Device and method for treating water

Abstract

The present invention relates to a device and method for treating water. In an embodiment, the present invention provides an adsorbent for treating water, the adsorbent is made of a composite material comprising a porous support structure and a carbon-based material, the carbon-based material disposed on or within the porous support structure, and wherein the composite material removes an amount of boron present in the water being treated. The method of removing an amount of boron present in an aqueous solution comprises (a). contacting the boron removal medium with the aqueous solution; and (b). separating the boron removal medium from the aqueous solution.

Description

DESCRIPTIONTITLE OF THE INVENTION: DEVICE AND METHOD FOR TREATING WATERFIELD OF THE INVENTION

[0001] The invention relates to a device and method for treating water. In particular, it relates to a device and method for removing boron, or boron ions, from, in an embodiment, brackish water. More particularly, it relates to a device and method for removing boron from brackish water.BACKGROUND OF THE INVENTION

[0002] Boron is a naturally occurring element in the environment. Its presence comes mainly in the form of boric acid (H3BO3) or borate ions (B(OH)4-, B4O72; H3BO2) or salts. Its aqueous solution plays an important role in many application fields, e.g. in a middle-scale semiconductor factory, million tons of pure water with ppb (parts per billion) level of boron is daily consumed during the manufacture process, higher boron concentration might cause defects due to the p-type dopant in semiconductor chip manufacturing, and leak might happen.

[0003] In irrigation water, boron content must not exceed 1 mg / L (parts per million). Its deficiency and excess are harmful to the normal growth of plants. On one hand, boron deficiency may reduce absorption of calcium, magnesium and phosphorus in the growth and functioning of plants. On the other hand, excess boron can result in dwarfing or death of plants.

[0004] For potable water, the World Health Organization (WHO) recommends a guideline concentration of boron up to 2.4 mg / L level in 2011 . Increased boron content causes problems in cardiovascular, coronary, nervous and reproductive systems. It is particularly dangerous for pregnant women to take excess of boron because of the risk of birth pathology.

[0005] The concentration of boron is approximately 5 mg / L in seawater. In seawater desalination, reverse osmotic membrane, capacitive desalination, and electro-dialysis desalination are the most popular technologies. However, none of them can efficiently remove boron from seawater due to its small size and uncharged species of boric acid at pH 8.4. In this case, additional post-treatment processes are needed to remove boron during the seawater desalination. These post-treatment processes include electrocoagulation, chemical precipitation, ion exchange processes, and liquid-liquid extraction. However, most of thesemethods are inefficient in solutions of low boron concentrations or adjustment of pH is required.

[0006] Accordingly, there remains a need to provide for an improved boron removal medium and method that overcome, or at least alleviate the above drawbacks by controlling and keeping the boron concentration within the applicable limit.

[0007] Due to the increasing scarcity of suitable quality water for drinking, industrial, and agricultural purposes, there is a pressing need to enhance freshwater production from unconventional sources like seawater and brackish water. While reverse osmosis (RO) has been extensively developed for seawater desalination, its energy demand doesn't scale efficiently with decreasing feed concentration, such as in brackish water (second RO) plants.

[0008] Despite brackish water being less concentrated than seawater, the energy input required for desalination remains high. As desalinating brackish water is a promising solution, technologies that have energy demands proportional to feed concentration are more desirable than RO. Electrochemical processes like capacitive deionization (CDI) offer a promising solution due to their energy demand being tied to salt removal, rather than water volume. CDI is scalable and suitable for brackish water desalination or polishing in combination with other treatments.

[0009] One critical challenge in brackish water desalination is the removal of boron, an amphoteric contaminant prevalent in seawater as boric acid (H3BO3). Traditional desalination methods (RO and CDI) struggle with efficient boron removal due to its uncharged state. High levels of boron are detrimental to human health and plant growth, necessitating stringent concentration limits to meet the standards of both drinking water and irrigation water with a minimum limit of 0.5 mg / L. This requirement is still difficult to be reached for several conventional deboronation treatment processes. Specifically, boron removal needs increased pH technology to transform the H3BO3 into B(OH)4‘ anion, this process often yields high boron concentrations in effluent and an increased capital-operational expenses. Consequently, efficient and sustainable boron removal techniques are needed to control the boron level (<0.5 mg / L).

