A method for reducing leaching of inorganic oxides during treatment with aqueous media

Abstract

The present application relates to a method for controlling the leaching of inorganic oxides in aqueous media by mixing them with organic thermoplastic polymer and utilizing selective laser sintering (SLS) 3D printing to prepare porous scavenger elements from the combination of inorganic oxides and organic thermoplastic polymers. The scavenger elements find use in catalysis as well as collecting dissolved metals and ions from aqueous fluids.

Description

A METHOD FOR REDUCING LEACHING OF INORGANIC OXIDES DURING TREATMENT WITH AQUEOUS MEDIAFIELD

[0001] The present invention relates to a method for controlling the leaching of inorganic oxides in aqueous media by mixing them with organic thermoplastic polymers and utilizing selective laser sintering (SLS) 3D printing to prepare porous scavenger elements from the combination of inorganic oxides and organic thermoplastic polymers. The scavenger elements find use in catalysis as well as collecting dissolved metals and ions from aqueous fluids.BACKGROUND

[0002] The optimization of industrial processes to efficiently utilize by-products and circulate materials is a rapidly growing field. In addition to recycling solid materials, there is increasing interest in reclaiming valuable elements from various streams. For instance, soluble metals — including battery metals (Li, Ni, Co, Mn, Al, Cu, Zn) and rare-earth elements (REEs) — can be recovered or used in catalytic applications, underscoring the broad utility of such approaches.

[0003] Inorganic oxides are highly valued for their versatility and customizable properties. Their strong affinity for specific metal ions, combined with the ability to tailor their structure, makes them useful in applications ranging from metal recovery to catalysis. For example, titanium oxide, manganese oxide, and iron oxide have been employed to selectively adsorb metals from aqueous media as well as to catalyze various chemical reactions.

[0004] The customizable structure of inorganic oxides allows them to be engineered for optimal performance in diverse applications. Whether the goal is to maximize metal ion adsorption and selective desorption or to enhance catalytic activity, these oxides offer significant advantages. However, a major challenge is that the oxide components can leach during repeated process cycles. This leaching compromises their structural integrity and long-term effectiveness, necessitating measures to control or mitigate this behavior.

[0005] Leaching of metal oxides typically occurs during process steps that involve chemical washing or regeneration. Acidic or otherwise leaching-inducing chemicals (for example, hydrochloric or sulfuric acid) can dissolve parts of the oxide structure along with any adsorbed species. Repeated exposure to such conditions can lead to the gradual degradation of the oxide material, thereby reducing its performance in applications like metal recovery or catalysis. Furthermore, factors such as the concentration of chemicals, temperature, and the presence of oxidizing or reducing agents significantly influence the leaching behavior.

[0006] Mitigating the leaching of metal oxides is crucial to extending their operational lifetime and maintaining consistent performance. Reducing leaching not only minimizes the need for frequent material replacement — thereby saving costs in both materials and operational downtime — but also ensures that the material continues to perform effectively in various applications, be it in metal recovery or catalytic processes.

[0007] Several strategies have been investigated to limit the leaching of metal oxides by preserving their chemical and physical structure. Approaches include optimizing the concentration of leaching agents (such as acids) to reduce their aggressiveness while still achieving necessary regeneration effects, controlling the pH during processing, and applying protective surface coatings to the oxides. Despite these efforts, many of these methods have limitations and may not fully prevent significant leaching over prolonged use.

[0008] Therefore, there remains a need to enhance methods for reducing oxide leaching to improve the durability and effectiveness of metal oxides in various industrial applications. In this context, the present invention introduces a novel approach: by combining metal oxides with a thermoplastic polymeric material and utilizing SLS 3D printing to create a sintered, porous scavenger element, the leaching of the oxide is substantially reduced. This advancement ensures sustained performance in applications such as metal recovery and catalysis while broadening the overall usability of the material.SUMMARY OF THE INVENTION

[0009] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0010] The present invention is based on the finding that by incorporating thermoplastic organic polymer to the chosen metal oxide followed by SLS 3D printing of the material mixture, a porous scavenger element with the chemical functionality of the metal oxide can be obtained while reducing the leaching of the metal oxide, even by 80 % if compared to the metal oxide being utilized in a powderous or a granular form.

