Renewable energy sources using pressure-driven filtration processes and systems

Abstract

Hydrogen 11 is co-produced from water 8 produced in a pressure-driven desalination / filtration process such as reverse osmosis, forward osmosis, pressure retarded osmosis, ultrafiltration, etc. A small portion of the feed, raw brine and / or permeate involved in the desalination / filtration process is subjected to electrolysis, thereby splitting water to produce hydrogen. This is achieved by providing novel RO-type semipermeable and / or UF-type membranes that incorporate electrodes 9, 10 within the membrane to enable the splitting of water by electrolysis.

Description

[Technical field]

[0001] The present invention relates generally to the production of renewable energy sources, particularly hydrogen, using pressure-driven filtration processes and systems. [Background technology]

[0002] To combat global warming and other environmental problems, the development of renewable energy sources is becoming increasingly important. Hydrogen is a suitable energy carrier for energy storage, and it can be burned to produce water with zero CO2 emissions. Therefore, the efficient production and storage of hydrogen for energy generation is a very attractive proposition. Water electrolysis is a known technology for producing hydrogen from water, in which water is the reactant and is split into hydrogen and oxygen using a direct current.

[0003] Anode: H2O → 1 / 2O2 + 2H + +2e - Cathode: 2H + 2e - →H2 Overall: H2O → H2 + 1 / 2O2

[0004] Many different types of water electrolysis processes have been investigated for hydrogen production, including alkaline water electrolysis, proton exchange membrane water electrolysis, solid oxide water electrolysis, and alkaline anion exchange membrane water electrolysis.

[0005] Satisfactory scale-up of hydrogen production may be hindered by a lack of suitable water sources, renewable energy sources, and / or convenient locations for storing the produced hydrogen.

[0006] It is an object of the present invention to provide improved devices, processes and systems for hydrogen production that address some or all of these problems. Summary of the Invention

[0007] According to a first aspect of the present invention, there is provided a membrane element configured for osmotic and / or gauge pressure driven filtration of water and electrochemical decomposition of at least a portion of the water for co-production of hydrogen, the membrane element comprising at least one permselective membrane configured to at least partially purify feed water when a pressure differential is provided across the membrane, the membrane element comprising at least one anode electrode and at least one cathode electrode.

[0008] In the context of this disclosure, a selectively permeable membrane is any type of reverse osmosis (RO) or ultrafiltration (UF) type membrane that may be used for osmotic and / or gauge pressure driven filtration of water. "RO" type membranes include membranes used for reverse osmosis, pressure retarded osmosis (PRO), forward osmosis (FO) and nanofiltration (NF). "UF" type membranes include membranes used for ultrafiltration (UF), microfiltration (MF) and other purification processes from suspended solids. These types of membranes are selectively permeable with a maximum pore size of 0.1 microns. In this regard, membrane types will have specific pore sizes, e.g. MF membranes generally have a maximum pore size of about 0.1 microns, UF membranes generally have pore sizes between 0.01 and 0.1 microns, NF membranes generally have a maximum pore size of 0.01 microns and RO membranes generally have pore sizes of 0.0001 microns. However, other parameters may be used to characterize these types of membranes as known in the art.

[0009] The membrane element of the first aspect is preferably incorporated into a module configured for pressure-driven filtration of water and electrochemical decomposition of at least a portion of the water for co-production of hydrogen. To this end, a second aspect of the invention provides a module comprising a feed water inlet, at least one membrane element according to the first aspect of the invention, a product water outlet and, optionally, a reject water outlet.

[0010] The optional reject outlet is for a reject stream, which is the portion of the feed water that does not pass through the membrane and is rejected as salt water in permselective membrane applications. This reject stream may not be present in UF or MF applications.

[0011] Additionally, the module may be provided with hydrogen and / or oxygen outlets, but more preferably dissolved hydrogen is provided in the reject stream or product water for later extraction from the reject stream or product water, for example by degassing or a gas separation membrane.

[0012] The membrane element according to the first aspect of the invention and the module according to the second aspect of the invention may be incorporated into any pressure-driven water filtration process or system to provide simultaneous co-production of at least partially purified water and hydrogen.

[0013] Thus, a third aspect of the present invention provides a process for pressure driven water filtration with co-generation of hydrogen, the process comprising: supplying feed water to a membrane element according to a first aspect of the present invention through a feed water inlet; applying a pressure differential across the RO and UF type permselective membranes of the membrane element to draw feed water through the membranes to form product water; applying a potential difference between electrodes of the membrane elements to electrochemically decompose at least a portion of the feed water and / or product water to form hydrogen and oxygen; recovering product water and optionally a reject stream, and hydrogen; Includes.

[0014] Preferably, hydrogen is dissolved in at least one of the product water or reject streams and extracted therefrom, for example by degassing or membrane gas separation.

[0015] A fourth aspect of the present invention provides a system for pressure-driven water filtration with cogeneration of hydrogen, the system comprising: A feed water inlet; At least one membrane element according to the first aspect of the present invention; at least one pump for pressurizing the supply water; a power source for applying a potential difference to the electrodes of the membrane element; a product outlet and optionally a reject water outlet; a hydrogen outlet in the product and / or reject water; It is equipped with:

[0016] In an embodiment, the membrane elements and modules of the first and second aspects of the invention, respectively, may form part of a pressure retarded osmosis (PRO) system for water-to-electricity with co-generation of hydrogen, but more preferably the membrane element or module is incorporated into a reverse osmosis (RO) or nanofiltration (NF) or other brand system for water desalination and co-generation of hydrogen.

[0017] Alternatively, the elements or modules can be incorporated into other water filtration systems, such as ultrafiltration or microfiltration systems, to provide purified water and hydrogen generation, all of which are described further herein. The main difference between RO, PRO, and NF and UF and MF is that RO, PRO, and NF implement desalination semipermeable membranes and have reject streams. UF and MF membranes are not desalination semipermeable membranes and do not have reject streams. However, all can be equipped with electrodes in or on the membrane to enable water splitting according to the present invention.

[0018] In the context of this disclosure, the reverse osmosis (RO) separation process, in which the membrane contains a semi-permeable desalination layer, extends to reverse osmosis (RO), nanofiltration (NF), and any other desalination semi-permeable membrane in which the RO dissolved ion separation process takes place. The pressure retarded osmosis (PRO) process, in which the membrane contains a semi-permeable desalination layer, is applied to processes in which the semi-permeable membrane acts as an osmotic pump and water with low salinity permeates water with high salinity. This is a different physical process from the RO dissolved ion separation process, and also applies to forward osmosis (FO) and other processes in which the membrane acts as an osmotic pump.

[0019] The water filtration process and system of the present invention includes ultrafiltration (UF), microfiltration (MF), and other processes based on non-desalting semipermeable membranes, where water moves through any membrane driven by gauge pressure for the purpose of water treatment (cleaning from suspended solids), with hydrogen generation being a complementary cogeneration activity. In the present invention, the membranes used in UF, MF and other processes for cleaning from suspended solids are referred to by the general name "UF-type membranes."

[0020] The particular number and arrangement of inlets and outlets provided within an embodiment of a module, process or system of the invention will depend on the type of desalination or water treatment process in which the electrochemical separation of water is incorporated. For RO or NF processes, the module has one inlet, "raw brine," and two outlets, a "residual brine stream" ("reject stream" or "reject outlet") and a "permeate stream." Hydrogen can exit through one or both of these outlets.

[0021] The module for the PRO process has two inlets and two outlets: one for the "draw solution" and one for the "feed water", and two outlets for the "residual fluid stream" and one for the "residual brine". Hydrogen leaves through one or both of these outlets.

[0022] In contrast, for UF and MF processes, the module typically has one inlet, "feed water," and one outlet, "filtrate water." Hydrogen only comes out of one outlet.

[0023] In all the above mentioned systems and processes, only a small portion of the water involved in RO, NF, PRO, UF, MF undergoes electrochemical decomposition to form hydrogen in the membrane, the rest produces product or filtrate water or a rejected draw solution. Preferably, less than 5% of said water is separated. More preferably, in all the processes, the amount is less than 1%, in particular 0.05%, more in particular 0.01%, ideally less than 0.01%.

[0024] The membranes, modules, systems and processes according to the invention should be equipped with a suitable power supply so that a current can be applied between the electrodes to enable the electrochemical separation of water. Preferably a low current density is used, preferably less than 100 mA / cm. 2 Less than or equal to 10 mA / cm, more preferably 2 Below, especially 5mA / cm 2 Ideally, less than 1mA / cm 2 The following is the result.

[0025] The process may also involve pH corrections to optimize the reactions occurring between the electrodes, for example to reduce the reversible potential of the oxygen evolution reaction.

[0026] It is understood that any type of RO and UF type membrane may be provided within the module for performing osmotic and / or gauge pressure driven filtration of the feed water, however the membrane is provided to include an anode and a cathode, and optionally additional electrodes for electrochemically separating a portion of the permeate water to produce hydrogen. Suitable membranes incorporating these electrodes may be provided in a very wide range of configurations and are not limited to the specific permutations disclosed herein.

