Synthesis and Characterization of Cellulose Acetate Membranes with Self-Indicating Properties by Changing the Membrane Surface Color for Separation of Gd(III)

This study presents a new, revolutionary, and easy method for evaluating the separation process through a membrane that is based on changing the color of the membrane surface during the separation process. For this purpose, a cellulose acetate membrane surface was modified in several steps: initially with amino propyl triethoxysilane, followed by glutaraldehyde reaction and calmagite immobilization. Calmagite was chosen for its dual role as a molecule that will complex and retain Gd(III) and also as an indicator for Gd(III). At the contact with the membrane surface, calmagite will actively complex and retain Gd(III), and it will change the color of the membrane surface during the complexation process, showing that the separation occurred. The synthesized materials were characterized by Fourier transform infrared spectroscopy (FT-IR), thermal analysis (TGA-DTA), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, demonstrating the synthesis of membrane material with self-indicating properties. In addition, in the separation of the Gd(III) process, in which a solution of gadolinium nitrate was used as a source and as a moderator in nuclear reactors, the membrane changed its color from blue to pink. The membrane performances were tested by Induced Coupled Plasma-Mass Spectrometry (ICP-MS) analyses showing a separation process efficiency of 86% relative to the initial feed solution.