The use of different materials to form the intermediate layers of tubular carbon nanofibers/carbon/alumina composite membranes for removing pharmaceuticals from aqueous solutions

The primary aim of this study was to use different materials to form the intermediate layers of tubular carbon nanofibers/carbon/alumina composite membranes (TCCACMs) for removing pharmaceuticals from aqueous solutions. To this end, plastic wrap made from four different materials (i.e., polyethylene, polymethylpentene, polyvinylchloride, and polyvinylidenechloride) were evaluated for their suitability as the precursors to form the aforementioned intermediate layers, on which carbon nanofibers (CNFs) were deposited for further fabrication of TCCACMs. Based on the results of thermogravimetric analysis and scanning electron microscopic observations, only polyvinylchloride (PVC) and polyvinylidenechloride (PVDC) films met the criteria to form the intermediate carbon layers of good quality. TCCACMs thus prepared were designated PVC-TCCACM and PVDC-TCCACM, respectively. Proposed structure of TCCACMs and relevant separation mechanisms were also revealed in this work. PVC-TCCACM and PVDC-TCCACM were then incorporated into a simultaneous electrocoagulation and electrofiltration (EC/EF) module respectively for removing three selected pharmaceuticals (i.e., caffeine, acetaminophen, and sulfamethoxazole) from aqueous solutions. The tested water specimens were artificially spiked with respective pharmaceuticals in deionized water yielding a concentration of ca. 200 μg/L. Under the optimal operating conditions PVC-TCCACM yielded the greatest removal efficiencies for caffeine (i.e., 95.8%) and sulfamethoxazole (i.e., 94.9%); whereas PVDC-TCCACM for acetaminophen (i.e., 79.8%). Evidently, couplings of the EC/EF module with suitable TCCACMs have demonstrated their capability in substantially removing pharmaceuticals from aqueous solutions. Test results showed that carbon adsorption, electrocoagulation, and electrofiltration respectively were all significant mechanisms for the removal of target pharmaceuticals. The adsorption behaviors related to CNFs on TCCACMs were also investigated in the present work.