[0027] For example, in one embodiment, a module includes at least one RO-type membrane including a desalination layer and a support layer, the membrane including at least one anode electrode and at least one cathode electrode, the electrodes comprising the desalination layer and / or disposed in, on or between one or both of the desalination layer and the support layer.

[0028] In embodiments, a membrane element or module may incorporate feed and / or permeate spacers. Electrodes may be provided on or adjacent to one or the other of the feed and / or permeate spacers.

[0029] The rejection layer, support layer, feed or permeate spacer serve as mechanical support for the electrodes. Thus, the existing permeate and feed spacers of RO, PRO, NF, FO modules and the semipermeable membrane layers of RO, PRO, NF, FO membranes can be used as is to separate the anode and cathode electrodes incorporated in the membrane element of the present invention.

[0030] In UF type membranes, the cathode and anode can be located either inside and / or outside these hollow fiber membranes.

[0031] Electrodes can be incorporated into an RO-type membrane in many different configurations. For example, at least two electrodes can be disposed between the desalination layer and the support layer. Alternatively, at least one electrode can be disposed between the desalination layer and the support layer and at least one electrode can be disposed on the outer surface of the desalination layer. In another embodiment, at least two electrodes can both be disposed on the outer surface of the desalination layer.

[0032] In yet another embodiment, the electrodes may be located on the permeate and / or feed spacer, and more preferably, the electrodes are located on either side of the permeate or feed spacer. In an alternative embodiment, both electrodes may be located on one side of the permeate and / or feed spacer. In other embodiments, one electrode may be located on one side of the permeate and / or feed spacer and the other electrode may be located at an opposing site on the permeate and / or feed spacer.

[0033] In alternative embodiments of the invention, the electrodes (anode and / or cathode) may be coupled to the permeate or feed spacer. Preferably, the feed spacer is mechanically coupled to the permeate tube. In one embodiment, the anode may be coupled to the feed spacer and the cathode may be coupled to the permeate spacer. In another embodiment, the cathode may be coupled to the feed spacer and the anode may be coupled to the permeate spacer. In yet other embodiments, the polarity of the spacers may be changeable to control which electrode is utilized as the cathode and which electrode is utilized as the anode.

[0034] In other embodiments, the electrodes (anode and / or cathode) may be provided with a feed and / or permeable spacer. In such embodiments, the spacer is at least partially coated with a conductive layer and / or a catalyst layer, thereby making the electrode an electrically conductive and electrocatalytically active anode (for O2 generation) or an electrocatalytically active cathode (for H2 generation) or both. The spacer may be at least partially coated with at least one catalyst, e.g., selected from Pt, Ir, and combinations thereof.

[0035] Spacer conductivity can be achieved, for example, by coating the polymer spacer with nickel or copper metal and then displacing these metals with Pt- or Ir-based catalysts, for example by redox displacement or other techniques.

[0036] In embodiments, the electrodes may be provided in the form of a grid or parallel spaced strips, or may be provided in the form of a full or partial coating of the permeant and / or feed spacer.

[0037] Additionally, the desalting layers or spacers may be formed of a material that may enable them to function as one of the electrodes, i.e., a material that has sufficient electrical conductivity (e.g., graphite, a composite of a polymer and conductive particles, or a metal, etc.).

[0038] More preferably, at least one electrode may be formed from graphene. In one embodiment, the electrodes (anode and / or cathode) are graphene or carbon fiber / carbon cloth.

[0039] Preferably, carbon is the substrate for coating with mixed metal oxides (MMOs) selected from platinum (Pt), iridium (Ir), Pt-lr, ruthenium (Ru) metals and any combination thereof. In these embodiments, MMO / C electrodes can be prepared by a two-step process consisting of forming a sacrificial copper or nickel layer on carbon via electroless or electrodeposition, and replacing the sacrificial metal with Pt, Ir, Ru or Pt-lr.

[0040] In an embodiment, the salt rejection layer is formed from graphene and may comprise one of the electrodes. The support layer is preferably made of a porous material, preferably a ceramic material.

[0041] Alternatively, the electrodes (anode and / or cathode) may be a titanium material for increased durability.

[0042] The electrodes may be provided in any configuration, but are preferably selected from the group consisting of meshes, plates, fabrics made of fibers, and sintered bodies, and are more preferably made of titanium.

[0043] The semi-permeable membrane may further include a reference electrode. Optionally, at least one dielectric material may be provided between the at least two electrodes. The feed and / or permeable spacer may function as a dielectric material for the electrodes printed, coated or disposed on either side of the spacer.

[0044] Additionally, at least one catalyst may be provided on at least one or both of the electrodes to promote desired reactions, for example, promoting the evolution of oxygen and hydrogen and discouraging the evolution of chlorine.

[0045] In one embodiment, the electrode may be at least partially coated with at least one catalyst, preferably selected from at least one of the group consisting of iridium oxide, ruthenium oxide, tantalum oxide, titanium oxide, platinum, and platinum oxide, and any combination thereof.

[0046] As noted above, the processes and systems according to the third and fourth aspects of the invention may be applied to many different types of pressure-driven water filtration processes and systems.

[0047] In a preferred embodiment, the process and system comprises a reverse osmosis (RO) process and system for splitting water into hydrogen and oxygen in a permeate separation module including at least one, and preferably a plurality of, membrane elements having a feed side and a permeate side with at least two electrodes disposed on an RO-type membrane and / or support layer and / or feed and / or permeate spacer of the membrane element. Feed brine is fed to the module, a portion of the feed brine exits the module as a retentate brine stream, and a portion of the feed brine permeates the membrane in a conventional reverse osmosis process to produce desalinated water by the net driving force of the balance of gauge pressure and osmotic pressure and exits the permeate side of the membrane element as a permeate stream.

[0048] The process involves applying an electric current to the membrane electrodes, either continuously or for a predetermined period of time, which separates a portion of the feed brine and / or permeate stream into hydrogen gas and oxygen gas, which exit the permeate separation module along with the remaining brine and / or permeate stream. In this manner, the RO module combines the desalination of brine for commercial use with the simultaneous decomposition of water into hydrogen and oxygen. Preferably, less than 5% of the feed brine, more preferably less than 1%, is used for hydrogen production.

[0049] Alternatively, the process and system can be applied to water purification processes carried out on non-desalting semipermeable membranes, such as ultrafiltration or microfiltration membranes in UF or MF processes. In this embodiment, less than 1% of the filtrate, preferably less than 0.1% of the filtrate, is used for hydrogen generation.

[0050] Such a process and system for providing water filtration and hydrogen cogeneration can include a suspended solids fouling filtration module, said membrane elements having a feed side and a filtrate side with at least two electrodes disposed on a membrane, and / or a support layer, and / or a feed and / or filtrate spacer, wherein raw salt water enters the feed side of the module, is driven by a gauge pressure to at least partially permeate the membrane in a normal filtration process, and exits the filtrate side as a filtrate stream, said method for splitting water into hydrogen and oxygen includes applying an electric current to the electrodes, either continuously or for a predetermined period of time, which splits a portion of the permeate stream into hydrogen gas and oxygen gas that exits the filtration module along with the filtered water stream.

[0051] In another embodiment, an osmotic process and system for separating water into hydrogen and oxygen is provided that includes providing first and second solutions having different osmotic and gauge pressures to opposite sides of an RO type semipermeable membrane to generate a low-salt solution across the membrane, the semipermeable membrane including at least two electrodes, applying an electric current between the electrodes of the RO type semipermeable membrane to separate the low-salt solution into hydrogen and oxygen, and recovering the hydrogen and oxygen.

[0052] Typically, the first solution is known as the draw solution and the second solution is known as the feed solution. For example, the feed solution may include seawater, brackish water, wastewater, or fresh water such as river water or groundwater.

[0053] The osmotic process can include pressure retarded osmosis or forward osmosis, wherein an RO type semipermeable membrane has a first side and a second side opposite the first side, a first saline solution including a draw solution having an osmotic pressure POr and a gauge pressure PGr for entering the first side of the membrane, a second saline solution including a feed solution having an osmotic pressure POP and a gauge pressure PGp for entering the second side of the membrane, and at least a portion of the feed solution from the second side of the membrane permeates to the first side according to a net driving pressure defined by the balance of the pressures PGr, POr, POp and PGp, wherein the draw solution and a portion of the permeated feed solution exit the first side of the membrane as a residual brine stream via a residual brine outlet, the remainder of the feed solution exits, at least periodically, the second side of the membrane as a residual fluid stream via an outlet, and at least a portion of the low salt concentration solution stream passes from the second side to the first side for separation into hydrogen and oxygen as they pass through the semipermeable membrane.

[0054] Additionally or alternatively, at least a portion of the first saline solution and / or the second feed solution passing along the membrane flows to be decomposed into hydrogen and oxygen as it passes along the semipermeable membrane.

