Comparative Removal of Pharmaceutically Active Compounds Using Membrane Filtration Processes

Abstract

For the purpose of removing pharmaceutically active chemicals (PhACs) from wastewater, this study experimentally assesses the removal efficiency of four membrane filtration technologies: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) using four model pharmaceuticals, including nicotine (NCT), diclofenac sodium (DCF), 4-acetamidoantipyrine (4AAA), and ranitidine hydrochloride (RNT), spiked in a controlled synthetic wastewater matrix under identical operating conditions. Furthermore, this study investigates how steric and electrostatic interactions, along with membrane physicochemical characteristics would control the separation behavior. The influence of operating pressure is also evaluated to signify its role in controlling removal efficacy. The experimental results demonstrate limited removal efficiency for MF and UF membranes (rejection below 20% and 30%, respectively, across the tested operating pressures), particularly for low-molecular-weight PhACs, which is attributed to their relatively large transport pathways that permit dissolved solutes to penetrate with minimal retention. In contrast, NF and RO membranes achieved significantly higher rejection rates of more than 75% and more than 95%, respectively (one-way ANOVA, p < 0.05), for the tested PhACs. Generally, these results have ascertained the dominance of size, electrostatic, and charge mechanisms for NF and the effective removal of PhACs with RO due to strong solute transport inhibition through the dense barrier. Furthermore, an insignificant effect of operating pressure on the performance of MF and UF is noticed if compared to a stronger influence on NF and RO, where increased pressure initially enhances removal rate but may ultimately plateau as rejection mechanisms stabilize under polarization and fouling impacts.