Influence of Mw of the polymer support on the evolution of performances relating to extraction membrane processes of Cr(VI) ions

Abstract

Currently, the use of polymers is a growth necessity in several areas, particularly, medicine, chemical, and food industries, because of their characteristics such as their low cost, light weight and excellent chemical stability. Polysulfone (PSU) is one of the technical polymer classes with high thermal, oxidative and hydrolytic stability; in addition, it is inert and resistant to chemical degradation. For all these excellent properties it is adopted as a support for the development of polymer membranes, used to treat polluted industrial discharges. In the present work, we have studied the effect of the average mass (Mw) of the PSU polymer support on the evolution of Cr(VI) ions extraction processes. Indeed, to develop our membranes, we adopted the same polysulfone polymer (PSU) with the following three average masses Mw: 35.000, 26.000 and 22.000 g/mole and the same extractive agent Ethylene diamine tetra acetic (EDTA). Elaborated membranes were characterized, using TFIR spectroscopic technique which confirms the integration of EDTA agent into the polymer matrix, whereas SEM technique made it possible to characterize the morphology and the porosity of these membranes. Obtained membranes were adopted to carry out several oriented processes relating to extraction and elimination of Cr(VI) ions, in order to study the influence of several factors (Mw polymer support average mass, C0 initial concentration of Cr(VI) ions substrate, and temperature factor) on the evolution of macroscopic (initial flux J0, permeability P) and microscopic (association constant Kass and apparent coefficient diffusion D∗) parameters, as well as the determination of activation parameters (Energy Ea, entropy ΔS?" and enthalpy ΔH?"). The analysis of all results indicates a clear influence of the size PSU polymer strings on the characteristics of synthesized membranes and the evolution of all parameters. When the Mw weight average mass of the PSU polymer decreases the membrane performance becomes better.