Novel approach combining physico-chemical characterizations and mass transfer modelling of nanofiltration and low pressure reverse osmosis membranes for brackish water desalination intensification

Abstract

The aim of the present work is to establish a systematic approach in the range of characterization of commercial nanofiltration (NF) and low pressure reverse osmosis (LPRO) membranes materials for a better help to the users. We developed two sorts of characterizations: (i) first physico-chemicals in terms of hydrophobicity/hydrophilicity, morphology and topography and (ii) secondly by mass transfer in terms of pure water and saline solution permeabilities, monovalent (NaCl) and divalent (Na 2SO 4) solutes rejections and molecular weight cut-off determination. A model inspired by the phenomenological approach proposed by Kedem and Katchalsky (KK) and completed by Spiegler (S) will help us to quantify separately both parts of mass transfer occurring, the pure convection or advection and the pure diffusion for three membranes in polyamides, 2 NF and 1 LPRO, denoted NF270, NF90 and BW30, respectively, purchased from Dow. We have limited our study to low concentration polarization by using diluted solutions (10 −3 to 10 −1 M) and high flow rate (4 m s −1) under low conversion (5%) operational conditions to develop a new and original approach to classify and better understand the behavior of the commercialized NF and LPRO membranes under brackish waters in order to guide the users to find a suitable membrane.