[0010] Adsorption serves as the primary mechanism and deems to be the most effective method for the boron removal in aqueous solutions, given its simplicity and effectiveness at neutral pH levels even at low B concentrations though adsorbents need to be regenerated as well. During the adsorption, boron removal is achieved through the selective formation of borate complexes based on covalent or ionic bonds between boron species and functional groups, such as hydroxyl groups (-OH), present on the adsorbent's surface. While ion exchange is effective, it necessitates improved regeneration methods to reduce chemicalusage. Similarly, expensive membrane filtration results in concentrated boron in backwash effluent, posing potential discharge issues.

[0011] To address this concern, the focus has shifted towards efficient, boron-specific adsorbents. Notably, functionalized carbon-based materials like graphene oxide (GO) have gained prominence due to their availability, eco-friendliness, and high adsorption capacity in comparison to commercial ion exchange resins.

[0012] There is potential of using nitrogen-doped graphene oxide (NGO) for seawater boron removal. With an impressive adsorption capacity of 6.55 mg / g, NGO demonstrates remarkable performance, as indicated by the Langmuir adsorption isotherm with a capacity of 58.7 mg / g. This enhanced capacity arises from stronger bonding between boron compounds and NGO's adjacent hydroxyl groups of quaternary nitrogen doping. Notably, NGO can be conveniently regenerated through acid treatment, contributing to its appeal as an adsorbent.

[0013] Despite its high potential, NGO faces limitations hindering commercial application. Firstly, as a two-dimensional (2D) material, NGO is prone to stack and block the water transport pathway, reducing the boron removal rate and increasing the cost of the final boron rejection column. Secondly, previous methods of collecting NGO employed repeated cycles of water washing and centrifugation. Nevertheless, this technique presented difficulties in achieving a proper separation between the NGO and the aqueous solution, resulting in a modest yield of approximately 30%. This yield was additionally impacted by elevated material costs linked to the process. Thirdly, the inherent property of NGO to readily expand due to its low density has led to a notable upsurge in the usage of chemicals required for adsorbent regeneration. In addition to the points mentioned earlier, the pronounced superhydrophilicity of pure NGO poses a considerable obstacle in effectively separating water from mixed solutions containing the adsorbent. This challenge consequently hampers the overall production yield of purified water and drives up the expenses related to the adsorbent.

[0014] In recent times, there has been a significant breakthrough in the utilization of nitrogen-doped graphene oxide (NGO) nanomaterials for efficiently removing or reducing boron levels in neutral aqueous solutions. This efficacy arises from the ability of nitrogen- doped sites to modify local pH levels. Notably, boron is present in the form of borate ions (B(OH)4‘, B4O72; H3BO2;) rather than boric acid (H3BO3) in the adsorbed sites. The enhanced removal of boron is facilitated by the charged nature and larger size of borate ions compared to boric acid. This phenomenon can be attributed to the robust bonding between boron compounds and NGO's hydroxyl groups, particularly those adjacent to quaternary nitrogen. The stronger interaction at these sites contributes to the increased efficiency of boron removal.

[0015] While NGO holds great potential, powdery NGO adsorbents face several challenges in practical column adsorption systems. Their small particle size can lead to compact layers in the column, increasing flow resistance and pressure drop, which reduces flow rates and raises costs. These adsorbents also tend to aggregate, causing blockages and material loss, and may require additional filtration devices at the column outlet, complicating the system. Regenerating powdery adsorbents is difficult due to issues with separation and potential agglomeration, which affects performance.

[0016] Additionally, uneven distribution can create dead zones and short-circuiting flow paths, impacting overall efficiency. To address these issues, powdery adsorbents may need to be pelletized or combined with other materials to improve their practicality and stability in column systems.

[0017] To counteract these limitations, it becomes crucial to pioneer the development of advanced, cost-effective, and large-scale NGO-based composites, thereby mitigating the need for excessive chemical consumption during the regeneration process.SUMMARY OF THE INVENTION

[0018] As indicated above, nitrogen-doped graphene oxide (NGO) exhibits significant selectivity for boron species in water. Despite its extensive potential, the commercial application of NGO faces several substantial challenges. In practical column adsorption systems, powdery NGO adsorbents face several challenges. Their small particle size can lead to compact layers in the column, increasing flow resistance and pressure drop, which reduces flow rates and raises costs. These adsorbents also tend to aggregate, causing blockages and material loss, and may require additional filtration devices at the column outlet, complicating the system. Regenerating powdery adsorbents is difficult due to issues with separation and potential agglomeration, which affects performance. Additionally, uneven distribution can create dead zones and short-circuiting flow paths, impacting overall efficiency.

