(614f) Perchlorate Destruction from Ion-Exchange Regenerants By Catalytic Reduction Process Increases Brine Recovery

Perchlorate salts are generated as a byproduct from rocket fuels and other explosives. Ingestion of perchlorate inhibits normal function of the thyroid gland and contributes to hormone imbalance. Recently, the USEPA determined that perchlorate must be regulated as a water contaminant under the Safe Drinking Water Act (SDWA). One method of removing perchlorate from drinking water and potable water sources is through selective ion-exchange resin. Because perchlorate ion binds very tightly to the strong base anion exchange resin, a solution of having extremely high salt concentration, typically between 7 â?? 12%, is required for regeneration of the resin. Furthermore, disposal of high concentration of perchlorate containing regenerant is problematic. Accordingly, there is a need for an improved method of removing perchlorate from water, including brine recovery.

Using a nanofiltration (NF) process, perchlorate is separated from the brine. More than 95% perchlorate was separated and retained in the reject. Permeate primarily containing brine was recycled back to the Ion exchange process to be used in the next stage of regeneration. Low volume of the NF reject containing high concentration of perchlorate ions is mixed with a reducing agent in a reactor where the perchlorate ions and the reducing agents undergo an oxidation-reduction (Redox) reaction. During the Redox reaction, perchlorate ions are reduced to chloride ions and the reducing agent is oxidized. The oxidized reducing agent is separated from the water which is regenerated by means of a second reducing agent, and reused in the Redox process. Redox reaction kinetic was significantly improved in presence of catalyst. Various reducing agents including Titanium (III), Manganese (II), and Iron (II) at different temperatures were investigated. The impacts of pH on the reduction kinetic were examined. All reactions were conducted with and without the catalyst. The efficiency of TiO₂ and MnO₂as the catalyst was compared.

Using an ion Chromatography (IC), perchlorate was measured. Results reveal that within the first two hours of reaction, more than 98% perchlorate was converted to chloride ion in presence of a catalyst. Increasing temperature increased prechlorate destruction efficiency. The process, and the impacts of various process parameters on the perchlorate destruction efficiency will be presented and discussed.