A method for the recovery of anode sludges and their use as a raw material for phosphate coating chemical product

Abstract

The invention relates to a method for the recovery of valuable metals from anode sludge generated as a result of electroplating and / or electrochemical reactions, and the production of phosphate coating chemicals from the recovered valuable metals.

Description

[0001] A METHOD FOR THE RECOVERY OF ANODE SLUDGES AND THEIR USE AS A RAW MATERIAL FOR PHOSPHATE COATING CHEMICAL PRODUCT

[0002] TECHNICAL FIELD

[0003] The invention relates to a method for the recovery of valuable metals from anode sludge generated as a result of electroplating and / or electrochemical reactions, and the production of phosphate coating chemicals from the recovered valuable metals.

[0004] PRIOR ART

[0005] In the present techniques, anode sludge formation is a common result of both electroplating and various electrochemical processes.

[0006] In electroplating, the anode material dissolves during the metal plating process, providing metal ions to the electrolyte solution. In this process, substances detached from the anode but unable to dissolve into the electrolyte or that precipitate are collected as anode sludge. For example, during zinc plating, zinc used as the anode dissolves in the electrolytic cell and forms anode sludge.

[0007] Similarly, in electrochemical processes, the dissolution of electrodes also results in the formation of anode sludge. During water electrolysis, oxygen gas formation and oxidation reactions occur on the anode surface, leading to the generation of anode sludge. Moreover, in copper refining processes, anodic dissolution results in the formation of copper anode sludge, which contains valuable metals.

[0008] Another example of a known application of the technique is in the electrolytic cobalt production process, where the cobalt used as an anode dissolves to form cobalt anode sludge. The anode sludge is usually recovered during purification processes.

[0009] Another example of the known state of the art is observed in the aluminium refining process. In aluminium production by the Hall-Heroult method, carbon-based anode sludge is formed as a result of the dissolution of the graphite anode. The anode sludge is considered valuable due to its carbon content and other metallic components.

[0010] In the battery industry, especially in lithium-ion batteries, anode sludge can be formed during the use of anode materials. In lithium-ion batteries, graphite or other carbon-based anodes can form deposits and sludge on the surface as a result of the displacement of lithium ions during charge and discharge cycles. These deposits can affect the performance and lifetime of the battery and can be processed for the recovery of valuable materials.

[0011] Anode sludge can be formed in many different techniques. In sectors where electrochemical methods are employed — such as batteries, biosensors, water treatment, metal refining, photovoltaic cell production, and electroplating — reactions occurring between the anode and cathode result in the formation of anode sludge. This anode sludge emerges as a byproduct of such processes and is considered a significant source for the recovery of valuable metals contained therein.

[0012] The anode sludge generated as a result of electroplating and / or electrochemical processes in the present technique, examples of which are given above, pose problems for the environment and human health. Especially for the environment, it causes water pollution, soil pollution and air pollution; for human health, toxic substances cause respiratory diseases and irritation of the skin and eyes. Anode sludges should be cleaned or disposed of without direct discharge to the environment and human areas.

[0013] In relevant technical fields, anode sludges can be subjected to recovery processes. The objective is the selective recovery of valuable metals contained in anode sludges for use in other technical areas. However, in certain recovery processes of the known art, the valuable metals in electroplating anode sludges are subjected to costly and energy-intensive processes. In particular, the application of processes such as electro-drying leads to high energy consumption. Moreover, the use of complex and expensive equipment in recovery processes increases costs and prolongs processing times.

[0014] Another problem encountered in the prior art is the formation of toxic waste due to the use of lead-based or similar electrodes during the recovery of anode sludges. In this regard, the environmental harm caused by anode sludge is not fully eliminated, and the intended objectives are not achieved.

[0015] In the prior art, it has been determined that the processes are insufficient for the efficient separation of valuable metals to be obtained as a result of recovery operations. This leads to inefficiencies in waste management and results in resource wastage.

