Photocatalytic membranes separation layer

There are two main configurations of PMRs vnth photocatalytic membranes (Fig. 21.1). In the first (Fig. 21.1a), a membrane vith a photoactive layer, which fulfills also the function of a separation layer (skin), is used. The active layer is formed on a porous non-photoactive support. In the second (Fig. 21.1b), a membrane with a non-photoactive separation layer deposited on a porous active support is applied. Depending on the membrane type, the light source is positioned either on the feed side or on the permeate side. 

Asymmetric photocatalytic membranes. (a)Type 1 photoactive separation iayer is deposited on a non-photoactive porous support (b) Type 2 non-photoactive separation layer is deposited on a photoactive porous support (adapted from Mozia, 2010). 

The theory of operation of a photocatalytic membrane with photoactive separation layer. Organic contaminants are decomposed on the membrane surface and/or within its pores.The light source is positioned on the feed side (adapted from Mozia, 2010). 

Bulk addition of nanoparticles refers to the use of nanoparticles as additives during the membrane synthesis process by phase inversion (Kim and Van der Braggen 2010). Nanoparticles are dispersed in the polymer solution, which is then cast on a support layer and contacted with a nonsolvent, in the case of diffusion- or nonsolvent-induced phase separation (DIPS or NIPS). In the eventual membrane, the nanoparticles are present in the inner structure of the membrane, and not exclusively on the membrane surface. Therefore, the functionalities of the nanoparticles that were used can only be partly exploited. For example, catalytic activities would not be efficient, as the nanoparticles that should act as catalyst are shielded by the polymer material. This is a concern particularly for photocatalytic materials such as Ti02, which are often employed for mixed matrix membranes. 

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