Integrating nanoclay intercalated with interlayers of cationic surfactant into thin-film nanocomposite nanofiltration membranes to improve performance and antifouling property

We fabricated thin-film nanocomposite (TFN) polyamide membrane for the treatment of brine solutions. Different surfactant-modified nanoclay (montmorillonite, MMT) were embedded separately into polyamide layer through interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). These cationic surfactants are: trimethyloctylammonium bromide (OTAB), hexadecyltrimethlammonium bromide (CTAB); and dimethyldioctadecylammonium bromide (DDAB). The cationic surfactants have different chemical structure, which can alter the d-spacing of the nanoclay. The surfactants can also facilitate the dispersion of the nanoclay in TMC/n-hexane solution. Among the surfactants, DDAB has the longest alkane chain on its chemical structure, thus adjusting the d-spacing of the nanoclay at most. TFNDDAB-MMT had the most uniformly dispersed nanoclays on the membrane surface compared to other membranes. The pure water flux of the membranes at 6 bar follows a decreasing order: TFNDDAB-MMT (66.02 +/- 5.65 L m(-2) h(-1)) > TFNOTAB-MMT (43.74 +/- 3.88 L m(-2) h(-1)) approximate to TFNNa-MMT (45.03 +/- 2.80 L m(-2) h(-1)) > TFNCTAB-MMT (41.69 +/- 3.00 L m(-2) h(-1)) approximate to TFC (40.93 +/- 2.72 L m(-2) h(-1)). Furthermore, it also enhanced the membrane antifouling property with a good stability in wide range of operating condition.

Automated summary

We fabricated thin-film nanocomposite (TFN) polyamide membrane for the treatment of brine solutions. Different surfactant-modified nanoclay (montmorillonite, MMT) were embedded separately into polyamide layer through interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). The results showed that DDAB surfactant had the most significant effect on membrane performance, resulting in the most uniformly dispersed nanoclays on the membrane surface, as well as higher pure water flux and fouling resistance.