[0011] The reduced leaching of the metal oxide is proposed to be a function of the stabilization of the metal oxide into the thermoplastic organic polymer structure combined with suitable sintering process further improving the stability of the resulting porous scavenger element.

[0012] The reduced leaching of the metal oxide is also proposed to be a function of the re-precipitation behaviour of the leached metals that is influenced by the stabilization of the metal oxide into the thermoplastic organic polymer structure.

[0013] The method according to the invention for reducing the leaching of inorganic oxides during treatment with aqueous media comprises a stepwise process ofi) mixing one or more inorganic oxides possessing appropriate particle size, ideally between 1-300 pm, with organic thermoplastic polymer having an appropriate particle size, ideally between 5-300 pm, in a weight ratio of inorganic oxide to thermoplastic polymer of 30:70 to 80:20, andii) preparing the mixture comprising the inorganic oxide and the thermoplastic polymer into a porous scavenger element by utilizing SLS 3D printing process where the laser sintering parameters are adjusted to result in a porous body with bulk density, defined as weight of the porous body divided by the volume of the porous body, of 0.4-0.7 kg / dm3.

[0014] The porous scavenger elements can be utilized for by placing them in a pressure vessel and compressing porous scavenger elements between suitable gasket materials, allowing for process fluids or aqueous fluids to be pumped through the porous scavenger element.

[0015] Alternatively, the porous scavenger elements can be utilized by placing them in a pressure vessel loosely and by pumping chosen fluid through the bed of porous scavenger elements.

[0016] The SLS 3D printing of the material combination into a porous scavenger element includes specific control of the sintering parameters such as laser power, laser speed, different process temperatures, laser hatch distance, laser pattern and other relevant parameters to allow the resulting porous scavenger element to show bulk density of 0.4-0.7 kg / dm3defined as weight of the porous body divided by the volume of the porous body.

[0017] Considerable advantages are obtained by the invention. First, the method of the present invention remarkably reduces the leaching behaviour of the metal oxides, in some embodiments by up to 80 % if compared to similar process operated with metal oxides utilized in a powderous or granular form. This allows for higher degree of material stability, leading to lower frequency of material replacement as well as the ability to utilize higher concentration of washing solutions.

[0018] Second, when the leaching of the metal oxide is reduced the industrial process utilizing the oxide can remain more stable for extended period of time as the physical and chemical structure of the metal oxide undergoes change at a lower pace. These processes can include for example catalysis or metal recovery process remains more stable.

[0019] Further features and advantages of the present technology will appear from the following description of some embodiments.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIGURE 1 is a microscope image of the cross-section of the porous scavenger element where metal oxide is stabilized onto the polyamide structure.DETAILED DESCRIPTION OF THE INVENTION

[0021] DEFINITIONS

[0022] In the present context, the term “scavenger” refers generally to a solid physical body with a porous structure, The term may thus refer also to a SLS 3D printed porous body or several SLS 3D printed porous bodies.

[0023] As used herein, the term “scavenger element” comprises one or several SLS 3D printed porous bodies, optionally together with flexible gaskets.

[0024] In the present context, the term “metal oxide” refers to a crystalline solid compound, typically consisting of metal cations and oxide anions.

[0025] As used herein, “leaching” refers to a refers to the process where metals are dissolved and removed from the oxide material, leading to the loss of part of the metal content.

[0026] As used herein, “organic polymer” and “thermoplastic organic polymer” refer to a polymeric material that is used in combination with the metal oxide to allow the sinterability of the resulting material mixture. Examples of these organic polymers include polyamide and polypropylene.

[0027] “Dimensions” refer to both vertical and horizontal dimensions.

[0028] “Washing” refers to the act of pumping chosen aqueous fluid through the porous scavenger element. Typically, the aqueous fluid or aqueous media comprises acidic fluids, salt solutions, oxidizing solutions or alkaline solutions.

