Treatment method of heavy metal wastewater

Abstract

The invention provides a treatment method of heavy metal wastewater, and belongs to the technical field of wastewater treatment. The method comprises the following steps: adding a calcium silicate material into wastewater containing heavy metal ions, and introducing gas containing CO2 to obtain a mixture; and carrying out solid-liquid separation on the mixture to obtain a purified liquid and a precipitate. A calcium silicate material with high carbon mineralization activity is adopted as a main raw material, and carbon mineralization reaction of calcium silicate minerals is induced by introducing CO2 gas into the heavy metal wastewater, so that heavy metal ions are dissolved in a main product (calcium carbonate) of the carbon mineralization reaction, and the purposes of removing the heavy metal ions in the wastewater and solidifying the heavy metal ions are achieved. Compared with the prior art, the method is simple and efficient, can achieve efficient solidification of heavy metal ions under the condition of extremely low pH, has extremely low heavy metal dissolution risk, and meanwhile achieves co-treatment of CO2.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a method for treating heavy metal wastewater. Background Technology

[0002] Mining, lithium battery production, and other processes generate large amounts of wastewater, which mainly contains Pb. 2+ Cd 2+ Cu 2 + Ni 2+ Fe 3+ As 3+ It contains heavy metal ions and has a high acidity. If the wastewater is not treated, it can easily cause pollution and damage to the ecological environment.

[0003] However, traditional heavy metal solidification technologies (such as membrane adsorption, electrochemical, and physical adsorption) generally fail or experience a sharp decline in performance under highly acidic conditions, resulting in poor treatment effects of these methods on the aforementioned high-acidity wastewater. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a method for treating heavy metal wastewater, aiming to provide a wastewater treatment method with good treatment effect on high acidity wastewater.

[0005] This application provides a method for treating heavy metal wastewater, including the following steps:

[0006] Calcium silicate material is added to wastewater containing heavy metal ions, and CO2 gas is introduced to obtain a mixture; The mixture is separated into solid and liquid components to obtain a purified liquid and a precipitate.

[0007] Optionally, in some embodiments, the calcium silicate material includes at least one of γ-dicalcium silicate, β-dicalcium silicate, tricalcium silicate, monocalcium silicate, and industrial waste containing calcium silicate mineral phase, wherein the mass percentage of the calcium silicate mineral phase in the industrial waste is greater than or equal to 60%.

[0008] Optionally, in some embodiments, 1 to 10 g of the calcium silicate material is added for every 100 mL of the wastewater.

[0009] Optionally, in some embodiments, the CO2-containing gas is introduced for a time greater than or equal to 1 hour.

[0010] Optionally, in some embodiments, the volume percentage of CO2 in the CO2-containing gas is 40-95%.

[0011] Optionally, in some embodiments, the flow rate of the CO2-containing gas is 150~500 lpm.

[0012] Optionally, in some embodiments, the pH of the wastewater is 0.5 to 7.

[0013] Optionally, in some embodiments, the concentration of heavy metal ions in the wastewater is 100~3000 mg / L.

[0014] Optionally, in some embodiments, the heavy metal ions include Pb. 2+ Cd 2+ Cu 2+ Ni 2+ Fe 3+ As 3+ At least one of them.

[0015] Optionally, in some embodiments, after the step of separating the mixture into a purified liquid and a precipitate, the method further includes: pressing the precipitate into a mold for recycling.

[0016] The technical solution proposed in this application has the following beneficial effects: In this application, calcium silicate material with high carbon mineralization activity is used as the main raw material. CO2 gas is introduced into the heavy metal wastewater to induce a carbon mineralization reaction in the calcium silicate minerals, causing heavy metal ions to be dissolved in the main product of the carbon mineralization reaction (calcium carbonate). This achieves the purpose of removing heavy metal ions from the wastewater and solidifying them. Compared with existing technologies, this invention is simple and efficient, can achieve highly efficient solidification of heavy metal ions under extremely low pH conditions, has a very low risk of heavy metal leaching, and simultaneously achieves synergistic CO2 treatment.

