A method for controlling swelling in a scavenger system

Abstract

According to an example aspect of the present invention, there is provided a method for controlling swelling of a SLS 3D printed scavenger element in a scavenger system, in particular for controlling hydration related swelling and optionally also ionic form related swelling of the SLS 3D printed porous bodies in the scavenger system.

Description

A METHOD FOR CONTROLLING SWELLING IN A SCAVENGER SYSTEMFIELD

[0001] The present invention relates to a method for controlling swelling of SLS (Selective Laser Sintering) 3D printed porous bodies of a scavenger element in a scavenger system, in particular for controlling hydration-related swelling and optionally also ionic form related swelling of the SLS 3D printed porous bodies in the scavenger system. The scavenger system finds use in collecting ions and molecules from aqueous fluids.BACKGROUND

[0002] Circulation of materials and streamlining of industrial processes to increase utilization of side streams is a rapidly growing field in industry. In addition to recycling solid materials, there is an increasing interest to reuse and recycle soluble components, such as metals and nutrients, of various water streams. Another important aspect relates to removal of impurities and harmful contaminants from water streams before their future use.

[0003] Ion exchange is a long known chemical process to remove unwanted dissolved ions or to recover valuable ions in water and wastewater by exchanging specific ions for ions that have the same charge. In addition to their macroporous and granular form, ion exchange resins are nowadays available also in small particle size (powdered) form.

[0004] Metal scavenging can be seen as a subspecies of ion exchange where selected (dissolved) metals are recovered from complicated water streams containing different metals in various concentrations. Novel technology for metal scavenging using a selective laser sintered porous body is described in EP3648859A1. By utilization of selective laser sintering (SLS) 3D printing technique, unique internal structure, physical and metal scavenging properties have been achieved.

[0005] However, SLS 3D printed porous bodies for scavenging ions and molecules typically swell (increase in volume) when in contact with aqueous fluids. First, hydration of the initially dry SLS 3D printed porous bodies causes swelling, wherein the degree of swelling mainly depends on the basic composition of the porous body. Secondly, if theSLS 3D printed porous bodies comprise ion exchange resins, further swelling is caused by the change of the ionic form of the ion exchange resins during operation of a scavenger system comprising such SLS 3D printed porous bodies. Naturally also the proportion of the ion exchange resin in the composition of the SLS 3D printed porous body has an effect on swelling.

[0006] Swelling of SLS 3D printed porous bodies during operation may be even 25% or more of the initial dry state volume of the porous bodies. This causes problems during operation of the scavenger system and may even lead to breakdown of the system. Excessive swelling without proper control can lead to a major damage to SLS 3D printed porous bodies, ranging from small horizontal or vertical cracks to complete disintegration of the sintered structure. This is caused when the swelling of the structure separates the sintered particles from each other. In extreme cases, the swelling can even damage any support structures, containers or reactors that are holding the SLS 3D printed porous bodies in place. Opposite effect, shrinkage, can also happen and cause challenges if not accounted for properly. These challenges can range from support structures not operating properly to major problems such as damaging the SLS 3D printed porous bodies.

[0007] Therefore, there exists a need to control the swelling of SLS 3D printed porous bodies in a scavenger system, where the swelling relates to hydration of the porous bodies and also to ionic form related swelling, if the SLS 3D printed porous bodies comprise ion exchange material.SUMMARY OF THE INVENTION

[0008] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0009] The present invention is based on the finding that by providing a scavenger element comprising SLS 3D printed porous bodies, which in a dry state have a density of 0.4-0.7 kg / dm3, it is possible to control swelling during operation of a scavenger system so that the SLS 3D printed porous bodies after hydration have a first wet state volume, which is 100-125% of the volume of the laser 3D printed porous bodies in a dry state.

