Patent Publication Number: US-2022226552-A1

Title: Automatic recharger brine preparation from a salt cartridge

Description:
FIELD 
     The disclosure relates to systems and methods for generating a brine solution using a salt cartridge for recharging zirconium phosphate in a reusable sorbent module. The salt cartridge can include an inlet and an outlet on a first and second side. Water can be pumped through the salt cartridge to dissolve the salts in the salt cartridge and the resulting solution can be collected as a brine solution for use in recharging the zirconium phosphate. 
     BACKGROUND 
     Sorbent based dialysis systems can use zirconium phosphate as a sorbent material to remove potassium, calcium, and magnesium ions from spent dialysate. The zirconium phosphate is generally provided in a sorbent cartridge with other sorbent materials. After use, the spent zirconium phosphate is disposed or removed from the sorbent cartridge for further processing. However, removing spent zirconium phosphate from a sorbent cartridge, separating the zirconium phosphate from other sorbent materials and processing the spent zirconium phosphate requires significant time and expense. Further, large quantities of solutions for processing the spent zirconium phosphate can be required along with the processing infrastructure, storage, and transportation. Expensive manufacturing lines and plants are required to generate pre-made solutions for use in processing the zirconium phosphate. 
     Hence, there is a need for systems and methods that can recharge zirconium phosphate within a reusable sorbent module. There is further a need for systems and methods for generating the recharge solutions necessary for recharging the zirconium phosphate, and in particular, brine solutions. There is a need for systems and methods that can generate the brine solution on-line and quickly, reducing the manufacturing burden, and reducing the storage needs and time required for preparation and recharging. 
     SUMMARY OF THE INVENTION 
     The problem to be solved by the present invention is online preparation of a brine solution for use in recharging sorbent materials. The solution can include sodium chloride and sodium acetate in a salt cartridge. The sodium chloride and sodium acetate can be dissolved when needed to generate the brine solution. 
     The first aspect of the invention relates to a system. In any embodiment, the system can include a sorbent recharger; the sorbent recharger having: i) a receiving compartment for a zirconium phosphate sorbent module; ii) at least a first fluid line fluidly connectable to an inlet of the zirconium phosphate sorbent module in the receiving compartment; iii) at least a second fluid line fluidly connectable to an outlet of the zirconium phosphate sorbent module; and iv) at least one pump. The system can also include a brine container fluidly connectable to the first fluid line; a salt cartridge; the salt cartridge having an inlet fluidly connectable to a water source and an acetic acid source; and an outlet fluidly connectable to the brine container; the salt cartridge containing sodium chloride and sodium acetate; and a control system; the control system programmed to: i) pump a preset volume of fluid from the water source through the salt cartridge; ii) recirculate fluid in a first flow path from the outlet of the salt cartridge to the brine container and then to the inlet of the salt cartridge; and to pump a preset volume of acetic acid into the first flow path. 
     In any embodiment, the inlet of the salt cartridge can be on a top of the salt cartridge, and the outlet of the salt cartridge can be on a bottom of the salt cartridge. 
     In any embodiment, the salt cartridge can include a first filter pad in the salt cartridge between the inlet of the salt cartridge and the sodium chloride and sodium acetate. 
     In any embodiment, the salt cartridge can include a filter pad in the salt cartridge between the sodium chloride and sodium acetate and the outlet of the salt cartridge. 
     In any embodiment, the salt cartridge can include a solution diversion base; wherein the outlet of the salt cartridge is below the solution diversion base. 
     In any embodiment, the control system can be further programmed to pump fluid from the brine container through the zirconium phosphate sorbent module. 
     In any embodiment, the control system can be programmed to recirculate fluid in the first flow path until a homogeneous solution is generated in the first flow path. 
     In any embodiment, the control system can be programmed to recirculate fluid in the first flow path for a preset period of time. 
     In any embodiment, the salt sodium chloride and sodium acetate can be initially solid. 
     In any embodiment, the sodium chloride and sodium acetate can be below a bottom of the inlet of the salt cartridge. 
     In any embodiment, the salt cartridge can include a spring-loaded valve at the inlet. 
     In any embodiment, the salt cartridge can include a spring-loaded valve at the outlet. 
     The features disclosed as being part of the first aspect of the invention can be in the first aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. Similarly, any features disclosed as being part of the first aspect of the invention can be in a second, third, fourth, or fifth aspect of the invention described below, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. 
     The second aspect of the invention relates to a method for generating a brine solution for recharging zirconium phosphate. In any embodiment, the method can include the steps of: pumping water from a water source to a salt cartridge through an inlet of the salt cartridge; the salt cartridge containing sodium chloride and sodium acetate; recirculating fluid from an outlet of the salt cartridge, to a brine container, and back to the inlet of the salt cartridge in a first flow path; pumping acetic acid into the first flow path; and collecting fluid from the first flow path into the brine container to generate the brine solution. 