[0016] In the relevant technical field, various research and development efforts have been conducted to enable the recovery of valuable metals from anode sludges. One such study is described in patent application publication number CN 1827802 A, which relates to a method for recovering valuable metals from electroplating waste by precipitating them in the form of oxides and hydroxides. In this method, a simple acid-base filtration technique is applied to recover the valuable metals.

[0017] Another study, described in patent application publication number CN104419826 B, focuses not on valuable metal salts in general but specifically on obtaining a solution in which zinc oxide salts present in electroplating waste are dissociated into their ionic forms, followed by recovery using an electro-drying technique. During the electro-drying process, valuable metal ions in the solution are attracted to the surface of lead-based electrodes through the application of electric current. The metals are then separated from the electrode surface in metallic form, completing the recycling process. However, the electro-drying technique is a costly process that requires high energy consumption, and the use of toxic lead-based electrodes poses environmental and health risks.

[0018] In the related technical field, there is a need for the development of new processes that allow the efficient recovery of valuable metals from electroplating anode sludges, ensure the suitability of the recovered metals for use in various technical fields, and eliminate the need for additional treatment and disposal operations.

[0019] BRIEF DESCRIPTION OF THE INVENTION

[0020] The main objective of the invention is to provide a method for the recovery of valuable metals from anode sludge generated through the application of electroplating and / or electrochemical methods. The method of the invention aims to achieve the specific separation of components within the anode sludge by forming water-soluble and insoluble salts, thereby enabling low-cost and high-efficiency recovery.

[0021] The objective of the invention is to provide a method that enables the use of valuable metals, selectively recovered from anode sludge, as components in phosphate coating chemicals. Through the method disclosed in the invention, the production of phosphate coating chemicals from anode sludge has been made possible. In this way, the valuable metals contained in the anode sludge are converted into high value-added products.

[0022] Another objective of the invention is to enable the recovery of valuable metals from anode sludge without the need for using heavy metals such as lead or other components that may pose toxic effects. In this way, environmental risks can be minimized. Through the method of the invention, the recovery processes are rendered environmentally friendly and economically feasible.

[0023] BRIEF DESCRIPTION OF THE FIGURES

[0024] Figure 1-A shows the XRF analysis results of anode sludge obtained from a pure zinc electroplating plant before the method.

[0025] Figure 1-B shows the XRF analysis results of the phosphate coating chemical containing the active ingredient zinc phosphate obtained from the anode sludge after the method.

[0026] Figure 2 shows the XRD analysis result of the phosphate coating chemical containing zinc phosphate obtained by applying the method.

[0027] Figure 3-A shows the SEM morphology and elemental composition of the phosphate coating chemical containing zinc phosphate obtained by the method.

[0028] Figure 3-B shows the SEM morphology and elemental composition of a commercially known fine grained phosphate coating material.

[0029] Figure 4-A shows the polarisation test results of the plate coated with commercially known fine grained phosphate coating material. Figure 4-B shows the polarisation test results of the plate coated with the phosphate coating chemical obtained by the method.

[0030] DETAILED DESCRIPTION OF THE INVENTION

[0031] The invention relates to a method for the recovery of valuable metals from anode sludge and the production of phosphate coating chemicals from the recovered valuable metals. The methods of recovering precious metals from anode sludge subject to the invention and using said precious metals in phosphate coating are independent of the method in which the anode sludge is formed. The anode sludge is formed as a result of electroplating and / or electrochemical reactions in the prior art does not affect the method of recovery of valuable metals from the anode sludge disclosed in the invention. However, anode sludge formed as a result of electroplating is preferably used in the works of the invention.

[0032] The method disclosed in the invention provides two technical teachings for the relevant technical field. The first technical teaching is the specific recovery of valuable metals from anode sludge. This specific recovery enables the high-efficiency extraction of valuable metals contained in the anode sludge. The second technical teaching provided by the invention is the use of the valuable metals obtained from anode sludge as raw materials in the production of phosphate coating chemicals, which differs from what is known in the prior art.

