Methods and Systems of Nitrate Removal in Aqueous Systems for Improved PFAS Destruction
Methods, systems and devices for PFAS destruction including removing nitrate from water containing PFAS, combining the water with a sensitizer and a sufficient quantity of base to create a treatment solution having a pH of about 10 or more, and irradiating the treatment solution with UV light in a photoreactor to destroy a portion of the PFAS. The nitrate may be removed electrolytically such as by electrolytically reducing nitrate to nitrogen gas and/or ammonia. The nitrate may be removed by filtration through a selective membrane, such as by reverse osmosis, forward osmosis, nanofiltration, and/or ultrafiltration. The system may include electrolytic cell system including a first cell with a cathode contacting the water containing PFAS in the first cell, a second cell including an anode in an electrolytic solution, a power source, and a salt brine and/or membrane separating the first and second cells.
1 . A method of PFAS destruction comprising:
removing nitrate from water containing PFAS;
combining water containing PFAS with a sensitizer and a sufficient quantity of base to create a treatment solution having a pH of about 10 or more; and
irradiating the treatment solution with UV light in a photoreactor to destroy a portion of the PFAS.
2 . The method of claim 1 wherein removing nitrate from the water containing PFAS comprises electrolytically removing nitrate from the water containing PFAS.
3 . The method of claim 2 wherein electrolytically removing nitrate comprises electrolytically reducing nitrate to nitrogen gas and/or ammonia.
4 . The method of claim 2 wherein electrolytically removing nitrate from water containing PFAS comprises contacting water containing PFAS with an electrode and applying current to the electrode.
5 . The method of claim 4 wherein the electrode comprises an iron, copper or iron:copper electrode.
6 . The method of claim 4 wherein the electrode comprises a cathode of an electrolytic cell system, the electrolytic cell system further comprising an anode in an aqueous electrolyte solution.
7 . The method of claim 6 further comprising forming oxygen gas at the anode while reducing nitrate at the cathode.
8 . The method of claim 12 wherein removing nitrate from the water containing PFAS comprises filtration through a selective membrane.
9 . The method of claim 8 wherein filtration through a selective membrane comprises reverse osmosis, forward osmosis, nanofiltration (NF), and/or ultrafiltration (UF).
10 . The method of claim 1 wherein removing nitrate from water containing PFAS comprises a pretreatment step prior to irradiating the treatment solution.
11 . The method of claim 1 wherein removing nitrate from water containing PFAS comprises a step that occurs within the photoreactor.
12 . A method of PFAS destruction comprising:
contacting water containing PFAS with a cathode;
applying current to the cathode to electrolytically reduce nitrate in the water containing PFAS;
combining the water containing PFAS with a sulfite and a halide salt, and a sufficient quantity of base to create a treatment solution having a pH of about 10 or more; and
irradiating the treatment solution with UV light in a photoreactor to destroy a portion of the PFAS.
13 . The method of claim 12 wherein the halide salt comprises iodide and the UV light comprises light with an emission peak at approximately 222 nm.
14 . The method of claim 13 further comprising oxidatively pretreating the water containing PFAS prior to irradiating the PFAS.
15 . The method of claim 14 wherein oxidatively pretreating the water containing PFAS comprises mixing the water containing PFAS with a persulfate and an acid or base and then subjecting the water to increased temperature and pressure.
16 . A system for the destruction of PFAS in water, the system comprising:
a nitrate removal system configured to remove nitrate from water containing PFAS and nitrate, the nitrate removal system comprising a selective membrane and/or an electrolytic cell system; and
a photoreactor comprising:
a reactor vessel configured to contain an aqueous solution; and
a source of ultraviolet light source positioned to direct light onto the contents of the reactor vessel.
17 . The system of claim 16 wherein the nitrate removal system is upstream of the photoreactor.
18 . The system of claim 16 wherein the nitrate removal system is an electrolytic cell system comprising:
a first cell comprising a cathode configured to contact the water containing PFAS in the first cell;
a second cell comprising an anode in an electrolytic solution;
a power source; and
a salt brine and/or membrane separating the first and second cells.
19 . The system of claim 19 wherein the cathode is located within the photoreactor and the photoreactor vessel forms a container of the first cell.
20 . The system of claim 18 wherein the cathode comprises iron, copper and/or iron:copper.