Thin film polyamide membranes containing modified manganese dioxide nanotubes for removal of sodium and copper ions

Abstract

Hypothesis: Today, with the development of different industries and the disposal of untreated wastewaters, environmental pollution and pollution of water resources are increasing very rapidly. Membrane technology is an advanced and hopeful way to treat water and wastewater. Nanofiltration technology is widely used in water treatment and desalination of seawater. Methods: The performance of thin film polyamide membranes containing unmodified and modified manganese dioxide nanotubes was investigated. After hydrothermal synthesis of manganese dioxide nanotubes, the inner surface of the nanotubes was modified with polydopamine, and then, their performance in thin film polyamide membranes (in terms of monovalent/divalent ions rejection and permeation flux) was investigated. Findings: Unmodified and modified nanotubes were characterized by Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and X-ray diffraction analysis (XRD). In addition, the morphology and structure of the thin film membranes were investigated by FESEM test and the performance of the membranes was studied in terms of permeation flux, contact angle and rejection of sodium and copper ions. The maximum pure water flux, 18.6 L/m2h, was obtained for the membrane containing 0.10 %wt modified nanotube, an increase of 21.88% compared to the neat membrane. Creation of tiny pores on the surface of the membranes through hydrophilic nanotubes resulted in higher flux while there are extra routes through the nanotubes for water permeation. The maximum rejection of sodium ion (97.02%) for the membrane containing 0.2 %wt modified nanotubes could be related to the stacking of the nanotubes and more spatial hindrance, reduction in the diameter of the nanotube due to the coating and permeation of water through the nanotubes.