastewater. Specifically, the iron metal recovery unit recovers divalent and trivalent iron. The first shell is rectangular, with X representing its length and Y representing its width, and wastewater flows along its length. The acidic industrial wastewater is an acidic water body containing a large amount of metal ions and a certain amount of organic matter, including but not limited to acidic mining wastewater, acidic dyeing and printing wastewater, and acidic electroplating wastewater.

[0037] The system includes two high-value metal recovery units connected in series. One unit recovers metal ions with reactivity lower than hydrogen ions, i.e., easily reducible metals are recovered first. The other unit recovers metal ions with reactivity higher than hydrogen ions, i.e., difficult-to-reducible metals are recovered secondarily. Metal ions with reactivity lower than hydrogen ions include, but are not limited to, gold, silver, and copper; metal ions with reactivity higher than hydrogen ions include, but are not limited to, cadmium, cobalt, and nickel. The number of high-value metal recovery units can be one, three, five, etc., with each unit connected in series. Different current densities can be adjusted as needed to recover different high-value metals.

[0038] The working principle of the high-value metal recovery unit and the iron metal recovery unit in this system is as follows: By adjusting the current density of the electrode plate groups in the high-value metal recovery unit and the iron metal recovery unit, a lower current density is applied to the first electrode plate group of one of the high-value metal recovery units. This is used to recover easily reducible metals in the wastewater, i.e., metal ions with a lower reactivity than hydrogen ion reduction can be directly reduced to elemental metals on the cathode plate for recovery. A medium current density is applied to the first electrode plate group of the other high-value metal recovery unit. This is used to recover difficult-to-reducible metals in the wastewater, causing a certain degree of hydrogen evolution reaction on the cathode plate. Under the alkalinity generated by the hydrogen evolution reaction, hydroxylation products of difficult-to-reducible metal ions are generated, and further reduced to elemental metals on the cathode under the action of an electric field for recovery. After the metal ions on the first electrode plate group are mass-transferred to the cathode, they will generate elemental metals under the action of cathode electrons and adhere to the cathode. Since the generated elemental metals have high mechanical strength, they can be directly scraped off and recovered using a scraper. A high current density is applied to the second electrode plate assembly of the iron metal recovery unit. Under this high current density, the anodic oxidation water generates a large number of strong oxidizing species (O2 and ·OH, etc.), which can rapidly oxidize Fe(II) to Fe(III). Furthermore, the cathode undergoes a vigorous hydrogen evolution reaction under the action of high current density, generating a large number of hydroxide ions. The anions in the wastewater react with the hydroxide ions to generate iron minerals (Schwarzschildite, tetragonal lepidocrocite, etc.), thus realizing the recovery of iron resources. At the same time, the generated strong oxidizing species can simultaneously mineralize the organic matter in the wastewater during this process, with total organic carbon being removed in the form of CO2, achieving the electrochemical recovery of multiple metals and the removal of organic matter. After passing through a multi-stage electrochemical metal recovery process, the wastewater enters the concentration and conditioning unit. Since a large number of metal ions have already been recovered in the upstream recovery unit, the main function of the concentration and conditioning unit is to precipitate the metal ions in the wastewater that were not completely recovered, so that they can meet the industrial wastewater discharge standards.

[0039] In one of the high-value metal recycling units, the current density applied to its first electrode plate assembly is 1-4 mA / cm².2 In another high-value metal recycling unit, the current density applied to its first electrode plate group is 5-10 mA / cm². 2 The current density applied to the second electrode plate assembly in the iron metal recovery unit is greater than or equal to 20 mA / cm². 2 By precisely controlling the current density applied to the electrode plates in different recovery units, this system achieves efficient recovery of various high-value metals. Besides current density, other parameters include temperature, current, and processing time. The temperature is ambient, the current is applied using a constant current method, and the processing time ranges from 1 to 6 hours.

