Design of a sodium polyacrylate/carboxymethyl-chitosan-based imprinted cryogel for fluoxetine adsorption in continuous mode.

Fluoxetine (FLX) contamination in aquatic environments poses significant ecological risks, highlighting the need for efficient and selective removal technologies. In this study, a bio-based macroporous molecularly imprinted cryogel (MIC/NaPA-CMCs) was developed for continuous-flow FLX adsorption. The cryogel was synthesized from sodium polyacrylate and carboxymethyl chitosan by cryopolymerization at -18 °C for 24 h using genipin and N,N'-methylenebis(acrylamide) as crosslinkers, with FLX as the template molecule. Template removal using an acidified solvent (5 % methanol/0.1 M HCl, 1:1 v/v) generated selective recognition cavities, while a non-imprinted cryogel (NIC/NaPA-CMCs) was prepared for comparison. The materials were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), Brunauer-Emmett-Teller (BET) analysis, and point-of-zero-charge (pHPZC) determination. MIC/NaPA-CMCs exhibited a pHPZC of 4.9 and a specific surface area of 36.8 m2/g. Fixed-bed adsorption experiments (pH 8.5, bed height 0.4 cm, 20 ± 2 °C) showed that increasing the FLX inlet concentration (10-40 mg/L) accelerated bed saturation and shifted breakthrough to shorter times, whereas increasing the flow rate (1.5-2.5 mL/min) reduced residence time, decreasing the adsorption capacity from 22.05 to 6.61 mg/g. The Thomas and Yoon-Nelson models accurately described the breakthrough curves (R2 > 0.990), indicating that adsorption performance was governed by mass-transfer limitations under dynamic conditions. Competitive adsorption with citalopram confirmed the selective recognition of FLX by MIC/NaPA-CMCs, yielding higher FLX uptake and a relative selectivity coefficient (K' > 1) than the non-imprinted cryogel. These results demonstrate the potential of the developed imprinted cryogel for selective FLX removal under continuous-flow conditions.