[0029] SLS 3D printing parameters” refer to settings of a 3D printer when printing SLS 3D printed porous scavenger elements. Typically said printing parameters include settings such as power and speed of the laser, hatch distance (distance between two consecutive laser beams), height of each printed layer, and temperature of the powder bed during manufacturing.

[0030] “Powder” refers to the materials used in the manufacture of porous bodies by SLD 3D printing. Typically, the materials comprise at least a thermoplastic organic polymer. In the present invention, said materials comprise a thermoplastic organic polymer and metal oxide.

[0031] “Density” or “bulk density” refers to the weight of the material in a given volume and is calculated / measured by weighing the object in question and dividing the weight by the outer dimensions of the object.

[0032] In one embodiment, the preparation of material combinations in the present invention include mixing of one or more oxides, typically metal oxides, possessing appropriate particle size ideally between 1-300 pm with organic thermoplastic polymer with particles size ideally between 5-300 pm in a weight ratio of inorganic oxide to thermoplastic polymer of 30:70 to 80:20. In some embodiments the oxides, in particularlythe metal oxides, may have a particle size between 1-100 pm. As stated above, the inorganic oxide(s) are mixed with the thermoplastic polymer in a weight ratio of inorganic oxide to thermoplastic polymer of 30:70 to 80:20, in some embodiments in a weight ratio of inorganic oxide to thermoplastic polymer of 50:50 to 80:20.

[0033] The material combination comprising or consisting of one or more oxides, typically metal oxides, and organic thermoplastic polymer is printed by using SLS 3D printing to form a porous scavenger element or porous body having a bulk density of 0.4-0.7 kg / dm3. Importantly, activity is not lost in the printing process even though the active material (oxide) may be partially embedded, if the bulk density is within the above-mentioned range of 0.4-0.7 kg / dm3, preferably 0.55-0.65 kg / dm3.

[0034] In one embodiment, the material referred to here as metal oxide is selected from the list of titanium oxide, manganese oxide, nickel oxide, aluminum oxide, iron oxide, zirconium oxide, vanadium oxide, magnesium oxide, molybdenum oxide or combination thereof. In some embodiments, the metal oxide is titanium oxide or manganese oxide.

[0035] In one embodiment, the material referred to here as metal oxide is a mixed metal oxide, where the cation mixture of the oxide is selected from lithium, sodium, potassium, magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ammonium or cerium, and the anion is oxide.

[0036] In one embodiment, the material referred to here as metal oxide is a mixed metal hydroxide, where the cation mixture of the oxide is selected from lithium, sodium, potassium, magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ammonium or cerium and the anion is hydroxide.

[0037] In one embodiment, the material referred to here as metal oxide is either unmodified or modified version of minerals such as but not limited to ilmenite, muscovite, vermiculite, clinoptilolite, anatase, rutile, bimessite, lepidolite, spodumene, petalite or combination thereof.

[0038] In one embodiment, the material referred to here as metal oxide is layered double hydroxide. Thus, the metal oxide may also be a mixed metal oxide, a mixed metal hydroxide, an unmodified or modified version of a mineral, or a layered double hydroxide.

[0039] In one embodiment, the organic thermoplastic polymer is chosen from polyamide, polypropylene, thermoplastic polyurethane, polystyrene.

[0040] In one embodiment, the organic thermoplastic polymer is chosen from polyamide, polypropylene, thermoplastic polyurethane, polystyrene or polyether ketone.

[0041] In one embodiment, the porous scavenger element is washed by using acidic fluids chosen from hydrochloric acid, sulphuric acid, nitric acid, phosphoric acid, citric acid, acetic acid or mixture thereof.

[0042] In one embodiment, the porous scavenger element is washed by using salt solutions chosen from sodium chloride, aluminum chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, sodium phosphate or mixture thereof.

[0043] In one embodiment, the porous scavenger element is washed by using oxidizing solutions chosen from ammonium peroxy di sulfates, sodium peroxy di sulfates, potassium ferrates, or mixture thereof.

[0044] In one embodiment, the porous scavenger element is washed by using alkaline solutions chosen from sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, sodium bicarbonate, or mixture thereof. Thus, the porous scavenger element may be washed for example by using acidic fluids, salt solutions, oxidizing solutions and / or alkaline solutions.

