Trace Organic Contaminant Removal from Municipal Wastewater by Styrenic β-Cyclodextrin Polymers

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment Technologies

Background:

• Trace organic contaminants (TrOCs), including perfluoroalkyl and polyfluoroalkyl substances (PFAS), pose significant challenges in wastewater treatment due to their toxicity and persistence.
• Conventional adsorbents like granular activated carbon (GAC) show limitations in TrOC removal efficiency and are prone to fouling in complex wastewater matrices.
• There is a critical need for selective and robust adsorbents capable of efficient TrOC removal for safe water reuse and environmental protection.

Purpose of the Study:

• To develop and characterize a novel, simplified, and scalable porous polymer adsorbent based on cross-linked β-cyclodextrin (β-CD) with cationic ammonium groups.
• To evaluate the adsorption performance, selectivity, kinetics, and regenerability of the synthesized β-CD polymer for various TrOCs in wastewater.
• To compare the efficacy of the novel β-CD polymer with established adsorbents such as GAC and ion exchange (IX) resin.

Main Methods:

• Synthesis of a porous polymer via cross-linking of β-cyclodextrin with styrene and incorporation of cationic ammonium groups.
• Batch adsorption experiments to assess the removal of 13 different TrOCs from synthetic wastewater, evaluating selectivity and adsorption inhibition.
• Kinetic studies and adsorption isotherm modeling to determine adsorption rates and affinities, particularly for PFAS.
• Regeneration tests using solvent washing to assess adsorbent reusability.
• Rapid small-scale column tests to evaluate breakthrough behavior in comparison to GAC and IX resin.

Main Results:

• The synthesized β-CD polymer demonstrated complete removal for six out of 13 tested TrOCs, showing higher selectivity than GAC.
• The polymer exhibited significantly faster adsorption kinetics and higher adsorption affinity for PFAS compared to GAC.
• Less adsorption inhibition was observed for the β-CD polymer in wastewater compared to GAC, indicating better performance in complex matrices.
• Column tests revealed later breakthrough times for the β-CD polymer relative to GAC and IX resin, suggesting improved capacity and efficiency.
• The adsorbent was successfully regenerated through solvent washing, indicating its potential for multiple use cycles.

Conclusions:

• The developed porous β-CD polymer is a highly promising adsorbent for the selective removal of TrOCs, including challenging PFAS, from complex water matrices.
• Its superior adsorption kinetics, higher affinity for PFAS, and robustness in wastewater offer significant advantages over conventional adsorbents like GAC and IX resin.
• The simplified synthesis and regenerability of the β-CD polymer suggest its potential for scalable and cost-effective application in advanced wastewater treatment processes.