     In any embodiment, the inlet of the salt cartridge can be on a top of the salt cartridge, and the outlet of the salt cartridge can be on a bottom of the salt cartridge. 
     In any embodiment, the salt cartridge can include a first filter pad in the salt cartridge between the inlet of the salt cartridge and the sodium chloride and sodium acetate. 
     In any embodiment, the salt cartridge can include a filter pad in the salt cartridge between the sodium chloride and sodium acetate and the outlet of the salt cartridge. 
     In any embodiment, the brine container can be fluidly connected to a sorbent recharger; and the method can include the step of pumping the brine solution through a zirconium phosphate sorbent module in the sorbent recharger. 
     In any embodiment, the fluid can be recirculated in the first flow path until a homogenous solution is generated. 
     In any embodiment, the fluid can be recirculated in the first flow path for a preset period of time. 
     In any embodiment, the salt sodium chloride and sodium acetate can be initially solid. 
     In any embodiment, the sodium chloride and sodium acetate can be below a bottom of the inlet of the salt cartridge. 
     In any embodiment, a top of the sodium chloride and sodium acetate can be about ¾ of an interior of the salt cartridge. 
     In any embodiment, the salt cartridge can include a solution diversion base; wherein the outlet of the salt cartridge is below the solution diversion base. 
     The features disclosed as being part of the second aspect of the invention can be in the second aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. Similarly, any features disclosed as being part of the second aspect of the invention can be in the first, third, fourth, or fifth aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. 
     The third aspect of the invention is drawn to a salt cartridge for use in recharging zirconium phosphate. In any embodiment, the salt cartridge can include an inlet fluidly connectable to a water source; an outlet fluidly connectable to a brine container; and wherein the inlet is at a top of the salt cartridge and the outlet is at a bottom of the salt cartridge; the salt cartridge containing sodium chloride and sodium acetate. 
     In any embodiment, the salt cartridge can include a filter pad in the salt cartridge between the inlet of the salt cartridge and the sodium chloride and sodium acetate. 
     In any embodiment, the salt cartridge can include a filter pad in the salt cartridge between the outlet of the salt cartridge and the sodium chloride and sodium acetate. 
     In any embodiment, the salt cartridge can include a solution diversion base; wherein the outlet of the salt cartridge is below the solution diversion base. 
     In any embodiment, the salt cartridge can include a spring-loaded valve at the inlet. 
     In any embodiment, the salt cartridge can include a spring-loaded valve at the outlet. 
     The features disclosed as being part of the third aspect of the invention can be in the third aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. Similarly, any features disclosed as being part of the third aspect of the invention can be in the first, second, fourth, or fifth aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. 
     The fourth aspect of the invention is drawn to a sorbent recharger. In any embodiment, the sorbent recharger can include at least one inlet fluidly connectable to a water source; at least one inlet fluidly connectable to a brine container; and at least one outlet fluidly connectable to the salt cartridge of the third aspect of the invention. 
     In any embodiment, the sorbent recharger can include a control system programmed to: (i) pump a preset volume of fluid from the water source into the salt cartridge; (ii) recirculate fluid in a first flow path from the outlet of the salt cartridge to the brine container and then to the inlet of the salt cartridge; and to (iii) pump a preset volume of acetic acid into the first flow path. 
     In any embodiment, the control system can be programmed to recirculate fluid in the first flow path until a homogeneous solution is generated in the first flow path. 
     In any embodiment, the control system can be programmed to recirculate fluid in a first flow path for a preset period of time. 
     The features disclosed as being part of the fourth aspect of the invention can be in the fourth aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. Similarly, any features disclosed as being part of the fourth aspect of the invention can be in the first, second, third, or fifth aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. 
     The fifth aspect of the invention is drawn to a brine container. In any embodiment, the brine container can include an inlet fluidly connectable to the salt cartridge of the third aspect of the invention; and an outlet fluidly connectable to a sorbent recharger. 
     The features disclosed as being part of the fifth aspect of the invention can be in the fifth aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. Similarly, any features disclosed as being part of the fifth aspect of the invention can be in the first, second, third, or fourth aspect of the invention, either alone or in combination, or follow any arrangement or permutation of any one or more of the described elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-I  illustrate a salt cartridge for preparation of a brine solution. 
         FIG. 2  illustrates a sorbent recharger system using a salt cartridge. 
         FIGS. 3A-C  illustrate a sorbent recharger for recharging sorbent materials in reusable sorbent modules. 
         FIG. 4  shows a flow path for a sorbent recharger using a salt cartridge. 
     
