Using different surfactants for changing the properties of poly(piperazineamide) TFC nanofiltration membranes

Thin film composite (TFC) membranes are common membranes having wide applications. A common procedure for preparation of TFC membranes is interfacial polymerization process. In this study, the interfacial polymerization technique was used by applying trimesoyl chloride (TMC) and piperazine (PIP) as reagents for preparation of poly(piperazineamide) on a polyethersulphone UF support. The effect of anionic (SDS), cationic (CTAB) and non-ionic (Triton X-100) surfactants in the aqueous phase on the performance and morphology of TFC nanofiltration membranes was investigated. Characteristics and properties of obtained thin layers were measured by using ATR-IR, SEM, AFM, zeta potential measurements as well as a nanofiltration set-up. By introducing CTAB, no considerable changes in the performance and morphology were observed, but outstanding variations were highlighted in the presence of Triton X-100 and SDS. The porosity of thin layers decreased in the presence of CTAB, Triton X-100, and SDS, respectively. AFM images show a dense and compressed thin layer for thin layers containing surfactants compared to that without surfactants. The height of surface convexes decreased from 118 nm to 7 nm. On the other hand, the creation of cracks and defects in the structure of the thin layer containing SDS leads to more permeation and low rejection.