[0040] As shown in Figure 2-4, an inlet baffle and an overflow plate are sequentially arranged along the length of the first shell. These baffles divide the first shell into an inlet chamber, a recovery chamber, and an overflow chamber. The first inlet is located on the side of the inlet chamber. The inlet baffle is installed on the two side walls at the top of the first shell and extends downwards to a certain height, forming a communication port between the inlet baffle and the bottom wall of the first shell, allowing wastewater to pass through. The first outlet is located on the side of the overflow chamber. The overflow plate is installed on the bottom wall of the first shell and extends upwards to a certain height, forming an overflow port at the top of the overflow plate, allowing wastewater to overflow. The overflow port has a triangular overflow weir. The flow path of wastewater within the first shell is as follows: wastewater enters the inlet chamber through the first inlet port on the side wall of the inlet chamber. Due to the obstruction of the inlet baffle, the wastewater is forced to flow downwards and can only enter the recovery chamber through the connecting port at the lower end of the inlet baffle. The wastewater contacts and reacts with the first electrode plate assembly in the recovery chamber. The water flows tangentially between the cathode and anode plates. Simultaneously, the aeration pipe causes the metal precipitates settled at the bottom of the recovery chamber to tumble and rise. After the reaction is completed, the wastewater overflows into the overflow chamber through the overflow port at the upper end of the overflow plate and is finally discharged from the first drain port located at the lower part of the side wall of the overflow chamber. By setting the inlet baffle and overflow plate to change the flow path of wastewater in the high-value metal recovery unit, the reaction time between the wastewater and the first electrode plate assembly is increased, thereby improving the recovery efficiency. More importantly, this setting can also prevent the formation of stagnant water on the same side of the inlet and outlet, creating a buffer zone inside the first shell to prevent excessive hydraulic impact and excessive suspended solids at the front end from affecting the smooth progress of electrochemical recovery.

[0041] As shown in Figure 2-4, the first electrode plate assembly includes multiple anode plates and multiple cathode plates. The anode plates and cathode plates are connected together by wire harnesses. The anode and cathode plates are arranged alternately within the first housing and below the liquid surface, with their lengths parallel to the length of the first housing. The second electrode plate assembly also includes multiple anode plates and multiple cathode plates. The anode plates and cathode plates are connected together by wire harnesses. The anode and cathode plates are arranged alternately within the second housing and below the liquid surface, with their lengths parallel to the length of the second housing. The wire harnesses are connected to an external power source, which applies current and voltage to the multiple cathode and anode plates respectively. In this design, the length directions of the anode and cathode plates are parallel to the length direction of the second shell, meaning that the length directions of the anode and cathode plates are parallel to the flow direction of the wastewater. Most existing electrode plates are placed vertically in the flow direction of the wastewater to enhance mass transfer and ensure rapid electrode reaction. However, this process inevitably generates high local alkalinity near the cathode. This alkalinity causes metal ions to preferentially form metal hydroxides rather than elemental metals. The parallel arrangement of the length directions of the anode and cathode plates with the length direction of the second shell is to disperse the current density and ensure the recovery of higher-value elemental metals, thereby improving the economic efficiency of the electrochemical reaction process.

[0042] The high-value metal recovery unit comprises two first electrode plate groups, arranged sequentially along the length of the first shell. The aeration conduit has an inverted T-shape structure, including a horizontal conduit below the two first electrode plate groups and a vertical conduit inserted in the middle of the horizontal conduit. The horizontal conduit has aeration holes facing the first electrode plate groups. The vertical conduit is located between the two first electrode plate groups. External air enters through the vertical conduit, is distributed to the horizontal conduit, and finally sprays out through the aeration holes towards the first electrode plate groups. The number of horizontal conduits can be configured as needed; for example, one horizontal conduit can be installed at the bottom of each electrode plate, with the aeration holes facing the electrode plate. Multiple horizontal conduits are connected to one vertical conduit. The purpose of the aeration conduit in the high-value metal recovery unit is to prevent the metal elements from settling at the bottom of the first shell by aeration and stirring up and agitating the wastewater sediment, allowing more metal elements to contact and adhere to the first electrode plate groups, thus improving recovery efficiency. The iron metal recovery unit also has two second electrode plate groups, with a structure and arrangement similar to the high-value metal recovery unit, which will not be described further here. The iron metal recovery unit does not require aeration pipes, as it uses gravity settling to deposit iron ore to the bottom of the second shell, from which it is discharged to the next processing step. The absence of aeration ensures better settling.