[0010] The SLS 3D printed porous bodies are thus printed by using SLS 3D printing parameters which provide SLS 3D printed porous bodies having a bulk density of 0.4-0.7 kg / dm3in a dry state. Porous bodies having a bulk density within the range of 0.4-0.7kg / dm3enable to control the swelling caused by hydration within acceptable limits. Correspondingly, it has been found by using energy density values in the range of 4-12 mJ / mm2during SLS 3D printing, it is possible to achieve the above-mentioned bulk densities.

[0011] Thus, the present invention relates to a method for controlling swelling of SLS 3D printed porous bodies of a scavenger element in a scavenger system, wherein the SLS 3D printed porous bodies have a first wet state volume which is 100-125% of the volume of the laser 3D printed porous bodies in a dry state and wherein the SLS 3D printed porous bodies in the dry state have a density which is 0.4-0.7 kg / dm3.

[0012] Considerable advantages are obtained by the invention. First, the method of the present invention enables to maintain a high capacity of the scavenger system by keeping unavoidable swelling due to hydration within acceptable limits, thus avoiding operation disruptions, problems during operation or, in the worst case, breakdown of the scavenger system.

[0013] Second, when the active material comprises ion exchange resin, the high capacity of the active material can be further exploited since the SLS 3D printing allows efficient utilisation of even very small particle ion exchange resins, which further enhances the performance due to inherently porous structure of the resin combined with porous scavenger element structure. The manufacturing method allows utilizing higher operational capacity, smaller tendency for material fouling and faster reaction kinetics of the smaller particle ion exchange resins, while also negating negative effects arising from potential increase in back pressure or particle swelling that can be challenges when dealing with small particular matter.

[0014] Further, in some embodiments the method of the invention enables to control also a second wet state volume, in addition to the first wet state volume. Controlling the first and second wet state volume of the SLS 3D printed porous bodies provides additional process benefits. First wet state hydration, caused by hydration of the selected scavenger body, is controlled to maintain openly porous structure caused by the swelling combined with adequate pressure against the gaskets to maintain sealing effect of the gaskets that guide the waterflow through the scavenger body. Second wet state swelling and shrinking, caused for example by the material combination, manufacturing parameters, pore structure and particle size, is controlled to gain process benefits such as proper backpressure toincrease mass transfer as well as combined shrinking and swelling effect during sequential washes allowing the porous structure to also discharge solids and other foulants more effectively.

[0015] Further features and advantages of the present technology will appear from the following description of some embodiments.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGURE 1 illustrates an example of a scavenger system, capable of being used according to at least some embodiments of the method of the present invention. The scavenger system according to Figure 1 comprises SLS 3D printed porous bodies and flexible gaskets in a housing.DETAILED DESCRIPTION OF THE INVENTION

[0017] DEFINITIONS

[0018] In the present context, the term “scavenger” refers generally to a solid porous physical body capable of capturing desired objects, such as ions and molecules, from a target fluid. The term may thus refer also to a SLS 3D printed porous body or several SLS 3D printed porous bodies.

[0019] As used herein, the term “scavenger element” comprises one or several SLS 3D printed porous bodies, optionally together with flexible gaskets.

[0020] In the present context, a “scavenger system” comprises a scavenger element and a housing for the scavenger element, wherein the housing also comprises an inlet or several inlets for incoming aqueous medium and an outlet for outgoing aqueous medium.

[0021] As used herein, “swelling” refers to a change of the volume of a particle or a physical body compared to its initial volume. Within the present context, swelling refers in particular to an increase of a volume of a SLS 3D printed porous body or a scavenger element formed of SLD 3D printed porous bodies, due to hydration only or due to both hydration and change of ionic form, if ion exchange material is present in the SLS 3D printed porous body. However, swelling may also refer to a decrease of a volume of a SLS 3D printed porous body or a scavenger element, in which case the change of volume (expressed in percentages) may have a negative value.

[0022] Within the present context, a “dry state” refers to the state or condition of SLS 3D printed porous bodies after they have been manufactured by SLS 3D printing but before they have been in contact with water or aqueous medium.

