Reverse osmosis thin-film composite application

The membrane can be a solid, a liquid, or a gel, and the bulk phases can be liquid, gas, or vapor. Membranes can be classified according to their structures. Homogeneous or symmetric membranes each have a structure that is the same across the thickness of the membrane. These membranes can be porous or have a rather dense uniform structure. Heterogeneous or asymmetric membranes can be categorized into three basic structures (1) integrally skinned asymmetric membrane with a porous skin layer, (2) integrally skinned asymmetric membrane with a dense skin layer, and (3) thin film composite membranes [13]. Porous asymmetric membranes are made by the phase inversion process [14,15] and are applied in dialysis, ultrafiltration, and microfiltration, whereas integrally skinned asymmetric membranes with a dense skin layer are applied in reverse osmosis and gas separation applications. 

High performance thin-film composite membranes for reverse osmosis applications were fabricated by coating solutions of a highly chlorine-tolerant disulfonated PAES [92,93]. As base monomers, 4,4 -dichlorodiphenyl sulfone and 4,4 -biphenol are used. 4,4 -dichlorodiphenyl sulfone is then directly sulfonated to get a disulfonated monomer, 3,3 -disutfonate-4,4 -dichlorodiphenyl sulfone. These monomers can be directly copolymerized on a commercially available porous polysulfone support. 

Lee CH, McCloskey BD, Cook J, Lane O, Xie W, Freeman BD, et al. Disulfonated poly(arylene ether sulfone) random copolymer thin film composite membrane fabricated using a benign solvent for reverse osmosis applications. J Membr Sci 2012 389 363-71. 

IP is one of the techniques used for preparing composite membranes, normally for the production of NF and reverse osmosis (RO) membrane. Historically, thin-film composite membrane prepared by IP was developed in order to overcome the limitations and the problems encountered by an asymmetric membrane constructed by the phase inversion method (Rao et al. 1997). IP was a breakthrough in the history of membrane technology and was developed by Cadotte at the North Star Research Institute for RO applications (Pinnau and Freeman 2000). It is based on the polymerization that occurs between two reactive monomers at the interface of two immiscible solvents an aqueous phase and an organic solvent such as hexane, as shown in Figure 5.1. 

FIGURE 20.1-8 Schematic representation of thin-film composite-type films pioneered by Cadotte for reverse osmosis application. Topical monomers might include for A, mesyl chloride for B, npeiazine or 1,4 phenyidiamine. 

THIN-FILM COMPOSITE MEMBRANES FOR REVERSE OSMOSIS TABLE 1.1 Application of Reverse Osmosis Membrane Process... 

A.K. Agarwal and R.Y.M. Huang, Studies on the Enhancement of Separation Characteristics of Sulfonated Poly (Phenylene oxide)/PolysuIfone Thin Film Composite Membranes for Reverse Osmosis Applications II. Effects of Nitromethane and the Chemical Treatment Combined with Gamma-Ray Irradiation, Angewandte Makromol. Chem., 1988,163, 15-21. 

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