Preparation of a New Charged Nanofiltration Membrane Based on Polyelectrolyte Complex by Forced Fouling Induction for a Household Water Purifier

摘要

A new technique is introduced for the preparation of composite membranes based on the salting-out effect. The concept of this new technique consists of three parts: (i) polymer precipitation by the salting-out effect, (ii) blocking the pore structure by pressurizing the precipitated polymer particles (polyelectrolyte), and (iii) deposition of opposite charged polyelectrolyte through ionic cross-linking (polyelectrolyte complex). The pore blocked polyelectrolyte has the role of a membrane, and we called this membrane preparation technique by forced fouling induction "precipitated solute pressurization" (PSP). In this study, water-soluble polymers that are all polyelectrolytes were used as coating materials, namely polyethylenimine (PEI), poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA), and poly(vinyl sulfonic acid) (PVSA). The polymer particles formed by the addition of Mg(NO3)(2)center dot 6H(2)O were pressurized and flown to the surface of microporous polyvinyledene fluoride (PVDF) to prepare composite membranes under varying conditions of polyelectrolyte concentration, ionic strength of salt, pressure, annealing temperature, etc. The resulting membranes were characterized in terms of the flux and rejection for 100 ppm NaCl at 4 atm to determine their suitability for application in a household water purifier. A combination of PVSA and PEI polyelectrolyte complex produced by the PSP method showed the best performance of flux of 43 LMH and salt rejection rate of 83%, and this performance was maintained without loss of flux or rejection rate in a durability test carried out for 10 days.