[0043] The anode materials used in the anode plate include, but are not limited to, IrO2-RuO2 / Ti electrodes, PbO2 / Ti electrodes, and BDD electrodes. The cathode materials used in the cathode plate include, but are not limited to, stainless steel, iron, copper, nickel, titanium, and other metals or metal compounds. By selecting appropriate anode and cathode materials and configuring an advanced electrochemical oxidation pathway to simultaneously remove organic matter from acidic industrial wastewater, controllable resource recovery and simultaneous pollutant treatment of acidic industrial wastewater can be achieved.

[0044] As shown in Figure 2-4, the anode plate and cathode plate are fixed together by transverse support rods. The two ends of the transverse support rods are respectively fixed to the inner wall of the first housing to provide insulating support for the anode plate and cathode plate. The transverse support rods are made of insulating material to prevent the first housing from conducting electricity and ensure the safe use of the equipment. In this embodiment, each first electrode plate group is equipped with four transverse support rods, which are fixed laterally at the four corners of the first electrode plate group. These rods serve to position the distance between the anode plate and cathode plate, and also to fix the position of the first electrode plate group relative to the first housing. The second electrode plate group is also equipped with transverse support rods, with a similar structure to the first electrode plate group, and will not be described further here.

[0045] As shown in Figure 1, the system also includes a flotation unit located downstream of the iron metal recovery unit. This flotation unit receives iron metal from the discharge port and recovers the iron metal by separating it from wastewater through the addition of flotation reagents and aeration flotation. The working principle of the flotation unit is to separate solid particles by adjusting buoyancy and bubble adhesion. First, the iron minerals are crushed and ground to an appropriate particle size, then mixed with water and flotation reagents to adjust the solid-liquid interface properties and buoyancy. In the flotation cell, bubbles are generated using mechanical agitation or nozzles. These bubbles selectively adhere to the useful mineral particles and float to the surface, forming a foam layer. These foam layers contain iron minerals and are subsequently discharged for further processing.

[0046] As shown in Figure 1, the system also includes a concentration and conditioning unit located downstream of the iron metal recovery unit. This unit comprises a conditioning tank and a concentration sedimentation tank connected in series. The conditioning tank includes a stirrer inside, a dosing device at the top, and an online pH monitor. The concentration sedimentation tank has a bucket-type structure with a sludge discharge port at the bottom. The conditioning tank adds chemicals to the wastewater from the second discharge port to modify it. The concentration sedimentation tank then uses gravity to concentrate the modified wastewater from the conditioning tank, separating the concentrated sludge. The chemicals added to the conditioning tank are alkalizing agents, including but not limited to NaOH, CaO, and Na₂S, to further raise the pH to above neutral, allowing the remaining iron ions in the wastewater to precipitate in the concentration sedimentation tank. The resulting concentrated sludge enters the sludge dewatering unit through the sludge discharge port at the bottom of the sedimentation tank.

[0047] As shown in Figure 1, the system also includes a sludge dewatering unit located downstream of the thickening and conditioning unit. The sludge dewatering unit dewaters the thickened sludge from upstream to reduce its moisture content. The sludge dewatering unit is a plate and frame filter press, which dewaters the thickened sludge to obtain dewatered sludge, which is then subjected to subsequent harmless treatment and resource recovery.

[0048] Pumps for transporting wastewater are installed on the pipelines upstream of the high-value metal recovery unit, between the high-value metal recovery unit and the iron metal recovery unit, between the iron metal recovery unit and the concentration and conditioning unit, and between the iron metal recovery unit and the flotation unit.

[0049] The method of the present invention for the recovery and treatment system of high-value metals in acidic industrial wastewater includes the following steps:

[0050] Wastewater is transported to a high-value metal recovery unit. In the high-value metal recovery unit, the wastewater comes into contact with the first electrode plate group. The wastewater is aerated through the aeration pipe, and at the same time, a current density is applied to the first electrode plate group to make the high-value metals adhere to the first electrode plate group, so as to recover the high-value metals in the wastewater.

[0051] The wastewater after recovering high-value metals is transported to the iron metal recovery unit. In the iron metal recovery unit, the wastewater comes into contact with the second electrode plate group, and a current density is applied to the second electrode plate group to cause the iron metal in the wastewater to settle, thereby recovering the iron metal in the wastewater.

[0052] The wastewater containing iron metal is transported to the flotation unit through the discharge port. The iron metal is separated from the wastewater by adding flotation reagents and aeration flotation to recover the iron metal.