[0045] In one embodiment, the porous scavenger element can be washed with 0.1 -2 M sulfuric acid with limited leaching during washing process.

[0046] In one embodiment, the porous scavenger element can be washed with 0.1 -2 M hydrochloric to with limited leaching during washing process.

[0047] In one embodiment, the washing of the porous scavenger element with 0.1-2 M sulfuric acid leads to leaching of 0.001-1 % of the total metal oxide present in the porous scavenger element. This leaching is defined as the degree of lost metal oxide compared to metal oxide present in the porous scavenger element after their manufacturing process with SLS 3D printing.

[0048] In one embodiment, the washing of the porous scavenger element with 0.1-2 M hydrochloric acid leads to leaching of 0.001-1 % of the total metal oxide present in the porous scavenger element. This leaching is defined as the degree of lost metal oxide compared to metal oxide present in the porous scavenger element after their manufacturing process with SLS 3D printing.

[0049] In one embodiment, the metal oxide showing reduced leaching behavior is titanium oxide, manganese oxide or combination thereof.

[0050] In one embodiment, the metal oxide leaches during washing step but is then re-precipitated onto the porous scavenger element.

[0051] In one embodiment, the metal oxide leaching behaviour is reduced by 70% if compared to leaching observed during similar washing process performed for powderous metal oxide with material particle size of below 50 micrometers.

[0052] In one embodiment, the metal oxide leaching behaviour is reduced by 50 % if compared to leaching observed during similar washing process performed for granulous metal oxide with material particle size of below 5 millimeters.

[0053] In one embodiment, the porous scavenger element density has a direct correlation with the reduction observed in leaching behaviour of the metal oxide.

[0054] The SLS 3D printing parameters are adjusted to receive the required bulk density values of the porous scavenger elements. Typically, parameters such as power and speed of the laser as well as the laser route, hatch distance (i.e. distance between two consecutive laser beams), height of each printed layer, and temperature of the powder bed during manufacturing parameters need attention. For example, one or several of the following parameters and / or settings have been found to useful in adjusting the density and / or energy density values to the desired ranges:• 4-50 W laser power (for CO or CO2 laser)• 2000 - 6000 mm / s laser speed• 0.2-1 mm hatch distance• 0.08-0.8 mm layer height• 166-180 °C powder bed temperature during manufacturingPreferably, the SLS 3D printing parameters may be selected from the following parametersor combinations thereof:• 5-15 W laser power (for CO or CO2 laser)• 4000-6000 mm / s laser speed• 0.2-0.4 mm hatch distance• 0.08-0.2 mm layer height• 166-174°C powder bed temperature during manufacturing.

[0055] In some embodiments, the SLS 3D printing process step is performed by utilizing energy densities, defined as amount of laser-based energy introduced into a certain surface area, between 4 and 20 mJ / mm2.

[0056] In some embodiments, the SLS 3D printed porous scavenger may have a cylindrical structure. Typically, the diameter of the cylinder may range from 2 to 30 cm and the height of the cylinder from 2 to 30 cm.

[0057] In some embodiments, the porous scavenger element has a spherical structure, preferably with a diameter of 0.5 cm to 5 cm.

[0058] As discussed above, the porous scavenger elements, such as those having a cylindrical structure, can be placed in a pressure vessel and compressed between suitable, preferably flexible, gasket materials, allowing aqueous fluids to be pumped through the porous scavenger elements. Alternatively, the porous scavenger elements, such as those having a spherical structure, can be utilized by placing them in a pressure vessel loosely and by pumping chosen fluid through the bed of porous scavenger elements.

[0059] In some embodiments the washing fluids are fed through the scavenger system with a flow rate, which is 5-500 bed volume / hour, typically 5-50 bed volume / hour.

