Investigation of the Adsorption Processes of Fluorocarbon and Hydrocarbon Anions at the Solid–Solution Interface of Macromolecular Imprinted Polymer Materials

Abstract

This study details the isotherm adsorption properties of cross-linked polymers containing β-cyclodextrin (β-CD), hereafter referred to as macromolecular imprinted materials (MIMs). The isotherm sorption parameters of the MIMs are reported with perfluorooctanoic acid (PFOA), octanoic acid (OA), and perfluorooctanesulfonate (PFOS) anions. The Sips and BET models describe variable solid-solution interfacial interactions for the MIMs with perfluorocarbon (PFC) and hydrocarbon (HC) anions, respectively. Typical monolayer adsorption occurs for the MIMs/OA system via the hydrocarbon alkyl tail of OA. Atypical adsorption is observed for PFOA and is driven via interactions between the MIMs surface with the carboxylate headgroup, as evidenced by the formation of multilayer adsorption and aggregation of the PFC alkyl chain at elevated levels. Molecular level support for the unique interfacial adsorption phenomenon is provided by several complementary methods: contact angle, infrared (IR) spectral shifts and intensity variations, differential scanning calorimetry (DSC), and isothermal titration calorimetry (ITC). Isotherm studies reveal the formation of monolayers of a hydrocarbon surfactant anion (OA) vs self-assembled multilayer aggregates for PFC anion species (PFOA and PFOS) at the MIMs solid−solution interface. The surface interactions are interpreted as a balance between headgroup electrostatic interactions and hydrophobic effects of the amphiphile chain at the adsorbent−solution interface.

Functionalized bio‐adsorbents for removal of perfluoroalkyl substances: A perspective

“…The copolymer sorbent system having the molar ratios between HDI and β-CD of 1:1 seemed to be preferable for the PFOA sorption over the system with higher cross-link density. This may be because the larger cross-linking density attenuates the interactions from the inclusion site in β-CD, where the inclusion sites have a better affinity to PFOA in the absence of steric effect (Karoyo & Wilson, 2013;Karoyo & Wilson, 2016). Similar results were found in the study of Xiao et al (2017), indicating that densely cross-linked polymers exhibited inferior adsorption performance.…”

Cyclodextrin-Based Polymer-Supported Bacterium for the Adsorption and in-situ Biodegradation of Phenolic Compounds

“…The immobilization of SpC bacterium cells onto the HDI-3 solid support was described in the experimental section. Also, the degree of adsorption of the bacterium cells was tested on HDI-3 films that were cast onto glass slides (Karoyo and Wilson, 2016a ) by use of optical microscopy ( cf . Figures 3A–C and Experimental Section).…”

β-Cyclodextrin Attenuates Perfluorooctanoic Acid Toxicity in the Zebrafish Embryo Model

“…Cyclodextrins (CDs) have been proposed as a remediation strategy for a variety of pollutants, including perfluorinated surfactants such as PFOA [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Structurally, CDs are cyclic sugars made up of glucose monomers.…”

“…They are inexpensive, water soluble, and non-toxic, and have been used not only in environmental remediation applications, but also as drug delivery systems for hydrophobic drugs [ 14 , 15 , 16 , 17 ]. β-Cyclodextrin (β-CD), made up of seven glucose monomers, has been shown to strongly encapsulate PFOA to form one of the strongest known CD-based host–guest complexes [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. The fully fluorinated backbone of the PFOA alkyl chain interacts with the hydrophobic β-CD cavity via van der Waals interactions, while the PFOA carboxylate group can form hydrogen bonds with hydroxyl groups lining the cavity perimeter of β-CD ( Figure 1 ).…”