Understanding interactions of pharmaceutical pollutants with cellulosic materials

This research examines the interaction mechanisms of pharmaceutical pollutants ibuprofen (IBP) and naproxen (NPR) (anti-inflammatory compounds), and 17α-ethinyl estradiol (EE2) (estrogenic compound) with cellulosic materials via adsorption studies utilizing Surface Plasmon Resonance (SPR) technique. The goal was to identify the key factors affecting the affinity between cellulose materials and pollutants in a systematic fashion with real-time adsorption monitoring to support the development of sustainable water purification technologies. The anti-inflammatory and estrogenic compounds were adsorbed on ultrathin films (thickness ~ 10-20 nm) of nanocellulose with varying surface charge (mechanically disintegrated cellulose nanofibrils (CNF) and TEMPO-oxidized cellulose nanofibers (TCNF)), and polymeric cellulose with varying degree of hydrophobicity (regenerated cellulose (RC), cellulose triacetate (CTA) and trimethylsilyl cellulose (TMSC)). Highly hygroscopic and negatively charged nanocellulose surfaces showed low affinity for drugs, while regenerated cellulose exhibited higher adsorption capacity probably due to its amphiphilic nature. Indeed, the hydrophobic character of cellulose derivatives was found to significantly impact pharmaceutical adsorption, especially in case of EE2. Hydrophobic TMSC and CTA films demonstrated adsorption for hormonal pollutant, with nearly ten-fold higher adsorption than anti-inflammatory compounds. Pharmaceuticals were detectable on hydrophobized cellulose surfaces at trace concentrations of 0.1–1 µg/mL. Langmuir adsorption model showed the highest adsorption coefficient for EE2 on TMSC, emphasizing its efficacy at capturing hormonal pollutants at low concentrations. Adsorption was mostly irreversible after rinsing, highlighting the need for specific modifications to cellulose to achieve desired selectivity and efficiency for pollutant removal. These findings aid in designing efficient membrane and sensor systems for capturing and purifying pharmaceutical-contaminated water streams.