Developing high throughput thin film composite polyamide membranes for forward osmosis treatment of SAGD produced water

Abstract

Application of thin film composite (TFC) membranes for forward osmosis (FO) separation processes has attracted growing attention due to their outstanding permeation properties as compared to conventional asymmetric membranes. The aim of the present study is to fabricate high-performance TFC membranes by an innovative adjustment of interfacial polymerization (IP) reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) at the surface of a polyethersulfone (PES) microporous support. It was found that reducing the temperature of the organic solution down to −20°C effectively reduced the thickness of the PA selective layer and thus, significantly enhanced water permeation through the membranes. The water flux increased more than double from 17.6LMH for membranes prepared at 25°C to 38.5LMH at −20°C, when 3M NaCl solution and de-ionized water were used as draw and feed solutions, respectively. In addition, all the lab-made membranes showed significantly lower specific solute flux than the commercial membrane. The performance of lab-synthesized TFC membranes was also evaluated for the treatment of boiler feed water (BFW) of steam assisted gravity drainage (SAGD) process. The results showed superior permeation properties of lab-made membranes to commercially available TFC-FO membranes. This was attributed to the thinner PA selective layer and lower structural parameter (451±13) of the lab-made membranes compared to the commercial membrane (1770μm) which alleviated the effect of internal concentration polarization (ICP) remarkably. This study provides valuable guidelines for an effective tuning of the organic solution temperature during the IP reaction to develop high-throughput TFC FO membranes.