[0053] Wastewater discharged from the iron metal recovery unit is transported to the concentration and conditioning unit through the second discharge port. The conditioning tank in the concentration and conditioning unit adds chemicals to condition the wastewater from the second discharge port to modify the wastewater. The concentration sedimentation tank uses gravity to concentrate the modified wastewater from the conditioning tank to separate the concentrated sludge.

[0054] The concentrated sludge is transported to the sludge dewatering unit to dewater it and reduce its moisture content.

[0055] Example 1

[0056] Taking acidic mine wastewater with a pH of 2.7 as an example, this system was used to recover copper, cadmium, and iron while simultaneously removing a small amount of organic matter. This embodiment is configured with two high-value metal recovery units arranged in series and one iron metal recovery unit. Downstream of the iron metal recovery unit, a thickening and conditioning unit and a sludge dewatering unit are respectively configured. One high-value metal recovery unit is used to recover copper, the other for cadmium, and the iron metal recovery unit for iron. Two sets of first electrode plates are configured, each consisting of five electrode plates: two cathode plates and three anode plates. Two sets of second electrode plates are also configured, each consisting of five electrode plates: two cathode plates and three anode plates. The current density applied to the first electrode plate set in one of the high-value metal recovery units is 1 mA / cm². 2 In another high-value metal recycling unit, the current density applied to the first electrode plate assembly is 5 mA / cm². 2 The current density applied to the second electrode plate assembly in the iron metal recycling unit is 20 mA / cm². 2 .

[0057] After metal recovery through two high-value metal recovery units and one iron metal recovery unit, the acidic mine wastewater enters the concentration and conditioning unit. CaO (5% by mass) is added to raise the pH to 13, and the remaining metal ions are then precipitated by gravity sedimentation. The total amount of 5% CaO added is recorded. Test water samples are taken from the inlet and outlet of the high-value metal recovery unit to test the concentrations of Cu(II), Cd(II), and total iron in the wastewater.

[0058] The methods for testing Cu(II) and Cd(II) concentrations are based on the Atomic Absorption Spectrophotometric Method for the Determination of Copper, Zinc, Lead and Cadmium in Water (GB 7475-1987), and the methods for testing total iron concentrations are based on the Spectrophotometric Method for the Determination of Iron in Water (HJ / T 345-2007).

[0059] Figure 5 shows the concentration values ​​of copper and cadmium in the wastewater from the two high-value metal recovery units and one iron metal recovery unit in this embodiment. Figure 6 shows the concentration values ​​of iron in the wastewater from the two high-value metal recovery units and one iron metal recovery unit in this embodiment. It should be noted that the influent values ​​in Figures 5 and 6 refer to the metal concentration values ​​when the wastewater first enters one of the high-value metal recovery units; the first-stage effluent values ​​refer to the metal concentration values ​​when the wastewater exits one of the high-value metal recovery units; the second-stage effluent values ​​refer to the metal concentration values ​​when the wastewater exits the other high-value metal recovery unit; the third-stage effluent values ​​refer to the metal concentration values ​​when the wastewater exits the iron metal recovery unit; and the sedimentation effluent values ​​refer to the metal concentration values ​​of the wastewater discharged after gravity settling in the concentration and conditioning unit. As can be seen from Figure 5, the high-value metal recovery units and the iron metal recovery unit can achieve good graded recovery of metal ions in acidic mine wastewater with a pH of 2.7. In one of the high-value metal recovery units, the Cu(II) recovery rate reaches over 99%, while the Cd(II) and total iron concentrations remain essentially unchanged. After the wastewater enters another high-value metal recovery unit, a Cd(II) recovery rate of over 90% can be achieved. As shown in Figure 6, the total iron concentration of the wastewater only decreases slightly in the two high-value metal recovery units, without affecting the recovery of Cu(II) and Cd(II). The iron metal recovery unit finally achieves a total iron ore recovery of over 50%, and the remaining metal ions are completely removed after alkali precipitation in the concentration and conditioning unit.

[0060] Figure 7 shows the XRD characterization diagrams of copper, cadmium, and iron minerals recovered by the two high-value metal recovery units and one iron metal recovery unit in this embodiment. As can be seen from Figure 7, the XRD characterization diagrams show that the recovered materials in the three-stage recovery unit are pure elemental copper, pure elemental cadmium, and pure Schiele minerals, without other metal contamination peaks, indicating that the separation effect of the three-stage recovery unit is significant, demonstrating the feasibility of multi-stage metal recovery applications based on electrochemistry.

