The pore surface diffusion model as a tool for rapid screening of novel nanomaterial-enhanced hybrid ion-exchange media

Abstract

The primary goal of this study was to examine the feasibility of using Pore Surface Diffusion Model (PSDM) as a rapid screening tool to predict breakthrough curves of short bed columns packed with nanomaterial enhanced hybrid-ion exchange media. A novel hybrid-ion exchange media was fabricated by synthesizing titanium dioxide nanostructured endoskeleton inside nitrate selective strong base ion-exchange resin. The properties of the hybrid media were characterized and batch reactor tests were conducted with arsenate (As) and nitrogen-nitrate (NO₃⁻N) as model contaminants in 5 mM NaHCO₃ buffer ultrapure water at final pH = 7.2 ± 0.3 to assess the contaminant removal capacity and develop sorption isotherms. Freudlich sorption isotherm (q = KC_e^1/n) model was used to provide inputs for the PSDM predictions of the contaminants' breakthrough curves. To validate the PSDM breakthrough curve predictions for both model contaminants, continuous short bed packed column tests were conducted under the modeled conditions. Hybrid media regeneration was also conducted with solution mix of 2% KOH and 1% KCl followed by rinse with 0.1% HCl, and the column was operated under same conditions to assess the regeneration efficiency of the media. The results demonstrated that 100% regeneration efficiency could be achieved for nitrate, while only 75% efficiency could be achieved for arsenate under these regeneration conditions. The PSDM was able to successfully predict the breakthrough curves for arsenic and nitrate with relatively high precision, characterized by R² ≈ 0.977 and R² ≈ 0.930 for arsenate and nitrate, respectively.