[0019] Therefore, to improve practical application outcomes, powdery adsorbents may need to be processed into pelletized or composite forms to enhance their practicality and stability in column adsorption systems.

[0020] This invention provides a new method for assembling NGO onto a melamine sponge skeleton to form a composite material based on NGO (NGO@MS). This method offers three major advantages: (i) The porous skeleton of MS provides sites and space for efficient dispersion of NGO, significantly reducing layer stacking and thereby enhancing the utilization of NGO's active sites and water flux; (ii) Through interactions between oxygen-containinggroups (-COOH / -OH) on NGO and amino groups (-NH2) on MS, NGO is in-situ assembled onto the MS skeleton. The resulting NGO@MS composite exhibits high stability and incorporates the flexible characteristics of MS, which not only extends the lifespan of the adsorbent but also reduces the design requirements for the adsorption column; (iii) MS’s inherent strong acid and base resistance ensures that the NGO@MS adsorbent maintains high stability and mechanical strength during regeneration.

[0021] This enhancement improves the separation efficiency between the adsorbent and water, while maintaining high boron removal efficiency. Using NGO@MS as an adsorbent not only meets Singapore's stringent water quality standards (B < 0.5 mg / L) but also offers flexible and highly stable regenerability. Moreover, the chemical consumption during the regeneration of NGO@MS is comparable to that of powdery NGO. This advanced column adsorbent has significant practical application prospects, achieving strict water quality standards while minimizing design costs due to its flexible features and demonstrating excellent durability.

[0022] In one aspect, the present invention provides an adsorbent for treating water, the adsorbent is made of a composite material comprising a porous support structure and a carbon-based material, the carbon-based material disposed on or within the porous support structure, and wherein the composite material removes an amount of boron present in the water being treated.

[0023] By “porous support structure”, it is meant to refers to any solid framework or skeletal framework having a plurality of interconnected pores, channels or voids that provide a three- dimensional network suitable for accommodating, dispersing or supporting other materials.

[0024] The porous support structure may be in the form of a sponge, foam, aerogel, scaffold, membrane, or any other structure exhibiting porosity that enables mass transfer of fluids and the immobilisation of active materials within or on its surfaces.

[0025] The porous support structure may be formed from any suitable organic or inorganic material, including but not limited to polymeric materials such as melamine-formaldehyde, polyurethane, polyimide, polyethylene, polypropylene, or polyacrylonitrile, or from inorganic materials such as silica, alumina, or ceramics.

[0026] The pores of the support structure may be open or closed, and may vary in size, shape and distribution, provided that the overall structure maintains sufficient mechanical integrity and accessible surface area to support the deposition or assembly of the nitrogen- doped carbon material.

[0027] In various embodiments, the porous support structure may be a polymer. More specifically, the porous support structure is a melamine sponge skeleton.

[0028] In various embodiments, the carbon-based material is graphene oxide. The term “composite material” may be used interchangeably with the term “boron removal medium”.

[0029] The carbon-based boron removal medium may comprise at least one hydroxyl group and at least one pyridinic nitrogen, or pyrrolic nitrogen, or graphitic nitrogen, or amine group. In other words, there is always one or more hydroxyl groups in the carbon-based boron removal medium.

[0030] In various embodiments, the carbon-based material may comprise at least two hydroxyl groups and at least one pyridinic nitrogen, or pyrrolic nitrogen, or graphitic nitrogen, or amine group.

[0031] Preferably, the carbon-based material comprises at least one of graphene, graphite, graphene oxide, carbon nanotube, activated carbon, lonsdaleite, fullerene, carbon fiber, carbon black, charcoal, and amorphous carbon.

[0032] More preferably, the carbon-based material is doped, such as nitrogen-doped.

[0033] In certain preferred embodiments, the carbon-based material may comprise nitrogen-doped (N-doped) graphene oxide or N-doped reduced graphene oxide. In one exemplified embodiment where N-doped graphene oxide is used as the boron removal medium, the boron absorption capacity can be up to 6.154 mg / g for N-graphene oxide synthesized at 50 °C hydrothermal treatment.

[0034] The hydroxyl group and the pyridinic nitrogen, or pyrrolic nitrogen, or graphitic nitrogen, or amine group of the carbon-based material may be directly covalently bound to the carbon-based material. Alternatively, the hydroxyl group and the pyridinic nitrogen, or pyrrolic nitrogen, or graphitic nitrogen, or amine group of the carbon-based material may be covalently bound to the carbon-based material via a linker small molecule.