[0017] The above description of the present invention is merely an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are described below. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0019] Figure 1 This is a schematic flowchart of a method for treating heavy metal wastewater according to an embodiment of this application. Detailed Implementation

[0020] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0022] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0023] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the embodiments of this application, the term "at least one" refers to one or more, "more than one" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces). "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0026] For wastewater rich in heavy metal ions, existing technologies typically employ methods such as chemical precipitation, membrane adsorption, and physical or chemical adsorption. Membrane adsorption and physical or chemical adsorption purification methods involve providing or preparing materials capable of adsorbing heavy metal ions, such as adsorption membranes or gel materials, and then adsorbing the heavy metals primarily through physical or chemical adsorption. Because this method relies on the adsorption performance of the material and its main mechanism of action is based on the interaction between active groups, it is easily affected by the pH of the wastewater in practice and cannot be fully effective in strongly acidic environments. Chemical precipitation is not sensitive to pH changes but produces a large amount of hydroxide sludge, which requires safe disposal; otherwise, there is a high risk of leaching.

[0027] Therefore, this application proposes a method for treating heavy metal wastewater. Please refer to the embodiments below. Figure 1 The treatment method for heavy metal wastewater includes the following steps: S10: Calcium silicate material is added to wastewater containing heavy metal ions, and CO2 gas is introduced to obtain a mixture.

[0028] S20, the mixture is separated into solid and liquid phases to obtain purified liquid and precipitate.

[0029] In this technical solution, calcium silicate with high carbon mineralization activity is used as the main raw material. CO2 is introduced into an aqueous environment containing heavy metal ions and calcium silicate, allowing the heavy metal ions to participate in the reaction of calcium silicate with CO2 to form calcium carbonate and silica gel phase. In this way, the heavy metal ions directly participate in crystal nucleation and growth, thereby achieving lattice solidification and heavy metal ion solidification. This allows the heavy metal ions to enter calcium carbonate, occupy lattice vacancies, and be separated into the solid phase product (i.e., the precipitate in step S20) mainly through solid solution. This not only significantly reduces the concentration of heavy metal ions in the purified liquid but also effectively removes heavy metals. This method effectively utilizes the properties of ions and avoids secondary dissolution of heavy metal ions, resulting in excellent treatment performance. Furthermore, it primarily employs solid solution as the treatment method and enhances gas-liquid mass transfer through direct CO2 introduction, making it less susceptible to the pH of the wastewater. Even under strongly acidic conditions, it can still achieve efficient solidification of heavy metal ions, thus making it suitable for wastewater treatment across a wider pH range. In addition, the method achieves synergistic CO2 solidification during the heavy metal solidification process, enabling the reuse of CO2-rich waste gas in some applications, resulting in green carbon emissions. Moreover, this method does not produce any harmful byproducts that pose a risk of secondary pollution and require secondary safety treatment.

[0030] The method of this invention is applicable to the treatment of any wastewater containing heavy metal ions, and the types of heavy metal ions are not limited. Specifically, in some embodiments, the heavy metal ions may include, but are not limited to, Pb. 2+ Cd 2+ Cu 2+ Ni 2+ Fe 3+ As 3+ At least one of them.

[0031] In some embodiments, the concentration of heavy metal ions in the wastewater is 100~3000 mg / L; for example, it can be 100 mg / L, 200 mg / L, 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, or any value between any two of the above. This invention does not limit the concentration of heavy metal ions in the wastewater, and the method of this invention is effective for wastewater of any concentration. However, preferably, the method of this invention has the best solidification effect when the concentration of heavy metal ions in the wastewater is 100~3000 mg / L.

[0032] In some embodiments, the pH of the wastewater is 0.5 to 7; for example, it can be 0.5, 1, 1.5, 2, 3, 4, 5, 6, 7, or any two of the above values. The method of the present invention is applicable to wastewater with a wide pH range, has a broad range of applications, and does not require pre-treatment with acids or alkalis when treating such wastewater, thus reducing treatment steps, the use of acid and alkali materials, lowering costs, and improving treatment efficiency. Preferably, the method of the present invention is particularly suitable for strongly acidic wastewater, such as wastewater with a pH of 0.5 to 2; specifically, it can be directly used for the treatment of wastewater from mines, battery factories, etc.