[0033] The anode sludge characterized in the present invention comprises at least one of the metals or compounds of zinc, manganese, iron, and calcium. In this context, the valuable metal targeted for recovery in the invention is at least one of zinc, manganese, iron, and calcium or their respective compounds. Any anode sludge containing these valuable metals falls within the scope of protection of the invention.

[0034] In this invention, the final product is a phosphate coating chemical. The phosphate coating chemical is a solution composed of chemical substances used particularly during the phosphate coating of metal surfaces. This chemical is used to protect metal surfaces against corrosion, to improve the adhesion of paints and other coatings, to enhance wear resistance, and in some cases, to provide electrical insulation. In the present invention, by recovering at least one of the valuable metals from the group comprising zinc, iron, manganese, and calcium contained in the anode sludge, at least one of the following compounds is obtained: zinc phosphate, iron phosphate, manganese phosphate, and calcium phosphate.

[0035] The method for the recovery of valuable metals from anode sludge disclosed in the present invention essentially comprises the treatment of the anode sludge through acid-base reactions, the specific dissolution of valuable metals, and the disposal of the remaining anode sludge in solid form.

[0036] In the invention, the first step involves performing a chemical composition analysis of the raw material, namely the anode sludge. In the method of the invention, the use of certain chemicals is critical depending on the chemical composition of the anode sludge. The tests conducted to determine the chemical content of the anode sludge are not limited within the scope of protection of the invention.

[0037] The recovery of valuable metals is carried out based on the components identified in the analyzed anode sludges. These processes involve acid-base reactions, filtration, and solidliquid separation operations.

[0038] In the invention, the valuable metals obtained through the application of the disclosed method are subsequently reacted with at least one phosphate-containing acid. The resulting metal phosphates can be used as active ingredients in phosphate coating chemicals. The obtained active ingredient is combined with other components present in the phosphate coating chemical to enable the production of a stable commercial product. In the context of the invention, the term "active ingredient" refers to the component that primarily provides the expected performance of the phosphate coating chemical.

[0039] The method disclosed in the present invention comprises the following process steps:

[0040] - introducing into a system anode sludge formed as a result of electroplating and / or electrochemical reactions and containing at least one of zinc, iron, manganese, and / or calcium, and analyzing the composition thereof; subjecting the analyzed anode sludge to a drying process to adjust its moisture content;

[0041] - obtaining the solution by subjecting the anode sludge, which reaches the target moisture content, to processes in the reaction medium containing acid + water mixture according to the components in its content,

[0042] - the resulting solution is filtered and separated into solid and liquid phases, adding the resulting liquid phase to the mixture containing the components of the phosphate coating chemical and obtaining the phosphate coating chemical containing phosphate compounds of the target precious metals as active ingredients.

[0043] In a preferred embodiment of the invention, the said drying processes are carried out at a temperature range of 70 to 90 °C. Depending on the applied temperature, the drying process may be conducted for a duration of 1 to 5 hours. This process is performed to reduce the moisture content of the anode sludge to specified levels. The target moisture content in the anode sludge is in the range of 1% to 5% by weight.

[0044] The most critical process step of the method disclosed in the invention is the treatment of anode sludge with an acid+water mixture. In a preferred embodiment, the acid+water mixture is contained within an acid tank. The critical objective at this stage is to obtain valuable metal compounds dissolved in the liquid phase. Accordingly, the acid+water mixture used in the process must be selected based on the specific valuable metal present in the anode sludge. Compounds that are not soluble remain in the solid phase and are removed from the system.