    
    
     DETAILED DESCRIPTION 
     Unless defined otherwise, all technical and scientific terms used have the same meaning as commonly understood by one of ordinary skill in the art. 
     The articles “a” and “an” are used to refer to one to over one (i.e., to at least one) of the grammatical object of the article. For example, “an element” means one element or over one element. 
     The term “above” refers to a component that is at a higher elevation than another component when arranged for ordinary use. 
     “Acetic acid” refers to CH 3 CO 2 H in an aqueous solution. 
     An “acetic acid source” can be a solid, fluid, or concentrate source from which acetic acid or an acetic acid solution can be obtained. 
     The term “below” refers to a component that is at a lower elevation than another component when arranged for ordinary use. 
     The term “bottom” refers to a portion of a component intended to be at a lower elevation than a “top” during normal use of the component. 
     A “brine container” is a container for containing a brine solution. 
     A “brine solution” is a solution containing sodium chloride, an acid, and the sodium salt of the acid. 
     To “collect” a fluid can refer to flowing a volume of the fluid into a container. 
     The term “comprising” includes, but is not limited to, whatever follows the word “comprising.” Use of the term indicates the listed elements are required or mandatory but that other elements are optional and may be present. 
     The term “consisting of” includes and is limited to whatever follows the phrase “consisting of.” The phrase indicates the limited elements are required or mandatory and that no other elements may be present. 
     The term “consisting essentially of” includes whatever follows the term “consisting essentially of” and additional elements, structures, acts, or features that do not affect the basic operation of the apparatus, structure or method described. 
     The term “containing” refers to a substance that is within a component or container. 
     A “control system” can be a combination of components that act together to maintain a system to a desired set of performance specifications. The control system can use processors, memory and computer components configured to interoperate to maintain the desired performance specifications. The control system can also include fluid or gas control components, and solute control components as known within the art to maintain performance specifications. 
     A “filter pad” can be a porous pad through which water or aqueous solutions can pass, but that prevents solid materials from passing. 
     A “flow path” is a pathway through which a fluid, gas, or any combination or mixture thereof can travel. 
     A “fluid” is a liquid substance optionally having a combination of gas and liquid phases in the fluid. Notably, a liquid, as used herein, can therefore also have a mixture of gas and liquid phases of matter. 
     A “fluid line” can refer to a tubing or conduit through which a fluid or fluid containing gas can pass. The fluid line can also contain air during different modes of operation such as cleaning or purging of a line. 
     The term “fluidly connectable” refers to the ability of providing for the passage of fluid, gas, or combination thereof, from one point to another point. The ability of providing such passage can be any connection, fastening, or forming between two points to permit the flow of fluid, gas, or combinations thereof. The two points can be within or between any one or more of compartments of any type, modules, systems, components, and rechargers. 
     The term “fluidly connected” refers to a particular state such that the passage of fluid, gas, or combination thereof, is provided from one point to another point. The connection state can also include an unconnected state, such that the two points are disconnected from each other to discontinue flow. It will be further understood that the two “fluidly connectable” points, as defined above, can form a “fluidly connected” state. The two points can be within or between any one or more of compartments, modules, systems, components, and rechargers, all of any type. 
     The terms “generate,” “generating,” “is generated,” and the like refer to forming a solution or substance from constituent parts. 
     The term “homogeneous solution” refers to an aqueous solution wherein the concentration of solutes is substantially identical at all parts of the solution. 
     The term “initially” refers to a state of a component or system prior to a process. 
     The term “inlet” can refer to a portion of container, flow path, or component through which fluid, gas, or a combination thereof can be drawn into the container, flow path, or component. 
     The term “interior” refers to an area inside of a given component or system. 
     The term “outlet” can refer to a portion of container, flow path, or component through which fluid, gas, or a combination thereof can be drawn out of the container, flow path, or component. 
     A “preset period of time” is a length of time that is set prior to a process or step. 
     The term “preset volume” refers to an amount of fluid determined prior to a process. 
     The term “programmed,” when referring to a processor, can mean a series of instructions that cause a processor to perform certain steps. 
     The term “pump” refers to any device that causes the movement of fluids or gases by applying suction or pressure. 
     A “receiving compartment” can be a compartment, section, or chamber of any device or components. In one non-limiting example, the receiving compartment can be within a sorbent recharger into which a sorbent module can be positioned to be recharged. 