[0023] A “first wet state volume” refers to the volume of the initially dry SLS 3D printed porous bodies after they have been exposed to contact with water or aqueous medium.

[0024] When SLS 3D printed porous bodies comprise ion exchange resin as an active material, they may have a “second wet state volume”, which refers to the volume of SLS 3D printed porous bodies after a change of ion form of the ion exchange resin during operation of the scavenger system. In some embodiments, there may be several “second wet state volumes”. A second wet state volume may be larger, equal or smaller than a first wet state volume. Typically, a second wet state volume changes dynamically depending on the chemical reactions occurring during certain process steps.

[0025] Within the present context, “active material” refers to material, which is used for SLS 3D printing of the porous bodies and which may actively capture or scavenge targeted objects from an aqueous fluid. Within this disclosure, “active material” may be selected from ion exchange materials and adsorbents. Typically, the active material comprises ion exchange resin. As known to persons skilled in the art, ion exchange resins comprise functional groups with ion exchange properties.

[0026] ‘Dimensions” refer to both vertical and horizontal dimensions.

[0027] “Operation” of the scavenger system refers to a situation wherein a target aqueous fluid is fed through a scavenger system.

[0028] “Backpressure” refers to the resistance to the desired flow of fluid through the scavenger system. It is commonly also observed as pressure drop over the scavenger system.

[0029] ‘A target aqueous fluid” refers to an aqueous solution to be treated by the scavenger system.

[0030] ‘SLS 3D printing parameters” refer to settings of a 3D printer when printing SLS 3D printed porous bodies. Typically said printing parameters include settings such as power and speed of the laser, hatch distance (distance between two consecutive laserbeams), height of each printed layer, and temperature of the powder bed during manufacturing.

[0031] ‘Powder” refers to the materials used in the manufacture of porous bodies by SLD 3D printing. Typically, the materials comprise at least a base polymer. In the present invention, said materials comprise a base polymer and active material.

[0032] When ion exchanger resin is present as an active material, it may have a degree of crosslinking. A degree of crosslinking in connection with ion exchange material or ion exchange resin refers to the degree of covalent bonds linking polymer chains to each other.

[0033] A “bed volume” means the dry state volume of the scavenger element.

[0034] ‘Bulk density” refers to the weight of the many particles of the material divided by the bulk volume. In the present case, bulk density is calculated by weighing the manufactured porous body and dividing the weight with the total volume of the scavenger body obtained by measuring the outer dimensions of the said body.

[0035] “Energy density” indicates how much energy a laser produces on a given surface area. This is calculated in practice via the laser power, laser speed and hatch distance of adjacent laser lines. It can also be measured indirectly by measuring the laser power output of a 3D printer. In the present case, energy density may be calculated as follows: Energy density = laser power / (laser speed x hatch distance). In some cases, equipment with higher laser power can be utilized and in such scenario other parameters are compensated in such a way that desired energy density is reached.

[0036] As stated above, it has been found that by adjusting the bulk density of the SLS 3D printed porous bodies to a range of 0.4-0.7 kg / dm3, it is possible to control the swelling of the porous bodies during the operation of a scavenger system. Preferably, flexible gaskets are also included in the scavenger element to further increase controllability and flexibility of the system.

[0037] Thus, in the present method for controlling swelling of SLS 3D printed porous bodies of a scavenger element in a scavenger system the SLS 3D printed porous bodies have a dry state density of 0.4-0.7 kg / dm3and a first wet state volume which is 100-

[0038] Typically, the scavenger bulk density has an inverse correlation with an increase in a first wet state volume and a direct correlation with backpressure produced when pumping water through the scavenger element. On the other hand, backpressure may thus be influenced by the bulk density of the SLS 3D printed porous bodies.