[0055] It will be appreciated that the processes and systems according to the third and fourth aspects of the invention may, and preferably do, incorporate conventional steps and components for implementing these processes and systems used in prior art processes and systems, such as intakes and discharges, pre- and post-treatment units, pumps, control valves, delivery pipes and control units.

[0056] Preferably, energy for the operation of the process and system is produced efficiently. For example, electricity for operating the electrodes of the membrane can be provided using pressure retarded osmosis, where the draw solution is provided by dissolving rock salt in a salt dome. The dissolution of rock salt can be carried out under pressure equal to or close to PGr. Alternatively, the dissolution can be carried out at atmospheric pressure. The salt dome is also used to store hydrogen generated in the process.

[0057] Alternatively, the produced hydrogen may be stored in a storage tank for later use or supplied to a network grid for use. [Brief description of the drawings]

[0058] For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1A] FIG. 1 is a schematic diagram showing the principle of alkaline water electrolysis according to the prior art. [Figure 1B] FIG. 1 is a schematic diagram showing the principle of proton exchange membrane (PEM) water electrolysis according to the prior art. [Figure 2A] 1 is a schematic top view of a cross section through a FO or PRO semipermeable membrane incorporating an electrode according to an embodiment of the present invention. [Figure 2B] FIG. 2B is a three-dimensional view of the semipermeable membrane shown in FIG. 2A with the desalting layer 4 and feed 7 removed. [Diagram 3] FIG. 1 is a three-dimensional view of a semi-permeable membrane incorporating a pair of electrodes according to an alternative embodiment of the present invention. [Figure 4] FIG. 13 is a three-dimensional view of a semi-permeable membrane incorporating a pair of electrodes according to yet another embodiment of the present invention. [Diagram 5] FIG. 13 is a three-dimensional view of a semi-permeable membrane incorporating a pair of electrodes according to yet another embodiment of the present invention. [Figure 6A] FIG. 13 is a fragmentary three-dimensional view of a semipermeable membrane having a permeable spacer and a feed spacer and incorporating electrodes, according to yet another embodiment of the present invention. [Figure 6B] FIG. 6B shows two membranes according to FIG. 6A arranged in mirror symmetry. [Figure 7] FIG. 1 is a schematic diagram of a desalination plant and process scheme in which one or more semipermeable membranes according to the present invention may be incorporated. [Figure 8] Graph showing the reversible potential for chlorine evolution, oxygen evolution and hydrogen evolution reactions as a function of pH, T=25° C., [Cl−]=20 g / L, gas fugacity=1, no complexation, infinite dilution. [Figure 9] FIG. 1 is a schematic diagram illustrating one embodiment of a system of the present invention for hydrogen production and storage. [Figure 10] 2 is a schematic diagram of a permeation tube having a pair of spacers and electrodes coupled thereto, in accordance with an embodiment of the present invention. [Figure 11] FIG. 13 is a schematic diagram of a permeation tube having multiple spacers and electrodes coupled thereto, according to another embodiment of the present invention. [Figure 12] FIG. 3 is a schematic diagram of a titanium foil clad 300 for infiltration and / or feed spacers with and without an additional conductor between the titanium foil and the plastic spacer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059] The present invention generally relates to a novel hydrogen production from water produced during a desalination or water treatment process using RO or UF membranes, where the feed water is pressure driven (e.g., by osmotic and gauge pressure) against the membrane, certain components pass through the membrane while others are rejected, and a portion of the water is electrochemically separated to produce hydrogen.

[0060] In some examples, the process utilizes feed water permeated through an RO type semipermeable membrane to draw the solution into a pressure retarded osmosis process PRO or forward osmosis process FO. Very low salinity water passes through the RO type semipermeable membrane from the feed water stream to a draw solution stream. A portion of this low salinity water is electrolyzed to split water and produce hydrogen. This is accomplished by incorporating one or more electrodes into the RO type semipermeable membranes conventionally used in such pressure-driven energy production processes, providing an improved membrane that allows for the simultaneous splitting of water by electrolysis in addition to the standard PRO process conventionally practiced using these types of membranes.

[0061] Pressure retarded osmosis (PRO) is an osmotically driven membrane process that utilizes the energy harnessed from mixing of a high salinity stream with a low salinity stream to generate mechanical energy (utilization of the Gibb's free energy of mixing). Water permeates through an RO-type semipermeable membrane from a low-salinity feed stream into a high-salinity, partially pressurized, brine stream (the "draw solution"). The water pressure is less than the osmotic pressure, and as a result, water (the permeate stream) is transported from the feed stream to the brine stream with a net osmotic driving force. The permeate stream is pressurized, diluting the brine stream, and the energy of the pressurized permeate stream can be converted to mechanical or electrical energy via a turbine-generator.

[0062] Forward osmosis is another osmotically driven membrane process that uses an RO type membrane to treat two liquid feed streams. On one side of the membrane is the feed solution (FS) with low osmolarity, and on the other side of the membrane is the draw solution (DS) with high osmolarity. Due to the difference in osmolarity, water flows through the membrane from the FS side to the DS side, simultaneously diluting the DS and concentrating the FS. RO membranes consist of an active layer (or desalting layer) and a porous support layer, with the FS side generally facing the active layer.

[0063] Both of these processes produce a very low salinity water flow across the membrane. The present invention utilizes this water flow for hydrogen production. However, the invention is not limited to these types of membranes and can be implemented with other types of membranes, such as reverse osmosis and nanofiltration membranes. RO type semipermeable membranes are essentially very thin layers of polymeric material that act as a barrier layer and separate dissolved ions or molecules from water when the applied pressure is greater than the osmotic pressure.

[0064] In one embodiment, the invention utilizes the permeate stream generated in the PRO or FO. This stream cannot be removed from the membrane and is extremely thin, making it impossible to measure directly. However, the inventors are the first to recognize that this stream has an extremely low salinity and therefore could potentially be used for hydrogen production. In this regard, it is not readily known that at the interface between the desalination layer and the support layer of the FO and / or PRO membrane, there is a continuous movement of low-salinity water, having a salinity of about 1 / 1000 of that of the feed solution (seawater) moving on one side (FS) of the FO / PRO membrane and about 1 / 10,000 of that of the draw solution (DS) on the other side. The innovation places electrodes in this extremely thin low-salinity stream for the purpose of separating water for the production of hydrogen and oxygen. Thus, the invention provides a novel permeable membrane that allows separation of water, and further provides a novel method and system for the production of hydrogen and oxygen from water.

[0065] The present invention can also be incorporated into RO and NF processes, where a small portion of the feedwater and / or permeate at the raw salt concentration is subjected to electrolysis, thereby splitting water to produce hydrogen. Again, this is accomplished by incorporating one or more electrodes into the RO-type semipermeable membranes traditionally used in these pressure-driven desalination processes, providing an improved membrane that allows for the simultaneous separation of water by electrolysis in addition to the standard desalination traditionally performed using RO-type membranes.

[0066] Alternatively, the present invention can be incorporated into UF and MF processes to electrolyze a portion of the feed water and / or filtrate to split water and produce hydrogen, again by incorporating one or more electrodes into UF type membranes traditionally used in pressure-driven water treatment processes to provide an improved membrane that allows for the simultaneous splitting of water by electrolysis in addition to the standard water treatment traditionally performed using UF type membranes.

[0067] The following description equally applies to RO, NF, PRO, UF and MF processes which have been modified in accordance with the present invention to provide hydrogen generation.

[0068] The present invention provides simultaneous water desalination (RO, NF) or water treatment (UF, MF, FO) or osmotic power generation (PRO) and electrochemical production of hydrogen gas for electrical energy conversion and storage (hydrogen economy). Electrochemical reactors and membrane reactors have at least two common components: spacers and membranes. Moreover, modern water electrolysis systems utilize ultrapure water. Using the same membranes, spacers, control and automation units, hydraulic systems and other equipment and materials, direct electrolysis of deionized water in desalination and filtration modules can significantly reduce the operational and capital costs of water electrolysis and provide added value to desalination and water treatment plants.

[0069] Conventional water electrolysis processes use currents of 200 to 2000mA / cm 2 (or even higher). Such high current densities are necessary to reduce the reactor footprint and minimize the capital costs of these processes. Currently, there are three main processes for hydrogen production using water electrolysis (WE): (i) alkaline water electrolysis (see FIG. 1A), (ii) polymer electrolyte membrane (PEM) electrolysis (see FIG. 1B), and (iii) steam or solid oxide electrolysis (SOE). SOE processes are performed at high temperatures (>500° C.) and are not relevant to the present invention, so they will not be described in further detail.