     “Recharging” refers to treating a sorbent material to restore the functional capacity of the sorbent material to put the sorbent material back into a condition for reuse or use in a new dialysis session. In some instances, the total mass, weight and/or amount of “rechargeable” sorbent materials remain the same. In some instances, the total mass, weight and/or amount of “rechargeable” sorbent materials change. Without being limited to any one theory of invention, the recharging process may involve exchanging ions bound to the sorbent material with different ions, which in some instances may increase or decrease the total mass of the system. However, the total amount of the sorbent material will in some instances be unchanged by the recharging process. Upon a sorbent material undergoing “recharging,” the sorbent material can then be said to be “recharged.” 
     To “recirculate” refers to moving fluid in a flow loop from a first point through the flow loop and back to the first point. 
     A “salt cartridge” is a container designed to hold solid salts for generation of a brine solution. The salt cartridge can include an inlet on one side for receiving water and an outlet on the opposite side for the formed solution to exit. Fluid can enter the salt cartridge and dissolve the salts to generate the brine solution as the fluid passes through the salt cartridge. 
     The term “sodium acetate” refers to CH 3 CO 2 Na either solid or in an aqueous solution. 
     The term “sodium chloride” refers to NaCl either solid or in an aqueous solution. 
     The term “solid” refers to a material in the solid phase of matter, and can include crystalline, powdered, or any other form of solid material. 
     A “solution diversion base” is a bottom of a component or cartridge that has one or more features causing fluid to flow in a specified pattern. The solution diversion base can cause fluid to evenly disperse over a given area. 
     A “sorbent module” means a discreet component of a sorbent cartridge. Multiple sorbent cartridge modules can be fitted together to form a sorbent cartridge of two, three, or more sorbent cartridge modules. The “sorbent cartridge module” or “sorbent module” can contain any selected materials for use in sorbent dialysis and may or may not contain a “sorbent material” or adsorbent, but less than the full complement of sorbent materials needed. In other words, the “sorbent cartridge module” or “sorbent module” generally refers to the use of the “sorbent cartridge module” or “sorbent module” in sorbent-based dialysis, e.g., REDY (REcirculating DYalysis), and not that a “sorbent material” that is necessarily contained in the “sorbent cartridge module” or “sorbent module.” 
     A “sorbent recharger” or “recharger” is an apparatus designed to recharge at least one sorbent material. 
     A “spring-loaded valve” is a valve controlled by a spring, the valve opens or closes when pressure is placed on the spring. 
     The term “top” refers to a portion of a component intended to be at a higher elevation than a “bottom” during normal use of the component. 
     The term “water source” refers to any source from which potable or non-potable water can be obtained. 
     “Zirconium phosphate” is a sorbent material that removes cations from a fluid, exchanging the removed cations for different cations. 
     A “zirconium phosphate sorbent module” is a sorbent module that contains zirconium phosphate. 
     Brine Preparation from a Salt Cartridge 
       FIGS. 1A-I  illustrate a salt cartridge  101  that can be used to generate brine for recharging zirconium phosphate in a reusable zirconium phosphate sorbent module.  FIG. 1A  is a perspective view of a salt cartridge  101 ;  FIG. 1B  is a front transparent view of the salt cartridge  101 ,  FIG. 1C  is a rear transparent view of an empty salt cartridge  101 ,  FIG. 1D  is an exploded view of the connections to the salt cartridge  101 ,  FIG. 1E  is a transparent close up view of a top of the salt cartridge  101 ,  FIG. 1F  is a transparent close up view of the bottom of the salt cartridge  101 ,  FIG. 1G  is a close up view of a top of the salt cartridge  101 ,  FIG. 1H  is a close up view of a base of the salt cartridge  101 , and  FIG. 1I  is an exploded view of the salt cartridge  101 . 
       FIG. 1A  shows the salt cartridge  101  mounted on a base frame  106 . A base  105  of the salt cartridge  101  can be inserted into the base frame  106  for mounting. A bracket  113  can be included to mount the base frame  106  on a surface or a recharger. The salt cartridge can include a connector  102  positioned at a top of the salt cartridge  101  for connection to a fluid line  103 . Water can be pumped into the salt cartridge  101  through the fluid line  103 . An additional connector (not shown in  FIG. 1A ) can connect to fluid line  104  positioned at a bottom of the salt cartridge  101  for brine solution to be pumped out of salt cartridge  101 . 
     As illustrated in  FIG. 1B , the salt cartridge  101  can include an inlet  114  at the top of the salt cartridge  101  and an outlet  108  at the bottom of salt cartridge  101 . Fluid can flow downwardly through salt cartridge  101  from the inlet  114  to the outlet  108 . The inlet  114  can connect to connector  102 , which in turn connects to fluid line  103 , which is fluidly connectable to both a water source and an acetic acid source (not shown). The outlet  108  can connect to fluid line  104 , which is fluidly connectable to a brine container (not shown). Initially solid salts  110  can be placed in the salt cartridge  101 . A top portion  109  of the salt cartridge  101  can initially be empty. To generate a brine solution, water can be pumped into the salt cartridge  101 . The water passes through a first filter pad  111 . The water wets the entire filter pad  111  and drops onto the solid salts  110 . In certain embodiments, the filter pad  111  can be a foam filter. Other materials known to those of skill in the art can be used for the filter pad  111  as well. Because filter pad  111  is wider than the inlet  114 , the water distribution on the salts  110  is uniform, causing smooth and uniform soaking of the salts  110 . The water can dissolve the sodium chloride and sodium acetate in the salt cartridge  101  and exit through outlet  108 . A second filter pad  112  can be included to prevent larger solid particles from entering outlet  108  or fluid line  104  connected to outlet  108 . The filter pad  112  can be placed between the solid salts  110  and the outlet  108  to filter brine solution exiting the salt cartridge  101 . Fluid travels through the salt cartridge  101  from inlet  114  to outlet  108 , dissolving the salts within the salt cartridge  101  as the fluid flows downwardly through the salt cartridge  101 . 
