Anion exchange processes are often designed to target a specific oxyanion (e.g., arsenic, chromium, etc.). This study reports the removal and regeneration efficiency of non-target anions that co-occur in water sources using pilot-scale testing at groundwater utilities for two target contaminants: chromium and arsenic. For chromium testing, two test locations (California and Oklahoma) and three resins (Purolite A600E, Purolite PGW6002E, and Lanxess TP107) are compared to show that loading and recovery of arsenic, vanadium, and uranium are different from the target anion. Uranium and vanadium have poor regeneration efficiencies using a conventional sodium chloride approach. Applying an alternative approach (e.g., segmented regeneration) had a large impact on uranium and vanadium recovery. Recovery was sensitive to the presence of co-eluting bicarbonate and/or sulfate. Uranium accumulation can exceed nuclear regulation thresholds after 2-3 loading-regeneration cycles, and regeneration strategies may need to prioritize uranium recovery, even when it is a non-target anion. Vanadium loading on regenerated resins shows stepwise breakthrough compared to new resins, suggesting a change in the underlying isotherm. For chromium loading (&gt;30,000 bed volumes), arsenic appears to load 50% more mass past initial arsenic breakthrough. The additional arsenic recovered during regeneration equates to only 1.5% of the raw water arsenic exchanging over the last 40,000 BV of chromium loading. For arsenic testing (Purolite PFA300), chromium, vanadium, and uranium regeneration efficiency were low, and the impact of different regeneration approaches will be presented. Using the observations from pilot-scale testing, hypothesized chemical mechanisms (e.g., polynuclear complex formation) for increased arsenic loading and poor uranium and vanadium regeneration efficiency are presented as opportunities for future investigations.

Behavior of non-target anions in pilot-scale strong base anion exchange processes

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.