[0070] All WE technologies are based on the oxidation and reduction of water molecules or H+ and OH- ions to oxygen and hydrogen gas at the anode and cathode. These processes consume electrical energy and heat, and the reactions occurring at the anode and cathode depend on the pH of the electrolyte as shown below:

[0071] In the case of alkaline solution (see Figure 1A) Anode: 2OH - →0.5O2+H2O+2e - Er 0 =0.401V VS. SHE (1) Cathode: 2H2O+2e - →H2+2OH - Er0 =-0.828V VS. SHE (2) For acidic solutions (see Figure 1B): Anode: H2O → 0.5O2 + 2H + +2e - Er 0 =1.229V VS. SHE (3) Cathode: 2H + +2e - →H2Er 0 =0.0V VS. SHE (4) Overall: H2O→H 2(g) +0.5O 2(g) Vrev=1.229V (5) (where Vrev is the reversible voltage (volts) and Er° is the standard reduction potential (volts vs. standard hydrogen electrode, SHE)).

[0072] The oxidation and reduction processes take place at the anode and cathode, respectively. In all electrolysis cells, the anode is more positive than the cathode. Electrons flow from the anode to the cathode (i.e., in the opposite direction to the flow of electric current) through an external wire (or other, usually metallic conductor) connected to a direct current (DC) power source. The electric circuit of an electrochemical cell requires the movement of charge (i.e., ions) in the electrolyte. In other words, an electrolyte must be present in the water to sustain the WE process. Two main types of electrolytes are used in low-temperature (i.e., T<100 °C) water electrolysis processes: (1) salts, acids, and bases and (2) solid electrolytes.

[0073] As can be derived from the above equations (1) to (4), H is generated in the electrolyte by the anodic and cathodic reactions. + Ions and OH -Ions are produced. These ions can be used to drive the ionic current in the electrolysis of water. In this case, no external electrolyte addition is required. This principle is used in the solid electrolyte water electrolysis process, as shown in Figure 1B. A "solid electrolyte" is an ion exchange membrane located between the anode and the cathode of an electrochemical cell. Usually, polymeric cation exchange membranes (e.g. Nafion, a fluoropolymer-copolymer based on sulfonated tetrafluoroethylene) are used in this type of WE device. For this reason, the term "proton exchange membrane (PEM) water electrolysis" and the abbreviation PEM are used in the technical literature. The native membrane contains fixed negatively charged sulfonic groups and exchangeable H+ ions. The anodic production of oxygen according to reaction (3) generates H+ ions. These ions flow through the membrane (ionic current in the "solid" electrolyte) and are consumed in the hydrogen evolution reaction that proceeds at the cathode via reaction (4). In this way, the overall concentration of H+ ions in the membrane is kept constant. PEM electrolysis requires ultra-high purity deionized water (total dissolved solids less than 0.5 ppm to prevent membrane degradation) and expensive precious metal catalysts (e.g., lrO2 at the anode and Pt at the cathode).

[0074] Such conventional water electrolysis processes require (1) ionic carriers inherently contained in the electrolyzed water (e.g., seawater), (2) ionic carriers added to deionized water (e.g., alkaline water electrolysis), or (3) ion exchange membranes. Electrolysis of pure water is not commonly performed.

[0075] Seawater is a potentially unlimited source of water for electrochemical hydrogen generation, but there are two significant obstacles that must be overcome to develop industrial-scale hydrogen production from seawater electrolysis: (1) scaling of the cathode with Ca and Mg precipitates, and (2) the generation of chlorine species via the anodic oxidation of chloride ions.

[0076] Regarding the scaling problem, seawater contains a large amount of magnesium and calcium ions, which precipitate in the alkaline solution and on the cathode because the local pH near the cathode increases due to the hydrogen generation reaction. 2 At current densities above this, the pH near the cathode is as high as pH=12. As a result, at current densities of 200 mA / cm 2 Direct electrolysis of seawater above this temperature inevitably results in the detrimental deposition of Ca and Mg on the cathode.

[0077] Furthermore, the anodic generation of chlorine gas is also a major problem. In this regard, seawater contains a high concentration of chloride ions, which can be oxidized at the anode to produce chlorine gas. This is hydrolyzed to hypochlorous acid (HOCI) and produces hypochlorite ions (OCI). - ) in equilibrium with Cl, typical of seawater. - At concentrations (approximately 20 g / L), the current density of the Cl2 evolution reaction is more than 70%. This means that Cl2 is the main anodic product in direct seawater electrolysis processes using typical water electrolysis anodes (graphite, Pt, mixed metal oxides, lrO2, etc.). For the purpose of mass production of H2, the evolution of chlorine must be prevented.

[0078] The present invention reduces or eliminates all these issues by incorporating electrodes into traditional pressure-driven membranes used in seawater desalination or water treatment processes, representing a key step in hydrogen production from readily available water sources.

[0079] The present process and system for simultaneous pressure-driven membrane filtration of water and electrochemical water splitting to produce hydrogen is significantly different from the large-scale electrochemical water splitting of the prior art. 2 / h", which is equivalent to 3mA / cm 2 " and is the current density applied to state-of-the-art alkaline and solid electrolyte water electrolysis reactors (200-2000mA / cm 2), but the integration of electrochemical processes into a water desalination or filtration module according to the invention is not expected to add to the footprint of an already existing desalination or water treatment facility. Furthermore, the operating costs are expected to be even lower than established water electrolysis technologies, since, for example, electrolysis of seawater (or RO brine or other water to be purified) at very low current densities (1) consumes less energy per unit volume of hydrogen gas produced, (2) does not produce chlorine, which is not required for seawater electrolysis for hydrogen gas production, (3) can be carried out using inexpensive catalysts with long operating lives, and (4) does not produce harmful precipitates, e.g. Ca and Mg salts, on the cathode.

[0080] Typically, desalted water contains ions such as Ca, Mg, Na, CO3, SO4, HCO3, Cl, etc. at 10-300 ppm. During water diversion, the concentration of dissolved solids in the permeate stream increases. (i) The occurrence of scaling such as CaCO3, CaSO4, etc., and (ii) the increase in the conductivity of the permeate water increases the power consumption for hydrogen production. This contradiction is resolved by combining two processes (desalination and decomposition), (energy generation and decomposition) or (water filtration and decomposition) in one membrane element. Furthermore, the present invention is cost-effective because it uses common water conveying equipment and water filtration equipment for the two combined processes.

[0081] Any pressure-driven membrane for desalination or filtration of water, such as RO, NF, PRO, FO, UF, MF membranes, etc., can be adapted for the co-production of hydrogen according to the present invention. In the context of the present disclosure, these are referred to as RO-type or UF-type membranes, and generally these consist of semipermeable membranes with a maximum pore size of 0.1 microns. In this respect, the membrane types have specific pore sizes, for example MF membranes generally have a maximum pore size of about 0.1 microns, UF membranes generally have a pore size of 0.01-0.1 microns, NF membranes generally have a maximum pore size of 0.01 microns, and RO membranes generally have a pore size of 0.0001 microns.

[0082] 2A and 2B of the accompanying drawings show one embodiment of a novel semi-permeable membrane 3 according to the present invention that can be incorporated into a PRO or FO module to carry out the process as described above. The membrane is equipped with electrodes 9, 10 and can be used for hydrogen production in addition to conventional applications.

[0083] Referring to FIG. 2A, a feed stream (saline solution, FS) 7 is delivered to the feed side 2 of a semipermeable membrane 3. The membrane 3 consists of a salt rejection layer 4 and a support layer 5, with a series of parallel electrodes 9, 10 disposed between the salt rejection layer 4 and the support layer 5. During forward osmosis (FO) or pressure retarded osmosis (PRO), a portion of the feed stream 7 (saline solution) travels from the feed side 2 of the semipermeable membrane through the salt rejection layer 4 (omitted from FIG. 1B for simplicity) and the support layer 5 to the opposite side 1 (the draw side) as permeate 8. This permeate stream 8 has a very low salinity (approximately 2%) and therefore a lower osmotic pressure than the feed solution 7 (POf) and the draw solution stream 6 (POr).

[0084] The movement of stream 8 (permeate) takes place under the osmotic and gauge pressure balances Por, POf, PGr, PGf. This stream 8 (permeate) only exists as a moving stream during an active FO or PRO process. It cannot be extracted as a liquid, but due to its very low salinity it can be electrochemically separated during its passage through the body of the semipermeable membrane 3. This is achieved by electrodes 9, 10 integrated into the membrane 3, which apply a direct current to the permeate stream 8, dissociating the water into hydrogen 11 and oxygen 12, which can be recovered for later use.

[0085] Figures 3, 4 and 5 of the accompanying drawings show alternative embodiments of a semi-permeable membrane 3 according to the invention, the membrane 3 being provided with electrodes 9, 10 at different positions within the membrane. Identical features already described in relation to Figures 2A and 2B are given the same reference numerals.

[0086] Figure 3 shows a membrane 3 with both electrodes 9, 10 (anode and cathode) arranged externally on the surface of the desalting layer 4. In contrast, Figure 4 shows a membrane 3 with both electrodes 9, 10 arranged between the support layer 5 and the desalting layer 4. In Figure 5, one electrode 10 is arranged between the support layer 5 and the desalting layer 4, and the other electrode 9 is arranged on the outer surface of the desalting layer 4.

