The MET released into the solution was monitored by measuring the UV–VIS spectra with a BECKMAN COULTER-DU-720
spectrophotometer, as MET has a maximum absorption at 330 nm.
The membranes were characterized with Fourier transform
infrared (FTIR) spectroscopy using a NICOLET 380 (Thermo Electron
Co., USA) spectrophotometer in the attenuated total reflectance (ATR)
mode (4000–500 cm−1) with a resolution of 4 cm−1. The samples
were also characterized by X-ray powder diffraction (XRD), using a
Siemens D5005 X-ray diffractometer and a graphite crystal as
monochromator to select Cu Kα1 radiation (1.5406 Å), in a step of
0.02° s−1. The surface morphology of the NRL membrane was
observed using a scanning electron microscopy (SEM) model Zeiss®
EVO 50 (20 KV) and a take off angle of 35°.