Polymeric membranes fixed-site carrier polymers

Second, other types of membrane separation processes can also be proposed for the CO2/N2 separation step, in order to play the same role as the absorption process. In that case, it is absolutely necessary to carefully estimate the operating costs (OPEX) and capital costs (CAPEX) of the operation, so that an overall CO2 capture cost (in euros or per ton of recovered CO2) can be precisely estimated. This data will obviously be of utmost importance in order to evaluate the chances of the membrane process to possibly compete with the standard capture process. A CO2/N2 separation efficiency is clearly needed in that case. Depending on the membrane material, this characteristic can be obtained based on a physical mechanism (solution-diffusion in a dense polymer, for instance, which corresponds to a classical membrane gas separation operation ), or a chemical reaction in a polymeric matrix based on fixed sites (so-called fixed site carrier membranes ) or with membranes making use of a mobile selective carrier (liquid membranes ). 

Selective separation of lead(II) and cadmium(II) chloride complexes by both liquid membranes containing liquid anion-exchangers as mobile carriers and solid polymeric membranes with anion-exchange sites as fixed carriers is described by Hayashita in Chapter 21. A novel polymeric plasticizer membrane, which is composed of cellulose triacetate polymer as a membrane support, o-nitrophenyl octyl ether as a membrane plasticizer, and trioctylmethylammonium chloride as an anion-exchange carrier, provides enhanced permeation selectivity and efficiency. 

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