[0087] Additionally, the semipermeable membrane may comprise a module having a permeate tube and flat membrane sheets wrapped around the tube to provide a membrane element and incorporating permeate and / or feed spacers (support layers between the membrane sheets). These types of membrane elements or modules may also be adapted to incorporate electrodes in accordance with the present invention. Figure 6A shows a fragment of such a membrane 3 arrangement. This is a single fragment of an RO membrane with a raw feed stream 42 and a permeate stream 43. The support layer 5 and the desalination layer 4 form the entire membrane 3.

[0088] The support layer side 5 of the membrane 3 is provided with a permeate spacer 41, and the desalting layer side 4 of the membrane 3 is provided with a feed spacer 40. This is the typical arrangement shown in Figure 6A. However, it will be appreciated that other arrangements may be provided, such as having the desalting layer 4 facing the permeate spacer 41. Electrodes 9 and 10 are positioned on opposite sides of the permeate spacer 41. In another embodiment, the electrodes may be positioned on the same side (not shown). In other embodiments, three or more electrodes may be positioned on the same or both sides of the permeate spacer 41 (also not shown).

[0089] In other embodiments, one, two, three and more electrodes may be disposed on the same or both sides of the permeate spacer 41 and / or on the feed spacer 40 (not shown). This arrangement of electrodes disposed on the feed spacer 40 and / or on the permeate spacer 41 may be combined with electrodes disposed on the salt rejection layer 4 and support layer 5 of the membrane 3 as described above. In some membranes, the location of the salt rejection layer may be oriented towards the permeate channel instead of the feed channel (also not shown in the accompanying figures).

[0090] Thus, the electrodes 9, 10 can be incorporated into multiple types of filtration membranes, including but not limited to those shown and described herein, including membranes consisting of only the salt rejection layer 4, without the support layer 5 and / or feed or permeate spacers.

[0091] 6B shows two membrane segments 3 arranged in a mirror symmetrical arrangement within an RO module, with arrows indicating the feed stream 42 and permeate stream 43 passing between the membranes 3. The permeate stream generated on membrane 3 is indicated by arrow 44 and merges with the permeate stream 43 from the other membranes arranged within the module. This represents a typical mirror RO membrane arrangement, where the raw brine feed channel 42 includes a feed spacer 40 and the permeate channel 43 includes a permeate spacer 41 arranged therein.

[0092] Thus, it will be understood that any type, number, and arrangement of electrodes may be provided within the membrane to enable water splitting: two or more electrodes may be provided between the desalting layer and the support layer, electrodes may be provided only in the support layer, electrodes may be provided only in the removal layer, or electrodes may be provided in both layers.

[0093] The electrodes must have the necessary electrical conductivity and one of the electrodes may comprise an active or desalination layer 4. A preferred embodiment of the semipermeable membrane also has a desalination layer forming one of the electrodes. One preferred material for the electrode comprising the active or desalination layer 4 is graphene. However, another suitable material is titanium. The substrate of the electrode may consist, for example, of a mesh, a plate, a fabric formed of fibers or a sintered body. A dielectric layer may also be incorporated in the membrane between the electrodes. The layers may be interconnected and may be manufactured by techniques such as casting or printing, gluing or growing.

[0094] The electrodes (anode and / or cathode) may also be at least partially coated with at least one catalyst, such as those selected from the group consisting of iridium oxide, ruthenium oxide, tantalum oxide, titanium oxide, platinum, and platinum oxide, and any combination thereof.

[0095] In embodiments in which the electrode comprises graphene or carbon fiber / cloth, the carbon substrate is preferably coated with a mixed metal oxide (MMO) selected from Pt, Ir, Pt-lr and Ru metals, and any combination thereof.

[0096] Preferably, carbon is the substrate for coating with mixed metal oxides (MMO) selected from platinum (Pt), iridium (Ir), Pt-lr, ruthenium (Ru) metals and any combination thereof. In these embodiments, MMO / C electrodes can be prepared by a two-step process consisting of forming a sacrificial copper or nickel layer on carbon by electroless or electrodeposition, and replacing the sacrificial metal with Pt, Ir, Ru or Pt-lr.

[0097] The present application is equally suitable for two-electrode systems, three-electrode systems or systems with more than two electrodes, such as a cathode, an anode and a reference electrode. Additional non-removing layers (membranes) can be placed near the electrodes.

[0098] As known in the art, feed spacers are used in spiral wound reverse osmosis membrane modules to separate the membrane sheets and promote mixing. Feed spacers are beneficial to membrane performance but increase pressure drop. Feed spacers are mesh-like materials placed between flat sheets of reverse osmosis membrane to promote turbulence in the feed / retentate flow. Feed spacers are typically made of plastic polypropylene.

[0099] Permeate or flow channel spacers are also called "permeate carriers" or "mesh spacers". In the construction of the membrane element, the permeate spacer is placed between two layers of flat sheet membrane. This spacer is used to prevent the RO membrane from closing during high pressure operation. The permeate flows in a spiral path across the product flow channel spacer into the product recovery tube. The permeate spacer is inside the envelope and forms the permeate flow channel. In addition, to mechanically support the membrane sheet against the (high) feed pressure, it is made of a woven spacer with low permeability to provide the necessary rigidity. Typically, the permeate or flow channel spacer is woven from a thin plastic (e.g., a knitted fabric called tricot).

[0100] It will be appreciated that the electrodes (anode and / or cathode) may also include a feed or permeated spacer as described above, at least partially coated with, for example, a conductive layer to render the spacer electrically conductive and / or a catalyst layer to render it electrocatalytically active as the anode (O2 evolution) or cathode (H2 evolution) or both. The catalyst may be, for example, Pt, Ir, Ni, Cu metal, or combinations thereof.

[0101] Alternatively, the electrodes (either anodes or cathodes) may be coupled to a permeate spacer or feed spacer that mechanically cooperates with the permeate tube. An example of such an embodiment is shown in Figure 10 of the accompanying drawings, where two electrodes 402 are coupled to a spacer attached to one end of a permeate tube 400. Any number of electrodes and spacers may be provided, with twenty electrodes 402 coupled to a spacer that is coupled at one end to the permeate tube 400, as shown in Figure 11.

[0102] According to another embodiment of the invention, the infiltrate and / or feed spacer are clad with titanium foil, with or without an additional electrical conductor between the titanium foil and the plastic spacer, so the electrode is essentially titanium foil clad.

[0103] Refer now to FIG. 12, which shows a titanium foil cladding 300 for infiltrating and / or powering the spacer, with and without an additional conductor between the titanium foil and the plastic spacer. In the example shown in FIG. 12, the titanium foil 300 is cladded to the penetrant spacer 41. However, as defined above, such cladding can be done for the feed spacer 40 as well. According to one embodiment, the cladding is done on one side of the penetrant spacer and / or feed spacer. According to another embodiment, such cladding is done on both sides of the penetrant spacer and / or feed spacer.

[0104] According to one embodiment, the cladding is performed by applying a vacuum. According to such an embodiment, the foil is placed on one side of the infiltrate spacer and / or feed spacer and a vacuum is applied to the other side. Such suction causes the titanium foil 300 to adhere to the infiltrate and / or feed spacer. The thickness of such titanium foil 300 can be varied depending on the required electrical conductivity.

[0105] According to another embodiment, in addition to the titanium foil cladding 300, electrical wires can be added to allow for electrical current transmission, as can be seen in Figure 12. Thus, as seen in Figure 12, according to one embodiment, electrical wires 301 are also added to the penetrant spacer 41.

[0106] The method of water separation carried out in the membrane can be carried out using any one of the conventional techniques of water electrolysis such as water electrolysis (WE), PEM electrolysis, microbial electrolysis, solid oxide electrolysis, alkaline electrolysis, etc. Thus, the present invention is not limited to one particular process of water splitting.

[0107] To remove the gases from the membrane system, different types of hydrogen and oxygen exhaust systems (not shown in the drawings) can be applied. Preferably, hydrogen and oxygen are exhausted from the membrane element or module together with the water stream from which they were generated. Extraction of hydrogen and oxygen is then performed in a degasser. Since the solubility of hydrogen and oxygen in water is very different, the degasser is able to extract hydrogen at the pressure at which the oxygen is dissolved. The oxygen is sent together with the water stream to a subsequent degasser at a lower gauge pressure where the oxygen is extracted. Alternatively, gas separation membranes can be used.

[0108] According to the present invention, low-salinity water such as seawater, brine, and brackish water that is produced during water treatment can be electrochemically separated and added to the treated water to supply hydrogen.

[0109] In embodiments utilizing RO type membranes for desalination of feed water, multiple membrane elements can be provided in an RO module, with the feed seawater being concentrated as it passes from one membrane element to the next in the module. For example, seawater may have a TDS of 3.5% at the first membrane element in the module and 8% TDS at the eighth membrane element. Membrane elements with different salinities electrolyze water differently. The electrical system can be adjusted to provide different currents (voltages) to the different membranes in the module.