     After the brine solution exits through the outlet  108  of salt cartridge  101  into fluid line  104 , the generated brine solution can be collected in the brine container (not shown). The brine solution can be recirculated back to inlet  114  of the salt cartridge  101 , through the outlet  108 , and back through the brine container. The brine solution can be recirculated for a preset period of time, or until full dissolution of the solid salts  110  and after a homogeneous solution is formed in the recirculation flow path. As illustrated in  FIG. 1B , the salt cartridge  101  can initially be filled about ¾ full with solid salts  110 , leaving about ¼ of the volume of the salt cartridge  101  in the top portion  109  available for filling with water. This places the salts  110  below the bottom of inlet  114 . However, the actual amount of solid salts initially placed in salt cartridge  101  can vary. For example, the salt cartridge  101  can initially be ½ filled, ⅔ filled, ¼ filled or any other fractional amount depending on the needs of the user. 
       FIG. 1C  is a transparent view of the salt cartridge  101 , including inlet  114  at the top of the salt cartridge  101  and an outlet  108  at the bottom of salt cartridge  101 . The salt cartridge  101  includes a first filter pad  111  at a top portion of the salt cartridge  101  and a second filter pad  112  in the bottom portion of the salt cartridge  101 . The inlet  114  and outlet  108  can include spring loaded valve  118  and spring-loaded valve  119 , respectively. The spring-loaded valves prevent the salt inside the salt cartridge  101  from spilling out. When the salt cartridge  101  is not connected to the system, spring loaded valve  118  and spring-loaded valve  119  are closed. When the salt cartridge  101  is connected to the base frame  106 , pressure is applied to the top and bottom of the salt cartridge  101 , opening spring loaded valve  118  and spring loaded valve  119  to allow fluid into and out of the salt cartridge  101 . Upon connection, connector  102  at the inlet  114  and a connector connecting fluid line  104  to outlet  108  can act similar to plungers, opening spring loaded valve  118  and spring-loaded valve  119  to assist fluid flow. Spring loaded valve  118  and spring-loaded valve  119  also operate as non-return valves during salt preparation. Fluid flow in an out of the salt cartridge  101  can be arrested due to spring loaded valve  118  and spring-loaded valve  119 . 
       FIG. 1D  is an exploded view of the salt cartridge  101 . The base  105  of the salt cartridge  101  can be inserted into base frame  106 . Connector  102  can connect inlet  114  to fluid line  103 . Fluid line  104  can connect to outlet  108 . The base frame  106  can include an opening in the bottom to allow fluid line  104  to connect to the salt cartridge  101 . Frame  107  houses the base frame  106  or cartridge holder of the salt cartridge  101  can be included for carrying or moving the salt cartridge  101 . The base frame  106  can be included to mount the salt cartridge  101 . The base frame  106  holds a bottom  115  the salt cartridge  101  in place during use and provides a space underneath the salt cartridge  101  for connection to fluid line  104 . As illustrated in  FIG. 1D , a bracket  113  can be included to mount the base frame  106  on a surface or a recharger. The base frame  106  acts as a cartridge holder to hold salt cartridge  101  in place an apply pressure to spring loaded valves (not shown in  FIG. 1D ). However, as understood by a person of ordinary skill in the art, alternative methods of mounting the salt cartridge  101  can be used, including hooks or any other method. 
       FIG. 1E  is a close-up view of a top of the salt cartridge  101 . Spring-loaded valve  118  is compressed as pressure is applied when connector  102  is attached to the inlet  114 . The compression of spring-loaded valve  118  allows fluid to flow through fluid line  103  and into the salt cartridge  101 . The fluid wets filter pad  111 , evenly distributing fluid across the salt cartridge  101 . 
       FIG. 1F  is a close-up view of a bottom of the salt cartridge  101 . Spring-loaded valve  119  is compressed as pressure is applied when fluid line  104  is connected to outlet  108 . The compression of spring-loaded valve  119  allows fluid to flow through fluid line through the outlet  108  and into fluid line  104 . Filter pad  112 , prevents large salt particles from exiting the salt cartridge  101  while allowing the generated brine solution through. The filter pad  112  can be any type of filter known to those of skill in the art that will prevent most solid salt particles from passing through while allowing the brine solution to pass through. 
       FIG. 1G  shows a top of the salt cartridge  101 , including inlet  114 . The top of the salt cartridge  101  can include ridges  116  to help evenly distribute fluid entering through inlet  114 . The ridges  116  can extend radially from a desired point, such as inlet  114 , to induce flow to the desired point. In certain embodiments, the top of the salt cartridge  101  can have a slightly concave or convex surface to induce flow to the desired point. The ridges  116  can be uniform in length or have different lengths. 
     As illustrated in  FIG. 1H , the base  105  of salt cartridge  101  can be a solution diversion base that includes solution diversion ridges  117 . The solution diversion ridges  117  can be positioned above the outlet  108 . The solution diversion ridges  117  ensure that flow through the salts is even, causing the entire column of sodium chloride and sodium acetate to contact the water and dissolve. The diversion ridges  117  can be uniform in length or have different lengths. In certain embodiments, the base  105  can have a slightly concave or convex surface to induce flow to the desired point. 