[0045] It is essential to use mixtures with low pH values and specific solubilisation of precious metals. Therefore, it is critical to analyse the precious metals in the anode sludge. According to these analyses, the following acid+water mixtures are used in the processes. The salt forms of one or more of the precious metals zinc, manganese, iron and calcium in the anode sludge are converted into water soluble salt forms depending on the specific acid selected. At least one of ammonium chloride, ammonium carbonate, hydrochloric acid, nitric acid, sulphuric acid, acetic acid, chloric acid, perchloric acid, perchloric acid, boric acid, oxalic acid, citric acid, hydrogen fluoride, hydrogen cyanide, hydrogen bromide, hydrogen iodide, carbonic acid, boric acid group is included in the acid+water mixture. The treatment of anode sludge with the acid+water mixture is performed under controlled temperature and pH conditions. This is an exothermic reaction. The temperature of the reaction medium must be maintained within the range of 50 to 60 °C. Similarly, as it is a pH-controlled reaction, the pH value of the reaction medium must be maintained within the range of 1.2 to 3.5. To achieve this, the most suitable acid+water mixture is used. In the acid+water mixture, the acid-to-water ratio by weight is within the range of 1:2 to 1:3. The purity of the acid(s) used is between 99.7% and 99.9%. The specified temperature ensures optimal process durations. If the reactions are carried out outside the specified temperature range, undesired phases or complexes may form from the anode sludge. Similarly, if the reactions are carried out outside the specified pH range, the metal ions within the anode sludge may not transfer to the liquid phase, thereby reducing the efficiency of the process.

[0046] As stated in the invention, the fact that the processes can be carried out through exothermic reactions means that the process can proceed without the need to supply additional thermal energy to the system. This condition contributes to the reduction of overall process costs.

[0047] In the said process step, the anode sludge-to-acid ratio by weight is in the range of 0.8:2 to 1.2:2. By maintaining the specified weight ratio of anode sludge to acid, it becomes possible to ensure a sufficient amount of acid in the reaction medium and to achieve a balanced dissolution of metal complexes. Moreover, the specified weight ratio allows the reaction medium to attain an appropriate pH value and optimizes the conditions for the solubility of metal ions.

[0048] The liquid phase obtained as a result of the reaction of the anode sludge with the acid+water mixture in the acid tank, which contains the salt forms of the valuable metals, is separated by filtration for use in subsequent processing steps. The liquid phase obtained in this manner will hereinafter be referred to as Mixture A in this invention. The solid phase obtained during the filtration process is considered waste and is transferred to the waste section.

[0049] Mixture A primarily comprises the compounds formed by the reaction between the valuable metal present in the anode sludge and the acid in the acid+water mixture. For example, if the valuable metal in the anode sludge is zinc, its reaction with hydrochloric acid in the acid+water mixture results in the formation of zinc chloride, which is then included as a component in Mixture A.

[0050] Mixture A obtained through the filtration process is added to a mixture comprising the components of the phosphate coating chemical, in order to react with at least one phosphate-containing acid. The mixture comprising the components of the phosphate coating chemical will hereinafter be referred to as Mixture B in this invention.

[0051] Mixture B comprises at least one phosphate-containing acid selected from the group of organic phosphoric acids, phosphorus acid derivatives, or phosphonic acids. In the context of this invention, the phosphate-containing acid present in Mixture B comprises hydrogen, oxygen, and phosphate, and does not comprise any metal. In a most preferred embodiment, the phosphate-containing acid in Mixture B comprises at least one acid selected from the group comprising orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, diphosphoric acid, polyphosphoric acid, triorthophosphoric acid, tetraorthophosphoric acid, and hexaorthophosphoric acid. The phosphate-containing acid is present in solution with water. In the said solution, the phosphate-containing acid to water ratio is in the range of 1:4 to 1:7. In Mixture B, the phosphate acid+water solution is present in an amount ranging from 80% to 90% by weight.

[0052] The reaction carried out for the production of the phosphate coating chemical is controlled in terms of both pH and temperature. The reaction temperature must be maintained within the range of 25 to 60 °C. Similarly, as the reaction is pH-controlled, the pH value must be maintained within the range of 2 to 3.