[0110] Typically, one RO module contains 5 to 8 membrane elements. It is desirable to install water separation electrodes only on the first few membrane elements in the pressure vessel, where the permeate has a low dissolved solids content, low electrical conductivity, and high separation efficiency.

[0111] Preferably, only a portion of the desalted permeate stream produced during the RO process, at most 5%, preferably less than 2.5%, is separated into hydrogen and oxygen, which provides the important technical advantage that the permeate is free of dissolved suspended solids.

[0112] Figure 7 of the accompanying drawings shows a conventional seawater desalination plant, which may be modified to include electrode-equipped membranes to provide a dual seawater desalination and hydrogen production plant. Briefly, seawater SW is pumped via an intake channel 101 through various pre-treatment sites 102, 103, 104, 105 and through multiple reverse osmosis passes 110, 112 by pumps 108 to form desalinated product water 114 and concentrated seawater or brine 116. The product water is subjected to post-treatment 118 and held in a holding tank 120, while the brine 116 is discharged to the sea via a discharge channel 122.

[0113] Each reverse osmosis path 110, 112 is comprised of a number of membrane elements 201, one of which is illustrated and enlarged in FIG. 8. A central perforated product tube 202 runs through the center of each element and is surrounded by a sheet of semipermeable membrane 204 wrapped around the tube and separated therefrom by a feed spacer sheet 206 and a permeate spacer sheet 208. Both ends are provided with anti-drop caps 210. As described above, a raw saline feed solution is fed into one end of the element 201 to provide a permeate stream 114 and a retentate stream 116 with a permeate flow PF through the layers of the element. Electrodes (not shown) may be incorporated within the element to allow electrochemical separation of the raw brine and / or permeate to produce a minor output of hydrogen production (not shown) along with a main output of retentate stream 116 and / or permeate product 114.

[0114] The process and system for simultaneous water treatment and electrochemical separation according to the present invention addresses many of the problems associated with prior art production of hydrogen from seawater and other water sources.

[0115] For example, the probability of cathodic deposition of CaCO3, Ca(OH)2, Mg(OH)2 and other species in the hybrid reactor proposed by the applicant for water treatment and H2 co-production is significantly low due to (i) the very low current density, (ii) the very high water flux, and (iii) the pH buffering capacity of seawater (only relevant if the cathode is placed in the feed and / or concentrate compartments).

[0116] Furthermore, the chlorine evolution reaction in seawater electrolysis may be suppressed due to the very small anode current density of 1 mA / cm2.

[0117] This is illustrated in Figure 8 of the accompanying drawings, which is a graph of the reversible potentials for the chlorine evolution, oxygen evolution, and hydrogen evolution reactions as a function of pH. - ]=20g / L, gas fugacity=1, no complexation, infinite dilution. This is typical of seawater electrolysis conditions (i.e., [Cl - Figure 8 shows the reversible potentials (vs. SHE) for oxygen evolution (Eq. (3) above), chlorine evolution (Eq. (6) above), and hydrogen evolution (Eq. (4) above) as a function of pH at pH = 20 g / L, gas fugacity = 1, no complexation effects, infinite dilution. In a WE, the electrode potential for the anodic reaction must be higher than the reversible potential. For cathodic H2 production, the cathodic potential must be lower than the reversible potential for this reaction. As shown in Figure 8, the minimum cell potential (i.e., the potential difference between the anode and cathode) required for chlorine evolution in seawater (pH = 8.1) is 1.78 V. On the other hand, the minimum cell potential required for oxygen evolution at the anode and hydrogen evolution at the cathode is only 1.23 volts. As a result, there exists a range of cell potentials where only oxygen is evolved at the anode and hydrogen is evolved at the cathode. This maximum cell potential typically limits the anodic current density to a very low current density of only a few mA / cm2. In alkaline water electrolysis, current densities of 200 to 400 mA / cm2 and in PEM water electrolysis, current densities of 600 to 2000 mA / cm2 are common, and chlorine generation is an issue. In contrast, in the present invention, the current density is very small, making it possible to suppress chlorine generation.

[0118] Moreover, the proposed technology has the same thermodynamics as conventional water electrolysis processes. In general, operation at high current densities (i.e., high production rates per reactor volume) requires higher energy input (or cell potential), while the energy / H2 ratio increases at high current densities. In other words, the very low current densities utilized in the process of the present invention are expected to lower the electrical energy consumption for hydrogen production compared to the state of the art. The main reasons for this lower energy consumption are: (1) lower activation overpotentials are required to achieve lower current densities, (2) mass transport is very effective in the proposed system, so that diffusion and concentration overpotentials are very low, and (3) gas evolution occurs without the formation of bubbles. The last reason is the relatively low H2 and O2 production rates and very high water flow rates that result in complete dissolution of the product gases. Conventional water electrolysis systems cannot be operated at very low current densities because the footprint and construction costs of the H2 production system would be unreasonably high.

[0119] In this regard, one of the main requirements for modern water electrolysis processes is low energy consumption at sufficient (i.e., above 200 mA / cm2) current densities. High current densities are necessary to reduce construction costs, footprint and the amount of expensive materials such as catalysts, membranes and bipolar plates. Simply put, the construction of conventional large water electrolyzers operated at very low current densities is economically unfeasible, as the construction costs are so high that the benefits of low energy consumption are diminished.

[0120] However, the present invention allows the incorporation of a hydrogen production process into a conventional water desalination / filtration system without increasing its size or significantly decreasing its water treatment performance. For example, the permeate and feed spacers of RO, NF, UF, and FO modules, as well as the membrane layers of NF, MF, and UF membranes, can be used as they are today for the separation of anodes and cathodes incorporated therein to provide the desired hydrogen generation. As a result, the capital cost of the proposed H2 production system is expected to be relatively low, since it utilizes materials, water pretreatment systems, and other units already present in the pressure-driven membrane filtration process.

[0121] Another important potential advantage of low current density operation is the possibility to apply cheaper catalysts, since higher current densities usually lead to faster catalyst wear rates. This is an important reason for the use of precious metal catalysts in conventional PEM electrolysers. In summary, despite the fact that the proposed technology requires the use of larger amounts of materials (per unit volume of hydrogen produced), the attributable hydrogen cost is expected to be lower than that of conventional WE processes due to the longer service life and significantly lower prices of materials.

[0122] A conventional water electrolysis electrode consists of a very thin (a few microns) catalytic layer, the "real electrode," and a secondary layer such as a gas diffusion layer (GDL). The GDL provides fast mass transport of gaseous products from the electrode and is used to drive electrons to and from the electrode. The GDL in modern PEM water electrolyzers contains hydrophobic particles for fast transport of gaseous species. Next to the GDL is a current collector, which provides the flow of electrons to and from the GDL and catalytic layer. The current collector contains a flow field to distribute water over the electrode surface and to collect the evolved gases. The current collector is usually 3 mm or thicker and is made of a highly conductive material (e.g. graphite, composites of polymers and conductive particles, metals, etc.).

[0123] In contrast, the electrodes of the electrolysis cell proposed by the applicant's semipermeable membrane must be made of relatively long (i.e., up to 100 cm inside the membrane) and relatively thin (nominally up to 100 μm) conductive fibers. Such a geometry is almost impossible for conventional WEs operated at high current densities because of the high resistance of fiber-type electrodes. However, simple calculations show that this fiber-type geometry is applicable to the system and process proposed herein. Assumptions: electrode thickness = 100 μm, membrane area = 100–100 cm cm, percentage of cross section occupied by electrodes = 50%, current density = 3 mA / cm 2 , the effective electrolytic area is equal to the membrane area.

[0124] Considering the above parameters, the cross-sectional current density (ratio of current to cross-sectional area of ​​fiber electrode) is = 0.6A / mm 2 This means that if the electrical conductivity of the electrode is 1.27·105 (S / m) (typical of graphite in the basal plane), then the ohmic voltage drop across a 100 cm long electrode at a current of 30 A is only 50 mV. This simple calculation shows that the proposed electrochemical cell is feasible if the fiber-type electrodes are made of a material with high electrical conductivity (i.e., in the range of stainless steel or titanium).

[0125] Figure 9 of the accompanying drawings illustrates one scheme in which the hydrogen production system described herein may be incorporated. In particular, in this scheme, green energy may be produced using osmotic power generation from a salt dome, which is then utilized for water separation as previously described herein, followed by storage of hydrogen in the empty salt caverns. In this manner, the present invention provides a highly energy efficient method for producing green energy in the form of hydrogen.

[0126] The plan includes three cycles: cycle 100, which involves efficient energy production by the PRO using different salinity concentrations between seawater 2 and dissolved brine from the salt dome 26; cycle 200, which involves hydrogen production by electrolysis of water using electricity generated in cycle 100; and cycle 300, which discharges the hydrogen produced in cycle 200 and supplies it for storage in the salt dome cavern 35 formed during salt extraction by the PRO in cycle 100.

