A review of reverse osmosis membrane materials for desalination—Development to date and future potential

Abstract

Reverse osmosis (RO) is currently the most important desalination technology and it is experiencing significant growth. The objective of this paper is to review the historical and current development of RO membrane materials which are the key determinant of separation performance and water productivity, and to define the targets for those who are developing new RO membrane materials. The chemistry, synthesis mechanism(s) and desalination performance of various RO membranes are discussed from the point of view of membrane materials science. The review starts with the first generation of asymmetric polymeric membranes and finishes with current proposals for nano-structured membrane materials. The review provides an overview of RO performance in relation to membrane materials and methods of synthesis. To date polymeric membranes have dominated the RO desalination industry. From the late 1950s to the 1980s the research effort focussed on the search for optimum polymeric membrane materials. In subsequent decades the performance of RO membranes has been optimised via control of membrane formation reactions, and the use of poly-condensation catalysts and additives. The performance of the state-of-the-art RO membrane has been highlighted. Nevertheless, the advances in membrane permselectivity in the past decade has been relatively slow, and membrane fouling remains a severe problem. The emergence of nano-technology in membrane materials science could offer an attractive alternative to polymeric materials. Hence nano-structured membranes are discussed in this review including zeolite membranes, thin film nano-composite membranes, carbon nano-tube membranes, and biomimetic membranes. It is proposed that these novel materials represent the most likely opportunities for enhanced RO desalination performance in the future, but that a number of challenges remain with regard to their practical implementation.

Cellulose nanopapers as tight aqueous ultra-filtration membranes

“…Poly(ethylene glycol) (PEG) standards (1,4,10,20,35,50,93 kDa) were purchased from Polymer Labs (Shropshire, UK) and used to quantify the molecular weight cut-offs of the nanopapers. Four different types of nanocellulose were studied in this work, namely bacterial cellulose, wood-based nanofibrillated cellulose, TEMPO-oxidized nanocellulose and cellulose nanocrystals.…”

“…Membrane technologies, such as nanofiltration (NF) or tight ultrafiltration (UF), are key for decentralizing industrial and domestic water treatment aiming at the removal of various contaminants, which are vital for providing clean water [2,3]. Commercially available membranes used for this purpose are usually produced from polymers derived from fossil resources [4].…”

The effect of feed spacer geometry on membrane performance and concentration polarisation based on 3D CFD simulations

“…This can be expressed as: J s = J w c m (1−R s ) where J s is the solute flux, J w the water flux (or flow velocity on the membrane wall), c m the solute concentration on the membrane wall and R s the membrane rejection. Introducing the rejection term is clearly more useful than imposing a constant solute concentration on the membrane wall due to the more realistic representation of membrane [10], but it does not describe accurately mass transport through RO membranes, as this is governed by diffusion due to its small size pores (less than a nanometre) [32][33]36]. The most widely accepted transport theory for RO membrane is the solution-diffusion model [32][33], where the solute flux is related to the solute permeability and the difference in concentration between the two sides of a membrane.…”

Tip and inner walls modification of single-walled carbon nanotubes (3.5 nm diameter) and preparation of polyamide/modified CNT nanocomposite reverse osmosis membrane

“…The pressure was maintained at about 2.0 MPa and the feed solution was 2000 mg/L of NaCl solution (pH = 8) whose conductivity was about 3.0 mS/cm in this study. The temperature was controlled at 25 C. These membrane filtration conditions have been generally used in BWRO membrane systems by others [29,30]. Cross flow velocity at the membrane surface was 1 Lmin ¡1 in the filtration system.…”