Dye adsorption on zinc oxide nanoparticulates atomic-layer-deposited on polytetrafluoroethylene membranes

In this work, zinc oxide (ZnO) is deposited onto porous polytetrafluoroethylene (PTFE) membranes via atomic layer deposition (ALD) and thus produced ZnO-deposited PTFE membranes are used as adsorbents for the removal of dyes from aqueous solutions. We first examine the evolution of morphology, wettability, and crystallization of PTFE membranes with ZnO ALD. The presence of ZnO nanoparticulates significantly promotes the diffusion and contact of the aqueous solutions within the membrane on one hand, and endows the membrane a strong capability to adsorb dyes from the solutions on the other. Kinetic studies reveal that the adsorption of rhodamine B and acid orange 7 by the ZnO-deposited PTFE membranes can be described by the pseudo-second-order and pseudo-first-order model, respectively, and the adsorption of both dyes follows the Langmuir isotherm. The used membranes can be easily regenerated by rinsing with ethanol and reused for multiple times without loss of removal efficiency.