[0127] More specifically, the cycle 100 uses a pressure retarded osmosis process (PRO) to generate electricity. The PRO is driven by the difference in salinity between 10-25% high-concentration salt dissolved from the salt dome 26 (draw solution DS) and 3.6-4.5% seawater (feed solution FS). Optional dissolution of salt rock in the salt cavern 26 can be carried out under high gas pressure PGr of about 200 bar to form a draw solution. Alternatively, dissolution can be carried out at atmospheric pressure. This draw solution is pumped by pump 25 via line 23 to the first PRO module 100 and enters the first side of the module 100 via first side inlet 22. The feed stream (FS) enters the second side of the PRO module 100 via inlet 20. A portion of the feed stream permeates from the second side to the first side of the membrane 3 as a low salinity permeate and mixes with the draw solution. The mixture of the draw solution and the permeate exits the module 100 through outlet 23. A portion of this mixture is directed to turbine 27 for generating electricity.

[0128] The remainder of the feed stream is discharged from module 100 via outlet 21 into the environment (eg, the sea as shown in FIG. 5).

[0129] Electricity generated in a turbine 27 or similar device from the output from the module 100 is then directed to a forward osmosis (FO) module 200 as an energy source for electrochemically separating water into hydrogen and oxygen, low salinity water for the water separation being provided from the FO process, the separation being achieved by incorporating a membrane according to the invention into a module having electrodes for carrying out the electrolysis. Seawater 2 can be used as the feed liquid 30.

[0130] Module 200 FO is structurally similar to PRO module 100. The transfer of the permeate stream from the feed side to the draw side of the membrane also takes place under the balance of osmotic and gauge pressures Por, POf, PGr, PGf. However, the difference between modules 100 and 200 lies in the gauge pressures PGr, PGf. In module 200, PGr and PGf are lower, and the transfer of the permeate from the FS side to the DS side mostly takes place under the difference of osmotic pressures POr' and POf. The membrane has electrodes (9, 10 in Figs. 1A to 4) and, optionally, further reference electrodes (not shown in the drawings). These electrodes, together with the electrical power from module 100, allow the decomposition of the low salinity permeate stream to produce hydrogen and oxygen. Any residual water 33 can be returned to the sea 2.

[0131] Semipermeable membranes incorporating electrodes according to the present invention can be installed in modules 100 and 200, allowing water separation to occur simultaneously in modules 100 and 200. Alternatively, electrodes can be installed only in module 100 or only in module 200.

[0132] After hydrogen production in cycle 200, the hydrogen is stored in the salt dome caverns 35 produced during salt extraction in the PRO process 100.

[0133] The integration of electrochemical hydrogen production into RO membrane or UF / MF filtration processes offers significant and surprising advantages compared to prior art electrochemical treatment of water. The integration of water treatment and hydrogen production processes into one module is expected to significantly reduce the operating and capital costs of hydrogen gas production and create added value for water treatment facilities. The proposed technology is expected to have significantly lower energy consumption than traditional water electrolysis technologies. The hybrid process can be operated using inexpensive catalysts with very long operational lives. These novel and inventive systems and methods according to the present invention use the same hybrid reactor to simultaneously perform pressure-driven membrane filtration of water (e.g., reverse osmosis, forward osmosis, nanofiltration, ultrafiltration) and electrochemical splitting of water.

[0134] It should be understood that changes can be made in the films, processes and systems described above without departing from the principles embodied in the examples described and illustrated herein.

Claims

1. A membrane element configured to filter water while co-producing hydrogen, comprising: a membrane element including at least one anode electrode and at least one cathode electrode, each in communication with said membrane, said membrane further adapted to electrolyze at least a portion of said water to at least partially produce hydrogen therefrom.

2. 10. The membrane element of claim 1, wherein the membrane is configured to filter water when a pressure differential is provided across the membrane.

3. 10. The membrane element of claim 1, wherein the membrane is configured for osmotic and / or gauge pressure driven filtration of water.

4. 10. The membrane element of claim 1, wherein the membrane is a selective osmosis membrane configured to at least partially purify a feed water when a pressure differential is provided across the membrane.

5. 10. The membrane element of claim 1, wherein at least one selected from the group consisting of the at least one anode electrode, the at least one cathode electrode, and any combination thereof is made of at least one material selected from titanium, carbon fiber, carbon cloth, graphene, and any combination thereof.

6. 2. The membrane element of claim 1, wherein at least one selected from the group consisting of the at least one anode electrode, the at least one cathode electrode, and any combination thereof is at least partially coated or at least partially clad with at least one catalyst.

7. 7. The membrane element of claim 6, wherein the catalyst is selected from the group consisting of iridium oxide, ruthenium oxide, tantalum oxide, titanium oxide, platinum, and platinum oxide, and any combination thereof.

8. 2. The membrane element of claim 1, wherein at least one selected from the group consisting of the at least one anode electrode, the at least one cathode electrode, and any combination thereof is provided in the form of at least one selected from the group consisting of a mesh, a plate, a fabric, a fiber, a sintered body, and any combination thereof.

9. 9. The membrane element according to claim 1, wherein the membrane comprises a salt rejection layer and a support layer, and at least one anode electrode and / or at least one cathode electrode is provided with a salt rejection layer.

10. 10. The membrane element according to claim 1, wherein the membrane element comprises at least one selected from the group consisting of a feed spacer, a permeate spacer, and any combination thereof, and at least one anode electrode and / or at least one cathode electrode is provided by a feed spacer or a permeate spacer, provided on one or the other of the feed spacer and / or the permeate spacer, or is bonded to at least one selected from the group consisting of a feed spacer, a permeate spacer, or is at least partially coated on at least one selected from the group consisting of a feed spacer, a permeate spacer, and combinations thereof.

11. The membrane element according to any one of claims 1 to 10, wherein at least one electrode is formed from graphene.

12. A membrane element according to any one of claims 1 to 11, wherein at least one electrode is provided in the form of a grid or parallel spaced apart strips.

13. 13. The membrane element of claim 12, wherein at least one electrode is in the form of a full or partial coating, or a full or partial cladding, of the permeate spacer and / or the feed spacer.

14. 14. The membrane element according to claim 1, wherein a catalyst is provided on one or both of the anode electrode and the cathode electrode.

15. 15. The membrane element of any one of claims 1 to 14, further comprising recovery means for recovering dissolved hydrogen in the product water or any reject stream for subsequent degassing or extraction by gas membrane separation.

16. The membrane element according to any one of claims 1 to 15, wherein the water filtration process is selected from the group consisting of reverse osmosis, pressure retarded osmosis (PRO), forward osmosis (FO), ultrafiltration, microfiltration, and nanofiltration.

17. 100 mA / cm between the electrodes to allow electrochemical separation of water 2 A low current density of less than 10 mA / cm is applied. 2 Less than 5 mA / cm 2 Ideally, it should be less than 1 mA / cm 2 The membrane element according to any one of claims 1 to 15, wherein:

18. 1. A method for generating hydrogen during a pressure-driven seawater desalination process, comprising: a. supplying a feed water to at least one membrane comprising at least one anode electrode and at least one cathode electrode and in communication with said membrane; b. filtering the water while co-producing hydrogen; wherein the co-producing hydrogen step comprises applying either a potential difference or a current between the at least one anode electrode and the at least one cathode electrode, thereby producing hydrogen and oxygen by electrolysis from at least a portion of at least one selected from the group consisting of feed water, product water, and any combination thereof.

19. 20. The method of claim 18, wherein filtering the water further comprises applying a pressure differential across the membrane to draw feed water through the membrane to form product water.

20. 20. The method of claim 18, wherein at least one selected from the group consisting of the at least one anode electrode, the at least one cathode electrode, and any combination thereof is made of at least one material selected from titanium, carbon fiber, carbon cloth, graphene, and any combination thereof.

21. 20. The method of claim 18, wherein at least one selected from the group consisting of the at least one anode electrode, the at least one cathode electrode, and any combination thereof is at least partially coated or at least partially clad with at least one catalyst.

22. 20. The method of claim 18, wherein the catalyst is selected from the group consisting of iridium oxide, ruthenium oxide, tantalum oxide, titanium oxide, platinum, and platinum oxide, and any combination thereof.

23. 20. The method of claim 18, wherein at least one selected from the group consisting of the at least one anode electrode, the at least one cathode electrode, and any combination thereof is provided in the form of at least one selected from the group consisting of a mesh, a plate, a fabric, a fiber, a sintered body, and any combination thereof.

24. 24. The method of any one of claims 18 to 23, further comprising recovering dissolved hydrogen in the product water or any reject stream for subsequent extraction by degassing or gas membrane separation.

25. 25. The method according to any one of claims 18 to 24, wherein the water filtration process is selected from the group consisting of reverse osmosis, pressure retarded osmosis (PRO), forward osmosis (FO), ultrafiltration, microfiltration, and nanofiltration.