[0053] Mixture B additionally comprises auxiliary components intended to enhance the performance of the phosphate coating chemical. These auxiliary components comprise at least one selected from the group comprising surfactants, pH-adjusting agents, reaction accelerators, and complexing agents.

[0054] Mixture B comprises at least one pH-adjusting agent. As a pH-adjusting agent, Mixture B comprises at least one compound selected from the group comprising calcium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, ammonium hydroxide, lithium hydroxide, barium hydroxide, strontium hydroxide, and aluminum hydroxide. As is known, phosphate coating chemicals are applied to substrate surfaces at a pH value in the range of 1.9 to 3. The pH value affects the grain size of phosphate crystals within the phosphate coating chemical, and therefore, it is critical that the pH be adjusted according to the intended application area of the phosphate coating chemical. To obtain the phosphate coating chemical within the specified pH range, at least one pH-adjusting agent is used. In order to achieve the targeted pH values, the pH-adjusting agent is present in the mixture at a concentration ranging from 5% to 10% by weight.

[0055] Mixture B comprises at least one complexing agent. As a complexing agent, Mixture B comprises at least one compound selected from the group comprising ethylenediaminetetraacetic acid, nitrilotriacetic acid, sodium nitrilotriacetate, diethylenetriaminepentaacetic acid, citric acid, and tartaric acid. In the invention, the phosphate coating chemical comprises at least one complexing agent to stabilize metal ions and to prevent undesired reactions within the solution. In this way, precipitation of components in the phosphate coating chemical is avoided. In a preferred embodiment, Mixture B comprises at least one complexing agent in an amount ranging from 0.1% to 2% by weight. If the mixture comprises more than 2% by weight of complexing agent, it may cause changes in the final pH value of the phosphate coating chemical; therefore, the specified values are critical.

[0056] Mixture B comprises at least one accelerator component. As an accelerator, Mixture B comprises at least one compound selected from the group comprising urea, ammonium nitrate, hydrogen peroxide, nitrobenzene, potassium nitrate, sodium nitrate, ammonium chloride, calcium nitrate, and magnesium nitrate. The phosphate coating chemical of the invention comprises at least one accelerator component to increase the rate of the reactions that enable the coating process and to improve the homogeneity of the coating. In a preferred embodiment, Mixture B comprises at least one accelerator component in an amount ranging from 1% to 5% by weight. If the accelerator component is present in an amount less than the specified range, a homogeneous appearance may not be achieved on the surface treated with the phosphate coating chemical. If it is present in an amount exceeding the specified range, large non-standard volume crystals may form within the phosphate coating chemical. Mixture B comprises at least one surfactant. As a surfactant component, Mixture B comprises at least one compound selected from the group comprising alkyl amine oxide, alkyl nitronate, alkyl polyglycoside, cellulose, alkyl glucoside, alkyl betaine, ethylene oxide copolymer, propylene oxide copolymer, polyethylene glycol, polypropylene glycol, alkyl sulfate, nonylphenol ethoxylate, alkyl phenol ethoxylate, octylphenol ethoxylate, and alkyl amine ethoxylate. In the invention, the phosphate coating chemical comprises at least one surfactant to reduce surface tension, thereby improving the wettability of the material to be coated, and to reduce foaming on the surface, thereby enabling the formation of a homogeneous coating layer.

[0057] In a preferred embodiment, Mixture B comprises at least one surfactant in an amount ranging from 0.1% to 2% by weight. If the surfactant is present in an amount outside the specified range, excessive foaming or the formation of impurities may occur in the phosphate coating chemical.

[0058] The ratio at which Mixture A, containing the salt forms of the recovered valuable metals, is combined with Mixture B, which comprises the components of the phosphate coating chemical, is critical. These ratios are expressed by weight. As a result of the research and development activities conducted within the scope of this invention, the present inventors have determined that the weight ratio of Mixture A to Mixture B should be in the range of 1:2 to 1:3.5. If the specified ratio is exceeded, the amount of valuable metal (e.g., Zn) in the phosphate coating chemical becomes too high, resulting in a lower pH value. Conversely, if the ratio is below the specified range, the phosphate coating chemical exhibits a higher pH value.