       FIG. 1I  is an exploded cutaway view of the salt cartridge  101 . The salt cartridge  101  can include a frame  107  at a top of the salt cartridge  101 . The first filter pad  111  is placed between the inlet  114  and a top level of salt in the salt cartridge  101 . Second filter pad  112  is placed at the bottom of the salt cartridge  101  above outlet  108 . The base  105  of the salt cartridge  101  includes solution diversion ridges  117  to ensure even flow of fluid through the salt column. 
     The salt cartridge  101  can be constructed from any material known to those of ordinary skill capable of holding the salts  110 . In certain embodiments, the salt cartridge  101  can be constructed from a polymer such as polypropylene, polyethylene, or high-density polyethylene. Alternatively, metal, glass, or other materials can be used. 
     One of skill in the art will understand that the required size of the salt cartridge  101  depends on the amount of brine solution desired. As a non-limiting example, the salt cartridge  101  can be sized to hold between 1.5-2.0 kg of sodium acetate and sodium chloride with 200-300 mL left of water filling capacity. The volume of water added can be varied to generate a brine solution having a desired sodium concentration. In certain embodiments, about 5 L of water can be used to generate the brine solution. However, with larger brine outputs desired, the salt cartridge can be made larger as well. The volume of water added can be varied to generate a brine solution having a desired sodium concentration. In certain embodiments, about 5 L of water can be used to generate the brine solution. However, the amount of water used can be varied depending on the desired brine solution concentration and the amount of salt used. 
       FIG. 2  is a generalized diagram of a sorbent recharger system using the described salt cartridge  205 . As described, a salt cartridge  205  can contain sodium acetate and sodium chloride in any amounts. Water from water source  201  can be pumped into an inlet of the salt cartridge  205 . In certain embodiments, the water source can be fluidly connected to a sorbent recharger  202 . The water can be pumped from water source  201 , through line  209  into the sorbent recharger  202  and then into the salt cartridge  205  through fluid line  207 . Alternatively, a separate fluid line (not shown) can connect the water source  201  to the inlet of salt cartridge  205 . 
     The water pumped into salt cartridge  205  can dissolve the sodium acetate and sodium chloride and exit through an outlet of the salt cartridge  205  into brine container  204 . To ensure complete dissolution of the sodium acetate and sodium chloride and a homogeneous brine solution, the solution can be recirculated through a flow path as shown by arrows  211 . The brine solution can be pumped from the outlet of the salt cartridge  205  into brine container  204  through fluid line  206 , back into sorbent recharger  202  through fluid line  208 , and then back to the inlet of the salt cartridge  205  through fluid line  207 . The salt cartridge  205 , fluid line  206 , brine container  204 , fluid line  208 , sorbent recharger  202 , and fluid line  207  define a recirculation flow path. The solution can be pumped through the recirculation flow path until a homogeneous solution is formed, or for some preset period of time that is long enough to ensure formation of a homogenous solution. The preset period of time can be any time long enough to ensure complete dissolution and homogeneity. In certain embodiments, the preset period of time can be between 20 and 45 minutes. Additionally, or alternatively, one or more sensors, such as conductivity sensors, can be included to ensure that the generated brine solution has the proper concentrations of sodium chloride and sodium acetate. 
     The brine solution, once formed, can be used to recharge zirconium phosphate in a zirconium phosphate sorbent module. The brine solution can replace cations that were bound to the zirconium phosphate during dialysis treatment with sodium and hydrogen ions. The final ratio of sodium to hydrogen ions on the recharged zirconium phosphate is a function of the pH and sodium concentration of the brine solution. As such, the sodium/hydrogen ratio of the recharged zirconium phosphate can be controlled by controlling the pH and sodium concentration of the brine solution used in recharging. Acetic acid from acetic acid source  203  can be added to the recirculation flow path while the brine is being recirculated to adjust the pH of the brine solution. Acetic acid can be pumped from acetic acid source  203  through fluid line  210  into the sorbent recharger  202  for addition to the recirculating flow path. A control system (not shown) can control one or more pumps and one or more valves within the sorbent recharger  202  to generate a brine solution having a specified pH by adding a volume of acetic acid from the acetic acid source  203 . Using a known amount of sodium chloride and sodium acetate in salt cartridge  205  and adding a set amount of water from water source  201  can provide a known sodium concentration in the resulting brine solution. The amount of acetic acid added from acetic acid source  203  can be controlled by the control system to generate a brine solution having a desired pH. 
     To recharge the zirconium phosphate in a zirconium phosphate sorbent module, the control system can control one or more pumps (not shown) and/or valves (not shown) to pump the generated brine solution from brine container  204 , through fluid line  208 , into sorbent recharger  202  where the brine solution is passed through the zirconium phosphate sorbent module. 
     Table 1 shows a non-limiting example of a brine solution for recharging zirconium phosphate that can be made using the described salt cartridge system. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 ZP Recharge- Brine Solution Preparation 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Sodium  
                   