[0061] Figure 8 shows the total organic carbon removal rate of the wastewater by the iron metal recovery unit in this embodiment at different times. As can be seen from Figure 8, due to the high current density applied in the iron metal recovery unit and the residence time of 2 hours, more than 60% of the total organic carbon in the acidic mining wastewater can be removed.

[0062] Comparative Example 1

[0063] Comparative Example 1: Acidic mine wastewater with a pH of 2.7 was treated by lime neutralization. 5% CaO was added to the acidic mine wastewater with a pH of 2.7 until the pH reached 13. The amount of 5% CaO added was recorded. After sedimentation, a water sample was taken, and the concentrations of Cu(II), Cd(II), and total iron were tested.

[0064] Figure 9 shows a comparison of the amount of alkaline reagent added in Example 1 and Comparative Example 1 of the present invention. As can be seen from Figure 9, Example 1 achieved the recovery of most metal ions through two high-value metal recovery units and one iron metal recovery unit before proceeding to alkali precipitation, while Comparative Example 1 precipitated the metals directly through alkali addition. In comparison, the 5% CaO dosage in Comparative Example 1 was significantly higher than that in Example 1, by approximately 61%.

[0065] Figure 10 shows the XRD characterization of the precipitate after adding alkali in Comparative Example 1. As can be seen from Figure 10, the precipitate obtained in Comparative Example 1 is a multi-metallic iron sludge, exhibiting amorphous peaks without other elemental metal peaks. Furthermore, no metal ions were detected in the wastewater, proving that low-content precious metal ions are removed from the wastewater as hydroxides or adsorbed onto iron minerals, and high-value metals cannot be separated. It is noteworthy that, as shown in Figure 7, the samples obtained in Example 1 all contained high-value metal components, demonstrating a significantly better recovery effect than Comparative Example 1.

[0066] In summary, the high-value metal recovery system for acidic industrial wastewater of the present invention is equipped with multi-stage metal recovery units. By precisely controlling the current density applied to the electrode plate groups in different recovery units, the system achieves efficient recovery of various high-value metals and simultaneously utilizes an electrochemical oxidation process to effectively remove potential organic matter from the wastewater. Since the metal recovery rate of the wastewater reaches over 80% after treatment by the multi-stage metal recovery units, the consumption of chemical reagents in subsequent wastewater treatment processes is significantly reduced, resulting in significantly improved economic efficiency and lower operating costs. Furthermore, the unique design of the electrode plates in the metal recovery units, parallel to the wastewater flow direction, effectively reduces the accumulation of cathode alkali in the solution, thereby avoiding the formation of hydroxides and further improving the recovery efficiency of high-value elemental metals. Compared to the traditional lime neutralization method, the metal recovery method of the present invention, based on electrochemical treatment technology, features low energy consumption, low material consumption, ease of assembly, and modularity. Based on the fundamental principle of simultaneous electrochemical anodic oxidation and cathodic reduction, and through precise control of electrode potential, the graded recovery of various high-value metals such as iron, copper, cadmium, and nickel was achieved under acidic conditions, while simultaneously removing organic matter. During the electrochemical treatment process, the metals are recovered in the form of iron minerals and elemental metals. This not only effectively reduces the consumption of chemical reagents required for subsequent alkali precipitation but also lowers the yield of metal sludge, thereby significantly reducing the risk of secondary pollution.

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A system for recovering and treating high-value metals from acidic industrial wastewater, characterized in that, include: At least one high-value metal recovery unit for recovering high-value metals, the high-value metal recovery unit includes a first shell with an open top, a first inlet for receiving wastewater and a first outlet for discharging wastewater after high-value metal recovery, disposed on the side wall of the first shell, and a plurality of first electrode plate assemblies disposed inside the first shell and insulated and supported therewith, and at least one perforated aeration conduit laid along its length at the bottom of the first shell, the aeration conduit being located below and corresponding to the first electrode plate assemblies, and high-value metals in wastewater being recovered by applying a current density to the first electrode plate assemblies; The iron metal recovery unit located downstream of the high-value metal recovery unit includes a second shell with an open top, a second inlet for receiving wastewater and a second outlet for discharging wastewater after high-value metal recovery, an outlet for discharging iron metal from the bottom wall of the second shell, and multiple second electrode plate groups disposed inside the second shell and insulated from and supported by the inner wall therein. Iron metal in the wastewater is recovered by applying a current density to the second electrode plate groups.

