Reduction of pore size in membranes from polyacrylonitrile by introducing 1,4-dioxane into the casting solution

The effect of adding 1,4-dioxane to casting solutions based on poly(acrylonitrile-co-methyl acrylate) (poly(AN-co-MA)) using solvents such as dimethyl sulfoxide (DMSO) and N -methylpyrrolidone (NMP) was investigated. The introduction of the soft precipitant altered the rheological properties of the studied solutions: it reduced viscosity in the poly(AN-co-MA)/NMP system and caused an opposite change in the poly(AN-co-MA)/DMSO system. A direct correlation was established between the solution viscosity and the deposition rate during membrane formation via phase inversion. The incorporation of 1,4-dioxane enabled controlled modification of the membrane morphology and filtration performance by reducing the average pore size. The reduction in the average pore size was more pronounced in the membranes with NMP than in the membranes with DMSO (up to 11.8 nm and 19.1 nm, respectively). During the filtration of crude oil and 100 g/L oil solution in toluene, the rejection of asphaltenes by the membranes of both types was over 98 %. These findings confirm the potential of 1,4-dioxane in the development of membranes with tailored properties for application in the petrochemical industry.