[0035] In various embodiments, the graphene oxide is self-assembled N-doped graphene oxide.

[0036] In various embodiments, the graphene oxide is nitrogen doped.

[0037] The N-doped graphene oxide may comprise at least one hydroxyl group and at least one pyridinic nitrogen, or pyrrolic nitrogen, or graphitic nitrogen, or amine group. The hydroxyl group may come from the oxidation of the graphite material. Alternatively, the hydroxyl group may come from the transformation of a function group, preferably a carboxyl group, or carbonyl group. In other embodiments, the hydroxyl group may come from another small molecule comprising a hydroxyl group coupled to a carbon material.

[0038] In various embodiments, the nitrogen doping may come from the hydrothermal treatment of carbon materials with ammonia in an autoclave.

[0039] In further embodiments, the nitrogen doping may come from ammonia or nitrogen plasma treatment of carbon materials.

[0040] In yet further embodiments, the nitrogen doping may come from a direct synthesis of nitrogen doping of carbon materials.

[0041] In other embodiments, the nitrogen doping may come from N+ ion-irradiated carbon materials.

[0042] In still further embodiments, the nitrogen doping may come from a thermal treatment of carbon materials with ammonia.

[0043] Alternatively, the nitrogen doping may come from a chemical treatment of carbon materials, preferably hydrazine, or other small molecule with nitrogen or amine group coupled to a carbon material.

[0044] In various embodiments, the composite material is a melamine sponge skeleton and nitrogen-doped graphene oxide composite.

[0045] In various embodiments, the mass ratio of melamine sponge skeleton to nitrogen- doped graphene oxide is about approximately 1 :4.

[0046] In another aspect of the invention, there is provided a water treatment device comprising an adsorbent according to an aspect of this invention.

[0047] In yet another aspect of the invention, there is provided a method of removing an amount of boron present in an aqueous solution, the method comprising: (a), contacting a boron removal medium with the aqueous solution; and (b). separating the boron removal medium from the aqueous solution, wherein the boron removal medium is a medium according to an earlier aspect of this invention.

[0048] In various embodiments, the concentration of the boron removal medium to aqueous solution is 4 mg / ml, 6 mg / ml, 8 mg / ml, or 10 mg / ml.

[0049] In various embodiments, the separating comprises centrifuging or filtering the aqueous solution, or the separating comprises passing water through the boron removal medium.

[0050] Another advantage of the present boron removal medium is the ease of regenerating a used medium. Accordingly, another aspect of the invention relates to a method of regenerating a used boron removal medium. The method comprises contacting the used boron removal medium with an acid, followed by rinsing the used boron removal medium with deionized water.

[0051] Suitable acids include, but not limited to, sulfuric acid (H2SO4) and hydrochloric acid (HCI).

[0052] The presently disclosed boron removal medium and method of removing or reducing the amount of boron present in an aqueous solution may be extended to a method of detecting and quantifying the amount of boron present in an aqueous solution.

[0053] Advantageously, this invention contributes to the advancement in the field of water treatment, being both academically insightful and industrially applicable.BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The invention will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:

[0055] Figure 1 shows The synthesis of NGO@MS and corresponding to the images of MS during each step;

[0056] Figure 2 shows SEM results of MS (a) and NGO@MS (b-c);

[0057] Figure 3 shows results from evaluating the Boron removal performance: optimizing the ratio of adsorbent (NGO@MS) to feed water;

[0058] Figure 4 shows the stability of NGO@MS soaked in regenerants;

[0059] Figure 5 shows results from evaluating the output water quality after multi-cycles regeneration; and

[0060] Figure 6 shows the high physical and chemical stability of NGO@MS adsorbent after 15 cycles regeneration.DETAILED DESCRIPTION OF THE INVENTION

[0061] Other embodiments are within the following claims and non- limiting examples. In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0062] EXAMPLE

[0063] Nitrogen-doped graphene oxide (NGO) shows strong selectivity for boron in water, but its commercial application faces challenges due to its powdery form. These challenges include increased flow resistance, pressure drops, aggregation, blockages, and difficulties in regeneration, all of which reduce efficiency in practical column adsorption systems. To overcome these issues, a new method is proposed to assemble NGO onto a melamine sponge (MS) skeleton, creating a composite material (NGO@MS). This approach offers three keyadvantages: (i) Enhanced dispersion of NGO on the porous MS skeleton, reducing stacking and improving water flux and active site utilization; (ii) In-situ assembly of NGO on MS, resulting in a stable and flexible composite that extends adsorbent lifespan and lowers column design requirements; (iii) The strong acid and base resistance of MS ensures high stability and mechanical strength during regeneration, maintaining boron removal efficiency. The NGO@MS adsorbent meets Singapore's stringent water standards (B < 0.5 mg / L), offers stable regenerability, and minimizes design costs, demonstrating significant practical application potential.

