A review on membrane fabrication: Structure, properties and performance relationship

Highlights

• Membrane fabrication techniques

• Structure–property relationship of membranes

• Structure parameters affect the membrane performance.

Abstract

In this review, polymeric membrane fabrication techniques for pressure driven membrane processes and membrane distillation are discussed. The fabrication technique, properties of the fabricated membranes and performance in water desalination are related. Important parameters which affect the membrane performance such as crystallinity of the membrane based polymer, porous structure, hydrophobicity/hydrophilicity, membrane charge and surface roughness are analyzed. Despite the fact that extensive knowledge exist on how to ‘tailor’ membrane pore structure including its surface properties and cross-section morphology by selection of appropriate fabrication methods, there is still a challenge to produce reliable membranes with anti-fouling properties, chemical resistance, high mechanical strength with high flux and selectivity. To ensure progress in membrane performance, further improvements are needed of common membrane fabrication techniques such as phase inversion and interfacial polymerization. At the same time, the potential of novel fabrication techniques such as electrospinning and track-etching needs to be assessed. A comprehensive understanding between structure-surface properties and performance is a key for further development and progress in membrane technology for water desalination.

Introduction

According to the world population clock, the population exceeds 7 billion and will reach 10 billion by 2050. Pure drinking water would be a major problem for the developing countries in the world. The improvement in the efficiency and cost of water treatment is a major challenge to overcome the scarcity of portable water. Different membrane methods have been used for water treatment, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO) and membrane distillation (MD) [1]. UF and MF are well-developed techniques used for water treatment, whereas RO is widely used for water desalination and purification. MD is a new developing technique and it has potential for desalinating highly saline water [2], [3]. The membranes play a key role in membrane-based water treatment processes and determine the technological and economical efficiency of the aforementioned technologies; membrane improvement can greatly affect the performance of current technology. The material selection and pore size of the membranes depend on the application for which it would be used. Fig. 1 represents the average pore size requirement for membranes for different water treatment processes.

Different fabrication techniques and polymers used for the preparation of polymeric membranes are summarized in Table 1. Details of the fabrication techniques process and the material structural characteristics will be discussed in the subsequent sections.

In this article, the recent development of polymeric membrane materials and membrane preparation methods with focus on structure–property relationships for pressure-driven membrane processes and MD will be discussed. This review article will provide a reference to the researchers and manufacturers working on fabrication of membranes and materials for water treatment.