Perchlorate removal from concentrated salt solutions using amphoteric ion-exchange resins
A process for reducing the concentration of perchlorate in an aqueous concentrated multi-component salt solution comprising treating the salt solution with an amphoteric ion-exchange resin to provide an adsorbed perchlorate and multi anion-containing resin and a perchlorate depleted solution; and removing the perchlorate depleted solution. The multi-anion are selected from chloride, chlorate, perchlorate, sulphate, and dichromate, present in electrolytic processes for the production of sodium chlorate.
1. A process for reducing the concentration of perchlorate in an aqueous concentrated multi-component sodium chlorate solution comprising mainly sodium chlorate, the process comprising:
treating said sodium chlorate solution with an amphoteric resin to provide an adsorbed perchlorate and multi anion-containing resin and a perchlorate-depleted solution; and
removing said perchlorate depleted solution.
2. The process according to claim 1 further comprising treating said adsorbed perchlorate and multi anion-containing resin with a first quantity of elution water to provide a lean first eluent and a first eluted resin; and collecting said lean first eluent.
3. The process according to claim 2 further comprising treating said first eluted resin with a second quantity of elution water to provide a rich second eluent and a second eluted resin; and collecting said rich second eluent.
4. The process according to claim 3 , wherein said treatment of said adsorbed perchlorate resin with said first quantity of elution water and said first eluted resin with said second quantity of elution water constitutes a continuous process.
5. The process according to claim 3 wherein said amphoteric ion-exchange resin has a resin first volume and combined said first quantity and second quantity of said elution water has a total volume of about 1 to 10 times said resin first volume.
6. The process according to claim 5 , wherein said total volume of elution water is about 2 to 5 times said resin first volume.
7. The process according to claim 3 further comprising treating said rich second eluent to provide a recovered perchlorate.
8. The process according to claim 3 further comprising treating said rich second eluent to a perchlorate destruction process to remove said perchlorate and produce a perchlorate-depleted solution.
9. The process according to claim 8 , wherein said destruction process is selected from the group consisting of electrolytic reduction, thermal decomposition and an electro-catalytic process.
10. The process according to claim 8 further comprising recycling said perchlorate-depleted solution to a process selected from the group consisting of an electrolyte sodium chlorate process, an integrated chlorine dioxide process and a sodium chlorite production process.
11. The process according to claim 2 , wherein said adsorbed perchlorate and multi-anions are eluted with said elution waters from said resin in the order of their inverse affinity to said amphoteric ion-exchange resin as to separate said perchlorate and anions wherein the less affixed anions are first eluted to produce said lean first eluent while the more strongly affixed perchlorate is eluted subsequently with said elution water to produce said rich second eluent.
12. The process according to claim 2 , wherein said elution water is demineralized water.
13. The process according to claim 2 further comprising recycling said lean first eluent to a process selected from the group consisting of an electrolyte sodium chlorate process, an integrated chlorine dioxide process and a sodium chlorite production process.
14. The process according to claim 1 , wherein said multi-component sodium chlorate solution additionally comprises anions selected from the group consisting of chloride, sulphate and dichromate.
15. The process according to claim 1 , wherein said sodium chlorate solution comprises 300 to 650 gpl NaClO 3 .
16. The process according to claim 15 , wherein said sodium chlorate solution comprises:
480 to 620 gpl NaClO 3 ;
80 to 110 gpl NaCl;
4 to 6 gpl Na 2 Cr 2 O 7 ;
5 to 20 gpl Na 2 SO 4 ; and
20 to 50 gpl NaClO 4 .
17. The process according to claim 15 , wherein said sodium chlorate solution additionally comprises:
80 to 130 gpl NaCl;
3 to 10 gpl Na 2 Cr 2 O 7 ;
0 to 25 gpl Na 2 SO 4 ; and
0.5 to 100 gpl NaClO 4 .
18. The process according to claim 1 , wherein said sodium chlorate solution is a cell liquor produced from the electrolysis of sodium chloride solution in a sodium chlorate electrolyzer.
19. The process according to claim 1 , wherein said sodium chlorate solution is mother liquor exiting a sodium chlorate crystallizer in a sodium chlorate electrolytic process.
20. The process according to claim 1 further comprising recycling said perchlorate-depleted solution to a process selected from the group consisting of an electrolyte sodium chlorate process, an integrated chlorine dioxide process and a sodium chlorite production process.
21. The process according to claim 1 further comprising treating said adsorbed perchlorate and multi-anion-containing resin with elution water to provide a perchlorate-containing eluent.
22. The process according to claim 21 further comprising treating said perchlorate-containing eluent to provide a recovered perchlorate.
23. The process according to claim 21 further comprising treating said perchlorate-containing eluent to a perchlorate destruction process to remove said perchlorate and produce a perchlorate-depleted solution.
24. The process according to claim 23 , wherein said destruction process is selected from the group consisting of electrolytic reduction, thermal decomposition and an electro-catalytic process.
25. The process according to claim 23 further comprising recycling said perchlorate-depleted solution to a process selected from the group consisting of an electrolyte sodium chlorate process, an integrated chlorine dioxide process and a sodium chlorite production process.