[0059] In another aspect, the invention relates to a phosphate coating chemical obtained from anode sludge. This phosphate coating chemical comprises at least one compound selected from the group comprising zinc phosphate, iron phosphate, manganese phosphate, and calcium phosphate derived from anode sludge. Additionally, the phosphate coating chemical comprises at least one auxiliary component selected from the group comprising surfactants, pH-adjusting agents, reaction accelerators, and complexing agents.

[0060] The critical process steps of the method disclosed in the invention comprises reactions carried out under controlled pH and temperature conditions. It is known to those skilled in the art that appropriate tanks or containers must be used for the environment in which these reactions take place. The scope of protection of the invention is not limited by the specific conditions under which these reaction environments are provided.

[0061] The XRF analysis results of anode sludge samples taken from a pure zinc electroplating facility prior to the application of the method disclosed in the invention are presented in Figure 1-A. In Figure 1-B, the XRF analysis result of the phosphate coating chemical obtained from the anode sludge by applying the method of the invention, and containing zinc phosphate as the active ingredient, is provided. Notably, the spectrum of the raw anode sludge shows a noisy profile due to the presence of non-metallic complex molecules. In contrast, the sludge processed by the inventive technique was found to contain predominantly zinc and minor amounts of iron. The absence of noise peaks on the right side of the spectrum indicates that impurities have been successfully removed from the structure, and the resulting spectrum exhibits the characteristic profile of a typical zinc phosphate coating.

[0062] Figure 2 shows the XRD analysis result of the phosphate coating chemical containing zinc phosphate, obtained through the application of the method disclosed in the invention. According to the analysis, the formation of the hopeite (Zm PO^AFbO) phase — recognized as the primary component providing corrosion resistance in zinc phosphate coatings — was clearly identified.

[0063] Figure 3-A shows the SEM morphology and elemental composition of the phosphate coating chemical containing zinc phosphate, obtained through the application of the method disclosed in the invention. Figure 3-B shows the SEM morphology and elemental composition of a commercially known fine-grained phosphate coating material. The SEM analysis confirmed that the phosphate coating chemical produced by the method of the invention meets the criteria of having a crystal size of less than 10 pm and a coating coverage greater than 90%.

[0064] Figure 4-A shows the polarization test results of a plate coated with a commercially known fine-grained phosphate coating material. Figure 4-B shows the polarization test results of a plate coated with the phosphate coating chemical obtained through the method of the invention. According to the Tafel findings, the corrosion resistance of the phosphate coating product obtained by the inventive technique was compared with that of the commercially used fine-grained phosphate coating product. Based on the results, the phosphate coating chemical derived from anode sludge exhibited comparable corrosion resistance, and in some samples, even higher corrosion resistance was achieved.

[0065] Through the method disclosed in the invention, the environmental impact of anode sludge is reduced, and its inclusion in sustainable production is enabled. Compared to equivalent applications in the prior art, the method of the invention provides energy savings in the recycling of anode sludge. In addition, the valuable metals obtained from anode sludge by means of the inventive method can, unlike in the prior art, be used as active ingredient raw materials in phosphate coating chemicals.

[0066] The method disclosed in the invention comprises processes that are carried out without the need for expensive and complex equipment.

[0067] The scope of protection of the invention is defined in the claims provided in the annex and shall in no way be limited to the embodiments described in this detailed description for illustrative purposes. It is evident that a person skilled in the art may develop similar configurations in light of the above description without departing from the core concept of the invention.