[0039] In embodiments, the SLS 3D printed scavenger element is formed of SLS 3D printed porous bodies, which comprise or consist of active material and a base polymer. Typically, the SLS 3D printed porous bodies comprise active material and a base polymer in a weight ratio of active material to base polymer of 30:70 - 60:40, preferably in a weight ratio of about 50:50.

[0040] Typically, the SLS 3D printed porous bodies are composed of material having a particle size ranging from 0.1 to 500 pm, preferably 1-100 pm, defined by laser diffraction methods using for example Malvern Mastersizer 3000 particle size analyzer according to ISO 13320:2020. Particle size may have an effect on the first wet state volume of the SLS 3D printed porous bodies, as the first wet state volume change is determined partly by the degree of hydration of the active material and changing the particle size causes unproportional change in the observed volume change during swelling - meaning that certain materials as small particles might for example show larger volume change relative to the particle size than they would as larger particles. Particle size may also play a role in the second wet state volume change.

[0041] In one embodiment, each SLS 3D printed porous body in a dry state has dimensions, which are 5-50 cm, preferably about 10-20 cm. Typically, the scavenger element comprises or consists of several SLS 3D printed porous bodies, optionally together with flexible gaskets. Thus, the scavenger element may comprise for example 2-10 or 3-5 SLS 3D printed porous bodies. In some embodiments it may be possible that the scavenger element consists of a single porous body. However, preferably the scavenger element comprises at least 2 to 3 SLS 3D printed porous bodies.

[0042] When the active material in the SLS 3D printed porous bodies comprises ion exchange material, more particularly ion exchange resin(s), the scavenger element during operation of the scavenger system may have a second wet state volume, which is due to the volume changes caused by the change of ionic form. Typically, the second wet state volume is 85-115% of the first wet state volume. In some embodiments, it has been foundthat a second wet state volume nearly equal to the first wet state volume is preferred for higher recovery of metals.

[0043] Ion exchange materials typically belong to group of strong cation exchange resins (SAC), weak cation exchange resins (WAC), strong base anion exchange (SBA), weak base anion exchange (WBA) or chelating exchange resins. More specifically, the functional groups in the ion exchange resins may belong to group of carboxylates, primary amine or ammonium, secondary amine or ammonium, tertiary amine or ammonium, sulphates, sulfonic acids, phosphonic acids, diethanolamines, thioureas, thiols, thiouronium, ethylenediaminetetraacetic acid or any combination of these.

[0044] When the active material in the SLS 3D printed porous bodies comprises ion exchange material, the choice of the ion exchange resin-base polymer combination will have an effect on the second wet state volume. Typically, ion exchange materials with different functional groups inherently possess different swelling and shrinking behaviour based on their ionic form. However, this behaviour may now be controlled in SLS 3D printed scavengers in several ways: 1) The ratio of ion exchange material to the base polymer allows tailoring material combinations so that the volume changing behaviour of the combination is limited. 2) Manufacturing parameters provide vast control over the swelling behaviour as the level of sintering or energy density, controlled by process parameters such as laser power, hatch distance and laser speed, also affects the possible degree of swelling and shrinking observed. The amount of sintering (via energy density) also controls how embedded the active material particles are into the base polymer particles, which alters their second wet state volume change. 3) Pore structure or porosity, which may be altered during manufacturing of the SLS 3D printed porous bodies, may also affect second wet state volume. Typically, manufacturing parameters providing higher energy density provide the SLS 3D printed porous bodies with minor porosity and vice versa. On the other hand, pore structure may be adjusted by hatch distance parameters. A more openly porous structure allows for more swelling and shrinkage into the direction of the open pores of the structure. 4) Particle size may also play a role in controlling the swelling as changing the particle size of the material alters the swelling and shrinking behaviour unproportionally compared to the change in particle size.

