Removal of PFAS and pharmaceuticals from municipal wastewater using a novel β-cyclodextrin adsorbent over distinct contact times.

Conventional adsorbents applied in wastewater treatment are ineffective at removing trace organic contaminants (TrOCs), including per and poly-fluoroalkyl substances (PFAS) and pharmaceuticals. Cross-linked β-cyclodextrin (β-CD) polymer adsorbents have demonstrated efficient removal of TrOCs and exhibit rapid kinetics and high adsorption capacity in wastewater. We evaluate the removal of a mixture of contaminants from wastewater by a styrene functionalized β-CD adsorbent (StyDex) through rapid small-scale column tests (RSSCTs). We found the kinetics observed in batch adsorption tests are maintained in RSSCTs. However, batch sorption kinetic constants did not match column breakthrough kinetics, due to an inability to describe complex flow-through behaviors. We correlated both batch kinetic constants and treatable bed volumes with hydrophobicity of target compounds, where PFOA and PFHxS had the highest affinity for StyDex in batch tests and the latest breakthroughs in RSSCTs. Breakthrough curves of five of the seven TrOCs were not affected by change in contact time. Conversely, decreasing the contact time led to earlier breakthrough of contaminants with the highest sorption affinity to StyDex: longer chained and sulfonated PFAS compounds. These effects were isolated in two-component competitive sorption experiments between PFOA and PFBA, and we observed the same preferential sorption of hydrophobic compounds identified in the multi-component mixture. Additionally, competitive adsorption-desorption increased with increasing contact times. We discuss how these findings are crucial for scale-up and large-scale testing of novel sorbents.