Preparation of porous phosphine oxide-incorporated polymer membranes for selective removal of p-cresol from simulated serum: A preliminary study

This preliminary study aims to prepare porous extractant-incorporated membranes (EIMs) containing base polymer cellulose triacetate (CTA), tri-n-octylphosphine oxide (TOPO), and trioctylammonium chloride (Aliquat 336) prepared by non-solvent induced phase inversion for selective removal of p-cresol from simulated serum. The surface morphology and pore structure of the EIMs were investigated using a field emission scanning electron microscope (FE-SEM) and nitrogen sorptiometer, respectively. The functional groups and chemical composition of the EIMs were characterized by the Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectrometry (XPS), respectively. The interactions between uremic toxins (p-cresol, creatinine, and urea) and TOPO or Aliquat 336, studied independently by liquid-liquid extraction, were ascribed to hydrogen bonding. Batch tests showed that the addition of TOPO strongly favored p-cresol adsorption; for example, an adsorption capacity of 2.08 mmol/g of the EIM composed of 54.5 wt% CTA, 27.3 wt% Aliquat 336, and 18.2 wt% TOPO was obtained at 37 °C, compared to a negligibly small capacity for creatinine and urea. Cross-flow dynamic experiments revealed that the maximum adsorption of p-cresol in a multi-component serum was 0.75 mmol/g of the EIM under the conditions studied. The high adsorption selectivity for p-cresol may make the prepared EIMs promising and potential for efficient removal of p-cresol from simulated serum.