2. The system for recovering and treating high-value metals from acidic industrial wastewater according to claim 1, characterized in that, There are two high-value metal recovery units. One high-value metal recovery unit is used to recover metal ions of high-value metals with metal activity lower than that of hydrogen ions, and the other high-value metal recovery unit is used to recover metal ions of high-value metals with metal activity higher than that of hydrogen ions.

3. The system for recovering and treating high-value metals from acidic industrial wastewater according to claim 2, characterized in that, In one of the high-value metal recycling units, the current density applied to its first electrode plate assembly is 1-4 mA / cm². 2 In another high-value metal recycling unit, the current density applied to its first electrode plate group is 5-10 mA / cm². 2 .

4. The system for recovering and treating high-value metals from acidic industrial wastewater according to claim 1, characterized in that, An inlet baffle and an overflow plate are sequentially arranged along the length of the first housing. The inlet baffle and the overflow plate divide the first housing into an inlet chamber, a recovery chamber, and an overflow chamber. The first inlet is located on the side of the inlet chamber. The inlet baffle is set on the two side walls of the top of the first housing and extends downward to a certain height, so that a communication port that allows wastewater to pass is formed between the inlet baffle and the bottom wall of the first housing. The first outlet is located on the side of the overflow chamber. The overflow plate is set on the bottom wall of the first housing and extends upward to a certain height, so that an overflow port that allows wastewater to overflow is formed at the top of the overflow plate.

5. The system for recovering and treating high-value metals from acidic industrial wastewater according to claim 1, characterized in that, The first electrode plate group includes multiple anode plates and multiple cathode plates. The multiple anode plates are connected together by wire harnesses, and the multiple cathode plates are connected together by wire harnesses. The anode plates and cathode plates are arranged alternately in the first housing and located below the liquid surface. The length direction of the anode plates and cathode plates is parallel to the length direction of the first housing.

6. The system for recovering and treating high-value metals from acidic industrial wastewater according to claim 1, characterized in that, The current density applied to the second electrode plate assembly in the iron metal recovery unit is greater than or equal to 20 mA / cm². 2 .

7. The system for recovering and treating high-value metals from acidic industrial wastewater according to claim 1, characterized in that, It also includes a flotation unit located downstream of the iron metal recovery unit. The flotation unit is used to receive iron metal from the discharge port and to separate the iron metal from the wastewater by adding flotation reagents and aeration flotation to recover the iron metal.

8. A system for recovering and treating high-value metals from acidic industrial wastewater according to claim 1, characterized in that, It also includes a concentration and conditioning unit located downstream of the iron metal recovery unit. The concentration and conditioning unit includes a conditioning tank and a concentration sedimentation tank connected in series. The conditioning tank adds chemicals to condition the wastewater from the second discharge port to modify the wastewater. The concentration sedimentation tank uses gravity to concentrate the modified wastewater from the conditioning tank to separate the concentrated sludge.

9. A system for recovering and treating high-value metals from acidic industrial wastewater according to claim 8, characterized in that, It also includes a sludge dewatering unit located downstream of the thickening and conditioning unit. The sludge dewatering unit dewaters the thickened sludge from upstream to reduce the moisture content of the thickened sludge.

10. A method for recovering and treating high-value metals from acidic industrial wastewater according to any one of the preceding claims, characterized in that, The method includes the following steps: Wastewater is transported to a high-value metal recovery unit. In the high-value metal recovery unit, the wastewater comes into contact with the first electrode plate group. The wastewater is aerated through the aeration pipe, and at the same time, a current density is applied to the first electrode plate group to make the high-value metals adhere to the first electrode plate group, so as to recover the high-value metals in the wastewater. The wastewater after recovering high-value metals is transported to the iron metal recovery unit. In the iron metal recovery unit, the wastewater comes into contact with the second electrode plate group, and a current density is applied to the second electrode plate group to cause the iron metal in the wastewater to settle, thereby recovering the iron metal in the wastewater.

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