Multifunctional Zwitterionic Hydrogels as a Platform for the Rapid and Simultaneous Elimination of Organic and Inorganic Micropollutants from Water

The removal of micropollutants from water is made difficult by their chemical diversity, low concentrations, and slow uptake by industrial adsorbents. Traditional adsorbents, like activated carbon and ion-exchange resins, are effective in eliminating only specific classes of micropollutants, necessitating the use of multiple unit operations that sequentially treat water. At the same time, slow kinetics require the unit operations to have long residence times and be much larger to effectively eliminate micropollutants. Here we present a new multifunctional zwitterionic porous hydrogel platform for the single-step bulk absorption of both organic and inorganic micropollutants from water. Shifting from traditional surface adsorbents to hydrogels greatly increases the effective functional area, while allowing us to retain the same process-level equipment that has been well studied in the context of conventional adsorbents. A facile synthesis allows easy functionalization of the hydrogels for eliminating multiple micropollutant classes, while also allowing a measure of selectivity. The hydrogels can be synthesized in several form factors for specific applications, including microparticles for use in packed beds, or tablets for treating water in a glass or canteen. Transport of micropollutants within the hydrogels is sped by ion-conducting zwitterionic backbones, while encapsulated micelles speed the transport of uncharged organics. The zwitterionic hydrogels are shown to remove six chemically diverse micropollutants (including BPA, xenoestrogens, and other organics, and lead and other metals) at least 10 times more rapidly than a commercial activated carbon/ion exchange resin mixture, and 100 times faster than other multifunctional adsorbents reported in literature. Zwitterionic hydrogels treat complex micropollutant mixtures, including in the presence of background hardness. Lower compressibility, extremely rapid mass transport, and high stability make our materials highly scalable for real world applications. We demonstrate the use of a prototype packed bed filter with a practical residence time and containing zwitterionic hydrogel microparticles to clean highly contaminated water to below regulatory limits for a period of two weeks.