Simultaneous rejection of chromium(VI) and fluoride [Cr(VI) and F] by nanofiltration: Membranes characterizations and estimations of membrane transport parameters by CFSK model

The current work examines the performance of NF300 and PN40 nanofiltration (NF) membranes for simultaneous rejection of Cr(VI) and F. Experimental: results indicate that, Cr(VI) and F percentage of removal was improved with increasing operating pressure and declined with increasing feed concentration. Highest percent rejection of Cr(VI) and F were found 97% and 92% with NF300 and 88% and 82% with PN40 membranes for 5 ppm feed respectively. Maximum removal was found at pH 8 and above with NF300 membrane compared to PN40 membrane. Mass transfer coefficient (MTC) was found 6.88 x 10(4) cm/s and 5.74 x 10(4) cm/s and membrane transport parameters (MTPs) such as solute permeability was 4.03 x 10(5) cm/s and 6.23 x 10(5) cm/s and reflection coefficient was 0.9688 and 0.9223 using CFSK model for 5 ppm feed of Cr(VI) and F respectively for NF300 membrane. A Good correlation was found in experimental results (observed rejection for Cr(VI) and F was 0.97 and 0.92) and the model predicts results (true rejection for Cr(VI) and F was 0.9731 and 0.9222) for 5 ppm feed of Cr(VI) and F respectively for NF300 membrane. (C) 2016 Elsevier Ltd. All rights reserved.