[0045] In some embodiments, the method for controlling swelling of a SLS 3D printed scavenger element in a scavenger system may comprise or consist of the following steps:- providing a target aqueous fluid;- selecting active material, a base polymer and their weight ratio based on properties of the target aqueous fluid;- selecting SLS 3D printing parameters;- printing porous bodies by SLS 3D printing, wherein the SLS 3D printed porous bodies comprise the active material and the base polymer;- providing a housing for the scavenger system;- selecting at least one flexible gasket and providing said gasket(s) in the housing;- filling the housing of the scavenger system with the 3D laser printed porous bodies to form the scavenger element;- feeding the target aqueous fluid through the scavenger system; and eluting scavenged material from the scavenger system with an elution solution, which regenerates the scavenger element.

[0046] Target aqueous fluids typically comprise of industrial wastewaters, process waters, industrial side streams, hydrometallurgical process waters, mining waters, acidic mining drainages and other industrial water streams.

[0047] The scavenger system comprises a housing, in which the SLS 3D printed porous bodies are inserted. In some embodiments, the housing may have a height and width in the range of from 10 to 500 cm. As stated above, the SLS 3D printed porous bodies in a dry state typically have (horizontal and / or vertical) dimensions in the range of 5-50 cm, preferably about 10-20 cm. Preferably, said SLS 3D printed porous bodies also include a hole, typically having a diameter of 2-5 cm, such as 3 cm, through the middle of the porous body.

[0048] When the housing is filled with the SLS 3D printed porous bodies, flexible gasket(s) are also included between the SLD 3D printed porous bodies. Such flexible gaskets provide a further opportunity to obtain additional space for possible swelling of the SLS 3D printed porous bodies if considered necessary or as a precaution. The flexible gasket(s) preferably constitute 1 to 20% of the height of the housing.

[0049] The housing of the scavenger system comprises an inlet or several inlets for incoming aqueous fluid and an outlet for outgoing aqueous fluid. The scavenger element inside the housing may comprise a central opening configured to discharge the outgoing aqueous fluid to the outlet of the housing. In a preferred embodiment, the incoming aqueous fluid flows in horizontal direction through the scavenger element.

[0050] In one preferred embodiment, the active material of the SLS 3D printed porous bodies is composed of an ion exchange resin, preferably an ion exchange resin having a degree of crosslinking of 2-20%.

[0051] The passive material or the base polymer of the SLS 3D printed porous bodies is typically a thermoplastic polymer, preferably a polyamide, polypropylene, thermoplastic polyurethane or polystyrene.

[0052] The SLS 3D printing parameters are adjusted to receive the required bulk density values for controlling the swelling of SLS 3D printed porous bodies. In some embodiments, the SLS 3D printing parameters are adjusted to provide also the desired energy density values. Typically, parameters such as power and speed of the laser, 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:• 4-20 W laser power• 2000 - 6000 mm / s laser speed• 0.2-1 mm hatch distance• 0.08-0.2 mm layer height• 100-185 °C, typically 166-180 °C (for example in case of polyamide 12) powder bed temperature during manufacturingIn some embodiments, the SLS 3D printed porous bodies are printed with the following printing parameters to obtain a bulk density of 0.4-0.7 kg / dm3and optionally an energy density of 4-12 mJ / mm2: 4-20 W laser power, 2000 - 6000 mm / s laser speed, and 0.2-1 mm hatch distance.

[0053] By the present method is possible to efficiently remove and / or recover metals, metal ions and nutrient ions from aqueous fluids. Typically, the present method isused for removing and / or recovering heavy metals, battery metals, noble metals or combinations thereof from aqueous fluids.

[0054] In some embodiments the aqueous fluids are fed through the scavenger system with a flow rate, which is 20-2000 bed volume / hour, typically 25-500 bed volume / hour.

[0055] 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.

[0056] 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 present invention. 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.

[0057] 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.

