A method comprising the steps of: recharging a sorbent material within a sorbent module by pumping one or more recharge solutions through the sorbent module; wherein a volume and/or a concentration of the one or more recharge solutions is set based on one or more patient parameters and/or one or more dialysis session parameters for a patient and/or dialysis session using the sorbent module; wherein (a) the sorbent module contains zirconium oxide, and wherein the one or more patient parameters and/or one or more dialysis session parameters include: a total phosphate pumped through the sorbent module during a prior dialysis session; or an estimated duration to a next dialysis session for the patient; or (b) the sorbent module contains zirconium phosphate, and wherein the volume of the one or more recharge solutions is set using an equation Vr = v * Q * t * (CNH4 + CK + CCa + CMg + (a * CHCO3 + b)); wherein Vr is the volume of the one or more recharge solutions, Q is a time averaged volume flow rate into the sorbent module, t is a session time, CNH4, CK, CCa, CMg, and CHCO3 are average concentrations of ammonium ions, potassium ions, calcium ions, magnesium ions and bicarbonate ions entering the sorbent module, a and b are variables related to a pH of the zirconium phosphate, and v is a variable specific to a recharge process being used. recharging a sorbent material within a sorbent module by pumping one or more recharge solutions through the sorbent module; wherein a volume and/or a concentration of the one or more recharge solutions is set based on one or more patient parameters and/or one or more dialysis session parameters for a patient and/or dialysis session using the sorbent module; wherein (a) the sorbent module contains zirconium oxide, and wherein the one or more patient parameters and/or one or more dialysis session parameters include: a total phosphate pumped through the sorbent module during a prior dialysis session; or an estimated duration to a next dialysis session for the patient; or (b) the sorbent module contains zirconium phosphate, and wherein the volume of the one or more recharge solutions is set using an equation Vr = v * Q * t * (CNH4 + CK + CCa + CMg + (a * CHCO3 + b)); wherein Vr is the volume of the one or more recharge solutions, Q is a time averaged volume flow rate into the sorbent module, t is a session time, CNH4, CK, CCa, CMg, and CHCO3 are average concentrations of ammonium ions, potassium ions, calcium ions, magnesium ions and bicarbonate ions entering the sorbent module, a and b are variables related to a pH of the zirconium phosphate, and v is a variable specific to a recharge process being used. (a) the sorbent module contains zirconium oxide, and wherein the one or more patient parameters and/or one or more dialysis session parameters include: a total phosphate pumped through the sorbent module during a prior dialysis session; or an estimated duration to a next dialysis session for the patient; or (b) the sorbent module contains zirconium phosphate, and wherein the volume of the one or more recharge solutions is set using an equation Vr = v * Q * t * (CNH4 + CK + CCa + CMg + (a * CHCO3 + b)); wherein Vr is the volume of the one or more recharge solutions, Q is a time averaged volume flow rate into the sorbent module, t is a session time, CNH4, CK, CCa, CMg, and CHCO3 are average concentrations of ammonium ions, potassium ions, calcium ions, magnesium ions and bicarbonate ions entering the sorbent module, a and b are variables related to a pH of the zirconium phosphate, and v is a variable specific to a recharge process being used. <EOS>