[0060] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0061] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the presentinvention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0062] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0063] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.EXPERIMENTAL

[0064] Example 1. Effect on TiO2 leaching behaviour with sulfuric acid

[0065] Material combination including 50 weight percent of TiO2 (average particle size 50 pm) and 50 weight percent of PA12 (average particle size 50 pm) was prepared into porous scavenger elements with resulting scavenger element density of 0.6 kg / dm3 and cylindrical structure with diameter of 2 cm and height of 2 cm. The porous scavenger element was then washed with 0.5 M sulfuric acid by pumping it through the scavenger element placed in a suitable reactor at the flowrate of 5 bed volumes per hour for 5 bedvolumes. For comparison a similar bed volume of TiO2 powder was placed in a suitable reactor and washed with 0.5 M sulfuric acid by pumping it through the scavenger element placed in a suitable reactor at the flowrate of 5 bed volumes per hour for 5 bed volumes. The washing solutions were analysed with ICP-OES to study the amount of Ti leached from the materials. The results are presented below in Table 1.Table 1. Leaching results of TiO2 displayed as a relative leaching compared to the TiO2 powder experiment. For clarity, the powder TiO2 experiment is displayed as 100 %.

[0066] As can be seen from the above results, the TiO2 in powder form shows considerably higher leaching behaviour if compared to the porous scavenger element with the TiO2 stabilized into the porous structure.

[0067] Example 2. Effect on Mn02 leaching behaviour

[0068] Material combination including 50 weight percent of Mn02 (average particle size 50 pm) and 50 weight percent of PA12 (average particle size 50 pm) was prepared into porous scavenger elements with resulting scavenger element density of 0.58 kg / dm3 and cylindrical structure with diameter of 2 cm and height of 2 cm. The porous scavenger element was then washed with 0.5 M sulfuric acid by pumping it through the scavenger element placed in a suitable reactor at the flowrate of 5 bed volumes per hour for 5 bed volumes. For comparison a similar bed volume of Mn02 powder was placed in a suitable reactor and washed with 0.5 M sulfuric acid by pumping it through the scavenger element placed in a suitable reactor at the flowrate of 5 bed volumes per hour for 5 bed volumes. The washing solutions were analysed with ICP-OES to study the amount of Mn leached from the materials. The results are presented below in Table 2.Table 2. Leaching results of Mn02 displayed as a relative leaching compared to the Mn02 powder experiment. For clarity, the powder Mn02 experiment is displayed as 100 %.

[0069] As can be seen from the above results, the Mn02 in powder form shows considerably higher leaching behaviour if compared to the porous scavenger element with the Mn02 stabilized into the porous structure.

[0070] Example 3. Effect on TiO2 leaching behaviour with hydrochloric acid

[0071] Material combination including 50 weight percent of TiO2 (average particle size 50 pm) and 50 weight percent of PA12 (average particle size 50 pm) was prepared into porous scavenger elements with resulting scavenger element density of 0.6 kg / dm3 and cylindrical structure with diameter of 2 cm and height of 2 cm. The porous scavenger element was then washed with 0.5 M sulfuric acid by pumping it through the scavenger element placed in a suitable reactor at the flowrate of 5 bed volumes per hour for 5 bed volumes. For comparison a similar bed volume of TiO2 powder was placed in a suitable reactor and washed with 0.5 M hydrochloric acid by pumping it through the scavenger element placed in a suitable reactor at the flowrate of 5 bed volumes per hour for 5 bed volumes. The washing solutions were analysed with ICP-OES to study the amount of Ti leached from the materials. The results are presented below in Table 3.Table 3. Leaching results of TiO2 displayed as a relative leaching compared to the TiO2 powder experiment. For clarity, the TiO2 is displayed as 100 %.

[0072] As can be seen from the above results, the TiO2 in powder form shows considerably higher leaching behaviour if compared to the porous scavenger element with the TiO2 stabilized into the porous structure.

[0073] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0074] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.INDUSTRIAL APPLICABILITY

[0075] At least some embodiments of the present invention find industrial application in various water intensive industries, battery metal recycling, metal processing and mining industry. Quick adaptation of the technology can be expected because of the improved performance compared to traditional materials used.