[0033] In step S10, the calcium silicate material may include, but is not limited to, at least one of γ-dicalcium silicate, β-dicalcium silicate, tricalcium silicate, monocalcium silicate, and industrial waste containing calcium silicate mineral phases. In the industrial waste, the mass percentage of the calcium silicate mineral phase is greater than or equal to 60 wt%. The industrial waste may be steel slag. The above materials have high carbon mineralization activity and good reactivity. If industrial waste is used as the main raw material, it can also open up a way for resource reuse of industrial waste, resulting in good economic benefits.

[0034] In some embodiments, the dosage of calcium silicate material can meet the following conditions: 1-10g of calcium silicate material is added per 100mL of wastewater, for example, 1g, 2g, 3g, 4g, 5g, 6g, 7g, 8g, 9g, 10g of calcium silicate material, or any value between any two of the above, are added per 100mL of wastewater. Controlling the amount of calcium silicate material added within the above range can effectively remove and solidify heavy metal ions in the wastewater.

[0035] The CO2-containing gas can be CO2-rich industrial waste gas or gas from commercially available CO2 cylinders.

[0036] The CO2-containing gas is introduced for a duration of 1 hour or more. Controlling the gas introduction time to meet this condition ensures a complete reaction and effectively removes and solidifies heavy metal ions in the wastewater.

[0037] In the CO2-containing gas, the volume percentage of CO2 is 40-95%; for example, it can be 40%, 50%, 60%, 70%, 80%, 90%, 95%, or any value between two of the above. Controlling the gas flow rate within the above range helps to improve the carbon mineralization reaction rate and effect, thereby helping to improve the solidification rate of heavy metal ions.

[0038] The flow rate of the CO2-containing gas is 150-500 lpm; for example, it can be 150 lpm, 200 lpm, 250 lpm, 300 lpm, 350 lpm, 400 lpm, 450 lpm, 500 lpm, or any value between two of the above. Controlling the gas flow rate within the above range helps to improve the rate and effect of the carbon mineralization reaction, thereby helping to improve the solidification rate of heavy metal ions.

[0039] In step S20, solid-liquid separation can be performed using any commonly used separation method, including but not limited to filtration, vacuum filtration, pressure filtration, centrifugation, etc.

[0040] The precipitate is a solidified carbon mineralization reaction product containing heavy metal ions and may contain some unreacted calcium silicate material, which can be used for pressing, landfilling, etc. Based on this, in some embodiments, after step S20, the following step may be included: S30, pressing the precipitate into shape and then recycling it.

[0041] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Embodiments Where specific techniques or conditions are not specified, the procedures shall be carried out in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0042] Example 1 S1: Dissolve lead nitrate in water and adjust the pH with hydrochloric acid to obtain pH=1, Pb 2+ A heavy metal solution with a concentration of 1000 mg / L.

[0043] S2: Following a ratio of 1g:100mL for calcium silicate material to heavy metal solution, an appropriate amount of γ-type dicalcium silicate was mixed with the heavy metal solution. CO2 gas with a concentration of 95% was then introduced at a flow rate of 350 lpm for 5 days to obtain the final mixture. (Experiments showed that when the reaction time was greater than 5 days, the heavy metal curing rate did not increase significantly; therefore, the following examples and comparative examples all use 5 days as the reaction time.) S3: Filter the mixture by pressure to obtain purified liquid and precipitate.

[0044] Example 2 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S1, lead nitrate is replaced with copper nitrate, resulting in pH=1 and Cu. 2+ A heavy metal solution with a concentration of 1000 mg / L; In S2, the calcium silicate material is monocalcium silicate.

[0045] Apart from that, all other steps and conditions remain unchanged.

[0046] Example 3 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S1, lead nitrate is replaced with a mixture of lead nitrate, copper nitrate, and cadmium nitrate, resulting in a solution with pH=1 and containing 300 mg / L Pb. 2+ 300mg / L Cu 2+ 300mg / L Cd 2+ Heavy metal solutions; In S2, the flow rate of CO2-containing gas is changed to 400 lpm.

[0047] Apart from that, all other steps and conditions remain unchanged.

[0048] Example 4 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S1, the pH of the heavy metal solution is 3, and Pb 2+ The concentration is 2000 mg / L; In S2, the ratio of calcium silicate material to heavy metal solution is 10g:100mL, and the calcium silicate material is industrial steel slag (the mass percentage of calcium silicate mineral phase is 60%).

[0049] Apart from that, all other steps and conditions remain unchanged.

