Scalable fabrication of anti-biofouling membranes through 2-aminoimidazole incorporation during polyamide casting

A proof-of-concept for the fabrication of novel anti-biofouling water purification membranes through the incorporation of a 2-aminoimidazole (2-AI) during membrane casting is presented. 2-AI molecules are known to inhibit biofouling through the disruption of biofilm formation mechanisms, not through the inactivation of bacteria. Three approaches to incorporation were evaluated, adding the 2-AI to either one of the two monomer solutions, (a) m-phenylene diamine or (b) trimesoyl chloride, that polymerize to make a polyamide active layer, or by (c) reacting the active layer with a post-polymerization-2-AI-soak solution. These methods of incorporation are directly translatable to current membrane fabrication practices without the addition of other chemicals aside from the 2-AIs themselves. Results showed that the 2-AI was incorporated into the active layer of the membranes at concentrations (0.16-0.93 M) orders of magnitude higher than what is required for biofilm inhibition (IC50 = 162-420 mu M). The 2-AI membranes significantly (p = 0.002-0.04) inhibited Pseudomonas aeruginosa biofilms (49-90% on average) due to the presence and action of 2-AI, not physico-chemical changes. The 2-AIsoak approach produced membranes that had the most stable incorporation, with no loss of compound during use and cleaning, and the highest biofilm inhibition, at 90% inhibition on average. The incorporation of 2-AI into the membranes decreased water permeability by 26-44% and salt rejection by 1.2-4.3% points, as compared to control membranes. No attempt was made to optimize 2-AI membrane preparation toward minimization of changes in water permeability and salt rejection. Given the substantial biofilm formation inhibition exhibited by the 2-AI membranes, and the limited decrease observed in water permeability and salt rejection, the 2-AI membranes presented in this study support 2-AI incorporation into polyamide active layers as a promising avenue to enhance current water purification membranes.