[0064] This example sets out preparing the boron removal medium composite material and its use.

[0065] The preparation process for the NGO@MS composite is depicted in Figure 1. It begins with dip-coating melamine sponge (MS) in a graphene oxide (GO) solution, followed by an ammonia hydrothermal reaction that promotes the in-situ growth of nitrogen-doped graphene oxide (NGO) on the sponge. Specifically, 3.66 ml of 2.5% v / v aqueous ammonia is added to 37.5 ml of a GO dispersion (8 mg / ml) under magnetic stirring.

[0066] The melamine sponges, cut to the desired size, are then immersed in this solution for 1 hour to ensure thorough coating with GO. The mixture is subsequently transferred to a Teflon-lined autoclave and heated at 50°C for 5 hours without stirring, allowing the NGO to grow directly on the sponge.

[0067] After natural cooling, the sponges are collected through self-assembly via ethanol and dried in an oven at 100°C for 12 hours. To remove any unattached NGO sheets, the sponges are washed several times with deionized water. The final product, referred to as NGO@MS, demonstrates a high loading capacity, with a mass ratio of MS to NGO of approximately 1 :4.

[0068] As illustrated in Figure 2, the NGO sheets self-assemble into network structures within the porous MS skeleton, effectively preventing significant restacking and ensuring a uniform and stable distribution of NGO on the sponge surface. This configuration not only enhances adsorption efficiency but also scales effectively for industrial applications.

[0069] The NGO@MS adsorbent's structural stability was first assessed in feedwater. Even after a 5-hour soaking period, NGO@MS demonstrated remarkable integrity with no signs of degradation. Additionally, during the pressure flushing process, the solution remained clear, indicating the sustained stability of the NGO@MS material. To optimize the performance of NGO@MS for boron removal from feed water, a series of experiments were conducted, varying the concentration of the adsorbent in relation to the feedwater.

[0070] To more accurately simulate brackish water conditions, additional elements were included in the synthetic feedwater: (Na+, 241 mg / L), chloride (CI-, 400 mg / L), boron (B, 1.8 mg / L), calcium (Ca2+, 2.3 mg / L), magnesium (Mg2+, 6.5 mg / L), potassium (K+, 10 mg / L) and sulphate (SO42-, 6.0 mg / L). The concentrations tested were 4 mg / ml, 6 mg / ml, 8 mg / ml, and 10 mg / ml, with the aim of determining the most effective ratio for reducing boron content in the treated water.

[0071] The results, as depicted in Figure 3, clearly indicate that as the concentration of NGO@MS increases, boron removal efficiency improves significantly. At 8 mg / ml, the boron content in the effluent water was reduced to 0.6 ppm — a noteworthy reduction. Further increasing the concentration to 10 mg / ml resulted in a dramatic decrease, lowering the boron concentration to 0.368 ppm, which complies with Singapore's stringent drinking water standards ( < 0.5 ppm). These results suggest that the optimal concentration for maximizing boron removal is at or above 10 mg / ml. At this concentration, NGO@MS exhibits peak performance, delivering exceptional boron removal efficiency.

[0072] When the NGO@MS adsorbent reaches saturation with boron ions, it can be efficiently regenerated through a simple backwashing process. A 5% HCI solution is used for 30 minutes to dissociate the borate-NGO@MS complex, effectively releasing the captured boron. Following this, a 2.5% NaOH solution is applied for another 30 minutes to neutralize the acid and restore the adsorbent’s functional sites, making it ready for subsequent boron removal cycles.

[0073] The structural stability of NGO@MS under acidic and alkaline conditions was rigorously evaluated. As shown in Figure 4, after soaking the NGO@MS in both HCI and NaOH solutions for 30 minutes, the solutions remained clear, indicating that the adsorbent maintained its chemical integrity under these conditions. The strong mechanical and chemical stability of the MS component significantly enhances the overall durability of the composite material.