[0058] 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. Oneskilled 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

[0059] Example 1. Effect of bulk density on first wet state volume of the SLS 3D printed scavenger element

[0060] The first wet state volumes and the concurrent backpressure caused by the scavengers manufactured with bulk densities of 0.5, 0.6 and 0.7 kg / dm3, energy densities of 6.1, 8.0 and 9.5 mJ / mm2, respectively, and material composition of 50 w% of ion exchange material and 50 w% of polyamide- 12 with dry state dimensions of 15 cm width and 15 cm of height with 3 cm diameter hole through the middle were compared by placing them in a suitable housing and by pumping water through the system at flow rate of 300 dm3 / h.Table 1. First wet state volume change and backpressure differences of different bulk density scavengers in Na+ ionic form

[0061] As can be seen from the above results, the scavenger bulk density has inverse correlation with first wet state volume increase and direct correlation with backpressure produced when pumping water through the scavenger element. The result demonstrates the importance of correctly utilizing the first wet state volume change when using different types of scavenger elements.

[0062] Example 2. Effect of ionic form on second wet state volume of the SLS 3D printed scavenger element

[0063] The second wet state volumes and the concurrent backpressure caused by thescavengers manufactured with bulk density of 0.6 kg / dm3and energy density of 8 mJ / mm2with dry state dimension of 15 cm width and 15 cm of height with 3 cm diameter hole through the middle were compared in different ionic forms by placing them in a suitable housing and by converting them into the corresponding ionic form by treating them with 20 dm3of 5 % chloride salt solution of the specific cation for the test followed by pumping water through the system at flow rate of 300 dm3 / h.Table 2. First wet state and second wet state volume change and backpressure differences of different ionic forms. Na+ is the standard ionic form used as starting point in the test and the change in ionic form happens between the first and second wet state.

[0064] As can be seen from the above results, controlling the second wet state volume plays a critical role in performance of the scavenger. This effect is in-part due to change in hydrated ionic radii compared with the flexibility of the scavenger element and materials used for manufacturing said elements.

[0065] Example 3. Effect of second wet state volume of the SLS 3D printed scavenger element on the metal recovery efficiency of the said elements

[0066] The recovery efficiency and the concurrent backpressure caused by the scavengers manufactured with bulk density of 0.55 kg / dm3and energy density of 7.4 mJ / mm2with dry state dimension of 15 cm width and 15 cm of height with 3 cm diameter hole through the middle were compared in different ionic forms by placing them in a suitable housing and by pumping 100 Bed Volumes (meaning the dry state volume of the scavenger element) of 200 mg / L Cu2+ solution at pH 4 through the system at flow rate of 300 dm3 / h.Table 3. Recovery efficiencies of scavenger elements with similar bulk densities in different second wet state volumes. Na+ is the standard ionic form used as starting point in the test. Backpressure measurements are taken at the start of the test, so the ionic statechange to Cu would not affect the results.

[0067] As can be seen from the above results, the second wet state of the scavenger element also leads to massive differences in metal recovery efficiency. From Table 3, we can see that the scavenger element with larger second wet state volume shows higher ability for Cu recovery compared to the scavenger element with smaller wet state volume.

[0068] Example 4. Effect of bulk density on first wet state volume of the SLS 3D printed scavenger element with different material ratios

[0069] The first wet state volumes and the concurrent backpressure caused by the scavengers manufactured with bulk densities of 0.6 kg / dm3and energy density of 7.8 mJ / mm2and varying material compositions with dry state dimensions of 15 cm width and 15 cm of height with 3 cm diameter hole through the middle were compared by placing them in a suitable housing and by pumping water through the system at flow rate of 300 dm3 / h.Table 4. First wet state volume change and backpressure differences of different material ratio scavengers in Na+ ionic form

[0070] As can be seen from the above results, the scavenger material ratio has direct correlation with first wet state volume increase with backpressure increasing more withscavengers including more active material compared to base material. The result demonstrates the importance of understanding the effect of different material choices on the first wet state volume change and albeit not shown here, on the second wet state volume change.

[0071] 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.

