Synthesis of co-polyamide reverse osmosis membrane constituting a linear aliphatic triamine and m-phenylenediamine for enhanced desalination performance

The improvement in the overall efficiency of membranes (especially reverse osmosis, RO) is limited by the tradeoff between salt rejection and permeate flux. To overcome this tradeoff, an RO membrane with a co-polyamide active layer was fabricated using a mixture of an aliphatic amine Bis(3-aminopropyl)amine (BAPA) and an aromatic amine m-phenylenediamine (MPD). Interfacial polymerization (IP) was carried out by cross -linking the amine mixture with trimesoyl chloride (TMC) on a polysulfone (PSf) support leading to a co-polyamide (Co-PA) membrane. A control polyamide membrane (PA) was also fabricated from conventional monomers of MPD and TMC. The Co-PA membrane showed significantly improved filtration performance when compared to the MPD conventional membrane; the permeate flux increased by 70 % while having comparable salt rejection. Furthermore, the Co-PA membrane showed better fouling resistance toward alginate (a model polysaccharide foulant), retaining 80 % of its initial flux, which was almost completely reversible. The lesser fouling tendency of the Co-PA membrane was ascribed to its reduced surface roughness and lower negative charge compared to the control sample. Long-term stability tests with a 2000 ppm NaCl feed revealed that both membranes maintained a constant performance for 72 h of continuous operation.