[0050] Example 5 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S2, the ratio of calcium silicate material to heavy metal solution is 10g:100mL.

[0051] Apart from that, all other steps and conditions remain unchanged.

[0052] Example 6 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S1, the pH of the heavy metal solution is 5, and Pb... 2+ The concentration is 1000 mg / L.

[0053] Apart from that, all other steps and conditions remain unchanged.

[0054] Example 7 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S1, the pH of the heavy metal solution is 0.5, and Pb... 2+The concentration is 1000 mg / L.

[0055] Apart from that, all other steps and conditions remain unchanged.

[0056] Example 8 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S2, the concentration of CO2 gas is 50%.

[0057] Apart from that, all other steps and conditions remain unchanged.

[0058] Example 9 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S2, the flow rate of CO2-containing gas is changed to 200 lpm.

[0059] Apart from that, all other steps and conditions remain unchanged.

[0060] Example 10 The scheme in this embodiment is basically the same as that in embodiment 1, except that in this embodiment: In S2, the flow rate of CO2-containing gas is changed to 500 lpm.

[0061] Apart from that, all other steps and conditions remain unchanged.

[0062] Comparative Example 1 A slurry was prepared by mixing calcium silicate material and deionized water at a water-to-solid mass ratio of 0.15. The calcium silicate material was γ-type dicalcium silicate.

[0063] The slurry was placed in a closed carbonization reactor, and a CO2-containing gas with a relative partial pressure of 0.3 MPa and a CO2 concentration of 95% was introduced into the reactor and maintained for 24 hours to obtain carbonized calcium silicate material (hereinafter referred to as "TG material"). XRD analysis showed that the phase composition of this TG material was approximately: 42 wt% calcium carbonate, 28 wt% silica gel, and 30 wt% unreacted dicalcium γ-silicate.

[0064] Prepare the pH=1, Pb obtained in Example 1 2+ A heavy metal solution with a concentration of 1000 mg / L.

[0065] The TG material was dried, and then the TG material was added to the heavy metal solution at a ratio of 1g TG material to 100mL heavy metal solution. After standing for 5 days, the solution was filtered to obtain a purified solution with a pH of 1.36 and a precipitate.

[0066] Comparative Example 2 This comparative example scheme is basically the same as that of Comparative Example 1, except that this comparative example uses pH=0.5 and Pb obtained in Example 7. 2+ A heavy metal solution with a concentration of 1000 mg / L was reacted to produce a purified solution with a pH of 0.75 and a precipitate.

[0067] Experimental Example (1) The concentration of residual heavy metal ions and the solidification rate of heavy metal ions in the purified solutions prepared in each embodiment and comparative example were detected by the following methods: 1. Concentration of heavy metal ions: Collect an equal volume of purified solution, filter it through a 0.22 μm membrane filter, then dilute and acidify it with 5% dilute HNO3 to obtain the detection solution. The detection solution is analyzed using inductively coupled plasma optical emission spectrometry / mass spectrometry (ICP-OES, Prodigy 7), and the test result is recorded as C. 处理后 .

[0068] 2. Heavy metal ion curing rate: The curing rate is calculated according to the following formula: Curing rate = (C 处理前 -C 处理后 )×100% / C 处理前 .

[0069] It is understandable that for Example 3, which contains multiple heavy metal ions, the curing rate is the sum of the curing rates of the three heavy metal ions.

[0070] Table 1

[0071] As can be seen, the solidification rates of the treatment methods in each embodiment are all high, exceeding 90%, and the heavy metal ion content in the purified liquid after treatment is extremely low. This indicates that the method of this application has a highly efficient heavy metal ion removal effect and can solidify and separate heavy metal ions in a solid solution form, with a low risk of secondary leaching. Furthermore, referring to the detection data of Examples 1, 4, 6, and 7, it can be found that even for wastewater with extremely low pH, such as the wastewater with pH=0.5 in Example 7, this method can achieve a heavy metal solidification rate of 90.5%, and the concentration of heavy metal ions in the treated wastewater can be reduced to below 100 mg / L, far below the initial level. This indicates that the method of this invention is applicable to wastewater with a wide range of pH levels and also has excellent treatment effects on strongly acidic wastewater.