[0074] To assess the regeneration capability and long-term stability of NGO@MS, we conducted a series of tests on its boron removal performance following multiple cycles of acid and alkali regeneration. In these experiments, the regenerant dosages were 4.5 pl / ml of 5% HCI and 6.7 pl / ml of 2.5% NaOH.

[0075] As illustrated in Figure 5, even after 29 regeneration cycles, NGO@MS continued to demonstrate high boron removal efficiency, consistently reducing the effluent boron concentration to below the stringent limit of 0.5 ppm. Figure 6 further confirms the exceptional structural stability of NGO@MS in feedwater, even after 29 regeneration cycles. The adsorbent remained stable in both acidic and alkaline environments, with the solutions stayingclear throughout the process. These results underscore the robust mechanical and chemical stability of NGO@MS, making it a highly reliable and durable solution for long-term boron removal applications at industry scale.

[0076] CONCLUSION

[0077] Nitrogen-doped graphene oxide (NGO) may be in-situ assembled onto the melamine sponge (MS) skeleton through interactions between the oxygen-containing functional groups of the NGO and the amino groups present on the MS. This assembly process results in the formation of a stable NGO@MS composite material rather than a powdery adsorbent. The non-powdered composite effectively addresses the challenges commonly associated with powder-type adsorbents in practical column adsorption systems, such as increased flow resistance, pressure drops, aggregation, blockages, and difficulties in regeneration.

[0078] The porous MS skeleton provides a three-dimensional framework that enhances the dispersion of the NGO, thereby reducing layer stacking and improving the accessibility and utilization of its active adsorption sites. This structure also facilitates higher water flux and more efficient boron removal. The resulting NGO@MS composite combines the flexibility and resilience of the MS framework with the high adsorption capacity of the NGO, producing a material that exhibits both structural integrity and excellent functional performance.

[0079] The flexible characteristics of the MS skeleton extend the operational lifespan of the adsorbent and allow it to better withstand the mechanical stresses typically encountered during continuous use. This flexibility also reduces the design and engineering requirements of the adsorption column, enabling simpler, more cost-effective system configurations while maintaining high adsorption efficiency. Furthermore, the strong resistance of the MS to both acidic and basic environments ensures that the NGO@MS adsorbent retains its stability and mechanical strength during regeneration, thereby improving separation efficiency and maintaining high boron removal performance over multiple cycles.

[0080] The robust mechanical and chemical stability of the NGO@MS composite makes it a reliable and durable solution for long-term boron removal in industrial water treatment applications. Its ability to maintain high performance under varying operational and chemical conditions contributes to consistent compliance with stringent water quality standards, while minimizing chemical consumption, energy usage, and overall operational costs.

[0081] Non-limiting examples of the invention and comparative examples will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

[0082] While embodiments of the invention have been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

CLAIMS1. An adsorbent for treating water, the adsorbent is made of a composite material comprising a porous support structure and a carbon-based material, the carbon-based material disposed on or within the porous support structure, and wherein the composite material removes an amount of boron present in the water being treated.

2. The adsorbent according to claim 1 , wherein the porous support structure is a melamine sponge skeleton.

3. The adsorbent according to any one of the preceding claims, wherein the carbon-based material is graphene oxide.

4. The adsorbent according to claim 3, wherein the graphene oxide is self-assembled N- doped graphene oxide.

5. The adsorbent according to claim 3, wherein the graphene oxide is nitrogen doped.

6. The adsorbent according to any one of the preceding claims, wherein the composite material is a melamine sponge skeleton and nitrogen-doped graphene oxide composite.

7. The adsorbent according to claim 6, wherein the mass ratio of melamine sponge skeleton to nitrogen-doped graphene oxide is about approximately 1:4.

8. A water treatment device comprising an adsorbent according to any one of claims 1 to 7.

9. A method of removing an amount of boron present in an aqueous solution, the method comprising:(a). contacting a boron removal medium with the aqueous solution; and(b). separating the boron removal medium from the aqueous solution, wherein the boron removal medium comprises the boron removal medium is a medium according to any one of claims 1 to 7.

10. The method of claim 9, wherein the concentration of the boron removal medium to aqueous solution is between 8 mg / ml to 10 mg / ml.

11. The method according to any one of claims 9 or 10, wherein the separating comprises centrifuging or filtering the aqueous solution, or the separating comprises passing water through the boron removal medium.

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