Claims

CLAIMS1. A method for recovering valuable metals from anode sludge generated through electroplating and / or electrochemical reactions and for producing phosphate coating chemicals from the recovered metals, characterized in that it comprises the steps of:§ introducing into a system anode sludge containing at least one of zinc, iron, manganese, and / or calcium, and analyzing the composition thereof;§ subjecting the analyzed anode sludge to a drying process;§ obtaining the solution by subjecting the anode sludge, which reaches the target moisture content, to processes in the reaction medium containing acid + water mixture according to the components in its content;§ filtering the obtained solution to separate it into solid and liquid phases, and collecting the liquid phase as Mixture A;§ adding Mixture A to Mixture B, which contains phosphate -based chemical components, to form a reaction medium having a pH value between 2 and 3 and a temperature between 25 °C and 60°C;§ reacting the metals in Mixture A with the phosphate-containing acid in Mixture B to obtain a phosphate coating chemical comprising phosphate compounds of the valuable metals as active ingredients.

2. The method according to claim 1, characterized in that the drying process is carried out at a temperature in the range of 70°C to 90°C.

3. The method according to any one of the preceding claims, characterized in that the acid: water ratio by weight in the acid+water mixture is in the range of 1:2 to 1:3.

4. The method according to any one of the preceding claims, characterized in that the weight ratio of anode sludge to acid in the reaction medium is in the range of 0.8:2 to 1.2:2.

5. The method according to any one of the preceding claims, characterized in that the said Mixture B comprises at least one acid selected from the group comprisingorthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, diphosphoric acid, and polyphosphoric acid as the phosphate- containing acid.

6. The method according to any one of the preceding claims, characterized in that the weight ratio of acid to water in Mixture B is in the range of 1:4 to 1:7.

7. The method according to any one of the preceding claims, characterized in that Mixture B comprises a phosphate-containing acid solution having a weight percentage in the range of 80% to 90%.

8. The method according to any one of the preceding claims, characterized in that Mixture B comprises at least one component selected from the group comprising surfactants, pH-adjusting agents, reaction accelerators, and complexing agents.

9. The method according to claim 8, characterized in that the pH-adjusting agent comprises at least one compound selected from the group comprising calcium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, ammonium hydroxide, lithium hydroxide, barium hydroxide, strontium hydroxide, and aluminum hydroxide.

10. The method according to claim 8 or claim 9, characterized in that Mixture B comprises at least one pH-adjusting agent in an amount by weight in the range of 5% to 10%.

11. The method according to any one of claims 8 to 10, characterized in that the complexing agent comprises at least one compound selected from the group comprising ethylenediaminetetraacetic acid, nitrilotriacetic acid, sodium nitrilotriacetic acid, diethylenetriaminepentaacetic acid, citric acid, and tartaric acid.

12. The method according to any one of claims 8 to 11, characterized in that Mixture B comprises at least one complexing agent in an amount by weight in the range of 0.1% to 2%.

13. The method according to any one of claims 8 to 12, characterized in that the reaction accelerator comprises at least one compound selected from the group comprising urea, ammonium nitrate, hydrogen peroxide, nitrobenzene, potassium nitrate, sodium nitrate, ammonium chloride, calcium nitrate, and magnesium nitrate.

14. The method according to any one of claims 8 to 13, characterized in that Mixture B comprises at least one reaction accelerator in an amount by weight in the range of 1% to 5%.

15. The method according to any one of claims 8 to 14, characterized in that the surfactant comprises at least one compound selected from the group comprising alkyl amine oxide, alkyl nitronate, alkyl polyglucoside, cellulose, alkyl glucoside, alkyl betaine, ethylene oxide copolymer, propylene oxide copolymer, polyethylene glycol, polypropylene glycol, alkyl sulfate, nonylphenol ethoxylate, alkylphenol ethoxylate, octylphenol ethoxylate, and alkylamine ethoxylate.

16. The method according to any one of claims 8 to 15, characterized in that Mixture B comprises at least one surfactant in an amount by weight in the range of 0.1% to 2%.

17. The method according to any one of the preceding claims, characterized in that the weight ratio of Mixture A to Mixture B is in the range of 1:2 to 1:3.5.

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