Perchlorate Treatment Using Highly Selective, Regenerable Anion Exchange Resins

 

Regeneration of Spent Resin Columns

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Regenerated by FeCl3-HCl solution (US Patent 6,448,299).

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Highly efficient – only 2–3 bed volumes of regenerant solution needed, and nearly 100% ClO4- recovered.

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ClO4- highly concentrated in FeCl3 regenerant solution.

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Applicable to any Type-I strong base anion-exchange resins.

Selective ion exchange is one of the preferred treatment technologies for removing low to trace levels of perchlorate (ClO4-) from contaminated water because of its high efficiency and minimal impact on water quality through the addition or removal of chemicals and nutrients.  However, the exceptionally high affinity of ClO4- for Type I strong-base anion-exchange resins makes regeneration with conventional NaCl brine extremely difficult and costly for practical applications.  The Oak Ridge National Laboratory recently developed a novel methodology to regenerate this type of resins loaded with ClO4-.  Tetrachloroferrate (FeCl4-) anions, formed in a solution of ferric chloride and hydrochloric acid (i.e., FeCl3 and HCl), were found to effectively displace ClO4- anions that were sorbed on the resin.  A mass-balance analysis indicated that a nearly 100% recovery of ion-exchange sites was achieved by washing with as little as ~2 - 3 bed volumes of the regenerant solution in a column. There was no significant deterioration of the resin’s performance with respect to ClO4- removal after repeated loading and regeneration cycles.  The new methodology offers a cost-effective means to regenerate ClO4--loaded resins with improved regeneration efficiency, recovery, and waste minimization in comparison with conventional brine regeneration techniques. Additionally, a new methodology was also developed to completely destroy perchlorate in the FeCl3-HCl regenerant solution; the regenerant can thus be recycled, and practically no secondary wastes are produced.