Perchlorate-selective and high capacity ion-exchange resins from hyperbranched polyethylenimine

Abstract

Perchlorate (ClO4-) is a persistent contaminant found in surface and groundwater around the United States. ClO4- can have adverse health effects due to its ability to disrupt the thy-roid’s ability to produce hormones required for proper growth and development. Although the United States Environmental Agency (USEPA) has yet to formally regulate ClO4-, vari-ous states have set public health goals (PHG) for drinking water. For example, Massachu-setts and California have established PHG based on a maximum concentration of ClO4- in drinking water of 2 ppb and 6 ppb, respectively.1, 2 ClO4--selective ion exchange resins based on styrene divinylbenzene beads are currently the most commonly utilized media for removing low concentrations of ClO4- (10-50 ppb) from contaminated drinking water sources.3 However, owing to the low exchange capacity of these commercial resins, the overall treatment cost becomes prohibitive as the concentration of ClO4- in the influent wa-ter increases. In this text, we show that hyperbranched polyethylenimine (PEI) can be used as building blocks to prepare a new generation of ClO4--selective anion-exchange resins with high capacity. PEI based ion-exchange matrix prepared at AquaNano Technologies (Monrovia, California) were alkylated to afford resins with fixed ionogenic sites which were appropriately tuned to impart ClO4--selectivity. PEI resins that were functionalized with hexyl and ethyl alkyl chains (QPEI-8) can selectively extract trace amounts of ClO4- from a makeup groundwater to below detection limits (2 ppb) in the presence of competing ions. The performance of QPEI-8 was evaluated and compared with commercially available ClO4--selective A-530E resin. Batch and column studies of ClO4- removal from a simulated groundwater indicate that our new resins outperform several commercial resins.