                   
               
               
                   
                 Sodium 
                 Acetate, 
                 Acetic 
                   
               
               
                 Description 
                 chloride 
                 trihydrate 
                 Acid 
                 Water 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Conc M 
                 4.70 
                 0.40 
                 0.40 
                 N/A 
               
               
                 Mol wt 
                 58.50 
                 136.00 
                 60.05 
                 N/A 
               
            
           
           
               
               
            
               
                 Mix density (kg/l) @25° C. 
                 1.19 
               
            
           
           
               
               
               
               
               
            
               
                 Individual density (kg/l) @25° C. 
                 2.16 
                 1.45 
                 1.05 
                 1.00 
               
            
           
           
               
               
            
               
                 Total Volume (L) 
                 6.20 
               
               
                 Total weight (kg) 
                 7.38 
               
            
           
           
               
               
               
               
               
            
               
                 Individual weight (kg) 
                 1.70 
                 0.34 
                 0.15 
                 5.19 
               
               
                 Individual volume (L) 
                 N/A 
                 N/A 
                 0.14 
                 5.20 
               
               
                   
               
            
           
         
       
     
     The brine solution described in Table 1 uses 5.20 L of water, which is added to a salt cartridge containing 1.70 kg of sodium chloride and 0.34 kg of sodium acetate trihydrate. 0.14 L of acetic acid can be added during generation of the brine solution, as described. The resulting brine solution has a sodium chloride concentration of 4.70 M, a sodium acetate concentration of 0.40 M, and an acetic acid concentration of 0.40 M. However, as described, brine solutions having a higher or lower pH can be generated by adding more or less acetic acid or sodium acetate. A person of ordinary skill in the art will understand that the ratio of sodium chloride to sodium acetate used can vary depending on the needs of the user. The sodium concentration of the brine solution can be controlled by using more or less sodium chloride and sodium acetate or by varying the volume of water added to the salt cartridge in forming the brine solution as would be understood by one of ordinary skill in the art. One or more conductivity sensors can be used to ensure complete dissolution and homogeneity. The conductivity of the generated brine solution will vary based on the concentrations of each solute. However, the conductivity of the solution shown in Table 1 should be within 180-240 mS/cm at 25° C. 
       FIGS. 3A-C  show a sorbent recharger  301  using a salt cartridge  302  as described.  FIG. 3A  is a rear view of the sorbent recharger  301 ,  FIG. 3B  is a perspective view of the sorbent recharger  301 , and  FIG. 3C  is a front view of the sorbent recharger  301 . As illustrated in  FIG. 3A , the salt cartridge  302  can be fluidly connected to the sorbent recharger  301 . Water from a water source (not shown) can be pumped through an inlet  305  of the salt cartridge  302  containing sodium chloride and sodium acetate through fluid line  304 . The brine solution formed can exit the salt cartridge  302  through an outlet (not shown) and flow through fluid line  306  into brine container  303 . Fluid can be recirculated in a flow path from the outlet of the salt cartridge  302 , through fluid line  306  and into the brine container  303 , out of brine container  303  through fluid line  307  back to sorbent recharger  301  through inlet port  309 , and then through outlet port  308  back into the salt cartridge  302  through fluid line  304 . The brine solution can be recirculated in the flow path until a homogeneous solution is formed, or for a preset period of time. While the brine solution is recirculating, acetic acid from acetic acid source  310  can be pumped through fluid line  311  into sorbent recharger  301  through inlet port  312 , where the acetic acid is added to the recirculating brine solution. After a homogeneous brine solution is formed, the brine solution can be collected in brine container  303 . 
     As described, in certain embodiments, the sorbent recharger can also be used to recharge zirconium oxide. To recharge zirconium oxide, a basic solution can be pumped through the zirconium oxide. Sodium hydroxide from sodium hydroxide source  313  can be pumped through fluid line  314  into sorbent recharger  301  through inlet port  317  and through the zirconium oxide sorbent module  332 . Bleach from bleach source  315  can be pumped through fluid line  316  into sorbent recharger  301  through inlet port  318  and through the zirconium oxide sorbent module  332  to disinfect the zirconium oxide sorbent module  332 . 
     As illustrated in  FIG. 3A , the sorbent recharger  301  can include fluid inlet port  309  for receiving a brine solution, inlet port  312  for receiving acetic acid, inlet port  317  for receiving sodium hydroxide, and inlet port  318  for receiving bleach. An additional inlet port (not shown) can be included for receiving water from a water source (not shown). The sorbent recharger  301  can also include outlet port  308  for pumping fluid to the salt cartridge  302 . Additional outlet ports, including outlet port  319 , outlet port  320 , and outlet port  321  can be included for connection to a drain, waste container, or collection container. 
     The salt cartridge  302  can connect to fluid lines  306  and  308  through any means known in the art. In  FIG. 3A , the connections are shown as a quick connector  324  to connect to the sorbent recharger  301  and quick connector  323  to connect to brine container  303 . A similar quick connector  322  can be used to connect brine container  303  to the sorbent recharger  301  and quick connector  325  can connect bleach source  315  to fluid line  316 . One of skill in the art will understand that connectors can also be used for connecting any of the fluid sources to the fluid lines. Quick connectors allow fluid lines to be connected by snapping connectors on each line together. However, other connectors that can form fluid passages can be used. As described, the salt cartridge  302  can be mounted on the system using base plate  328 , or by any other method. In certain embodiments, identification plate  327  can be included on the salt cartridge  302  to identify a specific salt cartridge or to display any other information. 
     As illustrated in  FIG. 3B , The sorbent recharger  301  can include one or more receiving compartments for receiving reusable sorbent modules. The sorbent recharger  301  includes a first receiving compartment  329  for receiving a zirconium phosphate sorbent module  330 . To recharge the zirconium phosphate in the zirconium phosphate sorbent module  330 , the generated brine solution in brine container  303  is pumped through the zirconium phosphate sorbent module  330 , replacing potassium, calcium, magnesium, and ammonium ions bound to the zirconium phosphate with sodium and hydrogen ions. 