Claims

CLAIMS:

1. A method for reducing the leaching of inorganic oxides during treatment with aqueous media by a stepwise process ofi) mixing one or more inorganic oxides possessing appropriate particle size, ideally between 1-300 pm, with organic thermoplastic polymer with particle size, ideally between 5-300 pm, in a weight ratio of inorganic oxide to thermoplastic polymer of 30:70 to 80:20 and byii) preparing the material combination into a porous scavenger element by utilizing SLS 3D printing process where the laser sintering parameters are adjusted to result in a porous body with bulk density, defined as weight of the porous body divided by the volume of the porous body, of 0.4-0.7 kg / dm3.

2. The method according to claim 1, wherein the inorganic oxide is titanium oxide, manganese oxide, nickel oxide, aluminum oxide, iron oxide, zirconium oxide, vanadium oxide, magnesium oxide, molybdenum oxide or a combination thereof.

3. The method according to claim 1, wherein the inorganic oxide is a mixed metal oxide comprising a mixture of cations, wherein the cation mixture of the oxide is selected from lithium, sodium, potassium, magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ammonium or cerium, and the anion is oxide.

4. The method according to claim 1, wherein the inorganic oxide is a mixed metal hydroxide comprising a mixture of cations, wherein the cation mixture of the oxide is selected from lithium, sodium, potassium, magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ammonium or cerium, and the anion is hydroxide.

5. The method according to any one of claims 1 to 4, wherein the SLS 3D printing process step is performed by utilizing energy densities, defined as amount of laser-based energy introduced into a certain surface area, between 4 and 20 mJ / mm2.

6. The method according to any one of claims 1 to 5, wherein the organic thermoplastic polymer is chosen from polyamide, polypropylene, thermoplastic polyurethane, polystyrene or polyether ketone.

7. The method according to any one of claims 1 to 6, wherein the treatment with aqueous media comprises washing by using acidic fluids, salt solutions, oxidizing solutions or alkaline solutions.

8. The method according to claim 7, wherein the porous scavenger element possesses reduced leaching behavior during treatment with acidic fluids chosen from hydrochloric acid, sulphuric acid, nitric acid, phosphoric acid, citric acid, acetic acid or mixture thereof.

9. The method according to claim 7, wherein the porous scavenger element possesses reduced leaching behavior during treatment with salt solutions chosen from sodium chloride, aluminum chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, sodium phosphate, or mixture thereof.

10. The method according to claim 7, wherein the porous scavenger element possesses reduced leaching behavior during treatment with oxidizing solutions chosen from ammonium peroxy di sulfates, sodium peroxy di sulfates, potassium ferrates, or mixture thereof.

11. The method according to claim 7, wherein the porous scavenger element possesses reduced leaching behavior during treatment with alkaline solutions chosen from sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, sodiu bicarbonate, or mixture thereof.

12. The method according to any one of claims 1 to 11, wherein the porous scavenger element has a cylindrical structure with diameter of the cylinder ranging from 2 to 30 cm and height of the cylinder ranging from 2 to 30 cm.

13. The method according to claim 12, wherein the porous scavenger element having a cylindrical structure is placed in a pressure vessel with flexible gaskets in such a manner that aqueous fluids can be pumped through the porous scavenger elements.

14. The method according to any one of claims 1 to 11, wherein the porous scavenger element has a spherical structure with a diameter of 0.5 cm to 5 cm.

15. The method according to claim 14, wherein the porous scavenger elements are placed in a pressure vessel to allow aqueous solution to be pumped through the elements with a spherical structure with a diameter of 0.5 cm to 5 cm.

16. The method according to any of the preceding claims, wherein the SLS 3D printing parameters are selected from the following parameters and / or settings and combinations thereof:• 4-50 W laser power (for CO or CO2 laser)• 2000 - 6000 mm / s laser speed• 0.2-1 mm hatch distance• 0.08-0.8 mm layer height• 166-180 °C powder bed temperature during manufacturing.

17. The method according to any of the preceding claims, wherein the SLS 3D printing parameters are selected from the following parameters and / or settings and combinations thereof:• 5-15 W laser power (for CO or CO2 laser)• 4000-6000 mm / s laser speed• 0.2-0.4 mm hatch distance• 0.08-0.2 mm layer height• 166-174 °C powder bed temperature during manufacturing.

Images