[0072] 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

[0073] At least some embodiments of the present invention find industrial application in various water intensive industries, such as municipal water treatment, process, mining and recycling industries. Quick adaptation of the technology can be expected because of the improved performance and lower operating and capital costs compared to currently available metal scavenging solutions.CITATION LISTPatent LiteratureEP3648859A1Non-Patent Literature

Claims

CLAIMS:

1. A method for controlling swelling of SLS (Selective Laser Sintering) 3D printed porous bodies of a scavenger element in a scavenger system, wherein the SLS 3D printed porous bodies have a first wet state volume which is 100-125% of the volume of the laser 3D printed porous bodies in a dry state, wherein the SLS 3D printed porous bodies in a dry state have a bulk density which is 0.4-0.7 kg / dm3.

2. The method according to claim 1, wherein the SLS 3D printed porous bodies comprise active material and a base polymer, preferably in a weight ratio of active material to base polymer of 30:70 - 60:40, more preferably about 50:50.

3. The method according to claim 1 or 2, wherein each of the SLS 3D printed porous bodies in a dry state has dimensions of 5-50 cm, preferably about 10-20 cm.

4. The method according to any one of the preceding claims, wherein the SLS 3D printed porous bodies during operation of the scavenger system have a second wet state volume, which is 85-115% of the first wet state volume.

5. The method according to any one of the preceding claims, comprising the steps of- providing a target aqueous fluid;- selecting active material, a base polymer and their weight ratio based on properties of the target aqueous fluid;- selecting SLS 3D printing parameters;- SLS 3D printing porous bodies, wherein the SLS 3D printed porous bodies comprise the active material and the base polymer;- providing a housing for the scavenger system;- selecting at least one flexible gasket and providing said gasket(s) in the housing;- filling the housing of the scavenger system with the 3D laser printed porous bodies and the optional flexible gasket(s) to form the scavenger element;- feeding the target aqueous fluid through the scavenger system; and- eluting scavenged material from the scavenger system with an elution solution, which regenerates the scavenger element.

6. The method according to claim 5, wherein the housing has a height and width in the range of from 10 to 500 cm.

7. The method according to claim 5 or 6, wherein the housing of the scavenger system comprises flexible gasket(s) to provide 1 to 20% of the height of the housing.

8. The method according to any one of claims 5 to 7, wherein the housing of the scavenger system comprises an inlet (2) for incoming aqueous fluid and an outlet (3) for outgoing aqueous fluid and the scavenger element comprises a central opening (4) configured to discharge the outgoing aqueous fluid to the outlet of the housing, and wherein the incoming aqueous fluid flows in horizontal direction through the scavenger element.

9. The method according to any one of claims 2 to 8, wherein the active material is an ion exchange resin, preferably an ion exchange resin having a degree of crosslinking of 2-20%.

10. The method according to any one of claims 2 to 9, wherein the base polymer is a thermoplastic polymer, preferably a polyamide, polypropylene, thermoplastic polyurethane or polystyrene.

11. The method according to any one of the preceding claims, wherein the SLS 3D printed porous bodies are SLS 3D printed with printing parameters providing energy density of 4- 12 mJ / mm2.

12. The method according to any one of the preceding claims, wherein the SLS 3D printed porous bodies are SLS 3D printed with printing parameters comprising one or more of the following:• 4-20 W laser power• 2000 - 6000 mm / s laser speed• 0.2-1 mm hatch distance• 0.08-0.2 mm layer height• 100-185 °C, typically 166-180 °C powder bed temperature during manufacturing13. The method according to any one of the preceding claims, wherein the scavenger system is used for removing and / or recovering metals and nutrient ions from an aqueous fluid.

14. The method according to any one of the preceding claims, wherein the scavenger system is used for removing and / or recovering heavy metals, battery metals, noble metals or combinations thereof from an aqueous fluid.

15. The method according to any one of the preceding claims, wherein an aqueous fluid is fed through the scavenger system with a flow rate, which is 10-2000 bed volume / hour, typically 25-500 bed volume / hour.

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