26. 100 mA / cm between the electrodes to allow electrochemical separation of water 2 A low current density of less than 10 mA / cm is applied. 2 Less than 5 mA / cm 2 Ideally, it should be less than 1 mA / cm 2 The method according to any one of claims 18 to 25, wherein the

27. 1. A water filtration module configured for pressure-driven filtration of water and electrochemical decomposition of at least a portion of the water for co-generation of hydrogen, comprising: A water inlet, At least one membrane element according to any one of claims 1 to 17; A produced water outlet; Optionally, a reject water outlet; A water filtration module comprising:

28. 28. The module of claim 27, wherein the membrane comprises a salt rejection layer and a support layer, and at least one anode electrode and / or at least one cathode electrode comprises the salt rejection layer and / or is disposed in, on or between one or both of the salt rejection layer and the support layer.

29. 29. The module of any one of claims 27 to 28, wherein the membrane elements comprise at least one selected from the group consisting of feed spacers, permeate spacers, and any combination thereof, and at least one anode electrode and / or at least one cathode electrode is provided by a feed spacer or a permeate spacer, or is provided on or adjacent to one or the other of a feed spacer and / or a permeate spacer, or is bonded to at least one selected from the group consisting of a feed spacer, a permeate spacer, or is at least partially coated by or at least partially clad with at least one selected from the group consisting of a feed spacer, a permeate spacer, and combinations thereof.

30. 30. The module of any one of claims 27 to 29, wherein at least one electrode is formed from graphene.

31. A module according to any one of claims 27 to 30, wherein at least one electrode is provided in the form of a grid or parallel spaced apart strips.

32. 30. The module of claim 29, wherein at least one electrode is in the form of a full or partial coating (coat) or a full or partial coating (cladding) of the permeation spacer and / or the feed spacer.

33. The module according to any one of claims 27 to 32, wherein one or both of the anode and cathode electrodes are provided with a catalyst.

34. 34. The module of any one of claims 27 to 33, further comprising recovery means for recovering dissolved hydrogen in the product water or any reject stream for subsequent extraction by degassing or gas membrane separation.

35. The module of any one of claims 27 to 34, wherein the water filtration process is selected from the group consisting of reverse osmosis, pressure retarded osmosis (PRO), forward osmosis (FO), ultrafiltration, microfiltration, and nanofiltration.

36. 100 mA / cm to allow electrochemical splitting of water to occur 2 A low current density of less than 10 mA / cm is applied between the electrodes. 2 Less than 5 mA / cm 2 Ideally, it should be less than 1 mA / cm 2 The module of any one of claims 27 to 35, wherein the module is less than

37. A pressure-driven water purification system with hydrogen cogeneration, comprising: A water inlet, At least one membrane element according to any one of claims 1 to 17 or a module according to any one of claims 27 to 36, at least one pump for applying pressure to the water supply; A power source that applies a potential difference to the electrodes of the membrane element; a product water outlet and an optional reject outlet; a hydrogen outlet in the product and / or reject stream; A system including:

38. 1. A pressure-driven water purification process with cogeneration of hydrogen, comprising: Supplying feed water to the membrane element according to any one of claims 1 to 17 or the module according to any one of claims 27 to 36 through a feed water inlet; applying a pressure differential across the permselective membranes of the membrane elements to draw the feed water through the membranes to form a product water and, optionally, a reject stream; applying a potential difference between electrodes of the membrane element to electrochemically decompose at least a portion of at least one of the feed water and / or the product water to form hydrogen and oxygen; recovering product water and optionally a reject stream, and hydrogen; A process including.

39. 40. The process of claim 38, further comprising recovering dissolved hydrogen in the product water or any reject stream for subsequent extraction by degassing or gas membrane separation.

40. 40. The process of any one of claims 38 to 39, wherein the pressure driven water filtration process is selected from the group consisting of reverse osmosis, pressure retarded osmosis (PRO), forward osmosis (FO), ultrafiltration, microfiltration and nanofiltration.

41. 41. A process according to any one of claims 38 to 40, wherein less than 5% of the feed water and / or product water is separated to form hydrogen, preferably less than 1%, more preferably less than 0.05%, in particular less than 0.01%, ideally less than 0.01%.

42. 100 mA / cm between the electrodes to allow electrochemical separation of water 2 A low current density of less than 10 mA / cm is applied. 2 Below, especially 5mA / cm 2 Ideally, less than 1mA / cm 2 The process according to any one of claims 38 to 41, wherein:

43. 43. The process of any one of claims 38 to 42, further comprising the steps of: supplying a feed solution and a draw solution having different osmolality and gauge pressures to opposite sides of a permselective membrane element; separating the low salt solution into hydrogen and oxygen by passing an electric current between electrodes of the membrane; and recovering the hydrogen and oxygen.

44. the membrane is an RO-type membrane having a first side and a second side opposite the first side; a first saline solution comprising a draw solution having an osmolality POr and a gauge pressure PGr for entering a first side of the membrane; a second saline solution comprising a feed solution having an osmolality POp and a gauge pressure PGp for entering the second side of the membrane; at least a portion of the feed solution from the second side of the membrane permeates the first side according to a net driving pressure defined by the balance of pressures PGr, POr, Pop and PGp; the draw solution and a portion of the permeate feed solution exit the first side of the membrane via a retentate brine outlet as a retentate brine stream; the remainder of the feed solution at least periodically exits the second side of the membrane via the outlet as a residual fluid vapor; 44. The process of claim 43, wherein at least a portion of the low salt solution stream passes from the second side to the first side for decomposition into hydrogen and oxygen as it passes through the membrane.

45. the membrane is an RO-type membrane having a first side and a second side opposite the first side; a first saline solution comprising a draw solution having an osmolality POr and a gauge pressure PGr for entering a first side of the membrane; a second saline solution comprising a feed solution having an osmolality POp and a gauge pressure PGp for entering the second side of the membrane; at least a portion of the feed solution from the second side of the membrane permeates the first side according to a net driving pressure defined by the balance of pressures PGr, POr, Pop and PGp; the draw solution and a portion of the permeate feed solution exit the first side of the membrane via a retentate brine outlet as a retentate brine stream; the remainder of the feed solution at least periodically exits the second side of the membrane via the outlet as a residual fluid vapor; 44. The process of claim 43, wherein at least a portion of the first saline solution and / or the second feed solution is electrochemically separated into hydrogen and oxygen as it passes along the membrane.

46. 46. ​​The process of any one of claims 38 to 45, further comprising generating electricity using pressure retarded osmosis, where the draw solution is provided by dissolving rock salt in a salt dome.

47. 47. The osmotic process of claim 46, wherein the dissolution of rock salt is carried out under a pressure equal to or close to PGr.

48. 48. The osmotic process of any one of claims 38 to 47, further comprising storing the produced hydrogen in a salt dome.

49. 39. A system for producing hydrogen and oxygen from water as claimed in claim 38, comprising: The system further includes a housing having at least one RO-type membrane having at least two electrodes with a cathode and an anode, the membrane having a first side and a second side opposite the first side, a first inlet for supplying a first saline solution having a draw solution having an osmotic pressure POr and a gauge pressure PGr to enter the first side of the membrane, a second inlet for supplying a second saline solution having a feed solution having an osmotic pressure POP and a gauge pressure PGp to enter the second side of the membrane, and at least a portion of the feed solution from the second side of the membrane is supplied through a pressure a first side according to a net driving pressure defined by the balance of PGr, POr, POp and PGp, the permeated portions of the draw solution and the feed solution exiting the first side of the membrane as a residual brine stream via a residual brine outlet, and the remainder of the feed solution exiting, at least periodically, the second side of the membrane as a residual fluid vapor via an outlet, forming a low-salinity solution stream which passes from the second side to the first side, and the membrane electrodes serving to separate at least a portion of the low-salinity solution stream into hydrogen and oxygen as it passes through the RO type membrane, in the system.

50. 39. A system for producing hydrogen and oxygen from water as claimed in claim 38, comprising: The system further includes a housing having at least one RO-type membrane having at least two electrodes with a cathode and an anode, the membrane having a first side and a second side opposite the first side; a first inlet for supplying a first saline solution comprising a draw solution having an osmotic pressure POr and a gauge pressure PGr for entering a first side of the membrane; a second inlet for supplying a second saline solution comprising a feed solution having an osmotic pressure POP and a gauge pressure PGp for entering a second side of the membrane; at least a portion of the feed solution from the second side of the membrane permeates into the first side according to a net driving pressure defined by the balance of the pressures PGr, POR, POp and PGp; a portion of the draw solution and the permeated feed solution exiting the first side of the membrane via a residual brine outlet as a residual brine stream, and a remainder of the feed solution exiting, at least periodically, from the second side of the membrane via an outlet as a residual fluid stream, such that a low-salinity solution stream is formed and passes from the second side to the first side; and an electrode of the membrane serves to separate at least a portion of the first saline solution and / or the second saline solution into hydrogen and oxygen as they pass along the RO type membrane.

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