[0072] Furthermore, comparing Example 1 with Comparative Examples 1 and 2, it can be seen that Comparative Examples 1 and 2 have almost no effect on heavy metal treatment for wastewater with pH values ​​of 0.5 and 1, respectively. The concentration of heavy metals in the treated wastewater remains at a high level, and they do not have the effect of solidifying heavy metal ions. This may be because Comparative Examples 1 and 2 first react calcium silicate material with CO2 to form calcium carbonate and silica gel, and then use the product as a heavy metal adsorbent to adsorb heavy metals. Essentially, they still remove heavy metal ions through physical or chemical adsorption, so they require a high degree of acidity or alkalinity of the wastewater and are prone to failure in a strongly acidic environment. At the same time, since heavy metal ions are removed in the form of adsorption, secondary dissolution is prone to occur during the reaction process, which also weakens the treatment effect to some extent.

[0073] (2) Take 1g of the precipitate obtained in Example 1, dry it and grind it to a particle size of less than 75μm as the experimental sample; at the same time, use pure lead carbonate powder with a particle size of less than 75μm and an equal mass as the control sample. Put the sample into 50 mL of distilled water and shake it continuously at 40 rpm at an ambient temperature of 25℃. After shaking for 150 days, the sample is tested.

[0074] In Example 1, the leaching rate of the precipitate was less than 1.2%, while the leaching rate of pure lead carbonate powder was 2.6%. By comparison, it can be seen that the precipitate containing solidified heavy metal ions separated by the method of this invention has better stability and is less prone to secondary leaching of heavy metal ions, indicating that this method has the advantages of high efficiency and low risk in treating heavy metal wastewater.

[0075] (3) Take 1g of the precipitate obtained in Example 1, dry it to absolute dryness, remove the bound water at 300℃, and burn it off at 900℃. Since 900℃ is lower than the decomposition temperature of calcium silicate raw materials but higher than the decomposition temperature of calcium carbonate, the amount of loss on ignition can be considered as the amount of CO2 absorbed by the calcium silicate material during the carbon mineralization reaction.

[0076] The test results showed that the precipitate in this embodiment absorbed approximately 0.2g of CO2, indicating that this method has a synergistic carbon fixation effect.

[0077] (4) Take 10g of the precipitate obtained in Example 1, press it into shape under a pressure of 50MPa, and hold the pressure for 1min. Prepare a cylindrical specimen with a diameter of 20mm and a height of about 20mm. Test the compressive strength of the specimen, and the strength of the specimen is about 13MPa. This shows that the precipitate separated by this method can be pressed into shape and used as landfill material, etc.

[0078] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for treating heavy metal wastewater, characterized in that, Includes the following steps: Calcium silicate material is added to wastewater containing heavy metal ions, and CO2 gas is introduced to obtain a mixture; The mixture is separated into solid and liquid components to obtain a purified liquid and a precipitate.

2. The processing method according to claim 1, characterized in that, The calcium silicate material includes at least one of γ-type dicalcium silicate, β-type dicalcium silicate, tricalcium silicate, monocalcium silicate, and industrial waste containing calcium silicate mineral phase, wherein the mass percentage of the calcium silicate mineral phase in the industrial waste is greater than or equal to 60%.

3. The processing method according to claim 1, characterized in that, Add 1-10g of the calcium silicate material to every 100mL of the wastewater.

4. The processing method according to claim 1, characterized in that, The CO2-containing gas is introduced for a time of 1 hour or more.

5. The processing method according to claim 1, characterized in that, The volume percentage of CO2 in the CO2-containing gas is 40-95%.

6. The processing method according to claim 1, characterized in that, The flow rate of the CO2-containing gas is 150~500 lpm.

7. The processing method according to claim 1, characterized in that, The pH of the wastewater is 0.5 to 7.

8. The processing method according to claim 7, characterized in that, The concentration of heavy metal ions in the wastewater is 100~3000 mg / L.

9. The processing method according to claim 1, characterized in that, The heavy metal ions include Pb. 2+ Cd 2+ Cu 2+ Ni 2+ Fe 3+ As 3+ At least one of them.

10. The processing method according to claim 1, characterized in that, After the step of separating the mixture into a solid-liquid mixture to obtain a purified liquid and a precipitate, the method further includes: pressing the precipitate into a mold for recycling.

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