β-Cyclodextrin functionalized polystyrene porous monoliths for separating phenol from wastewater

A β-cyclodextrin (β-CD) functionalized polystyrene porous monolith was prepared by the following procedure: First, β-CD was modified with allyl bromide leading to allyl-β-cyclodextrin (allyl-β-CD); then a concentrated emulsion was prepared using a mixture of allyl-β-CD, styrene, and divinyl benzene as the continuous phase and water as the dispersed phase. In the third step, a β-cyclodextrin (β-CD) functionalized polystyrene porous monolith was obtained by copolymerization of allyl-β-CD and styrene followed by removal of the water phase. Since the allyl-β-CD contained both hydrophilic and hydrophobic groups, it tended to move towards the water/oil interface. As a result, the internal surfaces of the porous monolith were enriched with β-CD. This enrichment was indicated by X-ray photoelectron spectroscopy characterization. The high content of β-CD and the high specific surface area of the porous monolith both contributed to a high adsorption capacity. For example, the maximum adsorption of phenol was 5.74 mg/g. Importantly, the porous monolith could be easily regenerated and recycled through desorption with ethanol and it was found that the adsorption properties remained stable for at least five adsorption/desorption cycles.