Experimental and statistical investigation on fabrication and performance evaluation of structurally tailored PAN nanofiltration membranes for produced water treatment

The present study aims at investigating the effects of multiple fabrication and design parameters on the performance of nanofiltration (NF) membranes. By employing the Plackett-Burman design method, obtained results demonstrate that citric acid (0-1.5 wt.%), TiO2 (0-1 wt.%), and solvent evaporation time (1-3 min) are the top dominant factors affecting the pure water flux (PWF) of NF membranes. Also, the effects of the dominant factors and their corresponding interactions are statistically assessed through RSM technique by employing a quadratic model. Based on the ANOVA results the proposed models for the PWF and CaSO4 rejection responses are statistically significant. The calculated optimum values for citric acid, TiO2, and solvent evaporation time are 0.87 wt.%, 0.98 wt.%, and 1.34 min respectively. It is shown that by increasing the concentration of TiO2 both PWF and rejection of membrane enhanced from 108.8-131.5 (lit.m(-2).h(-1)) and from 73.5-83 % respectively. Furthermore, an increment in citric acid concentration leads to the promotion of the surface hydrophilicity and salt rejection of membranes. From the morphological point of view, increasing the TiO2 concentration leads to formation of membranes with more porous sublayers while longer solvent evaporation times results in the formation of membranes with smaller macrovoids.