     In certain embodiments, additional receiving compartments can be included. For example, the sorbent recharger  301  shown in  FIG. 3B  includes a second receiving compartment  331  for receiving a zirconium oxide sorbent module  332 . Additional chemicals can be included for recharging the zirconium oxide in zirconium oxide sorbent module  332 . To recharge zirconium oxide, sodium hydroxide from sodium hydroxide source  313  can be pumped through fluid line  314  into sorbent recharger  301  and through the zirconium oxide sorbent module  332 . Bleach from bleach source  315  can be pumped through fluid line  316  into sorbent recharger  301  and through the zirconium oxide sorbent module  332  to disinfect the zirconium oxide sorbent module  332 . Alternatively, a sorbent recharger can include two receiving compartments to recharge two different zirconium phosphate sorbent modules. In any embodiment, the sorbent recharger  301  can include any number of receiving compartments for recharging any number of zirconium phosphate and/or zirconium oxide sorbent modules. 
     The sorbent recharger can include a graphical user interface  333  shown in  FIG. 3B  that can be used to control recharging of the sorbent materials. Through graphical user interface  333 , the user can initiate, stop, and otherwise control the preparation of the brine solution and the recharging process. Further, any errors, alerts, or other messages can be provided to the user through graphical user interface  333 . In  FIG. 3B , the sorbent recharger  301  is small enough to fit on table  326 . However, larger sorbent rechargers can be used for recharging additional materials. 
       FIG. 3C  shows a front view of the sorbent recharger  301 . The sorbent recharger  301  includes a first receiving compartment  329  for receiving a zirconium phosphate sorbent module  330  and a second receiving compartment  331  for receiving a zirconium oxide sorbent module  332 . Brine container  303  is connected to an outlet of the salt cartridge  302  through fluid line  306  having quick connector  323 . The brine container is also connected to sorbent recharger  301  through fluid line  307  having quick connector  322 . To generate a brine solution, fluid is recirculated between the salt cartridge  302 , brine container  303  and sorbent recharger  301  until a homogeneous solution is formed. Acetic acid source  310 , sodium hydroxide source  313  and bleach source  315  can each be connected to sorbent recharger  301  through fluid lines  311 ,  314 , and  316 , respectively. As described, the sorbent recharger  301  can include graphical user interface  333  for controlling the recharging process. 
       FIG. 4  shows a flow diagram for a recharger system using a salt cartridge. salt cartridge  402  can include an inlet  404 . Solid sodium chloride and solid sodium acetate can be placed in a lower portion of the interior of salt cartridge  402 . Water from water source  412  can be pumped through water line  413  and port  414  into sorbent recharger  401 . As illustrated in  FIG. 4 , in certain embodiments the sorbent recharger  401  can use two pumps  432  and  433 . Using two pumps allows fluid from multiple sources to be mixed in-line rather than using mixing chambers. However, one of skill in the art will understand that a single pump system can also be used. From inlet port  414 , the water is pumped through fluid line  415  and T-junction  416  into fluid lines  417  and  418 . The water is pumped through T-junction  419  and fluid line  420  to port  421 . From port  421 , the water can flow through fluid line  422  and into an empty upper portion of salt cartridge  402  through inlet  404 . The water can soak filter pad  406  and the salt to generate the brine solution. 
     The water can dissolve at least a portion of the sodium acetate and sodium chloride in salt cartridge  402  and exit the salt cartridge  402  through outlet  405  into fluid line  409  and brine container  403 . Filter pad  407  can be included between the sodium acetate and sodium chloride and outlet  405  of salt cartridge  402  to prevent solid material from entering fluid line  409 . The brine solution can be recirculated through the flow path from brine container  403 , through fluid line  410  and port  411  of the sorbent recharger  401  into fluid line  415 , where the brine solution follows the same pathway as the water back into salt cartridge  402 . During recirculation of the brine solution, acetic acid from acetic acid source  423  can be pumped through fluid line  424  and port  425  for addition to the brine solution recirculating in the flow path. Once the sodium acetate and sodium chloride are fully dissolved, the acetic acid is added, and a homogeneous brine solution is formed, the brine solution can be collected in brine container  403 . 
     To recharge zirconium phosphate, a zirconium phosphate sorbent module can be placed in a receiving compartment (not shown) of the sorbent recharger  401 . An inlet of the zirconium phosphate sorbent module can be connected to fluid line  415 , and an outlet of the zirconium phosphate sorbent module can be fluidly connected to a drain or collection container (not shown). The control system can operate pump  432  and/or pump  433  to pump brine solution from brine container  403  through the zirconium phosphate sorbent module. 
     As described, in certain embodiments, the sorbent recharger  401  can include a receiving compartment for receiving a zirconium oxide sorbent module (not shown). To recharge zirconium oxide in a zirconium oxide sorbent module, bleach can be pumped from bleach container  429 , through fluid line  430  to port  431 . A separate flow path can direct the bleach solution through the zirconium oxide sorbent module to a drain or collection container. Sodium hydroxide from sodium hydroxide container  426  can be pumped through fluid line  427  and port  428 , and then through the zirconium oxide sorbent module. Additional outlet ports can be included on the sorbent recharger  401 , including outlet port  434 , outlet port  435 , and outlet port  436  for connection to waste collection containers, drains, or other components. 
     One of skill in the art will understand that  FIG. 4  is a simplified diagram of a non-limiting embodiment of a sorbent recharger  401 . Additional components, such as valves, sensors, additional pumps, and additional fluid lines can be included, as necessary. The control system can be programmed to control the pumps and valves to direct fluid through the proper flow paths for generating the brine solution and recharging the sorbent materials. As described, the salt cartridge  402  can be mounted on a base plate  408  to prevent the salt cartridge  402  from moving during use. 
     The described systems and methods allow for a “just in time” brine preparation. Rather than storing large quantities of premade brine solution, the salt cartridge system allows for preparation of the brine solution immediately before use. The time required to generate the brine solution using a salt cartridge can vary, but generally the generation of the brine solution will be under 1 hour, or about 45 minutes. 
     One skilled in the art will understand that various combinations and/or modifications and variations can be made in the described systems and methods depending upon the specific needs for operation. Various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. Moreover, features illustrated or described as being part of an aspect of the disclosure may be used in the aspect of the disclosure, either alone or in combination, or follow a preferred arrangement of one or more of the described elements. Depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., certain described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as performed by a single module or unit for purposes of clarity, the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.